Interestingly, the expression of MCP-1 was elevated in 4T1 cells that metastasized to the lung and intravenous injection of 4T1 cells producing a high level of MCP-1 resulted in a higher number of tumor foci in the lung of WT and MCP-1−/− mice, suggesting that the tumor cell-derived MCP-1 also promotes lung metastasis by supporting the tumor cell survival, seeding and growth in the lung. This evidence concerns the gene CCL2 and neoplasm.