Co-overexpression of cortactin and CRKII increases migration and invasive potential in oral squamous cell carcinoma

Cortactin stimulates cell migration, invasion, and experimental metastasis. Overexpression of cortactin has been reported in several human cancers. CRK was originally identified as an oncogene product of v-CRK in a CT10 chicken retrovirus system. Overexpression of CRKII has been reported in several human cancers. CRKII regulates cell migration, morphogenesis, invasion, phagocytosis, and survival; however, the underlying mechanisms are not well understood. We evaluated the possibility of the combination of cortactin and CRKII as an appropriate molecular target for cancer gene therapy. The expression of cortactin and CRKII in 70 primary oral squamous cell carcinomas and 10 normal oral mucosal specimens was determined immunohistochemically, and the correlation of cortactin and CRKII co-overexpression with clinicopathological factors was evaluated. Co-overexpression of cortactin and CRKII was detected in 31 of 70 oral squamous cell carcinomas, the frequency being significantly greater than in normal oral mucosa. In addition, cortactin and CRKII co-overexpression was more frequent in higher-grade cancers according to the T classification, N classification, and invasive pattern. RNAi-mediated co-suppression of cortactin and CRKII expression reduced the migration and invasion potential of an oral squamous cell carcinoma cell line, OSC20. Downregulation of cortactin and CRKII expression also reduced the expression of vimentin, fibronectin, and N-cadherin. These results indicate that the co-overexpression of cortactin and CRKII may be tightly associated with an aggressive phenotype of oral squamous cell carcinoma. Therefore, we propose that the combination of cortactin and CRKII could be a potential molecular target of gene therapy by RNAi-targeting in oral squamous cell carcinoma.