Background:Recently,studies have shown that piperlongumine( PL)selectively killed cancer cells by elevating reactive oxygen species(ROS)in various cancers. However,the effect of PL on gastric cancer cells remained to be further studied. Aims:To investigate the effect of PL on proliferation and apoptosis of human gastric cancer cell line MKN45 and its underlying mechanism. Methods:MKN45 cells were treated with different doses of PL,caspase inhibitor,antioxidant, and their combinations,respectively. Cell viability was assessed by CCK-8 assay;cell cycle,apoptosis and intracellular ROS level were measured by flow cytometry;and Western blotting was employed to determine the expression of apoptosis-related proteins( XIAP,cleaved-caspase3,7,9 and cleaved-PARP),p53 and its downstream target genes( p21, GADD45α and PUMA). Results:PL inhibited the proliferation of MKN45 cells in a dose- and time-dependent manner. In MKN45 cells treated with PL,the proportion of cells in G1 phase,apoptotic rate and intracellular ROS level were significantly increased,the expression of inhibitor of apoptosis protein XIAP was down-regulated,and the caspase-dependent apoptosis pathway,p53 and its downstream target genes were activated. Pretreatment with antioxidant NAC or Z-VAD-FMK, a general caspase inhibitor could partially abolish the effect of PL on ROS production and its antitumor effect. Conclusions:PL can inhibit cell proliferation and induce cell cycle G1 phase arrest and apoptosis in MKN45 cells. Its antitumor effect may be associated with a ROS-mediated p53 activation and subsequent triggering of caspases cascade of cell apoptosis.

Background: Piperlongumine (PL) is an alkaloid compound extracted from piperlongum. Many studies have shown that PL has anti-tumor effects on a variety of tumor cells in vivo and in vitro. However, the specific mechanism needs to be further explored. Aims: To investigate the regulatory mechanism of PL on the expression of TERT in gastric cancer cells. Methods: Gastric cancer cells were treated with different doses of PL, AG490, respectively. CCK-8 and plate colony formation experiment were used to detect cell viability. Real-time fluorescent quantitative PCR was used to detect the expression of TERT mRNA. Western blotting was used to detect the protein expressions of TERT, STAT3, p-STAT3 and DNMT1. TRAP-ELISA was used to determine the telomerase activity. Luciferase reporter gene was used to detect the TERT promoter activity. Results: Compared with control group, gastric cancer cells viability in PL group was significantly decreased, colony formation ability was significantly reduced, TERT mRNA and protein expressions, as well as telomerase activity were significantly reduced, p-STAT3 and DNMT1 protein expressions were significantly downregulated. AG490 significantly inhibited gastric cancer cells viability, protein expressions of p-STAT3, DNMT1 and TERT. Conclusions: PL may inhibit gastric cancer cells viability through regulation of TERT expression via STAT3-mediated epigenetic regulation and it may become a new target drug for the treatment of gastric cancer in future.