Saturday, May 31, 2025
5/31/2025
The role, mechanism, and therapeutic potential of METTL1 in acute myeloid leukemia - PROJECT SUMMARY: Acute myeloid leukemia (AML) is a devastating hematopoietic malignancy characterized by clonal expansion of leukemia stem cells (LSCs). Despite advancements in chemotherapy regimens and targeted therapies, most AML patients remain incurable. Thus, novel therapies targeting key leukemogenic pathways are needed. RNA modifications are essential modulators of post-transcriptional gene regulation, and their dysregulation emerges as a contributor to AML. Through an integrated analysis of genome-wide CRISPR/Cas9 screen data, we discovered that AML cells preferentially depend on METTL1, an RNA methyltransferase that mainly catalyzes 7-methylguanosine (m7G) modification on transfer RNAs (tRNAs). METTL1 is highly expressed in LSCs and AML specimens, and its high expression is associated with poor clinical outcomes. METTL1 depletion significantly suppresses AML growth, eradicates LSCs in vitro, and attenuates AML progression in an AML patient-derived xenograft (PDX) model. Importantly, those effects are largely dependent on METTL1’s m7G methyltransferase activity, offering a unique opportunity for AML therapy through the development of small- molecule inhibitors targeting its enzymatic activity. Via a high-throughput screen, we have discovered a selective and potent METTL1 inhibitor with promising anti-AML activity. Moreover, METTL1 loss significantly reduces the m7G abundance on tRNAPheGAA and its overall expression. This, in turn, leads to translation suppression of transcripts that heavily rely on tRNAPheGAA-related codons, such as tyrosine-protein kinase HCK. The decreased expression of HCK due to METTL1 depletion could further disrupt C-X-C chemokine receptor 4 (CXCR4) signaling, which is essential for LSC homeostasis. Despite these insights, we do not yet understand the exact mechanisms by which METTL1 loss results in AML suppression and LSC eradication. We hypothesize that METTL1 functions as an m7G methyltransferase to drive AML development and sustain LSC frequency, making it a potential ‘druggable’ target for treating high-risk AML. These hypotheses will be addressed in three Specific Aims. Aim 1 will further consolidate the importance of METTL1 function in AML using mouse models. In this Aim, we will utilize a number of AML models with different genetic backgrounds to rigorously determine the roles of METTL1 in AML initiation and progression. Aim 2 will understand the role of METTL1/tRNAPheGAA/HCK signaling in LSC homeostasis. This Aim will delineate the molecular mechanism through which the METTL1/m7G axis facilitates LSC homing and self-renewal ability. Aim 3 will evaluate the therapeutic potential of pharmacologically targeting METTL1 to treat AMLs.
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