Integrating CRISPR knockout, interference, and activation to dissect the functional role and underlying signaling of microRNA-23a-27a-24-2 cluster in hepatocellular carcinoma

The miR-23a-27a-24-2 cluster is overexpressed in human cancers, including hepatocellular carcinoma (HCC). However, the role of three mature miRNAs of the miR-23a-27a-24-2 cluster in HCC is still controversial. Also, the integrative role of the miR-23a-27a-24-2 cluster in HCC remains elusive. In the present study, using CRISPR knockout (KO), CRISPR interference (CRISPRi), and CRISPR activation (CRISPRa) technologies, we established an endogenous miR-23a-27a-24-2 controllable and various knockout (KO) cell models, which were used to dissect the functional role and underlying signaling of the miR-23a-27a-24-2 cluster. Either miR-23a KO or miR-27a KO reduced cell growth in vitro and in vivo. Of particular note, endogenous miRNAs in the miR-23a-27a-24-2 cluster were effectively regulated by CRISPRi/a, identifying an integrated oncogenic role of the miR-23a-27a-24-2 cluster in HCC cells. Functional analysis showed that miR-23a KO and miR-27a KO led the cell cycle arrest, especially at the G2/M phase, by reducing CDK1/cyclin B activation in HCC cells. Furthermore, a high-throughput RNA-seq approach with miRNA target prediction identified the miR-23a/miR-27a-regulated gene network, further validated by various technologies. In addition, miR-23a and miR-27a have opposite roles in cell migration and mesenchymal-epithelial transition. However, an integrated analysis by CRISPRi/a suggested an oncogenic role of the miR-23a-27a-24-2 cluster in cell migration, which may require a miR-23a-BMPR2-Smad-Snail axis in HCC cells. Thus, our CRISPRi/a study offers a valuable research tool for dissecting the integrated role and underlying mechanism of an endogenous miRNA cluster. Also, this CRISPR approach may provide new routes of miRNA intervention for miRNA targeted therapy.