(A) Comparison of mRNA expression of Src family members in BT-474, BT-474-R and BT-474-RL2 by q-RT-PCR. Fgr, Blk and Hck was not detected. Data are shown as means + SE. The assay was repeated three times. (B) Western blot analysis of Yes1 protein expression among BT-474, BT-474-R and BT-474-RL2. (C) Copy number assay of Yes1 in BT-474, BT-474-R and BT-474-RL2. Human Genomic DNA (HGD) was used as the control (2 copies). Data are shown as means + SE. The assay was repeated three times. (D) Protein expression profile after Yes1 knockdown by Yes1 siRNA in BT-474, BT-474-R and BT-474-RL2. (E) MTS assay assessing the sensitivity to trastuzumab or lapatinib among BT-474, BT-474-R and BT-474-RL2 after Yes1 knockdown. Cells (3,000/well) were seeded in 96-well plates and transfected with siRNA for 48 hours followed by the treatment of trastuzumab or lapatinib for 72 hours. Data are shown as means + SE. The assay was repeated three times.