Flow Cytometric Analysis of BRCA1 Protein in Sporadic Breast Cancer

Lee, Seung Moo; Sons, Kyung Soon; Lee, Hee Dae

Abstract

PURPOSE
To study the subcellular localization with flow-cytometry and to evaluate their prognostic values.
MATERIALS AND METHODS
The breast tissues were obtained from 28 patients with breast cancer and 6 patients with benign mass. The expression of BRCA1 protein was analyzed with the flow cytometry(Coulter Epics-XL, Coulter Corps, FL, USA) using the monoclonal antibody(BRCA1(Ab-1), Calbiochem, MA, USA) before and after nuclear and cytoplasmic permeabilization in association with DNA ploidy analysis. Several BRCA1 protein indices were derived including 95 percentile channel fluorescence(95% CF) and mean channel fluorescence(MCF) and percentage of BRCA 1 positive cell population arbitarily defined as those above 0.12 channel fluorescence.
RESULTS
Cytoplasmic 95% CF were higher in breast cancer(n=28, 0.65+/-0.26) than in benign mass(n=6, 0.40+/-0.13, p=0.0211). Cytoplasmic BRCAl positive cell percentages were significantly higher in malignant tissues(24.0+/-10.3) than in benign mass(43.4+/-15.2, p=0.0059). Cytoplasmic BRCA1 positive cell percentages were significantly different according to the stages(stage I vs II, 32.6+/-9.8 vs 48.3+/-18.8, p=0.048, stage I vs stage III, 32.6+/-9.8 vs 47.0+/-10.9, p=0.010). The BRCA1 protein indices were not significantly correlated with histologic grades and DNA indices(aneuploidy, S phase and proliferation fractions).
CONCLUSIONS
Flowcytometric assay offers an alternative approach to evaluating BRCA1 protein status of breast cancer tissue and detection of cytoplasmic BRCA1 protein by this method may help to understand the role of BRCA1 in breast cancer cell biology. The further study on cytoplasmic or nuclear BRCA1 protein in association with clinical therapeutic response or prognosis seems to be warranted.