Antitumor miR-150-5p and miR-150-3p inhibit cancer cell aggressiveness by targeting SPOCK1 in head and neck squamous cell carcinoma

Objective: Our recent studies have revealed that both strands of pre-miRNAs, the guide strand and the passenger strand, are involved in cancer pathogenesis. Analyses of miRNA expression signatures by RNA sequencing in head and neck squamous cell carcinoma (HNSCC) showed that both of the strands of pre-miR-150 (miR-150-5p and miR-150-3p) were significantly downregulated, and that these miRNAs acted as antitumor miRNAs in HNSCC cells. The aim of this study was to identify oncogenic genes in HNSCC cells that were regulated by miR-150-5p and miR-150-3p. Methods: Genome-wide gene expression studies, in silico analyses and dual-luciferase reporter assays were carried out to predict miR-150-5p and miR-150-3p regulation in HNSCC cells. Knockdown assay was applied to investigate the functional significance of the target gene. Overall patient survival as a function of target gene expression was estimated by The Cancer Genome Atlas (TCGA) database. Results: A total of 19 genes were putative targets of both miR-150-5p and miR-150-3p regulation. Among them, SPOCKI (SPARC/osteonectin, cwcv and kazal-like domains proteoglycan 1) was directly regulated by both miRNAs in HNSCC cells. Knockdown studies using si-SPOCKI showed that expression of SPOCKI enhanced HNSCC cell aggressiveness. Overexpression of SPOCK 1/SPOCKI was confirmed in HNSCC clinical specimens. Interestingly, analysis of a large number of patients in the TCGA database (n = 248) demonstrated that patients with high SPOCK] expression had significantly shorter survival than did those with low SPOCKI expression (P = 0.0003). Moreover, 15 pathways were identified as SPOCKI-mediated downstream pathways. Conclusion: Downregulation of both strands of pre-miR-150 (miR-150-5p and miR-150-3p) and overexpression of SPOCKI contribute to the aggressive nature of HNSCC. The involvement of passenger strand miRNA in the regulation of HNSCC pathogenesis is a novel concept in RNA research. (C) 2017 Elsevier B.V. All rights reserved.