Kdm6b is Required for Self-Renewal of Normal and Leukemic Stem Cells Under Proliferative Stress

Recent studies have indicated that the histone 3 lysine 27 (H3K27me2/3) demethylase KDM6B (JMJD3) is frequently upregulated in a myriad of blood disorders including myelodysplastic syndrome (MDS), T-cell acute lymphoblastic leukemia (T-ALL), and multiple myeloma (MM) suggesting it may have important functions in the pathogenesis of hematopoietic cancers. Here, we sought to determine the role of Kdm6b in hematopoietic stem cell (HSC) fate decisions under normal and malignant conditions to evaluate its potential as a therapeutic target. We show that loss of Kdm6b leads to a significant reduction in phenotypic and functional HSCs in adult mice, and that Kdm6b is necessary for HSC self-renewal in response to inflammatory, genotoxic and oncogenic stress. Additionally, we show that loss of Kdm6b in HSCs leads to a stress-response gene expression signature in native HSCs that is independent of its demethylase activity. Loss of Kdm6b lead to increased expression of a subset of genes implicated in HSC quiescence (e.g. Fos, Jun, Ier2, Dusp1, Zfp36). Upon inflammatory or replicative stress, HSCs deficient for Kdm6b are not able to efficiently resolve this gene expression program, leading to increased quiescence and a self-renewal block, forcing them to differentiate. These findings show that Kdm6b is necessary for self-renewal of normal and leukemic stem cells, and suggest inhibiting Kdm6b in blood cancers in the presence of proliferative agents may force differentiation and eventual depletion of leukemic stem cells.