Flow cytometric analysis of estrogen, progesterone receptor expression andDNA content in formalin-fixed, paraffin-embedded human breast tumors

Flow cytometric analysis of estrogen (ER) and progesterone (PgR) receptor e xpression in archival human breast tumors is relatively difficult. We have used enzyme digestion and microwave antigen retrieval procedures for multip arametric flow cytometric analysis of ER and PgR expression and DNA content in nuclei isolated from formalin-fixed/paraffin-embedded primary breast tu mors. Deparaffinized rehydrated tissue sections treated with pepsin were su bjected to microwave irradiation for unmasking of ER and PgR antigenic site s, Biotinylated ER antibody and streptavidin-fluorescein isothiocyanate (FI TC) were used far ER labeling and PgR antibody with phycoerythrin labeled g oat anti-mouse antibody was used for PgR labeling. Counter staining with pr opidium iodide-RNase was used for determination of cellular DNA content. Ou r results show that enzyme digestion and microwave treatment of formalin-fi xed, paraffin-embedded breast tumors can be successfully used for the multi parametric analysis of nuclear hormone receptor expression and DNA content by flow cytometry, Cytometry (Comm, Clin. Cytometry) 38:61-69, 1999. (C) 19 99 Wiley-Liss, Inc.