Dihydromethysticin kavalactone induces apoptosis in osteosarcoma cells through modulation of PI3K/Akt pathway, disruption of mitochondrial membrane potential and inducing cell cycle arrest.

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.