Natural Bcl-2 inhibitor (-)-gossypol induces protective autophagy via reactive oxygen species-high mobility group box 1 pathway in Burkitt lymphoma

(-)-Gossypol, a natural inhibitor of anti-apoptotic Bcl-2 proteins, has presented an effective anti-tumor activity in numerous preclinical trials. More and more evidence in vivo and in vitro validates that (-)-gossypol can dramatically suppress cell proliferation and induce cell death in hematological malignancies. However, the detailed mechanisms are not well known. In the present study, we showed that treatment with (-) -gossypol stimulated reactive oxygen species (ROS) generation and induced autophagy in Burkitt lymphoma cells. Antioxidant N-acetyl-cysteine (NAC) pretreatment attenuated (-)-gossypol-induced autophagy. Furthermore, (-)-gossypol treatment increased the translocation of high mobility group box 1 (HMGB1) from nuclei to cytoplasm, which can be suppressed by NAC pretreatment. NAC pretreatment also dramatically enhanced (-)-gossypol-induced apoptosis and total cell death. These results indicate that (-)-gossypol induces a protective autophagy in Burkitt lymphoma cells, partly due to ROS induction and cytosolic translocation of HMGB1. Antioxidants may serve as potent chemosensitizers to enhance cell death through blocking (-)-gossypol-induced autophagy.