Semaphorin-7A contributes to growth, migration and invasion of oral tongue squamous cell carcinoma through TGF-β-mediated EMT signaling pathway.

Abstract

Oral tongue squamous cell carcinoma (OTSCC) is the most frequently encountered malignant epithelial tumors. Semaphorin-7A is a membrane-associated/secreted protein that plays an essential role in the migration and progression of human malignancies. We aimed to investigate the mechanisms of Semaphorin-7A in the growth and migration of OTSCC. The expressions of Semaphorin-7A in cells were tested by RT-PCR, Western blot, and Immunofluorescence, separately. The activities of OTSCC cells (HSC-3 and Tca8113) were analyzed by MTT, following treatment with Semaphorin-7A or PBS. The migration, invasion, and apoptosis of cells were also determined. The protein expressions of epithelial mesenchymal transition (EMT) pathway were analyzed by Western blot, after treated with Semaphorin-7A in vitro and in vivo. Finally, the mouse model of OTSCC was treated with antibody target for Semaphorin-7A (AntiSema-7A), Semaphorin-7A or PBS, then the tumor size was determined, and histopathological examination and western blot was applied for further confirmation. In OTSCC cells, Semaphorin-7A was highly expressed, and Semaphorin-7A promoted growth in multiple metastatic OTSCC cell lines. Further study indicated that Semaphorin-7A resulted in up-regulation of Snail, N-cadherin and Vimentin expression, and downregulating of E-cadherin. In addition, The Ets2-repressor factor (ERF) expression was down-regulated, and transforming growth factor (TGF-β)-induced EMT was promoted in OTSCC cells. Then, the proteins of collagen types I (CT-I) and fibronectin (FIB) were also up-regulated after Semaphorin-7A treatment. Furthermore, our results indicated that inhibition of Semaphorin-7A by antibody target for Semaphorin-7A (AntiSema-7A) suppressed OTSCC growth and increased survival in a mouse model of OTSCC. Histopathological examination confirmed the inhibitory effects in vivo. Semaphorin-7A promoted growth and migration of OTSCC by regulating TGF-β-induced EMT signaling pathway in OTSCC cells, which provided a new interconnection between the Semaphorin-7A and TGF-β-induced EMT signaling pathway.