Ginsenoside Rh2 (G-Rh2), a component extracted from roots of ginseng, exhibited anti-cancer pharmacological activities by inhibiting proliferation and inducing apoptosis in lung cancer cells. However, the mechanisms of G-Rh2 suppressing lung cancer development remained elusive. This study tried to investigate the possible mechanism involved in anti-proliferative effect of G-Rh2 in lung cancer cells. As results, G-Rh2 inhibited the proliferation of H1299 cells in a dose-dependent manner by inducing cell apoptosis. Activating transcription factor 4 (ATF4), CCAAT/enhancer-binding protein homologous protein (CHOP), and caspase-4 were involved in G-Rh2-induced apoptosis of H1299 cells. It was also found that G-Rh2 could up-regulate expressions of ATF4, CHOP and caspase-4 in H1299 cells in a dose-dependent manner. In addition, NAC (N-acetylcysteine, a reactive oxygen species (ROS) scavenger) treatment dramatically decreased ROS generation in H1299 cells; both of NAC and 4-PBA (4-phenylbutyrate, a specific endoplasmic reticulum (ER) stress inhibitor) administration impaired apoptosis and expression levels of ATF4, CHOP and caspase-4 in G-Rh2 incubated H1299 cells. In vivo assays extended the significance of these results, showing that G-Rh2 inhibited lung cancer growth and the inhibition effects of G-Rh2 in tumor growth were significantly reduced by inhibition of ER stress. In conclusion, G-Rh2 inhibited proliferation of H1299 cells by inducing ROS mediated ER stress dependent cell apoptosis.
Keywords: apoptosis; endoplasmic reticulum stress; ginsenoside Rh2; lung cancer; reactive oxygen species.