SEARCH · PubMed Health

Results for “Drug Collateral Sensitivity”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 181 records · Page 10Linked to original sources

PubMed2005

Nitric oxide (NO)- and nitroxyl (HNO)-generating diazeniumdiolates (NONOates): emerging commercial opportunities.

Diazeniumdiolate ions are convenient and, for a variety of applications, uniquely advantageous nitric oxide (NO) dosage forms. Ionic diazeniumdiolates generate bioactive NO in physiological fluids truly spontaneously (i. e., without metabolism or redox activation), with reliable half-lives ranging from 2 seconds to 20 hours depending on the ion's structure. They are generally simple-to-prepare solids with excellent shelf life and high NO content - up to 40% by weight. Very importantly from the pharmaceutical point of view, the ionic diazeniumdiolates can be easily derivatized to prodrug forms that can be activated for NO release enzymatically, photolytically, or by slowed hydrolysis, allowing for rational design of strategies for targeting pharmacological delivery of NO to sites of need without unwanted collateral exposure of other NO-sensitive compartments. In addition to their world-wide sale for use in probing the chemical biology of NO, published proof-of-concept studies with diazeniumdiolates suggest several more lucrative applications. These include: converting existing drugs and biologicals to NO-releasing form to improve performance and/or extend patent life; diazeniumdiolating medical devices for improved biocompatibility; anticancer drug discovery; use as surgical aids and for wound repair; field generation of NO gas; and non-medical uses such as extending the post-harvest life of cut flowers. Future work aimed at exploiting the full clinical potential of diazeniumdiolate technology will be pursued in this laboratory and strongly encouraged in others, with a concurrent fundamental research effort to broaden the knowledge base from which further opportunities can be inferred [e. g., exploiting the very recent finding that some diazeniumdiolates appear to offer a versatile platform from which nitroxyl (HNO)-generating prodrugs can be developed].

Animals↗

PubMed1991

Antitumor spectrum of deoxyspergualin and its lack of cross-resistance to other antitumor agents.

Antitumor activities of 15-deoxyspergualin (NKT-01), an analogue of spergualin (SGL), were examined in cultured tumor cells, transplantable murine tumors, and human tumor xenografts in nude mice. NKT-01 exhibited strong antitumor activity specifically against leukemias both in vitro and in vivo. Moreover, it also showed activity against AH66F hepatoma, M5076 fibrosarcoma and MH134 hepatoma. However, antitumor activity of NKT-01 against other non-leukemic tumors was marginal. Effective dose range of NKT-01 in sensitive tumors was so wide that the largest chemotherapeutic indexes were produced by NKT-01 in P388 and L1210 leukemias among 15 antitumor agents examined. The efficacy of NKT-01 against doxorubicin- and cytosine arabinoside-resistant P388 leukemias was comparable to that against parental sensitive P388 leukemia. NKT-01 also retained activity against other p388 leukemia sublines resistant to cisplatin, 5-fluorouracil or nimustine, although the effect was slightly decreased. In addition, in the in vitro and in vivo experiments using NKT-01-resistant P388 and SGL-resistant L1210(IMC) leukemias, no cross-resistance was observed. Moreover, collateral sensitivity was observed especially to alkylating agents in animal study.

Animals↗

PubMed1983

Collateral sensitivity to N-(phosphonacetyl)-L-aspartic acid in a line of P388 leukemia cells selected for resistance to L-(alpha S, 5S)-alpha-amino-3- chloro-4,5-dihydro-5-isoxazoleacetic acid (acivicin).

Administration of N-(phosphonacetyl)-L-aspartic acid (PALA) is ineffective in treating mice bearing the parent P388 leukemia line; however, such treatment becomes highly effective when a cell line, P388/ACIA, derived from P388/0 was selected for resistance to another antimetabolite, acivicin. The observed phenomenon of collateral sensitivity is associated with a significantly higher inhibition of the specific activity of carbamyl phosphate synthetase II, pyrimidine nucleoside kinases, adenine phosphoribosyl transferase, and hypoxanthine phosphoribosyl transferase in the PALA-sensitive line, P388/ACIA. Twenty-four hr following administration of PALA, 200 mg/kg, the 10% lethal dose i.p. to tumor-bearing mice, the intracellular concentrations of uridine triphosphate and cytidine triphosphate were decreased in the P388/ACIA, PALA-sensitive cells, whereas no significant change in the corresponding nucleotide pool sizes was observed in P388/0, PALA-resistant line. Moreover, the purine nucleotide pool demonstrated a significant expansion of adenosine triphosphate and guanosine triphosphate only in the P388/ACIA line following a similar treatment with PALA. It is proposed that the imbalance in the generation of pyrimidine and purine nucleoside triphosphate pools may explain the observed collateral sensitivity to PALA in P388/ACIA leukemia line.

Adenine Phosphoribosyltransferase↗

PubMed1979

Genetic control of enhanced mutability of mitochondrial DNA and gamma-ray sensitivity in Saccharomyces cerevisiae.

Five nuclear mutants enhancing the spontaneous mutation rate of mtDNA have been isolated in Saccharomyces cerevisiae. These mutators fall into five complementation groups and are located at five genetic loci different from rad50 to rad57 loci. Three mutants (gam1, gam2, and gam4), insensitive or weakly sensitive to gamma-rays, exhibit increased frequency of spontaneous production of mutants with large deletions of the mtDNA (p-) and of all tested mitochondrial drug-resistant mutants. Two other mutants (gam3 and gam5), highly sensitive to gamma-rays, increase only the mutation rate of particular alleles of the mtDNA. The mutant gam5 enhances only the production of p- and erythromycin-resistant clones. The mutant gam3 exhibits an enhanced rate of oligomycin-resistant clones as well as a collateral increase of nuclear mutability. The existence of gam3 and gam5 mutants indicates that at least two common steps control both nuclear DNA repair and the mutability of particular alleles of the mtDNA. However, the general spontaneous mutability of the mtDNA includes at least three steps not involved in the repair of nuclear DNA, as revealed by the gam1, gam2, and gam4 mutations.

Chromosome Mapping↗

PubMed1988

Changes in drug sensitivity of a human astrocytoma clone previously treated with 1-(2-chloroethyl)-3-(4-methylcyclohexyl)-1-nitrosourea in vitro.

We have shown in earlier studies that repeated weekly exposures of a human astrocytoma clone (AST 3-4) to MeCCNU (10 micrograms/ml for 1 h per week) produced a linear decrease in survival over the first 3 weekly treatments. But, after that time these cells became progressively more resistant to the 10 micrograms/ml concentration of the agent. In the studies reported here we show that these previously treated cells were also less responsive to other doses ranging from 1 to 30 micrograms MeCCNU/ml. This change in sensitivity to MeCCNU was accompanied by collateral changes in response to other agents: resistance to BCNU and Galactitol, increased sensitivity to Adriamycin, and no change to ionizing radiation. These experiments suggest that once repeated treatments with a single agent cause a tumor cell population to become more resistant, sensitivity to other agents may also change unpredictably.

Astrocytoma↗

PubMed1997

Cross-resistance to antifolates in multidrug resistant cell lines with P-glycoprotein or multidrug resistance protein expression.

Resistance to some (lipophilic) antifolates has been associated with P-glycoprotein (P-gp)-mediated multidrug resistance (MDR). A possible relationship with non-P-gp MDR has not been established. We studied resistance to antifolates in SW-1573 human lung carcinoma cells, a P-gp overexpressing variant SW-1573/2R160 and a multidrug resistance protein (MRP) overexpressing variant SW-1573/2R120. In this study, thymidylate synthase (TS) inhibitors with different properties concerning the efficiency of membrane transport and the efficiency of polyglutamylation were tested for cross-resistance in SW-1573/2R120 and SW-1573/2R160 cells. Growth inhibition patterns in this cell line panel were measured by the Sulforhodamine B (SRB) assay. Resistance factors for TS inhibitors were: 2.4 and 0.4 for 5-fluorouracil (5FU), 18.8 and 8.8 for ZD1694, 17 and 0.7 for AG337, and 40 and 8.3 for BW1843U89 in SW-1573/2R160 and SW-1573/2R120, respectively. This study showed changes in the TS enzyme kinetics during the induction of doxorubicin resistance in both SW-1573 variants, resulting in 2-fold lower Km values for 2'-deoxyuridine-5'-monophosphate (dUMP) in both resistant variants compared to the parental cell line. TS activity, TS protein induction and TS mRNA expression all had 2-fold increased in the SW-1573/2R120 compared to the SW-1573/2R160. 3H-MTX influx was 2-fold lower in SW-1573/2R160 cells compared to SW-1573/2R120 and SW-1573 cells. In the SW-1573/2R160 cell line, an aberrant intracellular trafficking towards the target TS was observed, compared to SW-1573/2R120 and SW-1573 cells as measured by the TS in situ assay. The rate of TS inhibition by the TS inhibitors used in this study was similar in all cell lines. In conclusion, collateral sensitivity to 5FU and the lipophilic AG337 and cross-resistance to other antifolates were observed in non-P-gp MDR SW-1573/2R120 cells, as well as resistance to all antifolates in P-gp SW-1573/2R160 cells. The mechanism of resistance in SW-1573/2R160 cells possibly involves reduced influx and changes in intracellular trafficking routes. For the SW-1573/2R120 cell line, several changes related to the TS enzyme possibly play a role in the observed cross-resistance and collateral sensitivity pattern.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1995

Characterisation of a human small-cell lung cancer cell line resistant to the DNA topoisomerase I-directed drug topotecan.

Camptothecins are DNA topoisomerase I-directed anti-tumour drugs with a novel mechanism of action. Topotecan (TPT), a hydrophilic derivative of camptothecin, is currently undergoing phase II clinical trials in small-cell lung cancer (SCLC). Human SCLC OC-NYH cells were made more than 6-fold resistant to topotecan by stepwise drug exposure and resistance was stable for 70 passages without drug. NYH/TPT cells had half the topoisomerase I level and activity of wild-type cells. However, no difference in camptothecin or topotecan inhibition of topoisomerase I-mediated DNA relaxation was found, indicating that the enzyme itself was unchanged in the resistant cell. In NYH/TPT cells, topoisomerase II alpha and beta levels were increased approximately 2-fold. Accordingly, the topoisomerase II-directed drug etoposide (VP-16) induced an increased number of DNA single-strand breaks in NYH/TPT cells. However, sensitivity to different topoisomerase II-targeting agents in NYH/TPT cells varied from increased to decreased, indicating a role for as yet unidentified factors acting on the pathway to cell death after topoisomerase II-induced DNA damage has occurred. Of 20 anti-cancer agents tested, only hydroxyurea showed marked collateral hypersensitivity in NYH/TPT cells.

Antigens, Neoplasm↗

PubMed2003

Antifolate resistance associated with loss of MRP1 expression and function in Chinese hamster ovary cells with markedly impaired export of folate and cholate.

Export of folates from a Chinese hamster ovary PyrR100 cell line is markedly impaired, resulting in expansion of cellular folate pools and high-level antifolate resistance. We now report that MRP1 expression is absent in PyrR100 cells along with a marked decrease in MRP5 expression with 3-fold cross-resistance to thiopurines. PyrR100 and wild-type cells had comparable low levels of MRP2 expression; both lacked the breast cancer resistance protein. PyrR100 cells showed a 4-fold decrease in cholate (an MRP substrate) efflux with a 6-fold increase in cellular cholate accumulation compared with wild-type cells. Prostaglandin A1 increased cholate accumulation in wild-type cells to levels comparable with PyrR100 cells. Calcein (an MRP1 substrate) fluorescence increased 5-fold in PyrR100 cells; probenecid increased the intracellular calcein level in wild-type cells to that of PyrR100 cells. Consistent with the loss of MRP1 expression, PyrR100 cells showed modest collateral sensitivity to cholate, etoposide, doxorubicin, and vincristine. Transfection of MRP5 into PyrR100 cells did not alter sensitivity to pyrimethamine or MTX but restored sensitivity to mercaptopurines, indicating that decreased MRP5 expression did not play a role in antifolate resistance. Hence, although MRP-mediated anticancer drug resistance has been associated with gain of function (i.e., overexpression), this is the first report that loss of MRP1 efflux function can expand intracellular folate pools to result in acquired antifolate resistance. The data also suggest that MRP1, and possibly other MRPs that transport folates, can play a role in the maintenance of cellular folate homeostasis.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1987

Differential expression of collateral sensitivity or resistance to cisplatin in human bladder carcinoma cell lines pre-exposed in vitro to either X-irradiation or cisplatin.

Two sublines were derived from a human bladder carcinoma continuous cell line (RT112-P), one by exposure to fractionated X-irradiation (RT112-DXR8) and the other by continuous exposure to cisplatin (RT112-CP). RT112-DXR8 cells were 1.6- to 2-fold more sensitive to cisplatin and 2 analogues, carboplatin and iproplatin, compared with the parental line, whereas RT112-CP cells were 1.6- to 2.8-fold more resistant to these agents. Uptake of 195mcisplatin was elevated 1.4-fold in RT112-DXR8 cells compared with RT112-P cells whereas uptake into RT112-CP cells was similar to that of the parental line. Binding of 195mcisplatin to DNA was similar in all 3 lines. Levels of reduced glutathione were significantly elevated in RT112-CP cells and significantly reduced in RT112-DXR8 cells compared with the parental cells. In addition, activities of glutathione reductase and glutathione peroxidase were higher in RT112-CP cells than in the parental cells whereas the activity of glutathione-S-transferase was similar in all 3 cell lines. A 2.5-fold greater induction of DNA-DNA interstrand crosslinks occurred in RT112-DXR8 cells compared with the parental line, whereas crosslinking in RT112-CP cells, whilst initially similar to that seen in RT112-P cells, was significantly elevated at later times. These findings suggest that mechanisms associated with the expression of resistance and collateral sensitivity to cisplatin may differ.

Cell Line↗

PubMed1996

[The pathophysiological mechanisms of disorders of cerebral circulation and the new directions in their prevention and treatment].

The contribution of Laboratory of Nervous System's Experimental Pathology (Institute of Neurology of Russian Academy of Medical Sciences) to cerebrovascular circulation investigations is described. The following questions were considered: cerebral circulation in cerebrovascular disturbances, collateral circulation in the "turned off" state of different brain arteries, and immunological brain alterations as the result of brain organic diseases. Results of the investigation of the damaging effect of acute increase in arterial pressure as well as individual sensitivity to brain ischemia and to drug administration were presented. The particular importance of researches of blood circulation biomechanics as well as of factors of its normalization were also emphasized.

Academies and Institutes↗

PubMed1992

Mechanisms of collateral sensitivity to fluorouracil of a cis-diamminedichloroplatinum(II)-resistant human non-small lung cancer cell line.

A cisplatin(CDDP)-resistant subline of a human lung cancer cell line, PC-7/CDDP, was 4.7-fold more resistant to CDDP than the parent line in a colony-forming assay. The sensitivity of this cell line to anthracyclines, vinca-alkaloid, etoposide, mitomycin C, and bleomycin was similar to that of the parental line, PC-7. However, PC-7/CDDP exhibited 4-fold higher sensitivity to fluorouracil (FUra). Possible mechanisms associated with the collateral sensitivity to FUra were studied in PC-7/CDDP cells. The sensitivity of both cell lines to FUra did not correlate with the effect of FUra on RNA. On the other hand, FUra induced a greater reduction in dTTP pools and more single strand breaks in PC-7/CDDP than in PC-7 cells. These results suggest that the pathway for de novo deoxyribonucleotide synthesis may be a target for FUra in PC-7/CDDP cells. However, inhibition of thymidylate synthase after FUra treatment did not correlate with the DNA-directed activity of FUra. Based on the above findings, the decreased salvage synthesis of dTTP was considered a possible mechanism of the greater reduction of dTTP pools in PC-7/CDDP cells. However, the activity of dThd kinase was the same in both cell lines. In the presence of physiological concentrations of exogenous dThd in the serum, uptake of dThd was less in PC-7/CDDP cells than that in PC-7 cells. Our data suggest that FUra-induced cytotoxicity in PC-7/CDDP cells is associated with the inhibition of dTTP synthesis and that the decreased uptake of dThd is a possible mechanism of the collateral sensitivity to FUra in PC-7/CDDP cells.

Adenocarcinoma↗

PubMed1999

Cisplatin-resistant HeLa cells are resistant to apoptosis via p53-dependent and -independent pathways.

Since HeLa cells possess very little functional p53 activity, they could be originally resistant to genotoxic stress-induced apoptosis. Therefore, it is likely that the drug-resistant cells derived from HeLa cells are more resistant to apoptosis. The aim of this study was to determine whether cisplatin-resistant cells derived from HeLa cells have an apoptosis-resistant phenotype. A cisplatin-resistant cell subline, HeLa/CDDP cells, showed a 19-fold resistance to cisplatin compared with the parent cells. The subline showed a collateral sensitivity to paclitaxel. An equitoxic dose (IC50) of cisplatin produced DNA fragmentation in HeLa cells but not in HeLa/CDDP cells. Transfection of wild-type p53 gene enhanced the cytotoxicity of cisplatin and cisplatin-induced apoptosis in HeLa cells but not in HeLa/CDDP cells, although it caused p53 overexpression in both cell lines. The expression of caspase 1 (interleukin-1beta-converting enzyme, ICE) mRNA and the overexpression of bax protein were observed only in HeLa cells. Paclitaxel-induced DNA fragmentation appeared less in HeLa/CDDP cells than in HeLa cells. p53 gene transfection did not affect the extent of DNA fragmentation in either cell line, suggesting that paclitaxel may induce p53-independent apoptosis. These findings suggest that HeLa/CDDP cells may have an acquired phenotype that is resistant to p53-dependent and -independent apoptosis.

Antineoplastic Agents↗

PubMed2004

Enhanced in vitro invasiveness and drug resistance with altered gene expression patterns in a human lung carcinoma cell line after pulse selection with anticancer drugs.

The human lung carcinoma cell line DLKP was exposed to sequential pulses of 10 commonly used chemotherapeutic drugs (VP-16, vincristine, taxotere, mitoxantrone, 5-fluorouracil, methotrexate, CCNU, BCNU, cisplatin and chlorambucil); resulting cell lines exhibited resistance to the selecting agents (ranging approx. 1.5- to 36-fold) and, in some cases, cross-resistance to methotrexate (approx. 1.4- to 22-fold), vincristine (1.6- to 262-fold), doxorubicin (Adriamycin, approx. 1.1- to 33-fold) and taxotere (approx. 1.1- to 36-fold). Several of the variants displayed collateral sensitivity to cisplatin. A marked increase in in vitro invasiveness and motility was observed with variants pulsed with mitoxantrone, 5-fluorouracil, methotrexate, BCNU, cisplatin and chlorambucil. There was no significant change in invasiveness of cells pulsed with VP-16, vincristine, taxotere or CCNU. All of the pulse-selected variants showed elevated levels of MDR-1/P-gp protein by Western blot analysis, although mdr-1 mRNA levels were not increased (except for DLKP-taxotere). In DLKP-taxotere, MRP1 protein levels were also greatly elevated, but mrp1 mRNA levels remained unchanged. BCRP was upregulated in DLKP-mitoxantrone at both the mRNA and protein levels. Gelatin zymography, Western blot and RT-PCR showed that DLKP and its variants secreted MMPs 2, 9 and 13. MMP inhibition assays suggested that MMP-2 plays a more important role than MMPs 9 and 13 in cell invasion of these DLKP drug-resistant variants in vitro. These results indicate that drug exposure may induce not only resistance but also invasiveness in cancer cells.

Antineoplastic Agents↗

PubMed2001

Modulation of endogenous beta-tubulin isotype expression as a result of human beta(III)cDNA transfection into prostate carcinoma cells.

Increases of individual beta tubulin isotypes in antimicrotubule drug resistant cell lines have been reported by several laboratories. We have previously described elevations in beta(III)and beta(IVa)isotypes in estramustine and paclitaxel resistant human prostate carcinoma cells. To investigate further the function of beta tubulin isotypes in antimicrotubule drug response, human prostate carcinoma cells that normally have very low to undetectable levels of beta(III)were stably transfected with beta(III)cDNA in pZeoSV system. An 18 bp haemagglutinin (HA) epitope tag was added at the 3' end prior to cloning into the vector. Cells were transfected with pZeoSV or pZeoSV-beta(III)plasmids and selected in the presence of Zeocin. Immunofluorescent staining of the transfectant cells have shown significant expression and incorporation of HA-tagged beta(III)tubulin into cellular microtubules. Quantitation of Western blots revealed the HA-tagged beta(III)levels to be approximately 7-fold higher than the vector control cells. RT-PCR analysis confirmed the increase at the transcript level and also revealed a collateral increase of beta(II)and beta(IVb)transcripts. Cell viability assays indicated that sensitivity of beta(III)transfected cells to various antimicrotubule agents was similar to vector transfected cells: IC50 values for estramustine, paclitaxel, colchicine and vinblastine were 4 microM, 4 nM, 22 nM and 2 nM, respectively for both cell lines. Thus, overexpression of beta(III)isotype in human prostate carcinoma cells by stable transfection failed to confer antimicrotubule drug resistance to these cells. Counterregulatory increases of endogenous beta(II)and beta(IVb)tubulin isotypes in these beta(III)transfected cells may be a compensatory mechanism used by the cells to overcome the effects of elevated beta(III)levels on the cellular microtubules. These results highlight the difficulty in isolating the contribution of single tubulin isotypes in drug response studies.

Antineoplastic Agents↗

PubMed1987

Cross-resistance of drug-resistant murine leukemias to deoxyspergualin (NSC 356894) in vivo.

Deoxyspergualin, the 15-deoxy derivative of the antibiotic spergualin, is a novel guanidino analog structurally related to spermine. Deoxyspergualin has significant activity in selected experimental tumor models, and clinical trials have been initiated. Described here are in vivo evaluations of the therapeutic activity of deoxyspergualin against murine leukemia lines specifically resistant to eight clinically useful antitumor drugs. These were P388 lines resistant to doxorubicin, vincristine, L-phenylalanine mustard, cisplatin, ara-C, and methotrexate and L1210 lines resistant to 5-FU, L-phenylalanine mustard, and cyclophosphamide. Sensitivity to deoxyspergualin was evaluated in parallel comparisons of each resistant leukemia to the sensitive line from which it had been derived. All experiments were repeated at least once for confirmation of results. Responses were quantitated in terms of the change in tumor cell numbers from the beginning of treatment to the end of treatment as estimated from the median survival times of dying mice. The results indicated that P388 leukemia resistant to cisplatin (P388/DDPt) was cross-resistant to deoxyspergualin. No cross-resistance was observed in leukemias resistant to doxorubicin, vincristine, ara-C, methotrexate, or cyclophosphamide. L1210 resistant to 5-FU (L1210/5-FU) was collaterally sensitive to deoxyspergualin. Although cross-resistance was also observed in P388/L-PAM, L1210/L-PAM retained sensitivity to deoxyspergualin. Total glutathione concentrations in P388/L-PAM and L1210/L-PAM provided no apparent explanation for this unexpected result. It may be tentatively concluded that resistance to cisplatin, L-PAM, or other DNA alkylators or cross-linkers may increase the potential for cross-resistance to deoxyspergualin. This conclusion requires verification with additional alkylating agents, with drug-resistant human tumor cell lines, and with prospective clinical studies.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed2001

Novel mechanism of cellular DNA topoisomerase II inhibition by the pyranonaphthoquinone derivatives alpha-lapachone and beta-lapachone.

PURPOSE: The mechanisms of intracellular topoisomerase II inhibition by the pyranonaphthoquinone derivatives alpha-lapachone and beta-lapachone were studied. METHODS: Cell-based mechanistic studies were designed based on the in vitro mechanisms [17] and primarily involved the use of cultured KB (nasopharyngeal tumor cells) cells and the etoposide-resistant sub-line KB-7d. RESULTS: The KB-7d cells exhibited collateral sensitivity to alpha-lapachone; this supports the possibility of catalytic inhibition of topoisomerase II in the cells. Interestingly, both compounds induced an increase (two- to threefold) in reversible double-stranded DNA breaks in cell lines with a reduced expression of topoisomerase II. However, these drug-induced DNA breaks became irreversible at treatment times greater than 1 h. Studies showed that DNA breaks in KB-7d cells were not caused by endonucleases. Use of antioxidants abolished the appearance of cellular DNA breaks; this suggests involvement of the oxidation-reduction cycle of pyranonaphthoquinones in topoisomerase II inhibition; however, irreversible DNA breaks were not a result of drug-induced oxidative stress. CONCLUSIONS: On the basis of the findings, it is proposed that the compounds, on longer incubation with cells, induce abortive dissociation of topoisomerase II from the DNA, leading to an irreversible accumulation of high molecular weight DNA fragments. In addition to establishing topoisomerase II as an intracellular target of alpha-lapachone, the results suggest that both compounds can be classified as neither typical poisons nor as typical catalytic inhibitors of the enzyme. In summary, both compounds are members of a new inhibitor class, and alpha-lapachone, in particular, can be considered a potential lead for the development of drugs to treat multidrug-resistant cell lines with lower expression of topoisomerase II.

Colony-Forming Units Assay↗

PubMed1986

Folate requirements of methotrexate-resistant human acute lymphoblastic leukemia cell lines.

We studied the folate requirements of a human acute lymphoblastic leukemia cell line, MOLT-3, and methotrexate (MTX)-resistant sublines established in vitro. The requirement of pteroylglutamate (PGA) for optimal cell growth was different for each cell line. With increasing MTX resistance, there was progressive increase in PGA requirements, moving the PGA concentration-cell growth curve (dose-response curve) 1 log order of magnitude to the right. The increases in the requirement of 5-methyltetrahydrofolate (5-methyl-THF) by the resistant sublines were more pronounced than PGA requirement, moving the dose-response curve nearly 3 log orders in magnitude to the right. The concentrations in vitro of 5-methyl-THF required for optimal growth of the MTX-resistant sublines far exceeded the normal serum 5-methyl-THF concentrations known in humans. These observations show that MTX-resistant cell established in vitro in culture media containing PGA instead of 5-methyl-THF, a physiological folate, cannot be expected to grow in vivo. The collateral sensitivity of transport-impaired MTX-resistant sublines to 2,4-diamino-5-methyl-6-[(3',4',5'- trimethoxyanilino) methyl] quinazoline (trimetrexate, TMQ) was negated in the absence of PGA. With the addition of 5-methyl-THF, the parent cells became more resistant than the transport-impaired sublines to TMQ These data indicate that the collateral sensitivity of MTX resistant cells to the substituted 2,4-diaminoquinazoline is due to functional folate deficiency by virtue of the impaired transport of folate.

Biological Transport↗

PubMed1999

Collateral methotrexate resistance in cisplatin-selected murine leukemia cells.

Resistance to anticancer drugs is a major cause of failure of many therapeutic protocols. A variety of mechanisms have been proposed to explain this phenomenon. The exact mechanism depends upon the drug of interest as well as the tumor type treated. While studying a cell line selected for its resistance to cisplatin we noted that the cells expressed a > 25,000-fold collateral resistance to methotrexate. Given the magnitude of this resistance we elected to investigate this intriguing collateral resistance. From a series of investigations we have identified an alteration in a membrane protein of the resistant cell as compared to the sensitive cells that could be the primary mechanism of resistance. Our studies reviewed here indicate decreased tyrosine phosphorylation of a protein (molecular mass = 66) in the resistant cells, which results in little or no transfer of methotrexate from the medium into the cell. Since this is a relatively novel function for tyrosine phosphorylation, this information may provide insight into possible pharmacological approaches to modify therapeutic regimens by analyzing the status of this protein in tumor samples for a better survival of the cancer patients.

Animals↗