VIRMA-Dependent N6-Methyladenosine Modifications Regulate the Expression of Long Non-Coding RNAs CCAT1 and CCAT2 in Prostate Cancer

RNA methylation at position N6 in adenosine (m(6)A) and its associated methyltransferase complex (MTC) are involved in tumorigenesis. We aimed to explore m(6)A biological function for long non-coding RNAs (lncRNAs) in prostate cancer (PCa) and its clinical significance. m(6)A and MTC levels in PCa cells were characterized by ELISA and western blot. Putative m(6)A-regulated lncRNAs were identified and validated by lncRNA profiler qPCR array and bioinformatics analysis, followed by m(6)A/RNA co-immunoprecipitation. Impact of m(6)A depletion on RNA stability was assessed by Actinomycin D assay. The association of m(6)A-levels with PCa prognosis was examined in clinical samples. Higher m(6)A-levels and VIRMA overexpression were detected in metastatic castration-resistant PCa (mCRPC) cells (p < 0.05). VIRMA knockdown in PC-3 cells significantly decreased m(6)A-levels (p = 0.0317), attenuated malignant phenotype and suppressed the expression of oncogenic lncRNAs CCAT1 and CCAT2 (p < 0.00001). VIRMA depletion and m(6)A reduction decreased the stability and abundance of CCAT1/2 transcripts. Higher expression of VIRMA, CCAT1, and CCAT2 as a group variable was an independent predictor of poor prognosis (HR = 9.083, CI95% 1.911-43.183, p = 0.006). VIRMA is a critical factor sustaining m(6)A-levels in PCa cells. VIRMA downregulation attenuates the aggressive phenotype of PCa by overall reduction of m(6)A-levels decreasing stability and abundance of oncogenic lncRNAs.