Low Doses of the Anti-psychotic Drug Aripiprazole Have Strong P-gp-inhibitory Activity and Sensitize Anti-mitotic Drug-resistant Cancer Cells.

OBJECTIVE

The present study was designed to identify conditions that would increase the sensitivity of resistant cancer cells to anti-mitotic drugs.

METHODS

Previously, we showed that KBV20C cancer cells highly resistant to Halaven® (HAL) were sensitized by co-treatment with fluphenazine (FLU). In this study, we found that low doses of aripiprazole (ARI), another antipsychotic drug, sensitized HAL-resistant KBV20C cancer cells. We then investigated the mechanisms and roles of ARI in the sensitization of HAL-treated KBV20C cancer cells.

RESULTS

First-generation P-glycoprotein (P-gp) inhibitor verapamil required a dose that was nearly four-fold higher than that of ARI for P-gp inhibition, which suggested that ARI had a high specificity for P-gp binding to prevent efflux of anti-mitotic drugs. ARI was also found to sensitize HAL-treated KBV20C cells at a low dose, approximately 4-fold lower than that of verapamil. Co-treatment of ARI with another anti-mitotic drug, vincristine, also increased the sensitization of KBV20C cells. ARI caused a reduction in cell viability, increased G2 arrest, and up-regulated expression of the DNA damage protein, pH2AX, when co-treated with HAL. Moreover, G2 phase arrest and apoptosis in HAL-ARI co-treated cells resulted from the up-regulation of retinoblastoma protein, reduced extracellular signal-regulated kinase pathway activity, and down-regulation of cell division cyclin protein.

CONCLUSIONS

Cancer cells that are highly resistant to HAL can be sensitized with the antipsychotic drug, ARI, which exerts specific P-gp inhibitory effects at a low dose.