mA RNA modification modulates PI3K/Akt/mTOR signal pathway in Gastrointestinal Cancer.

Methylation at the N6 position of adenosine (mA) is the most prevalent RNA modification within protein-coding mRNAs in mammals, and it is a reversible modification with various important biological functions. The formation and function of mA are regulated by methyltransferases (writers), demethylases (erasers), and special binding proteins (readers) as key factors. However, the underlying modification mechanisms of mA in gastrointestinal (GI) cancer remain unclear. Here, we performed comprehensive molecular profiling of the nine known mA writer, eraser, and reader proteins in GI cancer. Data from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) were used. Gene alteration and pathway analysis were done in cBioportal. The protein network of mA regulators and its related pathway members was analyzed in STRING online platform. Phylogenetic tree was constructed in MEGA7. mA modification sites were predicted by SRAMP. mA related SNPs were analyzed by mASNP. The modulation of mA on its related pathway members was validated by mA-seq, real-time PCR and phosphor-MAPK array. We found that mA regulators were mostly upregulated in GI cancer and their differential expression significantly influenced the overall survival of patients with GI cancer. The phosphatidylinositol-3-kinase (PI3K)/Akt and mammalian target of rapamycin (mTOR) signaling pathways were found to be potentially affected by mA modification in most human cancers, including GI cancer, which was further verified by mA-Seq and phospho-MAPK array. Our findings suggest that mA RNA modification has a fundamental role in the regulation of PI3K/Akt and mTOR signaling pathway function in cancer.