Proteinase activity in malignant human breast cancers and NMU mammary tumours of the rat.

In subcellular fractions of human mammary tumours and NMU tumours of rats proteinase activity was studied by means of the synthetic substrates Bz-dl-arginin-4-nitroanilid (BAPNA) and Bz-dl-arginin-2-naphthyl-amid (BANA). Using the substrate BAPNA enzymatic activity was found to be highest in low speed particulate fractions, whereas in NMU tumours of rats the bulk of the activities could be observed in the high speed supernatant. The substrates BAPNA and BANA were cleavaged enzymatically in human mammary tumours at pH 7 and pH 6, respectively, while in rats the maximum turnover of both substrates changed at value of pH 6.5. Enzyme activity with BAPNA was proved to be resistant to alkaline preincubation in human breast cancer tissue only. On the other hand, the enzymatic cleavage of BANA was completely lost in human as well as in rat tumour specimens under these experimental conditions. It can be concluded from these results that both enzyme activities measured in human malignant mammary tumours, which are known for their invading activity, represent two different proteolytic enzymes with their maximum activity at neutral and acidic pH. Similar enzyme activities are quite different in NMU tumours, which are not invasive.