Inhibition of growth of human tumor cells in nude mice by a metalloproteinase inhibitor

The effects of a new metalloproteinase inhibitor, BEI6627B [L-N-(N-hydroxy-2-isobutylsuccinynamoyl)-seryl-L-valine, MW: 375.2] isolated from microbial cultures, on human tumor cell growth in nude mice were investigated. BE16627B inhibited metalloproteinases in enzyme assays, as well as gelatinolysis and collagenolysis in cell cultures. BE16627B at 100 μg/ml showed no apparent cytotoxicity to human tumor cells in culture and its LD₅₀ in mice was more than 1,000 mg/kg (i.p.). The effects of BE16627B on the in vivo growth of 1 human tumor cell lines were examined: HT1080 fibrosarcoma, which overproduces metalloproteinases, and HCT116 colon carcinoma, which barely secretes metalloproteinases. When BE16627B was administered to mice at 2 mg/mouse/day by an osmotic pump implanted s.c. for 3 weeks from 1 week after i.v. inoculation of HT1080 cells, the number and size of nodules of HT1080 cells on the lung surface were reduced to 24.3 and 46.4%, respectively, of those of controls, and the increase in lung weight due to tumor-cell growth was inhibited 85.5% without body-weight loss. Moreover, BE16627B inhibited 71.2% of the growth of HT1080 cells inoculated s.c. into mice under the same conditions, but did not significantly inhibit the s.c. growth of HCT116 human colon-carcinoma cells. Thus, BE16627B inhibited metalloproteinase-dependent human tumor-cell growth as well as lung colonization without showing cytotoxicity in nude mice.