Chemical Inhibitors Targeting the Oncogenic mA Modifying Proteins.

Epigenetics is brought to RNA, introducing a new dimension to gene expression regulation. Among numerous RNA modifications, -methyladenosine (mA) is an abundant internal modification on eukaryote mRNA first identified in the 1970s. However, the significance of mA modification in mRNA had been long neglected until the fat mass and obesity-associated (FTO) enzyme was identified as the first mA demethylase almost 40 years later. The mA modification influences nearly every step of RNA metabolism and thus broadly affects gene expression at multiple levels, playing a critical role in many biological processes, including cancer progression, metastasis, and immune evasion. The mA level is dynamically regulated by RNA epigenetic machinery comprising methyltransferases such as methyltransferase-like protein 3 (METTL3), demethylases FTO and AlkB human homologue 5 (ALKBH5), and multiple reader proteins. The understanding of the biology of RNA epigenetics and its translational drug discovery is still in its infancy. It is essential to further develop chemical probes and lead compounds for an in-depth investigation into mA biology and the translational discovery of anticancer drugs targeting mA modifying oncogenic proteins.In this Account, we present our work on the development of chemical inhibitors to regulate mA in mRNA by targeting the FTO demethylase, and the elucidation of their mode of action. We reported rhein to be the first substrate competitive FTO inhibitor. Due to rhein's poor selectivity, we identified meclofenamic acid (MA) that selectively inhibits FTO compared with ALKBH5. Based on the structural complex of MA bound with FTO, we designed MA analogs FB23-2 and Dac51, which exhibit significantly improved activities compared with MA. For example, FB23-2 is specific to FTO inhibition among over 400 other oncogenic proteins, including kinases, proteases, and DNA and histone epigenetic proteins. Mimicking FTO depletion, FB23-2 promotes the differentiation/apoptosis of human acute myeloid leukemia (AML) cells and inhibits the progression of primary cells in xenotransplanted mice. Dac51 treatment impairs the glycolytic activity of tumor cells and restores the function of CD8 T cells, thereby inhibiting the growth of solid tumors . These FTO inhibitors were and will continue to be used as probes to promote biological studies of mA modification and as lead compounds to target FTO in anticancer drug discovery.Toward the end, we also include a brief review of ALKBH5 demethylase inhibitors and METTL3 methyltransferase modulators. Collectively, these small-molecule modulators that selectively target RNA epigenetic proteins will promote in-depth studies on the regulation of gene expression and potentially accelerate anticancer target discovery.