HIGH THROUGHPUT SEQUENCING REVEALS CIRCADIAN RHYTHM GENE RORΑ IS COOPERATIVELY SUPPRESSED BY MULTIPLE MICRORNAS IN ORAL SQUAMOUS CELL CARCINOMA

Objectives To explore the differentially expressed mRNAs and miRNAs in OSCC tissues, and identify the interaction network between miRNAs and trascription factors (TFs). Among them, the regulatory network of miRNAs - circadian gene RORα on proliferation in OSCC was further elucidated. Findings RNA-seq and microRNA-seq analyses show that upregulation of microRNA in OSCC samples significantly contribute to the globally down-regulated transcription factors (TFs) in OSCC. Circadian rhythms genes including three members of retinoic acid receptor-related orphan receptor family (RORα, RORβ and RORγ) and CLOCK were among the down-regulated TFs. RORα was predicted to be targeted by 25 co-upregulated miRNAs, of which, miR-503- 5p, miR-450b-5p, miR-27a-3p, miR-181a-5p and miR-183-5p were further testified to directly target RORα, resulting in a more stronger effect on RORα suppression by mixing together. In addition, we showed that RORα was significantly decreased in most OSCC samples (37 of 44, 84%), and significantly suppressed the proliferation of OSCC cells in vitro and in vivo. Attenuated RORα decreased p53 protein expression and suppressed p53 phosphorylation activity. Conclusions The abnormal miRNAs-mediated TFs network could play important role in OSCC tumorigenesis. Among those TFs, circadian gene RORα acted as a tumor suppressor in OSCC by inhibiting tumor proliferation and could be negatively regulated by miR-503-5p, miR-450b-5p, miR-27a-3p, miR-181a-5p and miR-183-5p cooperatively, which provides clues to understand the clinical link between circadian rhythms and cancer therapy.