E-cadherin and β-catenin adhesion proteins correlate positively with connexins in colorectal cancer

The majority of solid cancers present with qualitative and quantitative aberrations of adhesion proteins, including E-cadherin and beta-catenin, and connexin (Cx) gap junction proteins, which is consistent with alterations in the expression and location of such proteins in neoplastic cells. Since there are no data on the correlation between adhesion proteins and Cxs in human colorectal cancer (CRC), the aim of the present study was to evaluate the expression and correlation between these proteins. Tissue specimens were obtained from 151 cases of surgically removed colorectal adenocarcinomas. The samples were examined by immunohistochemistry with the use of antibodies against E-cadherin, beta-catenin and the three Cxs: Cx26, Cx32 and Cx43. The aberrant expression of the studied adhesion proteins (primarily cytoplasmic for E-cadherin and cytoplasmic and/or nuclear for beta-catenin) was observed, whereas only a minority of cases revealed normal membranous distribution of the labeling. The present study is the first in the literature to reveal a correlation between the expression of E-cadherin and beta-catenin and the examined Cxs in CRC in humans. The positive correlation between the Cxs, particularly Cx26 and Cx32, and the adhesive proteins occurred in patients without lymph node metastases and in the moderately differentiated tumors (G2). Such a dependency was not observed in the analysis of the correlation between Cx43 and E-cadherin. However, a positive correlation between these proteins was observed in patients with lymph nodes metastases. Additionally, a link between the expression of these adhesion proteins was observed. The present study indicates, for the first time, that the expression of adhesion proteins, E-cadherin and beta-catenin, is closely associated with the expression of three studied Cxs in CRC, and that this correlation may improve an understanding of the carcinogenic process in this cancer.