Up-regulation of INSR/IGF1R by C-myc promotes TSCC tumorigenesis and metastasis through the NF-κB pathway

The insulin receptor (INSR) and insulin-like growth factor 1 receptor (IGF1R) have been reported to be involved in the tumorigenesis and metastasis of various malignancies. The aim of our study was to investigate and compare the effects of INSR and IGF1R on the tumorigenesis and metastasis of tongue squamous cell carcinoma (TSCC) and explore the possible mechanism(s) involved. We found that INSR had the same up-regulated expression pattern as IGF1R in TSCC tissues. INSR and IGF1R up-regulation were correlated with each other and associated with lymph node metastasis and poor prognosis. Functional studies established that knocking down either INSR or IGF1R dramatically impeded TSCC cell proliferation, migration, and invasion in vitro and tumorigenesis and tumor metastasis in vivo, whereas ectopic overexpression of INSR or IGF1R enhanced these activities. Both INSR and IGF1R directly targeted p65 and activated the NF-kappa B pathway; furthermore, C-myc was observed to directly bind to the INSR and IGF1R promoters and up-regulates INSR and IGF1R expression in TSCC. Thus, our current data demonstrate that both INSR and IGF1R are directly targeted by C-myc and exert similar effects to promote the tumorigenesis and metastasis of TSCC through the NF-kappa B pathway. Therefore, INSR and IGF1R may be therapeutic target genes and potential prognostic factors for TSCC.