Harmine Hydrochloride Triggers G2/M Cell Cycle Arrest and Apoptosis in HCT116 Cells through ERK and PI3K/AKT/mTOR Signaling Pathways

Colorectal carcinoma (CRC) is one of the most common and aggressive malignant carcinomas. There is a pressing need to develop naturally derived novel drugs with minimal side effects for treatment of CRC. In this study, we aimed to investigate the anticancer effects of harmine hydrochloride (HMH), a hydrophilic and stable substance that is easily absorbed by tissues and similar to harmine, and the underlying mechanism of action in human CRC HCT116 cells. HMH inhibited the growth, colony formation, and migration ability of HCT116 cells. Additionally, HMH induced G2 cell cycle arrest by reducing expression of p-cdc2, cdc2, and cyclin B1, proteins that regulate the G2/M phase, and expression of Rb, a protein that regulates cell proliferation, in a dose-dependent manner. HMH mediated apoptosis by downregulating expression of apoptotic proteins (such as caspase-3, caspase-9, and PARP) and the anti-apoptotic protein Bcl-2 and by inducing expression of Bax, a pro-apoptotic protein. Furthermore, HMH reduced the levels of p-ERK, p-PI3K, p-AKT, and p-mTOR in HCT116 cells, and significantly inhibited p-ERK and p-AKT expression in cells treated with of HMH and PD98059, an ERK inhibitor, or LY294002, an AKT inhibitor (P<0.05 and P<0.01). These results demonstrate the inhibi-tory effect of HMH on cell proliferation and migration through inducing apoptosis by inhibiting ERK and PI3K/AKT/mTOR signaling pathways, indicating its potential therapeutic applications in CRC.