The reduced VEGF secretion by htMSCs in coculture with 4T1 cells suggests that the expression of IL-8 and MCP-1 by htMSCs at the tumor microenvironment after coinjection of mesenchymal and tumor cells strongly regulates the increased primary and metastatic tumor development, by chemoattracting secondary immune cells, with a minor participation of VEGF in these conditions. The gene discussed is CCL2; the disease is metastatic neoplasm.