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Polycomb Group protein EZH2-mediated transcriptional repression of microRNA-338/-421 drives SPINK1-positive prostate cancer

ABSTRACT: 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.

ORGANISM(S): Homo sapiens

PROVIDER: GSE108558 | GEO | 2018/12/30

REPOSITORIES: GEO

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Project description:Glioblastoma multiforme (GBM) is the most aggressive form of brain tumors. Despite radical surgery and radiotherapy supported by chemotherapy, the disease still remains incurable with extremely low median survival rate of 12-15 months from the time of initial diagnosis. The main cause of treatment failure is considered to be the presence of cells that are resistant to such treatment. MicroRNAs (miRNAs) as regulators of gene expression are involved in the tumor pathogenesis, including GBM. MiR-338 is a brain specific miRNA which has been described to target pathways involved in proliferation and differentiation. In our study, miR-338-3p and -5p were differentially expressed in GBM tissue in comparison to non-tumor brain tissue. Overexpression of miR-338-3p with miRNA mimic did not show any changes in proliferation rates in GBM cell lines (A172, T98G, U87MG). On the other hand, pre-miR-338-5p notably decreased proliferation and caused cell cycle arrest. Since radiation is currently the main treatment modality in GBM, we combined overexpression of pre-miR-338-5p with radiation, which led to significantly decreased of cell proliferation, and increased cell cycle arrest and apoptosis in comparison to only irradiated cells. To better elucidate the mechanism of action, we performed gene expression profiling analysis that revealed targets of miR-338-5p being Ndfip1, Rheb, ppp2R5a. These genes have been described to be involved in DNA damage response, proliferation and cell cycle regulation. To our knowledge, this is the first study to describe role of miR-338-5p in GBM and its potential to improve sensitivity of GBM to radiation. Study was performed on three glioblastoma multiforme cell lines A172, T98G and U87MG. This experiment was performed on Affymetrix GeneChip Human Gene ST 1.0 to elucidate the targets of miRNA-338-5p. Cell lines were seeded 24 hours prior transfection. After transfection with pre-miR338-5p or negative control cell were cultured for 24 hours and harvested. RNA was isolated using MirVana miRNA Isolation Kit (Ambion, USA) and checked for RNA integrity by Bioanalyzer 2100 and purity by ratios 260/280>1.8 and 260/230>1.8 by Nanodrop2000.

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Polycomb Group protein EZH2-mediated transcriptional repression of microRNA-338/-421 drives SPINK1-positive prostate cancer

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