Gallic acid from Terminalia chebula inhibited the growth of esophageal carcinoma cells by suppressing the Hippo signal pathway

To explore the molecular mechanism of gallic acid (GA) from Terminalia chebula in suppressing the growth of esophageal carcinoma (EC). Human EC cells (EC9706 and KYSE450) were treated with different concentrations of GA (10, 20, and 40 μg/ml), which were subjected to 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) assay, plate clone formation assay, Annexin V-fluorescein isothiocyanate (FITC)/propidium iodide (PI) staining, and Western blotting. EC mice were divided into Model, 0.3% GA, and 1% GA groups to observe the tumor volume and the expressions of YAP, TAZ, Ki-67, and Caspase-3 in tumor tissues. GA decreased cell viability and colony formation of EC9706 and KYSE450 cells, which was more obvious as the concentration increased. In addition, GA promoted cell apoptosis in a concentration-dependent manner with the up-regulation of pro-apoptotic proteins (Bax, cleaved caspase-3, and cleaved caspase-9) and nuclear YAP/TAZ, as well as the down-regulation of anti-apoptotic protein Bcl-2 and the levels of p-YAP and p-TAZ. Moreover, GA decreased the growth of xenograft tumor in vivo, with the reduction in the tumor volume and the reduction of YAP and TAZ expressions in the tumor tissues. In addition, Ki-67 expression in GA groups was lower than those in the Model group, with the increase in caspase-3 expression in the tumor tissues. Changes aforementioned were obviously shown in the 0.3% GA group. GA blocked the activity of the Hippo pathway to suppress cell proliferation of EC and facilitate cell apoptosis, which is expected to be a novel strategy for treatment of EC.