Cancer, 1993 Feb 1, 71(3), 667 - 71 MDR1 gene expression and its clinical relevance in primary gastric carcinomas; Wallner J et al.; BACKGROUND . Drug resistance remains a major problem in gastric carcinomas . To evaluate the mechanisms involved in this resistance, the authors determined the expression of the MDR1 gene, a multidrug resistance gene, in primary gastric carcinomas . METHODS . MDR1 RNA levels of gastric carcinoma specimens (n = 22) were determined by slot blot analysis . An MDR1 cDNA (probe 5A) was used for the hybridization . RESULTS . MDR1 RNA was detected in 41% of the gastric carcinomas, with high levels in 18% of the specimens . No expression of the MDR3 gene was observed in these tumors . MDR1 gene expression was independent of patient age, tumor localization, and lymph node involvement . However, MDR1 RNA expression was less frequent in locally advanced tumors and was absent in the primary tumors of all six patients who had distant metastases . CONCLUSIONS . The data indicate that multidrug-resistant cells are present in primary gastric carcinomas and suggest that multidrug resistance might contribute to the clinical drug resistance of these tumors. Br J Cancer, 1993 Feb, 67(2), 274 - 8 Chemotherapeutic efficacy of the protein-doxorubicin conjugates on multidrug resistant rat hepatoma cell line in vitro; Ohkawa K et al.; In vitro studies were initiated to study the antitumour effect of protein-doxorubicin (DXR) conjugate on the growth of the multidrug resistant rat ascites hepatoma cell line, AH66DR . The 50% inhibitory concentration (IC50) for DXR in AH66DR cell line was 16 mumol l-1 (AH66 parental cell line, AH66P, IC50 was 0.08 mumol l-1) . Treatment of AH66P and AH66DR cells with various concentrations of DXR or conjugates at equivalent concentrations of DXR was performed . The two types of conjugates used were bovine serum albumin (BSA)-DXR conjugate and immunoglobulin G (IgG)-DXR conjugate . Both of these conjugates showed potent dose-dependent inhibition of cell growth against AH66DR cells as compared with the cells treated with DXR or other controls . The IC50 for BSA-DXR and IgG-DXR conjugates in AH66DR cell line was 0.05 (equivalent DXR) mumol l-1 and 0.07 (equivalent DXR) mumol l-1, respectively . These values were similar to that of the AH66P treated with DXR . Cellular uptake and accumulation of DXR or BSA-DXR conjugate was also quantitated in both cell lines . The cellular concentration of DXR in AH66DR cells was 2-fold lower than that of AH66P cells throughout the experiment . In contrast, by the treatment of AH66DR cells with BSA-DXR conjugate, the intracellular drug concentration increased as a function of time up to 24 h (639.1 +/- 41.8, equivalent DXR, ng 10(-5) cells) and reached the same drug level as AH66P cells treated with DXR (617.9 +/- 17.3 ng-5 cells) . Ammonium chloride treatment inhibited the effects of the conjugates but did not inhibit the free drugs . Intracellular DXR was effluxed rapidly from AH66DR cells, but BSA-DXR conjugate remained in the cells at relatively high concentration for a long time . These results indicate that by chemically modifying DXR, such as by conjugation of the drug with proteins, it may be possible to overcome multidrug resistance. Gynecol Oncol, 1993 Feb, 48(2), 214 - 20 Sensitivity of drug-resistant human ovarian tumor cell lines to combined effects of tumor necrosis factor (TNF-alpha) and doxorubicin: failure of the combination to modulate the MDR phenotype; Safrit JT et al.; We have examined four human ovarian tumor lines (A2780, AD10, OVC-8, and SKOV-3) selected for their sensitivity and/or resistance to the recombinant human tumor necrosis factor alpha (TNF-alpha) and the chemotherapeutic drug doxorubicin (DOXO) . The tumor lines were either sensitive to both agents, resistant to one or the other, or resistant to both . Of the four lines examined only the DOXO-resistant line AD10 exhibited the multidrug-resistance (MDR) phenotype . Enhanced cytotoxicity was seen with the combination of TNF-alpha and DOXO in each line regardless of their sensitivity or resistance patterns and, thus, demonstrates that drug resistance due to the expression of the MDR phenotype or its absence can be overcome by TNF-alpha and DOXO . We then examined whether TNF-alpha or TNF-alpha and DOXO modulated the MDR phenotype in AD10 as a possible mechanism of overcoming drug resistance . TNF-alpha had no effect on either DOXO intake or efflux as measured by flow cytometry . Further, TNF-alpha treatment showed no effect on the level of MDR-1 mRNA . These results suggest that the enhanced cytotoxicity seen with the combination of TNF-alpha and DOXO is not the result of any modulation of drug influx or efflux levels by TNF-alpha . Overall, these findings suggest that combination treatment with TNF-alpha and DOXO can overcome resistance inflicted by different mechanisms. J Nat Prod, 1993 Feb, 56(2), 233 - 9 1H- and 13C-nmr assignments of phyllanthin and hypophyllanthin: lignans that enhance cytotoxic responses with cultured multidrug-resistant cells; Somanabandhu A et al.; Complete 1H-nmr data and unambiguous assignments of the 13C-nmr spectra of phyllanthin {1} and hypophyllanthin {2} were obtained through extensive nmr studies, including homonuclear COSY, homonuclear decoupling, APT, HETCOR, nOe difference, selective INEPT, and COLOC experiments . The absolute configuration of hypophyllanthin {2} was determined by cd . Neither of these lignans demonstrated significant cytotoxic activity when evaluated with a battery of cultured mammalian cells, but both were found to enhance the cytotoxic response mediated by vinblastine with multidrug-resistant KB cells . In addition, 1 was found to displace the binding of vinblastine with membrane vesicles derived from this cell line, suggesting an interaction with the P-glycoprotein. Invest New Drugs, 1993 Feb, 11(1), 75 - 9 Phase II trial of doxorubicin and trifluoperazine in metastatic breast cancer; Budd GT et al.; Pre-clinical and clinical studies have shown that trifluoperazine (TFP) can modulate multidrug resistance . We have performed a Phase II trial of TFP and doxorubicin in doxorubicin-naive patients with metastatic breast cancer . We hypothesized that TFP would inhibit the development of doxorubicin resistance, resulting in an increased rate of complete response or a prolongation in response duration . Twenty patients with metastatic breast cancer were treated every 3 weeks with TFP 5 mg by mouth every 6 hours on days 0-5 and doxorubicin 60 mg/m2/96 hr on days 1-4 by continuous intravenous infusion . The first 5 patients were treated with TFP 15 mg by mouth every 6 hours, but the dose was reduced to 5 mg every 6 hours when grade 3-4 extrapyramidal toxicity was noted in 3 of the first 5 patients . Thereafter, neurologic toxicity was grade 0-2 . No complete and 9 partial responses were produced in 20 patients (45%) . The median response duration was 17 weeks (range 7-112) . The combination of trifluoperazine and doxorubicin did not seem to produce a response rate or duration markedly different than that expected for doxorubicin alone in patients with metastatic breast cancer . Alternative trial designs may be necessary in future clinical trials investigating the inhibition of acquisition of drug resistance. Leuk Lymphoma, 1993 Feb, 9(3), 255 - 64 A comparative analysis of the sensitivity of multidrug resistant (MDR) and non-MDR cells to different anthracycline derivatives; Michieli M et al.; Because of the fact that tumor cell sensitivity to cytotoxic agents may play a major role in cancer treatment, and several anthracyclines are widely used for first-line treatment of leukemia, lymphoma and other tumors, and since the overexpression of the mdr-1 gene-coded 170 Kd glycoprotein (P170) decreases cell sensitivity to anthracyclines, we investigated the relationship between P170 overexpression and the cytotoxicity of two classic anthracyclines (Daunorubicin or DNR and Doxorubicin or DX) and two lipophilic anthracycline derivatives (Idarubicin or IDA and Iododoxorubicin or IDX) . For these purposes, we used multidrug resistant (MDR) and non-MDR tumor and leukemia cell lines and the MTT-microcultured tetrazolium colorimetric assay . We showed that mdr-1 gene overexpression was strongly associated with the development of a high level of resistance to DNR and DX, but not to the derivatives IDA and IDX . These data suggest that more lipophilic anthracycline derivatives may also be active in MDR cell systems. Semin Cell Biol, 1993 Feb, 4(1), 63 - 76 P-glycoproteins: mediators of multidrug resistance; Germann UA et al.; Multidrug resistance represents a major obstacle to successful chemotherapy of metastatic disease . Elevated levels in cancer cells of the product of the multidrug resistance gene, P-glycoprotein or the multidrug transporter, have been associated with the development of simultaneous resistance to a great variety of amphiphilic cytotoxic drugs . P-glycoprotein is an integral plasma membrane protein which contains 12 putative transmembrane regions and two ATP binding sites . It confers multidrug resistance by functioning as an energy-dependent drug efflux pump . Here we describe recent studies on the biosynthesis, structure, function, and mechanism of action of P-glycoprotein which have provided insights into the complexity of this multifunctional transport system and revealed an additional chloride channel activity . The physiological role of P-glycoprotein, however, still remains to be elucidated. Br J Cancer, 1993 Feb, 67(2), 311 - 20 Differential cytotoxicity of 19 anticancer agents in wild type and etoposide resistant small cell lung cancer cell lines; Jensen PB et al.; A panel of six 'wild type' and three VP-16 resistant small cell lung cancer (SCLC) cell lines is used to evaluate to what extent in vitro sensitivity testing using a clonogenic assay can contribute to combine cytotoxic drugs to regimens with improved efficacy against SCLC . The resistant lines include (a) H69/DAU4, which is classical multidrug resistant (MDR) with a P-glycoprotein efflux pump (b) NYH/VM, which exhibits an altered topoisomerase II (topo II) activity and (c) H69/VP, which is cross-resistant to vincristine, exhibits a reduced drug accumulation as H69/DAU4 but is without P-glycoprotein . 19 anticancer agents were compared in the panel . The MDR lines demonstrated, as expected, cross-resistance to all topo II drugs, but also different patterns of collateral sensitivity to BCNU, cisplatin, ara-C, hydroxyurea, and to the topo I inhibitor camptothecin . The complete panel of nine cell lines clearly demonstrated diverse sensitivity patterns to drugs with different modes of action . Correlation analysis showed high correlation coefficients (CC) among drug analogues (e.g . VP-16/VM-26 0.99, vincristine/vindesine 0.89), and between drugs with similar mechanisms of action (e.g . BCNU/Cisplatin 0.89, VP-16/Doxorubicin 0.92), whereas different drug classes demonstrated low or even negative CC (e.g . BCNU/VP-16 -0.21) . When the CC of the 19 drug patterns to VP-16 were plotted against the CC to BCNU, clustering was observed between drugs acting on microtubules, on topo II, alkylating agents, and antimetabolites . In this plot, camptothecin and ara-C patterns were promising by virtue of their lack of cross-resistance to alkylating agents and topo II drugs . Thus, the differential cytotoxicity patterns on this panel of cells can (1) give information about drug mechanism of action, (2) enable the selection and combination of non-cross-resistant drugs, and (3) show where new drugs 'fit in' among established agents. Br J Cancer, 1993 Feb, 67(2), 284 - 9 Cortisol is transported by the multidrug resistance gene product P-glycoprotein; van Kalken CK et al.; The physiology of the multidrug transporter P-glycoprotein (Pgp) is still poorly understood . We now show evidence that cell lines with a high expression of Pgp display a reduced accumulation of cortisol and an ATP-dependent outward transport of the hormone . Cortisol efflux from Pgp negative cells does not have such an active component . Further we show that the steroid hormones cortisol, testosterone, and progesterone cause an immediate, dose-dependent increase of daunorubicin accumulation in Pgp overexpressing cells . These effects are particularly apparent for the more lipophilic steroids . These results demonstrate that Pgp may function as a transporter for cortisol and suggest a physiological role of the protein in steroid handling by organs such as the adrenal. Br J Cancer, 1993 Feb, 67(2), 226 - 31 Effect of anthracycline analogs on photolabelling of p-glycoprotein by {125I}iodomycin and {3H}azidopine: relation to lipophilicity and inhibition of daunorubicin transport in multidrug resistant cells; Friche E et al.; Eight anthracycline analogs that have been shown to modulate multidrug resistance (Friche et al., Biochem . Pharmacol., 39, 1721-1726; 1990) were tested for their inhibitory effect on the photolabelling of P-glycoprotein . We photoaffinity labelled P-glycoprotein in daunorubicin (DNR) resistant Ehrlich ascites tumour cells (EHR2/DNR +) with a {125I}iodinated Bolton-Hunter derivative of daunorubicin ({125I}iodomycin) and with {3H}azidopine . The photolabelling of P-glycoprotein by {125I}iodomycin was inhibited more than 50% by 10 microM (1000-fold molar excess) of DNR (52%), N,N-dibenzyl-DNR (52%), and N-benzyladriamycin-14-valerate (AD-198) (85%) . Vincristine at 10 microM inhibited {125I}iodomycin labelling of P-glycoprotein by 95% . Thus vincristine was more potent than any of the eight anthracyclines tested, despite its relatively low lipophilicity . Increasing the concentration of DNR, AD-198 and N,N-dibenzyl-DNR to 40 microM resulted in 90, 99.5 and 99.5% inhibition of P-glycoprotein labelling by {125I}iodomycin, respectively . In comparison with the other anthracycline analogs, N,N-dibenzyl-DNR and Ad-198 were also found to exert the greatest inhibition of {3H}azidopine labelling of P-glycoprotein (about 90% at 100-fold molar excess) . The solvents Cremophor EL and Tween 80 (30 micrograms ml-1; 0.003% v/v), which are modulators of multidrug resistance in EHR2/DNR + cells, also inhibited {125I}iodomycin labelling > 90% . We showed earlier that there is a correlation between the lipid solubility within the anthracycline group of MDR-associated drugs and their ability to enhance DNR accumulation in EHR2/DNR + cells but a corresponding correlation to lipophilicity when it comes to the inhibitory effect on the specific photolabelling of Pgp ligand binding sites could not be demonstrated . Neither could a correlation between the modulating effect of the analogs on DNR accumulation and inhibition on the labelling of Pgp be demonstrated . With increasing lipophilicity of the analogs it seems that the chemical structure plays a lesser role, and the degree of lipophilicity becomes a more important feature. Leuk Res, 1993 Feb, 17(2), 149 - 56 Expression of P-glycoprotein and anionic glutathione S-transferase genes in non-Hodgkin's lymphoma; Rodriguez C et al.; Non-Hodgkin's lymphomas (NHL) are usually sensitive to chemotherapy . A certain percentage of patients are primarily or subsequently resistant to chemotherapeutic agents . Several biological mechanisms are implicated in this phenomenon, including multidrug resistance (mdr1) and glutathione S-transferase (GST pi) . We investigated these two systems, using dot blot analysis, in 41 patients who presented NHL with advanced disease . There were 15 patients with low grade, 22 with intermediate grade, and 4 patients with high grade using the Working Formulation for Clinical Usage . Twenty-five patients had not been previously treated and 16 had been treated, including 13 with refractory disease . Eleven out of 25 (44%) patients overexpressed mdr1 mRNA at diagnosis as compared to 6/16 (38%) in relapse, corresponding to 6/13 (46%) refractory patients . Nine out of 25 (36%) patients overexpressed GST pi mRNA at the time of diagnosis, and 6/16 (50%) in relapse . These data indicate that overexpression of these two messengers is not acquired after treatment in NHL . Furthermore, there is no relationship between the stage or histological grade and the overexpression of these two markers . This study shows that mdr1 and GST pi gene expressions are independent of one another . With regard to the clinical response, our results also demonstrated a higher level of treatment failure in the group co-expressing the two transcripts, 6/8 (75%) patients died in progressive disease as compared to 9/15 (60%) patients without overexpression, and 2/8 (25%) vs 6/15 (40%) responded to treatment . On the other hand, overexpression of only one of the two mRNAs did not allow us to observe a difference in the clinical response . Since it seems that coexpression of the mechanisms of resistance present a better clinical impact, it would be of interest to analyse simultaneously different mechanisms involved in the resistance phenomenon in NHL. Cancer, 1993 Feb 1, 71(3 Suppl), 1098 - 109 Cytotoxic chemotherapy for advanced hormone-resistant prostate cancer; Yagoda A et al.; BACKGROUND . Advanced adenocarcinoma of the prostate after hormonal manipulation has been noted to be a relatively chemotherapeutic nonresponsive tumor . Earlier reviews have reported objective responses, that is, complete and partial remissions in 6.5% of 3184 patients, and the current review examines the efficacy of new agents . METHODS . The current review consists of 26 new drug trials culled from papers and abstracts published between 1987-1991 . RESULTS . Results of these 26 drug trials found a similar trend, 8.7% (95% confidence interval, 6.4-9.0%), indicating that hormone-resistant adenocarcinoma of the prostate still fails to respond to most cytotoxic agents . The most interesting of the new therapeutic agents is the combination of vinblastine plus estramustine . Only six agents had an objective response rate greater than 10%, such as vinblastine by continuous infusion, trimetrexate, mitoguazone, and estramustine . The recent introduction of radioactive-labeled monoclonal antibodies is intriguing and these will undoubtably be used as carriers for radiotherapeutic and cytotoxic compounds . CONCLUSIONS . Although multidrug resistance may explain the marginal efficacy of cytotoxic drugs, methods to overcome such resistance and, more importantly, new classes of agents must be developed . In addition, reliable disease markers must be found for osseous and visceral metastases to avoid the prevailing confusion in evaluating more precisely the destruction of prostate cancer cells. MMWR Morb Mortal Wkly Rep, 1993 Jan 29, 42(3), 48 - 51 Probable transmission of multidrug-resistant tuberculosis in a correctional facility--California; Terfenadine (Seldane): a new drug for restoring sensitivity to multidrug resistant cancer cells; Department of Medicine, Yale University School of Medicine and Comprehensive Cancer Center, New Haven, CT 06510In our efforts to identify clinically effective drugs for reversing multidrug resistance (MDR) mediated by P-glycoprotein, we tested terfenadine for anti-MDR activity because it appeared to sensitize a patient to doxorubicin and because it met structural requirements defined for this activity . Terfenadine sensitized MCF-7/ADR human breast cancer cells and L1210/VMDRC.06 murine leukemia cells to doxorubicin . At concentrations < or = 10 microM, terfenadine decreased the IC50 to doxorubicin by up to 25-fold against MCF-7/ADR cells and completely restored sensitivity to L1210/VMDRC.06 cells . The drug had no effect on the sensitive, parental cell lines and enhanced activity of other drugs affected by the MDR phenotype . Terfenadine was as potent as trans-flupenthixol, one of the most active modulators of MDR . The mechanism of action of terfenadine appeared to be due to inhibition of the function of P-glycoprotein since it augmented the accumulation of doxorubicin and inhibited the efflux of rhodamine 123 from MDR lines but had no effect on drug accumulation or efflux in sensitive cells . Terfenadine displaced azidopine from P-glycoprotein, but at concentrations higher than expected based on its overall potency . Since terfenadine is clinically available, has numerous structural derivatives available for study, and has a relatively low toxicity profile, this drug and drugs of its class should be evaluated for future clinical trials. J Biol Chem, 1993 Jan 25, 268(3), 1792 - 8 Topology of P-glycoprotein as determined by epitope mapping of MRK-16 monoclonal antibody; Georges E et al.; There is growing evidence for the direct role of P-glycoprotein mediating multidrug resistance in tumor cells . P-glycoprotein is thought to function as an energy-dependent drug efflux pump . The monoclonal antibody MRK-16 binds to an external domain of P-glycoprotein and partially inhibits drug efflux in multidrug-resistant cells . As an approach toward elucidating the mechanism by which MRK-16 affects drug transport, we undertook the definition of the precise binding site of this antibody . In this study we have mapped the epitope of MRK-16 monoclonal antibody to a resolution of a single amino acid using a series of overlapping synthetic peptides . We demonstrate that MRK-16 recognizes only the class I isoform (MDR1) of human P-glycoprotein and that its epitope encompasses at least two (first and fourth) of the six predicted extracellular peptide loops . These results suggest that the epitope of MRK-16 is discontinuous and that the sequences involved which are separated by about 625 amino acids in the linear sequence must be spatially situated in close proximity in the native protein . Based on these results, we present a model for transmembrane alpha-helical packing of P-glycoprotein in the lipid bilayer . This may have implications for understanding the function of P-glycoprotein in drug transport. Int J Cancer, 1993 Jan 21, 53(2), 323 - 7 Multidrug-resistant human KB carcinoma cells are highly resistant to the protein phosphatase inhibitors okadaic acid and calyculin A . Analysis of potential mechanisms involved in toxin resistance; Chambers TC et al.; In this study we show that multidrug-resistant (MDR) human KB-V1 cells are highly resistant to the cytotoxicity of okadaic acid and calyculin A, 2 toxins from marine sponges that are potent inhibitors of type-1 and type-2A protein phosphatases (PP1 and PP2A) . Cytotoxicity and colony-forming assays indicated that, relative to parental drug-sensitive KB-3 cells, KB-V1 cells are 35-fold more resistant to okadaic acid and 70-fold more resistant to calyculin A . Cytotoxicity of the toxins was associated with mitotic arrest characterized by chromosome scattering and over-condensation, with KB-3 cells being more sensitive than KB-V1 cells and calyculin A being more potent than okadaic acid . The resistance of KB-V1 cells to both okadaic acid and calyculin A was completely reversed by verapamil, suggesting that the toxins may be transported by P-glycoprotein (P-gp) . To further assess the possibility of an interaction with P-gp, the toxins were employed as potential modulators of the photoaffinity labeling of P-gp by {3H}azidopine . Relative to vinblastine, which effectively competed with {3H}azidopine for P-gp photolabeling, calyculin A was 100-fold less potent and okadaic acid did not inhibit photolabeling at concentrations up to 50 microM . To determine whether the resistance mechanism involved differences in toxin-sensitive phosphatase activity, the activity was assayed in extracts from both cell lines and found to be slightly higher (1.6-fold) in KB-V1 than in KB-3 cells . Our results demonstrate a novel, marked resistance of MDR KB-V1 cells to these phosphatase inhibitors and suggest that a major mechanism of resistance may involve toxin transport by P-gp at sites apparently different from those which bind azidopine. Cancer Lett, 1993 Jan 15, 68(1), 7 - 14 Staurosporine reduces P-glycoprotein expression and modulates multidrug resistance; Sampson KE et al.; We have investigated the effect of staurosporine and other kinase inhibitors on the mRNA and protein levels of the P-glycoprotein (P-gp) in multidrug resistant (MDR) cells . Treatment of human MDR KB-V1 cells with staurosporine for 24 h caused up to a 50% decrease in the amount of P-gp mRNA and protein present . Co-treatment of KB-V1 cells with verapamil, a known reversal agent, plus staurosporine, H-9, or K252a resulted in an enhanced sensitization of cells to vinblastine than with verapamil alone . These findings support a role for protein kinases in the control of multidrug resistance through effects on P-gp levels. Blood, 1993 Jan 15, 81(2), 490 - 5 P-glycoprotein expression in human plasma cell myeloma: correlation with prior chemotherapy; Grogan TM et al.; Multidrug-resistant (MDR) myeloma patients failing chemotherapy may express P-glycoprotein (PGP), which serves as an efflux pump protecting the neoplastic cells . Unknown is whether PGP expression might relate to prior cytotoxic drug exposure . To address this question, we studied 106 consecutive bone marrow samples from 104 myeloma patients with samples studied either before or after therapy and at the time of relapse . We performed an established immunocytochemical assay of PGP using an MDR-1-specific monoclonal antibody and correlated PGP status with prior chemotherapy dosage . Myeloma patients with no prior therapy had a low incidence of PGP expression (6%, 3/47), whereas those receiving chemotherapy had a significantly higher incidence (43%, 21/49) (P < .0001) . A substantially higher incidence of PGP expression (50%, 83%, respectively) occurred when the total vincristine dose exceeded 20 mg and when doxorubicin exceeded 340 mg . In the 11 patients who received both high vincristine and doxorubicin dosages (> 20 mg, > 340 mg total dose) there was 100% incidence of PGP expression in the tumor cells . These data provided the basis for a predictive mathematical model from which dose-related PGP expression normograms were generated . Time with myeloma for PGP-negative patients (mean 33 months) had overlapping confidence limits with PGP-positive patients (mean 42 months), suggesting that disease duration was not a significant variable . PGP expression did not correlate with other clinical factors or immunophenotypic factors . Our findings indicate a strong correlation between PGP expression in myeloma and past chemotherapy in myeloma, in particular, related to prior exposure to the natural product agents vincristine and doxorubicin . Additionally, the proportion of PGP-positive plasma cells was significantly higher in the doxorubicin-treated patients than the nondoxorubicin-treated patients (87.7% v 65.17%; P = .013) . Combined high vincristine and doxorubicin total dosage appear highly predictive of PGP expression. Biochem Biophys Res Commun, 1993 Jan 15, 190(1), 79 - 85 Resistance to tetracycline, a hydrophilic antibiotic, is mediated by P-glycoprotein in human multidrug-resistant cells; Kavallaris M et al.; Two multidrug-resistant human leukemic CCRF-CEM sublines (CEM/VCR R and CEM/VLB100) were significantly more resistant to tetracycline, a hydrophilic antibiotic, than parental cells (P < 0.001) . Verapamil and cyclosporin A completely reversed tetracycline resistance in CEM/VCR R cells, which also accumulated and retained significantly less {3H}tetracycline than CCRF-CEM cells . Like verapamil, addition of tetracycline to CEM/VCR R cells which had achieved steady-state vincristine levels resulted in augmented vincristine accumulation . {3H}Azidopine photoaffinity labelling of CEM/VCR R membrane proteins was inhibited by tetracycline in a dose-dependent manner . Although drugs associated with the multidrug-resistance phenotype are typically hydrophobic compounds, these data suggest that resistance to tetracycline, despite its hydrophilic nature, is mediated by P-glycoprotein in these cell lines. Cancer Res, 1993 Jan 15, 53(2), 310 - 7 Monoclonal antibody to an external epitope of the human mdr1 P-glycoprotein; Arceci RJ et al.; A membrane glycoprotein, termed P-glycoprotein, has been shown to be responsible for cross-resistance to a broad range of structurally and functionally distinct cytotoxic agents . P-glycoprotein, encoded in humans by the mdr1 gene, functions as an energy-dependent efflux pump to exclude these cytotoxic agents from the resistant cell . In order to study the phenomenon of multidrug resistance in both normal and neoplastic cells, we have generated a mouse monoclonal antibody directed to an external epitope of the human P-glycoprotein . This monoclonal antibody, 4E3, is an IgG2a class antibody which specifically recognizes the human mdr1 P-glycoprotein but not the mdr3 gene product . The 4E3 monoclonal antibody immunoprecipitates both the glycosylated and nonglycosylated forms of P-glycoprotein under mild denaturation conditions . In addition, 4E3 can detect P-glycoprotein in immunocytochemical analysis of fixed tissue-cultured cells and in analysis of frozen sections of human tissue . Binding of the monoclonal antibody to multidrug-resistant cells does not significantly affect the intracellular accumulation or potentiate the cytotoxicity of daunomycin in multidrug-resistant cells . However, at high concentrations of antibody, 4E3 produces a mild potentiation of vinblastine and actinomycin cytotoxicity in multidrug-resistant cells . This monoclonal antibody will be useful both for analyzing P-glycoprotein expression in normal and neoplastic cells and for isolating live cells expressing the P-glycoprotein without significantly affecting the efflux functions of the transporter. J Biol Chem, 1993 Jan 5, 268(1), 658 - 64 Selective regulation of expression of protein kinase C (PKC) isoenzymes in multidrug-resistant MCF-7 cells . Functional significance of enhanced expression of PKC alpha; Blobe GC et al.; The multidrug resistance (MDR) phenotype induces cross-resistance to many chemotherapeutic agents in cancer cells . Protein kinase C (PKC) has been implicated in the regulation of the MDR phenotype . In order to determine the role of specific PKC isoenzymes in regulating the MDR phenotype, the expression and activity of PKC isoenzymes in the human breast cancer cell line, MCF-7-WT, and an MDR subline, MCF-7-MDR, were examined . The MDR phenotype was associated with a 10-fold increase in calcium-dependent PKC activity as well as a 10-fold decrease in calcium-independent activity was due to a selective increase in the activity was due to a selective increase in the expression of PKC alpha as determined by Western blot analysis and hydroxylapatite chromatography . This increase in expression of PKC alpha was regulated at the message level as demonstrated by Northern blot analysis . The decrease in calcium-independent activity was caused by a decrease in the expression of PCK delta and epsilon . The significance of the increase in PKC alpha expression was then demonstrated by a commensurate 11-fold increase in the basal and stimulated phosphorylation of the myristolated alanine-rich C kinase substrate . Phosphorylation of P-glycoprotein, the cellular mediator of the MDR phenotype, was increased > 20-fold in the unstimulated MCF-7-MDR cell line and its phosphorylation was further increased 2-fold in response to phorbol 12-myristate 13-acetate . These changes paralleled the increases in P-glycoprotein pump function and the MDR phenotype underscoring the role for PKC alpha in regulating P-glycoprotein phosphorylation and function. Eur J Cancer, 1993, 29A(8), 1152 - 7 Selective reversal of vinblastine resistance in multidrug-resistant cell lines by tamoxifen, toremifene and their metabolites; Kirk J et al.; In this study we describe the effects of tamoxifen, toremifene and their 4-hydroxy and N-desmethyl metabolites on the toxicity of a range of drugs to human breast and lung cancer and to Chinese hamster ovary cell lines, determined using a tetrazolium-based semi-automated colorimetric assay . Vinblastine resistance was completely abolished in an mdr1-transfected lung cancer cell line (S1/1.1), indicating that P-glycoprotein-mediated multidrug resistance can be fully reversed by anti-oestrogens . A substantial (14- to 39-fold) enhancement of vinblastine toxicity to highly multidrug-resistant (MCF-7Adr) cells expressing P-glycoprotein was also observed in the presence of tamoxifen, toremifene and their metabolites, while m-amsacrine, cisplatin and melphalan toxicity was unaffected. In Vivo, 1993 Jan-Feb, 7(1), 73 - 9 In vivo characterization of immunogenicity of a mitoxantrone-resistant murine P388 leukemia; Fichtner I et al.; The Mitoxantrone-resistant murine leukemia P388/Mitox, expressing the multidrug-resistant phenotype, has a higher immunogenicity than the parent sensitive P388 . This could be shown in vivo by immunization with lethally-irradiated tumor cells . If the P388/Mitox was used for immunization before subsequent challenge with viable tumor cells of the same line, this resulted in a partial rejection of tumors and production of a substantial number of tumor-free survivors . For an effective immunization at least two primings s.c., i.v . or i.p . with at least 10(6) irradiated cells were necessary . This protected the recipient mice from a challenge of up to 10(8) viable cells over a period of at least 75 days . Treatment of BDF1 mice with the T-cell suppressor Cyclosporin A prevents immunization . In nude mice no immunization effect could be obtained . It was possible to transfer immunity adoptively with spleen cells from mice, which were treated with irradiated tumor cells of the P388/Mitox line . Treatment of tumor-bearing mice with IL-2 resulted in a prolongation of survival both when it was administered prophylactically before transplantation of P388/Mitox and at an advanced stage (day 7-11) . Also the alkyl-phosphocholine hexadecylphosphocholine was significantly effective in the resistant but not in the parent P388 leukemia . The data presented demonstrate that by development of a multidrug-resistance, concomitantly a xenogenization must have taken place which leads to a recognition of cells by immune mechanisms . In our model, T-lymphocytes and NK-/LAK-cells probably play a role in the immunologically conditioned rejection of tumor cells of the P388/Mitox leukemia.(ABSTRACT TRUNCATED AT 250 WORDS) Cancer Chemother Pharmacol, 1993, 32(3), 173 - 8 Antitumor activity and cytotoxicity of a new ankinomycin derivative, 3'-,11-dibutyryl ankinomycin; Ishii S et al.; Ankinomycin is a new antitumor antibiotic found in the culture broth of Streptomyces sp . SF2587 . Ankinomycin showed marked cytotoxicity and antitumor activity against some murine leukemias, but the activity against murine solid tumors was rather weak because of its strong acute toxicity . We synthesized ankinomycin acyl derivatives and examined their antitumor activity . Among the derivatives, 3',11-dibutyryl ankinomycin (AN1006) exhibited the highest antitumor activity . The antitumor activity of AN1006 was dependent on the administration schedule, and on the most effective schedule, AN1006 showed activity comparable with that of Adriamycin (ADM) against murine solid tumors and leukemias . AN1006 showed a cytotoxic spectrum different from that of ADM, exhibiting cytotoxicity stronger than that of ADM against colon carcinoma, stomach carcinoma, and some leukemia cell lines . According to these in vitro effects, AN1006 showed antitumor activity superior to and equal to that of ADM against human colon xenografts and stomach carcinoma xenografts in athymic nude mice, respectively . AN1006 was effective against multidrug-resistant tumors in vitro and in vivo . AN1006 is an interesting candidate for further evaluation. Eur J Cancer, 1993, 29A(7), 1000 - 2 Titanocendichloride activity in cisplatin and doxorubicin-resistant human ovarian carcinoma cell lines; Harstrick A et al.; The activity of a new organometallic compound, titanocendichloride, was evaluated in doxorubicin- and cisplatin-resistant human ovarian carcinoma cell lines in vitro . Titanocendichloride showed no cross resistance to doxorubicin in two multidrug resistant sublines of A2780 . Furthermore, the cell line A2780 CP3, which is about 20-fold resistant to cisplatin was only 2.5-fold resistant to titanocendichloride, indicating a lack of cross resistance between the two metal compounds . These results were confirmed in vivo where titanocendichloride showed a much stronger inhibitory effect in cisplatin-resistant human ovarian carcinoma xenografts than cisplatin. Int J Hematol, 1993 Jan, 57(1), 31 - 7 MDR1 (multidrug resistance) gene expression in adult acute leukemia: correlations with blast phenotype; Miyachi H et al.; Resistance to multiple chemotherapeutic agents is related to the production of P-glycoprotein, a transmembrane drug efflux pump that is encoded by the multidrug resistance gene (MDR1) . To detect low-level or heterogenous expression of the MDR1 gene in acute leukemia, we have developed sensitive, specific and semi-quantitative protocols for measuring levels of MDR1 mRNA, based on the polymerase chain reaction . Using this assay, we screened blasts from 20 patients with untreated adult acute leukemia for evidence of MDR1 gene expression . The level of MDR1 mRNA was normalized to beta 2-microglobulin mRNA and was defined by reference to the highly resistant trimetrexate-selected leukemia cells MOLT-3/TMQ200 (1.80) . MDR1 mRNA was observed in 14 out of 20 patients . Higher MDR1 mRNAs were observed in three patients with phenotypes of undifferentiated or minimally differentiated nonlymphocytic acute leukemia, as compared with other types of acute leukemia (0.98 vs . 0.25) . In contrast, lower MDR1 mRNAs were found in five patients with acute promyelocytic leukemia, as compared with other types of acute leukemia (0.08 vs . 0.45) . These findings suggest that MDR1 gene expression is correlated with the leucocyte differentiation stage of leukemia . MDR1 gene expression may, in part, explain the responsiveness to chemotherapy in these distinct subtypes of acute leukemia. Anticancer Res, 1993 Jan-Feb, 13(1), 249 - 55 An analysis of vincristine-resistance in BHK cells pretreated with 1-beta-D-arabinofuranosylcytosine; Chen Y et al.; As with SV40-transformed BHK cells (1), pretreatment of BHK cells with 1-beta-D-arabinofuranosylcytosine (araC) very markedly enhanced the resistance frequency to N-phosphonoacetyl-L-aspartate (PALA) but only modestly increased the resistance frequency to vincristine (VCR) . AraC pretreatment of cells that already had moderate VCR-resistance again only modestly enhanced the resistance frequency at a higher VCR concentration . By contrast, delaying the addition of VCR to BHK cells by 7-24 hours after pretreatment with araC increased the enhancement of VCR-resistance frequency to a level comparable to the enhancement of PALA-resistance frequency . VCR-resistant clones isolated without or after araC pretreatment were analysed for amplification of the multidrug resistance (mdr) gene . One of four clones isolated by single-step selection with no araC pretreatment and four of six clones isolated after araC pretreatment showed amplification of the mdr gene . All VCR-resistant clones tested were cross-resistant to actinomycin D and VCR-resistance was inhibited by treatment with verapamil. Int Rev Neurobiol, 1993, 35, 279 - 390 Acetylcholine transport, storage, and release; Parsons SM et al.; ACh is released from cholinergic nerve terminals under both resting and stimulated conditions . Stimulated release is mediated by exocytosis of synaptic vesicle contents . The structure and function of cholinergic vesicles are becoming known . The concentration of ACh in vesicles is about 100-fold greater than the concentration in the cytoplasm . The AChT exhibits the lowest binding specificity among known ACh-binding proteins . It is driven by efflux of protons pumped into the vesicle by the V-type ATPase . A potent pharmacology of the AChT based on the allosteric VR has been developed . It has promise for clinical applications that include in vivo evaluation of the density of cholinergic innervation in organs based on PET and SPECT . The microscopic kinetics model that has been developed and the very low transport specificity of the vesicular AChT-VR suggest that the transporter has a channel-like or multidrug resistance protein-like structure . The AChT-VR has been shown to be tightly associated with proteoglycan, which is an unexpected macromolecular relationship . Vesamicol and its analogs block evoked release of ACh from cholinergic nerve terminals after a lag period that depends on the rate of release . Recycling quanta of ACh that are sensitive to vesamicol have been identified electrophysiologically, and they constitute a functional correlate of the biochemically identified VP2 synaptic vesicles . The concept of transmitter mobilization, including the observation that the most recently synthesized ACh is the first to be released, has been greatly clarified because of the availability of vesamicol . Differences among different cholinergic nerve terminal types in the sensitivity to vesamicol, the relative amounts of readily and less releasable ACh, and other aspects of the intracellular metabolism of ACh probably are more apparent than real . They easily could arise from differences in the relative rates of competing or sequential steps in the complicated intraterminal metabolism of ACh rather than from fundamental differences among the terminals . Nonquantal release of ACh from motor nerve terminals arises at least in part from the movement of cytoplasmic ACh through the AChT located in the cytoplasmic membrane, and it is blocked by vesamicol . Possibly, the proteoglycan component of the AChT-VR produces long-term residence of the macromolecular complex in the cytoplasmic membrane through interaction with the synaptic matrix . The preponderance of evidence suggests that a significant fraction of what previously, heretofore, had been considered to be nonquantal release from the motor neuron actually is quantal release from the neuron at sites not detected electrophysiologically.(ABSTRACT TRUNCATED AT 400 WORDS) Cancer Chemother Pharmacol, 1993, 32(1), 25 - 30 Reversal of multidrug resistance in Friend leukemia cells by dexniguldipine-HCl; Reymann A et al.; Dexniguldipine-HCl (DNIG)--a prospective clinical modulator of p170-glycoprotein (pgp170)-mediated multidrug resistance (MDR)--was evaluated in a drug-accumulation assay in MDR murine leukemia cell strain F4-6RADR expressing pgp170 . The compound elevated low accumulation of either doxorubicin (DOX), daunorubicin (DNR), or mitoxantrone (MITO) in resistant F4-6RADR cells to the very levels observed in drug-sensitive F4-6 precursor cells . In parallel with the increase in DNR content (F4-6RADR, solvent: 303 +/- 27 pmol/mg protein; DNIG (3.3 mumol/l): 1,067 +/- 174 pmol/mg protein; F4-6P, solvent: 948 +/- 110 pmol/mg protein; n = 8-9, SEM), the amount of DNR tightly bound to the acid precipitate pellet obtained from F4-6RADR (i.e., protein, DNA, RNA) increased 3.9-times to the levels observed in sensitive F4-6 cells . The main pyridine metabolite of DNIG displayed similar activity . Concentration-response analysis revealed that DNIG and R,S-verapamil (VER) induced 100% reversal of the DNR accumulation shortage associated with the MDR phenotype but DNIG was 8 times more potent than VER (50% inhibitory concentration (IC50), 0.73 vs 5.4 mumol/l) . In keeping with the accumulation assay, DNIG was about 10 times more potent than VER in sensitizing F4-6RADR cells to the cytostatic and cytotoxic effects of DNR in proliferation assays . In conclusion, DNIG is a potent in vitro modulator, improving (a) the accumulation of anthracycline-like cytostatics, (b) drug access to cellular binding sites, and (c) the cytostatic action of DNR in F4-6RADR leukemia cells of the MDR phenotype. Eur J Cancer, 1993, 29A(4), 559 - 61 Effect of D,L-verapamil, verapamil enantiomers and verapamil metabolites on the binding of vincristine to alpha 1-acid glycoprotein; Woodcock BG et al.; Vincristine binding to solutions of alpha 1-acid glycoprotein (AGP, 2 mg/ml) and the effect of D,L-verapamil, verapamil enantiomers and the verapamil metabolites norverapamil and D617 were investigated in vitro using equilibrium dialysis and 3H-labelled vincristine . Vincristine binding to AGP (52.3 +/- 3.6%) was concentration independent over the range 0.002-2.0 micrograms/ml . The displacement of vincristine from AGP varied between 25.1 and 81.3% with D,L-verapamil and verapamil enantiomers added at concentrations in the range 5-50 micrograms/ml . In contrast, the displacement by D617 (5-100 micrograms/ml) was weaker and varied between 0 and 47% . The displacement at 20 micrograms/ml produced by D,L-verapamil, R-verapamil, S-verapamil and norverapamil was 53.1%, 56.8%, 58.9% and 53.9%, respectively, was more than double that for D617 (25%; P = 0.002) . It is concluded that vincristine, D,L-verapamil and verapamil isomers and metabolites interact at binding sites on AGP . These interactions may be clinically important in multidrug resistance, for example in cancer patients with elevated levels of AGP undergoing treatment with verapamil and vinca alkaloids. Cancer Chemother Pharmacol, 1993, 31(5), 412 - 4 Targeting chemosensitizing doses of toremifene based on protein binding; Wurz GT et al.; Toremifene is currently being evaluated as a chemosensitizing agent in doxorubicin-resistant patients . Although concentrations of > 2 microM reverse resistance in vitro, target concentrations required to reverse multidrug resistance (MDR) in vivo may be highly influenced by variables such as protein binding in serum . We examined the effects of high serum concentrations on the cellular accumulation of toremifene in an MDR MDA-MB-A-1 human breast-cancer cell line . We then examined the cellular accumulation of doxorubicin at various toremifene concentrations in 5% - 100% serum . We also measured the concentrations of toremifene and its major metabolites in plasma specimens obtained from two patients receiving 360 mg/day for 5 days in a phase I study . Our results show that (1) high serum concentrations decrease toremifene accumulation, (2) toremifene concentrations of < or = 2.5 microM enhance doxorubicin accumulation, and (3) patients achieve plasma toremifene concentrations of 10-15 microM following doses of 360 mg/day x 5 days . Our findings suggest that in vivo toremifene concentrations well above those used to reverse resistance in vitro are required to overcome the effect of high serum-protein binding. Cancer Chemother Pharmacol, 1993, 31(5), 369 - 75 Effects of verapamil on the pharmacokinetics and metabolism of epirubicin; Mross K et al.; Experimental data suggest that multidrug resistance in cancer may be overcome by using an increased dose of anticancer agent(s) in combination with a resistance-modifying agent (RMA) . We studied the pharmacokinetics and metabolism of both epirubicin (EPI) and verapamil (VPL) to explore the possible pharmacokinetic interactions between these two drugs . Ten patients with advanced breast cancer were given EPI (40 mg/m2 in a daily i.v . bolus for 3 consecutive days), and five of them also received VPL (4 x 120 mg/daily p.o . for 4 consecutive days) . The data indicated a significant interaction between these two drugs that affected their metabolism . The areas under the concentration-time curves (AUC) obtained for epirubicin glucuronide, epirubicinol glucuronide, and both of the 7-deoxy-aglycones were higher in the EPI + VPL group as compared with the EPI group . The AUC, terminal half-life, mean residence time, volume of distribution at steady state, and plasma clearance of EPI alone as compared with EPI + VPL did not differ significantly . These results suggest either an induction of enzymes necessary for drug metabolism or an increase in the liver blood flow, resulting in an enhanced generation of metabolites with time or in an inhibition of excretion processes . Comparisons of the AUC values obtained for EPI and its metabolites after the first, second, and third injections of EPI revealed a cumulative effect for the metabolites that was more pronounced in the EPI + VPL group, being significant (P < 0.05) for epirubicin glucuronide in both treatment groups and for epirubicinol glucuronide in the EPI + VPL group . Maximal concentrations of VPL and nor-VPL reached 705 +/- 473 and 308 +/- 122 ng/ml, respectively, with the steady-state concentrations being 265 +/- 42 ng/ml for VPL and 180 +/- 12 ng/ml for nor-VPL. Cancer Chemother Pharmacol, 1993, 31(5), 343 - 9 Modulation of drug cytotoxicity in wild-type and multidrug-resistant tumor cells by stereoisomeric series of C-20'-vinblastine congeners that lack antimicrotubule activity; Borman LS et al.; Seven binary vinca alkaloid congeners were newly synthesized as the C14' or C16'(20') or C14'16'(20') stereoisomers of C20'-modified VBL . These congeners lacked detectable antimicrotubule activity in assays of polymerization of purified microtubule protein and of mitotic arrest induction . The compounds modulated the cytotoxicity of VBL, VCR, and DOX in sarcoma and colon-tumor cell lines . In wild-type cell lines, each congener elicited a concentration-dependent enhancement of cytotoxicity that was drug- and cell-type-selective . For example, C20'-deoxy C14'16'20'-epi VBL sensitized sarcoma S180 cells 19-fold to DOX and 11-fold to VCR but had no effect on VBL cytotoxicity . In the rat colon-cancer cell lines there was preferential enhancement of VCR cytotoxicity by most congeners . In two MDR cell strains of S180, the modulation potency of each congener was independent of specific drug or of resistance level . As a result, the amount of modulator (concentration) required for reversal was proportional to the drug-resistance level . Such properties were not displayed by the monomeric vinca alkaloid modulator vindoline . The potency of drug modulation in both wild-type and MDR cells strains was dependent on the stereoisomeric form of the congener and its C20'-substituents. Cell Growth Differ, 1993 Jan, 4(1), 41 - 7 Regulation by bcl-2, c-myc, and p53 of susceptibility to induction of apoptosis by heat shock and cancer chemotherapy compounds in differentiation-competent and -defective myeloid leukemic cells; Lotem J et al.; Myeloid leukemias that differ in their competence for induction of differentiation were analyzed for expression of bcl-2 and c-myc and for their sensitivity to induction of apoptosis by heat shock and cancer chemotherapy compounds . The M1 leukemia expressed a high level of bcl-2 and showed a much lower susceptibility to induction of apoptosis by heat shock, Adriamycin, 1-beta-D-arabinofuranosylcytosine, methotrexate, and cycloheximide, compared to five other leukemias which expressed a low level of bcl-2 . There was no association between susceptibility to induction of apoptosis and competence for induction of differentiation . The difference in susceptibility to methotrexate, which is not regulated by the multidrug resistance (MDR) genes, and treatment with verapamil, which blocks MDR activity, have indicated that the higher resistance of the M1 leukemia to these agents was not due to MDR activity . The results indicate that the level of regulated bcl-2 expression in these myeloid leukemias was associated with cell susceptibility to induction of apoptosis by different apoptosis-inducing agents . Screening for expression of bcl-2 may thus be useful to characterize leukemias regarding susceptibility to induction of apoptosis by different agents . The level of regulated c-myc expressed in these leukemias was not associated with susceptibility to induction of apoptosis . Transfection with a deregulated mutant p53 into the M1 leukemia did not change susceptibility to apoptosis induction, but transfection with deregulated c-myc increased susceptibility to apoptosis.(ABSTRACT TRUNCATED AT 250 WORDS) Cell Growth Differ, 1993 Jan, 4(1), 31 - 40 Extracellular matrix regulation of multidrug resistance in primary monolayer cultures of adult rat hepatocytes; Schuetz JD et al.; Previous studies reported that, in the absence of drug exposure, multidrug resistance, including resistance to Adriamycin (ADR), could develop in primary rat hepatocyte cultures (B . Carr, Proc . Am . Assoc . Cancer Res., 29:1158, 1988) . However, the hepatocytes in that report were cultured on plastic without the benefit of an extracellular matrix (ECM) . Because the ECM regulates hepatic gene expression, we have critically evaluated in primary cultures of rat hepatocytes how the ECM affects hepatic ADR resistance, the level of the drug efflux transporter associated with MDR, P-glycoprotein (pgp), and transport of a prototypical pgp substrate, vincristine . Hepatocytes cultured on type I collagen (Vitrogen) had greater resistance to ADR toxicity accompanied by parallel increases in the level of pgp mRNA, decreased drug accumulation, and enhanced drug efflux when compared with the hepatocytes maintained on the basement membrane matrix Matrigel . The development of ADR resistance coincided with the time course of increased pgp mRNA but was not coincident with the time course of expression of either the placental isozyme of glutathione S-transferase or P-450 reductase, proteins associated with MDR in some resistance models . Southern blot analysis revealed neither gross changes in pgp gene structure or gene copy number to account for the increase in pgp RNA levels for hepatocytes cultured on Vitrogen . ECM also regulated xenobiotic-inducible expression of hepatic pgp, since chemotherapeutic agents, including vincristine and colchicine, induced pgp mRNA exclusively in hepatocytes cultured on Vitrogen . The critical matrix proteins in Matrigel responsible for regulation of pgp were determined by the selective addition of its components to the culture environment . The presentation of the individual matrix elements as a rigid substratum to the hepatocyte did not decrease pgp mRNA . In contrast, the presentation to the same hepatocytes of either laminin or type IV collagen in a nonrigid state (solubly in the medium) selectively decreased hepatocellular pgp mRNA . We conclude that primary rat hepatocytes develop ADR resistance with time in culture due to increased expression of pgp and that ECM proteins represent endogenous physiological modulators of both basal and chemotherapeutically inducible expression of hepatic P-glycoprotein. Mol Pharmacol, 1993 Jan, 43(1), 51 - 6 Estradiol induction of rhodamine 123 efflux and the multidrug resistance pump in rat pituitary tumor cells; Jancis EM et al.; Rhodamine 123 is a fluorescent dye that localizes in mitochondria, is a substrate for the multidrug resistance pump, and is retained for long periods of time by carcinoma cells . 17 beta-Estradiol causes GH4C1 cells (rat pituitary tumor cells) to lose rhodamine 123 fluorescence faster than untreated cells . We found that estradiol induces accumulation of the mRNA for the multidrug resistance pump 3-5-fold, with maximum induction occurring within 1 day at 10(-9) M estradiol . Immunoblot analysis demonstrated that estradiol induces a protein of 150 kDa that reacts with an antibody to P-glycoprotein, the multidrug resistance pump . The reduced retention of rhodamine 123 caused by estradiol is prevented by verapamil and cyclosporin, inhibitors of the pump . A clone resistant to the effects of estradiol on rhodamine 123 has greatly reduced levels of mRNA for the pump . The effect of estradiol is more marked on rhodamine 123 retention than it is on that of rhodamine 110 or tetramethylrhodamine methyl ester . We conclude that estradiol enhances rhodamine 123 efflux by inducing the multidrug resistance gene . The specificity for rhodamine 123, compared with other analogs, may be caused by differences in accessibility to the pump. Cancer Chemother Pharmacol, 1993, 31(4), 301 - 7 Decreased resistance to N,N-dimethylated anthracyclines in multidrug-resistant Friend erythroleukemia cells; Schaefer A et al.; Doxorubicin-resistant Friend erythroleukemia cells, line F4-6 ADM2R, were selected by exposure of wild-type F4-6 cells to doxorubicin concentrations of up to 1 microgram/ml . In these cells, increased expression of multidrug resistance (MDR) genes was demonstrated by Northern blot analysis . The growth-inhibitory effect of doxorubicin, daunorubicin, N,N-dimethyldoxorubicin, N,N-dimethyldaunorubicin, morpholinodoxorubicin, and pyrromycin was comparatively investigated in resistant and wild-type cells . The doxorubicin-resistant F4-6 cells showed approx . 200-fold resistance to doxorubicin and about 100-fold resistance to daunorubicin with respect to the drug-sensitive counterpart . A dramatic decrease in resistance was observed for the N,N-dimethylated derivatives of doxorubicin and daunorubicin as well as for the N,N-dimethylated natural anthracycline pyrromycin and for morpholinodoxorubicin . Uptake studies using {14C}-daunorubicin and {14C}-N,N-dimethyldaunorubicin in resistant F4-6 cells showed a decreased accumulation of daunorubicin but no significant reduction in N,N-dimethyldaunorubicin accumulation as compared with the wild-type cells . Treatment with verapamil led to increased intracellular levels of daunorubicin in resistant cells, whereas an excess of N,N-dimethyldaunorubicin did not have this effect . Thus, the decreased resistance of the doxorubicin-resistant F4-6 cells to the N-alkylated anthracyclines may at least in part be due to a reduced affinity of these compounds for the efflux pump . The results indicate that the dimethylation of the amino group of the anthracycline sugar moiety and its incorporation within a morpholinyl ring may overcome MDR by similar mechanisms. Eur J Cancer, 1993, 29A(2), 245 - 7 In vitro effect of suramin on lung tumour cells; Morocz IA et al.; In the search for new therapeutic concepts in lung cancer chemotherapy, suramin, a potential anticancer drug which evades multidrug resistance, was tested in vitro on 25 lung-derived cell lines, either non-tumorigenic cells, or established cell lines from five different tumour types . Suramin treatment resulted in a time- and dose-dependent decrease in {3H}thymidine incorporation, except in one adenocarcinoma cell line where DNA synthesis was highly stimulated . {3H}Leucine incorporation was less affected, indicating that suramin acted cytostatically rather than cytotoxically . Our results show that suramin affected DNA synthesis of the different types of lung derived cells, including non-tumorigenic and tumour cell lines, to a similar extent. Adv Cancer Res, 1993, 60, 157 - 80 Function and regulation of the human multidrug resistance gene; Chin KV et al.; The discovery of an energy-dependent pump system for natural product anticancer drugs has important implications for the biology of related energy-dependent transport systems as well as for the treatment of human cancer . To fully realize the therapeutic potential associated with manipulation of the multidrug transporter, it will be necessary to understand the mechanisms of action of the transporter and its mode of regulation . This review has summarized recent developments in these areas which suggest that both the activity of the pump and its genetic regulation are potential targets for new anticancer therapies. J Urol, 1993 Jan, 149(1), 174 - 8 Pseudomonas exotoxin conjugated to monoclonal antibody MRK16 specifically kills multidrug resistant cells in cultured renal carcinomas and in MDR-transgenic mice; Mickisch GH et al.; Using renal carcinoma and prostate carcinoma cell lines, we investigated the concept of targeting and killing multidrug resistant cells in urogenital cancers . Renal carcinoma lines HTB44, 45, 46, and 47 expressed a relatively low, but detectable level of multidrug resistance (MDR)1 mRNA as indicated by Northern blot analysis, whereas prostate lines LNCaP and DU145 were found to be MDR1-negative . Anti-P-glycoprotein monoclonal antibody MRK16 was conjugated to Pseudomonas exotoxin (PE) by a stable thioether bond . Treatment with MRK16-PE resulted in a dose-dependent killing of multidrug resistant renal carcinoma cells, while non-MDR expressing prostate carcinoma cells were not affected . Addition of excess MRK16 blocked the effect of MRK16-PE . Furthermore, MOPC-PE, a non-MDR associated monoclonal antibody control conjugate, did not target and kill multidrug resistant renal carcinoma cells . Having established that MRK16-PE was active against and specific for multidrug resistant cells in culture, we also tested bioactivity in MDR-transgenic mice, whose bone marrow cells express the human MDR1 gene at a level approximately equal to that found in many human cancers . Again, MRK16-PE killed multidrug resistant bone marrow cells with high efficiency in an intact animal, and killing was blocked by unconjugated MRK16. Indian Pediatr, 1993 Jan, 30(1), 47 - 50 Clinical profile and outcome in enteric fever; Sharma A et al.; Sixty five blood culture positive cases of S . typhi were studied for clinical profile . A total of 64.6% were multidrug resistant and 35.4% were chloramphenicol sensitive . In patients with multidrug resistant S . typhi the age was higher (p < 0.01), and incidence of complications such as shock (35.7%), encephalopathy (42.9%), myocarditis (14.3%) and gastric hemorrhage (4.7%) were more frequent, compared to chloramphenicol sensitive group . Cases with multidrug resistant S . typhi (MDRST) were treated with oral ciprofloxacin; the period of defervescence of fever was significantly less (p < 0.05) compared to the chloramphenicol group . Our study suggests the use of ciprofloxacin in the treatment of MDRST without any side effects. Cancer Detect Prev, 1993, 17(3), 425 - 32 Doxorubicin, vincristine, and actinomycin-D, but not teniposide, require long-lasting uninterrupted verapamil pressure to overcome drug resistance in multidrug-resistant cells; Toffoli G et al.; The cytotoxic efficacy of doxorubicin (DOX), vincristine (VCR), actinomycin-D (ACT-D), and teniposide (VM-26) toward the LoVo and SW948 multidrug-resistant (MDR) cell sublines was significantly enhanced by the concomitant presence of verapamil (VER) during pharmacological treatment (1-h exposure) without, however, achieving a complete reversion of the MDR phenotype . Long-lasting VER in the culture medium, at the end of the combined drug+VER treatment, conferred to DOX, VCR, and ACT-D cytotoxic efficacy roughly similar to that exerted on the drug-sensitive parent cell lines . On the contrary, no enhancement of VM-26 cytotoxic efficacy was derived from continuous VER treatment . Enhancement of DOX, VCR, and ACT-D cytotoxic efficacy requires that VER be present in an uninterrupted manner in the culture medium since brief interruptions (15 to 60 min) in the VER pressure completely counteract any effect . These findings offer new insight into the modalities of pharmacological treatment that MDR cells require to obtain a complete reversion of cellular resistance to the various drug families included in the MDR spectrum. Breast Cancer Res Treat, 1993, 26(1), 23 - 39 Differential expression of steroid receptors, hsp27, and pS2 in a series of drug resistant human breast tumor cell lines derived following exposure to antitumor drugs or to fractionated X-irradiation; Whelan RD et al.; This study examined whether levels of estrogen receptor (ER), progesterone receptor (PR), and expression of estrogen regulated pS2 and/or heat shock protein (hsp) 27 were associated with drug resistance in a series of MCF-7 sublines expressing modest (i.e . 3- to 14-fold), yet clinically relevant, levels of resistance to vincristine (VCR) . These sublines were variously derived following pulsed exposures to VCR, to fractionated X-irradiation, or to alternating drug and X-ray treatments . This selection procedure more closely reflects the clinical treatment of breast tumors than the use of continuous drug exposures . The drug-selected sublines exhibited the classical multidrug resistance phenotype (MDR) characterized by cross-resistance to vinblastine (VLB), etoposide (VP-16), and Adriamycin (ADR), overexpression of P-glycoprotein (Pgp), impaired accumulation of {3H}-VCR and of Rhodamine-123 (Rh 123), and altered activities of certain drug detoxification enzymes . This classic MDR phenotype was associated with a lack of mitogenic response to estrogen or antiestrogen, related to loss of detectable ER and PR; consistent with these data, neither pS2 nor hsp27 expression was detectable . In contrast, X-ray-pretreated VCR-resistant cells (MCF/DXR-10) cells exhibited a distinctive resistance phenotype proving cross-resistant to VLB and VP-16 but not to ADR, and Pgp overexpression was not detectable . Furthermore, these VCR-resistant DXR-10 cells retained parental levels of ER and PR, exhibited sensitivity to estrogen and 4-hydroxytamoxifen, and expressed detectable levels of pS2 and hsp27 . Comparable characteristics to these MCF-7/DXR-10 cells were also identified in a similarly-derived X-ray-pretreated VCR-resistant subline of the ZR-75-1 human breast tumor cell line . These data therefore indicate that functional ER are frequently, but not invariably, modified in tumor cells which express resistance to multiple drugs. Eur J Cancer, 1993, 29A(3), 408 - 15 Chemosensitisation and drug accumulation effects of cyclosporin A, PSC-833 and verapamil in human MDR large cell lung cancer cells expressing a 190k membrane protein distinct from P-glycoprotein; Barrand MA et al.; The doxorubicin-selected multidrug resistant (MDR) human large cell lung cancer line COR-L23/R, lacks P-glycoprotein but shows a drug accumulation deficit . It does however overexpress a 190k membrane protein which shares an epitope with, but is otherwise distinct from, P-glycoprotein . The resistant cells show only a small sensitisation to vincristine and daunorubicin on treatment with cyclosporin A and its more potent analogue, PSC-833 despite an increase in drug accumulation . Verapamil, another effective resistance modifier in P-glycoprotein MDR cells, is slightly more effective . Fluorescent daunorubicin distributes in the cytoplasm and nucleus of sensitive parent COR-L23 cells but is confined to cytoplasmic perinuclear vesicles in resistant cells . Addition of cyclosporin A or PSC-833 slightly increases cytoplasmic fluorescence whereas verapamil also increases nuclear fluorescence . Resistance in this non-P-glycoprotein MDR line, COR-L23/R where these resistance modifiers have little effect may be associated with expression of the 190k protein. Eur J Cancer, 1993, 29A(12), 1776 - 8 Increased chemosensitivity to doxorubicin of intrinsically multidrug-resistant human colon carcinoma cells by prolonged exposure to verapamil; Toffoli G et al.; Resistance modifying agents (RMA) such as verapamil (VER) have proved effective in reversing multidrug resistance (MDR) in many in vitro experimental models, but clinical results with RMA have been disappointing . To clarify this apparent discrepancy we have evaluated the cytotoxic effects of doxorubicin (DOX) plus VER in four human colon carcinoma (HCOC) cell lines (LoVo, DLD-1, SW948, SW1116) . These lines were selected on the basis of their levels of mdr1 mRNA being similar to those expressed by HCC obtained from non-drug-treated patients . In all cell lines the sensitising effect of VER on DOX cytotoxicity was schedule-dependent and maximal potentiation of DOX cytotoxicity was obtained by exposure to VER for a time > or = the cells' population doubling time. Eur J Cancer, 1993, 29A(10), 1377 - 83 Reversal of multidrug resistance by a new lipophilic cationic molecule, S9788 . Comparison with 11 other MDR-modulating agents in a model of doxorubicin-resistant rat glioblastoma cells; Huet S et al.; We have compared the properties of the novel multidrug resistance modulator, S9788, to a panel of 11 well-known modulators in a model of rat glioblastoma cells resistant to doxorubicin and displaying a P-glycoprotein-mediated multidrug-resistance phenotype complemented by a mechanism of intracellular drug tolerance not yet identified (Br J Cancer 1992, 65, 538-544) . S9788, like most modulators, was able to completely restore drug accumulation in the resistant line to the level obtained in the sensitive cells . This was obtained with 10 mumol/l of modulator, which is slightly higher than required for cyclosporine A (3 mumol/l) verapamil and nicardipine (6 mumol/l), but lower than for amiodarone, trifluoperazine and dipyridamole (20 mumol/l), tamoxifen and diltiazem (40 mumol/l), quinine, quinidine and nifedipine (> 100 mumol/l) . Complete restoration of drug cytotoxicity was, however, obtained only with amiodarone, and a residual resistance factor of 4 could not be overcome by cyclosporine A or S9788, while other modulators gave residual resistance factors of 5-20 (trifluoperazine, tamoxifen, verapamil, quinine, nicardipine, dipyridamole) or even higher (diltiazem, quinidine, nifedipine) . When studying doxorubicin accumulation obtained for an exposure to the IC50 of this drug, it appeared that some modulators were able to decrease this "intracellular IC50" independently of their efficiency in resistance reversal (cyclosporine A, S9788, amiodarone, trifluoperazine, quinine, tamoxifen), thus reversing intracellular drug tolerance, whereas other modulators could not reduce this parameter (verapamil, nicardipine, dipyridamole, diltiazem, quinidine) . It is suggested that drugs of the first group could be able to segregate doxorubicin in subcellular compartments from which it could not reach its nuclear targets. Eur J Cancer, 1993, 29A(5), 753 - 9 A study of the expression of four chemoresistance-related genes in human primary and metastatic brain tumours; Mousseau M et al.; We investigated four mechanisms of intrinsic chemoresistance in a series of 67 human brain tumours including 31 gliomas (one grade I ganglioglioma, nine grade II and 10 grade III astrocytomas, 11 glioblastomas), 13 cerebral metastases, one medulloblastoma, one malignant teratoma, three ependymomas and 18 meningiomas . We studied four genes by northern blotting: multidrug-resistance (MDR 1), glutathione-s transferase (GST pi), dihydrofolate reductase (DHFR), and topoisomerase II (Topo II) . The Topo II gene was absent in the normal adult brain (100%) and in 64% of the tumour samples tested . A second gene, GST pi, was found to be overexpressed in 38% of brain tumours . The two other chemoresistance-related genes were occasionally overexpressed in brain tumours (2% for MDR1, 9% for DHFR) . Our results provide evidence that chemoresistance is intrinsic to the brain tissue and seems likely to be a multifactorial process. Cancer Chemother Pharmacol, 1993, 31(5), 401 - 6 In vitro assessment of N-{2-(dimethylamino)ethyl}acridine-4-carboxamide, a DNA-intercalating antitumour drug with reduced sensitivity to multidrug resistance; Finlay GJ et al.; The successful treatment of cancer requires the identification of new drugs with novel actions . N-{2-(Dimethylamino)ethyl}acridine-4-carboxamide dihydrochloride (DACA) is a topoisomerase II-targeted antitumour drug with curative activity against murine Lewis lung carcinoma . DACA was assessed for novel patterns of growth inhibition using normal and multidrug-resistant human cell lines . Cells were cultured in 96-well microtitre trays and tested against DACA and related topoisomerase-directed drugs, including amsacrine, etoposide and doxorubicin, and drug concentrations for 50% growth inhibition (IC50 or GI50 values) were determined . In a series of Jurkat leukaemia lines characterised as exhibiting atypical multidrug resistance, DACA was to a large extent capable of overcoming multidrug resistance exhibited towards the other topoisomerase-directed agents . DACA was also tested against the National Cancer Institute 60-tumour-specific cell-line panel (GI50 values ranging from 420 to 5,400 nM; mean, 2,100 nM) and against a series of primary cultures of surgically excised melanomas (IC50 values ranging from 60 to 1,600 nM; mean, 590 nM) . DELTA values (deviations of logarithmic IC50 or GI50 values from the mean) were calculated and compared by correlation analysis . The standard deviation of DELTA values was found to be lower for DACA than for the other topoisomerase II-directed drugs amsacrine, etoposide, doxorubicin and mitozantrone in both the cell lines and the primary cultures . These lower standard deviations appear to have resulted from the reduced susceptibility of DACA to both P-glycoprotein- and topoisomerase II-mediated multidrug-resistance mechanisms occurring naturally in cell lines and primary cultures. Oncol Res, 1993, 5(2), 75 - 82 Cytoplasmic membrane cholesterol and doxorubicin cytotoxicity in drug-sensitive and multidrug-resistant human ovarian cancer cells; Mazzoni A et al.; The possible involvement of cholesterol (CHOL) in the cellular transformations leading to the acquisition of the multidrug-resistance (MDR) phenotype has been evaluated in human ovarian cancer cells . To this end, the A2780 cell line and the 52-fold doxorubicin (DX)-resistant counterpart A2780-DX3 were analyzed under two different growth conditions: standard culture medium (FCS medium), or medium deprived of CHOL (LPDS medium) . The following variables were investigated: free and esterified cytoplasmic membrane CHOL, cell growth, DX uptake and cytotoxicity, and low-density lipoprotein uptake and degradation (as indirect variables of CHOL homeostasis) . The impact of the calcium antagonist verapamil (VER) on these variables was assessed . The results obtained indicate that under standard growth conditions, A2780 and A2780-DX3 cells are different not only with respect to DX uptake and sensitivity, but also with respect to membrane CHOL content and the ratio of free-to-esterified CHOL . The deprivation of lipoproteins in the culture medium, apart from slowing cell growth, induced a decrease in the cytoplasmic membrane CHOL content (mainly of the esterified form) that was particularly evident in A2780 sensitive cells . In LPDS medium, a reduced DX uptake occurred in both cell lines, but to a greater extent in A2780 cells, in which DX cytotoxicity decreased to values comparable to that of A2780-DX3 resistant cells . Restoration of DX sensitivity was achieved with the addition of 10 microM VER.(ABSTRACT TRUNCATED AT 250 WORDS) Trop Gastroenterol, 1993 Jan-Mar, 14(1), 21 - 7 The anatomy of an epidemic (the final report on an epidemic of multidrug resistant enteric fever in eastern India); Anand AC; Two hundred and forty two patients of enteric fever were treated at Command Hospital (EC) Calcutta, during the period 1989-90 . The mean age of the patients was 28.4 (range 2-60) years and 119 (49.2%) of them were males . Fever (100%), headache (55%), diarrhoea (25.2%), intestinal bleeding (2.9%) and icterus (3.7%) were the main presenting features . Blood cultures were positive in 216 (%) patients . A majority of the isolates were found to be resistant to all four commonly used drugs for enteric fever i.e . chloramphenicol, ampicillin, cotrimoxazole and furazolidone . The commonest phage type found in the resistant strains was 51 (biotype-1) . Two plasmids of 14 and 120 kd size were detected in the resistant strains but not in the sensitive strains . Clinical response to gentamicin was not satisfactory in spite of all strains showing in vitro sensitivity . Ciprofloxacin proved to be a safe and effective drug for the treatment of multidrug resistant enteric fever. Cancer Chemother Pharmacol, 1993, 32(5), 396 - 8 Tamoxifen stimulates in vivo growth of drug-resistant estrogen receptor-negative breast cancer; Maenpaa J et al.; An estrogen receptor-negative, multidrug-resistant MDA-MB-A1 human breast cancer cell line was grown in culture with and without a noninhibitory concentration (0.5 microM) of tamoxifen for 122 days . Tamoxifen-treated and control cells were inoculated into opposite flanks of nine nude mice, where they produced measurable tumors in every case . Six of the animals were treated with tamoxifen at 500 micrograms/day for 22 days . Although no inhibitory nor stimulatory effect of tamoxifen was seen in vitro, tamoxifen had a clear tumor-growth-stimulating effect in mice . The most pronounced stimulatory effects were observed in the cells that had been cultured with tamoxifen . Within 3 weeks of the start of tamoxifen therapy, the cells grown in the presence of tamoxifen produced tumors with a mean size of 380 mm2, whereas the cells not pretreated with tamoxifen had tumors of 220 mm2 . In contrast, in mice not receiving tamoxifen, the sizes of the tumors were 190 and 140 mm2, respectively . These preliminary results suggest that prolonged in vitro tamoxifen exposure induces cellular changes that result in tumors that are stimulated to grow faster in mice following tamoxifen treatment. Ann Oncol, 1993, 4 Suppl 4, 57 - 62 Advanced ovarian cancer . Drug resistance, supportive care and dose intensity; de Vries EG et al.; BACKGROUND: Both intrinsic and acquired drug resistance occur in ovarian cancer . Much work on in vivo or in vitro, obtained drug resistance has been done and this knowledge is presently being converted into clinical studies . MATERIALS AND METHODS: The review focuses on the detoxifying system, MDR (multidrug resistance), and supportive care in relation to dose intensity . RESULTS: In vitro models suggest that the amount of glutathione, glutathione S-transferase activity or metallothioneins could play a role in the outcome of chemotherapy treatment . The results of human tumour samples studies however do not support this idea . Expression of the cell membrane P-glycoprotein in tumour cells appears in vitro to be an important adverse prognostic factor concerning the effect of natural products . Again the results in human tumour samples vary . The supportive agent sodium thiosulphate protects against cisplatin induced nephrotoxicity, but the exact role of sulphur compounds in ameliorating the neurotoxicity is not yet established . The neuropeptide Org 2766 may be a possible neuroprotector . Hemopoietic growth factors such as GM-CSF, G-CSF and interleukin-3, protect the bone marrow to varying degrees . Autologous bone marrow transplantation induces high, but often short lasting response rates in chemotherapy resistant patients . CONCLUSIONS: More clinical studies on intervention of drug resistance and on high dose chemotherapy are needed to define the role of these strategies in ovarian cancer. Microbios, 1993, 76(309), 251 - 61 Use of beta-lactam/beta-lactamase-inhibitor combinations as antimycobacterial agents; Prabhakaran K et al.; Mycobacterium tuberculosis and Mycobacterium leprae develop resistance against the drugs used to treat tuberculosis and leprosy, respectively . Now multidrug-resistant tuberculosis is spreading in many countries, especially with the emergence of AIDS . Multidrug treatment is being promoted at present to eradicate leprosy . Since M . leprae may also become multidrug-resistant, new approaches have to be adopted for controlling mycobacterial diseases . Mycobacteria usually synthesize beta-lactamase and are insensitive to beta-lactam antibiotics . M . tuberculosis contains a constitutive beta-lactamase; de-repression of beta-lactamase has been reported in M . leprae . Three different beta-lactam/beta-lactamase-inhibitor combinations (ampicillin/sulbactam, amoxicillin/clavulanate and piperacillin/tazobactam) were used to suppress the growth of several strains of mycobacteria (including M . tuberculosis H37Rv) in vitro . Ampicillin/sulbactam is a potent bactericidal agent against M . leprae multiplying in mouse foot pads . In the present work, ampicillin/sulbactam showed higher activity than the other drug combinations . The beta-lactam/beta-lactamase inhibitors are likely to be effective as rational therapeutic agents against mycobacterial infections. J Cancer Res Clin Oncol, 1993, 120(1-2), 27 - 34 Effects of interferon gamma on the proliferation and modulation of cell-surface structures of human ovarian carcinoma cell lines; Mobus VJ et al.; Platinum-containing regimens are very effective in the primary treatment of ovarian cancer . However, upon subsequent treatment most tumors develop multidrug resistance . The clinical application of biological response modifiers like interferon gamma (IFN gamma) in advanced ovarian cancer is therefore of increasing interest . Permanent ovarian cancer cell lines are suitable for investigating the mode of action and the potential clinical effectiveness of such response modifiers . IFN gamma is known to modulate many cellular functions . In this study it was compared for its antiproliferative and antigen-modulatory activity on the expression of tumor-associated (CA-125, HMFG, CEA) and major histocompatibility complex (MHC) class I and II antigens as well as of the epidermal growth factor (EGF) receptor on 20 newly established human ovarian carcinoma cell lines . IFN gamma in concentrations of 10, 50 and 100 U/ml was used to study its antigen-modulatory effect, and at additional 1 U/ml and 1000 U/ml to assess its antiproliferative effect on the cells . The cells were incubated with IFN for 4 days . Two cell lines showed strong antiproliferative activity even at minimal doses (up to 50 U/ml) . Intermediate growth inhibition between 34% and 84% was observed in 15 cell lines with higher doses . Three lines were resistant to IFN gamma . Independent of the antiproliferative effect, IFN gamma enhanced the expression of MHC class I and MHC class II in nearly all cell lines . Upregulation was also observed for most of the tumor-associated antigens (TAA) and EGF receptor expression . A down-regulation was noticed but rarely . The fact that IFN gamma showed an antiproliferative activity on the majority of the cell lines is of clinical relevance . The in vitro modulation of cell-surface determinants by IFN gamma warrants special attention . The enhanced expression of TAA and MHC antigens can improve immunogenicity of the tumor cells and may explain the therapeutic effects observed under IFN therapy in ovarian cancer . By contrast, enhanced expression of the EGF receptor, often associated with poor patient survival rates, may be an undesirable side-effect of IFN therapy. Cancer Chemother Pharmacol, 1993, 33(1), 10 - 6 Effects of the methoxymorpholino derivative of doxorubicin and its bioactivated form versus doxorubicin on human leukemia and lymphoma cell lines and normal bone marrow; Kuhl JS et al.; The methoxymorpholino derivative of doxorubicin (MMDX; FCE 23672) has recently entered clinical trials because of its broad spectrum of preclinical antitumor activity and non-cross-resistance in multidrug-resistant (MDR) tumor models . MMDX is activated in the liver to a > 10 times more potent metabolite that cross-links DNA . To assess the potential of this drug in hematologic malignancies, we studied the myelotoxicity in vitro and antitumor effect of MMDX as well as its bioactivated form (MMDX+) in a panel of 14 different human leukemia and lymphoma cell lines . The tumor specificity of MMDX in CEM and K562 cells was similar to that of doxorubicin (DOX), and that of MMDX+ was slightly superior . All of the 14 cell lines were found to be more sensitive to MMDX and MMDX+ than were granulocyte-macrophage progenitors . On a molar basis, MMDX was approximately 3-100 times more active than DOX, and MMDX+ was 10-1,000 times more potent than DOX . The cytotoxic effect of MMDX and MMDX+ in two P-glycoprotein-positive MDR sublines was greatly improved in comparison with that of DOX . Whereas the response to DOX in the different leukemia and lymphoma cell lines was highly heterogeneous, the response to MMDX and MMDX+ was rather homogeneous . The novel anthracycline MMDX and its bioactivated form MMDX+ are highly active against this panel of human leukemia and lymphoma cell lines and demonstrate potentially greater selectivity for tumor cells in vitro as compared with normal bone marrow precursors. Oncol Res, 1993, 5(3), 119 - 26 31P and 13C NMR spectroscopic study of wild type and multidrug resistant Ehrlich ascites tumor cells; Rasmussen J et al.; Steady-state 31P NMR spectra of wild type EHR2 Ehrlich ascites tumor cells and multidrug resistant EHR2/DNR+ cells, immobilized in agarose threads, and continuously perfused with medium, showed temperature-dependent differences in the levels of intracellular phosphate metabolites . At 37 degrees C, the EHR2/DNR+ cells contained four times more phosphocreatine (PCr) than the EHR2 cells . At 20 degrees C, the EHR2 cells contained 80% more of phosphodiesters (PDE), the levels of PCr being equal . The quantitative metabolite level data are based on T1 relaxation times data and are normalized for the protein content of the cells . Perfusion of the cells with azide, an inhibitor of mitochondrial respiration, had no effect on the ATP level, and caused no changes in glucose consumption and lactate production . Azide perfusion, combined with glucose depletion, caused rapid drop in the ATP content, which was reestablished after renewed perfusion with glucose . Similarly, perfusion with 2,4-dinitrophenol, an uncoupler of the respiration chain, had no effect on the phosphate metabolites . These results demonstrate that aerobic glycolysis is the main route by which glucose is metabolised under the conditions used (glucose concentration in medium 2 g/L) . Rates of uptake and phosphorylation of 2-deoxy-D-glucose were measured by following the formation of intracellular {6-13C}2-deoxy-D-glucose-6-phosphate by 13C NMR; at 37 degrees C the observed rates for EHR2 and EHR2/DNR+ cells were equal, about 10 nmol/(min x mg protein), whereas at 20 degrees C the wild type cells produced the 6-phosphate at an approximately twice the rate found for the resistant cells {about 4 and 2 nmol/(min x mg protein), respectively}.(ABSTRACT TRUNCATED AT 250 WORDS) Life Sci, 1993, 53(25), PL433 - 8 Gossypol inhibits basal and estrogen-stimulated DNA synthesis in human breast carcinoma cells; Hu YF et al.; Estrogen stimulates the growth of hormone-dependent human breast cancer . Failure of chemotherapy frequently results from the development of multidrug resistance . Gossypol (GP), a naturally occurring toxin, inhibits the growth of various carcinoma cells . Thus, the effects of GP on 17 beta-estradiol (E2)-stimulated DNA synthesis were studied in two hormone-dependent human breast carcinoma cell lines: the wild-type MCF-7 and the multidrug-resistant MCF-7 Adr cells . Cells (5 x 104/well) were cultured for 24 hrs in a chemically-defined, serum-free medium consisting of 1:1 mixture of Dulbecco's Modified Eagle's medium and Ham's nutrient mixture F12 (DMEM/F12) supplemented with insulin (5.0 micrograms/ml), transferrin (5.0 micrograms/ml), epidermal growth factor (EGF; 10.0 ng/ml) and antibiotics E2 (0 or 10.0 nM), GP (0, 2.5, 5.0, 10.0 or 20.0 microM) and bovine serum albumin (BSA; 0 or 0.1 mg/ml) were used as treatments in a factorial experimental design . Cells were treated for 24 hrs and finally pulsed with 3H-thymidine (5.0 microCi/ml) for 3 hrs . E2 significantly stimulated 3H-thymidine incorporation in both MCF-7 and MCF-7 Adr cells . GP at 10.0 and 20.0 microM inhibited both basal and E2-stimulated DNA synthesis in human breast cancer cells . The inhibitory effects of GP at 10.0 microM, but not at 20.0 microM, were blocked by BSA treatment . Results from the present study indicate that GP treatment was antiproliferative in both drug-sensitive and multidrug-resistant cancer cells and that the antiproliferative effects of GP on human breast cancer cells were mediated through mechanisms independent of estrogenic responses . Thus, GP could be potentially very useful for treatment of human breast cancer patients, especially those who have developed multidrug resistance. Tumour Biol, 1993, 14(5), 288 - 94 Cytotoxic effect of the protein-doxorubicin conjugates on the multidrug-resistant human myelogenous leukemia cell line, K562, in vitro; Hatano T et al.; In vitro studies were performed to examine the antitumor effect of protein-doxorubicin (DXR) conjugate on the growth of the multidrug-resistant human chronic myelogenous leukemia cell line, K562/DXR . The 50% inhibitory concentration (IC50) for DXR in the K562/DXR cell line was 20 nM (in the K562 parental cell line, IC50 was 3.2 nM) . Treatment of both types of cells with various concentrations of DXR or conjugates at equivalent concentrations of DXR was carried out . One type of the conjugates used was human serum albumin (HSA)-DXR conjugate and human transferrin (Tf)-DXR conjugate via a glutaraldehyde bridge (HSA-ga-DXR, Tf-ga-DXR, respectively) and another type used was HSA-DXR conjugate with a dextran bridge (HSA-dex-DXR) . All of these conjugates showed potent dose-dependent inhibition of cell growth against the K562/DXR cells as compared with the cells treated with DXR or other controls . IC50 for HSA-ga-DXR, Tf-ga-DXR and HSA-dex-DXR conjugates in the K562/DXR cell line was 2.4, 3.6 and 1.0 (equivalent DXR) nM, respectively, which were approximately similar to the value of the K562 treated with DXR . Through the treatment of K562/DXR cells with HSA-DXR conjugate, the intracellular drug concentration increased as a function of time up to 24 h compared with the cells treated with DXR . Intracellular DXR effluxed rapidly from K562/DXR cells, but HSA-ga-DXR as well as HSA-dex-DXR conjugates remained in the cells at a relatively high concentration for a long time . These results indicate that it may be possible to overcome multidrug resistance by chemically modifying DXR, such as by conjugation of the drug with proteins. Free Radic Res Commun, 1993, 19(6), 355 - 69 High field proton NMR investigations of the metabolic profiles of multidrug-sensitive and -resistant leukaemic cell lines: evidence for diminished taurine levels in multidrug-resistant cells; Jiang XR et al.; High field proton (1H) nuclear magnetic resonance (NMR) spectroscopy has for the first time been employed to investigate and compare the metabolic profiles of vinblastine-sensitive and -resistant T-lymphoid leukaemic cell lines (CCRF-CEM and CEM/VLB100 respectively) and evidence is presented for a significantly lower taurine content in the CEM/VLB100 resistant subline when expressed relative to that of its drug-sensitive parental counterpart . These data suggest differences in the nature and relative involvements of taurine biosynthetic pathways between the two cell lines, a phenomenon that may be related to their differing sensitivities towards chemotherapeutic agents such as adriamycin which promote the generation of cytotoxic reactive oxygen species (ROS) in vivo . However, the 1H NMR data obtained provided no evidence for an increased metabolic consumption of hypotaurine (a metabolic precursor of taurine with powerful .OH radical scavenging properties) in CCRF-CEM cells since differences observed in the hypotaurine: taurine concentration ratio between the drug-sensitive and -resistant cell lines were not statistically significant . Furthermore, hypotaurine is unlikely to compete with alternative endogenous .OH radical scavengers present such as lactate since its level in either of the two cell lines investigated (ca . 6.0 x 10(-8) mol./10(8) cells) is insufficient for it to act as an antioxidant in this context . The biochemical and therapeutic significance of these results are discussed. Acta Biochim Pol, 1993, 40(4), 487 - 96 Interactions between the gene products of pma1 encoding plasma membrane H(+)-ATPase, and pdr1 controlling multiple drug resistance in Saccharomyces cerevisiae; Ulaszewski S; In Saccharomyces cerevisiae, the pma1 mutations controlling the vanadate resistance of the H(+)-ATPase activity from the plasma membrane, map on chromosome VII in the vicinity of pdr1 mutations controlling multiple drug resistance . However, the pma1-1 mutants exhibit a genotype and a multidrug resistant phenotype quite different from those obtained for pdr1 mutants . Quantitative modifications of cycloheximide and N,N'-(p-xylylidene)-bis-aminoguanidine-2HCl resistance are observed in diploids containing the pma1 and pdr1 genes in trans configuration . Each of the pdr1 mutations interacts with pma1 as shown by a decrease in the ATPase activity in pdr1/pma1 diploids . The in vitro resistance of ATPase activity to vanadate is totally or partially suppressed in pdr1 mutants in haploid double mutants . These results suggest that the expression of PMA1 might be controlled by the PDR1 gene product. Oncol Res, 1993, 5(6-7), 207 - 12 Toremifene enhances cell cycle block and growth inhibition by vinblastine in multidrug resistant human breast cancer cells; Baker WJ et al.; The clinical study of compounds that modulate multidrug resistance has been hindered by both the toxicities of these agents and the inability to monitor their effectiveness at the level of the tumor cell . Previously, toremifene has been shown to be well tolerated clinically and to sensitize multidrug resistant cells to the effects of cytotoxic chemotherapeutic agents . The chemosensitizing properties of toremifene in estrogen receptor negative, multidrug resistant MDA-MB-A1 human breast cancer cells were studied using flow cytometric analysis and growth inhibition assays . Cell cycle kinetics of MDA-MB-A1 cells were not significantly affected by treatment with either toremifene, N-desmethyltoremifene, Toremifene IV or vinblastine alone, as the majority of cells remained in G0/G1 . However, preincubation with toremifene or one of its metabolites for 72 hours followed by treatment for one hour with vinblastine caused a marked shift of cells to G2/M, as cells appeared to be blocked in that phase of the cell cycle . This result was nearly identical to the effect of vinblastine alone on vinblastine-sensitive MDA-MB-231 breast cancer cells and can be interpreted as a "resensitization" by toremifene of MDA-MB-A1 cells to vinblastine . This chemosensitizing effect of toremifene was accompanied by an enhanced inhibition of cell growth by vinblastine . The chemosensitizing effects of toremifene or one of its metabolites in combination with cytotoxic chemotherapy can be effectively monitored by flow cytometry, an easily accessible technique. Eur J Cancer, 1993, 29A(16), 2264 - 8 Antiproliferative activity of thermosensitive liposome-encapsulated doxorubicin combined with 43 degrees C hyperthermia in sensitive and multidrug-resistant MCF-7 cells; Merlin JL et al.; Thermosensitive liposome-encapsulated doxorubicin (TLED) was compared to free doxorubicin, at 37 degrees C or combined with 43 degrees C hyperthermia, in sensitive and multidrug-resistant MCF-7 human tumour cells using clonogenic assays . In the resistant subline, TLED was found to partly circumvent multidrug resistance (MDR) . The reversal was comparable to that obtained when verapamil was added to free doxorubicin . When hyperthermic treatment was applied, no difference in thermosensitivity was found between sensitive and resistant cells . The combination of hyperthermia with free doxorubicin did not reverse MDR . Hyperthermia and TLED yielded additive effects in the resistant cells while potentiation was observed in the sensitive cells . These results confirmed the usefulness of the liposome encapsulation of doxorubicin in reversing MDR . The possibility of obtaining additive cytotoxicity using TLED combined with hyperthermia may represent an alternative way of intensification of doxorubicin cytotoxicity concomitant with the circumvention of MDR without using MDR reversing agents, which often generate limiting toxic side-effects. Biol Cell, 1993, 78(1-2), 63 - 8 Flow cytometry: a useful technique in the study of multidrug resistance; Leonce S et al.; Flow cytometry has recently become a very important tool in the study of the mechanisms of multidrug resistance (MDR) . This technique allows rapid access to information regarding two characteristics related to the MDR phenotype: i) the level of overexpression of the P-glycoprotein; and ii) its functional aspect in expulsion of the cytotoxic agents to which the cell is exposed . In pharmacology, flow cytometry also allows evaluation of the capacity of modulating agents to reverse this resistance, and contributes a deeper insight into the mechanism of action of new molecules. Acta Haematol, 1993, 89(4), 184 - 8 Vitamin D3 administration and multidrug resistance in acute nonlymphoblastic leukemia; Petrini M et al.; This article reports preliminary results from a pilot study started in 1986 on patients with acute myeloblastic leukemia treated for several months with low-dose arabinosylcytosine and 1(OH)D3 . During treatment or at the time of relapse, a monoblastic component was frequently found . A high percentage of patients were P-170-positive . In 2 patients it was possible to show that blasts, previously P-170-negative, became positive after treatment . In these 2 patients, failure of clinical response to antileukemic therapy was associated with this phenotype . The addition of the revertant drug nicardipine to the previously inactive treatment induced a partial response . Thus, previously reported in vitro observations on the differentiating activity of vitamin D3 metabolites, possible induction of multidrug chemoresistance by differentiating agents and the revertant activity of the Ca++ antagonist nicardipine appear to be confirmed in vivo in the reported patients. Eur J Cancer, 1993, 29A(3), 389 - 94 Derivation and characterisation of a mouse tumour cell line with acquired resistance to cyclosporin A; Wright KA et al.; Cyclosporin A (CsA) is an effective modifier of multidrug resistance . We have studied (a) the possibility that cells grown in increasing concentrations of CsA acquire cellular resistance to the agent and, (b) whether such cells have a multidrug resistant phenotype . Sublines of the EMT6 mouse tumour cell line were developed which were able to grow in 75 and 200 micrograms/ml of CsA, respectively . The resistant sublines grew slowly in the presence of CsA but reverted to control growth rates, whilst maintaining resistance, when the drug was removed . P-glycoprotein (Pgp) was not detectable in the resistant sublines by immunocytochemistry . The CsA-resistant cells were not cross-resistant to doxorubicin or vincristine but showed a clear degree of cross-resistance to the calcium transport blocker, verapamil . Cellular accumulation of both {3H}CsA and {3H}daunorubicin was significantly increased in the EMT6/CsA200R subline compared with the parent line . In the EMT6 parent line, which expresses very low levels of Pgp, 10-30-fold sensitisation to doxorubicin may be achieved using 0.1-5 microgram/ml of CsA . Similar sensitisation by CsA was also seen in the CsA-resistant sublines. Eur J Cancer, 1993, 29A(3), 378 - 83 Verapamil enhances doxorubicin activity in cultured human renal carcinoma cells; Lai T et al.; Cells from 22 renal cell carcinomas (RCC) were established in culture . Sensitivity of the tumour cells to doxorubicin alone and in combination with racemic verapamil, which reverses multidrug resistance, was tested using a {75Se}selenomethionine uptake assay to measure protein synthesis . The effect of verapamil was expressed as a potentiation index: LD50doxorubicin/LD50doxorubicin + verapamil . The potentiation index in 15 of these carcinomas was determined for cells within the first 14 days of culture . At 3.3 mumol/l concentration of verapamil, of the tumours sensitive to doxorubicin alone (LD50 < 0.75 microgram/ml) five of seven showed a potentiation index of > 2 . For the less sensitive tumours the analogous proportion was seven of eight . Tumour cell expression of glycoprotein P-170, associated with multidrug resistance, was estimated using the monoclonal antibody C-219 . Initial expression levels were unrelated to the action of verapamil . In five tumours the proportion of cells expressing P-170 declined as the period of culture increased . This was not associated with any consistent change in the LD50 for doxorubicin or in potentiation of doxorubicin sensitivity by verapamil . Cell cloning associated with prolonged cell growth in vitro could mimic tumour cell cloning which accompanies the formation of metastases . Thus reduced expression of P-170 on prolonged cell growth in vitro may be a pointer to the efficacy of combination therapy in the treatment of patients with metastatic renal cell carcinoma. Mol Carcinog, 1993, 8(2), 67 - 73 Activation of distinct multidrug-resistance (P-glycoprotein) genes during rat liver regeneration and hepatocarcinogenesis; Teeter LD et al.; The multidrug transporter P-glycoproteins are encoded by three multidrug-resistance (mdr) genes in rodents, designated mdr1a (mdr3), mdr1b (mdr1), and mdr2 . Only the first two genes are functionally related to multidrug resistance . Activation of rodent mdr genes during liver regeneration and hepatocarcinogenesis has been reported . In mice, mdr1a is activated in hepatocellular carcinomas (HCCs) produced by various carcinogenic protocols, whereas both mdr1a and mdr2 are activated during liver regeneration . In this communication, we report isolating three gene-specific probes for the rat mdr homologues, which were used as probes in an RNase protection assay to demonstrate that mdr1b mRNA was expressed in HCCs induced by two different protocols . Furthermore, high levels of hepatic mdr1b mRNA but only moderate levels of mdr1a and mdr2 mRNA were seen in preneoplastic lesions in rats treated with 2-acetylaminofluorene . Likewise, highly elevated levels of hepatic mdr1b mRNA but only moderately increased levels of mdr1a and mdr2 mRNA were seen after partial hepatectomy . Nevertheless, the general patterns of tissue-specific expression of these three mdr genes were similar in rats and mice . These results reveal a complex hepatic gene expression pattern during hepatocarcinogenesis and hepatic proliferation for this conserved gene family in rodents. Eur Urol, 1993, 24(1), 156 - 60 Expression of P-glycoprotein and multidrug resistance in renal cell carcinoma; Naito S et al.; The expression of the multidrug-resistance gene product, P-glycoprotein was examined immunohistochemically in 31 untreated human renal cell carcinomas . In 17 of these, chemosensitivity to Adriamycin and vinblastine was also assessed by a microtiter succinate dehydrogenase inhibition test and the correlation between the expression of P-glycoprotein and intrinsic multidrug resistance was investigated . P-glycoprotein was detected in 16 (51.6%) of the 31 carcinomas . In the chemosensitivity test, 14 (82.4%) of the 17 carcinomas were estimated to be resistant to both drugs (multidrug resistant; MDR) . Eight (72.7%) of the 11 carcinomas with a positive expression of P-glycoprotein were MDR, and none of them were sensitive of both drugs . On the other hand, MDR carcinomas were not necessarily associated with the expression of P-glycoprotein . Eight (61.5%) of the 13 MDR carcinomas showed a positive expression of P-glycoprotein while the remaining 5 (38.5%) were negative . These results suggest that the expression of P-glycoprotein is an important factor responsible for the intrinsic MDR phenotype of renal cell carcinoma, however, there are probably other factors involved as well which have yet to be fully elucidated. J Cancer Res Clin Oncol, 1993, 119(10), 609 - 14 In vitro and in vivo chemosensitizing effect of cyclosporin A on an intrinsic multidrug-resistant rat colon tumour; Van de Vrie W et al.; Colon tumours are intrinsically resistant to chemotherapy and most of them express the multidrug transporter P glycoprotein (Pgp) . Whether this Pgp expression determines their resistance to anticancer agents in patients is not known . We report here on the reversibility of intrinsic multidrug resistance in a syngeneic, solid tumour model . CC531 is a rat colon carcinoma that expresses Pgp, as was shown with the monoclonal antibody C-219 . In vitro the sensitivity to doxorubicin, daunorubicin and colchicine was enhanced by the addition of the chemosensitizers verapamil and cyclosporin A (CsA), while the sensitivity to cisplatin was not enhanced . In a daunorubicin accumulation assay verapamil and CsA enhanced the daunorubicin content of CC531 cells . In vivo CsA was injected intramuscularly for 3 consecutive days at a dose of 20 mg kg-1 day-1 . This resulted in whole-blood CsA levels above 2 mumol/l, while intratumoral CsA levels amounted to 3.6 mumol/kg . In a subrenal capsule assay the maximal tolerable dose of doxorubicin (4 mg/kg) significantly reduced tumour growth . Doxorubicin at 3 mg/kg was not effective, but in combination with CsA this dose was as effective as 4 mg/kg doxorubicin . These experiments show that adequate doses of the chemosensitizing drug CsA can be obtained in vivo, resulting in increased antitumoral activity of doxorubicin in vivo . The in vitro and in vivo data together suggest that the chemosensitization by CsA is mediated by Pgp . This finding may have implications for the application of CsA and CsA-like chemosensitizers in the clinical setting. Hereditas, 1993, 118(2), 121 - 30 Amplification and overexpression of the mouse mdr 1a gene in nine independently derived multidrug-resistant SEWA murine cell lines; Stahl F et al.; Many different drugs may be used in selecting cells for multidrug resistance (MDR) . Enhanced expression and/or gene amplification is known to cause overproduction of membrane-bound 170,000 P-glycoproteins, responsible for the MDR . In rodents, the P-glycoproteins are encoded by a small gene family: mdr 1a, mdr 1b, and mdr 2 . To evaluate the relationship between the pattern of MDR and the selecting drug, nine MDR sublines were independently selected from a sensitive mouse tumor cell line, SEWATC13K, using three different drugs . Each MDR subline displayed amplification of one or more of the three mdr genes, but only one, mdr 1a, was consistently overexpressed . Thus, our results indicate that the pattern of mdr gene amplification and overexpression is independent of the selective agent . Furthermore, in four of the MDR sublines, where all three mdr genes had been originally amplified, pulsed field gel electrophoresis (PFGE) revealed that amplification of mdr 1a, only, was a second step of gene amplification . In addition, the gene for the calcium-binding protein, sorcin, was coamplified in eight of the nine MDR sublines . The sorcin gene was overexpressed in seven of these eight sublines . Finally, hybridizations with a probe homologous with a putative region of RFLP (restriction fragment length polymorphism), indicated that the amplified sequences originate from one or the other of the two homologous chromosomes with no preference. J Cancer Res Clin Oncol, 1993, 119(9), 527 - 32 Pharmacological and molecular characterization of intrinsic and acquired doxorubicin resistance in murine tumor cell lines; Schott B et al.; We have studied the pharmacological parameters of doxorubicin resistance in three lines of murine cells selected by long-term culture in the presence of this drug or vincristine . A line originating from rat hepatoma spontaneously presented an intrinsic doxorubicin resistance as compared to the other lines, originating from a rat glioblastoma and from simian-virus-40-transformed mouse hepatocytes . This intrinsic resistance, as well as the doxorubicin resistance exhibited by the vincristine-selected glioblastoma variant, could be entirely attribute to decreased drug accumulation due to drug efflux . In contrast, the doxorubicin-selected variants of the three lines exhibited an intracellular tolerance to this drug . Despite a reduction in drug accumulation when exposed to the same amount of doxorubicin, they accumulated 6-12 times more doxorubicin than wild lines when submitted to equitoxic exposures . Verapamil could restore in these lines the doxorubicin accumulation observed in sensitive lines but could not restore doxorubicin cytotoxicity . Quantitative evaluation of P-glycoprotein expression by Western blotting with the C219 antibody indicated that the wild hepatoma line overexpressed P-glycoprotein by a factor of 5 in comparison with the other wild lines, and that the vincristine-selected glioblastoma variant overexpressed this protein almost as much as the doxorubicin-selected variants . These observations favor the existence of P-glycoprotein-independent mechanisms of doxorubicin resistance, which are added to the classical multidrug-resistant phenotype in doxorubicin-selected highly resistant variant cell lines. Eur J Cancer, 1993, 29A(8), 1078 - 81 Multiple drug resistance in the human ovarian carcinoma cell line OAW42-A; Redmond A et al.; A new multidrug-resistant variant (OAW42-A) of a human ovarian carcinoma line has been selected by exposure to increasing concentrations of doxorubicin . The variant is resistant to doxorubicin, vincristine (but surprisingly not to colchicine), etoposide, tenoposide and also to cisplatin (a drug not usually involved in classical multidrug resistance), but not to 5-fluorouracil . Overexpression of P-glycoprotein in the resistant line was demonstrated by immunofluorescence and western blotting . Direct evidence for P-glycoprotein as a determinant of resistance was provided by transfection with a specific antisense oligonucleotide . Reversal was incomplete and this, along with the pattern of cross-resistance observed, suggests that additional mechanisms of resistance may also be involved . Substantial clonal variation in resistance exists within the cell line. Eur J Cancer, 1993, 29A(7), 1024 - 7 Clinical application of a rapid, functional assay for multidrug resistance based on accumulation of the fluorescent dye, fluo-3; Wall DM et al.; A rapid and simple functional assay for P-glycoprotein (Pgp) using flow cytometry to measure the accumulation of the flurophore fluo-3 has been applied to samples from patients with B-cell chronic lymphocytic leukaemia (B-CLL) . Peripheral blood lymphocytes from 37 patients with B-CLL were studied for Pgp . Pgp expression, using MRK-16, a monoclonal antibody recognising an external surface epitope of Pgp, was detected in 92% of patients with B-CLL . The functional assays for Pgp expression were positive in 78 and 59% of patients using the fluo-3 and doxorubicin (dox) assays, respectively . When compared with the MRK-16 assay, the fluo-3 assay had a sensitivity of 82% compared to a sensitivity of 56% for the dox assay (P = 0.004) . The specificity of the fluo-3 and dox assays could not be evaluated because of the low number of MRK-16 negative CLL cells. Haematologica, 1993 Jan-Feb, 78(1), 12 - 7 Expression of multidrug resistance gene (MDR-1) in human normal leukocytes; Damiani D et al.; BACKGROUND . The mdr-1 gene, which codes for a 170-kd transmembrane glycoprotein (P170), is frequently overexpressed in multidrug resistant (MDR) tumor cell lines and in spontaneous tumors, including leukemia and lymphoma . However, it is also constitutively expressed as a normal gene in normal tissues . METHODS . We used human mdr-1 cDNA and three anti-P170 monoclonal antibodies (MoAbs: MRK-16, C-219 and JSB-1) to investigate the normal peripheral blood leukocyte content of mdr-1 specific mRNA and of P170 through immunocytochemistry and flow cytometry . RESULTS . We did not find any increase in mdr-1-specific mRNA, while small amounts of P170 were easily detectable in about two thirds of the lymphocytes and monocytes and in about one third of the granulocytes . The level of P170 expression in leukocytes was similar to that found in non-MDR tumor cell lines . CONCLUSIONS . mdr-1 is constitutively expressed in human normal leukocytes at levels that cannot significantly affect drug resistance . Accordingly, low-level mdr-1 expression in leukemic cells should not be considered a label of pleiotropic drug resistance. Cancer Chemother Pharmacol, 1993, 32(2), 151 - 5 Influence of sequential exposure to R-verapamil or B8509-035 on rhodamine 123 accumulation in human lymphoblastoid cell lines; Roller E et al.; Modulators for the reversal of multidrug resistance such as R-verapamil and B8509-035, a dihydropyridine, effectively overcome multidrug resistance in vitro and are currently undergoing clinical trial . One problem with their use is the application protocol; the question as to whether they should be given by continuous administration or in sequential doses in combination with the cytotoxic drugs has to be addressed . Therefore, we examined the influence of the exposure time and the sequence of modulator administration on the active transport of the fluorescent dye rhodamine 123 (R123), a substrate for the P-glycoprotein, in the resistant lymphoblastoid cell line VCR1000 and the parental nonresistant cell line CCRF-CEM . Our results demonstrate the importance of coadministration of R-verapamil and the cytotoxic agent for the modulation