For tumor growth at the macroscopic scale, we have as variables the densities of live and dead tumor cells, macrophages, and endothelial cells (ECs), and the concentrations of cytokines interacting among the cells: monocyte chemoattractant protein-1 (MCP-1/CCL2), vascular endothelial growth factor (VEGF), and soluble VEGF receptor-1 (sVEGFR-1). The gene discussed is CCL2; the disease is neoplasm.