4T1 cells that metastasized to the lung express higher level of MCP-1.

<p>A. 1×10⁵ 4T1 cells were injected into a mammary pad of WT or MCP-1^−/− mice. Total RNA was extracted from the lung of tumor-bearing WT or MCP-1^−/− mice and the expression of MCP-1 mRNA was examined by Northern blotting. B. Total RNA was extracted from 4T1 cells obtained from metastatic lung tumors of WT or MCP-1^−/− mice and the expression of MCP-1 mRNA was evaluated by Northern blotting (upper panel). 1×10⁵ cells were seeded into 12-well plates and incubated at 37°C overnight. Medium was replaced by 1 ml fresh medium and incubated for an additional 24 hrs. Cell-free culture supernatants were collected and the concentrations of MCP-1 were measured by ELISA (lower panel). * <i>p<0.01, n = 2</i>.