Euphorbia lunulata extract acts on multidrug resistant gastric cancer cells to inhibit cell proliferation, migration and invasion, arrest cell cycle progression, and induce apoptosis

Ethnopharmacological relevance: The milky sap or the aboveground part of the plant Euphorbia lunulata has long been used by Chinese people to treat noncancerous growths and cancerous ailments but the specific mode of action and the action mechanism remain to be elucidated.

Aim of the study: To investigate the effects of Euphorbia lunulata extract on cell proliferation, migration, invasion, cell cycle progression, and Apoptosis of multidrug resistant human gastric Cancer cells; To study the mechanism of Apoptosis induction by Euphorbia lunulata extract in multidrug resistant human gastric Cancer cells.

Materials and methods: The aboveground part of fresh Euphorbia lunulata plant was extracted first with ethanol and then with n-hexane. The aseptic extract at varying concentrations was used to treat the multidrug resistant human gastric Cancer SGC7901/ADR cells. After treatment, the inhibition of cell proliferation was examined by MTT assay. The inhibitions of cell migration and invasion were detected by Transwell method. The alteration of cell cycle progression was studied by flow cytometry. The morphological changes of cell nuclei were observed with fluorescence microscopy following Hoechst 33258 staining and the apoptotic indexes were calculated. The activation of Caspase enzymes was analyzed by spectrophotometry. The sub-cellular distribution of cytochrome complex and the expression of Bax and Bcl-2 proteins were determined by Western blot.

Results: The proliferation, migration, and invasion of SGC7901/ADR cells were significantly inhibited by Euphorbia lunulata extract, which showed time- and dose-dependent manners. Cell cycle was arrested in G2/M phase. Significant apoptotic morphological changes were observed in the nuclei of the treated cells, and apoptotic indexes were increased significantly; these changes were diminished when Z-VAD-FMK, a Caspase Inhibitor, was also presented. The activities of Caspase-3, Caspase-8, and caspase-9 were increased. The sub-cellular distribution of cytochrome complex was altered----reduced in the mitochondria and increased in the cytoplasm. The expression of Bax was upregulated, while that of Bcl-2 was downregulated.

Conclusion: Euphorbia lunulata extract inhibited the proliferation, migration, and invasion of SGC7901/ADR cells, arrested cell cycle progression, and induced cell apoptosis; the mechanism of Apoptosis induction involved both the extrinsic and the intrinsic pathways.