In A-D) Western blots showing vaccine-specific sera reactive responses in all 60 vaccinated patients and 22 healthy donors. In E-F) Identification of antibody-reactive proteins by serological proteomics. G-I) Antibody responses to influenza proteins analyzed from the same sera shown for galectin-3 titers are intact and unaffected by multiple immunotherapy treatments in vaccinated patients.
ARTICLE ABSTRACT
Galectin-3 is a 31-kDa lectin that modulates T-cell responses through several mechanisms, including apoptosis, T-cell receptor (TCR) cross-linking, and TCR downregulation. We found that patients with pancreatic ductal adenocarcinoma (PDA) who responded to a granulocyte-macrophage colony-stimulating factor–secreting allogeneic PDA vaccine developed neutralizing antibodies to galectin-3 after immunization. We show that galectin-3 binds activated antigen-committed CD8+ T cells only in the tumor microenvironment. Galectin-3–deficient mice exhibit improved CD8+ T-cell effector function and increased expression of several inflammatory genes. Galectin-3 binds to LAG-3, and LAG-3 expression is necessary for galectin-3–mediated suppression of CD8+ T cells in vitro. Lastly, galectin-3–deficient mice have elevated levels of circulating plasmacytoid dendritic cells, which are superior to conventional dendritic cells in activating CD8+ T cells. Thus, inhibiting galectin-3 in conjunction with CD8+ T-cell–directed immunotherapies should enhance the tumor-specific immune response. Cancer Immunol Res; 3(4); 412–23. ©2015 AACR.
