A flow cytometric study of c-erbB-3 expression in breast cancer

In order to assess the specificity of biotinylated anti-c-erbB-3 antibody, screening was performed on a series of tumour cell lines and lymphocytes. Staining was found to be consistent, with good reproducibility. Twenty-nine consecutive breast cancer samples were obtained from women treated with tamoxifen and undergoing elective mastectomy. Twenty-eight invasive ductal carcinomas and 1 DCIS were stained for c-erbB-3 expression: 2 were grade I (Bloom and Richardson), 15 grade II, and 11 grade III tumours, 1 being unclassified; 16 were axillary node positive and 10 node negative; in 2 cases no nodes were sampled. Tumours examined by flow cytometry were stained with cytokeratin FITC antibody and the cytokeratin-positive population gated. Using Mann-Whitney analysis no association was seen between c-erbB-3 expression and Bloom and Richardson grade or axillary node status. In the tumour samples c-erbB-3 expression was found to show an association with EGF-R (P = 0.021 r(2) = 0.16), PgR (P = 0.02, r(2) = 0.16), c-myc (P <0.0001, P = 0.5), c-jun (P = 0.001, r(2) = 0.4) and c-fos (P = 0.001, r(2) = 0.5) but not with c-erbB-2 (P = 0.2, r(2) = 0.06), ER (P = 0.4, r(2) = 0.02) or p53 1801 (P = 0.05, r(2) = 0.2). Expression of c-erbB-3 may not be an independent marker of prognosis, but it is associated with other markers of poor prognosis and early cellular events linked with aberrant growth and differentiation.