Alteration of beta-catenin expression in esophageal squamous-cell carcinoma

beta-catenin regulates cadherin-mediated cell-cell adhesion and also functi ons as a signaling molecule. In this study, we examined the expression patt ern of E-cadherin, alpha-catenin and beta-catenin in 22 cases of esophageal squamous-cell carcinoma by Western-blot analysis. Expression of E-cadherin , alpha-catenin and beta-catenin was lower in carcinomas than in normal eso phageal mucosa in 4 cases(18.2%) for E-cadherin, 6 cases (27.3%) for alpha- catenin and 9 cases (40.9%) for beta-catenin, Expression of beta-catenin wa s not always correlated with that of E-cadherin. Over-expression of beta-ca tenin was observed in 3 cases (13.6%). Of 3 cases that presented with over expression of beta-catenin, 2 showed cytoplasmic staining by immunohistoche mistry. Nuclear localization of beta-catenin was observed in one case that had higher beta-catenin level in tumor tissue (1.4-fold higher than normal mucosa). The genomic DNA sequences of the beta-catenin and the APC gene wer e analyzed. No mutation of the beta-catenin gene was observed in any cases. Silent mutation of the APC gene was found in all the cases that showed ove r-expression or nuclear localization of the beta-catenin protein, These res ults indicate that alterations of the cadherin-catenin complex may play an important role in a sub-set of esophageal carcinogenesis. Furthermore, it i s suggested that beta-catenin over expression is not caused by genetic alte ration of either the beta-catenin or the APC gene. (C) 2000 Wiley-Liss, Inc .