miR-3682-3p directly targets FOXO3 and stimulates tumor stemness in hepatocellular carcinoma via a positive feedback loop involving FOXO3/PI3K/AKT/c-Myc

BACKGROUND

Cancer stem cells (CSCs) have been implicated in tumorigenesis and tumor recurrence and metastasis are key therapeutic targets in cancer treatment. MicroRNAs display therapeutic potential by controlling the properties of CSCs; however, whether an association exists between miR-3682-3p and CSCs is unknown.

AIM

To investigate the mechanism by which miR-3682-3p promotes stemness maintenance in hepatocellular carcinoma (HCC).

METHODS

MiR-3682-3p expression in HCC cell lines and 34 pairs of normal and HCC specimens was assayed by quantitative polymerase chain reaction. The functional role of miR-3682-3p was investigated in vitro and in vivo. Dual-luciferase reporter and chromatin immunoprecipitation assays were performed for target assessment, and western blotting was utilized to confirm miR-3682-3p/target relationships.

RESULTS

We found that miR-3682-3p plays a key role in HCC pathogenesis by promoting HCC cell stemness. The upregulation of miR-3682-3p enhanced CSC spheroid-forming ability, side population cell fractions, and the expression of CSC factors in HCC cells in vitro and the tumorigenicity of transplanted HCC cells in vivo. Furthermore, silencing miR-3682-3p prolonged the survival of HCC-bearing mice. Mechanistically, we found that miR-3682-3p targets FOXO3 and enables FOXO3/β-catenin interaction, which promotes c-Myc expression through PI3K/AKT; c-Myc, in turn, activates miR-3682-3p, forming a positive feedback loop. Intriguingly, miR-3682-3p expression was induced by hepatitis B virus X protein (HBx) and was involved in HBx-induced tumor stemness-related pathogenesis.

CONCLUSION

Our findings reveal a novel mechanism by which miR-3682-3p promotes stemness in HCC stem cells. Silencing miR-3682-3p may represent a novel therapeutic strategy for HCC.

Key Words: miR-3682-3p, FOXO3, Cancer stem cells, Hepatocellular carcinoma

Core Tip: In this work, we identified miR-3682-3p as a key inducer of cancer stem cell properties, thereby promoting the pathogenesis of hepatocellular carcinoma (HCC). In brief, we found that the upregulation of miR-3682-3p enhanced the spheroid forming ability, the fraction of side population cells, and the expression of cancer stem cell factors in HCC cells in vitro as well as the tumorigenicity of transplanted HCC cells in vivo; furthermore, silencing miR-3682-3p significantly prolonged the survival time of HCC-bearing mice. Mechanistically, we found that miR-3682-3p targets FOXO3 and enables FOXO3/β-catenin interaction, which promotes c-Myc expression through PI3K/AKT; c-Myc, in turn, activates miR-3682-3p, resulting in the formation of a positive feedback loop. Taken together, we identified a novel positive feedback regulatory loop involving HBx, miR-3682-3p, FOXO3, β-catenin, and c-Myc that plays a pivotal role in the stemness of HCC. Our findings revealed a novel mechanism by which miR-3682-3p promotes stem cell maintenance in HCC, and silencing miR-3682-3p may represent a novel therapeutic strategy for the treatment of this cancer.

• Citation: Chen Q, Yang SB, Zhang YW, Han SY, Jia L, Li B, Zhang Y, Zuo S. miR-3682-3p directly targets FOXO3 and stimulates tumor stemness in hepatocellular carcinoma via a positive feedback loop involving FOXO3/PI3K/AKT/c-Myc. World J Stem Cells 2022; 14(7): 539-555
• URL: https://www.wjgnet.com/1948-0210/full/v14/i7/539.htm
• DOI: https://dx.doi.org/10.4252/wjsc.v14.i7.539