PCBP2 facilitates miR-93-5p-mediated repression of GDF11 in HCC cell lines

Growth differentiation factor 11 (GDF11), a member of the transforming growth factor-β superfamily, functions in skeletal muscle and neuronal regeneration and has been implicated in tumor suppression. In hepatocellular carcinoma (HCC), GDF11 expression is markedly downregulated, but the mechanisms responsible for this repression remain unclear. In this study, we examined whether the oncogenic miR-106b-25 cluster contributes to GDF11 suppression in HCC. We found that this cluster decreases GDF11 expression at both the mRNA and protein levels, with miR-93-5p acting as the dominant regulator. Inhibition of miR-93-5p with antisense oligonucleotides restored GDF11 expression and reduced HCC cell proliferation, migration, and invasion. Mechanistically, we identified the RNA-binding protein (RBP) PCBP2 as a key facilitator of miR-93-5p targeting of GDF11. PCBP2 binds a C-rich element adjacent to the miR-93-5p target site in the GDF11 3' UTR, thereby enhancing miR-93-5p-mediated repression. PCBP2 knockout attenuated miR-93-5p-mediated repression, whereas re-expression of PCBP2 restored it, supporting its modulatory role. Collectively, these findings identify PCBP2 as a modulator of miR-93-5p-mediated GDF11 repression and suggest that this regulatory interaction contributes to HCC cell proliferation, migration, and invasion. This work provides insights into the post-transcriptional control of the tumor suppressor and highlights the therapeutic potential of targeting miRNA-RBP interactions.