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Matrilysin (MMP-7) Is a Novel Broadly Expressed Tumor Antigen Recognized by Antigen-Specific T Cells

Authors' Affiliations: ¹ Department of Oncology, Hematology, University of Bonn, Bonn, Germany; and ² Department of Oncology, Hematology, Immunology, Rheumatology and Pulmology and ³ Institute for Cell Biology, Department of Immunology, University of Tübingen, Tübingen, Germany

Requests for reprints: Peter Brossart, Department of Oncology, Hematology, University of Bonn, Wilhelmstrasse 35-35, 53111 Bonn, Germany. Phone: 228-28722234; Fax: 228-28722635; E-mail: peter.brossart{at}ukb.uni-bonn.de.

Purpose: A prerequisite for the development of vaccination strategies is the identification and characterization of relevant tumor-associated antigen. Using microarray and reverse transcription-PCR analysis, we found matrix metalloproteinase (MMP)-7 to be extensively up-regulated in renal cell carcinomas and expressed in a broad variety of malignant cells. MMP-7 can promote cancer invasion and angiogenesis by proteolytic cleavage of extracellular matrix and basement membrane proteins, thus making it a promising target in the context of immunotherapies.

Experimental Design: To analyze the possible use of MMP-7 as a tumor-associated antigen, specific CTLs were induced using monocyte-derived dendritic cells electroporated with MMP-7-mRNA. In addition, to better characterize the fine specificity of these CTLs, MMP-7 MHC class I ligands were isolated and characterized in renal cell carcinoma tissue, which overexpressed MMP-7, by mass spectrometry–based peptide sequencing. Using this approach, we identified a novel HLA-A3–binding antigenic MMP-7 peptide. CTLs generated from healthy donors by in vitro priming with dendritic cells, pulsed with the novel peptide, were used as effectors in ⁵¹Cr-release assays.

Results: The induced CTLs elicited an antigen-specific and HLA-restricted cytolytic activity against tumor cells endogenously expressing the MMP-7 protein. Furthermore, we were able to induce MMP-7–specific CTLs using peripheral blood mononuclear cells from a patient with acute lymphoblastic leukemia capable of recognizing the autologous leukemic blasts while sparing nonmalignant cells.

Conclusions: Our study describes the identification of a novel broadly expressed T-cell epitope derived from the MMP-7 protein that represents an interesting candidate to be applied in immunotherapies of human malignancies targeting both tumor cells and neovascularization.