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Ref Type Journal Article
PMID (17638894)
Authors Piechocki MP, Yoo GH, Dibbley SK, Lonardo F
Title Breast cancer expressing the activated HER2/neu is sensitive to gefitinib in vitro and in vivo and acquires resistance through a novel point mutation in the HER2/neu.
Journal Cancer research
Vol 67
Issue 14
Date 2007 Jul 15
URL
Abstract Text The HER2/neu oncogene is an important diagnostic and prognostic factor and therapeutic target in breast and other cancers. We developed and characterized a breast cancer cell line (Bam1a) that overexpresses the activated HER2/neu and ErbB-3 and has a gene expression profile consistent with the ErbB-2 genetic signature. We evaluated the effects of the epidermal growth factor receptor (EGFR)/HER2 inhibitor, gefitinib, on this breast tumor line in vitro and in vivo. We characterized the effects of gefitinib on EGFR, HER2, and ErbB-3 phosphorylation by Western blot and determined the effects on downstream signaling through growth, survival, and stress pathways and the effect on proliferation, cell cycle, and apoptosis. Gefitinib treatment diminished phosphorylation of the ErbB-3 > EGFR > HER2/neu and signal transducers and activators of transcriptions in a dose-dependent fashion. Downstream mitogenic signaling through mitogen-activated protein (MAP)/extracellular signal regulated kinase kinase, p44/42 MAP kinase (MAPK) and stress signaling through c-Jun-NH(2)-kinase (JNK) 1 and c-Jun was impaired (1 micromol/L, 4-24 h), leading to cytostasis and cell cycle arrest within 24 h by decreased cyclin D1, cyclin B1, and p(Ser795)Rb and increased p27. Proliferation and colony formation were inhibited at 0.5 and 1 micromol/L, respectively, and correlated with altered gene expression profiles. Diminished survival signaling through Akt, induction of bim, loss of connexin43, and decreased production of vascular endothelial growth factor-D preceded caspase-3 and poly(ADP)ribose polymerase (PARP) cleavage and apoptosis (>50% 2 micromol/L, 48 h). Oral administration of gefitinib was able to prevent the outgrowth of Bam1a tumor cells from palpable lesions, shrink established tumors, eliminate HER2 and HER3 phosphorylation, and decrease MAPK and Akt signaling in vivo. A variant of the Bam1a cell line, IR-5, with acquired ability to grow in 5 micromol/L gefitinib was developed and characterized. IR-5 bears a novel point mutation in the HER2/neu that corresponds to a L726I in the ATP-binding pocket and correlates with a log decrease in sensitivity to gefitinib, increased heterodimerization with EGFR and HER3, and impaired down-regulation. Gene expression profiling of IR-5 showed increased expression of EMP-1, NOTCH-1, FLT-1, PDGFB, and several other genes that may contribute to the resistant phenotype and sustain signaling through MAPK and Akt. This model will be useful in understanding the differences between intrinsic drug sensitivity and acquired resistance in the context of therapeutic strategies that target oncogene addicted diseases.

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Molecular Profile Treatment Approach
Gene Name Source Synonyms Protein Domains Gene Description Gene Role
Therapy Name Drugs Efficacy Evidence Clinical Trials
Drug Name Trade Name Synonyms Drug Classes Drug Description
Gene Variant Impact Protein Effect Variant Description Associated with drug Resistance
ERBB2 L726I missense unknown ERBB2 (HER2) L726I lies within the protein kinase domain of the Erbb2 (Her2) protein (UniProt.org). L726I is associated with resistance to Iressa (gefitinib) and Tykerb (lapatinib) in cell culture (PMID: 17638894, PMID: 18413839), but has not been biochemically characterized and therefore, its effect on Erbb2 (Her2) protein function is unknown (PubMed, Apr 2020). Y
Molecular Profile Indication/Tumor Type Response Type Therapy Name Approval Status Evidence Type Efficacy Evidence References
ERBB2 L726I breast cancer resistant Gefitinib Preclinical Actionable In a preclinical study, an ERBB2 (HER2) L726I mutation was detected in a murine breast cancer cell line that acquired resistance to Iressa (gefitinib) in culture (PMID: 17638894). 17638894