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RUNX1 is required for oncogenic Myb and Myc enhancer activity in T cell acute lymphoblastic leukemia

AHyun Choi, Anuradha Illendula, John A. Pulikkan, Justine E. Roderick, Jessica Tesell, Jun Yu, Nicole Hermance, Lihua Julie Zhu, Lucio H. Castilla, John H. Bushweller and Michelle A. Kelliher

Key points

  • RUNX1 maintains Myb and Myc enhancer activity and is required for leukemogenesis in vivo.

  • RUNX1 inhibition impairs the growth of primary T-ALL patient cells without effect on normal human hematopoietic cells.

Abstract

The gene encoding the RUNX1 transcription factor is mutated in a subset of T cell acute lymphoblastic leukemia (T-ALL) patients and RUNX1 mutations are associated with a poor prognosis. These mutations cluster in the DNA binding Runt domain, are thought to represent loss-of-function mutations, indicating that RUNX1 suppresses T cell transformation. RUNX1 has been proposed to have tumor suppressor roles in TLX1/3 transformed human T-ALL cell lines and NOTCH1 T-ALL mouse models. Yet retroviral insertional mutagenesis screens identify RUNX genes as collaborating oncogenes in MYC-driven leukemia mouse models. To elucidate RUNX1 function(s) in leukemogenesis, we generated Tal1/Lmo2/Rosa26-CreERT2Runx1f/f mice and examined leukemia progression in the presence of vehicle or tamoxifen. We found that Runx1 deletion inhibits mouse leukemic growth in vivo and that RUNX silencing in human T-ALL cells triggers apoptosis. We demonstrate that a small molecule inhibitor, designed to interfere with CBFβ binding to RUNX proteins, impairs the growth of human T-ALL cell lines and primary patient samples. We demonstrate that a RUNX1 deficiency alters the expression of a crucial subset of TAL1- and NOTCH1-regulated genes including the MYB and MYC oncogenes, respectively. These studies provide genetic and pharmacologic evidence that RUNX1 has oncogenic roles and reveal RUNX1 as a novel therapeutic target in T-ALL.

  • Submitted March 27, 2017.
  • Accepted July 24, 2017.