title: Novel EGFR mutation-specific antibodies for lung adenocarcinoma: highly specific but not sensitive detection of an E746_A750 deletion in exon 19 and an L858R mutation in exon 21 by immunohistochemistry.
abstract: OBJECTIVE
  Activating mutations in the epidermal growth factor receptor (EGFR) kinase domain are correlated with dramatic clinical responses in non-small cell lung cancer patients treated with EGFR-tyrosine kinase inhibitors (TKIs). The two most common EGFR mutations, representing 85-90% of EGFR mutations, are the E746_A750 deletion in exon 19 and the L858R point mutation in exon 21. We conducted this study to evaluate the suitability of mutation-specific antibodies that can detect E746_A750 deletion and L858R mutant EGFR proteins by immunohistochemistry (IHC).
  
  
  METHODS
  In a cohort of consecutive patients with surgically resected lung adenocarcinomas (n=240), mutant EGFR protein expression was assessed by IHC using specific antibodies (clone SP111 and SP125) to the 2 major forms of EGFR mutations. Immunoreactivity was scored as 0-3, and the results were compared with the EGFR-mutational status.
  
  
  RESULTS
  With a cutoff value of IHC 2+ for SP 111 (anti-EGFR E746_A750 del antibody) and SP 125 (anti-EGFR L858R antibody), both antibodies showed high specificity (99.0% and 89.7%, respectively) and sensitivity (70.6% and 80.4%, respectively). While cases with IHC scores of 3 using these 2 antibodies positively correlated with the EGFR-mutational status, cases with IHC scores lower than 3+ showed variable results regarding EGFR-mutational status.
  
  
  CONCLUSIONS
  Although each antibody showed relatively high specificity, some EGFR-mutant cases were not detected by the mutation-specific antibodies. Various forms of exon 19 deletions, except E746_A750, were rarely detected by the mutant-specific antibody. Therefore, IHC-negative cases require further molecular analysis to confirm the presence of EGFR mutations.
authors.affiliation: Department of Pathology, Seoul National University Bundang Hospital, 300 Gumi-dong, Bundang-gu, Seongnam-si, Gyeonggi 463-707, Republic of Korea; Department of Pathology, Kyungpook National University College of Medicine, 680 Gukchaebosang-ro, Jung-gu, Daegu 700-842, Republic of Korea.
authors.forename: An Na
authors.initials: AN
authors.lastname: Seo
authors.affiliation: Department of Pathology, Kyungpook National University College of Medicine, 680 Gukchaebosang-ro, Jung-gu, Daegu 700-842, Republic of Korea.
authors.forename: Tae-In
authors.initials: TI
authors.lastname: Park
authors.affiliation: Department of Pathology, Seoul National University Bundang Hospital, 300 Gumi-dong, Bundang-gu, Seongnam-si, Gyeonggi 463-707, Republic of Korea; Department of Pathology, Seoul National University College of Medicine, 103 Daehak-ro, Jongno-gu, Seoul 110-799, Republic of Korea.
authors.forename: Yan
authors.initials: Y
authors.lastname: Jin
authors.affiliation: Department of Pathology, Seoul National University Bundang Hospital, 300 Gumi-dong, Bundang-gu, Seongnam-si, Gyeonggi 463-707, Republic of Korea; Department of Pathology, Seoul National University College of Medicine, 103 Daehak-ro, Jongno-gu, Seoul 110-799, Republic of Korea.
authors.forename: Ping-Li
authors.initials: PL
authors.lastname: Sun
authors.affiliation: Department of Pathology, Seoul National University Bundang Hospital, 300 Gumi-dong, Bundang-gu, Seongnam-si, Gyeonggi 463-707, Republic of Korea; Department of Pathology, Seoul National University College of Medicine, 103 Daehak-ro, Jongno-gu, Seoul 110-799, Republic of Korea.
authors.forename: Hyojin
authors.initials: H
authors.lastname: Kim
authors.affiliation: Department of Internal Medicine, Seoul National University Bundang Hospital, 300 Gumi-dong, Bundang-gu, Seongnam-si, Gyeonggi 463-707, Republic of Korea.
authors.forename: Hyun
authors.initials: H
authors.lastname: Chang
authors.affiliation: Department of Pathology, Seoul National University Bundang Hospital, 300 Gumi-dong, Bundang-gu, Seongnam-si, Gyeonggi 463-707, Republic of Korea; Department of Pathology, Seoul National University College of Medicine, 103 Daehak-ro, Jongno-gu, Seoul 110-799, Republic of Korea. Electronic address: chungjh@snu.ac.kr.
authors.forename: Jin-Haeng
authors.initials: JH
authors.lastname: Chung
mesh_terms: D000230:Adenocarcinoma / Q000175:diagnosis* / Q000235:genetics / Q000276:immunology; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000912:Antibodies, Neoplasm / Q000378:metabolism*; D066246:ErbB Receptors / Q000235:genetics / Q000276:immunology; D005091:Exons / Q000235:genetics; D005260:Female; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D008175:Lung Neoplasms / Q000175:diagnosis* / Q000235:genetics / Q000276:immunology; D008297:Male; D008875:Middle Aged; D017354:Point Mutation / Q000235:genetics; D012680:Sensitivity and Specificity; D017384:Sequence Deletion / Q000235:genetics; D046888:Tissue Array Analysis; D055815:Young Adult
chemical_list: D000912:Antibodies, Neoplasm; C512478:EGFR protein, human; D066246:ErbB Receptors
keywords: E746_A750 deletion; EGFR mutations; Immunohistochemistry; L858R mutation; Lung adenocarcinoma; Mutation-specific antibody