Analysis of c‐erbB‐2 protein expression in conjunction with DNA content using multiparameter flow cytometry

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Abstract
Breast cancer is a leading cause of cancer death among women. Factors useful for determining the prognosis of breast cancer include axillary lymph node involvement, tumor size, hormonal receptor status, nuclear grade, and relative DNA content. The c‐erbB‐2 protooncogene is amplified in 10–40% of primary breast tumors, as well as in breast cancer cell lines; where it is amplified there is increased expression of its product. We have investigated the DNA content and c‐erbB‐2 protein expression in tumor cell lines and in breast cancer patient specimens by multiparameter flow cytometry. The study was enabled by the discovery that both cellular integrity and c‐erbB‐2 antigen reactivity were preserved in cells and tissues following fixation in 70% ethanol. We demonstrate that flow cytometric analysis of c‐erbB‐2 expression in populations of ethanol‐fixed tumor cells is a reliable and sensitive quantitative method that correlates well with previously documented semiquantitative techniques. This is a feasible method for analyzing archived clinical samples, and further allows correlations between c‐erbB‐2 levels and other cellular parameters. Additionally, this method detects abnormal populations not identified by DNA content analysis alone. Further studies utilizing this approach are necessary to evaluate the prognostic value of this oncoprotein in human breast cancer.