Dihydroartemisinin Exhibits Antitumor Activity Toward Human Gastric Cancer Cells Through the Endoplasmic Reticulum Stress Pathway

Abstract

Background: Gastric cancer is the most fatal digestive tract tumor. The current treatment of gastric cancer often causes adverse effects. Dihydroartemisinin (DHA), a first-line antimalarial drug, is a derivative of a compound from a well-known Chinese medicinal plant Artemisia annua. DHA demonstrates antitumor activities toward many different types of cancer while exerts no apparent adverse effects on normal cells, making it a promising lead compound for cancer treatment. DHA induces apoptosis in Gastric cancer cell line 7901 (SGC-7901). However, the exact mechanism of this antitumor activity remains not fully explored. Methods: A CCK-8 assay to detect cell viability with DHA treatment in gastric cancer SGC-7901. The colony formation was visualized by crystal violet staining. The DHA-treatment cells were stained by Annexin-V FITC/PI dye and then subject to cell flow cytometry. The apoptosis was further observed in the Hoechst staining assay. Real-time qPCR was conducted to detect apoptosis-related markers. Western blotting was conducted to detect the protein levels of the endoplasmic reticulum (ER) stress pathway-related proteins. KIRA6, an ER stress pathway inhibitor was applied to find out whether it could reverse the cell death. Results: DHA induced dose-dependent apoptosis in Gastric SGC-7901 cell with an IC50 of about 4 mg/ mL. It significantly increased the proportion of apoptotic cells in a dose-dependent pattern in the Annexin V/PI flow cytometry. Significantly higher percentages of cells with a more prominently stained nucleus were observed in the Hoechst staining assay. In qPCR assay, the mRNA level of Bcl-2 was significantly decreased while that of Bax was significantly increased in a dose-dependent manner after DHA treatment. In the western blot assay, increased Bax and Bim and decreased Caspase 9, Bcl-2 were observed. Consistently, the levels of pro-apoptotic proteins were increased while those of anti-apoptotic ones were decreased as shown in the Human Apoptosis Array assay after DHA treatment. DHA stimulated the expression of GRP78, ATF4, IRE1, CHOP, and phosphorylated c-Jun (p-c-Jun) as revealed in western blotting. The cell death caused by DHA treatment was reversed by KIRA6. Conclusions: DHA exerts its antitumor activity on SGC-7901 cells through the IRE1/c-Jun ER stress pathway.