KITLG and breast cancer: Interestingly, BC cells contribute to the establishment of MDSCs by influencing hematopoiesis and myeloid cell differentiation by secreting various cytokines–for example, granulocyte–macrophage colony stimulating factor (GM-CSF) [218], in addition to granulocyte-colony stimulating factor (G-CSF), M-CSF, macrophage migration inhibitory factor (MIF), PGE2, stem cell factor (SCF), VEGF, TGF-1β, IL-1β, IL-6, and IL-10 (Fig. 9) [219, 220].