CBX4 enhances acute monocytic leukemia development via HDAC-mediated suppression of Runx1

Acute monocytic leukemia (AML-M5) is a type of acute myeloid leukemia, characterized by a dominance of monocytes in the bone marrow and peripheral blood. AML-M5 exhibits a poor prognosis compared to other AML subtypes. Despite clinical recognition, current research on AML-M5 remains relatively limited, and its underlying pathogenic mechanisms are not yet fully understood. In this study, we uncover a distinct and heightened expression of CBX4, a core component of PRC1, in the peripheral blood of individuals diagnosed with AML-M5. By generating cbx4 overexpression transgenic and deleted mutant zebrafish lines, we observe elevated cbx4 expression in monocyte/macrophage, selectively modulating their production during zebrafish hematopoiesis. Notably, aging zebrafish with cbx4 overexpression exhibit a progression to AML-M5-like hematopoiesis. Further mechanistic analyses reveal that Cbx4 regulates the fate of monocyte/macrophage lineage by suppressing runx1 expression. This suppression is achieved through the recruitment of HDAC to the runx1 promoter via cbx4, resulting in the down-regulation of the H3K27 acetylation level of runx1. These findings offer novel insights, providing potential avenues for risk assessment and molecular diagnosis of AML-M5 leukemia. Moreover, CBX4 emerges as a promising target for the diagnosis and treatment of AML-M5 leukemia.