Key words ginsenoside Rh2; lung cancer; apoptosis; reactive oxygen species; endoplasmic reticulum stress Followed by serial biological steps including hyperplasia, metaplasia, dysplasia and in situ carcinoma, similar to other cancers, lung cancer eventually develops its malignancy marked by strong proliferative capacity which is characterized by resistance to apoptosis. 1) Nowadays, lung cancer is still among the top common cancers worldwide. According to the records, lung cancer composes 12.7% of cancer and 18.2% of cancer related death.2) Though the multiple therapies including surgery, radiotherapy and chemotherapy are more and more widely applied to patients, the prognosis of lung cancer is still poor due to its malignant nature. Non-small cell lung cancer (NSCLC) takes approximately 85% of lung cancer cases with less than 20% 5-year survival rate.3) Seeking and identifying new drugs inducing apoptosis may provide us new insight into prevention and treatment of lung cancer.As one of the vital organelles in eukaryotic cells, endoplasmic reticulum (ER) is responsible for directing correct protein folding, calcium homeostasis and lipid metabolism. 4) However, under certain physiological and pathological conditions, the normal functions of ER were impaired by multiple extra-or intra-cellular stimuli, which is referred as ER stress.5) Reactive oxygen species (ROS) is considered as one of the stimuli inducing ER stress. This phenotype is called ROS-mediated ER stress. 6) Many anticancer agents such as chemotherapeutic drugs are believed to induce apoptosis by generating excessive intracellular ROS which is related with unfolded protein response (UPR) in ER to induce ER stress. 7) Numerous investigations supposed that ROS-mediated ER stress could further promote cell apoptosis by activating CCAAT/enhancer binding protein (C/EBP) homologous protein CHOP signaling pathway.8) As a pre-apoptotic factor, CHOP is suggested to activate caspase cascade by inducing cleavage of caspase-12 (rodents) 9) or caspase-4 (human).
10)In recent decades, natural products gradually become new alternatives besides regular therapies. With a long history in traditional medicine in East Asia, ginseng (Panax quinquefolius) is now a very popular herb as medicine or food supplement in the world. 11) Extracted from roots of ginseng, ginsenosides are the main effective components.12) It was suggested in the previous study that among the ginsenosides, ginsenoside Rh2 (G-Rh2, first isolated by Shizuo Odashima 13) ) exhibited various biological and pharmacological activities including anti-inflammation, anti-diabetes and anti-cancer.
14-17)A recent report supposed that G-Rh2 induced colorectal cancer cell apoptosis by inducing excessive intracellular ROS generation.18) Thus, ROS-mediated ER-stress induced apoptosis attracted our attention in investigating gensenoside Rh2's mechanism of anti-proliferation.In this present study, we showed G-Rh2 inhibited proliferation of lung cancer cells by inducing apoptosis. Furthermore, whether ROS-mediated ER-s...