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We previously reported (Bell, D., P. Chomarat, D. Broyles, G. Netto, G.M. Harb, S. Lebecque, J. Valladeau, J. Davoust, K.A. Palucka, and J. Banchereau. 1999. J. Exp. Med. 190: 1417–1426) that breast cancer tumors are infiltrated with mature dendritic cells (DCs), which cluster with CD4+ T cells. We now show that CD4+ T cells infiltrating breast cancer tumors secrete type 1 (interferon γ) as well as high levels of type 2 (interleukin [IL] 4 and IL-13) cytokines. Immunofluorescence staining of tissue sections revealed intense IL-13 staining on breast cancer cells. The expression of phosphorylated signal transducer and activator of transcription 6 in breast cancer cells suggests that IL-13 actually delivers signals to cancer cells. To determine the link between breast cancer, DCs, and CD4+ T cells, we implanted human breast cancer cell lines in nonobese diabetic/LtSz-scid/scid β2 microglobulin–deficient mice engrafted with human CD34+ hematopoietic progenitor cells and autologous T cells. There, CD4+ T cells promote early tumor development. This is dependent on DCs and can be partially prevented by administration of IL-13 antagonists. Thus, breast cancer targets DCs to facilitate its development.

TSLP released from human breast cancer cells promotes OX40L expression on DCs, and these OX40L-expressing DCs drive development of inflammatory Th2 cells which promote breast tumor development.

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, CD41CD251Foxp31 regulatory T cells (Tregs) accumulate in the tumor milieu and are potent suppressors of autologous tumorspecific 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 CD41CD252 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;57:183-194) T he two most common types of cancer affecting the liver are hepatocellular carcinoma (HCC) and liver metastases from colorectal cancer (LM-CRC). 1,2 The current therapeutic options for both malignancies are limited to liver surgery and local (ablative) therapy. At the time of diagnosis, the majority of HCC patients are not candidates for curative treatment, and in patients with LM-CRC there is a high rate of recurrence after treatment. 1,2 Consequently, there is a pressing need for novel therapeutic strategies. Immunotherapy is attractive because of the exquisite specificity of the immune response and may thus avoid many of the side effects associated with currently available clinical options. 3 However, immunological tolerance of the liver or immunoregulatory mechanisms present in the tumor microenvironment, such as those described by us and others in breast, 4-6 ovarian, 7 and renal 8 cancer, may contribute to tumor outgrowth and limit immunotherapeutic strategies by suppressing the local antitumor response.There is accumulating evidence that CD4þFoxP3þ regulatory T cells (Tregs) hamper the development of effective tumor immunity in individuals with cancer. 9,10

SummaryImmunity results from a complex interplay between the antigen-nonspecific innate immune system and the antigen-specific adaptive immune system. The cells and molecules of the innate system employ non-clonal recognition receptors including lectins, Toll-like receptors, NOD-like receptors and helicases. B and T lymphocytes of the adaptive immune system employ clonal receptors recognizing antigens or their derived peptides in a highly specific manner. An essential link between innate and adaptive immunity is provided by dendritic cells (DCs). DCs can induce such contrasting states as immunity and tolerance. The recent years have brought a wealth of information on the biology of DCs revealing the complexity of this cell system. Indeed, DC plasticity and subsets are prominent determinants of the type and quality of elicited immune responses. Here we summarize our recent studies aimed at a better understanding of the DC system to unravel the pathophysiology of human diseases and design novel human vaccines.

CD4 type 1 T regulatory (Tr1) cells have a crucial role in inducing tolerance. Immune regulation by these cells is mainly mediated through the secretion of high amounts of IL-10. Several studies have suggested that this regulatory population may be involved in tumor-mediated immune-suppression. However, direct evidence of a role for Tr1 cells in human solid tumors is lacking. Using isolated cells from individuals with hepatocellular carcinoma (HCC; = 39) or liver metastases from colorectal cancer (LM-CRC; = 60) we identify a CD4FoxP3IL-13IL-10 T cell population in tumors of individuals with primary or secondary liver cancer that is characterized as Tr1 cells by the expression of CD49b and the lymphocyte activation gene 3 () and strong suppression activity of T cell responses in an IL-10 dependent manner. Importantly, the presence of tumor-infiltrating Tr1 cells is correlated with tumor infiltration of plasmacytoid dendritic cells (pDCs). pDCs exposed to tumor-derived factors enhance IL-10 production by Tr1 cells through up-regulation of the inducible co-stimulatory ligand (ICOS-L). These findings suggest a role for pDCs and ICOS-L in promoting intra-tumoral immunosuppression by Tr1 cells in human liver cancer, which may foster tumor progression and which might interfere with attempts of immunotherapeutic intervention.

Our studies showed that tumor-infiltrating dendritic cells (DC) in breast cancer drive inflammatory T helper 2 (iTh2) cells and protumor inflammation. Here we show that intratumoral delivery of the β-glucan curdlan, a ligand of dectin-1, blocks the generation of iTh2 cells, and prevents breast cancer progression in vivo. Curdlan reprograms tumor-infiltrating DC via the ligation of dectin-1, enabling the DC to become resistant to cancer-derived thymic stromal lymphopoietin (TSLP), to produce IL12p70, and to favor the generation of T helper 1 (Th1) cells. DC activated via dectin-1, but not those activated with TLR-7/8 ligand or poly IC, induce CD8+ T cells to express CD103 (αE integrin), a ligand for cancer cells E-cadherin. Generation of these mucosal CD8+ T cells is regulated by DC-derived integrin αvβ8 and TGF-β activation in a dectin-1-dependent fashion. These CD103+CD8+ mucosal T cells accumulate in the tumors thereby increasing cancer necrosis and inhibiting cancer progression in vivo in a humanized mouse model of breast cancer. Importantly, CD103+CD8+ mucosal T cells elicited by reprogrammed DC can reject established cancer. Thus, reprogramming tumor-infiltrating DC represents a new strategy for cancer rejection.

Background and ObjectivesPatients with isolated colorectal‐cancer‐liver‐metastases (CRCLM) frequently undergo metastatectomy. Tumor‐infiltrating‐lymphocytes (TILs) have prognostic potential in the setting of primary colorectal cancer, however, their role in CRCLM is less studied. We aimed to study the spatial distribution and prognostic role of tumor‐infiltrating CD8+ cytotoxic T‐cells and FoxP3+ regulatory T‐cells at the metastatic site of CRCLM patients.MethodsTILs were isolated from fresh metastatic tissues of 47 patients with CRCLM. Archived paraffin‐embedded tissue, from the same patients, was retrieved. CD8+ and FoxP3+ cells, both in the intra‐tumoral and the peri‐tumoral compartments, were measured by immunohistochemistry on full tissue sections. Proportions of cytotoxic T‐cells (CD8+) and regulatory T‐cells (CD4+CD25+FoxP3+), within CD45+TILs, were measured by flow‐cytometry.ResultsBy immunohistochemistry, individual densities of intra‐tumoral or peri‐tumoral CD8+ and FoxP3+ cells were not prognostic of survival. However, the intra‐tumoral, but not the peri‐tumoral, CD8+/FoxP3+ ratio was an independent predictor of survival (HR 0.43, 95%CI 0.19‐0.95, P = 0.032). By flow cytometry, the intra‐tumoral CD8+/regulatory T‐cell ratio was also an independent predictor of survival (HR 0.45, 95%CI 0.20‐0.99, P = 0.044).ConclusionsThe ratio of cytotoxic (CD8+) to regulatory (FoxP3+) T‐cells, in the intra‐tumoral compartment, but not in the peri‐tumoral compartment, can predict survival after resection of CRCLM.