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Figure 3 | Breast Cancer Research

Figure 3

From: Direct inhibition of PI3K in combination with dual HER2 inhibitors is required for optimal antitumor activity in HER2+ breast cancer cells

Figure 3

Lapatinib-resistant PIK3CA mutant cell lines show reactivation of phosphoinositide 3-kinase and utilize mutant p110α for phosphoinositide 3-kinase signaling. (A) Cells expressing E545K or H1047R were selected for lapatinib resistance. Unselected cells (Pre) were treated with lapatinib for 3 hours and analyzed along with lapatinib-resistant (LR) cells in the presence of lapatinib by immunoblotting with the indicated antibodies. (B) Lapatinib-sensitive and LR cells were treated with lapatinib and/or BKM120 for 3 hours, and lysates were analyzed by immunoblotting. (C) Phosphoinositide 3-kinase (PI3K) was immunoprecipitated from PIK3CA mutant–expressing cells before and after selection for lapatinib resistance with a p85 antibody. Complexes were separated by SDS-PAGE, and expression of mutant p110α was determined by immunoblot analysis for the hemagglutinin (HA)-tag. (D) HA band intensity detected by infrared fluorescence was quantified using a LI-COR Odyssey imaging system. Mean HA intensity normalized to p85 intensity from at least four replicate experiments is shown (bars = SEM).

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Breast Cancer Research

ISSN: 1465-542X

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