title: Allelic length of a CA dinucleotide repeat in the egfr gene correlates with the frequency of amplifications of this sequence--first results of an inter-ethnic breast cancer study.
abstract: Overexpression of the epidermal growth factor receptor (EGFR) is a common finding in invasive breast cancer and represents a potential target for new treatment options. However, little is known about the parameters that might indicate a potential clinical response for these anti-EGFR-based therapies. In order to gain further insights into the interplay between the length of a CA-SSR I repeat in intron 1 of egfr, copy numbers of this untranslated regulatory sequence, and protein expression, the present study investigated breast cancers from Germans and Japanese patients by microsatellite analysis, quantitative 5' nuclease assay by egfr enzyme-linked immunosorbent assay (ELISA), and comparative genomic hybridization (CGH). Japanese breast cancer patients displayed significantly longer alleles for the CA-SSR I repeat (p < 0.001), associated with significantly lower EGFR expression (mean 65 versus 36 fmol/mg membrane protein). Allelic imbalance (restricted to CA-SSR I) was observed in 55% of the informative Japanese breast cancers compared with only 34% of the German breast cancer reference group. Using a quantitative 5' nuclease assay for egfr, a significantly higher percentage of Japanese breast cancer patients revealed amplifications of the CA-SSR I repeat (p < 0.01). Japanese patients with these amplifications were characterized by a significantly higher EGFR content compared with the German breast cancer patients (p < 0.05). These data show, on the one hand, that the correlation of EGFR overexpression and an inherited CA repeat polymorphism within intron 1 of egfr is a general finding in breast cancer, as has been shown previously. On the other hand, the data demonstrate clearly for the first time an interaction between the length of a polymorphism in intron 1 of egfr as an inherited genetic factor and the frequency of egfr amplification, as an acquired genetic factor, both factors contributing to EGFR overexpression in breast cancer. This new knowledge about mechanisms of regulation of EGFR expression might serve as an additional basis for evaluating anti-EGFR-based therapies.
authors.affiliation: Institute of Pathology, University of Münster, Albert-Schweitzer-Strasse 33, 48139 Münster, Germany. burgerh@uni-muenster.de
authors.forename: Horst
authors.initials: H
authors.lastname: Buerger
authors.forename: Jens
authors.initials: J
authors.lastname: Packeisen
authors.forename: Almuth
authors.initials: A
authors.lastname: Boecker
authors.forename: Nicola
authors.initials: N
authors.lastname: Tidow
authors.forename: Christian
authors.initials: C
authors.lastname: Kersting
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Bielawski
authors.forename: Jorma
authors.initials: J
authors.lastname: Isola
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Yatabe
authors.forename: Kei
authors.initials: K
authors.lastname: Nakachi
authors.forename: Werner
authors.initials: W
authors.lastname: Boecker
authors.forename: Burkhard
authors.initials: B
authors.lastname: Brandt
mesh_terms: D000483:Alleles; D001943:Breast Neoplasms / Q000208:ethnology / Q000235:genetics*; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D005260:Female; D005784:Gene Amplification / Q000235:genetics*; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics; D018773:Genes, erbB-1 / Q000235:genetics*; D005858:Germany; D006801:Humans; D007438:Introns / Q000235:genetics; D007564:Japan; D019656:Loss of Heterozygosity / Q000235:genetics; D018895:Microsatellite Repeats / Q000235:genetics*; D009693:Nucleic Acid Hybridization / Q000379:methods; D016133:Polymerase Chain Reaction / Q000379:methods; D011110:Polymorphism, Genetic / Q000235:genetics