Hepatocyte growth factor stimulates Met phosphorylation and enhances clonogenic survival in the presence of gefitinib. (A) SUM102 and SUM149 cells were cultured with condition media from RMF-HGF fibroblasts for 1 hour in the presence or absence of 0.5 μM gefitinib (gef). Lysates were prepared and analyzed for Met phosphorylation using immunoblotting. Met and β-actin expression levels were used as controls. CM, pro-hepatocyte growth factor (pro-HGF) conditioned media; UT, untreated. (B) SUM102 and SUM149 cells were treated with conditioned media from RMF-HGF fibroblasts in the presence or absence of the indicated concentration of gefitinib or erlotinib for 7 days, adding fresh drug and conditioned media (CM) every other day. Cells were trypsinized, replated, and grown under normal growth conditions for 7 days. Colonies were stained using crystal violet and counted using a cell counter. Each experiment was performed in triplicate at least three times. Student's t test was used to determine survival differences between gefitinib-treated cells in the presence or absence of conditioned media.