Acid and neutral cysteine proteinase inhibitor in normal uterine portio and in squamo-epithelial metaplasia, dysplasias and infiltrative carcinoma of the uterine portio.

Acid cysteine proteinase inhibitor (ACPI) and neutral cysteine proteinase inhibitor (NCPI) were localized in formalin-fixed normal human uterine portio as well as in the squamous cell carcinoma and dysplasias of the uterine portio. The peroxidase-antiperoxidase technique was used. In the squamous epithelium of normal uterine portio, ACPI and NCPI were localized in the cells of the upper and middle layers, mainly in the cytoplasm. In the precursors of cancer, immunoreactivity for ACPI and NCPI declined, and neither of the inhibitors was demonstrable immunohistochemically in the anaplastic squamo-epithelial carcinoma of the uterine portio. Our results suggest that ACPI and NCPI are associated with squamo-epithelial differentiation and that they may also be of significance for the regulation of cysteine proteinase activity in normal tissue and malignant growth.