Methanol extracts of Humulus japonicus induced apoptosis in human FaDu hypopharynx squamous carcinoma cells

Humulus japonicus (HJ) is a widely used herbal medicine for pulmonary tuberculosis, hypertension, leprosy, and venomous wounds in Asia, particularly in China. Although HJ has certain physiological activities, such as longitudinal bone growth, antioxidation and alleviation of rheumatism, its anticancer activities, other than in colorectal and ovarian cancer, are yet to be studied. In this study, we investigated the anti-cancer activity and mechanism of methanol extracts of HJ (MeHJ) against human FaDu hypopharyngeal squamous carcinoma cells. MeHJ suppressed FaDu cell viability without affecting normal cells (L929), which was demonstrated using the MTT and Live & Dead assays. Furthermore, MeHJ effectively inhibited colony formation of FaDu cells, even at non-cytotoxic concentrations, and significantly induced apoptosis through the proteolytic cleavage of caspase-9, -3, -7, poly (ADP-ribose) polymerase and through the downregulation of BCL-2 and upregulation of BAX in FaDu cells, as determined by DAPI staining, flow cytometry, and western blot analyses. Collectively, these findings suggest that the inhibitory effects of MeHJ on the growth and colony formation of oral cancer cells may be mediated by caspase- and mitochondrial-dependent apoptotic pathways in human FaDu hypopharyngeal squamous carcinoma cells. Therefore, MeHJ has the potential to be used as a natural chemotherapeutic drug against human oral cancer.