Plumbagin reduces chronic lymphocytic leukemia cell survival by downregulation of Bcl-2 but upregulation of the Bax protein level

Chronic lymphocytic leukemia (CLL) is the most common leukemia in Western countries, and mainly originates from an accumulation of abnormal B cells caused by the dysregulation of cell proliferation and apoptosis rates. The aberration of apoptosis-related genes in CLL cells results in defective apoptosis of CLL cells in response to traditional therapeutic medicine. Plumbagin (5-hydroxy-2-methyl-1, 4-naphthoquinone), a natural compound from Plumbago zeylinica, has been shown to exhibit pro-apoptotic activities in tumor cells. In the present study, we report that plumbagin effectively inhibited CLL cell viability with a lower dose compared to fludarabine, and inhibited cell proliferation in a dose-dependent manner. In addition, plumbagin promoted accumulation of MEC-1 cells in the S phase, and blocked cell cycle transition of HG3 cells from G0/G1 to S phase. Molecularly, plumbagin markedly induced CLL cell apoptosis through reduction of Bcl-2, but through an increase in the Bax protein level. These results suggest that plumbagin may be considered as a potential anticancer agent for CLL therapy.