3^rd Glycobiology World Congress

Biography

Biography: Pierre van der Bruggen

Abstract

We describe a new mechanism of dysfunction of human tumor-infiltrating lymphocytes (TILs). TILs failed to secrete cytokines and lytic enzymes upon stimulation, although they were normally activated and able to produce these effector molecules inside the cell. Surprisingly, these effector molecules remained trapped inside the cell. This defect is related to the presence of galectin-3 at the TIL surface and can be relieved by agents that detach galectin-3 from the TIL surface. The normal secretion process is blocked in dysfunctional TILs, due to impaired LFA-1 mobility and actin rearrangement at the secretory synapse. This is the first observation of uncoupling between cytokine production and cytokine secretion in TILs.

We also hypothesise that galectins lattices hanged on the tumor microenvironment may capture glycosylated immune factors, blocking their anti-tumor function. The presence of galectin-3 in the tumor microenvironment reduced IFNγ diffusion and ability to induce the chemokine gradient necessary to attract anti-tumor T lymphocytes. Galectin-3 captured in vitro glycosylated IFNγ, and reduces IFNγ diffusion through a collagen matrix. Inhibiting galectins enhanced the capacity of human tumor cells to express CXCL9/10 upon IFNγ treatment in vitro. In a humanized mouse model, human galectin-3 restricts the intratumor diffusion of IFNγ. Co-injection of IFNγ and galectin antagonists improved tumor infiltration by autologous CD8+ T cells injected intravenously and delayed tumor growth,  as compared with tumors injected with IFNγ alone . Our results contribute to explain why some human tumors can be considered as ‘cold’ as they are poorly infiltrated by anti-tumor T lymphocytes.