β -Lapachone,a Quinone Isolated from Tabebuia avellanedae,Induces Apoptosis in HepG2 Hepatoma Cell Line Through Induction of Bax and Activation of Caspase

The DNA topoisomerase inhibitor β-lapachone is a quinone obtained from the bark of the lapacho tree (Tabebuia avellanedae) in South America. It has been reported to possess a wide range of pharmacological properties, and is a promising cancer chemopreventive agent. In this study, the effects of β-lapachone on the growth of the human hepatoma cell line HepG2 were investigated. The results showed that β-lapachone inhibits the viability of HepG2 by inducing apoptosis, as evidenced by the formation of apoptotic bodies and DNA fragmentation. Reverse transcription-polymerase chain reaction and immunoblotting results indicated that treatments of cells with β-lapachone resulted in down-regulation of anti-apoptotic Bcl-2 and Bcl-X_L and up-regulation of pro-apoptotic Bax expression. β-Lapachone-induced apoptosis was associated with a proteolytic activation of caspase-3 and -9 and degradation of poly(ADP-ribose) polymerase protein. However, β-lapachone treatment did not affect the inhibitor of apoptosis proteins family and the Fas/FasL system. Taken together, our study indicated that β-lapachone may have potential as a chemopreventive agent for liver cancer.