title: Quantitation of p95HER2 in paraffin sections by using a p95-specific antibody and correlation with outcome in a cohort of trastuzumab-treated breast cancer patients.
abstract: OBJECTIVE
  p95HER2 is an NH(2)-terminally truncated form of HER2 that lacks the trastuzumab binding site and is therefore thought to confer resistance to trastuzumab treatment. In this report, we introduce a new antibody that has enabled the first direct quantitative measurement of p95HER2 in formalin-fixed paraffin-embedded (FFPE) breast cancer tissues. We sought to show that quantitative p95HER2 levels would correlate with outcome in trastuzumab-treated HER2-positive metastatic breast cancer.
  
  
  METHODS
  The novel p95HER2 antibody used here was characterized for sensitivity, specificity, and selectivity over full-length HER2. Quantitative p95HER2 levels were measured in 93 metastatic breast tumors using a VeraTag FFPE assay to determine the correlation of p95HER2 levels with outcomes.
  
  
  RESULTS
  Within a cohort of trastuzumab-treated metastatic breast cancer patients, high levels of p95HER2 were found to correlate with shorter progression-free survival [hazard ratio (HR), 1.9; P = 0.017] and overall survival (HR, 2.2; P = 0.012) in patients with tumors selected to be HER2 positive by the VeraTag HER2 assay. For those with tumors found to be fluorescence in situ hybridization positive, elevated p95HER2 correlated similarly with shorter progression-free survival (HR, 1.8; P = 0.022) and overall survival (HR, 2.2; P = 0.009).
  
  
  CONCLUSIONS
  We have successfully generated an antibody that can specifically detect p95HER2, and developed an assay to quantify expression in FFPE tumor specimens. Using this novel assay, we have identified a group of HER2-positive patients expressing p95HER2 that have a worse outcome while on trastuzumab. As p95HER2 retains sensitivity to kinase inhibitors, measurement of p95HER2 in breast tumor sections may be useful in guiding treatment for patients with HER2-positive breast cancer.
authors.affiliation: Diadexus, South San Francisco, CA, USA.
authors.forename: Jeff
authors.initials: J
authors.lastname: Sperinde
authors.forename: Xueguang
authors.initials: X
authors.lastname: Jin
authors.forename: Jayee
authors.initials: J
authors.lastname: Banerjee
authors.forename: Elicia
authors.initials: E
authors.lastname: Penuel
authors.forename: Anasuya
authors.initials: A
authors.lastname: Saha
authors.forename: Gundo
authors.initials: G
authors.lastname: Diedrich
authors.forename: Weidong
authors.initials: W
authors.lastname: Huang
authors.forename: Kim
authors.initials: K
authors.lastname: Leitzel
authors.forename: Jodi
authors.initials: J
authors.lastname: Weidler
authors.forename: Suhail M
authors.initials: SM
authors.lastname: Ali
authors.forename: Eva-Maria
authors.initials: EM
authors.lastname: Fuchs
authors.forename: Christian F
authors.initials: CF
authors.lastname: Singer
authors.forename: Wolfgang J
authors.initials: WJ
authors.lastname: Köstler
authors.forename: Michael
authors.initials: M
authors.lastname: Bates
authors.forename: Gordon
authors.initials: G
authors.lastname: Parry
authors.forename: John
authors.initials: J
authors.lastname: Winslow
authors.forename: Allan
authors.initials: A
authors.lastname: Lipton
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology / Q000627:therapeutic use; D061067:Antibodies, Monoclonal, Humanized; D000918:Antibody Specificity; D000970:Antineoplastic Agents / Q000627:therapeutic use; D014408:Biomarkers, Tumor / Q000032:analysis; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000276:immunology / Q000378:metabolism* / Q000473:pathology; D045744:Cell Line, Tumor; D002469:Cell Separation; D015331:Cohort Studies; D018572:Disease-Free Survival; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005434:Flow Cytometry; D005557:Formaldehyde; D006801:Humans; D007150:Immunohistochemistry; D017404:In Situ Hybridization, Fluorescence; D053208:Kaplan-Meier Estimate; D016612:Paraffin Embedding; D010446:Peptide Fragments / Q000032:analysis / Q000276:immunology; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000096:biosynthesis* / Q000276:immunology; D012680:Sensitivity and Specificity; D016707:Tissue Fixation; D000068878:Trastuzumab; D016896:Treatment Outcome
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents; D014408:Biomarkers, Tumor; D005557:Formaldehyde; D010446:Peptide Fragments; D018719:Erb-b2 Receptor Tyrosine Kinases; D000068878:Trastuzumab