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Results for “Drug Collateral Sensitivity”

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PubMed1992

Collateral sensitivity to nitrosoureas in multidrug-resistant cells selected with verapamil.

We have examined the effects of the nitrosoureas, streptozotocin (STZ) and 1,3-bis(chloroethyl)-1-nitrosourea (BCNU), on a human multiple myeloma cell line, RPMI 8226, and its drug-resistant variants. Cell lines selected for doxorubicin (DOX) resistance alone displayed a STZ and BCNU cytotoxicity profile similar to that of the parent cell line. In contrast, two of the drug-resistant variants selected with DOX plus verapamil, an agent which inhibits P-glycoprotein-mediated multidrug resistance, displayed a collateral sensitivity to STZ and BCNU. Verapamil was included in the selection protocol because it has been shown to inhibit the P-glycoprotein-mediated multidrug resistance phenotype and is now in clinical trials as a chemosensitizing agent. The collateral sensitivity to these nitrosoureas seen in the DOX plus verapamil-selected cell lines is due to the functional loss of a DNA repair molecule, O6-Methylguanine DNA methyltransferase (MGMT). The functional loss of MGMT is secondary to the loss of MGMT gene expression. The loss of MGMT gene expression is not due to loss or gross rearrangement of the MGMT-coding region. If this selection pressure applied in vitro reflects the in vivo situation, then new chemotherapeutic strategies may be devised to exploit this phenomenon. These cell lines will serve as useful models for delineating mechanisms which govern MGMT expression.

Base Sequence↗

PubMed1985

Cross-resistance of vinblastine- and taxol-resistant mutants of Chinese hamster ovary cells to other anticancer drugs.

Stable mutants resistant to the anticancer drug vinblastine (VinR mutants) have been isolated after a single selection step from Chinese hamster ovary cells. Of the two types of VinR mutants which are obtained, one class exhibits specific cross-resistance to only some of the microtubule inhibitors. However, the second type of mutants, which is affected in membrane permeability, exhibits cross-resistance to a wide variety of unrelated compounds. Both classes of VinR mutants showed codominant expression in cell hybrids formed between resistant and sensitive cells. The cross-resistance patterns of the VinR mutants and a single-step mutant resistant to the anticancer drug taxol (TaxR mutant) toward various anticancer drugs have been determined. The mutants resistant to both of these drugs showed significantly increased resistance toward aclarubicin, dactinomycin, doxorubicin, bisantrene, bruceantin, chromomycin A3, demecolcine, colchicine, daunorubicin, ellipticine, emetine, ethidium bromide, maytansine, mithramycin, mitoxantrone, nitidine chloride, olivomycin, podophyllotoxin, puromycin, taxol, vinblastine, vincristine, vindesine, teniposide, and etoposide. Interestingly, either one or both of the above mutants exhibited somewhat enhanced sensitivity toward vidarabine, acivicin, bleomycin, cisplatin, cytarabine, alpha-difluoromethyl-ornithine, 5-FU, tegafur, and tiazofurin. For a number of other anticancer drugs which were examined (chlorambucil, mitolactol, IMPY, hexamethylmelamine, hydroxyurea, diglycoaldehyde, methotrexate, mitoguazone, mitomycin, nocodazole, and 6-thioguanine), the level of resistance of these mutants was found to be unaltered. The information regarding cross-resistance and collateral sensitivity patterns of VinR and TaxR mutants should prove to be very useful in the design of drug combinations which could prove more effective in cancer chemotherapy.

Alkaloids↗

PubMed1991

Cross-resistance patterns in ACNU-resistant glioma sublines in culture.

Three ACNU-resistant clones (R1, R3, and R12) were isolated from 9L rat glioma cells under selection pressure of ACNU in vitro. The authors have investigated the mechanisms of resistance and characteristics of these clones at the cellular level by studying cross-resistance patterns to chemical and physical agents. Although these resistant sublines showed complete cross-resistance to methyl-chloroethylnitrosourea (MCNU), no cross-resistance was observed for other alkylating agents, while each of the resistant sublines showed partial cross-resistance to structurally dissimilar toxic agents (vinblastine, Adriamycin, and VP-16). No difference in ACNU uptake was observed between 9L and R3 cells, and resistance patterns among alkylating agents suggested that the mechanism of ACNU resistance was specific to bifunctional nitrosoureas. Based on a transport study, this multidrug resistance could be explained by reduced intracellular uptake of these drugs, but there seemed little possibility that membrane P-glycoprotein, which usually is observed in typical multidrug-resistant cells, was expressed in these ACNU-resistant cells because enhanced drug efflux was not found in ACNU-resistant sublines. Significant collateral sensitivity to L-asparaginase indicated that ACNU might disturb the asparagine synthetic pathways by its mutagenic action. The increased level of total glutathione in the resistant sublines may be one mechanism of radiation or ACNU resistance.

Animals↗

PubMed1986

Selection of nitrogen mustard resistance in a rat tumor cell line results in loss of guanine-O6-alkyl transferase activity.

Cell killing, DNA-interstrand crosslinks, and DNA-protein crosslinks were assayed in nitrogen mustard-resistant Walker 256 carcinoma (WR) cells and the parent cell line (WS) after treatment with 5-[3-(2-chloroethyl)-1-triazenyl]imidazo-4-carboxamide (MCTIC). The WR cells, which also express collateral sensitivity to chloroethylnitrosoureas, were approximately twice as sensitive to the cytotoxic effects of MCTIC as were WS cells. Following treatment with 100 microM MCTIC, there was a rapid accumulation of both DNA-interstrand and DNA-protein crosslinks in the WR cell line, which reached a maximum at 6 and 12 hr, respectively. There was considerably less crosslinking in the WS cells and both cell lines were proficient in repairing most of the crosslinks by 24 hr. Measurement of guanine-O6-alkyl transferase activity showed the enzyme to be present in WS but not in WR cells. These data indicate that the collateral sensitivity of nitrogen mustard-resistant WR cells to chloroethylating drugs is in part due to the loss of guanine-O6-alkyl transferase activity which is present in the parent line.

Animals↗

PubMed1998

Ovarian cancer cisplatin-resistant cell lines: multiple changes including collateral sensitivity to Taxol.

BACKGROUND: Alteration in apoptosis pathways (in particular mutations of p53 gene) may result in resistance of ovarian carcinoma to cisplatin. However, cisplatin resistance is likely to be multifactorial. An understanding of the molecular alterations associated with the development of resistance may be of considerable relevance in an attempt to optimize the therapeutic approach. STUDY DESIGN: Two cisplatin-resistant sublines (IGROV-1/Pt0.5 and IGROV-1/Pt1), both characterized by mutant p53 (Cancer Res 1996; 56: 556-62), but with different degree of resistance were studied in terms of pattern of cross-resistance, susceptibility to drug-induced apoptosis, expression of gluthathione-dependent system, cellular pharmacokinetics, drug-induced DNA damage. The resistance index (ratio between the IC50 of resistant and sensitive cells) after a 96-hour drug exposure was 10 for IGROV-1/Pt0.5 and 14 for IGROV-1/Pt1 cells. RESULTS: Resistant cells were cross-resistant to DNA-damaging agents and, interestingly, they had a collateral sensitivity to Taxol. The cellular response to Taxol paralleled the drug ability to induce apoptosis. The intracellular glutathione level was significantly increased in IGROV-1/Pt cells compared to the sensitive counterpart. In contrast, glutathione S-transferase level was consistently reduced in both sublines. gamma-Glutamyl transpeptidase activity, which was lower in resistant than in sensitive cells, was not directly correlated with glutathione level, thus suggesting a complex regulation of cellular glutathione content. In the resistant cells with the highest glutathione content, a reduced level of cisplatin-induced cross-link was found. Analysis of DNA platination revealed a slight decrease of DNA-bound platinum only in IGROV-1/Pt1 cells. Again, this reduction is consistent with a protective role for glutathione. The expression of metallothionein IIa was increased in both resistant variants. CONCLUSIONS: Multiple changes are involved in acquired resistance of ovarian carcinoma cells including reduced susceptibility to apoptosis as consequence of inactivation of p53 and expression of defence mechanisms. The relative contribution is related to the degree of drug resistance. In particular, the glutathione-dependent system could have a role only in the development of a high degree of resistance. Finally, the finding that Taxol was very effective in inducing apoptosis in resistant sublines with p53 mutation supports the expression of an intact p53-independent pathway of apoptosis and suggests the pharmacological interest of Taxol in the treatment of p53-mutated tumors.

Adenocarcinoma↗

PubMed1990

Drug sensitivity of heat-resistant mouse B16 melanoma variants.

Induction of transient thermotolerance by heat or other cytotoxic stressors has been reported to confer a moderate degree of drug resistance to tumor cells in vitro. In this study, a genetically stable, heat-resistant mouse B16 melanoma variant (W-H75) was tested for its sensitivity to various cytotoxic and antiproliferative agents. The heat-resistant W-H75 cells displayed a moderate two- to threefold resistance to doxorubicin, VP-16, VM-26, colchicine, cis-dichlorodiammineplatinum(II), HgCl2, and CdCl2. Marginal resistance to 4'(9-acridinylamino)methanesulfon-m-anisidide vinblastine, 1,3-bis(2-chloroethyl)-1-nitro-sourea, and NaAsO2 was observed, while no difference in sensitivity to the anticancer drugs, actinomycin D and camptothecin, was observed. Although W-H75 cells were generally more resistant than the parental cells to most of the agents that were tested, they were collaterally sensitive to the antimetabolites methotrexate and 6-mercaptopurine. Resistance of the W-H75 cells to epipodophyllotoxins and anthracyclines was not due to differences in steady-state drug accumulation. For the epipodophyllotoxin VP-16, resistance may be related to a relative decrease in the number of drug-induced DNA strand breaks in W-H75 cells. However, no difference in DNA strand breakage was observed between W-H75 and parental cells which were treated with doxorubicin, suggesting that resistance to this drug occurred by a different mechanism. The possible involvement of glutathione and glutathione S-transferase in resistance was also investigated. The glutathione content in W-H75 cells was 35% higher than that in the parental line. However, glutathione S-transferase activity appeared to be identical in both cell lines. Two other heat-resistant B16 melanoma variants, B-H103 and R-H92, were also tested for sensitivity to doxorubicin and VP-16. In contrast to the W-H75 cells, these two heat-resistant variants were hypersensitive to doxorubicin. The B-H103 cells were also hypersensitive to VP-16. This study suggests that selection for cellular resistance to heat may result in cells that have an altered sensitivity to drugs.

Acclimatization↗

PubMed2003

A mechanism for P-glycoprotein-mediated apoptosis as revealed by verapamil hypersensitivity.

Selection of tumor cell lines with anticancer drugs has led to the appearance of multidrug-resistant (MDR) subclones with P-glycoprotein 1 (P-gp1) expression. These cells are cross-resistant to several structurally and functionally dissimilar drugs. Interestingly, in the process of gaining resistance, MDR cells become hypersensitive or collaterally sensitive to membrane-active agents, such as calcium channel blockers, steroids, and local anaesthetics. In this report, hypersensitivity to the calcium channel blocker, verapamil, was analyzed in sensitive and resistant CHO cell lines. Our results show that treatment with verapamil preferentially induced apoptosis in MDR cells compared to drug-sensitive cells. This effect was independent of p53 activity and could be inhibited by overexpression of the Bcl-2 gene. The induction of apoptosis by verapamil had a biphasic trend in which maximum cell death occurred at 10 microM, followed by improved cell survival at higher concentrations (50 microM). We correlated this effect to a similar biphasic trend in P-gp1 ATPase activation by verapamil in which low concentrations of verapamil (10 microM) activated ATPase, followed by inhibition at higher concentrations. To confirm the relationship between apoptosis and ATPase activity, we used two inhibitors of P-gp1 ATPase, PSC 833 and ivermectin. These ATPase inhibitors reduced hypersensitivity to verapamil in MDR cells. In addition, low concentrations of verapamil resulted in the production of reactive oxygen species (ROS) in MDR cells. Taken together, these results show that apoptosis was preferentially induced by P-gp1 expressing cells exposed to verapamil, an effect that was mediated by ROS, produced in response the high ATP demand by P-gp1.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1989

Comparative effectiveness of mitoxantrone and doxorubicin in overcoming experimentally induced drug resistance in murine and human tumour cell lines in vitro.

Using a range of cell lines of murine and human tumour origin in which relatively modest levels (2- to 17-fold) of drug resistance have been selected in vitro by exposure to a range of standard antitumour drugs, we compared the cytotoxic effects of doxorubicin (DOX) and mitoxantrone (MITO). In general, significantly lower concentrations of MITO than of DOX were required to achieve comparable cytotoxicity, confirming previously published data. MITO appears more generally effective against the murine L5178Y drug-resistant sublines than DOX, although there was no expression of collateral sensitivity to this newer agent. In the various human tumour lines there was a lack of cross-resistance to both DOX and MITO in two 5-fluorouracil (FU)-resistant lines and one of two cisplatin (CDDP)-resistant cells, but cross-resistance was expressed in one subline resistant to vincristine (VCR) and two etoposide (VP-16)-resistant sublines. One murine and two human DOX-resistant sublines were effectively killed by MITO, whilst DOX proved effective against the human MITO-resistant subline. This apparent lack of cross-resistance between DOX and MITO in these resistant sublines expressing low levels of resistance in vitro therefore appears to contrast with previous reports involving highly multidrug-resistant DOX-selected sublines. However, since the latter lines generally exhibited profound cross-resistance to VCR and definite cross-resistance to VP-16, this may at least in part dictate their responses to MITO. Therefore, attempts to use experimentally derived drug-resistant sublines for preclinical drug screening should be approached with caution, since patterns of drug response appear to be influenced by the level of drug resistance expressed. The need remains to determine which type of model system provides the most relevant clinical information.

Animals↗

PubMed1984

Transport of the antitumor antibiotic Cl-920 into L1210 leukemia cells by the reduced folate carrier system.

Cl-920 is a structurally novel antitumor antibiotic which has activity against a wide spectrum of tumor cells in vitro and is curative in L1210 leukemia in vivo. Several lines of evidence indicate that this drug penetrates L1210 cells via the reduced folate carrier system. Reduced folates (100 microM) including leucovorin and 5-methyltetrahydrofolate completely protected L1210 cells from growth inhibition by Cl-920. Protective effects were not observed, however, with folic acid, a compound which is transported by a process distinct from that for reduced folates. Cl-920 was a potent inhibitor of methotrexate influx exhibiting a mixture of competitive and noncompetitive inhibition and having a Ki (slope) of 30.0 microM and a Ki (intercept) of 58.8 microM. The inhibition appeared to be irreversible since, after cells were preincubated with drug, the inhibitory effects persisted after cells were washed in drug-free media. The irreversibility could be eliminated, however, by dithiothreitol, suggesting that Cl-920 may interact with a thiol which is essential to this transport system. Cells made 71-fold resistant to Cl-920 by continuous exposure to increasing concentrations of this drug were 245-fold cross-resistant to methotrexate but were collaterally sensitive to the lipophilic antifolate trimetrexate and contained normal levels of dihydrofolate reductase. This mutant cell line had a severely impaired reduced folate carrier system exhibiting methotrexate influx rates of less than 1% of control cells. Finally, inhibition of methotrexate influx by a number of Cl-920 analogues showed that the intact lactone ring and the presence of the phosphate ester were required for maximum interaction with the carrier system and that the degree of inhibition correlated with relative antitumor potency. These observations are compatible with the concept that Cl-920 utilizes the folate carrier system and could be of fundamental importance for understanding the cytotoxicity and selectivity of Cl-920.

Alkenes↗

PubMedDate not supplied

Characterization of four drug-resistant P388 sublines: resistance/sensitivity in vivo, resistance-and proliferation-markers, immunogenicity.

It was the aim of this study to compare drug-resistant sublines of the murine P388 in relation to resistance markers, the resistant phenotype and immunogenicity. Resistance to drugs either belonging to the MDR type (Doxorubicin, Vincristine, Mitoxantrone) or to the non-MDR type (Methotrexate) was generated in vivo in order to mimic the clinical situation. All resistant sublines expressed the mdr1 gene and the p-glycoprotein determined on m-RNA level or immunohistochemically, while no expression was registered in the parent P388. The rhodamine 123 fluorescence as marker for the energy dependent drug efflux pump was decreased only in the MDR-sublines, while the parent P388 and the Methotrexate-resistant line retained 100% or 90% of the dye, respectively. This indicates that the rhodamine efflux is a more function-related marker for MDR than the mdr1 gene and the pgp. The in vivo characterization of the sublines as regards their sensitivity to cytostatics revealed a clear-cut cross-resistance to MDR drugs in the MDR-lines, while the Methotrexate resistant subline was only cross-resistant to Cytarabine. In each resistant subline collateral sensitivity to certain but different cytostatics was observed. Experiments to overcome resistance by concomitant treatment with the modulators Nifedipine, Verapamil, Cyclosporin A and Chloroquin led to only limited success. The sublines P388/Mitox, P388/Vinc and P388/MTX developed immunogenicity which was never registered in the original P388. Vaccination with lethally irradiated drug-resistant cells resulted in a substantial rejection of viable tumor cells of the same line. With the P388/Mitox and P388/Vinc also an over-cross immunization was possible. This generation of immunogenicity as a concomitant characteristic of resistance should be considered as therapeutic potential also in the treatment of clinical cancer.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1988

Interactions between antitumor drugs and radiation in mammalian tumor cell lines: differential drug responses and mechanisms of resistance following fractionated X-irradiation or continuous drug exposure in vitro.

Drug-resistant mammalian tumor cell lines have been derived by either fractionated x-irradiation treatment or exposure to vincristine or etoposide (VP-16-213) in vitro. Analyses of the patterns of responses expressed by these differently derived, resistant cell lines have shown variations in responses to a range of antitumor drugs depending upon the agent used to induce resistance. However, all treated cell lines express resistance to vincristine and, with one exception, to VP-16-213. Preliminary evidence has indicated that resistance to vincristine in drug-treated cells, but not x-irradiation-treated cells, is associated with impaired vincristine uptake; resistance to VP-16-213 in both differently derived, resistant sublines is associated with a reduction of VP-16-213-induced DNA single-strand breakage; and collateral sensitivity to cisplatin in x-irradiation-treated cells is associated with enhanced drug-induced DNA cross-linking. These data indicate that patterns of responses to antitumor drugs and the mechanisms associated with these altered responses differ depending upon the agent used to induce resistance.

Animals↗

PubMedDate not supplied

Collateral sensitivity to thaliblastine and/or hyperthermia exhibited by a rat ovarian tumor cell line selected for resistance to cisplatin.

Drug resistance severely limits the effectiveness of clinical cancer chemotherapy. Employment of drugs other than the selected compounds with different mechanisms of action may provide a potential way to improve the therapeutic effects. Thaliblastine (TBL), a natural compound, showed a 2-fold higher cytotoxicity in a cisplatin (DDP) resistant rat ovarian tumor cell line (0-342/DDP) than in its parental sensitive line (0-342), as determined by an antiproliferation assay with 24 h continuous exposure. This phenomenon was also observed following 2 h pulse exposure if combined with heat treatment (40 degrees C). Further escalation of the temperature to 43 degrees C alone brought about 74.7 +/- 17.0% growth inhibition in the sensitive and 97.2 +/- 1.8% in the resistant line. Under this condition, the ID50 of TBL was again only half as much in 0-342/DDP cells as in the parental cells (12 vs 24 micrograms/ml) when compared to the hyperthermic treatment alone. In a colony formation assay with 2 h pulse exposure, the hypersensitivity of the resistant cells to DDP and/or heat was further confirmed. Alkaline elution showed that 24 h continuous treatment with TBL induced DNA single-strand breaks (SSB) in a dose-dependent manner in 0-342/DDP cells, whereas there was almost no DNA-SSB production by TBL in the sensitive line, possibly in part accounting for the hypersensitivity of the DDP resistant cells to TBL. The heat treatment (40 degrees C for 2 h) induced SSB in both lines, which was further enhanced by combination with TBL. This damage was repaired in part in 0-342 but almost completely in 0-342/DDP line after cells grew in drug-free medium for 48 h following the exposure, indicating that resistant cells can more efficiently repair DNA damage by either TBL or hyperthermia. Altogether, these results suggest that TBL may have potential to be used clinically as an alternative in the treatment of cisplatin-resistant malignancies with hyperthermia.

Animals↗

PubMed1983

Isolation and characterization of subclones of L1210 murine leukemia with different sensitivities to various cytotoxic agents.

Two subclones of L1210 murine leukemia (L1210-46.1 and L1210-56.3) were isolated in the absence of selective agents. Subclone 56.3 appeared to be more sensitive than was subclone 46.1 to treatment with dexamethasone, 1-beta-D-arabinofuranosyl cytosine, vincristine, and X-irradiation. No differences between the parent cells and the two subclones could be observed in population-doubling time, cloning efficiency, number of chromosomes, and tumorigenic potential in DBA/2 mice. The subclones did not differ in the per cell number of glucocorticoid receptor sites. Animal experiments revealed an increase in life span of 65% in mice inoculated with cells from subclone 46.1 and of 130% of mice with subclone 56.3 after treatment with 1-beta-D-arabinofuranosylcytosine. The present results indicate that the L1210 wild-type murine leukemia cells contained stable subpopulations with a different but collateral sensitivity to various cytotoxic treatments. It is postulated that differences in drug sensitivity between cells are partly determined by cellular properties which are independent of the mechanism of action of any specific treatment.

Animals↗

PubMed1999

Combined cytotoxic effects of tumor necrosis factor-alpha with various cytotoxic agents in tumor cell lines that are drug resistant due to mutated p53.

Several studies suggest that tumor necrosis factor-alpha (TNF) is able to overcome drug resistance in tumors. Whether TNF is able to do so in tumor cell lines that are drug resistant due to a mutation in the tumor suppressor gene p53 is unclear. Therefore, we studied the in vitro cytotoxic effects of TNF combined with various cytotoxic agents in a model consisting of a human ovarian cancer cell line containing endogenous wild-type p53 (wtp53) and sublines that were made drug resistant against various cytotoxic agents by transfection of several forms of mutated p53 (mtp53). Using the microculture tetrazolium assay, the cytotoxic effects of TNF alone, the cytotoxic agents VM-26, melphalan, cisplatin, vinblastine, paclitaxel, and mitoxantrone, plus the combined effects of 10 ng/ml TNF added 30 min before various concentrations of the cytotoxic agents were established. Compared with the control cell line (A2780/cmv), two cell lines transfected with mtp53 (A2780/m248 and A2780/m273) showed increased resistance against several cytotoxic agents but also an enhanced sensitivity to TNF. Interaction of TNF with the cytotoxic drugs was additive in the drug-sensitive control cell line as well as in the drug-resistant sublines. However, because of the increased sensitivity of A2780/m248 to TNF at the dose used for the combinations, the combination of TNF with several cytotoxic drugs reduced the level of resistance in A2780/m248 compared with the control cell line A2780/cmv. In conclusion, this study shows that addition of TNF can ameliorate resistance to cytotoxic agents in a subline that is drug-resistant because of mutated p53. This reduction in resistance by TNF is not due to synergistic interaction, but to collateral sensitivity to TNF.

Antineoplastic Agents↗

PubMed1997

Mechanism of increased sensitivity to etoposide in a mitomycin C-resistant human bladder cancer cell line.

The mechanism of increased sensitivity to etoposide (VP-16) in a human bladder cancer cell line (J82/MMC-2), which is >9-fold more resistant to mitomycin C (MMC) compared with parental cells (J82/WT), was investigated. Colony formation assays, following 1 hr drug exposure, revealed that about a 2.2-fold higher concentration of VP-16 was required to kill 50% of the J82/WT cell line compared with J82/MMC-2. The MTT assays, following continuous drug exposure, also showed that the J82/MMC-2 cell line was significantly more sensitive to VP-16 compared with J82/WT. Accumulation of VP-16 was significantly higher in the J82/MMC-2 cell line compared with J82/WT at every drug concentration tested. Likewise, intracellular VP-16 retention was significantly higher in the J82/MMC-2 cell line compared with J82/WT when drug uptake was measured as a function of varying incubation time and at a fixed VP-16 concentration. The efflux of VP-16 from the J82/MMC-2 cell line was equivalent to that from J82/WT. In agreement with the results of drug uptake studies, the levels of VP-16-induced protein-DNA complexes were markedly higher in the J82/MMC-2 cell line compared with J82/WT. The catalytic activity of topoisomerase II (topo II) in 0.35 M NaCl nuclear extract of J82/WT cells was equivalent to that of J82/MMC-2. The levels of topo II mRNA were also comparable in these cells. Our results suggest that the mechanism responsible for the collateral sensitivity of the J82/MMC-2 cell line to VP-16 may be attributable to a relatively higher drug accumulation in this cell line compared with parental cells.

Antineoplastic Agents, Phytogenic↗

PubMed2001

Collateral sensitivity to gemcitabine (2',2'-difluorodeoxycytidine) and cytosine arabinoside of daunorubicin- and VM-26-resistant variants of human small cell lung cancer cell lines.

Multidrug resistance (MDR), characterized by a cross-resistance to many natural toxin-related compounds, may be caused either by overexpression of a drug efflux pump such as P-glycoprotein, (P-gP), multidrug resistance proteins MRP1-3, or BCRP/MXR or, in the case of DNA topoisomerase II active drugs, by a decrease in the enzymatic activity of the target molecule termed altered topoisomerase MDR (at-MDR). However, human small cell lung carcinoma (SCLC) cell lines showed a collateral sensitivity to 2',2'-difluorodeoxycytidine (gemcitabine, dFdC) and 1-beta-D-arabinofuranosylcytosine (ara-C). H69/DAU, a daunorubicin (DAU)-resistant variant of H69 with a P-gP overexpression, and NYH/VM, a VM-26 (teniposide)-resistant variant of NYH with an at-MDR, were both 2-fold more sensitive to gemcitabine and 7- and 2-fold more sensitive to ara-C, respectively. MDR variants had a 4.3- and 2.0-fold increased activity of deoxycytidine kinase (dCK), respectively. dCK catalyzes the first rate-limiting activation step of both gemcitabine and ara-C. In addition, deoxycytidine deaminase, responsible for inactivation of dFdC and ara-C, was 9.0-fold lower in H69/DAU cells. The level of thymidine kinase 2, a mitochondrial enzyme that can also phosphorylate deoxycytidine and gemcitabine, was not significantly different between the variants. These differences most likely caused an increased accumulation of the active metabolites (dFdCTP, 2.1- and 1.6-fold in NYH/VM and H69/DAU cells, respectively) and of ara-CTP (1.3-fold in NYH/VM cells). Ara-CTP accumulation was not detectable in either H69 variant. The pools of all ribonucleoside and deoxyribonucleoside triphosphates were at least 3- to 4-fold higher in the NYH variants compared to the H69 variants; for dCTP and dGTP this difference was even larger. The higher ribonucleotide pools might explain the >10-fold higher accumulation of dFdCTP in NYH compared to H69 variants. Since dCTP is low, H69 cells might not need a high ara-CTP accumulation to inhibit DNA polymerase. This might be related to the lack of ara-CTP in H69 variants. In addition, the increased CTP, ATP, and UTP pools in the MDR variants might explain the increased ara-CTP and dFdCTP accumulation. In conclusion, the MDR variants of the human SCLC cell lines were collaterally sensitive due to an increased dCK activity, and consequently an increased ara-CTP and dFdCTP accumulation.

Adenosine Triphosphate↗

PubMed1991

Resistance to the antimitotic drug estramustine is distinct from the multidrug resistant phenotype.

Following EMS mutagenesis, three estramustine (EM) resistant DU 145 human prostatic carcinoma cell lines were clonally selected by exposure to incrementally increasing concentrations of the drug. Although only low levels of resistance (approximately 3-fold) were attainable, this resistance was stable in the absence of continuous drug exposure. These EM-resistant clones (EMR 4,9,12) did not exhibit cross resistance to vinblastine, taxol, or adriamycin, and had collateral sensitivity to cytochalasin B. None of the lines had elevated expression of P-glycoprotein mRNA or glutathione S-transferase activity, suggesting a phenotype distinct from the classic multi-drug resistance phenotype. This conclusion was supported further by the observation that two MDR cell lines (FLC mouse erythroleukaemic and SKOV3 human ovarian carcinoma cells) showed sensitivity to EM. Fluorescent activated cell sorting analysis of the effects of EM on cell cycle traverse revealed that at EM concentrations up to 20 microM an increasing percentage of wild type cells were blocked in G2/M; no such effect occurred in EMR lines. Differential interference contrast microscopy was employed to study EM's effect on mitosis. EMR lines were able to form functional, albeit smaller, spindles at EM concentrations that resulted in chromosomal disorganisation and inhibition of mitotic progression in wild type cells. EMR lines were able to progress through mitosis and cytokinesis at the same rate as untreated cells. Tritiated EM was used to evaluate potential drug uptake/efflux mutations in ERM clones. EMR 4 and 9 incorporate less EM than wild type cells; however, they have significantly decreased cellular volumes. The initial efflux rate constants for EMR clones were greater than for wild type cells. Within 5 min greater than 70% of the drug was lost from resistant cells compared to a 50% loss by the wild type. Although the specific mechanisms of resistance have yet to be defined, the lack of collateral resistance to other MDR/anti-microtubule agents could serve as the basis for the clinical use of EM in combination chemotherapy.

Anti-Bacterial Agents↗

PubMed1992

Expression of collateral sensitivity to cisplatin, methotrexate, and fluorouracil in a human ovarian carcinoma cell line following exposure to fractionated x-irradiation in vitro.

Examples of collateral sensitivity, even in experimental tumor systems, remain few. Preliminary data from this laboratory indicated that certain tumor cells expressed increased sensitivity to cisplatin after exposure in vitro to x-irradiation. To further clarify whether the type of fractionated radiation procedure used clinically can induce hypersensitivities to certain antitumor drugs we have pre-exposed the human ovarian carcinoma cell line JA-T/P derived from a tumor from an untreated patient to fractionated x-irradiation (total dose 50 Gy) in vitro. The resultant subline JA-T/DXR-10 expressed collateral sensitivity to cisplatin (CDDP), methotrexate (MTX) and fluorouracil (5-FU), but not to acute x-irradiation. Hypersensitivity to CDDP was associated with decreased activity of DNA polymerase beta (3.5-fold, P less than .01), but unaltered glutathione metabolism. Pre-incubation with cyclosporin A or with 3-aminobenzamide significantly enhanced (twofold, P less than .01) CDDP-induced cytotoxicity in JA-T/P cells, but not in the DXR-10 subline. Consistent with MTX hypersensitivity dihydrofolate reductase activity was significantly decreased (2.9-fold, P less than .01). Despite collateral sensitivity to 5-FU, however, thymidylate synthase activity was increased (twofold, P less than .05) suggesting alternative mechanisms for 5-FU-induced cytotoxicity in these JA-T/DXR-10 cells. These data demonstrate that DNA repair and associated reduced folate metabolism can be modified not only by drugs but also by fractionated x-irradiation.

Cisplatin↗