STAT3 and cancer: miRNAs in the let-7 family are commonly downregulated in various cancers including HCC and target and downregulate a number of proteins playing important roles in tumorigenesis and metastasis, such an Ras [44], high-mobility group AT-hook 2 (HMGA2) [45], myc [46], and signal transducer and activator of transcription 3 (STAT3) [41].