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PubMed1992

[The recent development and the present status of K+ channel opener].

The development of vasodilator drugs that open the K+ channels in blood vessels has been of great academic and practical interest. The discoveries of the ATP-sensitive K+ channel and the glibenclamide-sensitive K+ channel have promoted these interests. In relation to this channel, the cardioprotective effectiveness of a K+ channel opener (Aprikalim) in doses that did not change haemodynamics or collateral blood flow were demonstrated in infarct dog heart. The effects were antagonized by glibenclamide. Thus, ATP-sensitive K+ channels seem to play an important role in this effect. Clinical evaluations of the K+ channel openers are reviewed. The hypotensive effects of the drugs are well-recognized. At present, however, the clinical usefulness of K+ channel openers has not been accepted widely, because of their side-effects including reflex tachycardia, edema, flushing and headache. An approach to reduce these side-effects is critical if these K+ channel openers are to be used as good hypotensive drugs. The K+ channel opener nicorandil has been evaluated as a highly effective antianginal drug. It seems likely that the clinical benefits of nicorandil result from both its K+ channel opening properties and its ability to stimulate smooth muscle guanylate cyclase. Clinical data on the pure-selective K+ channel opener cromakalim (lemakalim) as an antianginal drug is limited. However, on the basis of the vasodilator profile of this drug, it is expected to be useful for this purpose. The application of K+ channel openers to treat other disorders such as bladder instability is limited because of its hypotensive action.

Animals↗
PubMed1987

Characterization of actinomycin-D-resistant CHO cell lines exhibiting a multidrug-resistance phenotype and amplified DNA sequences.

Actinomycin D (DACT)-resistant sublines of the Chinese hamster ovary cell line CHO-K1 were selected in vitro. Sublines were derived which expressed 5.2-fold (CHO 15DACT) and 35.8-fold (CHO 100DACT) resistance to DACT. The CHO 100DACT subline displayed marked cross-resistance to bleomycin, adriamycin, daunomycin, vinblastine, vincristine, VP 16 and VM 26. No cross-resistance was found to cisplatin or methotrexate. The resistant cells exhibited enhanced (collateral) sensitivity to prednisolone. Combination of prednisolone with vincristine resulted in a pronounced synergistic effect on sensitive cells, whereas in resistant cells the combined effect of both drugs was merely additive. Resistant cells, viably stained with the DNA-specific dye Hoechst 33342, exhibited decreased fluorescence intensities compared to parental cells. In contrast to sensitive cells the resistant sublines did not accumulate the mitochondria-specific dye rhodamine 123. Co-incubation with verapamil, however, effectively enhanced accumulation of the dye. The potential diagnostic value of these fluorescent compounds as marker dyes for the multidrug-resistance phenotype is discussed. Non-toxic doses of verapamil almost completely reversed the resistance to various drugs in CHO 100DACT cells. Specific DNA sequences were amplified in resistant cells, and the increase in resistance was paralleled by a concomitant increase in the copy number of these sequences, suggesting that the corresponding gene may be functionally linked to the multidrug-resistance phenotype.

Animals↗
PubMed1988

Establishment and characterization of cisplatin-resistant sublines of human lung cancer cell lines.

Human lung cancer sublines resistant to cisplatin (CDDP) have been developed by continuously exposing cells to gradually increasing doses of CDDP and use of the limiting dilution technique. The cell lines used were PC-7, PC-9 and PC-14 (pulmonary adenocarcinoma) and H69 and N231 (small-cell lung cancer). The resistant phenotype of the resistant sublines was stable for more than 2 months in the absence of drug. PC-7/1.2 (i.e., PC-7 cells growing stably in medium containing 1.2 micrograms/ml of CDDP), PC-9/0.5, PC-14/1.5, H69/0.4, and N231/0.2 have been developed, which are 22.9, 7.1, 3.1, 25.6, and 8.4 times more resistant to CDDP than the respective parent cell line in terms of IC50 in the soft agar colony assay with continuous drug exposure. Cloning efficiency decreased significantly in N231/0.2. The doubling times increased significantly in most of the resistant sublines. Cellular DNA contents increased in all resistant sublines, but statistical significance was observed only in H69/0.4 (p less than 0.05). Cells of the resistant sublines of PC-7, PC-9, PC-14 and H69 were larger than cells of the parent lines, but the differences were not significant. The growth morphologies of all resistant sublines in the drug-free medium were similar to those of parent cell lines. All resistant sublines tested were significantly cross-resistant to carboplatin. The patterns of cross-resistance, cross-sensitivity and collateral sensitivity to adriamycin, mitomycin-C, 5-fluorouracil, vindesine, etoposide, aclacinomycin and vincristine were different in each resistant subline. Verapamil (3.3 micrograms/ml) showed little modifying effect on CDDP resistance in 5 CDDP-resistant sublines tested except N231/0.2 (Modification Index: 0.49). Cyclosporin A (5.0 micrograms/ml) modified CDDP resistance in CDDP-resistant small-cell lung cancer sublines (H69/0.4 and N231/0.2) (Modification Index: 0.45 and 0.07, respectively), while in CDDP-resistant NSCLC sublines (PC-7/1.0 and PC-9/0.5), cyclosporin A reduced the sensitivity to CDDP.

Cell Line↗
PubMed2000

Potassium channel openers and blockers in coronary artery disease. Comparison to betablockers and calcium antagonists.

Potassium channel openers and blockers, which belong to a novel class of vasodilator drugs and to the class of specific bradycardic substances, are potential new antianginal drugs. Experimental findings in vivo suggest that bimakalim is a new substance characterized as ATP-sensitive K+ channel openers, since it exerts preferential vasodilation of the collateral circulation of the coronary vasculature and both leads to increase blood flow to ischemic areas and to attenuate the ST segment elevation caused by regional ischemia in the canine heart. Opening of KATP increases the conductivity of potassium ions which results in hyperpolarization of smooth muscle membranes, thus producing vasodilation. Tedisamil is a new bradycardic agent proven to exert antiischemic and antiarrhythmic effects by blockade of the cellular cardiac repolarization K+ currents as well as of multiple neuronal and vascular K+ currents (Ito, Ik, and K+ATP). Using right heart catheterization and exercise tolerance tests, we investigated the hemodynamic, antiischemic and neurohumoral effects of bimakalim and tedisamil in patients with angiographically proven coronary artery disease, stable angina pectoris and reproducible ST segment depression during exercise. In 50 patients with coronary artery disease, the hemodynamic and antiischemic effects of a single oral dose bimakalim of 0.1 mg, 0.3 mg and 0.6 mg were compared to placebo. In a dose-finding baseline-controlled study, a comparable collective was examined for the effects of acute i.v. administration of tedisamil 0.1, 0.2, 0.3 and 0.4 mg/kg bw. A subgroup of 8 patients receiving 0.3 mg/kg bw tedisamil i.v. was compared with a similar group of 14 patients who had received esmolol (i.v. bolus of 500 micrograms/kg, maintenance dose 200 micrograms/kg/min) and gallopamil (initial dose 0.025 mg/kg, maintenance dose 0.0005 mg/kg/h) in a second intra-individual comparison. Furthermore, in 48 patients, short-term (6 days) effects of tedisamil, 2 times 100 mg orally, were compared to 2 times 50 mg atenolol treatment. With a single oral dose of bimakalim antianginal and/or antiischemic effects were lacking, increased doses, however, induced changes in hemodynamics typical of vasodilation, i.e., a significant decrease in systolic blood pressure and a secondary chronotropic response. In contrast to bimakalim, tedisamil produced antiischemic effects and was found to have favorable hemodynamic, neurohumoral and antiischemic effects in comparison to the betablocker esmolol and atenolol in patients with coronary artery disease. Tedisamil induced a dose-dependent decrease in both heart rate and the index of myocardial oxygen consumption associated with an improvement in ST segment depression. Tedisamil as well as esmolol and atenolol showed almost equipotent antiischemic effects at the doses administered. Compared with gallopamil, both tedisamil and esmolol were superior in their effects on myocardial oxygen consumption and ST segment depression, whereas plasma lactate concentrations were more reduced by tedisamil and gallopamil.

Adrenergic beta-Antagonists↗
PubMed1990

Alterations in glutathione and glutathione-related enzymes in a multidrug-resistant small cell lung cancer cell line.

H69AR is a multidrug-resistant small cell lung cancer cell line derived from a drug-sensitive cell line, H69, by selection in doxorubicin. It is cross-resistant to a wide variety of natural product-type antineoplastic agents but does not overexpress P-glycoprotein. In the present study, the levels of GSH and GSH-related enzymes in the H69AR cell line were determined and compared with those found in H69 cells. Unlike other drug-resistant cell lines, GSH levels were diminished 6-fold in H69AR cells (0.67 +/- 0.28 microgram/mg of protein), compared with H69 cells (4.23 +/- 1.17 micrograms/mg of protein) (p less than 0.01). This unusually low level of GSH may explain the pronounced collateral sensitivity of H69AR cells to buthionine sulfoximine (BSO), an inhibitor of the rate-limiting enzyme in GSH biosynthesis (ID50 of 4.4 microM BSO for H69AR cells versus ID50 of 300 microM BSO for H69 cells). BSO did not enhance doxorubicin cytotoxicity in the H69AR cell line, despite further depletion of GSH. GSH-reductase (EC 1.6.4.2) activity was elevated 2-fold in H69AR cells, compared with sensitive H69 cells (75.34 +/- 14.94 versus 38.62 +/- 5.06 nmol of NADPH/min/mg of protein) (p less than 0.05). Both selenium-dependent and -independent GSH-peroxidase (EC 1.11.1.9) activities were unchanged in the resistant H69AR cell line, compared with its parent cell line. gamma-Glutamyl transpeptidase (EC 2.3.2.2) activity was 5-fold elevated in H69AR cells, compared with H69 cells (2.50 +/- 0.44 versus 0.46 +/- 0.21 nmol of p-nitroaniline/min/mg of protein) (p less than 0.01), whereas GSH-S-transferase (EC 2.5.1.18) activity was 10-fold higher (201.98 +/- 43.62 versus 19.77 +/- 1.72 nmol of 1-chloro-2,4-dinitrobenzene/min/mg of protein in H69AR and H69 cells, respectively) (p less than 0.01). The GSH-S-transferases from both cell lines were purified by affinity chromatography and immunoblot analysis identified the GSH-S-transferases as belonging to the anionic pi class. GSH-S-transferases from the mu or alpha classes were not detectable in either cell line. In conclusion, marked differences in GSH levels and the activities of three of four GSH-related enzymes were observed between the multidrug-resistant H69AR cell line and its parent cell line. Further study is required to determine whether these changes are causally related to the development of drug resistance in this model system.

Antineoplastic Agents↗
PubMed1984

Cytochemical characterization of Yoshida sarcoma cells resistant to dibromodulcitol.

Two Yoshida ascites sarcoma cell populations, one of them originally sensitive and another rendered resistant to the alkylating agent dibromodulcitol (DBD), were compared for doubling time, labeling index, survival time, morphological features, cellular DNA content and modal DNA value. Cross-resistance studies were carried out on bilaterally growing solid tumours derived from the sensitive and resistant Yoshida cell populations. Glycogen-containing granules appeared in the cytoplasm of the DBD-resistant sarcoma cells; these were not present in the sensitive tumour. The growth parameters of the sensitive tumour were throughout the 10-day observation period characteristic of rapidly proliferating tumours, whereas those of the DBD-resistant tumour was characteristic of slowly proliferating systems. As compared to the mean DNA values for normal somatic cells (lymphocytes), those found for both tumours indicated that the cells were hyperdiploid aneuploid. The DNA stem line in the resistant tumour proved to be significantly smaller than that in the sensitive tumour. These results indicate that a reduction of malignancy in the Yoshida tumour is associated with a developed resistance to dibromodulcitol. The resistant tumour showing cross-resistance to dianhydrogalactitol, diacetyl-dianhydrogalactitol and to nitrogen mustard retained full sensitivity to cyclophosphamide and adriablastin (Adriamycin), and proved to be collaterally sensitive to vincristin.

Animals↗
PubMed1995

Decreased sensitivity of multidrug-resistant tumor cells to cisplatin is correlated with sorcin gene co-amplification.

A set of multidrug resistant (MDR) murine leukemia P388 sublines processing 30-50-fold mdr1 gene amplification was obtained as a result of experimental chemotherapy with rubomycin, ruboxyl, vinblastine, vincristine, or combination of rubomycin and vincristine. Significant differences of developed MDR sublines in response to treatment with cisplatin, tiophosphamide, sarcolysin, and dopad were found. Strong correlation between drug sensitivity and a copy number of gene coding for 19-22 kDa calcium-binding sorcin gene co-amplification were hypersensitive to cisplatin and alkylating agents, the cell sublines showing amplification of sorcin DNA sequences did not possess such collateral sensitivity and even acquired cross-resistance. The dependence of sensitivity to cisplatin on sorcin gene co-amplification was confirmed by analysis of Djungarian hamster DM15 cell sublines that selected for MDR in vitro by colchicine.

Alkylating Agents↗
PubMed2001

Reversal of cytosine arabinoside (ara-C) resistance by the synergistic combination of 6-thioguanine plus ara-C plus PEG-asparaginase (TGAP) in human leukemia lines lacking or expressing p53 protein.

BACKGROUND: Sequence-specific combinations of purine analogs, such as fludarabine or 6-mercaptopurine (6-MP), administered prior to cytosine arabinoside (ara-C) have been shown to abrogate ara-C resistance in human leukemia cells in vitro and in patients with relapsed acute myeloid or lymphoblastic leukemias. The two-drug combination of 6-MP plus ara-C results in greater cytotoxicity than that achieved with either ara-C or 6-MP alone. Further preclinical investigations have shown that the addition of PEG-asparaginase (PEG-ASNase) to the combination of 6-MP plus ara-C (6-MP + ara-C + PEG-ASNase) results in 15.6-fold synergism over that achieved with the two-drug regimen. This is due to increased DNA damage leading to apoptotic cell death. PURPOSE: Since the intravenous preparation of 6-MP is no longer available and since oral 6-thioguanine (6-TG) provides higher levels of intracellular thioguanine nucleotides than an isotoxic dose of oral 6-MP, we investigated the potential drug synergism of 6-TG plus ara-C plus PEG-ASNase (TGAP) in myeloid (HL60/S, HL60/SN3, U937) and lymphoblastic (CEM/0, CEM/ ara-C/B, CEM/ara-C/I, MOLT-4) leukemia cell lines. The CEM clones, MOLT-4 and HL60/SN3 cell lines expressed functional or measurable p53 protein, while the other cell lines did not. METHODS: The MTT and trypan blue dye exclusion assays were used to determine drug cytotoxicity. In addition, cellular apoptosis and cellular p53, p21/waf-1 and bcl-2 protein concentrations were determined by FACS analysis and ELISA assays. RESULTS: Sequential exposure to 6-TG (24 h) plus ara-C (24 h) plus PEG-ASNase (24 h) produced 1.3- to 18.3-fold drug synergism over the two-drug combination of 6-TG plus ara-C. The molecular mechanism of synergism was due to the fact that the three-drug combination was capable of downregulating bcl-2 oncoprotein levels in these cell lines even when p53 was absent. CONCLUSION: These studies strongly demonstrate that the TGAP regimen is highly synergistic in p53-null and p53-expressing leukemia cell lines. We conclude that this combination regimen is collaterally sensitive with ara-C and further evaluation in an investigational phase I trial in relapsed leukemia patients is warranted.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1985

Evolution of methotrexate resistance of human acute lymphoblastic leukemia cells in vitro.

A human acute lymphoblastic T-cell line, MOLT-3, was fed with Roswell Park Memorial Institute Medium 1640 supplemented with 10% fetal bovine serum and antibiotics which contained increasing concentrations of methotrexate (MTX). The development of drug resistance was associated initially with progressive decrease in MTX transport. When the cells became 200-fold resistant, a rise in the dihydrofolate reductase was noted which was short-lived in the absence of the drug. A 10,000-fold increase in MTX resistance was accompanied, in addition to further decrease in MTX transport, by a 10-fold increase in the dihydrofolate reductase activity. While the purely transport-related resistant cell lines had a collateral sensitivity to lipid-soluble antifols, the sublines which had both transport- and enzyme-related MTX resistance contained a subpopulation highly resistant to these antifols. Chromosome analysis of the subline with increased dihydrofolate reductase activity showed an expanded abnormally banded region in chromosome 5.

Cell Line↗
PubMed1996

Drug-induced down-regulation of topoisomerase I in human epidermoid cancer cells resistant to saintopin and camptothecins.

The anticancer agent saintopin induces DNA cleavage mediated by both topoisomerase (topo) I and topo II in vitro through stabilization of the reversible enzyme-DNA cleavable complex. We established saintopin-resistant cell lines (KB/STP-1 and KB/STP-2) from human epidermoid cancer KB cells by stepwise exposure to increasing doses of the drug. KB/STP-1 and KB/STP-2 cells showed 12- and 44-fold increases, respectively, in resistance to saintopin relative to that of KB cells. Both saintopin-resistant cell lines showed only small reductions in sensitivity to the topo II inhibitor etoposide but developed marked cross-resistance to the topo I-targeting camptothecin derivative CPT-11 [(4s)-4,11-diethyl-4-hydroxy-9-[(4-piperidinopiperidino)carbony loxy] dione hydrochloride trihydrate] and its active form, SN-38 (7-ethyl-10-hydroxycamptothecin). In contrast, both KB/STP-1 and KB/STP-2 cells showed increased collateral sensitivity to cisplatin, a nitrosourea derivative, mitomycin C, and UV light. The protein concentration, activity, and mRNA abundance of both topo I and topo II were similar in KB/STP-1, KB/STP-2, and the parental KB cells. There were no significant changes in the drug-stabilized topo-DNA cleavable complex formation in KB and KB/STP-2 cells. Two point mutations were detected in topo I cDNA from KB/STP-2 cells, but these were also present in KB cells. Topo I mRNA abundance decreased markedly immediately after exposure of KB/STP-2 cells to saintopin; no such effects were apparent in KB cells. In contrast, topo II mRNA was not markedly affected by saintopin in either KB or KB/STP-2 cells. Treatment with CPT-11 or SN-38 also induced a markedly greater and more persistent reduction in topo I mRNA abundance in KB/STP-2 cells than in KB cells. Etoposide had no marked effect on topo I mRNA abundance in either KB/STP-2 or KB cells. Topo I mRNA was highly unstable in KB/STP-2 cells in comparison to KB cells when incubated with saintopin. This novel regulation of topo I mRNA by topo I-targeting agents could be associated with acquirement of drug resistance to saintopin or SN-38/CPT-11 in KB/STP-2 cells.

Antibiotics, Antineoplastic↗
PubMed1994

Effects of lovastatin on a human myeloma cell line: increased sensitivity of a multidrug-resistant subline that expresses the 170 kDa P-glycoprotein.

Using a fluorometric microculture cytotoxicity assay for measuring cell viability and proliferation we examine the cytotoxic effect of lovastatin on a drug sensitive myeloma cell line (RPMI 8226) and a multidrug resistant (MDR) clone (8226/Dox40), that was approximately 100-fold less sensitive to doxorubicin. The RPMI 8226 cells were sensitive to lovastatin with an IC50 of 15.8 micrograms/ml. However, the MDR subline exhibited a collateral sensitivity to lovastatin, with an IC50 of 1.7 microM, thus having a 9.3-fold greater sensitivity to lovastatin than the parental cell line. The combination of doxorubicin and lovastatin did not show any synergistic or antagonistic effects on any of the cell lines. The increased sensitivity to lovastatin of the P-gp 170-expressing MDR cells 8226/Dox40 might be part of a more general phenomenon that merits further investigation.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1994

Therapeutic potential of potassium channel activators in coronary heart disease.

Potassium channel activators have the ability to open potassium channels in a variety of cells. Since most of their effects are antagonized by antidiabetic sulfonylureas, the ATP-sensitive potassium channel is their likely target. Opening of potassium channels leads to hyperpolarization of the surface membrane with consequent closure of voltage-dependent ion channels and reduction of free intracellular calcium ions. Currently available potassium channel activators, including aprikalim, bimakalim, cromakalim, emakalim, nicorandil, pinacidil etc., display a high affinity for potassium channels of vascular smooth muscle. Vasodilation and a reduction in systemic vascular resistance are their prominent pharmacological effects. Coronary and cerebral arteries are highly sensitive to potassium channel activator-induced dilation. Apart from treatment of hypertension, potassium channel activators appear to have therapeutic potential in coronary heart disease. They reduce cardiac afterload, increase native and collateral coronary blood flow and reduce the size of experimental myocardial infarcts. This last effort cannot be satisfactorily explained entirely by haemodynamic or coronary vascular actions of potassium channel activators and a cardioprotective effect is postulated. For these drugs ischaemia-induced and activator-induced opening of cardiac ATP-sensitive potassium channels appear to work in concert. Nicorandil combines the pharmacological properties of an organic nitrate with those of potassium channel activators. Experimental and clinical results characterize nicorandil as a unique and promising drug for the treatment of coronary heart disease.

Animals↗
PubMed1982

Colchicine resistance in human cell lines. Pleiotropic phenotype and decreased membrane permeability.

Colchicine-resistant human cells were initially observed in patients exhibiting C-anaphases or tetraploidy in lymphocyte cultures. Cell lines established from these patients displayed cross-resistances to daunomycin, emetine, vinblastine, and vincristine and collateral sensitivity to Xylocaine, showing a pleiotropic phenotype similar to that described in permeability mutants in CHO cells. 3H colchicine uptake and binding assays confirmed a decreased permeability to the drug.

Cell Line↗
PubMed1989

Drug resistance and cross-sensitivity in cultured human osteosarcoma cells.

The sensitivity, cross-sensitivity, acquired resistance and restoration of sensitivity to adriamycin (ADR) in cultured human osteosarcoma (OST) cells were studied from the viewpoints of cell proliferation and cell cycle pattern by flow cytometry. OST cells resistant to ADR were produced by a treatment which consists of a 40-hour exposure to high doses of ADR and subsequent cultivation for 6 weeks and was repeated five times. ADR-resistant cells showed cross-resistance to methotrexate (MTX), and vincristine (VCR), and collateral sensitivity to cisplatin (CDDP). Treatment of the ADR-resistant cells with ADR and verapamil, a Ca-antagonist, resulted in an increased inhibition of sarcoma cell growth.

Cisplatin↗
PubMed1994

Cross-resistance to antitumor diarylsulfonylureas and collateral sensitivity to mitochondrial toxins in a human cell line selected for resistance to the antitumor agent N-(5-indanylsulfonyl)-N'-(4-chlorophenyl)urea.

Diarylsulfonylurea (DSU) antitumor agents represent a new class of oncolytic compounds with an unknown, potentially novel, mechanism of action. At high concentrations of several of these agents, cytotoxicity appears to be a consequence of uncoupling of mitochondria. However, the mechanism of action at pharmacologically achievable concentrations is unknown. To further study these agents a subline of human colon carcinoma, GC3/c1, was selected for resistance to N-(5-indanylsulfonyl)-N'-(4-chlorophenyl)urea (ISCU) (Sulofenur). This clone (designated LYC5) was stably resistant for 2 years in the absence of selection pressure and was characterized for cross-resistance to other antitumor DSU and therapeutically used oncolytic agents. LYC5 was cross-resistant to six of seven DSU analogues examined when cells were exposed to drugs for 7 days. However, the degree of resistance was inversely related to the potency of the individual DSU against the parental GC3/c1 clone. Consequently, against LYC5 cells there was a relatively narrow range for concentrations inhibiting colony formation by 50% (4-fold), compared with that in GC3/c1 cells (12-fold range). With a single exception, each DSU examined caused uncoupling of oxidative phosphorylation in isolated mitochondria at 50 microM, and data suggest that cytotoxicity in LYC5 cells may be a consequence of mitochondrial impairment. In contrast, LYC5 cells were collaterally sensitive to the mitochondrial toxins rotenone, antimycin, and oligomycin, by 11.4-, 7.2-, and 36.9-fold respectively. LYC5 cells were also collaterally sensitive to vincristine (7.7-fold), Actinomycin D (5.9-fold), and rhodamine-123 (10.5-fold), agents associated with P-glycoprotein (Pgp)-mediated multidrug resistance (MDR). LYC5 cells were slightly more sensitive to Melphalan and doxorubicin (2.8- and 2.3-fold, respectively) but not to cisplatin or dideazatetrahydrofolic acid. Collateral sensitivity to vincristine and Actinomycin D was consistent with decreased Pgp levels in LYC5 cells. Immunohistochemical staining and Western blotting with anti-Pgp antibodies indicated an 8-fold reduction in Pgp levels in LYC5 cells, relative to expression in parental GC3/c1 cells. Consequently, association of mitochondrial toxins with resistance in MDR KB8-5 cells was examined in the presence or absence of the MDR-reversing agent verapamil. KB8-5 cells had equal or greater sensitivity, compared with parental KB3-1 cells, to rotenone, antimycin, and oligomycin and also to each DSU analogue examined. In addition, verapamil tended to have a protective effect against these mitochondrial toxins.(ABSTRACT TRUNCATED AT 400 WORDS)

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1992

Doxorubicin sensitivity pattern in a panel of small-cell lung-cancer cell lines: correlation to etoposide and vincristine sensitivity and inverse correlation to carmustine sensitivity.

The aim of our investigations is to evaluate whether the sensitivity patterns of small-cell lung-cancer (SCLC) cell lines in vitro can be used in evaluating new drugs and in selecting drugs for the optimization of combination therapy. In our attempts to obtain a panel of cell lines demonstrating differential patterns in sensitivity, we have developed three SCLC lines exhibiting different types of multidrug resistance (MDR). In the present investigations we compared the sensitivity patterns shown by five wild-type SCLC lines and three MDR lines in response to six different types of drugs: doxorubicin, cytarabine, carmustine, cisplatin, vincristine, and etoposide. In the wild-type SCLC cell lines, the range of variation in sensitivity to all drugs was within a factor of 10. Cell lines showing low sensitivity to doxorubicin also exhibited low sensitivity to etoposide and vincristine, and vice versa. In contrast, the pattern of sensitivity to carmustine was almost the opposite of that to doxorubicin. A tendency to an inverse relationship between doxorubicin and carmustine sensitivity was also observed when doxorubicin sensitivity was reduced in near stationary cells and in cells exposed to the metabolic inhibitor 2-deoxy-D-glucose. In agreement with the pattern observed for the wild-type lines, all of the MDR sublines demonstrated collateral sensitivity to carmustine. As to cytarabine, the wild-type lines expressed a sensitivity pattern similar to that shown in response to doxorubicin. Interestingly, the opposite pattern was found in the MDR lines, as all three demonstrated cytarabine hypersensitivity. The combination of alkylating agents and "MDR" drugs are of proven clinical benefit in the treatment of solid tumors, as is the combination of anthracycline and cytarabine in acute myeloid leukemia. The experimentally derived sensitivity data on cytarabine, alkylating agents, and MDR drugs (i.e., etoposide, doxorubicin, vincristine) thus resemble the clinical experience with these drugs, and we conclude that the use of a clonogenic assay on the described panel of SCLC cell lines can give valuable information for the selection of agents for combination therapy.

ATP Binding Cassette Transporter, Subfamily B, Mem↗