Abstract
Baicalein, a flavone present in Scutellaria baicalensis Georgi, has been demonstrated to possess antitumor activity in a variety of cancer cells in vitro. However, its effects on the growth inhibition and induction of apoptosis in human esophageal carcinoma cells remain unclear. The aims of this study were to determine whether cultured EC-109 esophageal squamous cell carcinoma (ESCC) cells undergo apoptosis when treated with baicalein and to investigate the underlying mechanisms in vitro. Cell growth was measured using MTT and plate colony formation assays. Induction of apoptosis was examined using Hoechst 33258 staining, flow cytometry analysis and a DNA fragmentation assay. The mechanisms underlying the observed growth suppression were examined using western blot analysis. The results demonstrated that treatment of EC-109 cells with baicalein for 48 h markedly decreased the rate of cell viability. Colony formation was almost fully suppressed at 40 μM baicalein. EC-109 cells underwent apoptosis in response to baicalein treatment, demonstrated by an increase in the percentage of cells stainable with Hoechst 33258 and Annexin V-FITC/PI, increased DNA fragmentation and activation of the intrinsic (mitochondrial) pathway for cell death. The latter was characterized by increased expression of the cleaved forms of caspase-9 and -3, and poly (ADP-ribose) polymerase (PARP). Additionally, baicalein was found to downregulate anti-apoptotic components and upregulate apoptotic components of the PI3K/Akt pathway. In conclusion, baicalein induces apoptosis in EC-109 cells through modulation of the PI3K/Akt pathway, thus providing further understanding of the molecular mechanisms of baicalein action in esophageal carcinoma. Therefore, the present study revealed that baicalein significantly inhibits growth and induces apoptosis in EC-109 human ESCC cells in vitro.