Multidrug resistant

Mol Cell Biol, 1986 Dec, 6(12), 4268 - 73
Multidrug-resistant phenotype cosegregates with an amplified gene in somatic cell hybrids of drug-resistant Chinese hamster ovary cells and drug-sensitive murine cells; Teeter LD et al.; Gene amplification has been associated with multidrug resistance (MDR) in several drug-resistant Chinese hamster ovary (CHO) cell lines which exhibit cross-resistance to other unrelated, cytotoxic drugs . In situ hybridization studies (Teeter et al., J . Cell Biol., in press) suggested the presence of an amplified gene associated with the MDR phenotype on the long arm of either of the largest CHO chromosomes (1 or Z1) in vincristine-resistant cells . In this study, somatic cell hybrids were constructed between these vincristine-resistant CHO cells and drug-sensitive murine cells to determine the functional relationship between the chromosome bearing the amplified sequences and the MDR phenotype . Hybrids exhibited primary drug resistance and MDR in an incomplete dominant fashion . Hybrid clones and subclones segregated CHO chromosomes . Concordant segregation between vincristine resistance, the MDR phenotype, the presence of the MDR-associated amplified sequences, overexpression of the gene located in those sequences, and CHO chromosome Z1 was consistent with the hypothesis that there is an amplified gene on chromosome Z1 of the vincristine-resistant CHO cells which is responsible for the MDR in these cells . A low level of discordance between CHO chromosomes Z8 and 2 and the drug resistance phenotype suggests that these chromosomes may contain genes involved with the MDR phenotype.

Cancer Res, 1986 Dec, 46(12 Pt 1), 6290 - 4
Isolation and characterization of a Chinese hamster ovary cell line resistant to bifunctional nitrogen mustards; Robson CN et al.; A drug-resistant derivative of a Chinese hamster ovary cell line has been generated by chronic exposure to progressively higher concentrations of chlorambucil . The cells exhibit greater than 20-fold resistance to the cytotoxic effects of chlorambucil and comparable levels of cross-resistance to mechlorethamine and melphalan . These drugs all belong to a class of bifunctional alkylating agents which generate DNA cross-links by reaction at the N-7 position of guanine . However, no resistance is observed to several other drugs which possess a similar mechanism of action, to cis-platinum diammine dichloride or to bischloroethylnitrosourea and mitomycin C, which cross-link DNA via the O6 position of guanine . Lack of resistance to vincristine, colchicine, or Adriamycin coupled with the failure of the calcium channel blocker verapamil to reverse the phenotype, indicates that the mechanism of resistance is distinct from that characterized by the multidrug-resistant phenotype . Support for this view comes from the finding that no significant alteration in melphalan uptake could be demonstrated . The phenotype is very stable and has been maintained during 12 months of continuous culture without further selection . A slightly elevated basal level of glutathione is present in the resistant cells, but resistance is not overcome by depletion of intracellular glutathione with buthionine sulfoximine . A cytosolic protein with a molecular weight of approximately 25,000 is constitutively overexpressed in the resistant cells . Although these cells have an abnormal karyotype, no conclusive evidence for any cytogenetic indicator of gene amplification could be detected.

Proc Natl Acad Sci U S A, 1986 Dec, 83(24), 9328 - 32
Similar biochemical changes associated with multidrug resistance in human breast cancer cells and carcinogen-induced resistance to xenobiotics in rats; Cowan KH et al.; MCF7 human breast cancer cells selected for resistance to doxorubicin (adriamycin; DoxR) have developed the phenotype of multidrug resistance . Multidrug resistance in DoxR MCF7 cells (called AdrR MCF7 cell line in previous publications) is associated with biochemical changes similar to those induced by carcinogens in rat hyperplastic liver nodules (HNs) and associated with resistance to xenobiotics in that system . In HNs and DoxR cells, exposure to a single agent results in the selection of cells that are cross-resistant to a wide variety of structurally dissimilar toxic agents . Resistance in both systems is associated with decreases in intracellular accumulation of toxins and changes in phase I (decreased cytochrome P1-450) and phase II (increased glutathione transferase and glucuronyltransferase) drug-metabolizing activities . In HNs and DoxR cells, resistance is associated with the induction of relatively stable levels of an immunologically related anionic glutathione transferase isozyme (EC 2.5.1.18) . The finding of similar biochemical changes associated with the development of resistance to various xenobiotics in HNs and to many naturally occurring antineoplastic agents and at least one carcinogen (benzo{a}pyrene) in DoxR MCF7 cells suggests that the mechanisms of resistance in these two models may be similar.

EMBO J, 1986 Dec 1, 5(12), 3201 - 8
A 22-kd protein (sorcin/V19) encoded by an amplified gene in multidrug-resistant cells, is homologous to the calcium-binding light chain of calpain; Van der Bliek AM et al.; We have previously shown that at least five linked genes are co-amplified and overexpressed in the multi-drug resistant (MDR) Chinese hamster ovary cell line CHRC5 . We show here that one of these genes (class 4) codes for a small phosphorylated, cytosolic protein, sorcin/V19, known to be overproduced by many MDR cell lines . The class 4 gene codes for a nested set of mRNAs, varying in size between 1000 and 2500 nucleotides . Sequence analysis of complementary DNAs shows that these mRNAs encode a protein of 198 amino acids . The identity of this protein with sorcin was established by comparison with the amino acid sequence of two peptides from mouse sorcin . Hamster sorcin is a 22-kd protein with four 'E-F hand' structures typical of calcium-binding sites and it has substantial homology with the light chain of calpain . Two of the calcium-binding sites contain putative recognition sites for cAMP-dependent protein kinase . These may account for the known phosphorylation of sorcin . The unknown function of sorcin might therefore be controlled by both calcium and cAMP levels . The contribution of sorcin to multidrug resistance, if any, remains to be tested.

Mol Cell Biol, 1986 Dec, 6(12), 4717 - 22
Differential amplification and disproportionate expression of five genes in three multidrug-resistant Chinese hamster lung cell lines; de Bruijn MH et al.; At least five linked genes are amplified in the multidrug-resistant Chinese hamster ovary cell line CHRC5, selected with colchicine (A . M . Van der Bliek, T . Van der Velde-Koerts, V . Ling, and P . Borst, Mol . Cell . Biol . 6:1671-1678, 1986) . We report here that only a subset of these, encoding the 170-kilodalton P-glycoprotein, are consistently amplified in three different multidrug-resistant Chinese hamster lung cell lines, selected with vincristine, daunorubicin, or actinomycin D . Within each cell line, genomic sequences homologous to the P-glycoprotein cDNA probe were amplified to different levels . The pattern of differential amplification was consistent with the presence of at least two and possibly three P-glycoprotein genes . In the actinomycin D-selected cell line, these genes were disproportionately overexpressed relative to the associated levels of amplification . These results underline a central role for P-glycoprotein in multidrug resistance . In the daunorubicin-selected cell line, another, as yet uncharacterized, gene was amplified but disproportionately underexpressed . Its amplification was therefore fortuitous . We present a tentative map of the region in the hamster genome that is amplified in the multidrug-resistant cell lines which were analyzed.

J Biol Chem, 1986 Nov 25, 261(33), 15544 - 9
Overexpression of a novel anionic glutathione transferase in multidrug-resistant human breast cancer cells; Batist G et al.; Adriamycin-resistant (AdrR) human breast cancer cells have been selected which exhibit cross-resistance to a wide range of anti-cancer drugs . This multidrug-resistant phenotype is associated with increases in the activities of glutathione peroxidase and glutathione transferase . The 45-fold increase in glutathione transferase activity is associated with the appearance of a new anionic isozyme in AdrR cells which is immunologically related to the anionic glutathione transferase present in human placenta . The increase in transferase and the level of drug resistance is relatively stable during passage of AdrR cells in the absence of adriamycin for over 10 months . A similar anionic glutathione transferase isozyme is also found in rat hyperplastic liver nodules, a preneoplastic state resulting from exposure to carcinogens . A rat cDNA which codes for the anionic glutathione transferase in rat hyperplastic nodules hybridizes to a 1.1-kilobase pair mRNA which is overexpressed in the AdrR MCF-7 cells . The anionic transferase has been purified from the AdrR cells and found to have characteristics which distinguish it from other anionic human glutathione transferases, including high levels of intrinsic peroxidase activity . The overexpression of a similar anionic glutathione transferase in human breast cancer cells selected for multidrug resistance and in rat hyperplastic liver nodules, which develop resistance to various hepatotoxins, suggests a possible role for this drug-conjugating enzyme in the mechanism of resistance in both of these states.

Cell, 1986 Nov 7, 47(3), 371 - 80
Mammalian multidrug resistance gene: complete cDNA sequence indicates strong homology to bacterial transport proteins; Gros P et al.; The complete nucleotide and primary structure (1276 amino acids) of a full length mdr cDNA capable of conferring a complete multidrug-resistant phenotype is presented . The deduced amino acid sequence suggests that mdr is a membrane glycoprotein which includes six pairs of transmembrane domains and a cluster of potentially N-linked glycosylation sites near the amino terminus . A striking feature of the protein is an internal duplication that includes approximately 500 amino acids . Each duplicated segment includes a consensus ATP-binding site . Amino acid homology is observed between the mdr gene and a series of bacterial transport genes . This strong homology suggests that a highly conserved functional unit involved in membrane transport is present in the mdr polypeptide . We propose that an energy-dependent transport mechanism is responsible for the multidrug-resistant phenotype.

Cell, 1986 Nov 7, 47(3), 381 - 9
Internal duplication and homology with bacterial transport proteins in the mdr1 (P-glycoprotein) gene from multidrug-resistant human cells; Chen CJ et al.; Resistance of tumor cells to multiple cytotoxic drugs is a major impediment to cancer chemotherapy . Multidrug resistance in human cells is determined by the mdr1 gene, encoding a high molecular weight membrane glycoprotein (P-glycoprotein) . Complete primary structure of human P-glycoprotein has been determined from the cDNA sequence . The protein, 1280 amino acids long, consists of two homologous parts of approximately equal length . Each half of the protein includes a hydrophobic region with six predicted transmembrane segments and a hydrophilic region . The hydrophilic regions share homology with peripheral membrane components of bacterial active transport systems and include potential nucleotide-binding sites . These results are consistent with a function for P-glycoprotein as an energy-dependent efflux pump responsible for decreased drug accumulation in multidrug-resistant cells.

Mol Cell Biol, 1986 Nov, 6(11), 4039 - 45
Multidrug resistance of DNA-mediated transformants is linked to transfer of the human mdr1 gene; Shen DW et al.; Mouse NIH 3T3 cells were transformed to multidrug resistance with high-molecular-weight DNA from multidrug-resistant human KB carcinoma cells . The patterns of cross resistance to colchicine, vinblastine, and doxorubicin hydrochloride (Adriamycin; Adria Laboratories Inc.) of the human donor cell line and mouse recipients were similar . The multidrug-resistant human donor cell line contains amplified sequences of the mdr1 gene which are expressed at high levels . Both primary and secondary NIH 3T3 transformants contained and expressed these amplified human mdr1 sequences . Amplification and expression of the human mdr1 sequences and amplification of cotransferred human Alu sequences in the mouse cells correlated with the degree of multidrug resistance . These data suggest that the mdr1 gene is likely to be responsible for multidrug resistance in cultured cells.

Mol Cell Biol, 1986 Nov, 6(11), 3785 - 90
Chromosome-mediated gene transfer of multidrug resistance; Gros P et al.; Multidrug resistance can be transferred from drug-resistant LZ Chinese hamster cells to drug-susceptible mouse LTA cells by chromosome-mediated gene transfer . Analysis of genomic DNA demonstrated the transfer of multiple copies of a DNA domain which is amplified in the donor multidrug-resistant cells . The transfer of 10 to 15 copies of the Chinese hamster gene was sufficient to produce a multidrug-resistant phenotype . Chromosome transferents exhibited overexpression of an mRNA of approximately 5 kilobases which has previously been demonstrated to be encoded by the amplified DNA domain of the donor LZ cells . Phenotypic analysis of individual clones selected in adriamycin showed the resistance to be pleiotropic . All clones tested demonstrated similar levels of cross-resistance to the drugs daunorubicin and colchicine . These results indicate that the DNA sequences transferred confer the complete multidrug-resistant phenotype on recipient cells and suggest that multidrug resistance is due to overexpression of the protein encoded by the 5-kilobase mRNA.

Cancer Res, 1986 Nov, 46(11), 5941 - 6
Single cell analysis of daunomycin uptake and efflux in multidrug-resistant and -sensitive KB cells: effects of verapamil and other drugs; Willingham MC et al.; The accumulation of daunomycin in drug-sensitive and multidrug-resistant human KB cells was examined using light microscopy to detect the inherent fluorescence of daunomycin . Intracellular accumulation of fluorescent drug occurred rapidly in parental KB cells and was markedly reduced in several multidrug-resistant mutants . The addition of verapamil, which reverses multidrug resistance, resulted in increased accumulation of daunomycin in resistant cells . In living cells, most of the daunomycin was found in the nucleus, but significant amounts were detected associated with the plasma membrane, in the cytoplasm, in organelles of the Golgi region, and in lysosomes . The nuclear fluorescence was measured using a photometer system, and the loss of daunomycin from the cells was determined under various conditions . When sensitive cells were allowed to accumulate daunomycin for 5 min at 37 degrees C and then placed in medium without the drug, daunomycin remained inside the nuclei for longer than 1 day . When resistant cells were loaded in the presence of verapamil and the verapamil was removed, the resistant cells lost daunomycin with a half-time of about 1 min . The continuous presence of verapamil markedly inhibited the loss of daunomycin from the cells . Similar results were obtained in separate experiments using {3H}daunomycin . Vinblastine, vincristine, and quinidine were also effective in stimulating daunomycin accumulation in multidrug-resistant cells and in preventing the loss of daunomycin from these resistant cells . This effect required half-maximal concentrations of 1-2 microM for verapamil, vinblastine, and quinidine . Ouabain, lanthanum, colchicine, amiloride, probenecid, and 1-beta-D-arabinofuranosylcytosine had no effect on this process . Quinine was effective at 10 microM and nifedipine was effective at 50 microM . Depletion of cellular adenosine triphosphate levels by preincubation of cells with azide and 2-deoxyglucose partially inhibited daunomycin loss from resistant cells . These single-cell measurements indicate that diminished daunomycin accumulation in multidrug-resistant cells results from accelerated energy-dependent efflux across the plasma membrane, and this efflux is inhibited by verapamil, quinidine, vincristine, and vinblastine.

Nature, 1986 Oct 23-29, 323(6090), 728 - 31
Isolation and expression of a complementary DNA that confers multidrug resistance; Gros P et al.; The emergence and outgrowth of a population of tumour cells resistant to multiple drugs is a major problem in the chemotherapeutic treatment of cancer . We have used highly drug-resistant cell lines developed in vitro to study the molecular basis of multidrug resistance . In these cell lines high levels of resistance are frequently associated with amplification and overexpression of a small group of genes termed mdr or gp170 . Direct evaluation of the role of these genes in multidrug resistance has awaited the isolation of a member of this gene family in a biologically active form . Here we report the isolation of DNA clones complementary to the cellular messenger RNA transcripts of mdr genes and show that high-level expression of a full-length complementary DNA clone in an otherwise drug-sensitive cell confers a complete multidrug-resistant phenotype . Our results demonstrate that overexpression of a single member of the mdr group is sufficient to confer drug resistance . Furthermore, because the cDNA was isolated from a drug-sensitive cell, mutations in the primary sequence of mdr are not required to produce a multidrug-resistance phenotype.

Proc Natl Acad Sci U S A, 1986 Oct, 83(20), 7785 - 9
Functional role for the 170- to 180-kDa glycoprotein specific to drug-resistant tumor cells as revealed by monoclonal antibodies; Hamada H et al.; An overexpression of the plasma membrane glycoprotein of relative molecular size 170-180 kDa is consistently found in different multidrug-resistant human and animal cell lines, although the functional role of the protein in multidrug resistance is not known . Two monoclonal antibodies that interfere with biochemical functions were generated against the human myelogenous leukemia K-562 cells resistant to adriamycin (K-562/ADM) . These antibodies, designated MRK16 and MRK17, are specifically reactive to K-562/ADM and a human ovarian cancer cell line resistant to adriamycin (2780AD) . MRK16 modulated vincristine and actinomycin D transport in the resistant cells, while MRK17 specifically inhibited the growth of the resistant cells . Both antibodies recognized the 170- to 180-kDa glycoprotein . These data indicate that the 170- to 180-kDa glycoprotein is involved, directly or indirectly, in the drug transport mechanisms and the proliferation of multidrug-resistant tumor cell lines.

Cancer Res, 1986 Sep, 46(9), 4453 - 7
Reversal of multidrug resistance by synthetic isoprenoids in the KB human cancer cell line; Nakagawa M et al.; A colchicine resistant clone, Chr-24, derived from the human carcinoma KB cell line is extensively resistant to multiple drugs including vinblastine, vincristine, Adriamycin, actinomycin D, and daunomycin . In comparison with KB cells, very low accumulation of daunomycin or vincristine is observed in multidrug-resistant cells . Two isoprenoids with 9 to 10 isoprene chains (polyprenoids), N-(p-methylbenzyl)decaprenylamine and N-solanesyl-N,N'-bis(3,4-dimethoxybenzyl)ethylenediamine overcame the multidrug resistance almost completely in cultured Chr-24, whereas they only slightly sensitized the parental KB cells to anticancer agents . Both isoprenoids enhance the accumulation of vincristine or daunomycin in Chr-24, possibly by inhibiting efflux and also by enhancing influx of anticancer agents . A verapamil-like structure of N-solanesyl-N,N'-bis(3,4-dimethoxybenzyl)ethylenediamine is discussed in relation to its ability to overcome drug resistance.

Cancer Res, 1986 Sep, 46(9), 4352 - 6
Resistance to anthrapyrazoles and anthracyclines in multidrug-resistant P388 murine leukemia cells: reversal by calcium blockers and calmodulin antagonists; Klohs WD et al.; A series of anthrapyrazoles was examined for their cytotoxic effect on P388 cells resistant (P388R) to anthracyclines, N-{4-(9-acridinylamino)-3-methoxyphenyl} methanesulfonamide, trimetrexate, and vinblastine . The degree of resistance of P388R cells to Adriamycin (ADR) and daunomycin was 50-fold and 38-fold, respectively, when compared to the parent cell line (P388S) . The Adriamycin-resistant cells were highly cross-resistant to some anthrapyrazoles, but the degree of cross-resistance was not uniform and was less than 3-fold for one member of the series . The lipophilicity of these compounds appeared to correlate to some extent with the level of resistance . The calcium channel blockers verapamil (VER) and diltiazem and the calmodulin antagonist trifluoperazine potentiated the cytotoxicity of the anthrapyrazoles and ADR in P388R . This potentiating effect was concentration dependent with VER being the most efficacious . VER increased ADR cytotoxicity by greater than 10-fold and CI-937 by almost 40-fold . However, VER, diltiazem, and trifluoperazine had no effect on ADR or anthrapyrazole activity in P388S cells . The antiarrhythmic drug, quinidine, and the detergent, Tween 80, also potentiated ADR activity in P388R cells to the same extent as VER . Both the net accumulation and efflux of {3H}daunomycin were altered in P388R cells by nontoxic concentrations of Tween 80 in a fashion virtually identical to that demonstrated for VER . These data suggest that agents which potentiate drug cytotoxicity in P388R cells may do so by their interaction with the lipid domain of the plasma membrane . In addition, these results demonstrate that some members of the new series of DNA binding drugs, the anthrapyrazoles, may be active against anthracycline-resistant tumors and that, where cross-resistance to them occurs, it can be partially reversed by agents such as VER.

Proc Natl Acad Sci U S A, 1986 Aug, 83(15), 5521 - 5
Epidermal growth factor receptor is increased in multidrug-resistant Chinese hamster and mouse tumor cells; Meyers MB et al.; Multidrug-resistant sublines of Chinese hamster lung and mouse tumor cells selected for high levels of resistance to vincristine or actinomycin D have increased numbers of epidermal growth factor (EGF) receptors compared to control cells . Evidence for this increase was found in six of six resistant cell lines with the use of receptor binding or immunoprecipitation techniques . Levels of 125I-labeled EGF binding to intact actinomycin D-resistant cells derived from DC-3F or CLM-7 Chinese hamster lines are increased 3- to 10-fold compared to controls . Scatchard analysis of these data suggests that increased binding is a result of increased receptor number rather than altered affinity of receptor for ligand . Affinity-labeling and immunoprecipitation studies confirmed the finding of increased receptor amount in resistant hamster and mouse cells . Multidrug-resistant variants of DC-3F cells overproduce a plasma membrane glycoprotein (gp150-180) with several physicochemical properties that resemble those of EGF receptor . However, electrophoretic transfer blots with a polyclonal antibody to gp150-180 show that EGF receptor and gp150-180 are probably different molecules . Resistant cells described in this report manifest a normalized phenotype compared to transformed, tumorigenic, drug-sensitive parental cells . EGF receptor increase in resistant variants may be associated with this reverse transformation.

Somat Cell Mol Genet, 1986 Jul, 12(4), 415 - 20
Localization of multidrug resistance-associated DNA sequences to human chromosome 7; Fojo A et al.; Multidrug resistance in several human cell lines correlates with amplification or increased expression of two related DNA sequences, designated mdr1 and mdr2 . These DNA sequences were used as probes for hybridization with DNA with a panel of human-mouse somatic cell hybrids and from individual human chromosomes separated by fluorescence-activated chromosome sorting . By these assays, both mdr1 and mdr2 sequences were localized to chromosome 7.

J Biol Chem, 1986 Jun 15, 261(17), 7921 - 8
Increased vinblastine binding to membrane vesicles from multidrug-resistant KB cells; Cornwell MM et al.; Human KB carcinoma cells resistant to high levels of colchicine, vinblastine, vincristine, adriamycin, and actinomycin D exhibit reduced accumulation of these structurally unrelated chemotherapeutic agents (Akiyama, S.-I., Fojo, A., Hanover, J . A., Pastan, I., and Gottesman, M . M . (1985) Somatic Cell Mol . Genet . 11, 117-126; Fojo, A., Akiyama, S.-I., Gottesman, M . M., and Pastan, I . (1985) Cancer Res . 45, 3002-3007) . To examine the mechanism of reduced drug accumulation in these cells, we measured {3H}vinblastine ({3H}VBL) binding to membrane vesicles made from drug-sensitive (KB-3-1), drug-resistant (KB-C4), and revertant (KB-R1) cells . Membrane vesicles from KB-C4 cells bound up to 8-fold more {3H}VBL than vesicles from the parental KB-3-1 or revertant KB-R1 cell lines . No difference in binding of {3H}dexamethasone, to which the cells are equally sensitive, was observed . The difference in {3H}VBL binding by vesicles from resistant and sensitive cells was eliminated by the addition of 10 micrograms/ml verapamil, which is known to reverse the multidrug-resistance phenotype . Drug binding by KB-C4 vesicles was osmotically insensitive, temperature-dependent, and trypsin-sensitive . Binding of {3H}VBL by KB-C4 vesicles was inhibited by vinblastine, vincristine, and daunomycin (in decreasing order) . Dexamethasone at 100 microM, colchicine at 100 microM, and actinomycin D at 100 microM did not significantly inhibit {3H}VBL accumulation . No significant differences in tubulin content were detected among vesicles from sensitive and resistant cells . These data demonstrate that membrane vesicles from multiply drug-resistant cells bind increased amounts of vinblastine.

J Biol Chem, 1986 Jun 15, 261(17), 7762 - 70
Multiple drug-resistant human KB carcinoma cells independently selected for high-level resistance to colchicine, adriamycin, or vinblastine show changes in expression of specific proteins; Shen DW et al.; We have established four cell lines derived from the human KB carcinoma cell line which express high-level multiple drug resistance . One of these lines was selected for resistance to colchicine, one was selected for resistance to colchicine in the presence of the tumor promoter, mezerein, one for resistance to vinblastine, and one for resistance to adriamycin . All of these cell lines are cross-resistant to the other selective agents . The development of multidrug resistance in these cultured human carcinoma cells is associated with a limited number of specific protein alterations revealed by high resolution two-dimensional gel electrophoresis and Western blot analysis . These protein alterations in multidrug-resistant lines include the decreased prevalence of members of a family of proteins of molecular mass 70,000 to 80,000 daltons, pI 4.8-5.0, the increased synthesis of a protein of molecular mass 21,000 daltons, pI 5.0, in the colchicine-resistant cell lines only, and the increased expression of a 170,000-dalton protein in membrane preparations from all of the resistant cells . The loss of the 70,000- to 80,000-dalton proteins in the multidrug-resistant lines, which can also be demonstrated by immunoprecipitation of these proteins with specific antisera, is associated with a loss of translatable mRNA for these proteins . These studies suggest that only a limited number of protein changes occur in multidrug-resistant cell lines.

Proc Natl Acad Sci U S A, 1986 Jun, 83(12), 4538 - 42
Isolation of human mdr DNA sequences amplified in multidrug-resistant KB carcinoma cells; Roninson IB et al.; The ability of tumor cells to develop simultaneous resistance to structurally different cytotoxic drugs constitutes a major problem in cancer chemotherapy . It was previously demonstrated that multidrug-resistant Chinese hamster cell lines contain an amplified, transcriptionally active DNA sequence designated mdr . This report presents evidence that multidrug-resistant sublines of human KB carcinoma cells, selected for resistance to either colchicine, vinblastine, or Adriamycin (doxorubicin), display amplification of two different DNA sequences homologous to the hamster mdr gene . Segments of the human mdr DNA sequences, designated mdr1 and mdr2, have been cloned . mdr1 sequences were amplified in all of the highly drug-resistant sublines and were expressed as a poly(A)+ RNA species of 4.5 kilobases that was detected in the resistant cells but not in the parental cell line . No expression of mdr2 sequences was detected . mdr2 sequences were coamplified with mdr1 in some of the multidrug-resistant sublines and, in two independently derived cell lines, underwent very similar rearrangements . The data suggest that the mdr1 gene is involved in multidrug resistance in human cells.

Proc Natl Acad Sci U S A, 1986 Jun, 83(11), 3847 - 50
Membrane vesicles from multidrug-resistant human cancer cells contain a specific 150- to 170-kDa protein detected by photoaffinity labeling; Cornwell MM et al.; Multiple drug resistance of tumor cells is a common problem in cancer therapy . We have demonstrated that membrane vesicles from highly multidrug-resistant human KB carcinoma cell lines exhibit increased specific and saturable binding of vinblastine . To identify the molecules that bind vinblastine, membrane vesicles from multidrug-resistant cells were exposed to two analogs of vinblastine, N-(p-azido-{3,5-3H}benzoyl)-N'-(beta-aminoethyl)vindesine and N-(p-azido-{3-125I}salicyl)-N'-(beta-aminoethyl)vindesine, that could be photoactivated . Our studies show the specific labeling of a 150- to 170-kDa protein in membrane vesicles from two independently selected multidrug-resistant KB cell lines, which was not seen in drug-sensitive parental or revertant cell lines . The labeling of the high molecular weight protein was inhibited in a dose-dependent manner by vinblastine with half-maximal inhibition at about 1 microM . Photolabeling was also inhibited by 100 microM vincristine or 100 microM verapamil but not by 100 microM colchicine or 100 microM dexamethasone . The data suggest that the 150- to 170-kDa protein may play an important role in the multidrug-resistance phenotype.

J Biol Chem, 1986 May 15, 261(14), 6137 - 40
Vinblastine photoaffinity labeling of a high molecular weight surface membrane glycoprotein specific for multidrug-resistant cells; Safa AR et al.; Photoactive radioactive analogues of vinblastine were used to photoaffinity label membranes of Chinese hamster lung drug-sensitive (DC-3F), multidrug-resistant sublines selected for resistance to vincristine (DC-3F/VCRd-5L) or actinomycin D (DC-3F/ADX), and revertant (DC-3F/ADX-U) cells . A radiolabeled doublet (150-180 kDa) consisting of a major and minor band which was barely detectable in parental drug-sensitive cells was increased up to 150-fold in the drug-resistant variants but only 15-fold in the revertant cells . Photoaffinity labeling in the presence of 200-fold excess vinblastine reduced radiolabeling of the 150-180-kDa species up to 96%, confirming its Vinca alkaloid binding specificity . The radiolabeled doublet comigrated with a Coomassie Blue stained polypeptide doublet in the drug-resistant cells and was immunoprecipitated with polyclonal antibody which is specific for the 150-180-kDa surface membrane glycoprotein in multidrug-resistant cell lines . The identification of this Vinca alkaloid acceptor in multidrug-resistant plasma cell membranes suggests the possibility of a direct functional role for the 150-180-kDa surface membrane protein in the development of multidrug resistance.

Science, 1986 May 9, 232(4751), 751 - 5
Amplification and expression of genes associated with multidrug resistance in mammalian cells; Scotto KW et al.; In multidrug resistance, which is observed clinically and in tissue culture, cells that are challenged with certain cytotoxic drugs develop resistance not only to the selective agent but also to other, seemingly unrelated, agents . The multidrug-resistant phenotype is associated with DNA sequence amplification and with the overproduction of a number of cytosolic and membrane glycoproteins . The differential amplification and altered expression of at least two related genes, termed multidrug-resistant associated genes has been shown in multidrug-resistant Chinese hamster cells . In multidrug-resistant mouse and human cells, genes homologous to those in Chinese hamster cells are also amplified . The level of expression of these genes varied and did not correlate with their copy number . Furthermore, in Chinese hamster cells, the development of resistance to a single drug and multidrug resistance were closely related, but uncoupled, events . The overexpression of the multidrug-resistant genes was better correlated with the degree of resistance to the selective agent than it was with the extent of multidrug resistance.

Science, 1986 May 2, 232(4750), 643 - 5
Human multidrug-resistant cell lines: increased mdr1 expression can precede gene amplification; Shen DW et al.; The development of simultaneous resistance to multiple structurally unrelated drugs is a major impediment to cancer chemotherapy . Multidrug resistance in human KB carcinoma cells selected in colchicine, vinblastine, or Adriamycin is associated with amplification of specific DNA sequences (the multidrug resistance locus, mdr1) . During colchicine selection resistance is initially accompanied by elevated expression of a 4.5-kilobase mdr1 messenger RNA (mRNA) without amplification of the corresponding genomic sequences . During selection for increased levels of resistance, expression of this mRNA is increased simultaneously with amplification of mdr1 DNA . Increased expression and amplification of mdr1 sequences were also found in multidrug-resistant sublines of human leukemia and ovarian carcinoma cells . These results suggest that increased expression of mdr1 mRNA is a common mechanism for multidrug resistance in human cells . Activation of the mdr1 gene by mutations or epigenetic changes may precede its amplification during the development of resistance.

Mol Cell Biol, 1986 May, 6(5), 1671 - 8
Overexpression and amplification of five genes in a multidrug-resistant Chinese hamster ovary cell line; Van der Bliek AM et al.; Multidrug-resistant cells are cross-resistant to a wide range of unrelated drugs, many of which are used in cancer chemotherapy . We constructed a cDNA library from RNA of the multidrug-resistant Chinese hamster ovary cell line CHRC5 . By differential screening we isolated cDNAs derived from mRNAs that are overexpressed in this cell line . The cDNAs could be grouped in five classes on the basis of transcript lengths detected in RNA blots . We infer that each class codes for a separate protein . The corresponding genes are amplified 10 or 30 times in CHRC5 DNA, providing an explanation for the constitutive overexpression found in this cell line . Despite differential amplification, the genes may be linked in one large amplicon as indicated by the hybridization analysis of large fragments of CHRC5 DNA separated by pulsed field gradient gel electrophoresis . Therefore, some of these genes might be fortuitously coamplified and not contribute functionally to the resistant phenotype . It is also possible, however, that genes involved in drug resistance are clustered . One of our clones cross-hybridized with the recently described cDNA pCHP1 (J . R . Riordan, K . Deuchars, N . Kartner, N . Alon, J . Trent, and V . Ling, Nature {London} 316:817-819, 1985) encoding part of the 170-kilodalton P-glycoprotein, a protein which is frequently overproduced in multidrug-resistant cells . The nature of the four other genes is still unknown . Sequences of four of the five classes of cDNAs are conserved in mouse and human DNA.

Cancer Res, 1986 Apr, 46(4 Pt 2), 1939 - 42
Cross-resistance to intercalating agents in an epipodophyllotoxin-resistant Chinese hamster ovary cell line: evidence for a common intracellular target; Glisson B et al.; Several intercalating agents, as well as the epipodophyllotoxins, appear to effect DNA damage through their interaction with type II DNA topoisomerases . However, the relationship of this phenomenon to anti-tumor activity remains unproven . Our studies with an epipodophyllotoxin-resistant cell line not only provide additional evidence that the enzyme is a multidrug target but also serve to implicate it as a mediator of cytotoxic effect . When compared to wild-type cells, the epipodophyllotoxin-resistant Chinese hamster ovary cell line, VpmR-5, exhibits cross-resistance to both the cytotoxic and DNA cleavage activities of 4',9-acridinylaminomethanesulfon-m-anisidide, mitoxantrone, and Adriamycin . Steady-state concentrations of radiolabeled-4',9-acridinylaminomethanesulfon-m-anisidide and daunomycin are identical in both cell lines . Sharp plateaus in the VpmR-5 dose-response curves for Adriamycin-induced DNA strand breaks and cytotoxicity appear to be related to interference with type II topoisomerase-mediated cleavage of DNA at high concentrations of the intercalator . These data support a direct role for DNA strand scission in cell death and also suggest that multidrug resistance may be acquired by a qualitative change in type II topoisomerase that alters interaction of drug with the enzyme or enzyme-DNA complex.

J Cell Physiol, 1986 Feb, 126(2), 266 - 74
Markedly altered membrane transport and intracellular binding of vincristine in multidrug-resistant Chinese hamster cells selected for resistance to vinca alkaloids; Sirotnak FM et al.; Studies of a multidrug-resistant variant (DC-3F/VCRd-5L) of Chinese hamster lung cells selected for resistance to vinca alkaloids revealed marked alterations in transport and intracellular binding of {3H}vincristine compared to parental DC-3F cells . Influx of {3H}vincristine in DC-3F cells appears to be an equilibrating, but mediated, process . Although saturation kinetics for {3H}vincristine influx were not demonstrated, an extremely high temperature-dependence (Q10 27-37 degrees C = 5-6) and trans-inhibition of influx following preloading of cells with nonradioactive vincristine argue in favor of a carrier-mediated process . Efflux of {3H}vincristine from parental cells conformed to first-order kinetics (t1/2 37 degrees = 3.6 +/- 0.4) and exhibited a lower temperature-dependence (Q10 27-37 degrees C = 3-3.5) than influx . In variant vs . parental cells, influx of {3H}vincristine was reduced 24-fold and efflux was increased two-fold, accounting for the large (approximately 48-fold) reduction in steady-state level of exchangeable drug accumulating in variant cells . Otherwise, transport of {3H}vincristine in these cells showed characteristics similar to parental DC-3F cells . Also, the rate and amount of intracellular binding of {3H}vincristine in variant cells was almost 40-fold lower than in parental cells . These alterations in influx and efflux of {3H}vincristine and its intracellular binding appear to account, at least to a major extent, for the high level of resistance (2,750-fold) of this variant to vinca alkaloids . In contrast, cross-resistance of this variant to daunomycin (178-fold) could be explained only minimally by a transport alteration . Only a two-fold increase in efflux of {3H}daunomycin was demonstrated in variant vs . parental cells along with some decrease in intracellular binding . Influx of {3H}daunomycin was unaltered . In view of these results, we conclude that these two agents most likely do not share the same route for entry in these cells but might share the same efflux route.

Jpn J Cancer Res, 1986 Feb, 77(2), 197 - 204
Non-antitumor vinca alkaloids reverse multidrug resistance in P388 leukemia cells in vitro; Inaba M et al.; Twelve monomeric or dimeric alkaloids from Vinca rosea Linn., which had been reported to have little or no antitumor activity, were investigated to determine their combined effects with either vincristine or daunorubicin on in vitro cell growth of a P388 subline resistant to vincristine and cross-resistant to anthracyclines . We found that the combinations at subcytotoxic concentrations induced significant growth inhibition of the resistant cells, but not of the sensitive cells . Of the alkaloids examined, catharine, vindoline, catharanthine, vincarodine, and lochnerine were able to bring about complete inhibition of cell growth . Further in vitro study using vindoline revealed that at 10 micrograms/ml it was able to completely reverse not only resistance to vincristine but also cross-resistance to vinblastine, daunorubicin, and adriamycin . In addition, we found that vinca alkaloids active in reversing resistance possess potent activities to enhance the net uptake of not only vincristine but also daunorubicin by the resistant cells, and this effect was proved to result from their inhibitory action on the active efflux process . These results provide further support for our hypothesis that both anthracyclines and vinca alkaloids can inhibit their own efflux process by interacting with the cell membrane, and this similarity provides a basis for their reciprocal cross-resistance, irrespective of their different chemical structures.

FEBS Lett, 1986 Jan 20, 195(1-2), 275 - 9
Identification of a novel calcium-binding protein (CP22) in multidrug-resistant murine and hamster cells; Koch G et al.; Analysis of cytoplasmic extracts of multidrug-resistant murine and hamster cells by SDS gel and 2D gel electrophoresis showed that they expressed an abundant 22 kDa protein which was absent from the drug-sensitive parent lines . SDS gel electrophoresis in the presence of EGTA and direct binding tests with 45Ca2+ showed that the resistance-associated protein is a specific calcium-binding protein . Thus the development of multidrug resistance in both colchicine-selected hamster cells and adriamycin-selected murine cells is associated with a major change in calcium metabolism . These observations provide the first molecular basis for the hypothesis that Ca2+ plays a central role in the development of the multidrug resistance phenomenon.

Prog Clin Biol Res, 1986, 223, 163 - 71
Techniques to reverse or circumvent drug-resistance in vitro; Kuwano M et al.; In this study, we report that membrane-active agents can reverse or circumvent multidrug resistance in tumor cells through alteration of membrane permeability . Two different cell lines are used to assay the drug-sensitivity: colchicine-resistant clone derived from human cancer KB cell line with multidrug resistance and P388 leukemia cells resistant to many anticancer agents such as adriamycin, vincristine and other agents . In the latter system, circumvention effect can be tested with mice bearing drug-sensitive or -resistant P388 leukemia in vivo . Thioridazine (calmodulin inhibitor), N-(p-methylbenzyl)decaprenylamine, N-solanesyl-N,N'-bis(3,4-dimethoxybenzyl)ethylenediamine and amphotericin B (a sterol-binding polyene antibiotic) have been screened with these two drug-resistant cell systems . They overcome the multidrug resistance in Chr-24 as well as P388 leukemia cells resistant to adriamycin or vincristine . N-solanesyl-N,N'-bis(3,4-dimethoxylbenzyl)ethylenediamine can reverse the drug-resistance in vivo against mice bearing resistant leukemia . Mechanism to reverse the drug-resistance is to be discussed in relation with altered membrane permeability of the anticancer agents.

Cancer Chemother Pharmacol, 1986, 17(3), 259 - 63
Rapid chemosensitivity testing of human lung tumor cells using the MTT assay; Cole SP; Numerous procedures have been described which test the chemosensitivity of tumor cell lines . A major disadvantage of most of these assays is that practical limitations prevent the testing of more than a few variables . We have adapted a rapid and efficient colorimetric assay for testing the chemosensitivity of human lung tumor cells . In this assay, a tetrazolium salt (3-{4,5-dimethylthiazol-2-yl}-2,5-diphenyl-tetrazolium bromide, MTT) is converted to a colored formazan product by enzymes active only in living cells . The MTT assay may be carried out entirely in 96-well microtiter plates, so that large experiments examining a number of variables can be readily performed . Thus, drug concentration, time of exposure to drug, length of assay, and cell density can be varied and tested . Moreover, the simplicity of this assay allows simultaneous testing of multiple drugs on multiple cell lines . Finally, the MTT assay is useful for monitoring the development of multidrug-resistant cells in culture.

Invest New Drugs, 1986, 4(4), 359 - 65
Spirogermanium--a novel antitumour agent expressing a lack of cross-resistance in vitro with a range of 'standard' antitumour drugs; Hill BT et al.; We have used a series of drug resistant continuous tumour cell lines of murine, hamster or human origin, to screen in vitro for new drugs effective at overcoming resistance expressed to clinically useful antitumour drugs . We have established that spirogermanium appears to express a unique lack of cross resistance to a wide range of 'standard' antitumour drugs including 5-fluorouracil, cisplatin, methotrexate, vincristine and adriamycin, as judged by its equivalent effectiveness in reducing survival, measured by clonogenic assays, of the parental and drug-resistant sublines following 24 hour in vitro treatments . Spirogermanium was also able to overcome the multidrug resistance exhibited by the colchicine-resistant mutant CHRC5 cells and a subline of vincristine-resistant MCF-7 human breast carcinoma cells, following 1 or 24 hour drug treatments . These preclinical studies suggest that this novel compound may prove a potentially useful agent for inclusion in 'non-cross-resistant drug combinations'.

Prog Clin Biol Res, 1986, 223, 203 - 16
Acquired vs innate multidrug resistance and the effect of calcium channel blockers; Tsuruo T; Innate drug resistance as well as acquired multidrug resistance are directly related to ineffectiveness and failure of the cancer chemotherapy . The mechanisms of such resistance, especially those of innate resistance, have not been fully elucidated . We have established vincristine (VCR)- and Adriamycin (ADM)-resistant sublines of human myelogenous leukemia K562 by continuous drug exposure . These resistant sublines contained double minute chromosomes and express a glycoprotein with a 180,000 dalton M.W . Analysis of VCR and ADM sensitivities of several isolated clones from these resistant sublines revealed a tight relationship between these two resistant mechanisms . However, ADM resistant sublines are always highly resistant to VCR, but VCR resistant sublines are not necessarily highly resistant to ADM, suggesting the presence different mechanisms of ADM and VCR resistance . Calcium channel blockers inhibit the drug efflux in these resistant tumor cells, thereby overcoming of drug resistance . Greater potentition was observed with antitumor agents to which VCR- and ADM-resistant cells were highly cross-resistant . Calcium channel blockers always show higher potentiation with VCR than ADM, and the clones with greater resistance to VCR generally accumulated less VCR and generally possessed a higher rate of VCR efflux . These results might indicate that a major mechanism of VCR resistance could be a defficiency in drug transport and this mechanism can be reversed by calcium channel blockers, while the ADM resistance mechanisms are partly related to drug efflux and only this mechanism of the ADM resistance can be modulated by calcium channel blockers . Calcium channel blockers also potentiate the drug effects, especially that of vinca alkaloids, in innately resistant tumors cells, indicating that such innate resistant cells also share a similar resistance mechanism to that observed in acquired drug resistance . From these results, the mechanisms of acquired and innate drug resistance are discussed.

Proc Natl Acad Sci U S A, 1986 Jan, 83(2), 337 - 41
Isolation and characterization of DNA sequences amplified in multidrug-resistant hamster cells; Gros P et al.; The mechanism by which mammalian cells acquire resistance to chemotherapeutic agents has been investigated by using molecular genetic techniques . LZ and C5, two independently derived multidrug-resistant Chinese hamster cell lines, share specific amplified DNA sequences . We demonstrate that commonly amplified DNA sequences reside in a contiguous domain of approximately equal to 120 kilobases (kb) . We report the isolation of this DNA domain in cosmid clones and show that the level of amplification of the domain is correlated with the level of resistance in multidrug-resistant cell lines . The organization of the amplified domain was deduced by a unique approach utilizing in-gel hybridization of cloned DNA with amplified genomic DNA . We show that the entire cloned region is amplified in adriamycin-resistant LZ cells and independently derived, colchicine-resistant C5 cells . A mRNA species of approximately equal to 5 kb is encoded by a gene located within the boundaries of this region . Genomic sequences homologous to the 5-kb mRNA span over 75 kb of the amplified DNA segment . The level of expression of this mRNA in multidrug-resistant cells is correlated with the degree of gene amplification and the degree of drug resistance . Our results strongly suggest that the 5-kb mRNA species plays a role in the mechanism of multidrug resistance common to the LZ and C5 cell lines.

Trans R Soc Trop Med Hyg, 1986, 80(5), 753 - 7
Synergy of four macrolide antibiotics with chloroquine against chloroquine-resistant Plasmodium falciparum in vitro; Gershon P et al.; The antimalarial activity of four macrolide antibiotics was investigated against the multidrug resistant K1 strain of Plasmodium falciparum in vitro . ID50 (50% inhibitory concentration) values for erythromycin, spiramycin, tylosin tartrate and oleandomycin phosphate in 48-hour assays were 1.6 X 10(-4)M, 2.5 X 10(-5)M, 1.2 X 10(-5)M and 9 X 10(-6)M respectively, and in 96 hour assays were 10(-5)M, 2.6 X 10(-6)M, 2.6 X 10(-6) and 3 X 10(-6)M, respectively . Comparable values were obtained in assays in which drug effect was quantified from either parasite counts or 14C isoleucine incorporation . Each of the four macrolides displayed synergy with chloroquine at the IC90 (90% inhibitory concentration) level, but at the IC50 level synergy was either less pronounced or absent . For each combination this difference in the degree of synergy was significant at the 95% level of confidence . In replicate assays in which 3H hypoxanthine was the marker of drug effect, synergy between chloroquine and either erythromycin or spiramycin could not be detected.

Cancer Surv, 1986, 5(1), 25 - 46
Multidrug resistance; Gerlach JH et al.; Multidrug resistance describes a complex phenotype whose predominant feature is resistance to a wide range of structurally unrelated cytotoxic compounds, many of which are anticancer agents . This phenotype occurs frequently in mammalian cell lines and transplantable tumours selected for resistance to a single drug . Reduced cellular accumulation of the drugs involved appears to account for the resistance . This may be a consequence of reduced drug influx, increased drug efflux, or both . A wide variety of biochemical changes have been identified in multidrug resistant cell lines, the most consistent of which is the increased expression of P-glycoprotein, a conserved, high molecular weight, plasma membrane glycoprotein . The level of P-glycoprotein expression correlates with the degree of drug resistance in a variety of different cell types . In a number of multidrug resistant cell lines, overexpression of P-glycoprotein results from gene amplification . While the function of P-glycoprotein is unknown, independent lines of evidence support the notion that P-glycoprotein is the causative molecule mediating the multidrug resistance phenotype . Significant levels of P-glycoprotein expression have been detected in some biopsy specimens from patients with ovarian and sarcoma tumours . These findings suggest that multidrug resistant tumour cells can occur in human malignancies . The presence of such cells may affect the outcome of chemotherapy.

J Clin Microbiol, 1985 Dec, 22(6), 919 - 23
Interlaboratory drug susceptibility testing of Mycobacterium tuberculosis by a radiometric procedure and two conventional methods; Siddiqi SH et al.; A total of 224 recent isolates of Mycobacterium tuberculosis from 163 patients selected to have multidrug resistance were tested against streptomycin (SM), isoniazid, rifampin, and ethambutol (EMB) by the rapid radiometric BACTEC method and two conventional proportion methods: the World Health Organization (WHO) method, using Lowenstein-Jensen medium; and the Veterans Administration reference laboratory for mycobacteria (VA) method, using Middlebrook 7H10 agar medium . The results were compared, focusing on the concentrations of the drugs in all three methods . Among the four drugs tested, most of the discrepancies in measured activity were observed with SM and EMB, generally because of differences in the drug concentrations used by the three methods . A 4-micrograms amount of SM in the BACTEC method was found to be slightly less active than 10 micrograms in the VA method and significantly more active than 4 micrograms of dihydrostreptomycin in the WHO method . With EMB, 2.5 micrograms in BACTEC was similar to 5 micrograms in the VA method and 2 micrograms in the WHO method, while 10 micrograms in the BACTEC method was found to be more active than 10 and 2 micrograms in the VA and WHO methods, respectively . To attain close agreement, drug concentrations used in the BACTEC method should be carefully selected when a comparison is to be made with any conventional method employed in a laboratory . Standardization of in vitro susceptibility testing is greatly needed to achieve uniformity among the test methods used to evaluate tuberculosis therapeutics.

Proc Natl Acad Sci U S A, 1985 Nov, 82(22), 7661 - 5
Amplification of DNA sequences in human multidrug-resistant KB carcinoma cells; Fojo AT et al.; Four KB carcinoma cell lines selected independently for resistance to either colchicine, adriamycin, or vinblastine were studied . All cell lines showed high levels of resistance to the selecting drug and cross-resistance to the other drugs and to actinomycin D . Double-minute chromosomes could be identified on chromosomal spreads of these multidrug-resistant KB cell lines . Amplification of specific DNA sequences was demonstrated by using the technique of in-gel renaturation . All the cell lines share common amplified sequences . There are also amplified sequences that are specific for each cell line . A revertant cell line that has reacquired drug sensitivity has lost its amplified sequences . Specific probes obtained by cloning amplified sequences from the cell line selected in vinblastine recognize amplified sequences in all the resistant lines . The presence of common amplified sequences in these cell lines is strong evidence for the importance of these regions in multiple drug resistance.

Cancer Res, 1985 Oct, 45(10), 5064 - 9
Immunological detection of Chinese hamster ovary cells expressing a multidrug resistance phenotype; Lathan B et al.; A monoclonal antibody (IgG1) has been prepared that specifically detects Chinese hamster ovary cells expressing a multidrug-resistant phenotype . This antibody recognizes the membrane P-glycoprotein (Mr 170,000) associated with drug resistance as determined by enzyme-linked immunosorbent assay with purified P-glycoprotein and by Western blot analysis of cell extracts from drug-resistant and drug-sensitive cells . By immunofluorescence methods, the antibody also reacts strongly with viable and ether:ethanol-fixed resistant cells but does not react with the parent drug-sensitive cell line . Thus, this antibody can bind with live cells allowing discrimination by immunohistochemistry between drug-resistant and drug-sensitive Chinese hamster ovary cells.

Cancer Res, 1985 Sep, 45(9), 4091 - 6
Multidrug (pleiotropic) resistance in doxorubicin-selected variants of the human sarcoma cell line MES-SA; Harker WG et al.; The emergence of drug-resistant tumor cells is a major limiting factor in cancer chemotherapy . There is little information about the nature of such resistant variants among human cancer cell populations . Doxorubicin (DOX)-resistant sublines of the human sarcoma cell line MES-SA were selected by continuous in vitro exposure to DOX . Stepwise increases in DOX concentration produced variants which were 25- and 100-fold resistant to DOX . These sublines displayed marked cross-resistance to daunorubicin, dactinomycin, mitoxantrone, colchicine, vincristine, vinblastine, and etoposide and moderate resistance to mitomycin C and melphalan . Cross-resistance was not observed, however, to methotrexate, 5-fluorouracil, bleomycin, carmustine, or cisplatin . DOX resistance in these cell lines appeared to be stable despite long periods of growth in drug-free medium . Two additional marker chromosomes were identified in the 100-fold resistant variant, which indicated clonal selection during drug exposure, but no double minute chromosomes or homogeneously staining regions were noted . Doxorubicin accumulation in the DOX-resistant cells was reduced by approximately 50% compared to that of the sensitive MES-SA cells, as a result of enhanced efflux of DOX from the resistant cells . There was no evidence of appreciable DOX metabolism by either the sensitive or resistant cells . These studies demonstrate marked DOX resistance and multidrug resistance arising in a human sarcoma line during exposure to DOX . The pleiotropic nature of this resistance is similar to that described in other models . Decreased drug accumulation due to enhanced drug efflux is identified as a major mechanism of resistance in these cells, although other factors may also be involved.

Gan To Kagaku Ryoho, 1985 Sep, 12(9), 1715 - 25
{Antitumor drug resistance and therapeutic approaches to reverse resistance}; Tsuruo T; Acquired multidrug resistance as well as innate drug resistance are directly related to ineffectiveness and failure of the cancer chemotherapy . The mechanisms of such resistance, especially those of innate resistance, have not been fully elucidated . Drug resistant tumor cells, however, usually bear biochemical changes which are related to resistance mechanisms . New modalities with high selectivity against resistant cells could, therefore, be possible if we could target these biochemical changes . Vincristine (VCR)-and adriamycin (ADM)-resistant tumor cells (pleiotropic drug resistant cells) usually show an enhanced outward transport of these antitumor agents, and they express unique glycoproteins in the plasma membrane . By targeting for these biochemical changes characteristic to the resistant tumor cells, we establish new modality which shows high selectivity against drug resistant tumor cells . In this review, I will describe genetic origin of drug resistance, biochemical mechanisms of drug resistance and reversal of drug resistance in tumor cells . The modality to utilize calcium channel blockers which inhibit the enhanced outward transport of VCR and ADM from resistant tumor cells will be reviewed.

Nature, 1985 Aug 29-Sep 4, 316(6031), 817 - 9
Amplification of P-glycoprotein genes in multidrug-resistant mammalian cell lines; Riordan JR et al.; The multidrug-resistance phenotype expressed in mammalian cell lines is complex . Cells selected with a single agent can acquire cross-resistance to a remarkably wide range of compounds which have no obvious structural or functional similarities . The basis for cross-resistance seems to be a decreased net cellular accumulation of the drug involved, and has been attributed to alterations in the plasma membrane . An over-expressed plasma membrane glycoprotein of relative molecular mass (Mr) 170,000 (P-glycoprotein) is consistently found in different multidrug-resistant human and animal cell lines, and in transplantable tumours . Consequently, it has been postulated that P-glycoprotein directly or indirectly mediates multidrug resistance . Here we report the cloning of a complementary DNA encoding P-glycoprotein . Southern blot analysis of hamster, mouse and human DNA using this cDNA as a probe showed that P-glycoprotein is conserved and is probably encoded by a gene family, and that members of this putative family are amplified in multidrug-resistant cells.

Nature, 1985 Aug 29-Sep 4, 316(6031), 820 - 3
Detection of P-glycoprotein in multidrug-resistant cell lines by monoclonal antibodies; Kartner N et al.; One reason for the failure of chemotherapy in the treatment of advanced cancers may be the outgrowth of multidrug-resistant tumour cells . Multidrug resistance has been modelled in numerous mammalian cell lines in which the phenotype is characterized by a pleiotropic cross-resistance to unrelated drugs . In the study reported here, we have produced monoclonal antibodies whose binding to plasma membranes of different multidrug-resistant mammalian cells correlates with the degree of drug resistance . All these antibodies are specific for P-glycoprotein, a cell surface component of relative molecular mass (Mr) 170,000 (170K) that has been described previously, and are directed against three spatially distinct epitopes which define a conserved cytoplasmic domain in the C-terminal region of the P-glycoprotein polypeptide . The conserved nature of P-glycoprotein and its low-level expression is drug-sensitive cells suggest that it has an important function at the cell surface . The monoclonal antibodies against P-glycoprotein described here might serve as diagnostic reagents for clinically unresponsive tumours.

Am J Trop Med Hyg, 1985 Jul, 34(4), 692 - 3
Mefloquine failure in a case of falciparum malaria induced with a multidrug-resistant isolate in a non-immune subject; Cosgriff TM et al.; In a volunteer with infection induced by injection of the mefloquine-sensitive, multidrug-resistant Vietnam Smith isolate of P . falciparum, parasitemia recurred following treatment with the candidate antimalarial drug enpiroline . Parasitemia also recurred after subsequent treatment with mefloquine and again after retreatment with the same drug . All recurrences were at the RI level . Parasite drug sensitivities determined by a semi-automated isotope microdilution method after the second and third recurrences revealed a progressive decrease in sensitivity to all arylaminoalcohols tested (halofantrine, enpiroline, and mefloquine) . Decreased sensitivity persisted after 30 days of isolate culture . The parallel changes in parasite sensitivity to the synthetic arylaminoalcohols argue for development of drugs which are chemically dissimilar.

Am J Trop Med Hyg, 1985 Jul, 34(4), 675 - 80
Sensitivity of Plasmodium falciparum to antimalarial drugs in Colombia; Espinal CA et al.; Sensitivity of Plasmodium falciparum to several antimalarial drugs was determined by in vitro and in vivo tests . Chloroquine resistance in vitro was detected in 97 of 101 patients from different geographic areas of Colombia . Sensitivity to amodiaquine in vitro was observed in 29 of 30 P . falciparum isolates . In vitro sensitivity to amodiaquine was observed in 16 patients infected with chloroquine-resistant P . falciparum . In vitro sensitivity to quinine was demonstrated in 57 P . falciparum isolates . Two infections from the Amazon base (2/24) were resistant to mefloquine in vitro at concentrations of 5.7 and 16 pmol/well . Resistance to Fansidar, a sulfadoxine-pyrimethamine combination, was described in 9 patients from the Amazon region . One patient showed recrudescence of the infection 41 days after treatment . The current distribution and degree of resistance of P . falciparum to widely used antimalarial drugs requires the evaluation of therapeutic schemes based on combinations of fast blood schizontocides with slow acting drugs . These associations may reduce the development of multidrug-resistant isolates and retard the spread of resistant populations of P . falciparum parasites.

Antimicrob Agents Chemother, 1985 Jun, 27(6), 892 - 6
Inducible phenotypic multidrug resistance in the fungus Mucor racemosus; Leathers TD et al.; The dimorphic fungus Mucor racemosus exhibited a single-step, inducible resistance to cycloheximide, trichodermin, and amphotericin B . Cells adapted to inhibitory levels of the antibiotics after 12 to 40 h . The adaptation involved all the cells in the population and was not the result of the selection of resistant mutants . Adaptation to one drug provided cross resistance to other, dissimilar drugs . Resistance was lost within several generations of growth in the absence of the inhibitors.

J Clin Oncol, 1985 Mar, 3(3), 311 - 5
Detection of P-glycoprotein in ovarian cancer: a molecular marker associated with multidrug resistance; Bell DR et al.; A multidrug resistance phenotype is frequently observed in animal and human cell lines selected for in vitro resistance to a single chemotherapeutic agent . Overexpression of a highly conserved cell-surface glycoprotein (P-glycoprotein) is consistently associated with this phenotype in these mutant lines . A monoclonal antibody against P-glycoprotein was used to examine tumor samples from five patients with advanced ovarian cancer for evidence of P-glycoprotein overexpression . High levels of P-glycoprotein were detected in samples from two patients suggesting that a multidrug resistance mutation may also occur in ovarian cancer . This finding has broad implications for the understanding of nonresponse to chemotherapy in a variety of human neoplasms, and may provide a rational explanation for failure of chemotherapy in treatment of advanced ovarian cancer.

Eur Urol, 1985, 11(3), 163 - 9
Bulky germinal tumors: comparison of different induction regimens and significance of residual disease; Kreuser ED et al.; In order to study the efficacy of three different chemotherapy regimens and the prognostic significance of residual disease after chemotherapy, we analyzed 84 patients with bulky germinal tumors . Chemotherapy, consisting of vinblastine, bleomycin/adriamycin, cisplatin (VB/AP) was administered sequentially to 37 patients . 19 patients were treated with the cisplatin, vinblastine, bleomycin (PVB) regimen and 17 patients with cisplatin, vinblastine, bleomycin, ifosfamide (PVBI) . The initial complete remission (iCR) was 71% (52 of 73) with a relapse rate of 29% (15 of 52) . 10 of 73 (14%) patients achieved partial response and 11 of 73 (15%) showed progression due to multidrug resistance . There was no statistically significant difference in iCR, continuous complete remission (cCR), relapse and survival between the PVB, PVBI and VB/AP regimens . In 50 patients, the residual tumor after chemotherapy was examined histologically . cCR was achieved in 75% (15 of 20) of patients with necrosis or fibrosis, in 50% (5 of 10) with adult teratoma and in 25% (5 of 20) with malignant tumor . Comparison of survival curves according to residual histology revealed statistically significant differences (p = 0.02) . Our findings suggest that in patients with germinal bulk disease PVBI-regimen and VB/AD-therapy are not superior to the standard regimen . Residual disease seems to be an important prognosticator.

Gann, 1984 Dec, 75(12), 1049 - 52
Reversal of multidrug resistance by non-antitumor anthracycline analogs; Inaba M et al.; It was found that three synthetic anthracycline analogs lacking not only antitumor activity but also calcium-antagonizing action possessed an activity to potentiate vincristine cytotoxicity against vincristine-resistant P388 leukemia . ID-8279, one of these analogs, significantly reversed resistance to vincristine and daunorubicin by increasing their intracellular accumulation.

Orthop Clin North Am, 1984 Jul, 15(3), 417 - 25
Emerging patterns of microbial resistance; Washington JA 2nd; Microbial resistance arises by mutation or by inheritance . The latter is plasmid-mediated and transferable and may erode multidrug resistance to beta-lactams, aminoglycosides, tetracyclines, macrolides, lincosamides, sulfonamides, and trimethoprim . Resistance genes may transfer from one plasmid to another or from a plasmid to the chromosome or to a bacteriophage, thereby allowing rapid dissemination of resistance among bacteria . Mutational or chromosomal resistance is not readily transferable between different bacterial species or genera but is nonetheless medically important for resistance to isoniazid, methicillin, nalidixic acid, rifampin, and expanded spectrum cephalosporins.

Chest, 1984 Mar, 85(3), 440 - 1
Emergence of multidrug-resistant Mycobacterium fortuitum during treatment; Martin ML et al.; We present a case of pulmonary infection with Mycobacterium fortuitum demonstrating the development of multidrug resistance during therapy with multiple drugs . Emergence of drug resistance in a previously sensitive M fortuitum has been described with single drug therapy, but never before with multiple drug treatment . Development of resistance in the setting of multiple drug therapy illustrates the importance of repeated susceptibility testing during therapy.

Cancer Treat Rev, 1984 Mar, 11 Suppl A, 85 - 98
Studies on drug resistance in a human melanoma xenograft system; Osieka R; Alkylating agents and their functional analogues belong to the most useful antineoplastic drugs in the treatment of disseminated malignant melanoma . In conjunction with an open clinical phase II trial evaluating the combination of cisplatin and ifosfamide, 17 melanoma xenograft lines were established from patients often refractory to dacarbazine (DTIC) . These xenograft lines were exposed to cisplatin, dacarbazine, dibromodulcitol, ifosfamide, methyl-CCNU, mitomycin C, and malonato-diaminocyclohexane-platinum II (PHM) at the respective LD 10/30 doses . Growth delay values less than 2 corresponded in 26/27 instances with progressive disease, whereas values greater than 2 corresponded in only 10/13 instances with achievement of a no-change status or a partial remission of the donor patient's disease . Among the panel of DNA-damaging agents tested, cross-resistance was incomplete . Some xenograft lines revealed unique chemosensitivity patterns in contrast to a uniform pattern of drug resistance in others (pleiotropic or multidrug resistance) . The data confirm independently of results obtained in the phase II study that the combination of cisplatin and ifosfamide is effective against malignant melanoma refractory to dacarbazine . Suboptimal drug exposure, repeated up to 21 transplant generations, was employed to induce secondary resistance to either dacarbazine, melphalan or methyl-CCNU in a melanoma xenograft line originally quite sensitive to drug treatment . When the resistant sublines were exposed to the other agents, only partial cross-resistance was observed . Tumour volume responses to treatment with dacarbazine correlated with persisting DNA damage assayed 24 h after in vivo drug exposure in a sensitive line and the absence of such lesions in a resistant line.

Cancer Chemother Pharmacol, 1984, 13(2), 145 - 7
Expression of cell surface P-glycoprotein by an adriamycin-resistant murine fibrosarcoma; Giavazzi R et al.; Analysis of the cell membrane of Adriamycin (doxorubicin)-resistant UV-2237 ADMR murine fibrosarcoma cells revealed a 170,000-dalton component that is not found in the drug-sensitive parent or revertant cells . Immunoblot (Western blot) analysis showed that this component is similar to the 170,000-dalton P-glycoprotein found on the surface of Chinese hamster ovary cells that exhibit multidrug resistance . Thus, multidrug resistance and P-glycoprotein expression apparently can occur in a wide variety of cells, including the metastatic murine solid tumor cell line described here.

Breast Cancer Res Treat, 1984, 4(2), 89 - 94
Multidrug resistance; Ling V et al.; Mutations resulting in a complex phenotype of cross-resistance and collateral-sensitivity are frequently observed in mammalian cell lines . A cell surface 170 000 dalton glycoprotein (P-glycoprotein) has been identified to be intimately associated with this multidrug resistance phenotype . We speculate that such mutations also occur in advanced cancers and play a major role in contributing to the non-response to combination chemotherapy . In this context, P-glycoprotein may be a useful molecular marker for diagnostic and therapeutic applications.

Cancer Treat Rep, 1983 Oct, 67(10), 869 - 74
Multidrug-resistance phenotype in Chinese hamster ovary cells; Ling V et al.; Multidrug resistance is a complex pleiotropic phenotype of cross-resistance and collateral sensitivity to unrelated compounds observed in many mammalian cell mutants selected for resistance to single agents . In Chinese hamster ovary cells, colchicine-resistant mutants expressing this phenotype have been characterized extensively . Such mutants arise apparently from a single genetic event, and the basis of this phenotype appears to be localized at the membrane level, resulting in altered drug permeability . Expression of a 170,000-dalton surface glycoprotein (P-glycoprotein) has been identified to correlate with the multidrug-resistance phenotype . Selection of a second mutation in colchicine-resistant mutants, for resistance to phytohemagglutinin, results in an alteration of the carbohydrate moiety in P-glycoprotein and other surface components . This mutation does not noticeably affect the multi-drug-resistance phenotype . The altered permeability of mutant cells to drugs, however, can be modulated by nonionic detergents or metabolic inhibitors . These findings are consistent with a molecular mechanism of multidrug resistance whereby the pleiotropic response of the cell is mediated by an overexpression of a cell-surface protein, the P-glycoprotein.

Cancer Treat Rep, 1983 Oct, 67(10), 883 - 8
Evidence for multidrug-resistant cells in human tumor cell populations; Shoemaker RH et al.; Data are presented from two cell culture systems which support the notion that a multi-drug-resistant phenotype occurs in human tumor cell populations . Human small cell lung cancer cell lines derived from patients in relapse following intensive combination chemotherapy demonstrate broad cross-resistance to nine standard drugs in vitro . However, analysis of {14C}glucosamine-labeled glycoproteins in the small cell lung cancer cell lines failed to identify any consistent association between a specific glycoprotein marker and the drug-resistant phenotype . Evaluation of drug sensitivity of human tumor cells in primary culture (colony-forming assay) has indicated that multidrug-resistant cells may be present in tumor cell populations even in the absence of prior drug therapy . Several features of the multidrug-resistant phenotype, as observed in these human tumor cell populations, differ from those observed in Chinese hamster cell systems . In particular, the variability in patterns of resistance to various agents and in expression of glycoprotein markers suggests that a substantial amount of genetic heterogeneity underlies this phenotype in human tumors.

Science, 1983 Sep 23, 221(4617), 1285 - 8
Cell surface P-glycoprotein associated with multidrug resistance in mammalian cell lines; Kartner N et al.; The plasma membranes of hamster, mouse, and human tumor cell lines that display multiple resistance to drugs were examined by gel electrophoresis and immunoblotting . In every case, increased expression of a 170,000-dalton surface antigen was found to be correlated with multidrug resistance . This membrane component is of identical molecular size and shares some immunogenic homology with the previously characterized P-glycoprotein of colchicine-resistant Chinese hamster ovary cells . This finding may have application to cancer therapy.

Cancer Res, 1983 Sep, 43(9), 4413 - 9
Daunorubicin-resistant Chinese hamster ovary cells expressing multidrug resistance and a cell-surface P-glycoprotein; Kartner N et al.; Independent lines of Chinese hamster ovary cells resistant to the antineoplastic drug, daunorubicin, were obtained by clonal isolation in increasing drug concentrations . A single daunorubicin-resistant phenotype typified by reduced cellular drug accumulation was observed . These mutants displayed a complex phenotype of resistance to a variety of unrelated drugs . Such properties are similar to those of membrane-altered colchicine-resistant lines (V . Ling and L.H . Thompson, J . Cell . Physiol., 83: 103-116, 1974) . Analysis of the plasma membrane components of the daunorubicin-resistant clones by gel electrophoresis revealed a prominent cell surface glycoprotein with a molecular weight of about 170,000 . This component was immunologically cross-reactive with the cell surface P-glycoprotein of about the same molecular weight, previously identified in colchicine-resistant cells . Thus, it appears that the mechanism of resistance characterized by P-glycoprotein expression could be the basis of many drug-resistant phenotypes.

Annu Rev Med, 1983, 34, 321 - 35
Falciparum malaria: the urgent need for safe and effective drugs; Rieckmann KH; The spread of multidrug-resistant strains of Plasmodium falciparum poses an increasing threat to the effective treatment and prophylaxis of malaria . Recent advances in determining the drug sensitivity of malaria parasites should promote the more rational use of standard or alternative antimalarials in areas with emerging or well-established drug resistance . The use of currently available alternative drugs is usually associated with more problems than that of the standard, synthetic antimalarials . Safe and effective drugs, capable of being administered as a single-dose or short-course treatment, are urgently needed to control the adaptable malaria parasite.

Am Rev Respir Dis, 1982 Dec, 126(6), 1092 - 5
Drug-resistant Mycobacterium tuberculosis in Korean isolates; Carpenter JL et al.; Tuberculosis is a common disease in developing countries . An increasing incidence of resistance to isoniazid (INH) and streptomycin in organisms isolated from patients who contracted their disease in these countries, particularly in the Far East, is well recognized . This drug resistance has led to the recommendation of empirically beginning a regimen in patients with tuberculosis from the Far East of INH, ethambutol, and rifampin . This report documents the increasing incidence of resistance in isolates from Korea to ethambutol and rifampin in addition to INH and streptomycin . It suggests that the empiric use of INH, ethambutol, and rifampin in this group of patients could potentially lead to resistance to all of these drugs because of a significant amount of multidrug resistance . A regimen of INH, rifampin, pyrazinamide, and capreomycin is suggested as appropriate initial therapy in these patients based on the in vitro sensitivity data presented and initial clinical experience.

Pathol Biol (Paris), 1982 Jun, 30(6 Pt 2), 589 - 92
{Mefloquine in the treatment and prevention of malaria }; Danis M et al.; Mefloquine (WR 142,490 or Ro 21,5998) is a new antimalarial drug, 4-quinoline methanol derivative, with a prolonged half-life in man and a good activity against multidrug resistant P . falciparum strains . Tolerance and pharmacokinetic evaluated in 8 black African subjects, is according to previously studies in American or Asian patients: the mean whole blood half-life is 15,6 days . Efficiency of various regimens (1 g in 3 days; 1,50 g in 3 intakes, one day; 25 mg per kg in one intake) was studied on 39 patients, infected by african strains of P falciparum in 26 cases . Fever and parasitemia disappeared within 3 days in all cases . Sera from these patients showed a complete inhibition of P . falciparum continuous culture on day 30 at least . The use of mefloquine may be actually reserved for area where resistant strains of P . falciparum are widespread . In African this use, in theory possible, is not warrant.

Vet Med Nauki, 1980, 17(5), 73 - 9
{Elimination of multidrug resistance in E . coli in calves in vivo with rimactan}; Karaivanov L et al.; An experiment was carried out for eliminating the multimedicinal resistance markers of E . coli, populating the intestinal tract of calves, in vivo with rimactan introduced per os, and rationed 10 mg/kg of live weight, once during a period of 8 days . The highest percentage and the longest elimination were observed for the neomycin, the novobiocin and the chlornitromycin resistance markers . The elimination was weaker for the erythromycin, the streptomycin and the kanamycin markers and the weakest was for the penicillin and tetracycline markers . There appeared a difference in the elimination of the resistance markers with the different calves, especially for the markers with a low degree of elimination, depending on the individual peculiarities of the calves . Riphamycin proved to be an eliminating means for the resistance markers of E coli in vivo of calves suffering from enteritis . Alongside with the elimination of the resistance markers, due to the treatment of calves with rimactan, an almost complete recovery was achieved . Rimactan is a reliable means for fighting enteric illnesses with calves, caused by enteropathogenic E . coli.

Am J Trop Med Hyg, 1979 Sep, 28(5), 793 - 807
Studies on the 2,4-diamino-6-substituted quinazolines . II . Activities of selected derivatives against infections with various drug-susceptible and drug-resistant strains of Plasmodium falciparum and Plasmodium vivax in owl monkeys; Schmidt LH; Four 6-thio-, one 6-sulfinyl-, and two 6-sulfonyl-substituted 2,4-diaminoquinazolines were evaluated for capacities to cure established infections with the chloroquine-resistant Vietnam Oak Knoll and pyrimethamine-resistant Malayan Camp-CH/Q strains of Plasmodium falciparum in owl monkeys . As compared with the doses of standard drugs required for cure of infections with drug-susceptible strains or doses of the newly developed aminoalcohols required for cure of either drug-susceptible or drug-resistant strains, each of these quinazolines effected cure of infections with the Oak Knoll strain at a remarkably small daily dose . However, doses required for cure of infections with the Camp-CH/O strain were from 4-48 times those required for cure of infections with the Oak Knoll strain, suggesting that the activities of these quizanolines, like those of 6-amino-substituted derivatives, were compromised by pyrimethamine resistance . This suggestion received support from expanded studies involving WR-158,122 and WR-159,412, the most active of the agents examined, and the multidrug-resistant Vietnam Smith strain of P . falciparum and Vietnam Palo Alto strain of P . vivax, as well as the Oak Knoll and Camp-CH/Q strains . These studies also showed that significant fractions of infections with the Oak Knoll, Camp-CH/Q, and Palo Alto strains treated previously with subcurative doses of the above derivatives failed to respond to doses that regularly cured previously untreated infections . These treatment failures proved to be due to emergence of parasites resistant to the quinazolines.

Am J Trop Med Hyg, 1977 Sep, 26(5 Pt 1), 837 - 49
Quantitative aspects of pyrimethamine-sulfonamide synergism; Schmidt LH et al.; PIP: The experiments described in this report have dealt with the dimensions of therapeutic potentiation achieved when combinations of pyrimethamine and sulfadiazine were administered to rhesus monkeys infected with a drug-susceptible strain of Plasmodium cynomolgi or its pyrimethamine-resistant variant and to owl monkeys infected with strains of P . falciparum and P . vivax of varying degrees of resistance to this pyrimidine . These evaluations showed: 1) that when delivered in combination, the activities of both pyrimethamine and sulfadiazine against infections with any of the above strains were enhanced significantly; 2) that in infections with the Ro and Ro/PM strains of P . cynomolgi and the Vietnam Palo Alto strain of P . vivax, concomitant delivery of the 2 agents resulted in a 32-fold increase in pyrimethamine activity and a 50- to 100-fold increase in the activity of sulfadiazine; 3) that as a result of this synergism, infections with the pyrimethamine resistant Ro/PM and Palo Alto strains could be cured with a fraction of the maximum tolerated dose of this drug; 4) that in marked contrast to the above result, infections with the Malayan Camp and Vietnam Smith strains of P . falciparum could not be cured regularly by combination regimens which included the maximally tolerated dose of pyrimethamine . This poor response has been attributed to the high levels of pyrimethamine-resistance possessed by these strains . It is believed that the comparatively small but not insignificant incidences of treatment failures associated with delivery of pyrimethamine-sulfonamide combinations to both patients and human volunteers infected with multidrug-resistant strains of P . falciparum rest on a similar basis . author's modified

Ann Intern Med, 1975 Feb, 82(2), 219 - 23
Host failure in treatment of malaria with sulfalene and pyrimethamine; Trenholme GM et al.; An individual infected with a multidrug-resistant strain of Plasmodium falciparum failed to respond to treatment with sulfalene and pyrimethamine . Subinoculation studies showed that parasite resistance to the drug combination was not present . Plasma levels of sulfalene and pyrimethamine in this individual were similar to those of three individuals, subinoculated from him, who were cured by the drug combination . Erythrocyte levels of sulfalene in this individual were similar to those in an individual, subinoculated from him, who was cured by the drug combination . After treatment with the drug combination, in vitro tests showed similar antimalarial activity in the serum of this individual in comparison with the serum of this individual in comparison with the serum of an individual subinoculated from him . The failure of this individual to respond to treatment with sulfalene and pyrimethamine is attributed to an undefined host factor (or factors) that appear(s) to be present in his erythrocytes.

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