CATHEPSIN-D IMMUNOSTAINING IN PARAFFIN-EMBEDDED BREAST-CANCER CELLS AND MACROPHAGES - CORRELATION WITH CYTOSOLIC ASSAY

High cathepsin D (cath-D) concentration in breast cancer cytosol is as sociated with increased risk of metastasis. To specify the relative co ntribution of the different cells types responsible for cath-D level i n cytosol, we validated semiquantitative cath-D immunoperoxidase stain ing on formalin-fixed, paraffin-embedded sections, using the M1G8 mono clonal antibody, one of the two antibodies of the cytosolic assay. Usi ng computer-aided image analysis, cath-D level in cancer cells was est imated by integrating both staining intensity in each cell and proport ion of stained cells. We confirmed on 41 primary breast cancers a high er expression of cath-D in cancer cells compared with peritumoral mamm ary glands. Cancer cell staining was mostly in lysosomes and for some invasive ductal carcinomas in large vesicles corresponding to phagosom es. Lymphocytes and fibroblasts were not or were only weakly stained. Macrophages also were stained for cath-D, generally on the periphery o f the tumor area. The cytosolic cath-D level was correlated with cath- D expression in cancer cells (r = .76; P = 1 X 10(-4)) rather than wit h the number of macrophages in the tumor (r = .29; P = .09), as determ ined by use of the specific anti-CD68 antibody. There was a significan t increase in the tissue cath-D level in tumors containing large vesic les compared with tumors without large vesicles. This approach provide s a means to separately estimate the prognostic significance of cath-D expression in cancer cells and macrophages when evaluating risk of me tastasis. HUM PATHOL 25:863-871. Copyright (C) 1994 by W.B. Saunders C ompany