Increased MCP-1 expression in 4T1 cells has no effect on spontaneous lung metastasis in MCP-1^−/− mice, but increases lung metastasis after intravenous injection.

<p>A. 1×10⁵ 4T1-L10 cells were injected into a mammary pad of WT or MCP-1^−/− mice. The size of each primary tumor was measured and the area was calculated. <i>n = 4</i> for WT, <i>n = 3</i> for MCP-1^−/− mice. B. 1×10⁵ 4T1-L10 cells were injected into a mammary pad of WT or MCP-1^−/− mice. All mice were euthanized 4 weeks after the injection and the number of metastatic tumor nodules on the surface of each lung was counted by eye. C. Total RNA was extracted from each tumor and the expression of MCP-1 mRNA was examined by Northern analysis. Ten µg of total RNA was used. D. Sera were collected 2 weeks after the injection of 4T1-L10 cells and MCP-1 concentrations were measured by ELISA. E. 4T1-L5 or 4T1-L10 cells (5×10⁴ cells in 0.2 ml PBS) were intravenously injected into WT (left panel) or MCP-1^−/− mice (right panel). Two weeks later, mice were euthanized and the number of metastatic tumor nodules on the lung was counted. The results are the summary of two independent experiments. <i>n = 8</i> for WT, and <i>n = 8</i> (4T1-L5) or <i>n = 9</i> (4Y1-L10) for MCP-1^−/− mice.