Ganoderma lucidum inhibits proliferation of human ovarian cancer cells by suppressing VEGF expression and up-regulating the expression of connexin 43

BACKGROUND Ganoderma lucidum (G. lucidum, Reishimax) is an herbal mushroom known to have inhibitory effect on tumor cell growth. However, the molecular mechanisms responsible for its anti-proliferative effects on the ovarian cancer have not been fully elucidated. METHODS Human ovarian cancer cells HO 8910 (HOCC) and human primary ovarian cells (HPOC) were treated with G. lucidum. Effects of G. lucidum treatment on cell proliferation were studied by MTT assay. The expression of vascular endothelial growth factor (VEGF) and connexin 43 (Cx43) were measured by immunohistochemistry and real time polymerase chain reaction. To study the molecular mechanism of CX43 mediated anti-tumor activity, small interference RNA (siRNA) was used to knockdown Cx43 expression in HOCC. RESULTS G. lucidum treatment resulted in reduced proliferation of HOCC. Inhibition of proliferation was accompanied by a decrease in VEGF expression and increase in Cx43 expression in the cancer cells. The extent of immune-reactivity of Cx43 or VEGF in cancer cells were correlated with the concentrations of G. lucidum used for treatment. Furthermore, knockdown of Cx43 expression in HOCC abrogated the effect of G. lucidum on cell proliferation without alteration of G. lucidum-induced attenuation of VEGF expression. CONCLUSIONS G. lucidum inhibits ovarian cancer by down-regulating the expression of VEGF and up-regulating the downstream Cx43 expression. G. lucidum may be a promising therapeutic agent for the treatment of ovarian cancer.