title: Acid-mediated tumor proteolysis: contribution of cysteine cathepsins.
abstract: One of the noncellular microenvironmental factors that contribute to malignancy of solid tumors is acidic peritumoral pH. We have previously demonstrated that extracellular acidosis leads to localization of the cysteine pro-tease cathepsin B on the tumor cell membrane and its secretion. The objective of the present study was to determine if an acidic extracellular pH such as that observed in vivo (i.e., pHe 6.8) affects the activity of proteases, e.g., cathepsin B, that contribute to degradation of collagen IV by tumor cells when grown in biologically relevant three-dimensional (3D) cultures. For these studies, we used 1) 3D reconstituted basement membrane overlay cultures of human carcinomas, 2) live cell imaging assays to assess proteolysis, and 3) in vivo imaging of active tumor proteases. At pHe 6.8, there were increases in pericellular active cysteine cathepsins and in degradation of dye-quenched collagen IV, which was partially blocked by a cathepsin B inhibitor. Imaging probes for active cysteine cathepsins localized to tumors in vivo. The amount of bound probe decreased in tumors in bicarbonate-treated mice, a treatment previously shown to increase peritumoral pHe and reduce local invasion of the tumors. Our results are consistent with the acid-mediated invasion hypothesis and with a role for cathepsin B in promoting degradation of a basement membrane protein substrate, i.e., type IV collagen, in an acidic peritumoral environment.
authors.affiliation: Cancer Biology Program, Wayne State University, Detroit, MI ; Department of Pharmacology, Wayne State University, Detroit, MI.
authors.forename: Jennifer M
authors.initials: JM
authors.lastname: Rothberg
authors.forename: Kate M
authors.initials: KM
authors.lastname: Bailey
authors.forename: Jonathan W
authors.initials: JW
authors.lastname: Wojtkowiak
authors.forename: Yael
authors.initials: Y
authors.lastname: Ben-Nun
authors.forename: Matthew
authors.initials: M
authors.lastname: Bogyo
authors.forename: Ekkehard
authors.initials: E
authors.lastname: Weber
authors.forename: Kamiar
authors.initials: K
authors.lastname: Moin
authors.forename: Galia
authors.initials: G
authors.lastname: Blum
authors.forename: Raymond R
authors.initials: RR
authors.lastname: Mattingly
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Gillies
authors.forename: Bonnie F
authors.initials: BF
authors.lastname: Sloane
mesh_terms: D000818:Animals; D001943:Breast Neoplasms / Q000378:metabolism*; D002401:Cathepsin B / Q000378:metabolism*; D045744:Cell Line, Tumor; D024141:Collagen Type IV / Q000378:metabolism; D003110:Colonic Neoplasms / Q000378:metabolism*; D004792:Enzyme Precursors / Q000378:metabolism; D045604:Extracellular Fluid / Q000378:metabolism; D005260:Female; D064593:Heterografts; D006801:Humans; D006863:Hydrogen-Ion Concentration; D051379:Mice; D016513:Mice, SCID; D009368:Neoplasm Transplantation; D059748:Proteolysis
chemical_list: D024141:Collagen Type IV; D004792:Enzyme Precursors; D002401:Cathepsin B