Investigating the role of microRNAs in the hypoxic response in prostate cancer

Abstract

Introduction: Hypoxia (a pathologically low oxygen level) is a well-established driver of aggressive behaviour inprostate cancer (PCa). However, the reasons for this are not completely characterised and the role of microRNAs(miRNAs) in the hypoxic response remains unclear. In this study we investigate the expression and functional role ofmiRNAs in response to hypoxia in prostate cancer.Methods: Three models of PCa hypoxia were utilised (i) in vitro culture at 0.1% oxygen (ii) 3D spheroid culture and(iii) an in vivo tumour xenograft experiment. miRNA expression was measured by RT-qPCR. miRNA overexpressionwas achieved by transfection and the effect on selected targets was assessed by RT-qPCR and Western blots. Cellproliferation, apoptosis, migration and invasion abilities were assessed by functional bioassays. miRNA-seq andmRNA-seq was used to examine expression patterns in a small cohort of prostate biopsies. Bionformatic analysis ofprostate cancer data in The Cancer Genome Atlas (TCGA) repository was also performed.Results: Several miRNAs were identified as being affected by hypoxia in prostate cells. Among these, miR-210 andmiR-21 were shown to be upregulated by hypoxia in our various models. The subsequent effect on their respectivenetworks of target genes was explored and we demonstrate for the first time that miR-210 targets neural celladhesion molecule (NCAM) in prostate cells. miR-210 and miR-21 expression was positively correlated with markersof hypoxia and tumour aggressiveness in clinical samples, suggesting they may have value as novel biomarkers in thisdisease.Discussion: We provide evidence that various miRNAs can contribute to the progression of PCa throughhypoxia-related mechanisms. In particular, miR-210 and miR-21 appear to play key roles in the hypoxic responsewhich can contribute to PCa progression. We propose that miRNA profiling of these and other miRNAs has greatvalue for improving diagnostic, prognostic and potential therapeutic approaches in this disease