Demonstration of cysteine proteinase inhibitors ACPI and NCPI in breast cancer and in cell lines MCF-7 and ZR-75-1.

The samples of breast cancer and cell lines MCF-7 and ZR-75-1 were tested for the occurrence of cysteine proteinase inhibitors ACPI and NCPI. Further, the influence of estradiol on the expression of these inhibitors was examined. Both the tested inhibitors were found in tumor cells and in cell lines. Moreover, the positivity was found also in the connective tissue, especially in the vicinity of dysplastic changes and normal lobules. The expression of both the inhibitors can be regulated by estrogens. The data indicate a possible connection of NCPI expression with the regulation of cell proliferation and ACPI with cellular differentiation. The role of these inhibitors in invasive processes and metastases is not clear so far.