Claudin-1 expression confers resistance to anoikis in colon cancer cells in a Src-dependent manner

Denial of the appropriate cell-matrix interaction in epithelial cells induces apoptosis and is called 'anoikis'. Cancer cells are resistant to anoikis and it is believed that the resistance to anoikis helps promote tumor malignancy especially metastasis. We and others have demonstrated that the expression of tight junction protein claudin-1 is highly upregulated in colorectal cancer (CRC) and helps promote tumor progression and metastasis. However, molecular mechanism/s underlying claudin-1-dependent regulation of CRC progression remains poorly understood. In current study, we have determined that claudin-1 expression modulates anoikis in colon cancer cells to influence colon cancer invasion and thus metastasis. We have further provided data that claudin-1 modulates anoikis in a Src-Akt-Bcl-2-dependent manner. Importantly, claudin-1 physically associates with Src/p-Src in a multiprotein complex that also includes ZO-1, a PDZ-binding tight junction protein. Taken together, our data support the role of claudin-1 in the regulation of CRC progression and suggest that the regulation of anoikis may serve as a key regulatory mechanism in claudin-1-dependent regulation of CRC progression. Our findings are of direct clinical relevance and may open new therapeutic opportunity in colon cancer treatment and/or management.