Procyanidin B2 induces apoptosis and autophagy in gastric cancer cells by inhibiting Akt/mTOR signaling pathway

Background Procyanidin B2 (PB2), a unique component of the grape seed and other medicinal plants. PB2 has shown wide anticancer activity in various human cancer cells. However, it remains unclear about the biological effects and associated mechanisms of PB2 on gastric cancer cells. Methods Cell proliferation was measured by CCK8 assay, and cellular lactate dehydrogenase (LDH) release was measured in the culture medium. Cellular apoptosis was observed via TUNEL staining assay and measured by caspase-3 and -9 activities. Autophagy was observed by LC3 staining. Western blot analysis was performed to verify autophagy-associated proteins (Beclin1 and Atg5) and Akt-mTOR pathway. Results PB2 reduced the viability of BGC-823 and SGC-7901 cells in a concentration-dependent manner. Furthermore, PB2 induced increased apoptosis rate of gastric cancer cells and enhanced caspase-3 and -9 activities. Simultaneously, PB2 triggered autophagy in gastric cancer cells, with enhanced LC3 staining and increased expression of Beclin1 and Atg5, while the inhibition of autophagy by 3-MA reversed the PB2-induced suppression on cell viability. In addition, PB2 significantly decreased p-Akt and p-mTOR protein expression of gastric cancer cells. Conclusion PB2 exerts anti-proliferative and apoptotic effects and induces autophagy by modulating Akt/mTOR signaling pathway. PB2 may be developed as a potential therapeutic drug for gastric cancer.