Stable knockdown of MMP-1 is associated with reduced TGFα in culture supernatants. A, MMP-1 and TGFα protein levels in conditioned media were measured by ELISA. Cells were cultured in MEM with 5% FBS to 80% confluence. Supernatants were separated and concentrated, and MMP-1 and TGFα protein concentrations were measured by ELISA. Asterisks indicate significant differences (P < 0.05) in TGFα in culture supernatants from control shRNA expressing cells compared with MMP-1 shRNA expressing cells. This data shown are representative of 3 independent experiments. B, TGFα concentrations in conditioned media were measured by ELISA after 24 h incubation with MMP-1 inhibitor at 2 μM, in serum free medium. This data shown are representative of 3 independent experiments. C, Immunoblotting for phospho-EGFR, total EGFR and β-actin protein levels in each cell line cultured in culture medium with 5% FBS. This experiment was performed in triplicate.