Harmine Hydrochloride Triggers G2 Phase Arrest and Apoptosis in MGC-803 Cells and SMMC-7721 Cells by Upregulating p21, Activating Caspase-8/Bid, and Downregulating ERK/Bad Pathway.

This study aimed to investigate the effects of harmine hydrochloride (HMH) on digestive tumor cells in vitro and its molecular mechanism. MTT assays showed that HMH inhibited the proliferation of some human cancer cell lines and had no obvious inhibitory effects on human LO2 cells. Flow cytometry assays showed that HMH trigged G2 phase arrest in MGC-803 cells and SMMC-7721 cells, while the expression of cyclin A, cyclin B, p21, Myt1, and p-cdc2 (Tyr15) was upregulated. Flow cytometry assays also showed that the percentages of apoptotic cells were increased, the mitochondrial transmembrane potential (ΔΨm) decreased, and the cleavage of caspase-9, caspase-3, and poly (Adenosine diphosphate ribose) polymerase (PARP) were observed, the expression of Bad increased, phospho-Bad (S112) decreased, pro-caspase-8 was cleaved, and Bid (22 kDa) was cleaved. The expression of p-ERK decreased in both cells. In conclusion, these results demonstrated that HMH upregulates the expression of p21, activates Myt1 and inhibits cdc2 by phospho-cdc2 (Y15), and triggers G2 phase arrest in both MGC-803 cells and SMMC-7721 cells. It can also activate the mitochondria-related cell apoptosis pathway through the caspase-8/Bid pathway, inhibiting the ERK/Bad pathway and promoting apoptosis in both of these two cell types.