Regulation of IGF2BP1 by miR-186 and its impact on downstream lncRNAs H19, FOXD2-AS1, and SNHG3 in HCC

We have previously characterized oncogenic properties of IGF2BP1 in HCC, and its regulation by short noncoding RNAs (ncRNAs). Recent evidence suggests that IGF2BP1 itself may regulate long ncRNAs (lncRNAs). Therefore, this study aimed at exploring the interplay between IGF2BP1 and various upstream and downstream ncRNAs and its link to HCC pathogenesis.Bioinformatic analysis was used to identify up- and downstream ncRNAs interacting with IGF2BP1. Huh-7 cells were transfected with siRNAs against IGF2BP1 and microRNA mimics. Relative gene expression was determined using RTqPCR and IGF2BP1 protein was quantified by western blot. Luciferase binding assay was used to explore the targeting of IGF2BP1 3'UTR. HCC tumorigenesis was measured by MTT assay, BrdU-incorporation assay, colony-forming assay, and scratch assay.Bioinformatic analysis identified three oncogenic lncRNAs - namely H19, FOXD2-AS1, and SNHG3 - potentially regulated by IGF2BP1. Knockdown of IGF2BP1 decreased the expression of all three oncogenic lncRNAs and inhibited malignant cell behaviors. miR-186 was revealed as a possible upstream regulator of IGF2BP1. miR-186 mimics decreased IGF2BP1 mRNA and protein levels. miR-186 was significantly lower while IGF2BP1 was elevated in cancerous tissues from ten HCC patients compared to five healthy controls. In addition, miR-186 mimics caused a downregulation of the oncogenic lncRNAs H19, SNHG3, and FOXD2-AS1 and a concomitant decrease in cell viability, proliferation, migration, and clonogenicity.miR-186 may exert tumor suppressor effects in HCC by repressing oncogenic lncRNAs H19, SNHG3, and FOXD2-AS1 through its effect on IGF2BP1.