Cancer Lett, 1997 Jan 15, 112(1), 23 - 31 Lung resistance protein (LRP) expression in human normal tissues in comparison with that of MDR1 and MRP; Sugawara I et al.; MDR1 (P-glycoprotein), multidrug resistance-associated protein (MRP) and lung resistance protein (LRP) are associated with multidrug resistance in various cancer cells . It is known that P-glycoprotein and MRP are also expressed in several normal tissues . However, the exact location of LRP in normal tissues is still unclear . In order to obtain more insight into the physiological role of LRP, its expression in human normal tissues was examined by an immunohistochemical technique, using one monoclonal antibody, LRP-56 . Reverse transcriptase-polymerase chain reaction (RT-PCR) was also utilized for several cell lines and fresh-frozen tissues . P-glycoprotein was found to be expressed in the kidney, adrenal, brain vessels, muscle, lung, pancreas, liver, intestine, placenta and testis . MRP was expressed in the kidney, adrenal, lung, pancreas, muscle, intestine, thyroid and prostate, and its distribution mostly overlapped with that of P-glycoprotein . Interestingly, MRP was not expressed in the liver . LRP at 110 kDa was expressed in the kidney, adrenal, heart, lung, muscle, thyroid, prostate, bone marrow and testis . These findings suggest that LRP as well as P-glycoprotein and MRP plays distinct roles in the physiology of various organs. FEBS Lett, 1997 Jan 13, 401(1), 11 - 4 Anti-cancer drugs and glutathione stimulate vanadate-induced trapping of nucleotide in multidrug resistance-associated protein (MRP); Taguchi Y et al.; Multidrug resistance-associated protein (MRP), a member of the ABC superfamily transporters, functions as an ATP-dependent efflux pump that extrudes cytotoxic drugs from the cells . Although glutathione has been considered to play an important role in the function of MRP, there is no convincing evidence that glutathione directly interacts with MRP . Here we demonstrate that vanadate-induced trapping of 8-azido-ATP in MRP was stimulated in the presence of glutathione, oxidized glutathione and the anti-cancer drugs VP-16 and vincristine . MRP in membrane from a human MRP cDNA transformant was specifically photolabeled with 8-azido-{alpha-32P}ATP by the vanadate-trapping technique . Vanadate and Mg2+ were required for trapping of nucleotides, and vanadate trapping of nucleotides was inhibited by excess ADP as well as ATP . These results suggest that a stable inhibitory complex MRP x MgADP x Vi, an analog of the MRP x MgADP x Pi transition state complex, is formed in the presence of vanadate . Glutathione as well as anti-cancer drugs would directly interact with MRP, and stimulate the formation of the transition state of the ATPase reaction of MRP. J Biol Chem, 1997 Jan 10, 272(2), 1026 - 31 Role of multidrug resistance P-glycoproteins in cholesterol esterification; Debry P et al.; Cholesterol esterification, catalyzed by acyl-CoA:cholesterol acyltransferase (ACAT), plays a central role in cellular cholesterol homeostasis and in physiologic processes that lead to coronary heart disease . Although ACAT resides in the endoplasmic reticulum (ER), the cholesterol substrate for esterification originates in the plasma membrane and must be transported to the ER for esterification . Progesterone inhibits esterification, possibly by blocking the transport of cholesterol to the ER . Recent studies suggest that progesterone acts by inhibiting the activity of one or more of the multidrug-resistant (MDR) P-glycoproteins . In the current manuscript, we demonstrate that progesterone's ability to inhibit esterification is not mediated through the progesterone receptor . We evaluate a series of steroid hormones and find a strong correlation between a steroid hormone's hydrophobicity and its ability to inhibit both cholesterol esterification and MDR-catalyzed drug efflux . We also find that cholesterol esterification is inhibited by nonsteroidal MDR inhibitors, and that this inhibition specifically affects the esterification of cholesterol derived from the plasma membrane . MDR inhibitors also inhibit cholesterol esterification in a wide range of cultured human cell lines . These observations suggest that MDR activity normally functions in a general process of intracellular cholesterol transport. Biochem Pharmacol, 1997 Jan 10, 53(1), 89 - 93 Inhibition of drug transport by genistein in multidrug-resistant cells expressing P-glycoprotein; Castro AF et al.; It has been claimed that the flavonoid genistein could be used to distinguish multidrug-resistant tumors expressing the multidrug resistance-associated protein (MRP) from those expressing P-glycoprotein (Pgp) . Genistein would be block drug transport by MRP without affecting Pgp-mediated drug transport . However, we found that exposure to 200 microM genistein elicited an elevation in intracellular accumulation of rhodamine 123 (R123) and daunorubicin (DNR) in Pgp-expressing cell lines . Genistein inhibited R123 efflux in a rapidly reversible manner (ca . 2 min) . The flavonoid also decreased photoaffinity labeling of Pgp by {3H}azidopine, a Pgp substrate . The present results show that genistein interacts with Pgp and inhibits Pgp-mediated drug transport . Hence, genistein cannot be used in simple assays to distinguish MRP- and Pgp-expressing cells. Biochem Pharmacol, 1997 Jan 10, 53(1), 59 - 66 Induction of pgp3 expression and reversion of the multidrug resistance phenotype in 9-OH-ellipticine-resistant Chinese hamster lung fibroblasts transfected with the MYC oncogene; Delaporte C et al.; Chinese hamster lung cells resistant to the DNA topoisomerase II inhibitor 9-OH-ellipticine (DC-3F/9-OH-E) are cross resistant to various drugs through the expression of the MDR phenotype . The myc oncogene was approximately 10-fold amplified and 20-fold overexpressed in parental DC-3F cells as compared with DC-3F/9-HO-E cells . Transfection of the resistant cells with a mouse c-myc gene did not alter the resistance to topoisomerase II inhibitors and, in cells with a low multidrug (MDR) expression, reversed this phenotype . Northern and Western blot analyses revealed an increased expression of pgp1 in the DC-3F/9-OH-E cells, which was not modified in the myc-transfected clones . However, myc expression in these clones resulted in an increased expression of pgp3, roughly in proportion to the level of myc expression . Transfection of the DC-3F/9-OH-E cells with the human MDR3 gene, homologous to pgp3, also resulted in the reversion of the MDR phenotype . These results show that (1) expression of the transfected myc gene positively regulates pgp3 expression but has no effect on pgp1; (2) when observed, reversion of the MDR phenotype is proportional to the levels of myc and pgp3 expression; and (3) this reversion, resulting from pgp3 expression, is associated with a decreased functional activity of the pgp1 protein and might require an appropriate balance of pgp1 and pgp3 expression. Biochem Pharmacol, 1997 Jan 10, 53(1), 17 - 25 Reversal of P-glycoprotein-associated multidrug resistance by ivermectin; Pouliot JF et al.; P-Glycoprotein (P-gp) causes a multidrug resistance (MDR) phenotype in tumour cells . In some cancers, the expression of P-gp has been correlated with low clinical response to chemotherapy and survival of patients . Previous studies have shown that certain lipophilic drugs bind to P-gp and reverse the MDR phenotype of tumour cells . In this study, we extend that list of compounds and present evidence for the capacity of a potent and clinically safe anthelmintic, ivermectin (IVM), as an MDR-reversing drug . Using a highly drug-resistant human cell line, we compared IVM with other MDR-reversing agents and showed that IVM is 4- and 9-fold more potent than cyclosporin A and verapamil, respectively . The capacity of IVM to inhibit iodoaryl-azidoprazosin photolabeling of P-gp is consistent with direct binding to P-gp . Studies showed that {3H}IVM binding to membranes from resistant cells is specific and saturable with KD and Bmax values of 10.6 nM and 19.8 pmol/mg, respectively . However, while cyclosporin A or vinblastine inhibited {3H}IVM binding to membranes from drug-resistant but not drug-sensitive cells, neither verapamil nor colchicine had any effect . Furthermore, both IVM and cyclosporin A and, to a lesser extent, verapamil also inhibited {3H}vinblastine binding to membranes from drug-resistant cells . Drug transport studies showed that {3H}IVM is a substrate for the P-gp drug efflux pump . However, it was transported less efficiently by P-gp than {3H}vinblastine . Moreover, only cyclosporin A was effective in potentiating the accumulation of {3H}IVM in drug-resistant cells . Taken together, the high efficiency of MDR reversal by IVM combined with its low toxicity are consistent with the properties of an ideal MDR-reversing agent. Biochem Biophys Res Commun, 1997 Jan 3, 230(1), 22 - 6 Effect of ATP binding cassette/multidrug resistance proteins on ATP efflux of Saccharomyces cerevisiae; Boyum R et al.; Multidrug resistance (MDR) in mammalian tumors or tissues is often associated with the overexpression of the putative drug efflux pump P-glycoprotein (Pgp) . One theory concerning the mechanism of Pgp activity is that efflux of ATP is coupled to drug efflux . Evidence in support of this theory has been observed in mammalian cells . Recently, the STS1 gene, which is a multidrug resistance gene related to the mammalian Pgp's, has been characterized in S . cerevisiae . Also, the mouse mdr3 Pgp has been functionally expressed in yeast cells . Therefore, it was of interest to determine whether the expression of these proteins affected ATP efflux from yeast . Although both genes were shown to confer MDR, thus confirming functional expression, the endogenous glucose-dependent, drug-stimulated ATP efflux activity of yeast was not affected by expression of STS1, and was decreased by the expression of mouse mdr3. FEBS Lett, 1997 Jan 3, 400(2), 145 - 8 Inhibition of phorbol ester-stimulated phospholipase D activity by chronic tamoxifen treatment in breast cancer cells; Kiss Z et al.; We have shown that in an estrogen receptor-negative multidrug-resistant subline of MCF-7 human breast carcinoma cells longer-term (24 h), but not shorter-term (30 min), treatments with clinically relevant (2-5 microM) concentrations of tamoxifen (TAM) inhibited phorbol ester-stimulated phospholipase D (PLD) activity by 50-80% . TAM caused these inhibitory effects without inducing membrane translocation or down-regulation of protein kinase C-alpha, the major mediator of phorbol ester effects on PLD activation . The results raise the possibility that prolonged inhibition of the protein kinase C-alpha-regulated PLD system may contribute to the cytotoxic effects of tamoxifen in estrogen receptor-negative breast cancer cells. Zentralbl Gynakol, 1997, 119(5), 195 - 203 {Significance of stem cell-supported high-dose chemotherapy in the treatment of gynecological malignancies: indications and current clinical trials in the Federal Republic of Germany}; Nitz U et al.; The use of hematopoetic growth factors and stem cell support reduces the dose limiting hematopoetic toxicity's, resulting in a remarkable increase in dose intensity of chemotherapy . As far as data from phase I/II trials are available high dose chemotherapy (HDC) may be integrated in the systemic treatment of breast and ovarian cancers . In metastatic breast cancer HDC may induce fairly high but short response rates . Long term survival is expected in 20% of the cases . Patients with limited metastatic disease, without significant prior chemotherapy, partial or complete response to induction chemotherapy and complete remission after HDC may benefit from HDC . In phase I/II trials HDC improved recurrence free survival in high risk patients (e.g . > 9 positive LN) compared to historic controls and may therefore be a curative approach . Ovarian cancer is very chemosensitive . Conventional chemotherapies induce multidrug resistance rapidly . Just as in breast cancer-Phase I/II trials demonstrated high response rates to HDC, which again were short of duration. Br J Cancer, 1997, 76(4), 486 - 93 The prognostic significance of expression of the multidrug resistance-associated protein (MRP) in primary breast cancer; Nooter K et al.; In the present study, we determined the frequency and intensity of MRP protein expression by monoclonal antibody immunohistochemistry in a series of 259 resected invasive primary breast carcinomas, and we evaluated MRP immunoreactivity in relation to patient and tumour characteristics, relapse-free (RFS) and overall survival (OS) . The immunostaining was graded on a semiquantitative scale that ranged from (-) to ( ) . Overall, 34% of the tumours were positive for anti-MRP antibody: 19% showed weak cytoplasmic staining (+), 14% had clear cytoplasmic staining (++) and only 1% of the tumours had a strong cytoplasmic as well as membranous staining ( ) . MRP expression was not related to patient's age, menopausal status, tumour size, differentiation grade, oestrogen and progesterone receptor level or lymph node involvement . In an exploratory univariate analysis of all patients, only primary tumour size and number of lymph nodes involved were significantly associated with shortened RFS (P < 0.001 and P < 0.001 respectively) and OS (P = 0.02 and P < 0.001 respectively) . In Cox univariate analysis for RFS in subgroups of patients stratified by menopausal status, tumour size, nodal status, adjuvant systemic therapy and oestrogen and progesterone receptor status, MRP expression was associated with increased risk for failure in patients with small tumours (T1), in node-negative patients and in node-positive patients who received adjuvant systemic chemotherapy with cyclophosphamide, methotrexate and 5-fluorouracil (CMF); the relative hazard rate (RHR) for relapse was increased in the presence of MRP, with RHR values with 95% confidence limits (CL) of 2.8 (1.2-6.9), 2.1 (1.0-4.2) and 2.8 (0.8-9.9) respectively . In analysis for OS, expression of MRP was also associated with increased risk for failure in patients with small tumours (T1) {RHR (95% CL) 2.3 (0.9-6.0)} and in node-positive patients who received adjuvant systemic chemotherapy with CMF {RHR (95% CL) 3.7 (0.8-17.1)} but not in node-negative patients {RHR (95% CL) 1.1 (0.4-2.6)} . In conclusion, our results show that MRP is frequently overexpressed in primary breast cancer and suggest that MRP expression might be of prognostic significance in the subgroups of patients with the more favourable prognosis, i.e . patients with small tumours and node-negative patients, as well as in the setting of adjuvant systemic chemotherapy . In primary breast cancer, MRP might be related to altered cell biological behaviour, including a more aggressive phenotype, and resistance to adjuvant systemic chemotherapy. Br J Cancer, 1997, 76(4), 445 - 50 Murine P-glycoprotein on stromal vessels mediates multidrug resistance in intracerebral human glioma xenografts; Takamiya Y et al.; Human glioma usually shows intrinsic multidrug resistance because of the blood-brain barrier (BBB), in which membrane-associated P-glycoprotein (P-gp), encoded by the human multidrug resistance gene MDR1, plays a role . We studied drug sensitivity to vincristine (VCR), doxorubicin (DOX) and nimustine (ACNU) in both intracerebrally and subcutaneously xenotransplanted human glioma . We examined the levels of MDR1 and murine mdr3 gene expression in the xenografts by reverse transcriptase polymerase chain reaction and the localization of P-gp by immunohistochemistry . Six of seven subcutaneously transplanted xenografts (scX) were sensitive to the above three drugs . In contrast, all three intracerebrally transplanted human glioma xenografts (icX) were resistant to P-gp-mediated drugs VCR and DOX, but were sensitive to the non-P-gp-mediated drug ACNU . Neither icX nor scX showed any MDR1 expression . Intracerebrally transplanted human glioma xenografts showed an increased level of murine mdr3 gene expression, whereas scX showed only faint expression . The localization of P-gp was limited to the stromal vessels in icX by immunohistochemistry, whereas scX expressed no P-gp . Our findings suggest that the P-gp expressed on the stromal vessels in icX is a major contributing factor to multidrug resistance in human glioma in vivo. Cancer Chemother Pharmacol, 1997, 40 Suppl, S20 - 4 New multidrug-resistance-reversing drugs, MS-209 and SDZ PSC 833; Naito M et al.; The emergence of multidrug resistance (MDR) is a major problem in cancer chemotherapy . Many compounds have been developed to reverse MDR, and some of them are undergoing clinical trials . Among them, MS-209, a novel quinoline derivative, is one of the most potent MDR-reversing agents: MS-209 at 3 microM effectively reverses MDR in various cell lines in vitro . MS-209 directly interacts with P-glycoprotein (Pgp) and inhibits Pgp-mediated drug transport . Oral administration of MS-209 combined with anticancer drugs significantly increases the life span of mice bearing MDR tumor cells without causing serious side effects . SDZ PSC 833, a non-immunosuppressive analogue of cyclosporin A (CsA), is another potent MDR-reversing drug . Interestingly, the MDR-reversing activity of SDZ PSC 833 is enhanced in vitro and in vivo by MRK-16, a monoclonal antibody that recognizes an extracellular epitope of Pgp . Since MRK-16 promotes immune responses to MDR tumor cells expressing Pgp, the combined use of MRK-16, SDZ PSC 833, and antitumor drugs could be an effective therapeutic modality to reverse MDR. Cancer Chemother Pharmacol, 1997, 40(5), 453 - 6 An N-myristoylated protein kinase C-alpha pseudosubstrate peptide that functions as a multidrug resistance reversal agent in human breast cancer cells is not a P-glycoprotein substrate; Bergman PJ et al.; Protein kinase C-alpha (PKC-alpha) activation is an important contributing factor in human breast cancer MCF-7 MDR cell drug resistance . We recently reported the use of N-myristoylated PKC-alpha pseudosubstrate peptides with potent PKC-alpha inhibitory activity as reversal agents of drug resistance in MCF-7 MDR cells . The peptides potently inhibit phosphorylation of the PKC-alpha substrates P-glycoprotein (P-gp), raf kinase and PKC-alpha itself in MCF-7 MDR cells in association with a severalfold induction of intracellular uptake of P-gp substrate chemotherapeutics and a statistically significant twofold increase in cellular chemosensitivity . We now report that the N-myristoylated PKC-alpha pseudosubstrate peptide N-myristoyl-RFARKGALRQKNV (P3) is not a P-gp substrate in MCF-7 MDR cells based on a comparison of the cellular uptake of {125I}-radiolabeled P3 in MCF-7 MDR vs MCF-7 WT cells . The extent of cellular uptake of the radiolabeled peptide in the drug-resistant cell line MCF-7 MDR was either greater than or equivalent to the uptake in the parental drug-sensitive MCF-7 WT cell line over a time course of 30 min to 6 h, and across a peptide concentration range of 25-100 microM . Additionally, treatment of the MCF-7 MDR cells with verapamil (VPL), a known P-gp efflux inhibitor, had no effect on the cellular accumulation of radiolabeled P3 . Our results provide direct evidence that the N-myristoylated pseudosubstrate peptide is taken up equivalently by drug-sensitive and MDR cancer cells and therefore has potential value as an MDR reversal agent that operates by a novel mechanism. Cancer Chemother Pharmacol, 1997, 40(5), 433 - 8 Differential cytotoxicity of clinically important camptothecin derivatives in P-glycoprotein-overexpressing cell lines; Hoki Y et al.; Camptothecin and its derivatives are specific inhibitors of eukaryotic topoisomerase I (top1) and are active in cancer patients against a variety of refractory solid tumors and leukemia . PURPOSE: The present study further investigated the relationship between multidrug resistance (MDR) mediated by P-glycoproteinMDR and potential resistance to camptothecin derivatives using two experimental systems: (1) MDR KB-V1 cells selected for vinblastine resistance, and (2) NIH3T3 cells transfected with a plasmid expressing wildtype P-glycoproteinMDR multidrug transporter (NIH-MDR-G185) . RESULTS: We found that both KBV-1 and NIH-MDR-G185 cells were resistant to topotecan, and that topotecan-induced cleavable complexes were reduced in KB-V1 cells, consistent with a role of P-glycoproteinMDR in cellular resistance to topotecan . By contrast, no significant resistance to camptothecin, 9-aminocamptothecin, 10, 11-methylenedioxycamptothecin, or SN-38 (the active metabolite of CPT-11) was observed in NIH-MDR-G185 cells, while KB-V1 cells were cross-resistant to these compounds but produced cleavable complexes similar to those produced by parental KB-3-1 cells . CONCLUSIONS: These results suggest that topotecan is the only camptothecin tested with significant susceptibility to MDR in cell culture, and that multidrug resistant cells such as KBV1 probably exhibit additional resistance mechanisms to camptothecins besides P-glycoproteinMDR overexpression. Cancer Chemother Pharmacol, 1997, 40(5), 425 - 32 A novel quinoline derivative, MS-209, overcomes drug resistance of human lung cancer cells expressing the multidrug resistance-associated protein (MRP) gene; Narasaki F et al.; PURPOSE AND METHODS: MS-209 is a newly synthesized quinoline compound used orally to overcome human P-glycoprotein (Pgp)-mediated multidrug resistance (MDR) . The multidrug resistance-associated protein (MRP) gene is thought to play an important role in MDR in lung cancer . To investigate whether MS-209 could also overcome MRP-mediated MDR, we examined the effect of the compound using a cytotoxicity assay on MDR1 gene-negative drug-selected MDR and wildtype lung cancer cells with various levels of MRP gene expression . The effects of MS-209 were compared with those of verapamil (VER) and cyclosporin A (CsA) . The level of MRP gene expression in the cells was evaluated semiquantitatively by RT-PCR . For vincristine (VCR), intracellular accumulation of {3H}-VCR was measured with or without MS-209 . RESULTS: In MDR UMCC-1/VP small-cell lung carcinoma cell line, 5 microM of MS-209 and VER enhanced the cytotoxicity of etoposide, doxorubicin (DOX) and VCR more than twofold, and completely reversed the resistance to VCR . The mean reversing effects of MS-209 on DOX and VCR were significantly stronger than those of VER and CsA . In wildtype non-small-cell lung carcinoma cells, the effects of MS-209 were almost equal to those of VER and CsA . The effect of these three agents correlated with the level of MRP gene expression . The MS-209-induced increase in intracellular accumulation of VCR was proportional to the level of MRP gene expression in these cells . CONCLUSION: Our results indicate that MS-209 is a potentially useful drug that can overcome MRP-mediated intrinsic and acquired MDR in human lung cancer. Annu Rev Nurs Res, 1997, 15, 153 - 84 Adherence to therapy in tuberculosis; Cohen FL; Tuberculosis (TB) is a leading cause of morbidity and mortality worldwide . In the United States, TB has undergone a resurgence and the appearance of multidrug-resistant TB has caused new concerns . A critical part of TB treatment is adherence to the prescribed therapy for a considerable time period . Treatment "failure" is often due to nonadherence . Many factors influence adherence to therapy in TB . This chapter reviews research in the area of adherence to the TB treatment plan in the United States and worldwide . It discusses adherence as an outcome related to treatment regimens such as directly observed therapy, patient characteristics, life and family circumstances, motivation, education, incentives, and combination strategies . Themes across studies are compared and suggestions for successful future studies are identified. Eur J Clin Pharmacol, 1997, 52(4), 307 - 10 Pharmacokinetics and bioavailability of oral and intramuscular artemether; Karbwang J et al.; OBJECTIVE: The pharmacokinetics and bioavailability of artemether and dihydroartemisinin were investigated in eight Thai males following the administration of single oral and intramuscular doses of artemether (300 mg) in a randomized two-way cross-over study . RESULTS: Both oral and intramuscular artemether were well-tolerated . In most cases, artemether and dihydroartemisinin were detected in plasma after 30 min and declined to levels below the limit of detection within 18-24 h . Compared with intramuscular administration, oral administration of artemether resulted in a relatively rapid but incomplete absorption {Cmax: 474 vs 540 ng.ml-1; tmax: 2.0 vs 3.9 h; AUC: 2.17 vs 5.20 micrograms.h.ml-1} . Geographic means of lag-time and absorption half-life (t1/2a) of oral vs intramuscular artemether were 0.28 and 1.1 h vs 0.30 and 2 h, respectively, t1/2z was significantly shortened after the oral dose {2.8 vs 6.9 h} . Mean oral bioavailability relative to intramuscular administration was 43.2% . The ratio of the AUCs of artemether to dihydroartemisinin was significantly lower after the oral than after the intramuscular dose (geometric mean: 0.29 vs 0.60) . artemisinin, which is commercially available in China, Vietnam, Thailand and some African countries . The drug is administered as solution in oil for intramuscular injection or as oral tablets . The clinical efficacy of artemether is dependent on the formulation, dosing scheme, duration of treatment, and the severity of the disease {1, 2} . Oral artemether is effective but with short-term treatment, the relapse rate is high . While the efficacy of intramuscular artemether against multidrug-resistant P . falciparum in either uncomplicated or severe cases has been confirmed, its pharmacokinetic documentation is limited . Formulations with high bioavailability and low costs are essential . With high-performance liquid chromatography and electrochemical detection, more sensitive and reliable assay of artemisinin and derivatives in biological fluids has been achieved {3-4} . In the present study, we have assessed the pharmacokinetics and bioavailability of oral and intramuscular artemether, in healthy Thai males. Br J Cancer, 1997, 76(2), 211 - 9 Cytotoxic activity of topotecan in human tumour cell lines and primary cultures of human tumour cells from patients; Jonsson E et al.; The cytotoxic activity and cross-resistance pattern of the novel topoisomerase I inhibitor topotecan (Topo) were investigated in ten cell lines, representing different mechanisms of cytotoxic drug resistance, and in 218 fresh human tumour samples using the fluorometric microculture cytotoxicity assay (FMCA) . Resistance to Topo in the cell lines was associated with expression of the multidrug resistance-associated protein (MRP), whereas the cell lines with P-glycoprotein (P-gp), topoisomerase II and glutathione-associated resistance did not show decreased sensitivity to the drug . Topo was more active in haematological than in solid tumour samples, but substantial activity was observed in carcinomas of the ovary and breast, sarcoma and childhood solid tumours . Cross-resistance to standard drugs representing different mechanisms of action was generally low in patient cells . The effect of Topo was better after longer exposure, but this time-dependent effect was largely abolished when adjustment for in vitro exposure was made . Topo showed activity both in proliferative and non-proliferative cell systems . The results indicate that Topo is insensitive to major mechanisms of resistance except for MRP . Proliferation does not seem to be necessary for the effect of Topo, and no superiority for protracted dosing schedules was observed . The results also suggest that, for example, leukaemias, lymphomas, sarcomas and childhood solid tumours may be suitable targets for future phase II trials. Br J Cancer, 1997, 76(2), 198 - 205 Reversion of multidrug resistance with polyalkylcyanoacrylate nanoparticles: towards a mechanism of action; de Verdiere AC et al.; Polyalkylcyanoacrylate (PACA) nanoparticles loaded with doxorubicin allowed multidrug resistance to be overcome in vitro . However, increased cytotoxicity is not always correlated with an increased level of intracellular drug . Although we have previously shown that PACA nanoparticles are not endocytosed by tumour cells, we report here that a direct interaction between nanoparticles and cells is a necessary requirement for overcoming resistance . In addition, the results showed that the degradation products of PACA (mainly polycyanoacrylic acid) in the presence of doxorubicin are able to increase both accumulation and cytotoxicity, thus suggesting the formation of a doxorubicin-polycyanoacrylic acid ion pair . It is therefore concluded that resistance is overcome as a result of both the adsorption of nanoparticles to the cell surface and increased doxorubicin diffusion by the accumulation of an ion pair at the plasma membrane. J Cancer Res Clin Oncol, 1997, 123(6), 352 - 6 P-glycoprotein expression in soft-tissue sarcomas; Nakanishi H et al.; Multidrug resistance (MDR) is an important problem in chemotherapy for neoplastic disease . In humans . MDR is mainly mediated by P-glycoprotein (P-gp) a product of the MDRI gene, which acts as a transmembrane protein pump and eliminates chemotherapeutic agents from the cells . Expression of P-gp was immunohistochemically studied by using two monoclonal antibodies, JSB-1 and C-219, on paraffin-embedded sections from 55 patients with soft-tissue sarcoma . The histological diagnosis of tumors was malignant fibrous histiocytoma in 24 cases, liposarcoma in 9, synovial sarcoma in 7, malignant neurogenic tumors in 6, leiomyosarcoma in 5, others in 4 . The histological grade was determined on the basis of criteria previously proposed by us . Out of 55 cases, 34 (62%) were positive for P-gp expression . There was a significant difference in P-gp expression between high-grade (90%) and intermediate and low-grade tumors (46%) (P < 0.005) . Tumors expressing P-gp had a less favorable prognosis than P-gp-negative tumors in the high- and intermediate-grade tumors . The current study demonstrated that the estimation of P-gp expression could be used to select appropriate therapeutic modalities. Cancer Chemother Pharmacol, 1997, 40(3), 245 - 50 Resistance to paclitaxel mediated by P-glycoprotein can be modulated by changes in the schedule of administration; Zhan Z et al.; PURPOSE: Increasing use of paclitaxel in clinical oncology has stimulated interest in its mechanisms of resistance and ways to overcome these . Studies were performed with paclitaxel to determine the role of P-glycoprotein in drug sensitivity, and the effect of schedule on relative resistance . We have previously reported that prolonged exposure to P-glycoprotein substrates decreases relative resistance in multidrug resistant cells . METHODS: Using both unselected and drug-selected cell lines, cross-resistance and cytotoxicity reversal studies using cyclosporin A were performed . In multidrug-resistant cells, cross-resistance was evaluated after 3-, 24-, and 96-h exposures to paclitaxel . RESULTS: Cross-resistance to paclitaxel in P-glycoprotein-expressing sublines was shown to be comparable to that of other drugs transported by P-glycoprotein . Sensitivity to paclitaxel could be modulated by cyclosporin A in unselected cell lines expressing P-glycoprotein and not in P-glycoprotein-negative cell lines . Resistance to paclitaxel was reduced tenfold by increasing the duration of exposure in P-glycoprotein-expressing cells . This effect was not observed in a paclitaxel-resistant cell line which does not express P-glycoprotein . CONCLUSIONS: These studies extend observations on the schedule dependence of paclitaxel cytotoxicity and the role of P-glycoprotein in mediating paclitaxel sensitivity . The schedule dependence of relative resistance suggests that infusional paclitaxel may help in overcoming P-glycoprotein-mediated resistance. Cancer Chemother Pharmacol, 1997, 40(3), 215 - 24 Multienzyme-mediated stable and transient multidrug resistance and collateral sensitivity induced by xenobiotics; Rekha GK et al.; BACKGROUND: Determinants of cellular sensitivity to anticancer drugs include enzymes that catalyze their biotransformation . Coordinated induction of some of these enzymes is known to be caused by a number of dietary constituents, environmental contaminants, pharmacological agents and other xenobiotics, e.g . 3-methylcholanthrene and catechol . Despite the potential for inducing simultaneous changes in tumor cell sensitivity to a wide range of drugs, scant attention has been paid to the impact that dietary constituents and other xenobiotics might have on the therapeutic outcome of cancer chemotherapy . PURPOSE: The aim of this investigation was to demonstrate the potential of xenobiotic-induced multienzyme-mediated stable and transient multidrug resistance/collateral sensitivity in a model system . METHODS: Human breast adenocarcinoma MCF-7/0 cells and a stably oxazaphosphorine-resistant subline thereof, MCF-7/OAP, were grown in the presence of 3-methylcholanthrene (3 microM), catechol (30 microM), or vehicle for 5 days . Spectrophotometric and spectrofluorometric assays were used to quantify catalytic activities and thus cellular levels of cytosolic class 3 aldehyde dehydrogenase, glutathione S-transferase, DT-diaphorase, UDP-glucuronosyl transferase and cytochrome P450 1A1 . A colony-forming assay was used to quantify cellular sensitivities to several anticancer drugs . RESULTS: Relative to their untreated counterparts, MCF-7/0 and MCF-7/OAP cells treated with 3-methylcholanthrene or catechol transiently expressed elevated levels of cytosolic class 3 aldehyde dehydrogenase, glutathione S-transferase, DT-diaphorase and UDP-glucuronosyl transferase, and were transiently, more resistant to mafosfamide, melphalan, and mitoxantrone, and more sensitive to EO9 . Further, MCF-7/0 and MCF-7/OAP cells treated with 3-methylcholanthrene, but not those treated with catechol, transiently expressed elevated levels of cytochrome P450 1A1 and were transiently more sensitive to ellipticine . Relative to MCF-7/0 cells, MCF-7/OAP cells stably overexpressed all but cytochrome P450 1A1 and were stably, more resistant to mafosfamide, melphalan and mitoxantrone, and more sensitive to EO9 . Inclusion of relatively specific inhibitors of, or alternative substrates for, the enzymes of interest during drug exposure negated the influence of enzyme overexpression on cellular sensitivities to these agents . Untreated, and 3-methylcholanthrene- or catechol-treated, MCF-7/0 and MCF-7/OAP cells were equisensitive to vincristine and nearly so to doxorubicin . CONCLUSIONS: Collectively, these experiments illustrate the potential for both stable and transient xenobiotic-induced multienzyme-mediated multidrug resistance/collateral sensitivity that, although also the result of a single event, is mechanistically different from, and pertains to a largely different group of anticancer agents than does, the multidrug resistance caused by cell surface multidrug transporters. Br J Cancer, 1997, 76(1), 67 - 76 Characterization of a clonal human colon adenocarcinoma line intrinsically resistant to doxorubicin; Dolfini E et al.; Intrinsic low-level resistance to anti-cancer drugs is a major problem in the treatment of gastrointestinal malignancies . To address the problem presented by intrinsically resistant tumours, we have isolated two monoclonal lines from LoVo human colon adenocarcinoma cells: LoVo/C7, which is intrinsically resistant to doxorubicin (DOX); and LoVo/C5, which shows the same resistance index for DOX as the mixed parental cell population . For comparison, we have included in the study a LoVo-resistant line selected by continuous exposure to DOX and expressing a typical multidrug resistant (MDR) phenotype . In these cell lines we have studied the expression and/or activity of a number of proteins, including P-glycoprotein 170 (P-gp), multidrug resistance-associated protein (MRP), lung resistance-related protein (LRP), glutathione (GSH)-dependent enzymes and protein kinase C (PKC) isoforms, which have been implicated in anti-cancer drug resistance . Intracellular DOX distribution has been assessed by confocal microscopy . The results of the present study indicate that resistance in LoVo/C7 cells cannot be attributed to alterations in P-gp, LRP or GSH/GSH-dependent enzyme levels . Increased expression of MRP, accompanied by alterations in the subcellular distribution of DOX, has been observed in LoVo/C7 cells; changes in PKC isoform pattern have been detected in both intrinsically and pharmacologically resistant cells. Life Sci, 1997, 61(2), 153 - 63 Effect of the P-glycoprotein inhibitor, SDZ PSC 833, on the blood and brain pharmacokinetics of colchicine; Desrayaud S et al.; The effect of the multidrug resistance-reversing agent, SDZ PSC 833, on blood and brain pharmacokinetics of a P-glycoprotein substrate, colchicine, was investigated using simultaneous blood and brain microdialysis in freely moving rats . The use of microdialysis for pharmacokinetic studies was validated by comparing the blood concentrations of colchicine obtained by microdialysis with those obtained by direct blood sampling . The rats received either SDZ PSC 833 (2.3 mg/kg i.v . bolus followed by 16.7 microg/min/kg i.v . infusion during all the experiment) and colchicine (1 mg/kg i.v . bolus followed by 12.5 microg/min/kg i.v . infusion during 2 hours) or colchicine alone (the same dosage with SDZ PSC 833 vehicle) . The SDZ PSC 833 treatment resulted in important modifications of colchicine blood pharmacokinetics: the unbound colchicine blood concentration at steady-state was enhanced from 149.6 +/- 9.9 to 333.5 +/- 81.7 ng/ml indicating a two-fold decrease in colchicine clearance . Moreover the coadministration of SDZ PSC 833 increased the brain penetration of colchicine by a factor of 10, at least . This enhancement could not be exactly assessed because the brain dialysate concentrations of control group were below the limit of detection . Nevertheless, the large increase of colchicine brain penetration is consistent with the hypothesis that SDZ PSC 833 is able to inhibit the P-glycoprotein pump present at the blood-brain barrier. Acta Haematol, 1997, 98(1), 1 - 7 mRNA expression, measured by quantitative reverse transcriptase polymerase chain reaction, of five putative drug resistance parameters, in normal and leukaemic peripheral blood and bone marrow; Lohri A et al.; Using a quantitative reverse transcriptase PCR assay, the mRNA expression of five putative drug resistance-related genes were assessed in normal peripheral (n = 14) and bone marrow (n = 4) mononuclear cells from healthy donors and patients with acute myeloid leukaemia (n = 11) . The mRNA levels of MDR1, the multidrug resistance-associated protein and glutathione-S-transferase pi were equally expressed in both compartments . Bcl-2 mRNA was slightly higher in the leukaemic marrow samples . However, topoisomerase II alpha mRNA levels were found to be much higher in normal and leukaemic marrow cells compared to peripheral blood (p < 0.01), which may, in part, reflect the different proliferation pattern of the mononuclear cells in the two compartments . Such findings could be important for researchers using bulk assays in a mix of samples from peripheral blood or bone marrow to investigate prognostic factors in patients with leukaemia. Crit Rev Biotechnol, 1997, 17(2), 171 - 83 Changing the transport of a cell; Prasad R; The review deals with some of the transport functions of different systems that have been implicated with several pathological disorders . Membrane transport role in parasitic diseases and metal resistance is discussed as a few selected examples . Among various limitations that are encountered in recombinant technology and in heterologous expression of proteins, transport functions of the host organisms cannot be ignored . Recently, membrane transport has acquired a new emerging role in multidrug resistance . Several membrane transporters, particularly ATP binding cassette (ABC) proteins that are involved in drug resistance, have been identified throughout the evolutionary scale . The review briefly emphasizes that membranes are not only important as structural elements but are also adopted to perform diverse functions. Cancer Chemother Pharmacol, 1997, 40(2), 150 - 8 Probenecid reverses multidrug resistance in multidrug resistance-associated protein-overexpressing HL60/AR and H69/AR cells but not in P-glycoprotein-overexpressing HL60/Tax and P388/ADR cells; Gollapudi S et al.; PURPOSE: To determine whether probenecid, an inhibitor of organic anion transport, is able to reverse multidrug resistance (MDR) through modulation of the drug transport function of MDR-associated protein (MRP) and P-glycoprotein (P-gP) . METHODS: Two MRP-overexpressing cell lines (HL60/AR and H69/AR) and two P-gP-overexpressing cell lines (HL60/Tax and P388/ADR) were cultured with different concentrations of daunorubicin (DNR) or vincristine (VCR) in the presence or absence of various concentrations of probenecid (0.01-10 mM) . Drug sensitivity was determined using an MTT assay . DNR accumulation and subcellular distribution were determined by flow cytometry and confocal microscopy respectively . VCR accumulation was determined by scintillation spectrometry . RESULTS: Probenecid, in a concentration-dependent manner, reversed resistance to DNR and VCR in HL60/AR and H69/AR tumor cell lines . This effect of probenecid on MDR was associated with an increased accumulation of DNR and VCR and correction of the altered subcellular distribution of DNR . The concentrations of probenecid that reversed MDR are clinically achievable in vivo . In contrast, probenecid did not reverse MDR in either HL60/Tax or P388/ADR tumor cell lines that overexpress P-gP . CONCLUSION: These results suggest that probenecid is an effective chemosensitizer of MRP-associated MDR tumor cells and is a potential candidate for clinical use to reverse MDR. J Cancer Res Clin Oncol, 1997, 123(4), 237 - 9 Expression of multidrug resistance-associated protein gene in Ewing's sarcoma and malignant peripheral neuroectodermal tumor of bone; Oda Y et al.; The expression of multidrug resistance-associated protein (MRP) mRNA was examined in ten samples of Ewing's sarcoma of bone (ES) and in one nude mice transplantable ES and two malignant peripheral neuroectodermal tumor (MPNT) cell lines using an RT-PCR assay . MRP mRNA expression was recognized in eight of the ten clinical specimen and in all three cell lines . On the other hand, the expression of multidrug resistance gene (MDR1) was demonstrated in three of the ten clinical samples and all three cell lines . Our results may contribute to elucidation of the mechanism of anti-cancer-drug resistance in this tumor. J Cancer Res Clin Oncol, 1997, 123(4), 201 - 10 Inhibition of protein kinase C in multidrug-resistant cells by modulators of multidrug resistance; Hu YP et al.; We have evaluated the protein kinase C (PKC) activity in two series of cultured cell lines presenting the multidrug-resistance (MDR) phenotype and in the corresponding wild-type cells: the human KB 3.1, KB A1 and KB 8.5 cell lines, and the rat C6, C6 0.5 and C6 1V cell lines . We have observed an increase in PKC activity in the MDR cell lines of the KB cell lineage, proportional to their degree of resistance to doxorubicin . In contrast, the MDR cell lines of the C6 cell lineage presented no change (C6 0.5) or even decrease (C6 1V) in PKC activity; the basal level of PKC activity in C6 cells was, however, 50-fold higher than in KB 3.1 cells . We have tested, in these lines, the effect of four modulators of MDR: verapamil, cyclosporin A, quinine and S-9788, on doxorubicin acytotoxicity and on PKC activity . We observed that cyclosporin A and S-9788, which were the most active on MDR reversal, were able to inhibit PKC activity in the KB resistant lines as well as in all C6 lines, whereas verapamil and quinine had only marginal effects on PKC activity . The distribution of PKC isoenzymes was studied by Western blots . The PKC alpha, gamma and delta isoforms were increased in the KB resistant lines as compared to wild-type cells, which could account for the increase PKC activity we observed . In contrast, PKC alpha and gamma were decreased in C6 1V cells, as expected from the results obtained for total PKC activity, but we also noticed an important decrease in PKC delta in the C6 0.5 line . Our results suggest that an increase in PKC activity is not an absolute requirement for expression of MDR, provided that the basal level be high enough; and that some modulators may act on MDR, not only through direct P-glycoprotein interaction, but also through P-glycoprotein phosphorylation or expression . The distribution of PKC isoenzymes revealed that the modifications encountered between sensitive and resistant cells mainly concerned alpha, gamma and delta isoenzymes of PKC. Oncol Res, 1997, 9(2), 61 - 9 Potentiation of the antitumor activity by a novel quinoline compound, MS-209, in multidrug-resistant solid tumor cell lines; Nakanishi O et al.; A novel quinoline compound, MS-209, was examined for its ability to reverse multidrug resistance (MDR) in several murine and human MDR solid tumor cell lines both in vitro and in vivo . MS-209 strongly reversed drug resistance to adriamycin (ADM) and vincristine (VCR) in acquired MDR tumor cell lines, 2780AD and KB-C1 . In addition, MS-209 enhanced the cytotoxic effect of ADM and VCR on various human and murine cell lines . Particularly in 4-1St cells, which are extremely resistant to ADM and VCR, MS-209 at a concentration of 3 microM enhanced the cytotoxicity of ADM and VCR, 88- and 350-fold, respectively . MS-209 administered orally, together with ADM, enhanced the antitumor activity of ADM on Colon 26 and 4-1St tumors implanted subcutaneously (SC) in mice; the antitumor effect of ADM plus MS-209 was higher than that of ADM alone at the maximum tolerated dose (MTD) . Furthermore, the coadministration schedules of MS-209 to attain the highest potentiation of ADM activity were examined using Colon 26 tumors . The maximum antitumor activity was obtained when MS-209 was administered on the same day as ADM . MS-209 administered a day before the ADM injection exhibited no potentiation effect, whereas MS-209 administered a day after the ADM injection showed a moderate effect . The effect of MS-209 was weaker when administered in a fractionated manner than when administered as a single dose . The results presented in this article suggest that MS-209 is an effective agent to overcome MDR in cancer chemotherapy. Br J Cancer, 1997, 75(9), 1330 - 5 Co-ordinate loss of protein kinase C and multidrug resistance gene expression in revertant MCF-7/Adr breast carcinoma cells; Budworth J et al.; The aim of this study was to investigate the link between protein kinase C (PKC) and multidrug resistance (mdr) phenotype . The expression of both was studied in doxorubicin-resistant MCF-7/Adr cells as they reverted to the wild-type phenotype when cultured in the absence of drug . The following parameters were measured in cells 4, 10, 15, 20 and 24 weeks after removal of doxorubicin; (1) sensitivity of the cells towards doxorubicin; (2) levels of P-glycoprotein (P-gp) and MDR1 mRNA; (3) levels and cellular localization of PKC isoenzyme proteins alpha, theta and epsilon; and (4) gene copy number of PKC-alpha and MDR1 genes . Cells lost their resistance gradually with time, so that by week 24 they had almost completely regained the drug sensitivity seen in wild-type MCF-7 cells . P-gp levels measured by Western blot mirrored the change in doxorubicin sensitivity . By week 20, P-gp had decreased to 18% of P-gp protein levels at the outset, and P-gp was not detectable at week 24 . Similarly, MDR1 mRNA levels had disappeared by week 24 . MCF-7/Adr cells expressed more PKCs-alpha and -theta than wild-type cells and possessed a different cellular localization of PKC-epsilon . The expression and distribution pattern of these PKCs did not change for up to 20 weeks, but reverted back to that seen in wild-type cells by week 24 . MDR1 gene amplification remained unchanged until week 20, but then was lost precipitously between weeks 20 and 24 . The PKC-alpha gene was not amplified in MCF-7/Adr cells . The results suggest that MCF-7/Adr cells lose MDR1 gene expression and PKC activity in a co-ordinate fashion, consistent with the existence of a mechanistic link between MDR1 and certain PKC isoenzymes. Anticancer Drugs, 1997 Jan, 8(1), 26 - 33 Protein kinase C: a worthwhile target for anticancer drugs? Caponigro F, French RC, Kaye SB. Protein kinase C (PKC) is an enzyme family with serine/threonine kinase function which is involved in the transduction of signals for cell proliferation and differentiation . The important role played in processes relevant to neoplastic transformation, carcinogenesis and tumor cell invasion renders PKC a potentially suitable target for anticancer therapy . Bryostatin 1, a macrocyclic lactone isolated from Bugula nerutina, is a partial PKC agonist, and has shown potent antineoplastic properties in vitro and in vivo . Staurosporine, an alkaloid isolated from microbial sources, is ine of the most potent PKC inhibitors and has shown high antiproliferative activity in vitro, but poor selectivity . Staurosporine analogs have thus been synthesize with the aim of obtaining more selective PKC inhibition; among these, CGP 41251 has shown reduced PKC inhibitory activity, but a higher degree of selectivity when assayed for inhibition of different kinases . Several studies indicate a role for PKC in the regulation of the multidrug resistance (MDR) phenotype, since several PKC inhibitors are able to partially reverse MDR and inhibit P-glycoprotein (Pgp) phosphorylation . The MDR phenotype is also associated with variation in PKC isoenzyme content, in particular with PKC-alpha overexpression . While adequate PKC modulation might offer an attractive concept to modulate MDR, other potential mechanisms of PKC interaction with anticancer drugs exist and have been documented, such as the enhancement of chemotherapy-induced apoptosis by safingol, a specific PKC inhibitor . Three phase I clinical trials with bryostatin have been completed so far and have shown that myalgia is the dose-limiting toxicity, while some antitumor activity is evident . Safingol is presently undergoing a phase I clinical trial in combination with doxorubicin . While no definitive data are presently available, it appears that safingol plasma levels approach those associated with chemopotentiation in animals and no pharmacokinetic interaction between the two drugs exists . Drugs targeting PKC are well work considering for clinical trials, particularly for their potential as modulators of currently available cytotoxic agents. Anticancer Drugs, 1997 Jan, 8(1), 17 - 25 The role of multidrug resistance-associated protein (MRP) expression in multidrug resistance; Kavallaris M; Multidrug resistance (MDR) is a major hindrance to the successful treatment of neoplastic disease . The development of resistance to multiple chemotherapeutic drugs is a complex phenomenon which has been described in both tumor cell lines and human cancers . To date, two mechanisms associated with overexpression of membrane glycoproteins that function as energy-dependent efflux pumps to reduce intracellular drug levels have been identified for MDR . The first described was the product of the MDR1 gene, P-glycoprotein . The second mechanism is mediated by overexpression of the multidrug resistance-associated protein (MRP) . While these proteins both belong to the ATP-binding cassette superfamily of transporters, they are only distantly related . Despite this low homology, they mediate resistance to a similar range of chemotherapeutic drugs . While P-glycoprotein has been well described in the literature, much less is known about the recently identified MRP . This review gives an overview of the characteristics of MRP at both the phenotypic and genotypic levels, and discusses its possible relevance in drug-refractory cancer. Arch Toxicol, 1997, 71(5), 336 - 9 Lack of biliary excretion of Cd linked to an inherent defect of the canalicular isoform of multidrug resistance protein (cMrp) does not abnormally stimulate accumulation of Cd in the Eisai hyperbilirubinemic (EHB) rat liver; Sugawara N et al.; A new mutant, the Eisai hyperbilirubinemic (EHB) rat, shows no inherent expression of the canalicular isoform of the multidrug resistance protein (cMrp) in the liver . It has defective biliary secretion of organic anions such as bilirubin glucuronides, bromosulfophthalein (BSP), cysteinyl leukotrienes, glutathione (GSH) and bile acid sulfate and glucuronides . When rats were injected intravenously with CdCl2, biliary excretion of Cd over 30 min was 0.28% and 0.004% of the total dose in Sprague-Dawley (SD) and EHB rats, respectively . Six SD rats and five EHB rats were fed a diet containing Cd . Bile Cd was detected at the level of 2 ng/20 min in SD rats, but not in EHB rats . There was no significant difference of hepatic Cd concentration between SD and EHB rats . Furthermore, there were no significant differences of renal and intestinal Cd, and hepatic and renal metallothionein (MT) concentrations between the SD and EHB groups . Biliary excretion of reduced-GSH for 20 min was 1.3 +/- 0.3 mg and 3.6 +/- 0.9 micrograms in SD and EHB rats, respectively . Our results suggest that hepatobiliary excretion of exogenous Cd is mediated mainly via carrier transport, including a cMrp or GSH carrier, but that the lack of the transport pathway does not contribute to abnormal accumulation of Cd in the liver. Cancer Chemother Pharmacol, 1997, 40(1), 65 - 71 Characterization of cellular accumulation and toxicity of illudin S in sensitive and nonsensitive tumor cells; Kelner MJ et al.; Illudins are novel low molecular weight natural products cytotoxic to human tumor cells in vitro . Illudin-derived analogs are effective against experimental human cancers nonresponsive to conventional anticancer agents . It is not known why some illudin analogs are more efficacious in vitro and in vivo than other analogs . Therefore, the in vitro cytotoxicity of the parent compound illudin S towards tumor cells was characterized using radiolabeled drug . Two cell lines sensitive at nanomolar concentrations using only a 15-min exposure period displayed a saturable, energy-dependent accumulation of illudins with relatively low K(m) and high Vmax values . A nonsensitive cell line, requiring millimolar concentrations to achieve in vitro toxicity, showed minimal illudin uptake with higher K(m) and lower Vmax values . No release of radioactivity could be demonstrated from tumor cells, indicating that there was no efflux of illudin S (or metabolites) from these cells . The number of intracellular illudin S molecules required to kill 50% of cells of different tumor cell lines varied from 78000 to 1114000 molecules per cell and was correlated with the 2-h IC50 value determined using a colony-forming assay . Illudin S was cytotoxic to a variety of multidrug-resistant tumor cell lines regardless of whether resistance was mediated by gp170/mdrl, gp180/MRP, GSHTR-pi, topoisomerase I, topoisomerase II, increased DNA repair capacity, or alterations in intracellular thiol content . Information obtained in this study could be used to design clinical phase I trials and to develop analogs with improved therapeutic indexes. Eur Urol, 1997, 31(3), 365 - 70 Enhanced in vitro cytotoxicity of idarubicin compared to epirubicin and doxorubicin in rat prostate carcinoma cells; Siegsmund MJ et al.; OBJECTIVE: We evaluated the cytotoxic activity of the three anthracyclines, doxorubicin, epirubicin and idarubicin, in different sublines of the Dunning rat prostate carcinoma as well as in multidrug-resistant KB cells, expressing a high amount of the human multidrug resistance gene product, P glycoprotein . METHODS: The effectiveness of the three anthracyclines was tested in vitro in the Dunning rat prostate carcinoma sublines G, AT.1, AT.3.1, MatLu, and MatLyLu, as well as in multidrug-resistant KB cells, using an MTT assay . RESULTS: All drugs were clearly more effective in the androgen-sensitive Dunning rat prostate carcinoma subline G than in the androgen-independent growing sublines AT.1, AT.3.1, MatLu, and MatLyLu . Idarubicin was much more effective than doxorubicin or epirubicin . To further elucidate the mechanism of action of idarubicin as compared with doxorubicin and epirubicin, we tested the cytotoxicity of these anthracyclines in highly multidrug-resistant KB-V1 cells, which express high amounts of P glycoprotein, as well as in the drug-sensitive parental KB-3-1 cells . KB-V1 cells proved to be highly resistant to doxorubicin and epirubicin with IC50 values of 2,300 and 1,000 ng/ml, respectively . Idarubicin, however, was about 57.5-fold and 25-fold more active, respectively, suggesting, that it is able to overcome P-glycoprotein-mediated multidrug resistance . CONCLUSION: The strong in vitro effectiveness of idarubicin in androgen-insensitive prostate carcinoma cells suggests that this drug might be useful in the treatment of hormone-refractory prostate carcinoma. Free Radic Biol Med, 1997, 22(7), 1283 - 8 Artemisinin enhances heme-catalysed oxidation of lipid membranes; Berman PA et al.; Artemisinin, a sesquiterpene endoperoxide derived from a traditional Chinese herbal remedy for fevers, is a promising new antimalarial drug, particularly useful against multidrug resistant strains of P . falciparum . Despite widespread clinical use, its mode of action remains uncertain . We investigated whether its antimalarial properties could be explained by an ability to enhance the redox activity of heme, formed in the parasite food vacuole from digested hemoglobin . Artemisinin caused a sustained threefold increase, followed by a gradual decline, in the peroxidase activity of heme . It also enhanced the ability of heme to oxidize membrane lipids about sixfold . An unexpected finding was the potentiation of heme-catalysed membrane lipid oxidation by Vitamin E . The changes in redox-catalytic activity induced by artemisinin were paralleled by major changes in the absorption spectrum of heme, culminating in loss of the Soret band . We propose a model in which artemisinin binds irreversibly to heme in the parasite food vacuole, preventing its polymerization to chemically inert hemozoin, and promoting heme-catalysed oxidation of the vacuolar membrane by molecular oxygen, which leads, ultimately, to vacuole rupture and parasite autodigestion. Stem Cells, 1997, 15(2), 104 - 11 In vivo drug-selectable genes: a new concept in gene therapy; Licht T et al.; Chemoresistance genes, initially considered to be a major impediment to the successful treatment of cancer, may become useful tools for gene therapy of cancer and of genetically determined disorders . Various target cells are rendered resistant to anticancer drugs by transfer of chemoresistance genes encoding P-glycoprotein, the multidrug resistance-associated protein-transporter, dihydrofolate reductase, glutathione-S-transferase, O6-alkylguanine DNA alkyltransferase, or aldehyde reductase . These genes can be used for selection in vivo because of the pharmacology and pharmacokinetics of their substrates . In contrast, several other selectable marker genes conferring resistance to substrates like neomycin or hygromycin can only be utilized in tissue culture . Possible applications for chemoresistance genes include protection of bone marrow and other organs from adverse effects caused by the toxicity of chemotherapy . Strategies have also been developed to introduce and overexpress nonselectable genes in target cells by cotransduction with chemoresistance genes . Thereby expression of both transgenes can be increased following selection with drugs . Moreover, treatment with chemotherapeutic agents should restore transgene expression when or if expression levels decrease after several weeks or months . This approach may improve the efficacy of somatic gene therapy of hematopoietic disorders which is hampered by low or unstable gene expression in progenitor cells . In this article we review preclinical studies in tissue culture and animal models, and ongoing clinical trials on transfer of chemoresistance genes to hematopoietic precursor cells of cancer patients. Urol Res, 1997, 25(1), 35 - 41 Multidrug resistance in androgen-independent growing rat prostate carcinoma cells is mediated by P-glycoprotein; Siegsmund MJ et al.; Prostate carcinomas are in general resistant against virtually all cytotoxic drugs . Up to now it has not been thoroughly evaluated whether specific resistance factors, such as the expression of the MDR1 gene, play a role in this multi-agent resistance and whether there is a link between drug resistance and hormone-independent growth . We investigated the resistance patterns of a hormone-sensitive and four hormone-independent Dunning rat carcinoma sublines against four drugs which are substrates of P-glycoprotein (vinblastine, taxol, doxorubicin, and etoposide) and two agents (methotrexate and cis-platinum) which are not transported by this efflux pump . All hormone-insensitive sublines, AT.1, AT . 3.1., MatLu and Mat LyLu, continuously showed a clearly enhanced resistance (3- to 26-fold) against the P-glycoprotein substrates, compared to the hormone-sensitive subline G . Only two of the androgen-independent sublines displayed enhanced resistance against methotrexate, whereas all of them were more sensitive against cisplatin than the androgen-sensitive G cells . By addition of verapamil the resistance against vinblastine (9- to 10-fold) and taxol (6.7- to 26.7-fold) in the hormone-insensitive cells could be almost totally reversed . Furthermore, the fluorescent P-glycoprotein substrate rhodamine-123 was effectively pumped out of the four tested hormone-independent cell lines, whereas the hormone-sensitive G cells were unable to extrude the dye . By reverse transcriptase polymerase chain reaction (RT-PCR) with primers specific for the rat mdr1b gene, the homologue to the human MDR1 gene, we could easily detect mdr1b expression in the androgen independent cell lines, but not in the G cells . Our results suggest that the product of the rat mdr1b gene is involved in the multidrug resistance of androgen-independent Dunning prostate carcinoma cells. Anticancer Res, 1997 Jan-Feb, 17(1A), 481 - 6 Inhibition of the transport function of membrane proteins by some substituted phenothiazines in E . coli and multidrug resistant tumor cells; Molnar J et al.; Efflux-pumps mediated by P-glycoprotein increase the level of resistance to antibiotics in bacteria and to cytostatics in tumor cells due to decreased drug accumulation, and are also involved in the operation of blood brain barrier . Different compounds are able to enhance drug retention in the cells by inhibiting the efflux-pump mechanism of multidrug resistant (mdr) cancer cells and bacteria . The effects of substituted chlorpromazines were studied on a hemolysin producing and antibiotic resistant plasmid carrying E coli, and rhodamine uptake of multidrug resistant (mdr 1 gene expressing) mouse lymphoma cells . Hemolysin transporter protein encoding plasmids were eliminated from E . coli by a representative phenothiazine namely promethazine . Minimal inhibitory concentrations of tetracyclin and promethazine were lower for plasmidless bacteria as compared to the parent, plasmid carrying strains . The antibiotic resistance plasmid was cured of the R-plasmid of E . coli JE 2571, however, the ring substituted derivatives were less effective then parent compounds . The effect of some substituted phenothiazines on P-glycoprotein efflux-pump of mouse lymphoma cells were studied . The majority of ring substituted derivatives reversed the mdr of tumor cells . The 3,7,8-trihydroxy- and 7,8-dihydroxy derivatives of chlorpromazine were effective as P-glycoprotein blockers, however, 7,8-diacetoxy-, 7,8dimetoxy-, 7-semicarbazone-, and 5-oxo-chlorpromazine derivatives had only moderate effect . A tomato lectin, specific for blood brain capillary endothelium was able to modify the activity of P-glycoprotein in tumor cells . Phenothiazine and tomato lectin had some antagonism in tumor cells . Our results suggest that the inhibition of P-glycoprotein function in murine tumor cells and inhibition of transporter protein in E . coli bacteria may depend on pi-electron superdelocalizibility and electrophile binding of the compounds to the transporter proteins . The intracellular accumulation of antibiotics or chemotherapeutics increased as a consequence of decreased drug efflux in both bacterial and tumor cell systems . The inhibition of the drug effux-pump is the same for all individual cells of the population . These results can be realized by combination chemotherapy, however, antiplasmid effect itself cannot be exploited in this respect because the resistance was reversed in a part of the population only . The similarity with mdr P-glycoprotein in tumor cells and brain capillary endothels provides a good model for molecules opening the blood brain barrier. Anticancer Res, 1997 Jan-Feb, 17(1A), 129 - 33 The reversal of multidrug resistance in multicellular tumor spheroids by SDZ PSC 833; Ehrlich PH et al.; Multidrug resistance (MDR) is a major impediment to the effective treatment of cancer . We have used multicellular tumor spheroids (MTS) as a model to investigate whether MDR can be reversed in a three dimensional structure . MTS are tightly associated aggregates of tumor cells that exhibit many of the properties of solid tumors . A human MDR breast carcinoma cell line was selected by exposure to taxol under monolayer conditions . The sensitive (parental) and drug-resistant phenotypes were retained when the cells were grown as MTS . Thus, the three dimensional conditions in this novel model system did not affect the MDR phenotype . SDZ PSC 833 is an efficient MDR reversing agent as determined under monolayer conditions and is currently being evaluated in clinical trials . Resistance to taxol and doxorubicin of the MDR cells grown as MTS was almost completely reversed by SDZ PSC 833 . Our results suggest that SDZ PSC 833 has the potential to reverse the MDR phenotype in solid tumors. Anticancer Res, 1997 Jan-Feb, 17(1B), 721 - 4 The clinical role of MDR1 gene expression in human lung cancer; Oka M et al.; Human P-glycoprotein (Pgp) encoded by the MDR1 gene confers multidrug resistance to cancer cells . The clinical role of MDR1/Pgp in lung cancer is not fully understood . A total of 87 lung cancer surgical tissue samples, including previously untreated 84 non-small-cell (NSCLC) and three small-cell lung carcinoma (SCLC), were analyzed for levels of MDR1 mRNA determined by Northern blotting and compared with MDR1-positive cell lines . Fifteen percent (13/87) of the tumors were positive for the MDR1 gene, but the level was low in all samples except in one adenocarcinoma which expressed a high level of MDR1 . The gene expression in these tumors did not relate with any pathologic factors such as histologic type, pathologic stage and tumor size . The SCLC and only one of the 14 MDR1-negative NSCLC responded to adjuvant chemotherapy after surgery . The present results indicate that the MDR1 gene is not associated in NSCLC with tumor progression and drug resistance. Int Rev Cytol, 1997, 171, 121 - 65 Biophysical aspects of P-glycoprotein-mediated multidrug resistance; Wadkins RM et al.; In the 45 years since Burchenal's observation of chemotherapeutic drug resistance in tumor cells, many investigators have studied the molecular basis of tumor drug resistance and the phenomenon of tumor multidrug resistance (tumor MDR) . Examples of MDR in microorganisms have also become topics of intensive study (e.g., Plasmodium falciparum MDR and various types of bacterial MDR) and these emerging fields have, in some cases, borrowed language, techniques, and theories from the tumor MDR field . Serendipitously, the cloning of MDR genes overexpressed in MDR tumor cells has led to elucidation of a large family of membrane proteins {the ATP-binding cassette (ABC) proteins}, an important subset of which confer drug resistance in many different cells and microorganisms . In trying to decipher how ABC proteins confer various forms of drug resistance, studies on the structure and function of both murine and human MDR1 protein (also called P-glycoprotein or P-gp) have often led the way . Although various theories of P-gp function have become popular, there is still no precise molecular-level description for how P-gp overexpression lowers intracellular accumulation of chemotherapeutic drugs . In recent years, controversy has developed over whether the protein protects cells by translocating drugs directly (as some type of drug pump) or indirectly (through modulating biophysical parameters of the cell) . In this ongoing debate over P-gp function, detailed consideration of biophysical issues is critical but has often been neglected in considering cell biological and pharmacological issues . In particular, P-gp overexpression also changes plasma membrane electrical potential (delta psi zero) and intracellular pH (pHi), and these changes will greatly affect the cellular flux of a large number of compounds to which P-gp overexpression confers resistance . In this chapter, we highlight these biophysical issues and describe how delta psi zero and pHi may in fact be responsible for many MDR-related phenomena that have often been hypothesized to be due to direct drug translocation (e.g., drug pumping) by P-gp. Am J Trop Med Hyg, 1997 Jan, 56(1), 24 - 6 Initial screening for antituberculous drug resistance at an inpatient facility in Leon, Nicaragua; de la Hoz RE et al.; Antituberculous (anti-TB) drug resistance has become a major tuberculosis control issue in the United States, where this situation has closely paralleled the current acquired immunodeficiency syndrome epidemic associated with human immunodeficiency virus type-1 (HIV-1) infections . In less developed countries, especially those like Nicaragua with an apparently low prevalence of known HIV-1 infections, less is known about the epidemiology of antituberculous drug resistance . To understand the potential extent of this problem in Nicaragua, we conducted a cross-sectional prevalence study at Nicaragua's only inpatient tuberculosis treatment facility, located in Leon, Nicaragua . A radiometric method was used during recovery, purification, and drug susceptibility testing of clinical Mycobacterium tuberculosis isolates . Resistance to at least one of the major anti-TB medications was found in 15 (40.5%) of 37 sputum isolates, of which seven (19%) were resistant to either isoniazid alone, or to isoniazid plus another agent other than rifampin . Five were resistant to at least isoniazid and rifampin (i.e., 13.5% demonstrated multidrug resistance) . Two isolates were resistant to pyrazinamide alone, and one was resistant to streptomycin alone . These initial results suggest that anti-TB drug resistance is a defined problem for tuberculosis control programs in Nicaragua, a problem that is largely related to individual noncompliance, lack of extensive drug susceptibility testing facilities, and a general unavailability of expensive anti-TB medications for re-treatment . Ongoing surveillance for drug resistance, using the methodology presented here, might assist Nicaraguan public health officials in their tuberculosis control programs. Br J Cancer, 1997, 75(6), 884 - 91 Synergistic antiproliferative activity of tamoxifen and docetaxel on three oestrogen receptor-negative cancer cell lines is mediated by the induction of apoptosis; Ferlini C et al.; The taxanes are a promising family of anti-tumour drugs that block cell cycle replication by interfering with the microtubule network . The clinical use of these drugs involves some problems related to their low solubility and occurrence of resistance, which is mainly dependent on the multidrug-resistant (MDR) phenotype . To investigate the possible interaction between docetaxel and tamoxifen (TAM), three oestrogen receptor-negative cancer cell lines, MDR- MDA-MB 231, MDR + CEM-VBLr and MCF-7 ADRr, were used . In all three cell lines, the combination of docetaxel and TAM was more effective in terms of growth inhibition than single drug exposure . Isobolic analysis confirmed the presence of synergism in all cell lines when docetaxel was used at 0.2 microM and TAM at a dose equal to or higher than 1 microM . Flow cytometric DNA analysis performed on the three cell lines showed that TAM was able to increase the G2/M blocking activity of docetaxel . This blocking activity was followed by an increased flow cytometric DNA fragmentation suggestive of the presence of apoptosis, which was confirmed by DNA gel fragmentation and morphological analysis . While an antagonistic effect on P-glycoprotein (P-gp) activity may contribute to the synergistic effect of tamoxifen and docetaxel on CEM-VBLr and MCF-7 ADRr, other mechanisms must be involved, as the synergistic effect is also apparent with a P-gp-negative cell line. Br J Cancer, 1997, 75(6), 869 - 77 In vitro cross-resistance and collateral sensitivity in seven resistant small-cell lung cancer cell lines: preclinical identification of suitable drug partners to taxotere, taxol, topotecan and gemcitabin; Jensen PB et al.; The acquisition of drug-resistant tumour cells is the main problem in the medical treatment of a range of malignant diseases . In recent years, three new classes of anti-cancer agents, each with a novel mechanism of action, have been brought forward to clinical trials . These are the topoisomerase I (topo I) poisons topotecan and irinotecan, which are both camptothecin derivatives, the taxane tubulin stabilizers taxol and taxotere and, finally, the antimetabolite gemcitabin, which is active in solid tumours . The process of optimizing their use in a combination with established agents is very complex, with numerous possible drug and schedule regimens . We describe here how a broad panel of drug-resistant small-cell lung cancer (SCLC) cell lines can be used as a model of tumour heterogeneity to aid in the selection of non-cross-resistant regimens . We have selected low-fold (3-10x) drug-resistant sublines from a classic (NCI-H69) and a variant (OC-NYH) SCLC cell line . The resistant cell lines include two sublines with different phenotypes towards alkylating agents (H69/BCNU and NYH/CIS), two sublines with different phenotypes against topo I poisons (NYH/CAM and NYH/TPT) and three multidrug resistant (MDR) sublines (H69/DAU, NYH/VM, and H69/VP) with combinations of mdr1 and MRP overexpression as well as topoisomerase II (topo II) down-regulation or mutation . Sensitivity to 20 established and new agents was measured in a standardized clonogenic assay . Resistance was highly drug specific . Thus, none of the cell lines was resistant to all drugs . In fact, all resistant cell lines exhibited patterns of collateral sensitivity to various different classes of drugs . The most intriguing pattern was collateral sensitivity to gemcitabin in two cell lines and to ara-C in five drug-resistant cell lines, i.e . in all lines except the lines resistant to topo I poisons . Next, all sensitivity patterns in the nine cell lines were compared by correlation analysis . A high correlation coefficient (CC) for a given pair of compounds indicates a similar pattern in response in the set of cell lines . Such data corroborate the view that there is cross-resistance among the drugs . A numerically low coefficient indicates that the two drugs are acting in different ways, suggesting a lack of cross-resistance between the drugs, and a negative correlation coefficient implies that two drugs exhibit collateral sensitivity . The most negative CCs (%) to the new drug leads were: taxotere-carmustine (BCNU) (-75), taxol-cisplatin (-58), ara-C-taxol (-25), gemcitabin-doxorubicin (-32), camptotecin-VM26 (-41) and topotecan-VP16 (-17) . The most negative correlations to the clinically important agent VP-16 were: cisplatin (-70); BCNU (-68); camptothecin (-38); bleomycin (-33), gemcitabin (-32); ara-C (-21); topotecan (-17); melphalan (-3); and to the other main drug in SCLC treatment cisplatin were: doxorubicin (-70); VP-16 (-70); VM-26 (-69); mAMSA (-64); taxotere (-58); taxol (-58) . Taxol and taxotere were highly correlated (cross-resistant) to VP-16 (0.76 and 0.81 respectively) and inversely correlated to cisplatin (both -0.58) . Similarly, camptothecin and topotecan were correlated to cisplatin but inversely correlated to VP-16 and other topo II poisons . From the sensitivity data, we conclude that collateral sensitivity and lack of cross-resistance favours a cisplatin-taxane or topo I-topo II poison combination, whereas patterns of cross-resistance suggest that epipodophyllotoxin-taxane or topo I poison-cisplatin combinations may be disadvantageous. Br J Cancer, 1997, 75(6), 816 - 21 Response to ICRF-159 in cell lines resistant to cleavable complex-forming topoisomerase II inhibitors; Davies SL et al.; We have studied the relationship between expression of genes implicated in mediating resistance to cleavable complex-forming topoisomerase II (topo II) inhibitors and cellular sensitivity to ICRF-159, a 'catalytic' inhibitor of topo II . Overexpression of the membrane transporters, P-glycoprotein and multidrug resistance-related protein (MRP), or down-regulation of topo IIalpha and/or -beta, did not confer ICRF-159 resistance . Indeed, marked topo IIalpha down-regulation appeared to be associated with collateral sensitivity to ICRF-159 . Our results indicate that the resistance mechanisms that pertain to cleavable complex-forming topo II inhibitors and ICRF-159 are distinct . The evidence presented here suggests that topo IIalpha, not topo IIbeta, is more likely to be the major in vivo target for ICRF-159. Br J Cancer, 1997, 75(6), 810 - 5 Indomethacin-mediated reversal of multidrug resistance and drug efflux in human and murine cell lines overexpressing MRP, but not P-glycoprotein; Draper MP et al.; Decreased accumulation of the fluorescent dye BCECF {2', 7'-bis-(2-carboxyethyl)-5-(6)- carboxyfluorescein} characterized murine and human multidrug-resistant cell lines overexpressing the multidrug resistance protein (MRP) . Indomethacin (10 microM), a known cyclo-oxygenase and glutathione-S-transferase inhibitor as well as a modulator of anion transport, increased accumulation and blocked efflux of BCECF in MRP-expressing murine and human cells . The drug did not affect P-glycoprotein (P-gp)-mediated export of rhodamine 123 . The indomethacin effect on BCECF efflux was not reversed by the addition of exogenous prostaglandins, suggesting that the drug acts by a mechanism other than decreasing prostaglandin synthesis . Indomethacin also increased multidrug susceptibility of both murine and human cell lines overexpressing MRP, but not those displaying P-gp-associated resistance . In addition, indomethacin modulated the decreased vincristine accumulation in cells expressing MRP, but not in those expressing P-gp . These data suggest that indomethacin is a specific inhibitor of MRP, possibly functioning by inhibition of glutathione-S-transferase or, alternatively, by direct competition with the drug at the transport site. Eur J Radiol, 1997 Jan, 24(1), 2 - 10 Scintigraphic imaging of breast tumors; Maublant J; Technetium-99m-sestamibi scintigraphy has recently emerged as a new procedure for the imaging of malignant breast tumors . A large clinical experience has now been collected and this article reviews the main published results . The major drawback of the procedure appears to be its low sensitivity in detecting lesions smaller than 1 cm . The biological background underlying the tracer accumulation is also described . The stimulating potent applications of this functional imaging technique to non-invasively explore the development, and possibly the reversal, of a multidrug resistance under chemotherapy are discussed . The data related to the use of the positron emitter fluor-18-labeled fluorodeoxyglucose (FDG), a very promising agent for imaging breast as well as other solid tumors, are also reviewed . This situation of specific agents, still under development and such as labeled receptor ligands, is examined. Cancer Chemother Pharmacol, 1997, 39(5), 452 - 4 Superiority of cyclosporin A over PSC-833 in enhancement of VP-16 efficacy in murine tumors in vivo; Slater LM et al.; PSC-833, a non immunosuppressive analogue of cyclosporin A, is an effective modulator of the multidrug-resistant tumor phenotype . Since both PSC-833 and cyclosporin A also enhance the cytotoxicity of VP-16 against drug sensitive L1210 leukemia cells in vitro we compared these agents as modulators of VP-16 efficacy in vivo . Compared to VP-16 treatment alone both PSC-833 and cyclosporin A significantly altered the survival of L1210 leukemia-bearing BDF/1 mice and Lewis lung carcinoma-bearing C57/B1 mice . Cyclosporin A enhanced VP-16 efficacy whereas PSC-833 impaired VP-16 efficacy against these murine tumors . Possible reasons for these disparate effects are discussed. Cancer Chemother Pharmacol, 1997, 39(5), 424 - 30 The potential of N-{2-(dimethylamino)ethyl}acridine-4-carboxamide to circumvent three multidrug-resistance phenotypes in vitro; Davey RA et al.; The effectiveness of N-{2-(dimethylamino)ethyl}acridine-4-carboxamide (DACA) relative to that of amsacrine, idarubicin, daunorubicin and paclitaxel against three different forms of multidrug resistance (MDR) was determined using two sublines of the CCRF-CEM human leukaemia cell line, the P-glyco-protein-expressing CEM/VLB100 subline and the MRP-expressing CEM/E1000 subline, and two extended-MDR sublines of the HL60 human leukaemia cell line, HL60/E8 and HL60/V8 . DACA was effective against P-glycoprotein-mediated MDR and MRP-mediated MDR, whereas the extended-MDR phenotype showed only low levels of resistance (< 2-fold) to DACA . In comparison, idarubicin was ineffective against the MRP and extended-MDR phenotypes . Repeated exposure of the K562 human leukaemia cell line to DACA (55, 546 or 1092 nM for 3 days over 10 weeks) did not result in the development of any significant drug resistance . We conclude that DACA has the potential to treat refractory leukaemia. Cancer Chemother Pharmacol, 1997, 39(5), 417 - 23 Induction of apoptosis in multi-drug resistant (MDR) human glioblastoma cells by SN-38, a metabolite of the camptothecin derivative CPT-11; Nakatsu S et al.; The overexpression of the multidrug resistance (mdr1) gene and its product, P-glycoprotein (P-gp), is thought to limit the successful chemotherapy of human tumors . Recent studies demonstrate that SN-38, a metabolite of the camptothecin (CPT) derivative CPT-11, has antitumor effects on several tumors, but the mechanisms responsible for its cytotoxicity remain unclear . We therefore determined whether SN-38 has cytotoxic effects on MDR human glioblastoma GB-1 cells and non-MDR human glioblastoma U87-MG cells . Furthermore, we determined what role SN-38 plays in the induction of cytotoxicity in these tumor cells . In this study, we demonstrated that SN-38 had significantly stronger antitumor effects on GB-1 and U-87MG cells than did CPT (P < 0.01 and P < 0.05, respectively) . In addition, findings obtained using a DNA fragmentation assay, Hoechst 33258 staining, in situ end-labeling and cell cycle analysis demonstrated that SN-38 induced apoptosis in these tumors . Our results suggest that SN-38 has a stronger antitumor effect on malignant glioma cells regardless of MDR expression than does CPT, and therefore can be considered a new chemotherapeutic agent potentially effective in the treatment of human primary or recurrent malignant gliomas resistant to chemotherapy. Br J Cancer, 1997, 75(4), 608 - 13 Phase I trial and pharmacokinetics of the tubulin inhibitor 1069C85--a synthetic agent binding at the colchicine site designed to overcome multidrug resistance; Judson I et al.; The orally administered tubulin-binding agent 1069C85 was developed with the hope of overcoming the multidrug resistance associated with existing anti-tubulin agents, such as the vinca alkaloids . A phase I study was performed using a single oral dose every 3 weeks, administered as a suspension reconstituted in 0.1% Tween 80 and 0.9% saline . The starting dose was 2.8 mg m-2, and dose doubling was permitted until the area under curve (AUC) was > or = 40% of that at the mouse LD10; thereafter, a modified Fibonacci scheme was used . The formulation proved to be unsatisfactory, resulting in inconsistent absorption . The terminal elimination half-life was prolonged (range 18-73.5 h) . Sporadic central neurotoxicity was observed, which was grade 3 in one patient treated at 200 mg m-2 . A revised formulation with micronized drug was more easily suspended and appeared to increase the bioavailability by a factor of 2-4 . Severe central neurotoxicity, up to grade 4, was then observed at doses of 50-100 mg m-2 . Unfortunately, toxicity was not predictable and one patient, with a previous history of partial intestinal obstruction, treated at 50 mg m-2, cleared the drug very slowly, possibly because of prolonged, delayed absorption . This patient died from pancytopenia and severe gastrointestinal damage . It was concluded that such unpredictable behaviour would be incompatible with safe evaluation in phase II studies; the trial was closed and further clinical development abandoned. Jpn J Cancer Res, 1997 Jan, 88(1), 88 - 96 Establishment by adriamycin exposure of multidrug-resistant rat ascites hepatoma AH130 cells showing low DT-diaphorase activity and high cross resistance to mitomycins; Wakusawa S et al.; A resistant subline (AH130/5A) selected from rat hepatoma AH130 cells after exposure to adriamycin (ADM) showed remarkable resistance to multiple antitumor drugs, including mitomycin C (MMC) and porfiromycin (PFM) . PFM, vinblastine (VLB), and ADM accumulated in AH130/5A far less than in the parent AH130 (AH130/P) cells . AH130/5A cells showed overexpression of P-glycoprotein (PGP), an increase in glutathione S-transferase activity, and a decrease in DT-diaphorase and glutathione peroxidase activity . The resistance to MMC and VLB of AH130/5A cells was partly reversed by H-87, an inhibitor of PGP . Buthionine sulfoximine, an inhibitor of glutathione synthase, did not affect the action of MMC . tert-Butylhydroquinone induced DT-diaphorase activity, increased PFM uptake, and enhanced the growth-inhibitory action of MMC in AH130/5A cells . Dicumarol, an inhibitor of DT-diaphorase, decreased PFM uptake and reduced the growth-inhibitory action of MMC in AH130/P cells . These results indicated that the adriamycin treatment of hepatoma cells caused multifactorial multidrug resistance involving a decrease in DT-diaphorase activity. Cancer Detect Prev, 1997, 21(1), 78 - 82 Comparison of daunorubicin and Fluo-3 for detection of multidrug resistance in human tumor cells; Gheuens EE et al.; The detection of multidrug resistance (MDR) in clinical samples is still a topic for discussion . One method, proven extremely useful for detection of membrane proteins in patients with hematological malignancies is the flow cytometrical analysis of individual tumor cells . Recently an assay was described based on the labeling of the P-glycoprotein (P-gp) with the monoclonal antibody MRK16, combined with detection of active daunorubicin (DNR) extrusion . In order to improve the specificity of the assay, on line with the results obtained by Wall et al., we exploited staining with Fluo-3 . Both assays prove to be able to discriminate between drug-resistant and drug-sensitive cells . A major drawback of labeling with Fluo-3 in combination with the monoclonal antibody MRK16 is the important overlap of emission spectra of both fluorochromes . Moreover, using Fluo-3 for the detection of MDR might be complicated by the fact that differences in fluorescence intensities are not solely dependent on the presence of P-gp, but also on the activity of cytosolic esterases and the intracellular calcium concentration . Combination of the detection of structural and functional aspects of the MDR-associated protein may lead to a more precise detection of the MDR-positive patient. Br J Cancer, 1997, 75(5), 715 - 21 Cyclosporin A as a multidrug-resistant modulator in patients with renal cell carcinoma treated with teniposide; Toffoli G et al.; Patients with refractory metastatic renal cell carcinoma (RCC) were enrolled in a phase II study with teniposide (VM26) and cyclosporin A (CSA) to investigate (1) the effect of CSA on the response rate to VM26; and (2) the effect of CSA on the pharmacokinetics and pharmacodynamics of VM26 . Sixteen patients initially received VM26 alone (200 mg m(-2) day(-1) i.v.) . No objective responses were observed and all patients crossed over to receive at least an additional two courses (range 2-5) of VM26 plus CSA (5 mg kg(-1) 2h(-1) followed by 30 mg kg(-1) 48h(-1) i.v.) . At the end of the 2-h loading dose of CSA, whole-blood CSA levels ranged from 2250 to 3830 ng ml(-1), whereas at the end of the 48-h CSA infusion, CSA ranged from 1830 to 4501 ng ml(-1) . CSA significantly (P<0.01) increased the area under the curve (AUC) of VM26 . The variation in the paired AUC of VM26 was 50% . Terminal half-life of VM26 was significantly (P<0.01) increased (1.72-fold) after CSA administration, whereas the systemic clearance of VM26 was decreased by 1.4-fold (P<0.01) . The nadir neutrophil count after VM26 plus CSA (median 700 microl(-1), range <100 to 2860 microl(-1)) was lower than after VM26 alone (median 1900 microl(-1), range 200 to 6000 microl(-1)) . Increased haematological toxicity after CSA could be explained by the increase in the VM26 AUC and by inhibition of P-glycoprotein (P-gp) activity in haematopoietic precursor cells . Bilirubin concentrations in the serum were increased after VM26 plus CSA compared with VM26 alone (P<0.01) . Among the 15 patients evaluable for response, one had a minor response, eight had stable disease, and six had progressive disease . In conclusion, the dose of CSA we used achieved plasma concentrations within the effective range for P-gp inhibition . CSA affected both the pharmacokinetics and pharmacodynamics of VM26 in the patients, principally by increasing the plasma concentrations of the antineoplastic drug and VM26 haemopoietic toxicity. Am J Physiol, 1997 Jan, 272(1 Pt 1), G16 - 22 Molecular cloning of canalicular multispecific organic anion transporter defective in EHBR; Ito K et al.; Several organic anions are excreted into the bile via a canalicular multispecific organic anion transporter (cMOAT), which is hereditarily defective in mutant rats, such as the Eisai hyperbilirubinemic rat (EHBR) and TR- rat . In the present study, we cloned cMOAT from the Sprague-Dawley rat liver cDNA library based on the homology with human multidrug resistance-associated protein (hMRP) . cMOAT was encoded by 4,623-base pair (bp) cDNA with a homology of 53.0 and 46.3% with hMRP at the cDNA and deduced amino acid level, respectively . The deduced amino acid sequence was the same as that cloned in Wistar rats (C . C . Paulusma, P . J . Bosma, G . J . Zaman, C . T . Bakker, M . Otter, G . L . Sceffer, P . Borst, and R . P . Oude Elferink . Science Wash . DC 271: 1126, 1996) except for four amino acid substitutions . By screening the library, three kinds of cDNA species for cMOAT with the same open reading frame and different 3'-untranslated region lengths (0.2, 1.5, and 3.5 kbp) were isolated . The Northern blot analysis of poly(A)+ RNA from the liver revealed that the expression of plural bands (approximately 5, 6, and 8 kb) was defective in EHBR, and this may be due to the presence of these cDNA species . Expression of cMOAT was observed almost exclusively in the liver and to a lesser extent in the duodenum, kidney, and jejunum . Reverse transcription-polymerase chain reaction (RT-PCR) and subsequent sequence analysis of EHBR liver, kidney, duodenum, and jejunum revealed that 1-bp replacement from G to A at nucleotide 2564 resulted in the introduction of the premature stop codon in all tissues examined . This mutation was different from that observed in TR (C . C . Paulusma, P . J . Bosma, G . J . Zaman, C . T . Bakker, M . Otter, G . L . Sceffer, P . Borst, and R . P . Oude Elferink . Science Wash . DC 271: 1126, 1996) . Because EHBR and TR- are allelic mutants and both strains exhibit an autosomal recessive inheritance in the biliary excretion of organic anions it was concluded that the impaired expression of this particular protein is related to the pathogenesis of hyperbilirubinemia in the mutant animals. Plant Mol Biol, 1997 Jan, 33(2), 199 - 209 State of the art of the production of the antimalarial compound artemisinin in plants; Van Geldre E et al.; For more than three centuries we have relied on the extracts of the bark of Cinchona species to treat malaria . Now, it seems we may be changing to the leaves of a Chinese weed, Artemisia annua, and its active compound artemisinin . Artemisinin-derived drugs have been proved particularly effective treatments for severe malaria, even for multidrug-resistant malaria . However, this promising antimalarial compound remains expensive and is hardly available on a global scale . Therefore, many research groups have directed their investigations toward the enhancement of artemisinin production in A . annua cell cultures or whole plants in order to overproduce artemisinin or one of its precursors . This article provides a brief review of the state of art of the different aspects in A . annua research. FASEB J, 1997 Jan, 11(1), 19 - 28 Hepatic canalicular membrane 1: The role of mdr2 P-glycoprotein in hepatobiliary lipid transport; Elferink RP et al.; The small apical (canalicular) domains of hepatocytes form a luminal meshwork of tubules between adjacent hepatocytes and are the sites of primary bile formation . Organic compounds are transported across this membrane domain against high concentration gradients . It has been recognized in recent years that the hepatocyte is harnessed with a set of canalicular ATP-dependent transport proteins, specialized in this uphill transport . Bile salts, organic anions, cations, and neutral amphipaths are all pumped into the bile via such primary active transporters . Functionally, these transporters resemble ABC transporters overexpressed in cells with the multidrug resistance phenotype . Indeed, those transporters that have been characterized at the molecular level turn out to be new, or already recognized, members of this family . Phospholipid secretion across the canalicular membrane of the mouse is also mediated by a member of this family, mdr2 P-glycoprotein . This was demonstrated by the absence of phospholipid secretion into bile of mice with a disrupted mdr2 gene and by subsequent demonstration of phospholipid translocation in cells that overexpress this protein . The recognition of mdr2 P-glycoprotein as a phospholipid flippase sheds new light on the function of P-glycoproteins and is an important step in understanding the mechanism of biliary lipid secretion. J Formos Med Assoc, 1997 Jan, 96(1), 13 - 6 In vitro activity of ofloxacin against Mycobacterium tuberculosis; Yu MC et al.; For the past 3 years, ofloxacin has been widely used in treating patients with drug-resistant tuberculosis in Taiwan . To study its usefulness in treating these patients, 139 isolates of Mycobacterium tuberculosis from patients treated at the Taiwan Provincial Chronic Disease Control Bureau from September 1994 to September 1995 were tested to determine the in vitro antituberculosis activity of ofloxacin . Of these, 131 had not been previously exposed to ofloxacin, and 130 (99.2%) were susceptible to ofloxacin . Sixty-four isolates were found to be susceptible to all conventional antituberculosis drugs, and all of these were also susceptible to ofloxacin . Of the remaining 67 isolates that were resistant to one or more conventional antituberculosis drugs, 66 (98.5%) were susceptible to ofloxacin . There was no association between susceptibility to ofloxacin and susceptibility to conventional antituberculosis drugs among the isolates tested . Of the eight isolates of M . tuberculosis previously exposed to ofloxacin, seven (87.5%) were resistant . Our results indicate that patients with multidrug-resistant strains of M . tuberculosis who have not received prior ofloxacin treatment may be safely treated with ofloxacin even without knowing the result of pretreatment ofloxacin susceptibility tests . We also found that ofloxacin resistance emerges frequently . Therefore, an adequate combination of antituberculosis drugs, along with ofloxacin, should be prescribed to prevent the development of resistance to ofloxacin. Leuk Res, 1997 Jan, 21(1), 37 - 43 Ether lipids are effective cytotoxic drugs against multidrug-resistant acute leukemia cells and can act by the induction of apoptosis; Verdonck LF et al.; We studied the cytotoxic effects of two ether lipids, a relatively new class of anticancer drugs, on multidrug-resistant (MDR1) leukemia cells of patients with acute leukemias who had failed induction treatment . The cytotoxicity of ether lipids was determined by the elimination of clonogenic leukemia cells from leukemic cultures or, in case of failure to generate leukemic cultures, by the inhibition of 3{H}thymidine incorporation in leukemic blasts . At dose levels of 50 microg/ml, a plasma level that can be achieved after oral intake, the MDR1-positive blasts were killed, both of patients with drug-resistant acute myeloid leukemia (AML) and of patients with drug-resistant acute lymphoblastic leukemia (ALL) . The leukemic blasts were killed by the induction of apoptosis . These data suggest that ether lipids may be effective antileukemic drugs and that their cytotoxic function is not affected by MDR1. Gan To Kagaku Ryoho, 1997 Jan, 24(1), 87 - 92 {Intracellular distribution of bovine serum albumin-conjugated doxorubicin and multidrug resistance}; Takahashi N et al.; The intracellular distribution of bovine serum albumin (BSA)-conjugated {14C} doxorubicin (DXR) was investigated in a rat hepatoma cell line (AH66P) and its anthracycline resistant subline (AH66DR) . After the conjugate had been taken up into the cells by endocytosis and degraded in the lysomes, active adducts with a molecular mass of approximately 2 kDa were distributed to target organellae such as nuclei and mitochondria . Drug accumulation in the nuclear fraction was lower in AH66DR cells than in AH66P cells, but the level of drug radioactivity in the DNA fraction, which was extracted from the same nuclear fraction, was higher in the AH66DR cells than in AH66P cells . It is presumed from these results that the intercalated level of the drug into DNA was sufficient to exhibit cytotoxicity against AH66DR cells as well as AH66P cells . A part of the active adducts was effluxed from AH66DR cells by P glycoprotein (Pgp) in the same manner as DXR because the efflux of the adducts was suppressed by verapamil, an inhibitor of Pgp . The IC50 values of BSA DXR conjugate was decreased from 120 nM to 2 nM for AH66DR cells and from 3 nM to 0.6 nM for AH66P cells by the co-treatment with 5/M verapamil, respectively. Cancer Gene Ther, 1997 Jan-Feb, 4(1), 51 - 8 Coexpression of a multidrug resistance gene (MDR1) and herpes simplex virus thymidine kinase gene in a bicistronic retroviral vector Ha-MDR-IRES-TK allows selective killing of MDR1-transduced human tumors transplanted in nude mice; Sugimoto Y et al.; Ha-MDR-IRES-TK is a bicistronic vector that coexpresses the MDR1 gene and the herpes simplex virus thymidine kinase (HSV-TK) gene . In the present study we examined the effect of ganciclovir on MDR1-positive tumors that have been transduced with Ha-MDR-IRES-TK . To establish a human tumor xenograft model of MDR1-transduced recurrent tumors, human KB-3-1 carcinoma cells were transduced with HaMDR or Ha-MDR-IRES-TK, and one each of representative clones, termed KB/MDR and KB/MDR-TK, respectively, were isolated . KB/MDR and KB/MDR-TK showed similar levels of multidrug resistance in vitro . Vinblastine strongly inhibited the growth of the parental KB-3-1 tumors in nude mice but showed little or no effect against KB/MDR-TK tumors . Ganciclovir inhibited the in vivo growth of KB/MDR-TK tumors almost completely under conditions that did not affect the growth of KB-3-1 tumors . Coadministration of vinblastine and ganciclovir inhibited the in vivo growth of KB/MDR-TK premixed with KB-3-1 at any ratio . Long-term, high-level expression of human P-glycoprotein was observed in peripheral blood cells of mice transplanted with Ha-MDR-IRES-TK-transduced bone marrow cells . Ganciclovir eliminated the P-glycoprotein-positive normal blood cells . However, no systemic toxicity was observed . These results clearly demonstrate that it is possible to use ganciclovir to treat MDR1-positive tumors that have been unintentionally transduced with Ha-MDR-IRES-TK . This safety-modified vector should be useful for introducing the MDR1 gene into bone marrow cells to protect normal cells from the toxic effects of cancer chemotherapy. J Cell Sci, 1997 Jan, 110 ( Pt 1), 75 - 83 Transport of sphingomyelin to the cell surface is inhibited by brefeldin A and in mitosis, where C6-NBD-sphingomyelin is translocated across the plasma membrane by a multidrug transporter activity; van Helvoort A et al.; Sphingomyelin is a major lipid of the mammalian cell surface . The view that sphingomyelin, after synthesis in the Golgi lumen, reaches the outer leaflet of the plasma membrane on the inside of carrier vesicles has been challenged by inconsistencies in the results of transport studies . To investigate whether an alternative pathway to the cell surface exists for sphingomyelin, brefeldin A and mitotic cells were used to block vesicular traffic between the Golgi complex and the plasma membrane . Exogenous sphingomyelinase was applied in the cold to assay for the presence of sphingomyelin on the surface of CHO cells . Newly synthesized radiolabeled sphingomyelin was found to equilibrate with cell surface sphingomyelin within 1.5 hours at 37 degrees C . Brefeldin A and mitosis inhibited this transport but, surprisingly, not the surface appearance of the short-chain sphingomyelin analog N-6{7-nitro-2,1,3-benzoxadiazol-4-yl}aminohexanoyl(C6-NBD)-sphingo myelin as assayed by depletion of this lipid in the medium by the scavenger albumin . Transport of C6-NBD-sphingomyelin in the presence of brefeldin A was blocked by cyclosporin A and PSC 833, inhibitors of the multidrug resistance P-glycoprotein . The same was observed in HepG2 and HeLa cells, and for short-chain glucosylceramide, which demonstrates the general nature of the transporter-dependent sphingolipid translocation across the plasma membrane. Life Sci, 1997, 60(4-5), 307 - 13 Calcein is excreted from the intestinal mucosal cell membrane by the active transport system; Fujita T et al.; In this study, we report the efflux mechanism of calcein, an organic anion, mediated by a multidrug resistance-associated protein (MRP)-like protein in the intestinal mucosal membrane . The transport of calcein from the mucosal to serosal side was decreased dose-dependently and was significantly lower than that of the opposite direction . In addition, its transport was increased in the presence of metabolic inhibitors and probenecid . Furthermore, the efflux of calcein from the intestinal cell membrane, which was preloaded with calcein acetoxymethyl ester, was predominantly observed in the mucosal side rather than in the serosal side . Its efflux to the mucosal side was inhibited by the metabolic inhibitors and probenecid, not by verapamil which is a P-glycoprotein substrate . These results indicated that the transport of calcein and possibly other organic anions across the intestinal membrane may be regulated by the MRP-like protein, but not P-glycoprotein. Br J Cancer, 1997, 75(2), 208 - 12 Expression of the multidrug resistance-associated protein (MRP) gene in colorectal carcinomas; Fillpits M et al.; To determine the clinical significance of MRP in patients with colorectal carcinomas, we have studied the expression of the MRP gene by reverse transcription-polymerase chain reaction (RT-PCR) (n = 105) and by immunohistochemistry (n = 30) . MRP mRNA expression was observed in 92 (88%) tumour specimens . Positive MRP staining with monoclonal antibodies QCRL-1 and QCRL-3 was detected in all samples studied with strong staining in seven (23%) and weak staining in 23 (77%) specimens . Strong MRP staining in these samples did not appear to be related to the age and sex of the patients, localization of the primary tumour, histological grade, tumour size, lymph node metastasis, distant metastasis and tumour stage . Strong MRP staining was not associated with MDR1 RNA or P-glycoprotein (P-gp) expression . Kaplan-Meier curves revealed that overall survival of patients with strong MRP-staining tumours was similar to the survival of patients with weak-staining tumours . These data indicate that the MRP gene is expressed in primary colorectal carcinomas but is neither related to known prognostic factors nor a prognostic factor by itself. Br J Cancer, 1997, 75(2), 161 - 8 Effect of glucose transport inhibitors on vincristine efflux in multidrug-resistant murine erythroleukaemia cells overexpressing the multidrug resistance-associated protein (MRP) and two glucose transport proteins, GLUT1 and GLUT3; Martell RL et al.; The relationship between mammalian facilitative glucose transport proteins (GLUT) and multidrug resistance was examined in two vincristine (VCR)-selected murine erythroleukaemia (MEL) PC4 cell lines . GLUT proteins, GLUT1 and GLUT3, were constitutively coexpressed in the parental cell line and also in the VCR-selected cell lines . Increased expression of the GLUT1 isoform was noted both in the PC-V40 (a non-P-glycoprotein, mrp-overexpressing subline) and in the more resistant PC-V160 (overexpressing mrp and mdr3) cell lines . Overexpression of GLUT3 was detected only in the PC-V160 subline . An increased rate of facilitative glucose transport (Vmax) and level of plasma membrane GLUT protein expression paralleled increased VCR resistance, active VCR efflux and decreased VCR steady-state accumulation in these cell lines . Glucose transport inhibitors (GTIs), cytochalasin B (CB) and phloretin blocked the active efflux and decreased steady-state accumulation of VCR in the PC-V40 subline . GTIs did not significantly affect VCR accumulation in the parental or PC-V160 cells . A comparison of protein sequences among GLUT1, GLUT3 and MRP revealed a putative cytochalasin B binding site in MRP, which displayed 44% sequence similarity/12% identity with that previously identified in GLUT1 and GLUT3; these regions also exhibited a similar hydropathy plot pattern . The findings suggested that CB bound to MRP and directly or indirectly lowered VCR efflux and/or CB bound to one or both GLUT proteins, which acted to lower the VCR efflux mediated by MRP . This is the first report of a non-neuronal murine cell line that expressed GLUT3. Leukemia, 1997 Jan, 11(1), 48 - 53 A novel energy dependent mechanism reducing daunorubicin accumulation in acute myeloid leukemia; Hedley DW et al.; Using cyclosporin A (CsA) to inhibit P-glycoprotein (P-gp) function we showed previously that there was a discordance between the ability of acute myeloid leukemic (AML) blast cells to accumulate daunorubicin and P-gp antigen expression (Xie et al, Leukemia 1995; 9:1882-1887) . This discordance suggests that a CsA-sensitive drug efflux mechanism distinct from P-gp is expressed in many clinical samples . In the present study using the ATP depleting agents cyanide, azide, or dinitrophenol to inhibit energy dependent transport processes, we observed even larger increases in daunorubicin accumulation than were seen with CsA . Similar patterns were seen in a wide range of P-gp negative human cancer cell lines . Also the observed cyanide effect did not correlate with the expression of mRNA for multidrug resistance-associated protein (MRP), the only other member of the ABC family of membrane transporters that is known to be capable of effluxing daunorubicin . Thse results suggest that daunorubicin accumulation in many cases of AML is modulated by one or more novel energy-dependent processes that are distinct from P-gp or MRP . We speculate that this novel drug transport mechanism(s) may influence the response of AML patients to daunorubicin and other therapeutic agents. J Cancer Res Clin Oncol, 1997, 123(1), 21 - 4 Cyclosporin A enhances locoregional metastasis of the CC531 rat colon tumour; Van de Vrie W et al.; The immunosuppressive drug cyclosporin A has been evaluated recently in phase II trials in cancer therapy as a reverter of P-glycoprotein-mediated multidrug resistance . As an immunosuppressive agent, cyclosporin A potentially can enhance tumour growth . We investigated this potency of cyclosporin A in the weakly immunogenic CC531 colon adenocarcinoma model, using the same dose that had previously been shown to intensify the antitumour activity of doxorubicin in vivo . In vitro cyclosporin A caused no growth acceleration and only in high doses was growth inhibition of CC531 cells observed . In vivo no evidence of growth enhancement was found in short-term assays but, after 4 weeks, rats treated with cyclosporin A had a significantly higher tumour load, mainly consisting of locoregional metastases . These experiments in the CC531 tumour model show that cyclosporin A, used as a reverter of multidrug resistance, may produce short-term improvement of antitumour activity but may also induce enhancement of tumour metastasis. Cancer Chemother Pharmacol, 1997, 39(3), 212 - 6 Toremifene concentration and multidrug resistance in lung tumors; Liippo K et al.; In this pharmacokinetics study, concentrations of toremifene (TOR), a new antiestrogen, were measured after a 7-day oral treatment in serum, lung, and tumor tissue to determine the optimal dose of TOR for the modulation of clinical multidrug resistance in patients with lung cancer . Target levels of the antiestrogen were based on previous in vitro studies . Altogether, 18 patients with operable lung tumors were studied . TOR was given in an open, nonrandomized, phase I study at three different dose levels . The medication consisted of oral TOR given for 7 days at either 240, 480, or 600 mg/day before surgical removal of the tumor . At least five patients were scheduled to be included at each dose level, with all five receiving the full course of therapy before escalation of the dose . Blood samples for serum TOR concentration measurements were taken on days 0 and 7 . Specimens of tumor and normal lung tissue of approximately 0.5 g were taken on day 7 . The concentrations of TOR and its metabolites were determined in serum, lung, and tumor tissue at different dose levels . Altogether, 12 evaluable patients completed the scheduled treatment . The concentrations measured in serum, lung, and tumor tissue increased along with the dose used, such that the highest TOR values were achieved at 600 mg/day, with mean values being 4.9 mumol/l, 175.0 mumol/g, and 122.7 mumol/g, respectively . The concentrations of TOR and its metabolite N-demethyltoremifene were highest in lung tissue, but the values measured in tumor specimens were also well above the respective concentrations detected in serum samples . The TOR doses of 240 and 480 mg/day were well tolerated . One patient in the group treated at 600 mg/day had to discontinue the treatment because of headache and nausea . TOR given at doses ranging from 480 to 600 mg/day for 7 days will produce serum, lung, and tumor concentrations of the parent drug and its metabolites that have been shown to reverse multidrug resistance of cancer cells in vitro . As the 480-mg/day dose of TOR produced tumor concentrations high enough to reverse multidrug resistance without producing adverse drug reactions, the dose recommended for the foreseen clinical trials in the reversal of multidrug resistance would be 480 mg/day for 7 days. Chest, 1997 Jan, 111(1), 148 - 53 Drug-resistant Mycobacterium tuberculosis and atypical mycobacteria isolated from patients with suspected pulmonary tuberculosis in Honduras<