RUNX-NFAT Axis As a Novel Therapeutic Target for AML and T Cell Immunity

Runt-related transcription factor (RUNX) transcription factors are essential regulators of diverse developmental processes. In mammals, there are three RUNX genes, RUNX1, RUNX2, and RUNX3. All RUNX proteins contain a highly conserved DNA-binding domain, called the runt-homology domain (RHD), which is responsible for DNA-binding and interaction with a partner, core binding factor subunit β (CBFβ). They regulate transcription of target genes, involving hematopoietic differentiation, cell cycle regulation, p53 pathways, and so on. From our previous studies, we assume that compensation mechanism is present among the RUNX family members. RUNX plays pivotal roles in leukemogenesis and inhibition of RUNX has now been widely recognized as a novel strategy in anti-leukemic therapies. However, common mechanism via RUNX in diverse acute myeloid leukemia (AML) remains elusive. Here, we demonstrate that targeting RUNX-nuclear factor of activated T cells 2 (NFATC2) axis is an effective strategy to suppress drug-resistant (DR)-acute promyelocytic leukemia (APL) cells. Silencing of RUNX and NFATC2 in DR-APL cells suppressed cell growth and induced apoptotic cell death. Next, by RNA-seq analysis of several AML patient cohorts, we confirmed that a strong positive correlation between RUNX family (RUNX1,2,3: Pan RUNX) and NFAT family (NFATC1,2,3,4, NFAT5: Pan NFAT) exists not only in APL but also in all hematopoietic malignancies and that AML forms the Pan RUNX high-Pan NFAT high expression cluster. Inspection of the NFATC1-3 promoter revealed the RUNX binding sequence, and direct transcriptionally regulation of NFATC1-3 by RUNX family was confirmed in both chromatin immunoprecipitation (ChIP)-seq analysis and dual luciferase reporter assay. We believe that RUNX-NFAT axis could be an important target in diverse AML. Next, considering the well-established role of RUNX and NFATC2 in T cell immunity, we also apply targeting RUNX-NFATC2 strategy to suppress T cell activation and xenogeneic graft-versus-host disease (GVHD).The expansion of donor T cells requires IL-2, and aGVHD has been defined as a Th1-mediated disease. It is now well known that RUNX, especially RUNX1 and RUNX3 , are highly expressed in T cells, and directly regulate Th1 cytokine genes. As immunosuppressive approach for the prevention or treatment of aGVHD, calcineurin inhibitors, cyclosporine A and tacrolimus, inhibit GVHD by preventing the activation of NFAT, and steroid inhibits transcription of proinflammator