Constitutive association of TF with integrins in breast cancer cells. (A) TF-integrin interaction in breast cancer cells is VIIa independent. MDA-MB-231mfp cells were treated with 50 μg/mL antibody for 10 minutes before addition of 10 nmol/L VIIa. Coimmunoprecipitation with α3β1 was quantified in 4 separate experiments, mean and standard deviations are shown. (B) Mab-10H10 does not precipitate the TF-β1 integrin complex. Cells were lysed, and lysate was subjected to immunoprecipitation with control antibody, β1 antibody, Mab-10H10, or Mab-5G9. Immunoprecipitates were analyzed for the presence of β1 and TF by Western blotting. (C) VIIa, Mab-10H10, and Mab-5G9 do not influence TF coimmunoprecipitation with α2 integrin. MDA-MB-231mfp cells were treated with 50 μg/mL antibody for 10 minutes before addition of 10 nmol/L VIIa. Coimmunoprecipitation of TF with α2 was analyzed by Western blot. (D) Constitutive association of TF with β1 integrins is independent of the extracellular matrix. Cells were grown on collagen 1 or a laminin 5-rich matrix and immunoprecipitated after 1 hour Mab-10H10 or Mab-5G9 treatment.