PCBP2-dependent secretion of miRNAs via extracellular vesicles contributes to the EGFR-driven angiogenesis

Abstract

Rationale: The EGFR-driven angiogenesis is crucial in solid tumors, particularly through the delivery of biomolecules via extracellular vesicles (EVs), but the mechanism by which EGFR regulates EV cargo is still unclear. Methods: First, cell co-culture and murine tumor models were employed to examine the impact of EGFR overexpression on the pro-angiogenic properties of small EVs (sEVs) derived from oral squamous cell carcinoma (OSCC). Small RNA sequencing was then used to compare the miRNA profiles of OSCC-sEVs with and without EGFR overexpression, followed by functional enrichment and motif analyses of the differentially expressed miRNAs. Next, miRNA pull-down assays were conducted to identify potential molecules involved in sorting these miRNAs. Finally, the role of the candidate sorting protein was validated using existing public database, tissue samples, cell lines, and murine tumor models. Results: EGFR overexpression significantly enhances the pro-angiogenic effects of OSCC-sEVs, accompanied by a marked increase in the content of nucleic acid cargo carried in these sEVs. Small-RNA sequencing identified a group of miRNAs that were significantly enriched in OSCC-sEVs due to EGFR overexpression, which primarily functioned in angiogenesis and shared a characteristic "GGGU" motif. EGFR overexpression also strengthened the binding of PCBP2 with miRNAs containing this "GGGU" motif, thereby promoting their secretion through sEVs to support tumor angiogenesis. Mechanismly, EGFR overexpression upregulates PCBP2 protein content by activating its transcription rather than regulating the mRNA stability in OSCC cells. Additionally, depletion of PCBP2 impaired the EGFR-driven tumor angiogenesis by inhibiting the secretion of pro-angiogenic miRNAs through sEVs. Conclusions: EGFR boosts PCBP2 expression via transcriptional regulation, which then promotes the loading of specific miRNAs into sEVs by binding to the "GGGU" motif, thereby driving tumor angiogenesis.

Keywords: angiogenesis; epidermal growth factor receptor; extracellular vesicles; miRNA; oral squamous cell carcinoma; poly(rC) binding protein 2; sorting.