Demonstration of proteinase inhibitors cystatin A, B and C in breast cancer and in cell lines MCF-7 and ZR-75-1.

Polyclonal rabbit antibodies to endogenous natural inhibitors of cysteine proteinases (cystatins) were used for their immunohistochemical demonstration in samples of breast cancers and in two breast cancer derived cell lines (MCF-7 and ZR-75-1). The influence of estrogen stimulation on the expression of these inhibitors was also studied. The results showed that all cystatins tested can be found equally inside carcinomatous cells or in surrounding connective tissue, as well as in both cell lines examined. Further, the expression of inhibitors can be regulated by estrogen, and a certain role of cystatins in the regulation of the mitotic activity and differentiation of mammary cells can be supposed.