Overexpression of survivin via activation of ERK1/2, Akt, and NF-κB plays a central role in vincristine resistance in multiple myeloma cells

The acquisition of anti-cancer drug resistance is a major limitation of chemotherapy for multiple myeloma (MM) and it is thus important to identify the mechanisms by which MM cells develop such drug resistance. In a previous study, we showed that multidrug resistance (MDR) involves the overexpression of MDR1 and survivin in vincristine-resistant RPMI8226/VCR cells. However, the underlying mechanism of MDR remains unclear. In this study, we investigated the mechanism of MDR in RPMI8226/VCR cells, and found that RPMI8226/VCR cells exhibit increased levels of activated ERK1/2, Akt, and NF-κB, while the levels of activated mTOR, p38MAPK, and JNK do not differ between RPMI8226/VCR cells and their vincristine-susceptible counterparts. In addition, the inhibition of ERK1/2, Akt, or NF-κB by inhibitors reversed the drug-resistance of RPMI8226/VCR cells via the suppression of survivin expression, but did not affect MDR1 expression; RNA silencing of survivin expression completely reversed vincristine resistance, while MDR1 silencing only weakly suppressed vincristine resistance in RPMI8226/VCR cells. These results indicate that enhanced survivin expression via the activation of ERK1/2, Akt, and NF-κB plays a critical role in vincristine resistance in RPMI8226/VCR cells. Our findings suggest that ERK1/2, Akt, and NF-κB inhibitors are potentially useful as anti-MDR agents for the treatment of vincristine-resistant MM.