Apoptosis Was Induced by Casticin in Acute Myelocytic Leukemia Cells

Casticin, a component from Vitex rotundifolia wich was widely used as an anti-inflammatory agent in Chinese traditional medicine, was reported to have anti-tumor activities in lung cancer and breast cancer. There are yet no reports on roles against acute myelocytic leukemia (AML). This study aims to elucidate the anti-leukemic activity of casticin on AML cells. We investigated the efficient efficacy and the mechanisms by which casticin triggers cell death in AML cells by analyzing cell cycle perturbations, apoptosis-related marker expression. Cell viability was measured by MTT method; apoptosis and cell cycle arrest were determined by flow cytometry and AV-PI assay. Western blot was performed to measure the apoptosis-related marker. Concentration-dependant cell deaths were observed in AML cell lines including K562, U937 and THP-1, with IC50 values of 24h (hours) being 47.4μM, 67.8μM and 61.7μM, respectively. Time-dependant cell deaths were also observed. At the concentration of 20μM casticin, 45.7%, 76.1% and 80.9% of K562 cells were inhibited at 24h, 48h and 72h, respectively; 24.7%, 30% and 61% of U937 cells were inhibited at 24h, 48h and 72h, respectively; while for THP-1, 29%, 41.8% and 53.9% were inhibited at 24h, 48h and 72h, respectively. Apoptosis was found using AV-PI staining by flow cytometry analysis. We observed an obvious G2/M phase increase prolongation in casticin treated K562 cells. BThe distribitions of G2/M phase were 2.9%, 33.6%, 75.3%, 54.9%, 29.7% and 27.0% in K562 cells after treated by 20μM casticin for 0h, 6h, 12h, 24h, 36h and 48h, respectively. Furthermore, apoptosis-related proteins, PARP and caspase 3, were cleaved in casticin treated K562 cells. Taken together, these results demonstrated that casticin can induce leukemic cell death through apoptosis, suggesting that casticin could be a promising therapeutic agent against acute myeloid leukemia.