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Figure 5 | Breast Cancer Research

Figure 5

From: Different mechanisms for resistance to trastuzumab versus lapatinib in HER2- positive breast cancers - role of estrogen receptor and HER2 reactivation

Figure 5

BT474 lapatinib resistant cells with prolonged treatment reactivate HER receptor activity. (A) Growth curves of UACC-812 and BT474 late stage lapatinib resistant cells (LLR) treated with different targeted therapies for nine days: trastuzumab (T) (10 μg/ml), lapatinib (L) (1 μM), trastuzumab plus lapatinib, or endocrine therapy, fulvestrant (F) (10-7M). Significance between groups was determined by multiple comparisons using the Sidak method (*P = 0.0008, BT474 LLR + L versus LLR + L + F, *P = 0.0044, BT474 LLR + L versus LLR + L + T; *P < 0.0001, UACC-812 LLR + L versus LLR + L + F). (B) Immunohistochemical detection of ER, PR, and phospho-HER2 (Tyr877) in BT474 late stage lapatinib resistant cells. (C) Western blot analysis of UACC-812 and BT474 parental and resistant cell lines, including early (LR) and late (LLR) stage lapatinib resistant cells. Whole-cell extracts were analyzed by Western blot with the indicated antibodies. (D) BT474 parental, early, late stage lapatinib resistant, and combination (L + T) resistant cells were treated with fulvestrant for 24, 48, or 72 h and whole-cell extracts were analyzed by Western blot with the indicated antibodies.

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