Expression of PDGFRβ and Abl in breast cancer cell lines. A. Wt MCF7 and LTED cells were screened for kinase expression using western blotting. Cells were grown under basal conditions. Whole cell extracts were probed using antibodies against the indicated proteins. B. Wt MCF7 and C. LTED cells were seeded into 96 well plates and transfected with small interfering RNA (siRNA) control, siPDGFRβ, siAbl or the combination of both and then treated ± E2 for 96 hours. Proliferation was measured using Cell Titre glo. Data are representative of three individual experiments. Error bars express ± SEM * P < 0.05, ** P < 0.01. Abl, Abelson tyrosine kinase; E2, estradiol; LTED, long term estrogen deprived; PDGFRβ, platelet derived growth factor receptor β; SEM, standard error of the mean; siRNA small interfering RNA; Wt, wild type.