The tumor cells and the tumor stroma can produce factors such as transforming growth factor (TGF)-β, IL1, IL6β, GM-CSF, tumor necrosis factor (TNF)-α, vascular endothelial growth factor (VEGF), chemokine (C-C motif) ligand 2 (CCL2), chemokine (C-X-C motif) ligand (CXCL)12 and CXCL15 [17]. The gene discussed is CCL2; the disease is neoplasm.