N6-methyladenosine plays a dual role in arsenic carcinogenesis by temporal-specific control of core target AKT1

High-profile RNA epigenetic modification N6-methyladenosine (m6A), as a double-edged sword for cancer, can either promote or inhibit arsenic-induced skin carcinogenesis. However, the core m6A-target gene determining the duality of m6A and the regulatory mechanism of m6A on the core gene are still poorly understood. Based on m6A microarray detection, integrated multi-omics analysis, and further experiments in vitro and in vivo, we explored the molecular basis for the dual role of m6A in cancer induced by environmental pollutants using models in different stages of arsenic carcinogenesis, including As-treated, As-transformed, and As-tumorigenic cell models. We found that the key proliferative signaling node AKT1 is in the center of the m6A-regulatory network in arsenic carcinogenicity. The m6A level on AKT1 mRNA (3'UTR, CDS, and 5'UTR) dynamically changed in different stages of arsenic carcinogenesis. The m6A writer METTL3-catalyzed upregulation of m6A promotes AKT1 expression by elevating m6A reader YTHDF1-mediated AKT1 mRNA stability in As-treated and As-transformed cells, while the m6A eraser FTO-catalyzed downregulation of m6A promotes AKT1 expression mainly by inhibiting m6A reader YTHDF2-mediated AKT1 mRNA degradation in As-tumorigenic cells. Furthermore, upregulation of m6A inhibits the expression of AKT1 negative regulator PHLPP2 and promotes the expression of AKT1 positive regulator PDK1. These changes in AKT1 regulators result in AKT1 activation by upregulating AKT1 phosphorylation at S473 and T308. Interestingly, the FTO-catalyzed decrease in m6A prevents AKT upregulation in As-treated cells but promotes AKT upregulation in As-tumorigenic cells. Both inhibitors targeting the m6A writer and eraser can inhibit the AKT1-mediated proliferation of As-tumorigenic cells by breaking the balance of m6A regulators. Our results demonstrated that AKT1 is the core hub determining m6A as a double-edged sword. Changed m6A dynamically upregulates the expression and activity of AKT1 in different stages of arsenic carcinogenesis. This study can advance our understanding of the dual role and precise time-specific mechanism of RNA epigenetics involved in the carcinogenesis of hazardous materials.