EZH1 and chronic myelogenous leukemia, BCR-ABL1 positive: Interestingly, recent evidence from Agarwal et al. (2019) demonstrates that CXCL12 levels in mesenchymal stromal cells (MSCs) may influence EZH2 and EZH1 expression levels in CML stem cells indicating a role for the bone marrow microenvironment (BMM) on this effect.