{
  "abstract": "Background Acute Myeloid Leukemia (AML) is the most lethal form of adult leukemia. Standard chemotherapy for AML has remained largely unchanged over the last four decades. Immunotherapy is a promising therapy in many cancers including AML. T cell exhaustion (Tex) is observed in cancers including AML and epigenetic modifications play a major role in this phenomenon. Studies have shown that loss of DNA methylation can restore T cell effector function overcoming exhaustion in chronic viral settings. Hypomethylating agents such as Azacytidine (Aza) are used in patients unfit for chemotherapy because a variety of mutations occur that target methylation programs in AML. Recent findings suggest Aza can reprogram immune responses, therefore we investigated the effect of Aza on Tex in AML.Methods We have developed a spontaneous mouse model of AML where FLT3-ITD is knocked into its endogenous locus and TET2 is knocked out in the myeloid lineage. Mice with AML were treated with Aza or vehicle control for 3 weeks (n= 6-8/group). We analyzed myeloid and T cell/Tex markers in blood, bone marrow and spleen using flow cytometry. Bisulphite sequencing was performed on isolated CD4 and CD8+ T cells. T cell proliferation and cytokine production potential was assessed. Killing assays using human AML cell lines and healthy T cells were also performed. Statistical tests were done with PRISM 10.Results Aza enhances naïve and central memory T cell populations, reduces Tregs and inhibitory checkpoint markers. Bisulphite sequencing revealed Aza-induced hypomethylation of key T cell function genes, including Tcf7 and E2f2. Notably, Aza increased TCF1 expression, which is associated with reduced T cell exhaustion. We observed upregulation of E2F2 protein expression upon Aza treatment. Functionally, Aza restored proliferation in both CD4+ and CD8+ T cells in AML mice. In combination, Aza boosts bispecific antibody mediated AML killing by human T cells. Additionally, we observed VISTA upregulation on myeloid cells following Aza treatment.Conclusions Immune evasion and exhaustion are recognized barriers to effective durable treatment responses, but the underlying mechanisms remain elusive in leukemia. We show that Aza has the potential to restore Tex in AML. Current work includes gaining mechanistic insights on how TCF7 and E2F2 can elicit this effect. Next steps include combining Aza with VISTA blockade and other immunotherapy.",
  "authors": [
    {
      "affiliations": [
        "Cell, Developmental and Cancer Biology, Oregon Health and Science University, Portland, OR, USA"
      ],
      "name": "Ravina Pandita"
    },
    {
      "affiliations": [
        "Department of Molecular Microbiology and Immunology, Oregon Health and Science University, Portland, OR, USA"
      ],
      "name": "Yoko Kosaka"
    },
    {
      "affiliations": [
        "Department of Molecular Microbiology and Immunology, Oregon Health and Science University, Portland, OR, USA"
      ],
      "name": "Jessica Mulkey"
    },
    {
      "affiliations": [
        "Division of Oncological Sciences, Oregon Health and Science University, Portland, OR, USA"
      ],
      "name": "Brett A Davis"
    },
    {
      "affiliations": [
        "Department of Molecular and Medical Genetics, Oregon Health and Science University, Portland, OR, USA"
      ],
      "name": "Lucia Carbone"
    },
    {
      "affiliations": [
        "Oregon Health and Science University, Portland, OR, USA"
      ],
      "name": "Evan F Lind"
    }
  ],
  "title": "695 Investigating the effects of azacytidine on T cell exhaustion in AML",
  "uid": "e52f58d5-1b09-5228-97c6-faa0b47a0e26"
}