Ginkgolic acids (C15 and C17) induce autophagy and apoptosis in gastric carcinoma HGC cells by inducing ER stress

Objective: This paper show that Ginkgolic acids can induce cell death in gastric cancer cell line HGC via a combination of autophagy and apoptosis pathway.Methods: The survival curves of the GAs (C15, C17) of the HGC were measured by MTT assay, and the expression of apoptosis associated proteins caspase-3, 8, 9 and the autophagy-associated protein 5, beclin 1 and microtubule-associated protein 1A/1B-light chain 3 in the GA-treated HGC cells were all measured by western blot analysis.The terminal deoxynucleotidyl-transferase-mediated dUTP nick-end labeling (TUNEL) assay was used to monitor the level of apoptosis in the GA-treated cells, and Transmission Electron Microscopy (TEM) was used to monitor the level of autophagy in the GA-treated cells.Results: MTT assays showed that both C15 and C17 inhibited HGC cell proliferation in a time-dependent and dose-dependent manner, and WB showed that the ER stress-, autophagy-, and apoptosis-related proteins were all increased.TUNEL, and TEM analysis show that the GAs induced both apoptosis and autophagy in the HGC cells.After CHOP expression was knocked down by small interfering RNA (siRNA), both C15 and C17 ginkgolic acid-treated cells showed increased ER stress-related protein expression, moreover, the LC3-II conversion and beclin-1 expression were reduced.After inhibition of ER stress by 4-PBA, both autophagy-related protein and apoptosis-related protein expression was decreased.After treatment with the autophagy inhibitor 3MA, both ER stress-related protein and apoptosis-related protein expression was decreased.After treatment with the c-Jun N-terminal kinase (JNK) pathway downregulator SP600125, the expression of beclin-1 and LC3-II conversion were reduced.Conclusions: The results suggest that both C15 and C17 ginkgolic acids increased ER stress upstream to regulate autophagy and apoptosis by three branch pathways (ATF6, inositol-requiring enzyme 1 (IRE1), and PKR-like ER protein kinase (PERK)).The IRE1-JNK pathway plays an important role in the crosstalk between ER stress and autophagy.