Cytoplasmic beta-catenin in esophageal cancers

beta-catenin has 2 distinct roles in E-cadherin-mediated cell adhesion and carcinogenesis through APC gene mutation. One occurs at cell-adhesion sites , where cadherins become linked to the actin based cytoskeleton. The others occur in the cytoplasm and nuclei and are thought to regulate cell transfo rmation. We studied these different beta-catenins and evaluated their signi ficance in carcinogenesis, Fresh surgical specimens were obtained from 22 p atients with squamous cell carcinoma of the esophagus, beta-Catenin in the free soluble fraction and the insoluble fraction was immunoblotted separate ly. At the same time, its localization was observed by immuno-histochemical techniques. In the normal esophageal epithelium, 91% of beta-catenin was d etected in the insoluble fraction and beta-catenin staining occurred at the cell membrane, in co-existence with E-cadherin, In cancerous tissues, the amount of soluble beta-catenin was significantly (about 4-fold) higher than in normal tissues. Also, in cancerous tissues with higher amounts of solub le beta-catenin, immunohistochemical techniques revealed the presence of be ta-catenin in the cytoplasm and nuclei, as well as in the cell membrane. Ho wever, in samples with lower amounts of beta-catenin, expression was found only at the cell boundaries. The amount of soluble beta-catenin was not ass ociated with the clinicopathological grading of the tumors. Our results sho w that the accumulation of free soluble beta-catenin in the cytoplasm and n uclei frequently occurs during carcinogenesis of the squamous epithelium of the esophagus. Int. J. Cancer (Pred. Oncol.)84:174-178, 1999. (C) 1999 Wil ey-Liss, Inc.