1980 Volume 32 Issue Supplement Pages S33-S46
MeDBG, a potent synthetic inhibitor o f trypsin, plasmin, kallikrein, thrombin, and C1esterase, strongly inhibited mammary tumorigenesis induced by DMBA in rats. However, no inhibiotry effect of MeDBG was observed when MeDBG was given from the 20th day after DMBA treatment. This suggests that certain proteases may play a key role especially within 20 days after DMBA treatment on DMBA induced rat mammary tumorigenesis.
The activity of histone protease was significantly inhibited at the 3rd and 5th days after DMBA treatment in the MeDBG group, although MeDBG was less effective on histone protease in vitro than in vivo. Moreover, MeDBG had no inhibitory effect on cathepsin D activity. Therefore, MeDBG seems to be more effective in the initiation phase rather than in the promotion phase in DMBA induced rat mammary tumorigenesis.
It is likely that histone protease is mostly distributed in the nuclear fractions. These results indicate that histone protease may play an important role on mammary tumorigenesis induced by DMBA in rats.
