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Characteristics of P388/VMDRC.04, a simple, sensitive model for studying P-glycoprotein antagonists
J M Yang1, S Goldenberg, M M Gottesman
1Department of Medicine, Cancer Institute of New Jersey, Robert Wood Johnson Medical School, Piscataway 08854.
Abstract:
Cross-resistance to chemotherapeutic drugs is a significant problem in the treatment of patients with cancer. The discovery that this phenomenon is associated with the overexpression of a membrane glycoprotein, P-glycoprotein, which acts as a drug efflux pump, has provided a new target for drug development. To develop a model for identifying new compounds which can block the function of P-glycoprotein, we infected P388 mouse leukemic cells with a retrovirus containing a cloned human MDR1 complementary DNA. The new cell line, P388/VMDRC.04, incorporated and overexpressed the human gene as evidenced by Southern blots, increased mRNA and protein synthesis, and recognition by the MRK16 monoclonal antibody. P388/VMDRC.04 was cross-resistant to colchicine, vincristine, and doxorubicin, and the degree of resistance correlated with a reduction in cellular drug accumulation. Unlike many cell lines selected for resistance by growth in increasing concentrations of drug for prolonged periods of time, these cells did not show alternative mechanisms of resistance such as increased synthesis of glutathione or alterations in topoisomerase II. In addition, the sensitivity of P388/VMDRC.04 cells was completely restored by cyclosporin A and trans-flupenthixol. P388/VMDRC.04 cells were subcloned and 10 clones were picked for in vivo evaluation. One subclone grew similarly to parental cells in female BALB/c x DBA/2 F1 mice and showed no responsiveness to therapeutic doses of vincristine or etoposide. The combination of vincristine with cyclosporin A significantly increased the survival of mice inoculated with P388/VMDRC.04 cells. The availability of a cell line that displays the MDR phenotype, overexpresses human P-glycoprotein, but does not contain alterations in at least two well-defined alternative mechanisms of resistance, and that can be grown in simple animal models should facilitate the development of new agents active against this form of chemotherapeutic drug resistance.
Insights
Researchers developed a new cell line overexpressing P-glycoprotein to model multidrug resistance (MDR). This model aids in discovering new drugs to overcome chemotherapy resistance by targeting P-glycoprotein drug efflux pumps.
Area of Science:
- Molecular Biology
- Cancer Research
- Pharmacology
Background:
- Multidrug resistance (MDR) in cancer chemotherapy is a major clinical challenge.
- P-glycoprotein, a membrane efflux pump, is a key mediator of MDR.
- Targeting P-glycoprotein offers a strategy for overcoming drug resistance.
Purpose of the Study:
- To develop a novel cell line model for identifying compounds that inhibit P-glycoprotein function.
- To create a model that accurately reflects human multidrug resistance phenotypes.
Main Methods:
- Infection of P388 mouse leukemic cells with a retrovirus carrying human MDR1 cDNA.
- Characterization of the resulting cell line (P388/VMDRC.04) for P-glycoprotein overexpression.
- Evaluation of drug resistance profiles and mechanisms in the new cell line.
- In vivo testing of drug efficacy in animal models.
Main Results:
- The P388/VMDRC.04 cell line successfully overexpressed human P-glycoprotein and exhibited cross-resistance to multiple chemotherapeutic agents.
- This cell line demonstrated reduced drug accumulation and lacked common alternative resistance mechanisms.
- Drug sensitivity was restored by P-glycoprotein inhibitors like cyclosporin A.
- In vivo studies showed that combining vincristine with cyclosporin A improved survival in mice bearing P388/VMDRC.04 tumors.
Conclusions:
- The P388/VMDRC.04 cell line serves as a valuable model for studying P-glycoprotein-mediated multidrug resistance.
- This model facilitates the development of novel therapeutic agents to combat chemotherapy resistance.
- The findings support combination therapies involving P-glycoprotein inhibitors for enhanced cancer treatment.