RESUMEN
Oleanolic acid (OA) possesses various pharmacological activities, such as antitumor and anti-inflammation; however, its clinical applications are limited by its relatively weak activities and low bioavailability. In this study, we evaluated the cytotoxic activity of seven novel OA derivatives, one of which, SZC014 [2-(pyrrolidine-1-yl) methyl-3-oxo-olean-12-en-28-oic acid], exhibited the strongest antitumor activity; its anticancer effect on gastric cancer cells and action mechanisms were investigated. The viability of OA and seven synthesized derivatives treating gastric cancer cells was detected using tetrazolium (MTT). Among them, SZC014 exhibited the strongest cytotoxic activity against gastric cancer cells (SGC7901, MGC803, and MKN-45). The effect of SZC014 on cell cycle was identified by propidium iodide (PI) staining assay. The cellular apoptosis induced by SZC014 was tested by annexin V/PI. The cellular morphological changes and ultrastructural structures affected by SZC014 were observed and imaged through inverted phase contrast microscope and transmission electron microscopy. Western blotting was performed to explore the expression of proteins associated with apoptosis (caspase 3, caspase 9, Bax, Bcl-2, and Bcl-xL), autophagy (Beclin 1 and ATG 5), and nuclear factor-κB (NF-κB) signal pathway, respectively. The cytotoxic activities of all the seven synthesized OA derivatives were stronger than that of OA against gastric cancer cells. SZC014 exhibited stronger cytotoxic activity than other OA derivatives, inhibited the proliferation of gastric cancer cells, besides, induced G2/M phase cell cycle arrest in SGC7901 cells. Both apoptosis and autophagy were found simultaneously in SZC014-treated SGC7901 cells. Caspase-dependent apoptosis induced by SZC014 was confirmed to be associated with upregulation of Bax and downregulation of Bcl-2 and Bcl-xL, while upregulation of Beclin 1 and ATG 5 was inferred to be involved in SZC014-induced autophagy. Moreover, treating cells with SZC014 resulted in a decrease in phosphorylation of IκBα and NF-κB/p65 and NF-κB/p65 nuclear translocation. The cytotoxic activities of seven OA derivatives were generally stronger than that of OA, among which, SZC014 possessed the most potent anticancer activity in SGC7901 cells and would be a promising chemotherapic agent for the treatment of gastric cancer.