Yung-Chang Lin

Tumor-Derived Chemokine CCL5 Enhances TGF-β–Mediated Killing of CD8+ T Cells in Colon Cancer by T-Regulatory Cells

Chemokine CCL5/RANTES is highly expressed in cancer where it contributes to inflammation and malignant progression. In this study, we show that CCL5 plays a critical role in immune escape in colorectal cancer. We found that higher levels of CCL5 expression in human and murine colon tumor cells correlated with higher levels of apoptosis of CD8+ T cells and infiltration of T-regulatory cells (T(reg)). In mouse cells, RNA interference (RNAi)-mediated knockdown of CCL5 delayed tumor growth in immunocompetent syngeneic hosts but had no effect on tumor growth in immunodeficient hosts. Reduced tumor growth was correlated with a reduction in T(reg) infiltration and CD8(+) T-cell apoptosis in tumors. Notably, we found that CCL5 enhanced the cytotoxicity of T(reg) against CD8(+) T cells. We also found tumor growth to be diminished in mice lacking CCR5, a CCL5 receptor, where a similar decrease in both T(reg) cell infiltration and CD8(+) T-cell apoptosis was noted. TGF-β signaling blockade diminished apoptosis of CD8(+) T cells, implicating TGF-β as an effector of CCL5 action. In support of this concept, CCL5 failed to enhance the production of TGF-β by CCR5-deficient T(reg) or to enhance their cytotoxic effects against CD8(+) T cells. CCR5 signaling blockade also diminished the in vivo suppressive capacity of T(reg) in inhibiting the antitumor responses of CD8(+) T cells, in the same way as CCL5 signaling blockade. Together, our findings establish that CCL5/CCR5 signaling recruits T(reg) to tumors and enhances their ability to kill antitumor CD8(+) T cells, thereby defining a novel mechanism of immune escape in colorectal cancer.

Activated but not resting regulatory T cells accumulated in tumor microenvironment and correlated with tumor progression in patients with colorectal cancer

Activated T regulatory (Treg) cells are potent suppressors that mediate immune tolerance. We investigated the relationship between activated Treg cells and the progression of human colon cancer. We designed a cross‐sectional study of CD4+Foxp3+ T cells from peripheral blood, primary tumor and nontumor colon tissue of 42 patients with colon cancer and correlated the percentages of different subgroups of Treg cells with colon cancer stage. The phenotypes, cytokine‐release patterns and suppression ability of these Treg cells were analyzed. We found that Treg cells increased significantly in both peripheral blood and cancer tissue. In addition, the Treg cells expressed significantly lower levels of CCR7, CD62L and CD45RA in comparison to normal volunteers. Further dividing Treg cells into subgroups based on Foxp3 and CD45RA expression revealed that both activated Treg cells (Foxp3hiCD45RA−) and nonsuppressive Treg cells (Foxp3loCD45RA−), but not resting Treg cells (Foxp3lowCD45RA+), increased in the peripheral blood and cancer tissue of patients with colon cancer. Only the activated Treg cells expressed significantly higher levels of tumor necrosis factor receptor 2 and cytotoxic T‐cell antigen‐4. Activated Treg cells, however, secreted significantly lower levels of effector cytokines (interleukin‐2, tumor necrosis factor‐α and interferon‐γ) than did resting Treg cells and nonsuppressive cells upon ex vivo stimulation. Activated, but not resting, Treg cells in cancer tissue correlated with tumor metastases. In summary, we confirmed that activated Treg cells are a distinct subgroup with effector memory phenotype and fully functional regulatory activity against human colorectal cancer immunity.

Effector/Memory but Not Naive Regulatory T Cells Are Responsible for the Loss of Concomitant Tumor Immunity

The phenomenon of concomitant tumor immunity involves a tumor-bearing host rejecting another similar tumor at a distant site and suggests the existence of tumor-specific immunity. Loss of this immunity may contribute to tumor metastasis. However, mechanisms underlying the loss of concomitant immunity are largely unknown. We set up a concomitant tumor immunity model in which this immunity is gradually lost as the primary tumor progresses. We found that CD8+ T cells, especially tumor-infiltrating CD8+ T cells, from mice that lost concomitant tumor immunity, possessed potent antitumor properties and strongly expressed effector molecules. Furthermore, effector/memory regulatory T cells (Treg cells, CD103+CD4+Foxp3+ T cells) increased as the primary tumor progressed. They initially accumulated around the tumor and in the spleen at later points. Not only did these cells more greatly express killing molecules, they also suppressed the functions of tumor-bearing CD8+ T cells in vitro and in vivo. Finally, we show that these effector/memory Treg cells inhibit concomitant tumor immunity in vivo. Taken together, data suggest that effector/memory Treg cells are responsible for the loss of concomitant tumor immunity associated with tumor progression.

Apoptosis of tumor infiltrating effector TIM-3+CD8+ T cells in colon cancer

TIM-3 functions to enforce CD8+ T cell exhaustion, a dysfunctional state associated with the tolerization of tumor microenvironment. Here we report apoptosis of IFN-γ competent TIM-3+ population of tumor-infiltrating CD8+ T cells in colon cancer. In humans suffering from colorectal cancer, TIM-3+ population is higher in cancer tissue-resident relative to peripheral blood CD8+ T cells. Both the TIM-3+ and TIM-3- cancer tissue-resident CD8+ T cells secrete IFN-γ of comparable levels, although apoptotic cells are more in TIM-3+ compared to TIM-3- population. In mouse CT26 colon tumor model, majority of tumor-infiltrating CD8+ T cells express TIM-3 and execute cytolysis function with higher effector cytokine secretion and apoptosis in TIM-3+ compared to TIM-3- population. The tumor cells secrete galectin-9, which increases apoptosis of tumor-infiltrating CD8+ T cells. Galectin-9/TIM-3 signaling blockade with anti-TIM-3 antibody reduces the apoptosis and in addition, inhibits tumor growth in mice. The blockade increases therapeutic efficacy of cyclophosphamide to treat tumor in mice as well. These results reveal a previously unexplored role of TIM-3 on tumor-infiltrating CD8+ T cells in vivo.

The Indispensable Role of CCR5 for In Vivo Suppressor Function of Tumor-Derived CD103+ Effector/Memory Regulatory T Cells

CD103 is a marker for identification of effector/memory regulatory T cells (Tregs). CD103+ Tregs are potent suppressors of tissue inflammation in several infectious diseases, autoimmune diseases, and cancers. However, the underlying mechanisms for this potent suppression ability remain unclear. The current study was designed to clarify this issue. Unexpectedly, we found both CD103+ and CD103− Tregs had similar suppression capacity in vitro. We then chose a murine tumor model for investigation of the in vivo behavior of these Tregs. The suppression ability in vivo against the anti-tumor ability of CD8+ T cells was restricted to CD103+ Tregs although both Tregs had equal in vitro suppression ability. In addition, CD103+ Tregs expressed significantly higher levels of CCR5 than those of CD103− Tregs and accumulated more in tumors than did CD103− Tregs. Furthermore, blockade of CCR5 signaling, either by CCR5−/−CD103+ Tregs or by CCL5 knockdown tumor, could reduce the migration of CD103+ Tregs into tumors and impair their in vivo suppression ability. In conclusion, these results indicate that the potent in vivo suppression ability of CD103+ Tregs is due to the tissue-migration ability through CCR5 expression.

Blockade of TNF-α signaling benefits cancer therapy by suppressing effector regulatory T cell expansion

Effector but not naive regulatory T cells (Treg cells) can accumulate in the peripheral blood as well as the tumor microenvironment, expand during tumor progression and be one of the main suppressors for antitumor immunity. However, the underlying mechanisms for effector Treg cell expansion in tumor are still unknown. We demonstrate that effector Treg cell-mediated suppression of antitumor CD8+ T cells is tumor-nonspecific. Furthermore, TNFR2 expression is increased in these Treg cells by Affymetrix chip analysis which was confirmed by monoclonal antibody staining in both hepatocellular carcinoma (HCC) and colorectal cancer (CRC) patients and murine models. Correspondingly, increased levels of TNF-α in both tissue and serum were also demonstrated. Interestingly, TNF-α could not only expand effector Treg cells through TNFR2 signaling, but also enhanced their suppressive activity against antitumor immunity of CD8+ T cells. Furthermore, targeting TNFR2 signaling with a TNF-α inhibitor could selectively reduce rapid resurgence of effector Treg cells after cyclophosphamide-induced lymphodepletion and markedly inhibit the growth of established tumors. Herein, we propose a novel mechanism in which TNF-α could promote tumor-associated effector Treg cell expansion and suggest a new cancer immunotherapy strategy using TNF-α inhibitors to reduce effector Treg cells expansion after cyclophosphamide-induced lymphodepletion.

CD4⁺ T cells expressing latency-associated peptide and Foxp3 are an activated subgroup of regulatory T cells enriched in patients with colorectal cancer.

Latency-associated peptide (LAP) - expressing regulatory T cells (Tregs) are important for immunological self-tolerance and immune homeostasis. In order to investigate the role of LAP in human CD4+Foxp3+ Tregs, we designed a cross-sectional study that involved 42 colorectal cancer (CRC) patients. The phenotypes, cytokine-release patterns, and suppressive ability of Tregs isolated from peripheral blood and tumor tissues were analyzed. We found that the population of LAP-positive CD4+Foxp3+ Tregs significantly increased in peripheral blood and cancer tissues of CRC patients as compared to that in the peripheral blood and tissues of healthy subjects. Both LAP+ and LAP− Tregs had a similar effector/memory phenotype. However, LAP+ Tregs expressed more effector molecules, including tumor necrosis factor receptor II, granzyme B, perforin, Ki67, and CCR5, than their LAP− negative counterparts. The in vitro immunosuppressive activity of LAP+ Tregs, exerted via a transforming growth factor-β–mediated mechanism, was more potent than that of LAP− Tregs. Furthermore, the enrichment of LAP+ Treg population in peripheral blood mononuclear cells (PBMCs) of CRC patients correlated with cancer metastases. In conclusion, we found that LAP+ Foxp3+ CD4+ Treg cells represented an activated subgroup of Tregs having more potent regulatory activity in CRC patients. The increased frequency of LAP+ Tregs in PBMCs of CRC patients suggests their potential role in controlling immune response to cancer and presents LAP as a marker of tumor-specific Tregs in CRC patients.

IL-10 inhibits neuraminidase-activated TGF-β and facilitates Th1 phenotype during early phase of infection

Th1 cells control their activity by producing regulatory IL-10. Here we report that Th1 cell-derived IL-10 facilitates their expansion and, in addition, augments Th1 cell production of IFN-γ, TNF-α and IL-2 during the early phase of influenza. In our antigen-specific mouse experimental system, influenza haemagglutinin-specific CD4(+) T cells respond to infection with the induction of T-bet, and produce both IFN-γ and IL-10. In the early phase of infection, an abundance of viral neuraminidase causes TGF-β activation of haemagglutinin-specific CD4(+) T cells. CD4(+) T-cell-derived IL-10 inhibits neuraminidase-driven TGF-β activation and counteracts the virus-mediated immune suppression. As the host eradicates the virus, neuraminidase activity wanes and IL-10 receptors are upregulated on CD4(+) T cells in the late phase of infection. IL-10 then suppresses immune activation and aids in recovery from infection and inflammation. These results reveal a previously unrecognized function of Th1 cell-derived IL-10 in vivo.

LAP+CD4+ T cells are suppressors accumulated in the tumor sites and associated with the progression of colorectal cancer.

Purpose: Suppressor T cells are one of the determinants of colorectal cancer (CRC) clinical outcome. LAP+CD4+ T cell is a recently identified subset of suppressor T cells. This study was designed to investigate their clinical relevance in patients with CRC. Experimental Design: Sixty patients with CRC and 24 healthy donors (HD) were enrolled in this study. The percentages of LAP+CD4+ T cells in peripheral blood and tumor tissue were measured. The phenotype and functional relevance of LAP+CD4+ T cells were analyzed subsequently. Results: The percentages of LAP+CD4+ T cells in peripheral blood of patients with CRC were significantly higher than HD (HD vs. CRC: 3.1% ± 0.78% vs. 8.8% ± 5.8%, P < 0.0001) and in tumor tissue when compared with nontumor tissue (nontumor vs. tumor: 3.2% ± 1.1% vs. 9.5% ± 5.5%, P = 0.0002). In addition, LAP+CD4+ T cells with effector memory (EM) phenotype were more likely to accumulate in the tumor sites than in peripheral blood. These LAP+CD4+ T cells produced significantly higher levels of IFN-γ, IL-17 and comparatively lower IL-2 and very few IL-10. LAP+CD4+ T cells could suppress the proliferation of LAP−CD4+ T cells that were partially mediated by TGF-β. Furthermore, these LAP+CD4+ T cells accumulated in tumor site and increased further in the peripheral blood in patients with metastasis. Conclusions: LAP+CD4+ T cells as a suppressor subset could accumulate in the tumor microenvironment and circulated more in the peripheral blood with tumor progression in patients with CRC. Clin Cancer Res; 18(19); 5224–33. ©2012 AACR.

Altered T-bet Dominance in IFN-γ–Decoupled CD4+ T Cells with Attenuated Cytokine Storm and Preserved Memory in Influenza

Cytokine storm has been postulated as one of the major causes of mortality in patients with severe respiratory viral infections such as influenza. With the help of an influenza Ag- specific mouse experimental system, we report that CD4+ T cells contribute effector cytokines leading to lung inflammation in acute influenza. Although virus can no longer be detected from tissues 14 d postinfection, virus-derived Ag continues to drive a CD4+ T cell response after viral clearance. Ag-specific CD4+ T cells proliferate and evolve into memory CD4+ T cells efficiently, but the production of effector cytokines is seriously hampered during this phase. This decoupling of proliferation and effector cytokine production doesn’t appear in conjunction with increased suppression by regulatory T cells or decreased induction of transcription factors. Rather, GATA-3 and ROR-γt levels are elevated when compared with cells that have effector cytokine production. T-bet dominance over GATA-3 and ROR-γt decreases with the disarmament of effector cytokine production. Importantly, upon reinfection, these decoupled cells produce elevated levels of IFN-γ and were effective in virus eradication. These results provide a mechanism through altered T-bet dominance to dampen the cytokine storm without impeding the generation of memory T cells in influenza virus infection.