Mutated epithelial cadherin is associated with increased tumorigenicity and loss of adhesion and of responsiveness to the motogenic trefoil factor 2 in colon carcinoma cells

Epithelial (E)-cadherin and its associated cytoplasmic proteins (alpha-, be ta-, and gamma-catenins) are important mediators of epithelial cell-cell ad hesion and intracellular signaling. Much evidence exists suggesting a tumor /invasion suppressor role for E-cadherin, and loss of expression, as well a s mutations, has been described in a number of epithelial cancers. To inves tigate whether E-cadherin gene (CDH1) mutations occur in colorectal cancer, we screened 49 human colon carcinoma cell lines from 43 patients by single -strand conformation poly-morphism (SSCP) analysis and direct sequencing. I n addition to silent changes, poly morphisms, and intronic variants in a nu mber of the cell lines, we detected frameshift single-base deletions in rep eat regions of exon 3 (codons 120 and 126) causing premature truncations at codon 216 in four replication-error-positive (RER+) cell Lines (LS174T, HC T116, GP2d, and GP5d) derived from 3 patients. In LS174T such a mutation in evitably contributes to its lack of E-cadherin protein expression and funct ion. Transfection of full-length E-cadherin cDNA into LS174T cells enhanced intercellular adhesion, induced differentiation, retarded proliferation, i nhibited tumorigenicity, and restored responsiveness to the migratory effec ts induced by the motogenic trefoil factor 2 (human spasmolytic polypeptide ). These results indicate that, although inactivating E-cadherin mutations occur relatively infrequently in colorectal cancer cell lines overall (3/43 = 7%), they are more common in cells with an RER+ phenotype (3/10 = 30%) a nd may contribute to the dysfunction of the E-cadherin-catenin-mediated adh esion/signaling system commonly seen in these tumors. These results also in dicate that normal E-cadherin-mediated cell adhesion can restore the abilit y of colonic tumor cells to respond to trefoil factor 2.