Neural cell adhesion molecule (NCAM) mediates colon cancer cell clumping

Loss of intercellular adhesion precedes metastatic behavior in carcinomas. NCAM is an important intercellular adhesion molecule that is absent in aggressive colon carcinomas (Gastroenterology 108:A529, 1995). The purpose of the present study was to prove that NCAM is capable of mediating colon cancer intercellular cell adhesion. Methods: Eight colon cancer cell lines obtained from the ATCC were screened by immunohistochemistry and RT-PCR for the presence on NCAM cell surface protein or mRNA expression respectively. Cells were grown in graded doses of anti-NCAM monoclonal antibody (Zymed), with an IgG control or in media alone. A blinded observer counted the number of cell clumps and total number of cells. Data are reported as the percent of cells growing in clumps. Results: One of the 8 cell lines tested expressed mRNA as well as NCAM protein as determined by RT-PCR and immunohistochemistry. Cells lacking NCAM demonstrated little clumping with 4.3 ± .6 % (SEM) of cells in clumps. The cell line with NCAM had significantly greater clumping 21.6 ± .8 % of cells (p<.05, t-test). The figure on the left demonstrates the effect of anti-NCAM on colon cancer cell clumping in this cell line. The x-axis represents log-order anti-NCAM dilutions from 1:10̂6 on the left to 1:1 on the for right. The y-axis is the percent of cells found in clumps. Control cultures are represented by the open boxes and those grown in the presence of serial dilutions of anti-NCAM antibody are shown with closed boxes. There was a dose-dependent reduction in cell clumping with increasing concentrations of anti-NCAM antibody (p<.05, ANOVA with contrasts). Conclusions: NCAM expression occurs in some colon cancer cell lines and results in a tendency for the cells to clump together. The clumping behavior was reversed by anti-NCAM antibody in the media. These data suggest that NCAM mediates cell-cell adhesion in colon cancer and supports our hypothesis that loss of this molecule enables cells to break away and metastasize.