The objective of the present study was to evaluate the tumor and apoptotic effects of dihydromethysticin kavalactone against human osteosarcoma (MG-63) cells. Antiproliferative activity was measured with the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Apoptosis induction by dihydromethysticin was demonstrated by fluorescence microscopy, quantitative videomicroscopy and Annexin V-FITC apoptosis detection kit. Mitochondrial membrane potential disruption was demonstrated by rhodamine-123 dye using flow cytometry. We also evaluated the effect of dihydromethysticin on PI3K/Akt pathway with an immunoblotting analysis. The results showed that the compound induced dose-dependent as well as time-dependent antiproliferative effects against MG-63 cell growth. Cell death and apoptotic body formation was noticed followed dihydromethysticin treatment at various doses. The percentage of apoptotic cells (early apoptosis+late apoptosis) increased from 6.63% in untreated control to 23.92%, 23.81% and 93.9% in 25 µM, 75 µM and 100 µ Mdihydromethysticin-treated cells respectively. Flow cytometric analysis showed dihydromethysticin induced an increase in G0/G1 cells (apoptotic cells). Furthermore, we observed mitochondrial transmembrane depolarization along with decreased phosphorylation levels for PI3K, AKT (Ser 473), AKT (Thr 308), GSK-3β, and BAD. These reductions were associated with down regulation of AKT and upregulation of both GSK-3β and BAD.
Keywords: Osteosarcoma; anticancer effect; apoptosis; dihydromethysticin; flow cytometric.