Amplification of HER2 and TOP2A and deletion of TOP2A genes in a series of Taiwanese breast cancer.

BACKGROUND: The prognostic relevance of topoisomerase II alpha (TOP2A) copy number change remains not well established. This study is aimed to investigate the frequency and pattern of TOP2A aberrations; to correlate TOP2A alterations with human epidermal growth factor receptor 2 (HER2) status and clinicopathological parameters, and further to explore prognostic value of TOP2A and HER2 status in breast cancer in Taiwan. METHODS: We analyzed tissue samples from 311 invasive carcinomas in tissue microarrays for TOP2A and HER2 status by fluorescent in situ hybridization. RESULTS: TOP2A copy number change is an infrequent genetic event (9.8% amplification and 2.7% deletion) and is present in both HER2-amplified and nonamplified tumors. TOP2A amplification is statistically associated with age >50 at diagnosis (P = 0.016) and HER2 amplification (P < 0.001). HER2 amplification, but not TOP2A amplification, is a predictor of unfavorable prognosis (P = 0.002). Univariate and multivariate analysis showed that higher histologic grading, positive nodal involvement, and HER2 positivity were associated with poorer overall survival. Cytogenetically, double minutes-type amplification is the predominant pattern for both genes (HER2: 64% and TOP2A: 93.1%). Homogeneous staining region-type signals of both genes are resistant to RNase digestion, supporting that these were not nuclear accumulation of mRNA transcripts. CONCLUSION: Our results demonstrate the prognostic value of tumor grading, nodal involvement, and HER2 status in Taiwanese breast cancer. TOP2A aberrations are an infrequent event independent of HER2 status, and TOP2A amplification carries no prognostic value. The predictive value of TOP2A aberrations in patients of breast cancer taking athracycline-containing treatment in Taiwan remains to be determined in prospectively well-designed clinical trials.

Absence of estrogen receptor alpha (ESR1) gene amplification in a series of breast cancers in Taiwan.

Immunohistochemical expression of ERα, encoded by the ESR1 (estrogen receptor 1) gene located at 6q25.1, is the most important determinant of responsiveness to endocrine therapy in breast cancer. The prevalence and significance of ESR1 amplification in breast cancer remain controversial. We set out to assess ESR1 status and its relevance in breast cancer in Taiwan. We tested tissue samples from 311 invasive carcinomas in a tissue microarray for ESR1 status by fluorescent in situ hybridization (FISH) and chromogenic in situ hybridization (CISH). In order to examine its association with ERα and ESR1 status, HER2 status was determined by FISH. Of the carcinomas, 58.8 % (183/311) was ERα positive. None of the carcinomas showed amplification of ESR1 by either method, whereas 24.1 % (75/311) of the carcinomas harbored HER2 amplification. Of the carcinomas, 9.6 % (26/301) showed ESR1 gain (1.3 ≤ ratio ESR1/chromosome 6 < 2) by FISH and 10 % (24/299) by CISH. FISH and CISH results showed a good correlation (κ-coefficient = 0.786). ESR1 gain by FISH and CISH was significantly associated with high-grade (P = 0.0294 and 0.0417, respectively) but not with ERα expression, HER2 status, or overall survival. ERα positivity was significantly associated with better overall survival (P = 0.039). HER2 amplification was significantly related with poor overall survival (P = 0.002). Our data confirm that in breast cancer, HER2 amplification is a frequent genetic aberration and a negative prognostic factor, and show that ESR1 amplification is not a key genetic abnormality in the tumorigenesis of breast cancer in Taiwan.

Dual-colour chromogenic in-situ hybridization is a potential alternative to fluorescence in-situ hybridization in HER2 testing.

AIM: Dual-colour chromogenic in-situ hybridization (dc-CISH) is an emerging methodology for characterizing genomic alterations. This study was aimed at evaluating the performance of a dc-CISH kit (ZytoVision) in determining human epidermal growth factor receptor 2 (HER2) status in breast cancer. METHODS AND RESULTS: Two hundred and twenty-eight invasive breast carcinomas arranged in tissue microarrays were analysed in parallel with dc-CISH, fluorescence in-situ hybridization (FISH), and immunohistochemistry. Of 227 tumours with available FISH and dc-CISH results, HER2 amplification and non-amplification were detected in 49 (21.6%) and 178 (78.4%) tumours, respectively, by both assays. The concordance between dc-CISH and FISH results showed 100% agreement (κ-coefficient=1.00). Immunohistochemically, 162 (71%), 25 (11.0%) and 41 (18%) tumours were scored 0/1+, 2+, and 3+, respectively. The corresponding results with both FISH and dc-CISH demonstrated HER2 amplification in two (3.2%), nine (36%) and 38 (93%) tumours, respectively. Complete consensus among these three methods was observed in 197 cases, representing 98% of all 3+ and 0/1+ tumours (κ-coefficient=0.92). Confirmatory testing of 25 2+ tumours showed complete consensus between FISH and dc-CISH. CONCLUSIONS: dc-CISH is a promising alternative to FISH in HER2 testing, and the single-institute incidence of HER2 amplification in breast cancer in Taiwan is 21.2%.