Almuth Boecker

Publications (2)14.17 Total impact

• Article: 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.

  Horst Buerger, Jens Packeisen, Almuth Boecker, Nicola Tidow, Christian Kersting, Krzysztof Bielawski, Jorma Isola, Yasushi Yatabe, Kei Nakachi, Werner Boecker, Burkhard Brandt
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  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.
  The Journal of Pathology 05/2004; 203(1):545-50. · 6.32 Impact Factor
• Article: Distinct amplification of an untranslated regulatory sequence in the egfr gene contributes to early steps in breast cancer development.

  Nicola Tidow, Almuth Boecker, Hartmut Schmidt, Konstantin Agelopoulos, Werner Boecker, Horst Buerger, Burkhard Brandt
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  ABSTRACT: Overexpression of the epidermal growth factor receptor (egfr) gene is a common feature in breast cancer. We demonstrated recently that the expression of EGFR in breast cancer strongly correlates with the length of a CA simple sequence repeat within the first 2000 bases in intron 1 of the egfr gene [CA simple sequence repeat (CA-SSR) I; H. Buerger et al., Cancer Res., 60: 854-857, 2000]. Using a standardized semiautomated method of microsatellite analysis for loss of heterozygosity detection, we identified an allelic imbalance (AI) at the egfr locus in 55 of 163 primary breast cancer cases. Fine mapping of the chromosomal region at 7p12-15 around the egfr gene using 10 CA-SSR markers showed that mutations of egfr in breast cancer are frequently restricted to the first intron of egfr. Thereby, the simple sequence repeat CA-SSR I in intron 1 was affected in 84% of the patients with AI. Reverse transcription-PCR analysis of 23 breast cancer tissues with AI excluded the presence of in-frame deletions between exon 2 and exon 7. For additional characterization of the underlying phenomenon leading to the detection of an AI in microsatellite analysis, a quantitative 5'-nuclease assay for the first CA-SSR I in intron 1 was established. In breast cancer cases with AI the presence of amplifications of this sequence was shown. Kaplan-Meier analysis revealed a statistically significant worse prognosis for patients with AI in the cancer tissue at the egfr locus compared with patients without AI. Interestingly, 75% of the patients bearing AI of CA-SSR I in the tumor also showed AI at normal, nontumorous breast tissue. Our data strongly support the assumption that distinct amplifications in intronic sequences of the egfr gene, which enhance the basic transcription activity of the gene, represent one of the first steps in breast carcinogenesis. Furthermore, they point to the presence of prognosis-associated markers for breast cancer already in morphological normal breast tissue.
  Cancer Research 04/2003; 63(6):1172-8. · 7.86 Impact Factor