A cysteine proteinase secreted from human breast tumours is immunologically related to cathepsin B

Abstract
The stable cathepsin B-like cysteine (thiol) proteinase secreted from human breast tumors in culture was destabilized by mercurial compounds. After such treatment the enzyme cross-reacts in a radioimmunoassay with a monospecific antiserum to human liver cathepsin B. The secreted enzyme may be a precursor form of lysosomal cathepsin B.