EXAMINATION OF MULTIDRUG-RESISTANCE IN CELL-LINES AND PRIMARY BREAST-TUMORS BY FLOW-CYTOMETRY

The aim of this study was to measure multidrug resistance (MDR) by flo w cytometry and quantify the expression of beta-glycoprotein (using an tibody) glutathione transferase (using alpha-GSTpi antibody) in alpha- JSB-1 and alpha-GSTpi of a series of cell lines and primary breast can cers, and to assess the relationship between these MDR proteins and a selection of oncogene and prognostic markers in breast cancer. Flow cy tometry was performed using permeabilised cells stained with fluoresce nt antibodies using well-established methods. Antibody staining was co nfirmed for JSB1, but not GSTpi by use of known positive and negative controls. No correlation was seen when comparing the number of molecul es of alpha-JSB-1 with alpha-GSTpi (P = 0.1, r(2) = 0.4, n = 14) using a selection of cell lines. Examination of 45 breast tumours for expre ssion of JSB-1 and GSTpi revealed a significant association between th ese two antibodies (P < 0.00001, r(2) = 0.5, n = 45). On examining the breast tumours, alpha-JSB-1 showed a positive association with c-erbB -2 (P = 0.003), c-myc (P = 0.0004) and c-jun (P = 0.02) but not ER or EGF-R expression. alpha-GSTpi showed a positive association with c-erb B-2 (P = 0.03) and c-myc (P = 0.0004) but not ER, EGF-R or c-jun. Flow cytometric MDR levels were not related to tumour grade or axillary no de status. In solid tumours, a relationship between the two antibodies used has been clearly demonstrated, however, specificity of alpha-GST pi is questioned. Both antibodies show an association with c-erbB-2, w hich is associated with poor prognosis and with c-myc which is involve d in cell cycling and differentiation. Monitoring MDR markers (Pgp) us ing this methodology may be useful for evaluation of prognosis in brea st cancer. Copyright (C) 1996 Elsevier Science Ltd