(1) Background: The gold standard, prostate-specific antigen (PSA) screening lacks the sensitivity and specificity required for confident, early prostate-cancer detection. MicroRNAs (miRNAs) are small, highly stable, non-coding RNAs whose expression changes reproducibly in malignancy and therefore offer promise as minimally invasive biomarkers. Although prostate cancer biopsies are the gold standard for prostate cancer diagnosis, limitations in the field continue to persist. Since circulating fluids can also be a source of miRNA biomarkers, we investigated the overlap between miRNAs enriched in prostate cancer tissue and those isolated from the plasma of patients with prostate cancer. (2) Methods: We synthesized the published literature (PubMed, Google Scholar, ResearchGate, 2005–April 2025) and re-analyzed three Gene Expression Omnibus (GEO) datasets (GSE54516, GSE21032—tissue; GSE206793—plasma) to identify miRNAs consistently dysregulated in prostate cancer tissue and circulation. (3) Results: Of the 318 screened full-text articles, 24 met the inclusion criteria. From the GEO reanalysis (false-discovery-rate < 0.05, |log2FC| ≥ 1), 219 and 326 miRNAs were differentially expressed in tissue, whereas 12 were altered in plasma. Two miRNAs—miR-449b and miR-455-3p—were common in both compartments, highlighting their translational potential as liquid biopsy surrogates of tumor biology. (4) Conclusions: We summarize functional evidence for leading tumor-suppressive (e.g., miR-205, miR-23b, miR-455-3p) and oncogenic (e.g., miR-21, miR-182, miR-449b) candidates, discuss their intersection with the androgen-receptor, TGF-β, WNT/β-catenin, and PI3K-AKT signaling, and outline outstanding requirements for the clinical qualification of miRNA panels in prostate cancer.
Kallinikas et al. (Tue,) studied this question.