CXCL12 and melanoma: TAMs account for up to 30% of the melanoma tumor content (Hussein, 2006) and are polarized to an M2-like, immunosuppressive phenotype by melanoma cell-derived factors including but not limited to the B-cell lymphoma 2 protein (Di Martile et al., 2020), acidosis (Vitale et al., 2019), colony-stimulating factor 1, CXCL12 and CCL2 (Pieniazek et al., 2018).