Nectin is an immunoglobulin-like adhesion molecule that comprises a family consisting of four members, nectin-1, -2, -3, and -4. Nectin is associated with the actin cytoskeleton through afadin, a nectin- and actin filament-binding protein. The nectin-afadin and cadherin-catenin systems are associated with each other and cooperatively form cell-cell adherens junctions in intact epithelial cells. HSC-39 cells, a human signet ring cell gastric cancer cell line, express E-cadherin but do not form cell-cell adhesion. The beta-catenin gene has been shown to be truncated at the N-terminal region including the alpha-catenin-binding domain in HSC-39 cells, but overexpression of normal beta-catenin failed to form cell-cell adhesion. HSC-39 cells expressed nectin-1, -2, and afadin, but not nectin-3. Overexpression of nectin-3 or -2 formed cell-cell adhesion and accumulation of E-cadherin, but not actin filaments, at the cell-cell adhesion sites. Overexpression of a truncated form of nectin-2 incapable of interacting with afadin failed to form cell-cell adhesion. However, the nectin-formed cell-cell adhesion was not so strong as that observed in epithelial cells, such as CaCo-2 cells. Co-expression of nectin-2 and normal beta-catenin did not form strong cell-cell adhesion. These results suggest that an unidentified mechanism, by which nectin and E-cadherin form the actin cytoskeleton-associated adherens junctions to form strong cell-cell adhesion, is impaired in HSC-39 cells.