Acid-mediated tumor proteolysis: Contribution of cysteine cathepsins

Jennifer M. Rothberg, Kate M. Bailey, Jonathan W. Wojtkowiak, Yael Ben-Nun, Matthew Bogyo, Ekkehard Weber, Kamiar Moin, Galia Blum, Raymond R. Mattingly, Robert J. Gillies, Bonnie F. Sloane

Research output: Contribution to journalArticlepeer-review

86 Scopus citations


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 protease 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 bicarbonatetreated 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.

Original languageAmerican English
Pages (from-to)1125-1137
Number of pages13
JournalNeoplasia (United States)
Issue number10
StatePublished - Oct 2013

Bibliographical note

Funding Information:
Abbreviations: 3D, three-dimensional; ABP, activity-based probe; DQ-collagen IV, dye-quenched collagen IV; pHe, extracellular pH; rBM, reconstituted basement membrane; RFP, red fluorescent protein Address all correspondence to: Jennifer M. Rothberg, PhD, Department of Pharmacology, Wayne State University, 540 East Canfield, Detroit, MI 48201. E-mail: 1Research reported in this publication was supported by the National Institutes of Health under award numbers: R01 CA131990 (B.F.S./R.R.M.) along with a Research Supplement to Promote Diversity in Health-Related Research Programs (J.M.R.), R01 CA077575 (R.J.G.), and U54 CA143970 (R.J.G.). Imaging was performed in the Microscopy, Imaging and Cytometry Resources Core that is supported in part by National Institutes of Health Cancer Center Support grant P30 CA22453 and the Perinatology Research Branch of the National Institute of Child Health and Development. Moffitt Core Facilities are supported in part by Cancer Center Support grant P30 CA076292. 2This article refers to supplementary materials, which are designated by Figures W1 to W7 and Movies W1 to W8 and are available online at Received 9 May 2013; Revised 28 August 2013; Accepted 28 August 2013 Copyright © 2013 Neoplasia Press, Inc. All rights reserved 1522-8002/13/$25.00 DOI 10.1593/neo.13946


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