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Tumor-Associated Galectin-3 Modulates the Function of Tumor-Reactive T Cells

¹ The Center for Cell and Gene Therapy, ² Department of Immunology, and ³ Department of Pathology, Baylor College of Medicine, Houston, Texas

Requests for reprints: Rong-Fu Wang, The Center for Cell and Gene Therapy, Baylor College of Medicine, ALKEK Building, N1120, One Baylor Plaza, Houston, Texas 77030. Phone: 713-798-1244; Fax: 713-798-1263; E-mail: rongfw{at}bcm.edu.

Key Words: Galectin-3 • Tumor-reactive T cells • Tumor microenvironment • Immune regulation

T cells play an important role in cancer immunosurveillance and tumor destruction. However, tumor cells alter immune responses by modulating immune cells through antigen stimulation and immunoregulatory cytokines. A better understanding of the interplay between tumor cells and T cells might provide new strategies to enhance antitumor immunity. Through an antigen-screening approach using colorectal tumor–reactive T cells, we identified an HLA-DR11–restricted T-cell epitope encoded by KIAA0040 as well as MHC-unrestricted human galectin-3 (Gal-3) expressed by tumor cells. Although the biological function of KIAA0040 remains to be determined, we found that Gal-3 functioned as an immune regulator for direct T-cell activation and function. T-cell activation induced by Gal-3 resulted in T-cell apoptosis. We showed that a high level of expression of Gal-3 promoted tumor growth in vitro and in vivo. Using a mouse tumor model, we showed that delivery of high doses of Gal-3 inhibited tumor-reactive T cells and promoted tumor growth in mice receiving tumor-reactive CD8⁺ T cells. These findings suggest that Gal-3 may function as an immune regulator to inhibit T-cell immune responses and promote tumor growth, thus providing a new mechanism for tumor immune tolerance. [Cancer Res 2008;68(17):7228–36]