Azacytidine restores T cell function in AML by modulating DNA methylation

AML is an aggressive blood cancer associated with poor clinical outcomes. Chemotherapy remains the standard of treatment, but unfortunately relapse is very common, highlighting the need for alternative therapies. T cell dysfunction and exhaustion are prominent in AML and may represent a barrier to effective immunotherapy yet remains poorly studied in AML. DNA methylation is a major driver of T cell exhaustion and inhibition of de novo methylation can block exhaustion and restore T cell function in chronic viral infections and other cancers but is understudied in AML. Here, we investigated the impact of azacytidine (Aza), an FDA-approved hypomethylating agent, on T cell exhaustion in AML. Using a spontaneous AML mouse model and samples from patients with AML, we found that Aza treatment modulates T cell function. In vivo Aza-treatment of AML-bearing mice decreased tumor burden and reshaped CD8+ T cell states, with increases in frequencies of memory subsets and decreases in regulatory T cells (Tregs). Functionally, Aza treatment overcame the impaired proliferation displayed by both CD4 and CD8+ T cells in our model. DNA methylation sequencing of T cells after Aza treatment revealed hypomethylation and increased expression of stem-like precursor gene TCF7 and E2F2, a regulator of cell cycle progression and proliferation. Similar changes in phenotypes were observed in cultures of AML patient samples treated with Aza. Collectively, we show that Aza remodels epigenetic and functional states in AML and has the potential to reverse T cell exhaustion, with enhanced memory and proliferation capacity. Our work generates a mechanistic framework that provides rationale of combining hypomethylating agents with T cell-based immunotherapies in this lethal disease.