Project description:SPINK1 overexpression defines the second largest subtype of prostate cancer (PCa), however molecular mechanisms underlying its upregulation remains poorly understood. Here, we identified the role of miR-338-5p and miR-421 in post-transcriptional regulation of SPINK1. We established that miR-338-5p/miR-421 mediates several cellular responses against SPINK1-positive cancer by targeting oncogenic long non-coding RNA (lncRNA) MALAT1, inducing cell-cycle arrest, inhibiting epithelial-to-mesenchymal transition (EMT), cancer-stemness and drug resistance. Moreover, ectopic expression of miR-338-5p/miR-421 abrogates SPINK1-mediated oncogenesis, tumor growth and distant metastases in murine model. Importantly, RNA-sequencing expression analysis revealed an inverse correlation between miRNAs and SPINK1 or MALAT1 in PCa patients’ specimens. Further, we demonstrate Polycomb group protein EZH2-mediated epigenetic silencing of miR-338-5p/miR-421 in SPINK1-positive subtype. Thus, restoring miR-338-5p/miR-421 expression using epigenetic drugs or synthetic mimics could abrogate SPINK1-mediated oncogenesis by targeting multiple oncogenic pathways and eliciting anti-cancer pleiotropic effects. Taken together, the present study unravels the molecular mechanism underlying SPINK1 overexpression and suggests miR-338-5p and miR-421 replacement therapy for the treatment of SPINK1-positive malignancies.
