1. ¹Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107, USA
2. ²LifeCell Corporation, Branchburg, NJ 08876, USA
3. ³Cellular Biology and Signaling Program, Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, PA 19107, USA

Correspondence: RV Iozzo, Department of Pathology, Anatomy and Cell Biology, Room 249, JAH, Thomas Jefferson University, 1020 Locust Street, Philadelphia, PA 19107, USA. E-mail: iozzo@mail.jci.tju.edu

Received 13 August 2004; Accepted 12 October 2004; Published online 27 December 2004.

Abstract

Metastases in breast cancer are a vital concern in treatment, with epidermal growth factor receptor and ErbB2 strongly implicated in mediating tumor invasion and spreading. In this study, we investigated the role of decorin in suppressing both primary breast carcinomas and pulmonary metastases. We show that decorin causes marked growth suppression both in vitro and in vivo using a metastatic breast cancer cell line and an orthotopic mammary carcinoma model. Treatment with decorin protein core reduced primary tumor growth by 70% and eliminated observed metastases. An adenoviral vector containing the decorin transgene caused primary tumor retardation of 70%, in addition to greatly reducing observed metastases. Moreover, we demonstrate that ErbB2 phosphorylation and total receptor protein levels are reduced in this model system upon de novo expression of decorin under the control of a doxycycline-inducible promoter. Primary tumor growth in vivo was reduced by up to 67% upon decorin induction, and pulmonary metastases were markedly hampered as well. These effects are likely occurring through decorin's long-term downregulation of the ErbB2 tyrosine kinase cascade. These results demonstrate a novel role for decorin in reduction or prevention of tumor metastases in this breast cancer model and could eventually lead to improved therapeutics for metastatic breast cancer.