Acid protease secreted from human pancreatic carcinoma cell line HPC-YT into serum-free, chemically defined medium

Active acid protease was found in serum-free spent medium of human pancreatic carcinoma cell line HPC-YT. These cells have been maintained for over 215 generations in a serum-free, chemically defined medium. Acid protease was partially purified about 3000-fold by Mono Q ion-exchange chromatography, pepstatin-aminohexyl-Sepharose affinity chromatography, hydroxylapatite affinity chromatography, lectin affinity chromatographies, and gel filtration on TSK G3000SW. The molecular weight of the purified enzyme was estimated to be 63,000. An acid protease isolated from normal pancreas has two forms with molecular weights of 11,000 and 32,000. Isoelectric focusing of acid protease derived from HPC-YT revealed five isotypes, whereas the enzyme from normal pancreas showed only three bands. The optimal pH using bovine hemoglobin as substrate was 3.0 for both the normal and the HPC-YT-derived acid proteases. The HPC-YT enzyme was more heat stable than the enzymes of normal pancreas. Sulfhydryl compounds and metal ions had no apparent effects on this enzyme; however, pepstatin strongly inhibited it. We suggest that acid protease secreted from cancer cells may play a role in the destruction of the surrounding tissue matrix.