To clarify the mechanism of action of let-7c, we tried to elucidate the relation between let-7c and its targets: IGF1R and HMGA2. We demonstrated that the expression levels of IGF1R and HMGA2 were significantly higher in HNSCC tumor tissues compared to non-tumor tissues, corresponding to downregulation of let-7c. The gene discussed is IGF1R; the disease is head and neck squamous cell carcinoma.