Cancer cells can secrete leukocyte attracting chemokines, such as C-C Motif Chemokine Ligand 2 (CCL2), CCL4, CCL5, CCL7, CCL8, and CCL20 leading to an infiltration of tumor associated macrophages, neutrophils, T cells, and dendritic cells [105,106,107]. The gene discussed is CCL2; the disease is cancer.