Apoptosis-inducing effect of 6,7-dimethoxy-4'-hydroxy-8- formylflavon from <i>Nicotiana tabacum</i> L leaf in human hepatoma HepG2 cells via activation of mitochondriamediated apoptotic pathway

Abstract

Purpose: To study the anti-proliferative and apoptotic influences of 6,7-dimethoxy-4'-hydroxy-8formylflavon (DHF) from the leaves of Nicotiana tabacum L. in human hepatoma HepG2 cells, and the underlying mechanisms. Methods: The anti-proliferative effect of DHF (10-50 μg/mL) on HepG2 cells was assessed by CCK-8 assay. The pro-apoptotic effect of DHF (10, 20 and 30 μg/mL) on HepG2 cells was investigated via flow cytometry, while the mechanisms involved were studied using western blot. Xenograft assay was employed for determination of the in vivo effect of DHF (40 mg/kg/day) on HepG2 cell-induced tumor. Results: The proliferation of HepG2 cells was inhibited by DHF (IC50 = 25.87 μg/mL) due to apoptosis. In addition, xenograft assay revealed that HepG2 cell-induced tumor growth was significantly suppressed by DHF (p < 0.05 or 0.01) without any effects on mice body weights. The expressions of Survivin and Bcl-2 proteins were significantly decreased, while those of Bax, c-caspase-9, and ccaspase-3 proteins were significantly increased by DHF (p < 0.05 or 0.01), leading to increase in cytoplasmic levels of Smac and cytochrome c proteins. Conclusion: The underlying mechanism DHF-mediated apoptotic changes in HepG2 cells in vitro and in vivo involves induction of the mitochondrial pathway of apoptosis. Thus, DHF is a good drug candidate for the development of an effective therapy for liver cancer.