CSF1R and leukemia: Evidence shows that IL-34 plays an important role in cancer through direct or indirect mechanisms.26 Tumor cell-derived IL-34 acts as an autocrine in CSF-1R-expressing tumor cells to provide a proliferative signal for tumor growth and survival signal for tumor cells against chemotherapy.27 IL-34 also acts as a paracrine to educate macrophages to tumor-associated macrophages, which in turn contribute to tumor progression.28,29 However, the role of IL-34 in leukemia and the related mechanism have not been well established.