A FLOW CYTOMETRIC STUDY OF C-ERBB-3 EXPRESSION IN BREAST-CANCER

In order to assess the specificity of biotinylated anti-c-erbB-3 antib ody, screening was performed on a series of tumour cell lines and lymp hocytes. Staining was found to be consistent, with good reproducibilit y. Twenty-nine consecutive breast cancer samples were obtained from wo men 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 positi ve and 10 node negative; in 2 cases no nodes were sampled. Tumours exa mined by flow cytometry were stained with cytokeratin FITC antibody an d the cytokeratin-positive population gated. Using Mann-Whitney analys is no association was seen between c-erbB-3 expression and Bloom and R ichardson 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 p5 3 1801 (P = 0.05, r(2) = 0.2). Expression of c-erbB-3 may not be an in dependent marker of prognosis, but it is associated with other markers of poor prognosis and early cellular events linked with aberrant grow th and differentiation.