MiR-18b-3p promotes cell proliferation and metastasis by directly inhibiting PTEN expression in osteosarcoma

Osteosarcoma (OS), the most prevalent primary malignant bone tumor in adolescents, demonstrates aggressive clinical behavior and poor prognosis. This study aimed to elucidate the functional role and molecular mechanism of miR-18b-3p in OS pathogenesis.

The miRNA microarray data from the GEO database were evaluated through GEO2R. The expression patterns of miR-18b-3p and PTEN were systematically analyzed using RT-qPCR and western blotting. A dual-luciferase reporter assay validated the direct targeting relationship between miR-18b-3p and PTEN 3'-UTR. Functional experiments included CCK-8, wound healing, and transwell invasion assays, and xenograft mouse models. Bioinformatics predictions were further supported by Gene Ontology enrichment analysis, protein-protein interaction network construction, and single-cell RNA sequencing analysis.

Integrated bioinformatics interrogation identified miR-18b-3p as a prognostically characteristic gene, with its overexpression strongly correlating with reduced overall survival in OS patients (p = 0.046). Clinical specimens and cellular models revealed marked upregulation of miR-18b-3p in OS tissues and cell lines (U2OS, MG63, HOS, SAOS2) compared to normal controls. PTEN was subsequently identified as a direct downstream target through complementary binding site verification, showing inverse correlation with miR-18b-3p expression. Functional experiments demonstrated that miR-18b-3p overexpression significantly enhanced malignant phenotypes, including cellular proliferation, migration, and invasion capacity, while PTEN restoration effectively reversed these oncogenic effects. Additionally, OS cells (HOS and SAOS2) secreted miR-18b-3p, and this paracrine mechanism potentially reprogrammed the tumor microenvironment through suppressing PTEN expressed in various immune and stromal cells.

Our findings establish miR-18b-3p as a novel oncogenic regulator in OS pathogenesis through direct PTEN targeting, highlighting its potential as a therapeutic target.