RNAi-mediated down-regulation of α-actinin-4 decreases invasion potential in oral squamous cell carcinoma

α-actinin-4, originally identified as an actin-binding protein associated with cell motility, invasion, and metastasis of cancer cells, appears to be overexpressed in various human epithelial carcinomas, including colorectal, breast, esophageal, ovarian, and non-small cell lung carcinomas. The authors evaluated whether α-actinin-4 might be appropriate as a molecular target for cancer gene therapy. In 64 primary oral squamous cell carcinomas (OSCCs) and 10 normal oral mucosal specimens, and in seven human OSCC cell lines, α-actinin-4 expression was evaluated immunologically and correlations with clinicopathologic factors were examined. Overexpression of α-actinin-4 was detected in 38 of 64 oral squamous cell carcinomas (70%); significantly more frequently than in normal oral mucosa. The expression of α-actinin-4 was significantly associated with invasion potential defined by the Matrigel invasion assay. Cancer cell lines with higher α-actinin-4 expression had greater invasive potential. An RNAi-mediated decrease in α-actinin-4 expression reduced the invasion potential. These results indicated that the overexpression of α-actinin-4 was associated with an aggressive phenotype of OSCC. The study indicated that α-actinin-4 could be a potential molecular target for gene therapy by RNAi targeting for OSCC.