Effects of an antibiotic protease inhibitor, actinonin on the growth within collagen gels of non-metastatic and metastatic mouse mammary tumors of the same origin

Of five autonomous sublines established independently from the transplantable hormone-dependent mouse mammary tumor, TPDMT-4, three but not two acquired metastatic potential. In in vitro culture using collagen gels, actinonin, an antibiotic protease inhibitor exerted a stronger growth-inhibiting effect on the metastatic than on the parent and non-metastatic tumors. Zymographic analysis demonstrated the active forms of gelatinases in the metastatic but not in the non-metastatic sublines and the complete inhibition of the enzyme activities by actinonin. Gelatinases/type IV collagenases might play an important role in tumor progression towards metastatic phenotype and actinonin may suppress tumor growth through inhibiting collagenase.