Background: To investigate the relationship between MDR-1 gene expression and drug resistance in lung cancer cells.
Methods: The multidrug resistant cell line (3LL-MDR-1) was established by transfecting human MDR-1 gene expressing vector into a murine Lewis lung cancer cell line (3LL) . Drug resistance and the effect of valapamil (VLP) on the resistance were evaluated by MTT assay. The expression of MDR-1 gene product , P-gp , was measured immunohistochemically. The influx and efflux of Rhodamine 123 was tested with flow cytometry.
Results: The MDR cell line expressing P-gp was established , which exhibited a typical drug resistance to vincristine (VCR) , vindesin (VDS) , etoposide (VP-16) , mitomycin (MMC) , taxol and navelbine (NOR) . Valapamil was able to reverse the resistance of the gene-transfected cells and the reversion was dose-dependent. Flow cytometric analysis showed that the resistant cells had much higher ability to export Rhodamine 123 than the parent cells did. The expression of P-gp protein was visualized immunohistochemically.
Conclusions: The results indicate that drug resistance in lung cancer cells is closely related to the MDR-1 gene expression.