p16 and its putative interplay with metabolic factors in prostate cancer: An analysis based on public TCGA data

p16 is one of the most common tumour suppressor genes, mainly due to its genetic inactivation. However, the clinical significance of p16 in prostate cancer is not yet fully understood, and although p16 acts as a tumour suppressor gene, stress or oncogenic factors or alternative molecular events may overcome the role of p16 as a negative cell cycle regulator. p16 seems to be involved in the metabolic switch to glycolysis during tumorigenesis, possibly interacting with NADPH oxidase 4 (NOX4) and pyruvate kinase type M2 (PKM2), involved in energy metabolism, with differences depending on cell type. The aim of this study was to assess the putative crosstalk between p16, NOX4 and PKM2, with an involvement of miRNA-mediated regulation, in prostate cancer. Transcriptome data from a cohort of 243 patients were extracted from The Cancer Genome Atlas (TCGA) database. An elevated p16 expression level was significantly associated a high Gleason score, decreasing with the score (P<0.0001). NOX4 and PKM2 expression exhibited a similar trend as p16, with higher values in the samples with Gleason scores of 9-10 samples (P<0.0001 and P=0.02, respectively). Moreover, bioinformatics analysis by TargetScan revealed that miR-625-5p could bind to the 3'UTR of p16. A consequential pairing of the NOX4 and PKM2 target region with miR-23a-3p and miR-122-5p, respectively was also found. Of note, the miR-625-5p levels inversely correlated with p16 expression, miR-23a-3p and miR-122 with NOX4 and PKM2, respectively (data not shown). Taken together, these data suggest an interplay between p16 and metabolic factors, such as NOX4 and PKM2, and a miRNA regulation, with a potential clinical impact for the development of novel therapeutic strategies in prostate tumours.