Lal Priti, Salazar Paulo A, Ladanyi Marc, Chen Beiyun
Department of Pathology, Memorial Sloan-Kettering Cancer Center, New York, New York 10021, USA.
J Mol Diagn. 2003 Aug;5(3):155-9. doi: 10.1016/S1525-1578(10)60467-9.
Her-2/neu, a proto-oncogene located on chromosome 17, is an important biomarker in breast carcinoma. Immunohistochemistry (IHC) is currently the most widely used method for assessing Her-2/neu status. Some IHC-positive cases do not show Her-2/neu gene amplification by fluorescence in situ hybridization (FISH). It has been suggested that some of these IHC "false positive" results may in part be due to increased copy number of chromosome 17 resulting in increased Her-2/neu protein expression. We analyzed IHC and FISH data from 561 cases of invasive breast carcinoma to test this hypothesis. IHC and FISH for Her-2/neu were performed on formalin-fixed, paraffin-embedded sections of 561 invasive breast carcinomas. The IHC results were interpreted as 0, 1+, 2+, or 3+ according to the manufacturer's recommended criteria. The FISH results were expressed as a ratio of Her-2/neu/chromosome 17 and were interpreted as positive (> = 2.0) or negative (<2.0) for gene amplification according to the manufacturer's recommended scoring system. We found that in IHC 3+/FISH-negative cases (n = 15) both the average chromosome 17 copy number and the average Her-2/neu copy number were significantly higher than that in IHC (0 to 2+)/FISH-negative cases (n = 411) (2.45 vs. 1.68; P < 0.0001, and 3.19 vs. 1.95; P < 0.0001, respectively). In contrast, the IHC 2+/FISH-negative cases did not exhibit a significantly increased number of chromosome 17 compared to IHC 0 to 1+ cases. In addition, the average copy number of chromosome 17 in FISH-positive cases (n = 135) was significantly higher than that in FISH-negative cases (n = 426) (2.27 vs. 1.70; P < 0.0001), indicating a general association of increased chromosome 17 copy number with Her-2/neu gene amplification. Thus, our data suggest that IHC 3+ immunostaining without scorable gene amplification may indeed be, at least in some cases, the result of increased Her-2/neu protein expression secondary to an increased copy number of chromosome 17, associated with an increased total number of Her-2/neu gene copies per tumor cell.
Her-2/neu是一种位于17号染色体上的原癌基因，是乳腺癌中的重要生物标志物。免疫组织化学（IHC）是目前评估Her-2/neu状态最广泛使用的方法。一些免疫组化阳性病例通过荧光原位杂交（FISH）未显示Her-2/neu基因扩增。有人提出，这些免疫组化“假阳性”结果中的一些可能部分是由于17号染色体拷贝数增加导致Her-2/neu蛋白表达增加。我们分析了561例浸润性乳腺癌的免疫组化和FISH数据以验证这一假设。对561例浸润性乳腺癌的福尔马林固定、石蜡包埋切片进行了Her-2/neu的免疫组化和FISH检测。根据制造商推荐的标准，免疫组化结果被解释为0、1+、2+或3+。FISH结果以Her-2/neu/17号染色体的比率表示，并根据制造商推荐的评分系统被解释为基因扩增阳性（>=2.0）或阴性（<2.0）。我们发现，在免疫组化3+/FISH阴性病例（n = 15）中，17号染色体平均拷贝数和Her-2/neu平均拷贝数均显著高于免疫组化（0至2+）/FISH阴性病例（n = 411）（分别为2.45对1.68；P < 0.0001，以及3.19对1.95；P < 0.0001）。相比之下，免疫组化2+/FISH阴性病例与免疫组化0至1+病例相比，17号染色体数量没有显著增加。此外，FISH阳性病例（n = 135）中17号染色体的平均拷贝数显著高于FISH阴性病例（n = 426）（2.27对1.70；P < 0.0001），表明17号染色体拷贝数增加与Her-2/neu基因扩增普遍相关。因此，我们的数据表明，无可评分基因扩增的免疫组化3+染色在至少某些情况下，可能确实是由于17号染色体拷贝数增加继发Her-2/neu蛋白表达增加的结果，与每个肿瘤细胞中Her-2/neu基因拷贝总数增加有关。
