Variant cathepsin B activity secreted from human pancreatic cancer cell lines into protein-free chemically defined medium.

Cathepsin B activity was found in serum-free spent media of human pancreatic cancer cell lines, Panc-1 and MiaPaca. Cathepsin B activity was partially purified by gel filtration on TSK G3000SW, Con-A Sepharose chromatography, Phenyl-Superose column chromatography, and Mono S column chromatography. The optimal pH of cathepsin B was 7.4, and the activity was retained even at alkaline pH. Heat stability test showed that the enzyme was heat stable; that is, 50% activity was retained after incubation at 56 degrees C for 60 min. These results suggest that cathepsin B secreted from human pancreatic cancer cell is a variant type and may play an important role in pancreatic cancer invasion or metastasis through destruction of the surrounding extracellular matrix by its proteolytic activity.