c-erbB-2 (Her-2, neu)

Accurate (CB11, CBE1, polyclonal), Becton Dickinson (3B5), Biogenesis (2G2-91, LY369), Biogenex (EGFR), Coulter (3B5), Dako (polyclonal), Lab Vision (9G6.10, L87, N12, N24, N28.6), Novocastra (CB11, CBE1), Oncogene (CNeu), Pharmingen (9G6) and Dako (polyclonal antibodies).

Most antibodies are immunoreactive in fresh-frozen tissue sections as well as in fixed paraffin-embedded sections. HIER enhances immunoreactivity. Enzyme treatment is not necessary.

The c-erbB-2 oncogene was discovered in the 1980s by three different avenues of investigation. The neu oncogene was detected as a mutated transforming gene in neuroblastomas experimentally induced in fetal rats. The c-erbB-2 was a human gene discovered by its homology to the retroviral gene v-erbB, and HER-2 was isolated by screening a human genomic DNA library for homology with v-erbB. When the DNA sequences were determined subsequently, c-erbB-2, HER-2 and neu were found to represent the same gene.
The c-erbB-2 gene is located on human chromosome 17q21 and codes for the c-erbB-2 mRNA (4.6 kb), which translates to the c-erbB-2 protein (p185). The c-erbB-2 oncogene is homologous with, but not identical to, c-erbB-1, which is located on chromosome 7 and encodes for the epidermal growth factor receptor. The c-erbB-2 protein is a normal cell membrane component of all epithelial cells with extracellular, transmembrane and intracellular tyrosine kinase activity (Lupu et al, 1992). Apart from this growth stimulatory function, the molecule plays an important role in the motility of tumor cells by the activity of a motility factor, which acts as a specific ligand for the c-erbB-2 protein. The motility factor induces chemotaxis of c-erbB-2 overexpressing breast cancer cells and may lead to an increased metastatic potential (De Potter, 1994).
c-erbB-2 gene alterations have been reported in diverse human neoplasms and almost exclusively involve amplification of the gene. Amplification involves the repeated duplication of a particular gene sequence, resulting in multiple gene copies within each cell. This results in overexpression of the gene product, as reflected in the levels of mRNA and gene oncoprotein. There is generally good correlation of the c-erbB-2 gene amplification with overexpression (Smith et al, 1994).

c-erbB-2 has been shown to be amplified in about 20-30% of invasive breast carcinomas and various studies have correlated the gene amplification or overexpression with other prognostic variables in breast cancer patients. Although these studies have not provided sufficient information on survival outcome to evaluate the prognostic implications of c-erbB-2 overexpression, almost all have shown a strong correlation with various established adverse factors including large tumor size, unfavorable histologic subtype, high histologic grade, high mitotic index and proliferative activity, positive nodal status, presence of hematogenous spread and aneuploidy (De Potter et al, 1990; Borg et al, 1991; Horiguchi et al, 1994).
c-erbB-2 overexpression is more common in invasive ductal and medullary carcinomas than in lobular, colloid and papillary carcinomas. In intraductal carcinomas, it is almost exclusively seen in large cell, high nuclear grade, estrogen receptor-negative, comedo-type intraductal carcinoma. In contrast, in situ lobular carcinoma seldom shows overexpression of the oncoprotein. Overexpression is more common in invasive tumors associated with an intraductal component than in those without and there is usually concordance between the invasive and intraductal components of an individual tumor.
Despite the universal observation of a strong correlation with various adverse prognostic factors, the conflicting data regarding the prognostic value of c-erbB-2 suggest that overexpression of the oncoprotein may not be a powerful predictor by itself. In any individual patient, it should be employed as part of a multivariate approach to guiding treatment and determining prognosis. Overexpression of c-erbB-2 may also serve as a predictor of response to adjuvant treatment, predicting a poor response to chemotherapy and a lack of response to endocrine therapy on relapse and identifying those patients who are most likely to benefit from high-dose regimens (Muss et al, 1994).
Furthermore, as c-erbB-2 protein has an extracellular domain and tends to be expressed in more aggressive tumors, it is a potential target for immunotherapy.

Occasional reports have noted discrepancies between the demonstration of amplification of the cerbB-2 gene and detection of protein overexpression by immunostaining, but despite this drawback, immunohistochemistry now appears to be the method of choice in most institutions for assessing c-erbB-2 overexpression (Bobrow et al, 1996). Only membrane staining should be accepted as positive staining and we have found the polyclonal antibody from Dako and monoclonal Cneu to be the most sensitive. HIER enhanced staining and although it also produced some increase in cytoplasmic staining, this was not a hindrance to interpretation.

•Bobrow LG, Happerfield LC, Millis RR 1996 Comparison of immunohistological staining with different antibodies to the c-erbB-2 oncoprotein. Applied Immunohistochemistry 4: 128-134.

•Borg A, Baldetorp B, Ferno M et al 1991 ErbB2 amplification in breast cancer with a high rate of proliferation. Oncogene 6: 137-143.

•De Potter CR 1994 The neu-oncogene: more than a prognostic indicator? Human Pathology 25: 1264-1268.

•De Potter CR, Beghin C, Marak AP et al 1990 The neu oncogene protein as a predictive factor for hematogenous metastasis in breast cancer patients. International Journal of Cancer 45:55-58.

•Horiguchi J, Iino Y, Takei H et al 1994 Immunohistochemical study on the expression of c-erbB-2 oncoprotein in breast cancer. Oncology 51:47-51.

•Lupu R, Colomer R, Kannan B, Lippman ME 1992. Characterization of a growth factor that binds exclusively to the erbB-2 receptor and induces cellular responses. Proceedings of the National Academy of Sciences USA 89-2287-2291.

•Muss HB, Thor AD, Berry DA et al 1994 C-erbB-2 expression and response to adjuvant therapy in women with node-positive early breast cancer. New England Journal of Medicine 330: 1260-1266.

•Smith KL, Robbins PD, Dawkin HJS et al 1994 C-erbB-2 amplification in breast cancer: detection in formalin fixed, paraffin-embedded tissue by in situ hybridization. Human Pathology 25:413-418.

Manual of diagnostic antibodies for immunohistology / Anthony S.-Y. Leong, Kumarasen Cooper, F. Joel W.-M. Leong.