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Mediators of Inflammation
Volume 2012 (2012), Article ID 456462, 13 pages
http://dx.doi.org/10.1155/2012/456462
Research Article

Cathepsin G Induces Cell Aggregation of Human Breast Cancer MCF-7 Cells via a 2-Step Mechanism: Catalytic Site-Independent Binding to the Cell Surface and Enzymatic Activity-Dependent Induction of the Cell Aggregation

Laboratory of Host Defense, Department of Pharma-Sciences, Teikyo University, 2-11-1 Kaga, Itabashi-ku, Tokyo 173-8605, Japan

Received 29 February 2012; Revised 1 May 2012; Accepted 28 May 2012

Academic Editor: Luc Vallières

Copyright © 2012 Riyo Morimoto-Kamata et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Neutrophils often invade various tumor tissues and affect tumor progression and metastasis. Cathepsin G (CG) is a serine protease secreted from activated neutrophils. Previously, we have shown that CG induces the formation of E-cadherin-mediated multicellular spheroids of human breast cancer MCF-7 cells; however, the molecular mechanisms involved in this process are unknown. In this study, we investigated whether CG required its enzymatic activity to induce MCF-7 cell aggregation. The cell aggregation-inducing activity of CG was inhibited by pretreatment of CG with the serine protease inhibitors chymostatin and phenylmethylsulfonyl fluoride. In addition, an enzymatically inactive S195G (chymotrypsinogen numbering) CG did not induce cell aggregation. Furthermore, CG specifically bound to the cell surface of MCF-7 cells via a catalytic site-independent mechanism because the binding was not affected by pretreatment of CG with serine protease inhibitors, and cell surface binding was also detected with S195G CG. Therefore, we propose that the CG-induced aggregation of MCF-7 cells occurs via a 2-step process, in which CG binds to the cell surface, independently of its catalytic site, and then induces cell aggregation, which is dependent on its enzymatic activity.