title: Cathepsin B-like activity in viable tumor cells isolated from rodent tumors.
abstract: The cathepsin B-like cysteine proteinase activity which has been implicated in tumor malignancy has been attributed to several cellular sources, including viable tumor cells, necrotic tumor cells, and host-inflammatory cells. We have isolated subpopulations of cells from eight rodent tumors of five histological types, using centrifugal elutriation, and verified the cellular composition of the subpopulations cytologically. Ninety-two % or greater of the cathepsin B-like activity was associated with the isolated fractions containing greater than or equal to 95% tumor cells of 86 +/- 2% (SE) viability (beta fractions). The isolated fractions consisting of necrotic tumor cells and inflammatory cells (alpha fraction) apparently contain a cysteine proteinase inhibitor, since both cathepsin B-like and cathepsin H activities in the beta fraction of B16 amelanotic melanomas could be inhibited by addition of the alpha fraction.
mesh_terms: D000818:Animals; D002401:Cathepsin B; D056655:Cathepsin H; D002403:Cathepsins / Q000378:metabolism*; D002498:Centrifugation; D003546:Cysteine Endopeptidases; D008175:Lung Neoplasms / Q000556:secondary; D008247:Lysosomes / Q000201:enzymology; D051379:Mice; D009374:Neoplasms, Experimental / Q000201:enzymology*; D011480:Protease Inhibitors; D051381:Rats
chemical_list: D011480:Protease Inhibitors; D002403:Cathepsins; D003546:Cysteine Endopeptidases; D002401:Cathepsin B; D056655:Cathepsin H; C534127:Ctsh protein, mouse; C534128:Ctsh protein, rat