Cytoplasmic eIF6 Promotes OSCC Malignant Behavior Through AKT Pathway

Abstract Background: Eukaryotic translation initiation factor 6 (eIF6), also known as integrin β4 binding protein, is involved in the formation and translation of ribosomes and acts as an anti-association factor. It is also essential for the growth and reproduction of cells, including tumor cells. Yet, its role in oral squamous cell carcinoma (OSCC) remains unclear. Methods: The expression characteristics of eIF6 in 233 samples were comprehensively analyzed by immumohistochemical staining (IHC). Effects of eIF6 over-expression and knockdown on cell proliferation, migration and invasion were determined by CCK-8, wound healing and Transwell assays. Western blot, immunofluorescence (IF) and co-immunoprecipitation (co-IP) were performed for mechanism verification.Results: We found that cytoplasmic eIF6 was abnormally highly expressed in OSCC tissues, and its expression was associated with tumor size and the clinical grade. Amplification of eIF6 promoted the growth, migration, and invasion capabilities of OSCC cell lines in vitro and tumor growth in vivo. Through Western blot analysis, we further discovered that eIF6 significantly promotes epithelial-mesenchymal transformation (EMT) in OSCC cells, while depletion of eIF6 can reverse this process. Mechanistically, eIF6 promotes tumor progression by activating the AKT signaling pathway. By performing co-immunoprecipitation, we discovered a direct interaction between endogenous eIF6 and AKT protein in the cytoplasm. Conclusion: This was the first report on the role and mechanism of eIF6 in OSCC. These results demonstrated that eIF6 could be a new therapeutic target in OSCC, thus providing a new basis for the prognosis of OSCC patients in the future.