Heterogeneous expression of claudin-4 in human colorectal cancer: decreased claudin-4 expression at the invasive front correlates cancer invasion and metastasis.

OBJECTIVE

Claudin-4 plays a key role in constructing the tight junction (TJ), and altered claudin-4 expression has been documented in various human malignancies; however, little is known about the biological significance of claudin-4 in colorectal cancers (CRCs). The aim of this study is to investigate the significance of claudin-4 expression in CRC and its association with clinicopathological factors.

METHODS

The levels of claudin-4 expression in a total of 129 CRCs and 44 metastatic tumors were examined by immunohistochemistry. A small interfering RNA (siRNA)-mediated claudin-4 knockdown examination was also conducted to assess the biological role(s) of claudin-4 in cultured cells.

RESULTS

Expression of claudin-4 at the intercellular membrane was well preserved at the surface of the tumor; however, decreased claudin-4 expression was detected in 57% of CRCs, particularly at the invasive front. Interestingly, decreased claudin-4 expression was detected in metastatic lesions of CRC. The siRNA-mediated claudin-4 knockdown in SW480 claudin-4-positive CRC cells upregulated cell motility, whereas no significant change was detected in cell proliferation.

CONCLUSIONS

These observations suggested that disruption of claudin-4-mediated TJ construction enhances cancer cell invasion and metastasis in human CRC. Claudin-4 might be a good biomarker for diagnosing the risk of distant metastasis.