Overexpression of MDR1 and survivin, and decreased Bim expression mediate multidrug-resistance in multiple myeloma cells.

Multidrug resistance represents a major obstacle for the chemotherapy of a wide variety of human tumors. To investigate the underlying mechanisms associated with resistance to anti-cancer drugs, we established anti-cancer drug-resistant multiple myeloma (MM) cell lines RPMI8226/ADM, RPMI8226/VCR, RPMI8226/DEX, and RPMI8226/L-PAM, the 50% inhibitory concentration values of which were 77-, 58-, 79-, and 30-fold higher than their parental cell lines, respectively. The resistant cell lines overexpressed MDR1 and survivin, or showed decreased Bim expression. These results indicated that regulating these factors with inhibitors might be a viable approach to increasing the susceptibility of quiescent MM cells to chemotherapy.