Figure 1 Expression of platelet derived growth factor receptor β (PDGFRβ) in malignant mesothelioma (MMe) cells. (A) Immunoblotting with PDGFRβ, c‐Kit and c‐Fms antibodies on human mesothelial cells (HMC) and three representative MMe cell lines. Controls: human dermal fibroblasts (HDF) expressing PDGFRβ and CCRF, CCRF‐HSB‐2, human leukaemic lymphoblast cells expressing c‐Kit and c‐Fms. (B) Immunoprecipitation with PDGFRβ antibodies followed by immunoblotting with phosphotyrosine antibodies (upper panel); immunoblotting with the indicated antibodies on whole lysates (lower panel). In both panels MMP, REN and ISTMES2 cells were in low serum (−) or stimulated with PDGF in the presence or absence of 10 μM imatinib or (C) 100 nM wortmannin. (D) Immunoblotting with P‐Akt (P‐Ser 473) antibodies of MMP cells stimulated by 50 ng/ml hepatocyte growth factor (HGF) in the presence or absence of 10 μM imatinib.