Leukemic Cytokines co-opt Regulatory T cell and Th17 immunity to promote chronic myeloid leukemia

Abstract

Abstract Non-immune roles of Regulatory T cells (Tregs) have been described across various tissues. However, the mechanisms by which T cells regulate the bone marrow in myeloproliferative neoplasms lack resolution. A hallmark of leukemic progression is the increase in pro-inflammatory cytokines, cellular inflammation, and an expansion of CD4 T cells. In this study, we demonstrate that this inflammatory milieu promotes pathogenic skewing of both regulatory and effector T cells. We characterized the altered CD4+ T cell compartment in chronic myeloid leukemia (CML) and we found that Tregs are unstable and dysregulated across leukemic tissues. Specifically, the CML environment effectively co-opts Treg function and stability. This contributes to a phenotype of immune activation as well as an increase of pathogenic inflammatory T cells. Notably, our findings reveal that Treg/Th17 ratios are disrupted in leukemia and that loss of Tregs and activation of Th17 cells influence disease progression. Additionally, we found that Treg-secreted IL-10 directly influences myeloid and neutrophil differentiation of leukemic progenitors has beneficial anti-inflammatory effects. We demonstrate that restoring Treg function and expanding their IL-10 production can be used therapeutically to limit leukemic progression. Our results support the hypothesis that Tregs are compromised during leukemic progression as a consequence of pro-inflammatory cytokines from the myeloid associated disease. These findings highlight how the Treg/Th17 balance regulates disease progression. Furthermore, these studies provide an avenue by which Treg secreted IL-10 can be used for therapeutic intervention in the context of hematopoietic malignancies.