MUC1 and neoplasm: The binding of mucin 1-sialylated core 1 (MUC1-ST) to siglec-9 on monocytes and macrophages can induce the release of factors such as IL-8, IL-6, macrophage colony-stimulating factor (M-CSF), and plasminogen activator inhibitor-1 (PAI-1), that promote tumor growth and induce macrophages to develop a tumor-associated macrophages (TAM) phenotype (Fig. 4A, III) [115, 116].