The selective anticancer activity of the endogenous inhibitor of calcium-activated neutral proteinase. A histological, cytological and chemosensitivity study.

The cytotoxicity of an endogenous inhibitor of calcium-activated neutral proteinase (CANP-I) was evaluated using various mammalian tumor-derived cell lines and human cell cultures. The inhibitor was selectively cytotoxic to human tumor cells from lung, bladder, melanoma and chronic myeloid leukemia tissues, in a dose-dependent manner, and was also cytotoxic to Walker rat tumor cells. The inhibitor was not cytotoxic to normal human, urothelial, fallopian tube, liver and resting white blood cells. Cytological examination of the treated malignant cells revealed cells with vacuolated cytoplasm, pyknotic, hyperchromatic nuclei and membranous, granular haematoxylinophilic extracellular matrix. The use of the inhibitor on urothelial tumor tissues caused great exfoliation of necrotic cells while not affecting normal urothelial tissues. When the inhibitor was tested on mixed cell cultures, consisting of normal and malignant cell clones, a selective cytotoxicity to the malignant cells occurred allowing the normal cells to grow unaffected. Cytogenetic and cytological examination of the remaining cells, after the inhibitor treatment, showed normal diploid karyotype and morphology. The inhibitor was also tested in vivo on Wistar rats bearing Walker tumors. Treatment with 50 Units/100 g i.p. daily for 5 days caused 90% tumor regression and necrosis of metastatic foci in the liver and abdomen, without toxic side effects. The protease inhibitors trypsin-chymotrypsin, aprotinin, leupeptin and E64 were also tested in vitro and showed no anticancer activity. In conclusion, the endogenous inhibitor of CANP selectively killed malignant cells of different chromosomal abnormalities, tissue and species origin; also nuclear vlimata and chemoresistant cells.(ABSTRACT TRUNCATED AT 250 WORDS)