Valproic Acid Enhances the Anti-tumor Effect of (-)-gossypol to Burkitt Lymphoma Namalwa Cells

Burkitt lymphoma is a highly aggressive B-cell neoplasm. New therapeutic methods are needed to overcome the adverse effect of intensive chemotherapy regimens. Valproic acid and (-)-gossypol are two kinds of chemical compounds used as new anti-tumor drugs in recent years. To investigate the anti-tumor effect of valproic acid and (-)-gossypol, Burkitt lymphoma Namalwa cells were cultured and treated with valproic acid and (-)-gossypol at different concentrations. The proliferation of Namalwa cells was dramatically suppressed after the combination treatment with 2 mmol/L valproic acid and 5 μmol/L (-)-gossypol. The combined treatment also enhanced intrinsic apoptosis by down-regulating anti-apoptotic protein Mcl-1. Moreover, the autophagy flux significantly increased in Namalwa cells after combined treatment. However, the enhanced autophagy showed little effect on cell survival with present regimen. The results confirmed that combination of valproic acid and (-)-gossypol had synergistic anti-tumor effect to Burkitt lymphoma Namalwa cells. The related mechanisms might include the down-regulation of anti-apoptotic protein Mcl-1 and avianized pro-survival role of autophagy.