STAT3 and chronic myelogenous leukemia, BCR-ABL1 positive: Many factors in the bone marrow microenvironment that provide signals to CML LSCs for homing and survival (e.g., SDF1, FGF2, IL-8, WNT, miRNA, TGF-β, and STAT3/5) have been described, while immune cells, such as regulatory T cells, myeloid-derived suppressor cells (MDSCs), T cells, and—most importantly—natural killer (NK) cells, prevent disease progression and patrol residual LSCs in patients on TKI therapy (Fig. 2).