LAUSR

Background N6-methyladenosine (m 6 A) is the most abundant modification in mRNA of humans. Emerging evidence has supported the fact that m 6 A is comprehensively involved in various diseases especially cancers. As a crucial reader, YTHDF2 usually mediates the degradation of m 6 A-modified mRNAs in m 6 A-dependent way. However, the function and mechanisms of m 6 A especially YTHDF2 in prostate cancer (PCa) still remain elusive. Methods To investigate the functions and mechanisms of YTHDF2 in PCa, in vitro , in vivo biofunctional assays and epigenetics experiments were performed. Endogenous expression silencing of YTHDF2 and METTL3 was established with lentivirus-based shRNA technique. Colony formation, flow cytometry and trans-well assays were performed for cell function identifications. Subcutaneous xenografts and metastatic mice models were combined with in vivo imaging system to investigate the phenotypes when knocking down YTHDF2 and METTL3. m 6 A RNA immunoprecipitation (MeRIP) sequencing, mRNA sequencing, RIP-RT-qPCR and bioinformatics analysis were mainly used to screen and validate the direct common targets of YTHDF2 and METTL3. In addition, TCGA database was also used to analyze the expression pattern of YTHDF2, METTL3 and the common target LHPP in PCa, and their correlation with clinical prognosis. Results The upregulated YTHDF2 and METTL3 in PCa predicted a worse overall survival rate. Knocking down YTHDF2 or METTL3 markedly inhibited the proliferation and migration of PCa in vivo and in vitro. LHPP and NKX3–1 were identified as the direct targets of both YTHDF2 and METTL3. YTHDF2 directly bound to the m 6 A modification sites of LHPP and NKX3–1 to mediate the mRNA degradation. Knock-down of YTHDF2 or METTL3 significantly induced the expression of LHPP and NKX3–1 at both mRNA and protein level with inhibited phosphorylated AKT. Overexpression of LHPP and NKX3–1 presented the consistent phenotypes and AKT phosphorylation inhibition with knock-down of YTHDF2 or METTL3. Phosphorylated AKT was consequently confirmed as the downstream of METTL3/YTHDF2/LHPP/NKX3–1 to induce tumor proliferation and migration. Conclusion We propose a novel regulatory mechanism in which YTHDF2 mediates the mRNA degradation of the tumor suppressors LHPP and NKX3–1 in m 6 A-dependent way to regulate AKT phosphorylation-induced tumor progression in prostate cancer. We hope our findings may provide new concepts of PCa biology.