Proliferation of esophageal cancer cells is promoted by hUCMSCs in vitro. (A) Esophageal cancer cells and hUCMSCs were performed directly contacting co-culture. Before co-cultured with esophageal cancer cells, hUCMSCs were treated with mitomycin C (20 μg/ml) to prevent cell proliferation. Then esophageal cancer cells were co-cultured with hUCMSCs for 48 hours. Separately cultured cancer cells and mitomycin-treated hUCMSCs were used as control. (B) Eca109 and TE-1 cells were co-cultured with hUCMSCs by using the transwell co-culture systems for 48 h, and then, cells were harvested for proliferation assays. The results are shown as mean ± SD of three independent experiments in comparison with that of controls not co-cultured with hUCMSCs (*P < 0.05 versus control).