Background/Aims: The most common type of oral cancer is known as oral squamous cell carcinoma (OSCC) which is a highly invasive malignant tumor with frequent cervical lymph node metastasis.Despite the advanced therapeutic strategies for OSCC, the 5-year survival rate of patients with OSCC is merely 50%. Therefore, it is necessary to find novel prognostic factors and treatment modalities to prevent OSCC progression. Cripto-1 or teratocarcinoma-derived growth factor-1 (TDGF-1) is a member of the epidermal growth factor–Cripto-1/FRL-1/Cryptic (EGF–CFC) family. Cripto-1 has been found to be overexpressed in several human cancers including breast, colon, lung, cervix, stomach, and pancreatic cancer. Epithelial-to-mesenchymal transition (EMT) is process that is physiologically involved in development, tissue regeneration and wound healing. In Vitro and in vivo studies have shown that Cripto-1 plays important oncogenic roles during tumorigenesis and tumor progression by promoting cell proliferation, migration, invasion and tumor angiogenesis as well as induction of EMT. In OSCC,EMT is a critical event to enhance the migration and invasion of OSCC cells. Therefore, the aims of this study were to determine whether knockdown of Cripto-1 by siRNA could inhibit cell proliferation and migration in OSCC cell lines, and to identify the molecular mechanism of Cripto-1 to play an oncogenic role in OSCC. Methods:Cripto-1 expression in 13 OSCC cell lines was evaluated by western blotting. In Vitro Cell proliferation and migration assays were performed using HSC-3 and HSC-4, which showed relatively high expression of Cripto-1. For Cripto-1 knockdown, cells were transfected with 50nM of siRNA. The inhibition of Cripto-1 expression was confirmed by western blotting. WST-1 assay was used to evaluate cell proliferation. Cell migration was assessed using a transwell assay. In order to investigate the molecular mechanism of Cripto-1, Cripto-1 expression was inhibited in HSC-3 cells and the following changes of downstreaming signaling were examined by western blotting. Results: In the cell proliferation assay, transfection with anti-Cripto-1 siRNA (50nM)induced a statistically significant decrease in the proliferation of HSC-3 and HSC-4 (p < .001 , respectively). In the cell migration assay, after 48h and 72h incubation, there was a statistically significant decrease in migration of both cells transfected with the anti-Cripto-1 siRNA at every time point, respectively. (p < .001). After knockdown of Cripto-1, the activities of p-AKT (ser473) and p-ERK1 / 2 (Thr202 / Tyr204) were markedly decreased but the expression of p-Src was not changed. Expression of nucleus NF-κB, Slug, Twist which are related with EMT, was decreased. E-cadherin expression was increased, but vimentin expression was decreased. In addition, expression of MMP-2 was not changed but expression of MMP-9 was remarkably decreased.Conclusion: Knockdown of Cripto-1 could significantly inhibit cell proliferation and migration of OSCC cells through the AKT/MAPK signaling pathway. In addition, Cripto-1 could regulate the cell migration of OSCC by modulating EMT-related molecules and MMP-9. Therefore, suppression of Cripto-1 may be a new therapeutic strategies for the patients with OSCC.
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