Low molecular weight proteinase inhibitors. II. Extraction and identification of activity from infiltrating ductal carcinoma during lactation.

Extracts of both infiltrating ductal carcinoma and non-tumorous tissue were obtained from the same mastectomy specimen of a lactating female patient. The extracts were ultrafiltered and concentrated to recover proteins having nominal molecular weights between 1000 and 50,000 daltons. Although the final concentrates of both samples contained proteinase-inhibitory activities with electrophoretic mobilities similar to that of Trasylol, only the extract from the tumour had significant trypsin-inhibitory activity as expressed by the inhibition of the hydrolysis of TAME (p-tosyl-L-arginine methyl ester). Molecular sieve chromatography by high performance liquid chromatography of the final concentrate of the tumour indicated that the activity was present in three peaks having apparent molecular weights of less than 17,000.