title: Dual-colour CISH is a reliable alternative to FISH for assessment of topoisomerase 2-alpha amplification in breast carcinomas.
abstract: Anthracyclines are among the most powerful antineoplastic drugs available for breast cancer treatment. Although HER2 amplification has been postulated to predict anthracycline benefit, numerous reports have demonstrated that HER2/TOP2A co-amplification is the clinically useful predictive marker of response to anthracyclines. The standard technique to evaluate gene status for target therapy selection is fluorescence in situ hybridization (FISH), but this technique has some disadvantages. Dual-colour chromogenic in situ hybridization (CISH) is an extension of the FISH protocol that allows bright-field microscopy and thus represents a user-friendly alternative to FISH. In order to evaluate whether dual-colour CISH is a reliable alternative to FISH in determining TOP2A gene amplification and to determine the frequency with which TOP2A and HER2 were co-amplified, we analysed 100 invasive breast cancer specimens (70 consecutive and 30 HER2-amplified samples) using tissue microarrays. Thus, a 99 % agreement was found between TOP2A status determined by dual-colour CISH and FISH, as well as a high degree of correlation in TOP2A ratios using both techniques. TOP2A gene amplification was present in 8.6 % of the 70 consecutive samples studied, all of which were HER2-amplified. Co-amplification of TOP2A was observed in 46.5 % of the additional 30 HER2-amplified samples (no TOP2A amplification was seen in non-amplified HER2 samples). We conclude that dual-colour CISH represents an excellent alternative to FISH for determination of TOP2A gene status in invasive breast cancer. Our results showing TOP2A amplification only in HER2-amplified cases also add to the evidence that TOP2A determination should be restricted to those cases.
authors.affiliation: Department of Morphological Sciences, Faculty of Medicine-University Clinical Hospital, University of Santiago de Compostela, 15782, Santiago de Compostela, Spain, tomas.garcia-caballero@usc.es.
authors.forename: Tomás
authors.initials: T
authors.lastname: García-Caballero
authors.forename: Olga
authors.initials: O
authors.lastname: Prieto
authors.forename: Angel
authors.initials: A
authors.lastname: Vázquez-Boquete
authors.forename: Francisco
authors.initials: F
authors.lastname: Gude
authors.forename: Patricia
authors.initials: P
authors.lastname: Viaño
authors.forename: María
authors.initials: M
authors.lastname: Otero
authors.forename: Teresa
authors.initials: T
authors.lastname: Curiel
authors.forename: Beatriz
authors.initials: B
authors.lastname: Fernández-Rodríguez
authors.forename: Concepción
authors.initials: C
authors.lastname: Parrado
authors.forename: Máximo
authors.initials: M
authors.lastname: Fraga
authors.forename: José R
authors.initials: JR
authors.lastname: Antúnez
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000951:Antigens, Neoplasm / Q000235:genetics*; D001943:Breast Neoplasms / Q000175:diagnosis* / Q000235:genetics*; D004250:DNA Topoisomerases, Type II / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics*; D005260:Female; D005784:Gene Amplification; D018628:Gene Dosage; D006801:Humans; D017403:In Situ Hybridization / Q000379:methods*; D017404:In Situ Hybridization, Fluorescence / Q000379:methods; D008875:Middle Aged; D060787:Neoplasm Grading; D000075223:Poly-ADP-Ribose Binding Proteins; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000235:genetics
chemical_list: D000951:Antigens, Neoplasm; D004250:DNA Topoisomerases, Type II; D004268:DNA-Binding Proteins; D000075223:Poly-ADP-Ribose Binding Proteins; D018719:Erb-b2 Receptor Tyrosine Kinases; C000618811:TOP2A protein, human