Department of Pathology, Institute of Surgical Pathology, University Hospital Zurich, Schmelzbergstrasse 12, 8091 Zurich, Switzerland.
Breast Cancer Res Treat. 2012 Jun;133(3):929-35. doi: 10.1007/s10549-011-1873-8. Epub 2011 Nov 15.
The HER2 amplicon on chromosome 17q is variable in size and occasionally includes Topoisomerase 2A (TOP2A) at 17q21-22. It has been suggested that TOP2 co-amplification, not HER2 amplification on chromosome 17q11.2-12, is a useful predictive marker of response to anthracycline-based chemotherapy in breast cancer patients. Given the significant toxicities of anthracyclines, the detection methods of TOP2A gene amplifications have to be standardized. We determined TOP2A gene alterations using two different fluorescence in situ hybridization (FISH) DNA probes. HER2 amplifications were identified with the PathVysion probe. TOP2A status of 42 HER2 amplified breast cancers was tested by FISH with PathVysion covering 160 kb and DAKO pharm DX covering 228 kb of the TOP2A amplicon. TOP2A protein expression was tested by immunohistochemistry. Multiplex-ligation dependent probe amplification (MLPA) was performed retrospectively in cases showing discrepancies. TOP2A was amplified in 15 of 42 cases (35%) with DAKO pharm DX and in 11 of 42 cases (26%) with PathVysion. In all four discrepant cases, MLPA showed no TOP2A amplification, but instead amplification of an upstream region including HER2. TOP2A was deleted in the same seven of 42 carcinomas (17%) with both probes. TOP2A protein expression was detected in all 42 tumours (100%) with high intratumoral heterogeneity. TOP2A amplification rate depends on the length of the hybridized probes for the TOP2A locus. Because TOP2A, not HER2, is a target of anthracyclines, non-overlapping DNA probes should be used to evaluate any associations between such alterations and response to anthracycline-based chemotherapy.
17 号染色体上的 HER2 扩增子大小可变，偶尔包括 17q21-22 上的拓扑异构酶 2A（TOP2A）。有人提出，TOP2 共扩增，而不是 17q11.2-12 上的 HER2 扩增，是乳腺癌患者对蒽环类化疗反应的有用预测标志物。鉴于蒽环类药物的毒性很大，必须标准化 TOP2A 基因扩增的检测方法。我们使用两种不同的荧光原位杂交（FISH）DNA 探针来确定 TOP2A 基因改变。使用 PathVysion 探针鉴定 HER2 扩增。通过 FISH 用 PathVysion 覆盖 TOP2A 扩增子的 160 kb 和 DAKO pharm DX 覆盖 228 kb 测试 42 例 HER2 扩增乳腺癌的 TOP2A 状态。通过免疫组织化学测试 TOP2A 蛋白表达。在显示差异的情况下，回顾性进行多重连接依赖性探针扩增（MLPA）。使用 DAKO pharm DX，TOP2A 在 42 例中的 15 例（35%）中扩增，在 42 例中的 11 例（26%）中扩增。在所有四个不一致的病例中，MLPA 显示没有 TOP2A 扩增，而是包括 HER2 的上游区域扩增。在 42 例中的 7 例（17%）中，两种探针均检测到 TOP2A 缺失。两种探针均检测到 42 例肿瘤中的 TOP2A 蛋白表达（100%），肿瘤内异质性高。TOP2A 扩增率取决于用于 TOP2A 基因座的杂交探针的长度。由于 TOP2A 而不是 HER2 是蒽环类药物的靶点，因此应使用非重叠的 DNA 探针来评估这些改变与蒽环类化疗反应之间的任何关联。
