CDKN1A and leukemia: Considering (i) the shared cellular features between macrophages and senescent cells22, (ii) the ability of senescent cells to phagocytose live tumor cells23, and (iii) the pivotal roles of p21 in the senescence24, terminal differentiation, and survival of macrophages25–28, we assessed the role of p21 to identify molecular mechanisms regulating the macrophage-mediated phagocytosis of leukemia cells.