HER-2/neu oncogene amplification and overexpression of breast cancer tissue has been correlated with poor prognosis in women with both node-positive and node-negative disease. However, several studies have not confirmed this association. Review of these studies reveals the presence of considerable methodological variability including differences in study size, follow-up time, techniques and reagents. The majority of papers with clinical follow-up information are immunohistochemical studies using archival, paraffin-embedded breast cancers, and a variety of HER-2/neu antibodies have been used in these studies. Very little information, however, is available about the ability of the antibodies to detect overexpression following tissue processing for paraffin-embedding. Therefore, a series of antibodies, reported in the literature or commercially available, were evaluated to assess their sensitivity and specificity as immunohistochemical reagents. Paraffin-embedded samples of 187 breast cancers, previously characterized as frozen specimens for HER-2/neu amplification by Southern blot and for overexpression by Northern blot, Western blot, and immunohistochemistry, were used. Two multitumor paraffin-embedded tissue blocks were prepared from the previously analyzed breast cancers as a panel of cases to test a series of previously studied and/or commercially available anti-HER-2/neu antibodies. Immunohistochemical staining results obtained with 7 polyclonal and 21 monoclonal antibodies in sections from paraffin-embedded blocks of these breast cancers were compared. The ability of these antibodies to detect overexpression was extremely variable, providing an important explanation for the variable overexpression rate reported in the literature.
Supported in part by Grants CA48780, CA32737, CA36827, and CA50589 from the National Cancer Institute; Grant N01-HD-3-3175 from the National Institute of Child Health and Human Development; Grant IN-21-29/003 and PDT-411 from the American Cancer Society; the Revlon/UCLA Women's Cancer Research Program; and the Molecular Core Laboratory Facilities of the General Clinical Research Centers (National Institutes of Health National Center for Research Resources of the General Clinical Research Centers MO1 RR-43). D. J. S. has a Faculty Research Award from the American Cancer Society.