The mechanisms that enable liver cancer to escape elimination by the immune system remain unclear, but their elucidation may provide novel therapeutic interventions. We investigated the influence of tumor-infiltrating regulatory T cells on tumor-specific T cell responses in patients with liver cancer, using ex vivo isolated cells from individuals with hepatocellular carcinoma (HCC) or liver metastases from colorectal cancer (LM-CRC). Here we report that in both HCC and LM-CRC, CD4+CD25+Foxp3+ regulatory T cells (Tregs) accumulate in the tumor milieu and are potent suppressors of autologous tumor-specific T cell responses. Especially in LM-CRC, where Treg accumulation is more prominent, there is good evidence for local proliferation of Tregs at the cancer site. We show that tumor Tregs up-regulate the expression of glucocorticoid-induced tumor necrosis factor receptor (GITR) compared with Tregs in tumor-free liver tissue and blood. Importantly, treatment with soluble GITR ligand (GITRL) induces a decrease in the suppression mediated by the activated tumor-infiltrating Tregs and restores the proliferative capacity and cytokine production of CD4+CD25- T cells. Conclusion: Our results show that tumor-associated Tregs are critical for immune evasion in liver cancer, and we propose that GITRL constitutes a rational treatment for this disease. (HEPATOLOGY 2013) Copyright,
Department of Pathology

Pedroza-Gonzalez, A, Verhoef, C, IJzermans, J.N.M, Peppelenbosch, M.P, Kwekkeboom, J, Verheij, J, … Sprengers, D. (2013). Activated tumor-infiltrating CD4+ regulatory T cells restrain antitumor immunity in patients with primary or metastatic liver cancer. Hepatology, 57(1), 183–194. doi:10.1002/hep.26013