METTL16-mediated inhibition of MXD4 promotes leukemia through activation of the MYC-MAX axis.

N6-methyladenosine (m(6)A) is an RNA modification that governs multiple aspects of RNA metabolism, including splicing, translation, stability, decay, and the processing of marked transcripts. Although accumulating evidence suggests that the m(6)A writer METTL16 is involved in leukemia, the molecular pathway(s) by which it contributes to leukemogenesis remain unexplored. In this study, we shed light on a novel molecular mechanism whereby METTL16 plays a role in acute myeloid leukemia (AML) progression through an m(6)A-dependent manner. Our investigations revealed that METTL16 is overexpressed in primary AML cells. Genetic depletion of METTL16 or its pharmacological inhibition strongly affected the proliferation of AML cells, eventually triggering apoptosis. Transcriptome-wide analysis identified mRNA of MAX Dimerization Protein 4 (MXD4), a MYC pathway regulator, as a downstream target of METTL16. Mechanistically, we showed that METTL16 controls the stability of MXD4 mRNA, resulting in a reduction in MXD4 protein levels that indirectly activates the MYC-MAX axis, essential for leukemogenesis. Strikingly, the suppression of MXD4 rescued the expression levels of MYC target genes, restoring AML cell survival. Our findings unveil a novel METTL16-MXD4 oncogenic axis crucial for AML progression, establishing small-molecule inhibition of METTL16 as a potential therapeutic approach in leukemia and providing a new strategy to target MYC activity in cancer. Molecular model of METTL16-MXD4 axis controlling AML progression by regulating MYC activity. (A) METTL16 installs m(6)A on MXD4 mRNA, decreasing its stability and resulting in decreased MXD4 protein levels. (B) MXD4 reduction ensures MYC-MAX complex formation, MYC target gene expression, and AML cell growth. (C) Silencing or chemical inhibition of METTL16 stabilizes MXD4 mRNA and increases its protein levels. (D) (1) Increased MXD4 proteins may counteract MYC binding with its partner MAX, thus repressing expression of MYC target genes (early event); (2) MXD4 binds to MYC regulatory regions, decreasing MYC expression (late event) and affecting AML proliferation.