Prostate cancer (PCa) is the leading cause of cancer-related mortality among men, largely due to acquired resistance to standard therapies. Comprehensive transcriptional analyses across thousands of PCa specimens revealed a marked upregulation of critical DNA methylation regulators, including DNA methyltransferases and demethylases, particularly during progression to androgen independence. Importantly, these enzymes were identified as direct targets of miR-29a/b/c-3p, whose expression is notably suppressed during PCa progression. We hypothesized that restoring miR-29 expression could reverse aberrant epigenetic regulation, potentially reactivating epigenetically-silenced tumor-suppressive pathways.

To test this hypothesis, androgen-independent prostate cancer cell lines (PC3, DU145, LNCaP-abl, 22Rv1) were treated with miR-29 mimics for isoforms a, b, and c. Cells were collected at multiple time points (48-192 hours), followed by transcriptomic analyses, real-time PCR, Annexin V-PI apoptosis and migration assays to evaluate gene expression changes and functional outcomes.

Transcriptomic analysis following miR-29 mimic in PC3 cells revealed substantial gene expression changes, notably increased pro-apoptotic mediators and decreased expression of genes involved in cell invasion and extracellular matrix remodeling. Functional assays confirmed significant miR-29-induced apoptosis and inhibition of migration capacities. Furthermore, a single miR-29 mimic treatment induced sustained cell-cycle arrest in PC3 cells for up to 10 days. Our expanded analyses demonstrated that miR-29 mimic treatment preferentially induced significant growth inhibition in TP53-deficient prostate cancer cell lines (PC3, DU145), whereas TP53 wild-type cells (LNCaP-abl, 22Rv1) remained largely unaffected. This selective sensitivity highlights a novel context-dependent mechanism, whereby miR-29 restoration compensates for TP53 loss by directly reactivating downstream p53-related apoptotic pathways. Notably, miR-29 itself is a TP53-induced transcript, suggesting that its reactivation may bypass the loss of functional TP53.

Collectively, these findings position miR-29 reactivation as a potential therapeutic strategy to reverse epigenetic dysregulation and overcome treatment resistance in advanced prostate cancer.