title: An oncogenic isoform of HER2 associated with locally disseminated breast cancer and trastuzumab resistance.
abstract: The HER2-targeted therapy trastuzumab is widely used for the treatment of patients with metastatic breast tumors overexpressing HER2. However, an objective response is observed in only 12% to 24% of patients treated with trastuzumab as a single agent and initial responders regress in <6 months (1-3). The reason for the clinical failure of trastuzumab in this setting remains unclear. Here we show that local lymph node-positive disease progression in 89% of breast cancer patients with HER2-positive tumors involves the HER2 oncogenic variant HER2Delta16. We further show that ectopic expression of HER2Delta16, but not wild-type HER2, promotes receptor dimerization, cell invasion, and trastuzumab resistance of NIH3T3 and MCF-7 tumor cell lines. The potentiated metastatic and oncogenic properties of HER2Delta16 were mediated through direct coupling of HER2Delta16 to Src kinase. Cotargeting of HER2Delta16 and Src kinase with the single-agent tyrosine kinase inhibitor dasatinib resulted in Src inactivation, destabilization of HER2Delta16, and suppressed tumorigenicity. Activated Src kinase was also observed in 44% of HER2Delta16-expressing breast carcinomas underscoring the potential clinical implications of coupled HER2Delta16 and Src signaling. Our results suggest that HER2Delta16 expression is an important genetic event driving trastuzumab-refractory breast cancer. We propose that successful targeted therapeutics for intervention of aggressive HER2-positive breast cancers will require a strategy to suppress HER2Delta16 oncogenic signaling. One possibility involves a therapeutic strategy employing single-agent tyrosine kinase inhibitors to disengage the functionally coupled oncogenic HER2Delta16 and Src tyrosine kinase pathways.
authors: 1Department of Pathology, University of Colorado-Denver, Aurora, Colorado, USA.
authors: Doyel
authors: D
authors: Mitra
authors: Michael J
authors: MJ
authors: Brumlik
authors: Stella U
authors: SU
authors: Okamgba
authors: Yun
authors: Y
authors: Zhu
authors: Tamika T
authors: TT
authors: Duplessis
authors: Jenny G
authors: JG
authors: Parvani
authors: Samuel M
authors: SM
authors: Lesko
authors: Edi
authors: E
authors: Brogi
authors: Frank E
authors: FE
authors: Jones
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology* / Q000627:therapeutic use; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents / Q000494:pharmacology* / Q000627:therapeutic use; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000201:enzymology / Q000235:genetics; D045744:Cell Line, Tumor; D019008:Drug Resistance, Neoplasm; D005260:Female; D005455:Fluorescent Antibody Technique; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D051379:Mice; D041681:NIH 3T3 Cells; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000235:genetics* / Q000378:metabolism*; D015398:Signal Transduction; D014162:Transfection; D000068878:Trastuzumab
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents; D020033:Protein Isoforms; D018719:Erb-b2 Receptor Tyrosine Kinases; D000068878:Trastuzumab; C508053:ERBB2 protein, human