Mir-483-5p-mediated activating of IGF2/H19 enhancer up-regulates IGF2/H19 expression via chromatin loops to promote the malignant progression of hepatocellular carcinoma.

Background: The insulin-like growth factor 2 (IGF2) and H19 are overexpressed in hepatocellular carcinoma (HCC). IGF2-derived miR-483-5p is implicated in the development of cancers. Here, we investigated the involvement of miR-483-5p in IGF2 and H19 overexpression regulation and its role in HCC.

Methods: Firstly, the effect of miR-483-5p on the expression of IGF2 and H19, and the binding of miR-483-5p to IGF2/H19 enhancer were evaluated in HCC cells. Next, miR-483-5p-mediated IGF2/H19 enhancer activation and its mechanism were investigated in HCC cells. Then, the mechanism by which active IGF2/H19 enhancer mediated by miR-483-5p activate IGF2/H19 promoters was studied in HCC cells. Finally, the effect of MED1 on the expression of IGF2/H19 as well as the malignant phenotype of HCC cells in vitro and in vivo mediated by miR-483-5p was evaluated.

Results: Mir-483-5p up-regulated IGF2 P2 mRNA-P4 mRNA and H19 expression by binding to IGF2/H19 enhancer resulting in IGF2/H19 enhancer activation in HCC cells. Mechanistically, miR-483-5p increased recruitment of Ago1 and Ago2 at IGF2/H19 enhancer and then activated transcription of IGF2/H19 eRNA by RNA polymerase II and p300, which further induced chromatin loops formation between IGF2/H19 enhancer and IGF2/H19 promoters to activate IGF2/H19 promoters via IGF2/H19 eRNA-MED1-IGF2/H19 promoters complex in HCC cells. In this process, MED1 promoted chromatin loops formation as well as the malignant phenotype of HCC cells in vitro and in vivo mediated by miR-483-5p.

Conclusions: miR-483-5p-mediated activating of IGF2/H19 enhancer up-regulates IGF2/H19 expression via DNA loops, thereby promoting the malignant progression of HCC.