E-Poster Presentation 33rd Lorne Cancer Conference 2021

MYC antagonist MNT: A new target for acute myeloid leukaemia (#161)

Karla Charlotte Fischer 1 2 , Suzanne Cory 1 2
  1. The Walter and Eliza Hall Institute of Medical Research, Parkville, VICTORIA, Australia
  2. Department of Medical Biology, University of Melbourne, Parkville, VICTORIA, Australia

Acute myeloid leukaemia (AML) is a highly heterogeneous haemopoietic malignancy characterized by excessive proliferation and accumulation of immature myeloid blasts in the bone marrow. AML has a very poor 5-year survival rate of just 15% and thus remains a major clinical challenge.

AML can arise from diverse genetic changes, but amongst the most common are chromosomal translocations/inversions involving the gene MLL (mixed lineage leukemia). More than 100 MLL fusion partners have been identified, but several of the most common (AF9, ENL, AF4, AF10 and ELL) are components of a transcriptional activation complex, which is why most MLL gene rearrangements result in deregulated transcription of MLL target genes. Critically, MLL fusion proteins directly activate the c-MYC gene and a high level of c-MYC protein (hereafter MYC) correlates with poor outcome in AML.

MYC is a basic Helix-Loop-Helix Leucine Zipper (bHLHLZ) transcriptional activator that controls numerous genes involved in cell growth, cell cycle progression, metabolism, DNA damage responses and malignant transformation. However, under conditions of stress (eg cytokine or nutrient deprivation), cells expressing elevated MYC undergo apoptosis, particularly at high MYC levels, and this serves as a critical restraint on MYC-driven neoplastic transformation. MYC heterodimerises with MAX, another ubiquitously expressed bHLHLZ protein, and together they bind the E-box CACGTG (and variants) in regulatory regions of target genes.

MAX also binds several MYC-related transcriptional repressors, most notably MNT1, which is essential for development and widely expressed in adult tissues. Recent mouse genetic studies2-4 have shown, unexpectedly, that MNT facilitates MYC-driven lymphomagenesis, by suppressing MYC-driven apoptosis. Based on these findings, we set out to test whether MYC-driven AMLs are also dependent on MNT. Our preliminary findings show that MNT loss very significantly extends the life of mice transplanted with MLL-AF9 AMLs. Thus, MNT may be an exciting new drug target for AML.

  1. Hurlin, P. J., Quéva, C. & Eisenman, R. N. Mnt, a novel Max-interacting protein is coexpressed with Myc in proliferating cells and mediates repression at Myc binding sites. Genes & development 11, 44-58, doi:10.1101/gad.11.1.44 (1997).
  2. Link, J. M. et al. A critical role for Mnt in Myc-driven T-cell proliferation and oncogenesis. Proceedings of the National Academy of Sciences of the United States of America 109, 19685-19690, doi:10.1073/pnas.1206406109 (2012).
  3. Campbell, K. J., Vandenberg, C. J., Anstee, N. S., Hurlin, P. J. & Cory, S. Mnt modulates Myc-driven lymphomagenesis. Cell death and differentiation 24, 2117-2126, doi:10.1038/cdd.2017.131 (2017).
  4. Nguyen, H. V. et al. Development and survival of MYC-driven lymphomas require the MYC antagonist MNT to curb MYC-induced apoptosis. Blood 135, 1019-1031, doi:10.1182/blood.2019003014 (2020).