Upregulation of TCTP expression in human skin squamous cell carcinoma increases tumor cell viability through anti-apoptotic action of the protein.

The translationally controlled tumor protein (TCTP) is an anti-apoptotic protein, which is highly expressed in several human cancer types. However, the role of TCTP in skin cancers, including squamous cell carcinoma (SCC), has not been investigated. In this study, we analyzed the expression of TCTP in cutaneous SCC samples using immunohistochemistry in two epidermoid SCC cell lines, A431 and SCL-1, using western blot analysis. We further investigated the role of TCTP in skin cancinogenesis by silencing the TPT1 gene using small interfering RNA (siRNA) in the SCC cell line A431. Our results demonstrated that TCTP was overexpressed in cutaneous SCC cells, compared to normal skin keratinocytes. In addition, the expression of TCTP in skin SCC significantly increased with the grade of malignancy. Western blot analysis further confirmed that the expression of TCTP in the cell lines, A431 and SCL-1, was significantly higher compared to that in the normal keratinocyte cell line, HaCaT. The expression of TCTP in A431 cells was significantly downregulated by transfection with our specifically designed TCTP siRNA. We found that downregulation of TCTP expression was associated with decreased cell proliferation and increased apoptosis in A431 cells. These results suggest that the TPT1 gene may be a potential therapeutic target in skin SCC through a siRNA approach.