Bose S, Mohammed M, Shintaku P, Rao P N
UCLA School of Medicine, Department of Pathology and Lab Medicine, Los Angeles, CA 90095-1763, USA.
Breast J. 2001 Sep-Oct;7(5):337-44. doi: 10.1046/j.1524-4741.2001.21018.x.
Overexpression of the Her-2/neu (HER2) oncogene is known to confer important prognostic and predictive value to patients with breast cancer. Controversy exists as to the best method for its determination caused primarily by the variable sensitivities of the different antibodies and interobserver differences, particularly in the group of breast cancers with borderline levels of expression of the protein product. This study was therefore designed to determine the status of the HER2 gene amplification in a group of breast carcinomas with low levels of overexpression. After an initial validation of our procedures, a series of 52 consecutive cases of formalin-fixed, paraffin-embedded breast cancers with low levels of overexpression and a series of 22 cases with no expression by immunohistochemistry were analyzed by fluorescence in situ hybridization (FISH), and the results correlated statistically. Amplification of the HER2 gene was observed in 16% of equivocal to weakly positive cases. Those that were amplified showed low levels of amplification with ratios less than 4.5 and a characteristic scattered pattern of distribution of HER2 signals in the FISH assay. In addition, heterogeneity was noted in two cases in the amplification of the HER2 gene within the same tumor samples with pockets of amplified tumor cells amidst nonamplified tumor cells. In cases without amplification, a statistically significant number showed chromosome 17 polysomy. In conclusion, equivocal to low levels of HER2 overexpression in breast cancers are associated, in the majority of cases, with chromosome 17 polysomy and a corresponding increase in the HER2 gene numbers. True gene amplification is present in only a minority of cases. FISH analysis should be used for confirmation of gene amplification. Prior screening and selection of appropriate immunohistochemistry-positive areas for FISH analysis may prove beneficial.
已知Her-2/neu（HER2）癌基因的过表达对乳腺癌患者具有重要的预后和预测价值。对于其最佳检测方法存在争议，主要原因是不同抗体的敏感性不同以及观察者之间存在差异，特别是在蛋白质产物表达水平处于临界值的乳腺癌组中。因此，本研究旨在确定一组低水平过表达的乳腺癌中HER2基因扩增的状态。在对我们的程序进行初步验证后，通过荧光原位杂交（FISH）分析了一系列52例福尔马林固定、石蜡包埋的低水平过表达乳腺癌连续病例以及一系列22例免疫组化无表达的病例，并对结果进行了统计学关联分析。在16%的可疑至弱阳性病例中观察到HER2基因扩增。那些扩增的病例显示扩增水平较低，比率小于4.5，并且在FISH检测中HER2信号呈特征性的散在分布模式。此外，在同一肿瘤样本中，HER2基因扩增存在异质性，在未扩增的肿瘤细胞中有扩增的肿瘤细胞簇。在无扩增的病例中，有统计学意义的数量显示17号染色体多体性。总之，在大多数情况下，乳腺癌中可疑至低水平的HER2过表达与17号染色体多体性以及相应的HER2基因数量增加有关。真正的基因扩增仅存在于少数病例中。FISH分析应用于确认基因扩增。在进行FISH分析之前，对合适的免疫组化阳性区域进行预先筛选和选择可能是有益的。
