To investigate whether let-7c exerted its effects by regulating IGF1R and HMGA2 in HNSCC cells, we re-expressed the coding region sequence of IGF1R or HMGA2 in let-7c stably transfected SAS cells (SAS-let-7c) using the pCMV6-IGF1R or pCMV6-HMGA2 plasmid, respectively. Here, IGF1R is linked to head and neck squamous cell carcinoma.