MUC4 and esophageal squamous cell carcinoma: We further validated the expression of MUC4, MUC13, MUC 20, and BMP7 at the mRNA level in the tumor tissues of 2 chemosensitive and 3 chemoresistant ESCC patients before chemotherapy; the results showed that MUC4, MUC20, and BMP7 were expressed at low levels, while MUC13 was over-expressed in the tumor tissues of patients who responded to chemotherapy.