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Cancer Immunology at the Crossroads

Treg Fragility: A Prerequisite for Effective Antitumor Immunity?

Abigail E. Overacre-Delgoffe and Dario A.A. Vignali
Abigail E. Overacre-Delgoffe
1Department of Immunology, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania.
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Dario A.A. Vignali
1Department of Immunology, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania.
2Tumor Microenvironment Center, UPMC Hillman Cancer Center, Pittsburgh, Pennsylvania.
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  • For correspondence: dvignali@pitt.edu
DOI: 10.1158/2326-6066.CIR-18-0066 Published August 2018
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Abstract

Inhibitory checkpoint blockade has significantly improved patient response rate across numerous tumor types. However, most patients remain unresponsive to immunotherapy, suggesting that unappreciated mechanisms of resistance exist. The tumor microenvironment (TME) is unique and composed of many suppressive cell populations that inhibit antitumor immune responses, including regulatory T cells (Tregs). The TME is nutrient poor, acidic, and hypoxic, creating a challenging microenvironment for immune cells to function and survive. Tregs suppress a wide variety of cell populations through multiple mechanisms and are tasked with limiting tissue damage. Tregs are now considered to be a barrier to effective antitumor immunity. Systemic Treg depletion is not favored because of their critical role in maintaining immune homeostasis and preventing autoimmunity. Reducing Treg function specifically within the TME may provide a more effective, targeted approach to limit the immunosuppressive environment within the tumor without inducing systemic adverse consequences. Targeting molecules that cause Treg instability, characterized by loss of critical Treg transcription factors such as Foxp3, could result in conversion into cells that cause immune pathology, tissue damage, and subsequent autoimmune side effects. Interferon-γ (IFNγ) can cause intratumoral Treg “fragility,” which results in loss of suppressive activity and increased IFNγ production without loss of Foxp3 expression and gross Treg “identity.” We reviewed the impact Tregs have on the TME and vice versa, and their implications for responsiveness to cancer immunotherapy. We propose that the extent to which intratumoral Tregs develop a “fragile” phenotype following immunotherapy will predict and dictate responsiveness. Cancer Immunol Res; 6(8); 882–7. ©2018 AACR.

Introduction

Immunotherapy became a major pillar of cancer treatment around 2010, when an antibody targeting the inhibitory receptor, CTLA-4 (Ipilimumab), showed a ∼20% increase in overall survival in metastatic melanoma patients, followed by FDA approval (1, 2). Interest in immunotherapy grew rapidly in 2014, when another antibody targeting PD-1 (Nivolumab) was approved with better than anticipated patient responses, showing a 40% objective response rate in melanoma (3). Unfortunately, many patients remained unresponsive. The underlying mechanisms of immunotherapy resistance remain obscure. However, one potential roadblock is the presence of suppressive cell populations, such as regulatory T cells (Tregs; ref. 4), which remain dominant despite the mechanistic benefits of inhibitory receptor blockade.

Tregs function as the master regulators of the immune system, maintaining homeostasis and preventing autoimmunity. Initially identified as “suppressive cells” (5), Tregs are characterized by the transcription factor Foxp3, which is required for their development and function in mice (6, 7). Treg-suppressive function is exerted through a variety of mechanisms, such as cytokine secretion (including IL10, IL35, and TGFβ), metabolic disruption through CD39:CD73 adenosine production or IL2 deprivation, direct cytolysis through granzyme B, and modulation of DC development and function via LAG3 and CTLA-4 (8). Tregs also play a key role in limiting tissue damage, but the mechanisms utilized remain to be fully elucidated (9). Tregs can develop in the thymus (tTregs), arise in the periphery (pTregs), or be generated in vitro with the addition of TGFβ (iTregs; ref. 10). We primarily focus on tTregs (herein denoted as “Tregs”). However, the role of pTregs in tumors, their stabilizing factors, and whether they become fragile in tumors remains unclear and warrants further investigation.

In the absence of Tregs or when the Foxp3 locus is disrupted, rampant systemic autoimmunity ensues. This presents as IPEX (immune dysregulation polyendocrinopathy, enteropathy, x-linked) in patients and is lethal without a bone marrow transplant. In mice that lack expression of Foxp3 through genetic deletion or the “Scurfy mutation” (6), autoimmune symptoms can be substantively delayed by Treg cell transfer within 48 hours of birth (11). Although Tregs are critical for preventing autoimmunity, they also suppress the antitumor immune response and promote tumor outgrowth (4). Treg depletion in tumor models has been studied in Foxp3DTR-GFP mice (12), where the majority of mice clear the tumor but subsequently succumb to systemic autoimmunity (13, 14).

The tumor microenvironment (TME) is unique in that it is nutrient poor, hypoxic, and acidic, making it a taxing environment for many immune subsets, such as effector T cells (Teffs), that are primarily glycolytic. In contrast to this, Tregs rely on oxidative phosphorylation and are thought to have a proliferative and functional advantage within hypoxic, acidic environments (15). Increased Tregs have been observed in a variety of cancer patient peripheral blood and tumors (16, 17), and many cancer types show a positive correlation between higher Treg percentages and poor prognosis in patients. Treg percentages in the tumor mass can increase with severity of stage (18), and higher Treg percentages correlate with poorer disease-free survival in several cancers (19). As a result, Tregs have been targeted in the clinic, albeit with limited success. Depletion strategies targeting the IL2 pathway, through use of antibodies or other small molecules, led to off-target effects such as depletion of Teffs or loss of DC-mediated T-cell activation, in addition to incomplete depletion of Tregs (20, 21).

CTLA-4 blockade has been identified as a potential Treg target due to high surface expression. Previous studies have shown that CTLA-4 antibodies with FcγR ADCC activity reduced Tregs in the TME and that a positive correlation exists between reduced Tregs and CTLA-4 blockade response in bladder cancer patients (22). CTLA-4 blockade was initially thought to work on Tregs through either depletion or reduction of suppression (23). However, effects on both Teff and Treg compartments are required for full antitumor function (24). Blockade led to increased peripheral Tregs and reduced intratumoral Tregs due to higher CTLA-4 expression on intratumoral Tregs and the presence of FcγR-expressing macrophages. Subsequent studies suggested that CTLA-4 blockade also led to increased Teffs in both the tumor and periphery, highlighting a role for both Tregs and Teff in patient response (25).

An anti-CCR4 (mogamulizumab; defucosylated to enhance ADCC) is in clinical trials and targets Tregs through the CCL22:CCR4-mediated recruitment to the tumor, which has shown some clinical efficacy (26). Although encouraging, these strategies still show limited efficacy, thereby further highlighting the need to identify new avenues to target Treg function, potentially through destabilization or by driving Treg fragility specifically within the TME.

Treg stability is defined as sustained Foxp3 expression, hypomethylation at the CNS2 locus, and maintained suppressive function. However, the prevalence and impact of Treg instability remains controversial (27–31). In contrast to Treg instability, Treg fragility is defined as the retention of Foxp3 expression with loss of suppressive function (32). Fragile Tregs produce IFNγ and upregulate the IFNγ receptor, as well the transcription factor Tbet. They have reduced expression of suppressive molecules, such as CD73 and IL10, and are functionally less suppressive in the TME (Fig. 1; ref. 32). In this review, we address the following: (i) How is Treg stability maintained? (ii) How is Treg fragility induced? (iii) Is responsiveness to immunotherapy dependent on Treg fragility?

Figure 1.
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Figure 1.

Contributing factors of stable, fragile, and unstable Tregs. Stable Tregs: hypomethylated at CNS2 and express other stabilizing markers like Nrp1 and Helios. Fragile Tregs: secrete IFNγ while maintaining Foxp3 expression. Unstable Tregs: loss Foxp3 expression and secrete proinflammatory cytokines.

Building Up: How Is Treg Stability Maintained?

Treg stability has been discussed across many disease types. Treg instability was initially defined as the loss of Foxp3 expression in cells and subsequent loss of suppressive function. This is thought to be, in part, due to lack of demethylation or remethylation at certain sites within the Foxp3 locus (33). Demethylation in this locus was first described in 2007 when a region in the 5′ UTR of the Foxp3 locus containing a number of conserved demethylated CpG motifs, was identified (known as the TSDR/CNS2). This demethylation pattern is observed in both thymic and mature peripheral Tregs in mice and peripheral blood of humans. In contrast, the CNS2 is methylated in effector CD4+ T cells. Hypomethylation of the Foxp3 locus is thought to be required for Treg stability, but occurs independently of Foxp3 upregulation (34). It was shown that TGFβ-induced Tregs (iTregs) display a somewhat hypermethylated Foxp3 locus (34), and tumor-derived Tregs exhibit a primarily demethylated locus (35). However, variations within CNS2 methylation patterns (∼10%–60%) suggest that the intratumoral Treg pool may be heterogeneous. Previous studies have identified two subsets of Tregs (Foxp3Hi and Foxp3Lo) in the tumor and periphery of colorectal patients that display differences in suppressive capacity and CNS2 methylation status (36, 39). Another possibility that could contribute to the heterogeneity of Tregs within the tumor is the conversion of conventional T (Tconv) cells to Tregs. However, TCR repertoires between these two populations appear to be distinct (37, 38). Whether Foxp3+ Tregs with a partially methylated Foxp3 locus are a functionally unstable population or a heterogeneous population comprised of both stable and unstable Tregs remains unclear. The possibility that there are other factors that lead to the remethylation of the locus in the TME warrants further investigation.

In addition to epigenetic alterations of the Foxp3 locus, loss of Foxp3 expression is a hallmark of unstable Tregs. A number of factors involved in maintaining Foxp3 expression have been identified, including IL2/STAT5 and Foxo1/3a. STAT5 binds to the Foxp3 locus, and in its absence, Treg development is reduced (Fig. 1; ref. 40), while Foxo1 and Foxo3a translocate to the nucleus of Tregs and prevent effector functions (41). Induction of Foxp3 and subsequent Treg development can also be prevented by persistent TCR stimulation, leading to constitutive activation of the PI3K/Akt/mTOR pathway (42), or in the absence of the microRNA processing enzyme Dicer (43).

Loss of Foxp3 expression has also been reported in certain disease settings, such as lymphopenia and autoimmune diabetes (27). Fate-mapping mice were used to trace all cells that currently or previously expressed Foxp3, regardless of subsequent downregulation. “ExTregs,” which no longer express Foxp3, upregulated IL7R, secreted IFNγ and IL17, took on a pathogenic role, and worsened disease (29). Other groups report that Foxp3 expression is stable and that previously identified exTregs were likely T cells that transiently upregulated Foxp3 during differentiation or activation (31, 44). Very few exTregs have been observed in mouse models of cancer (32), suggesting Foxp3 is stable in these models. Other studies have highlighted a role for Helios in maintaining Foxp3 expression and showed that in its absence, Foxp3 was reduced, and Helios-deficient Tregs secreted IFNγ in the TME (45, 46). However, whether unstable Tregs exist in patients is unknown and remains difficult to assess without cell lineage tracing capabilities or definitive markers.

Breaking Down: How Is Treg Fragility Induced?

Multiple factors have been reported previously to be important for preventing Treg fragility, including Nrp1, Foxo1, and Eos (14, 32, 46–49). Although Nrp1 can be expressed on a number of cell types, it is upregulated on Tregs and supports Treg function through binding of semaphorin-4a (Sema4a). In the absence of Nrp1 signaling, either through Nrp1 blockade or genetic deletion (using Nrp1L/LFoxp3Cre-YFP mice), intratumoral Tregs show reduced cell survival, reduced expression of suppressive markers (such as CD73, IL10, and IL35), and significantly impaired suppressive function (Fig. 1). Surprisingly, this did not result in loss of Foxp3 expression. Mice cleared tumors similarly to mice lacking Tregs, but they displayed no signs of autoimmunity. Nrp1+ Tregs are also increased in metastatic melanoma and head and neck squamous cell carcinoma patients compared with healthy donors (32). Patients with a larger population of Nrp1+ Tregs correlated with reduced disease-free survival. It was later shown that Nrp1− Tregs produce IFNγ and were less suppressive than wild-type (WT) Tregs but maintained Foxp3 expression. Secretion of IFNγ only occurred within the TME, likely as a result of sustained or increased Hif1α expression due to hypoxia and heightened Akt activity (14, 32, 50, 51). It is possible that the unique metabolic environment within the TME contributes to Treg stability, as they are more adept at tolerating this “harsh environment” compared with effector T cells. Distinct metabolic differences between Tregs and other T-cell subsets have been found (52, 53), which may also underlie the preferential restriction of a fragility Treg phenotype to the TME following Nrp1 deletion/blockade or immunotherapy.

Previous reports have shown that although Foxo1 is key for Foxp3 upregulation during Treg development, the loss or mutation of Foxo1 from mature Tregs leads to a fragile phenotype rather than an unstable one. Specifically, Foxo1-deficient Tregs are less suppressive and secrete IFNγ, but Foxp3 expression is maintained and the percentage of Tregs increases in vivo. Foxo1 deletion in Tregs leads to an IFNγ-dependent lethal inflammatory phenotype (54). However, unlike the phenotype observed in the absence of Nrp1, wherein fragility appears to be restricted to the TME (14, 32), the loss of Foxo1 results in a fragile phenotype that is systemic, leading to the inflammatory phenotype. Similarly, Eos is upregulated in Tregs, and when removed, Treg suppression is reduced, IFNγ and IL2 are upregulated, but Foxp3 expression remains unchanged (47). It has been reported that when LAG3 is deleted on Tregs, Eos is increased and leads to better suppressive function in an autoimmune diabetes setting (55). It is possible that LAG3 limits Eos expression in Tregs, thereby promoting fragility, but further studies are required.

Is Response to Immunotherapy Dependent on Treg Fragility?

Intratumoral Tregs display a distinct profile, suggesting specific markers could be targeted within the TME that might lead to Treg instability or Treg fragility. However, whether this is observed in cancer patient intratumoral Tregs and predicts patient responsiveness remains unknown. We hypothesize that Tregs within the TME upregulate stabilizing molecules, such as NRP1, and that patients who respond to immunotherapy exhibit a more fragile intratumoral Treg phenotype.

Treg fragility appears to be required for response to anti–PD-1 in murine tumor models. In an adenocarcinoma mouse model that is sensitive to PD-1 blockade, treatment of WT mice with anti–PD-1 led to the upregulation of IFNγ+ Tregs, consistent with an increased fragile phenotype. When Tregs were insensitive to IFNγ (through the use of an Ifngr1L/LFoxp3Cre-YFP mouse), mice were completely resistant to PD-1 blockade in comparison with ∼40% response in WT mice (32), suggesting a role for Treg fragility in responsiveness to immunotherapy. Similarly, reduction of tumor burden through the use of a GITR agonist antibody (DTA-1) was due to an increase in IFNγ+ Tregs and reduction in Helios expression (45, 56). As mentioned, CD8:Treg ratios have been shown to be indicative of patient response to therapy. However, the idea that Treg fragility is the key component to determining response to immunotherapy was previously unappreciated.

Similarly, previous studies have identified IFNγ+ Tregs in human samples in autoimmune diseases, such as multiple sclerosis and type 1 diabetes, where these cells have reduced suppression and altered methylation while maintaining Foxp3 expression, suggesting a fragile phenotype (34, 57, 58). Patients with malignant glioma (GBM) exhibit a higher percentage of circulating PD-1Hi Tregs that are less suppressive and express IFNγ. PD-1Hi Tregs bear a distinct transcriptional profile, are phenotypically exhausted as defined by upregulation of LAG3 and Tim3, and show a slight reduction in CNS2 demethylation. When GBM patients were treated with anti–PD-1 (nivolumab), the exhausted PD-1+IFNγ+ Treg population increased (59). This population has been observed in other tumor types, such as late advanced rectal cancer, where it correlated with poorer patient response (60). These data suggest that PD-1 blockade, as well as other immunotherapies, may act, in part, through inducing a fragile Treg phenotype in patients. Whether this is a direct effect of anti–PD-1 on Tregs or an indirect effect of increased IFNγ in the TME acting on Tregs to drive fragility remains to be determined.

Given that the impact of Treg fragility in immunotherapy has not been fully elucidated in the clinic, assessing the extent to which patient Tregs develop a fragile phenotype following immunotherapy could aid in both prediction of patient susceptibility to anti–PD-1, as well as provide a rationale for patient responsiveness to immunotherapy. Sensitizing Tregs to become fragile may be an effective strategy to utilize alongside PD-1 blockade. Although PD-1 blockade has been shown to upregulate IFNγ in CD8+ T cells, whether this directly affects Tregs remains unclear in the clinic. However, IFNγ-sensitive Tregs have been observed in patient samples and were found to be less suppressive following IFNγ treatment in vitro (32). Although PD-1 blockade has been the primary focus thus far, it is possible that Treg fragility plays a key role in responsiveness to other immunotherapies in the clinic or perhaps the efficacy of any immunotherapy. One possibility could be to target a known driver of Treg fragility prevention, such as NRP1, through antibody blockade. Although Tregs become fragile in mice upon loss of Nrp1 through either genetic deletion or antibody blockade, whether this is conserved in human Tregs after Nrp1 depletion remains to be further investigated. Although a higher percentage of Nrp1+ Tregs in patients appears to correlate with reduced disease-free survival, it remains unclear whether this is due to enhanced Treg stability. We would argue that inducing Treg fragility may be a preferred therapeutic strategy compared with Treg depletion or destabilizing Tregs because the effect on Tregs seems to be restricted to the TME, thereby preventing autoimmune side effects.

Identifying ways to target Treg fragility while leaving Treg stability intact may be critical, given the previously identified pathogenic nature of unstable Tregs or exTregs in various diseases (Fig. 1; refs. 27–29). It is possible that local Treg destabilization strategies may be efficacious. However, the potential systemic autoimmune effects of this are unknown, and distinguishing between the two Treg subsets can be challenging. Although some clear markers of fragile Tregs have been identified, including Nrp1, PD-1, and IFNγR1, specific markers do not exist for unstable Tregs that distinguish them from Th-like cells, and tracking the presence of exTregs in patient samples is not yet feasible. There may be more unappreciated markers of Treg fragility that warrant further investigation.

Although targeting molecules that prevent Treg fragility in the clinic may represent the clearest step forward, many interrelated questions remain: (i) What are the markers of unstable or exTregs in patients? (ii) Are there other drivers of Treg fragility? Although IFNγ has been shown to drive Treg fragility, it is possible that other cytokines or soluble factors could lead to a similar phenotype. (iii) Do fragile Tregs display hypermethylation at the Foxp3 CNS2 locus, and does this lead to reduced suppressive function? (iv) What is the level of Treg fragility and instability in checkpoint blockade responders and nonresponders, and do they correlate? (v) Is Treg fragility a biomarker of patient response to immunotherapy? (vi) Does patient response to immunotherapy depend on Treg fragility? Although loss of Nrp1 and increased IFNγ sensitivity have been identified as drivers of Treg fragility, other molecules that contribute to this phenotype have yet to be defined. We propose that the development of combinatorial immunotherapies that maximize Treg fragility may maximize efficacy and improve patient response to immunotherapy.

Disclosure of Potential Conflicts of Interest

D.A.A. Vignali reports receiving commercial research funding from Potenza, Tizona, and Bristol-Myers Squibb; has ownership interest in Bristol-Myers Squibb, Potenza, Tizona, Oncorus, and Merck; and is a consultant/advisory board member for Potenza, Tizona, Oncorus, FStar, and Pieris. No potential conflicts of interest were disclosed by the other author.

Acknowledgments

This work was supported by the NIH (R01 CA203689 and P01 AI108545 to D.A.A. Vignali) and a NCI Comprehensive Cancer Center Support CORE grant (CA047904 to D.A.A. Vignali).

We thank the Vignali laboratory for helpful discussions.

  • ©2018 American Association for Cancer Research.

References

  1. 1.↵
    1. Leach DR,
    2. Krummel MF,
    3. Allison JP
    . Enhancement of antitumor immunity by CTLA-4 blockade. Science 1996;271:1734–6.
    OpenUrlAbstract
  2. 2.↵
    1. Hodi FS,
    2. O'Day SJ,
    3. McDermott DF,
    4. Weber RW,
    5. Sosman JA,
    6. Haanen JB,
    7. et al.
    Improved survival with ipilimumab in patients with metastatic melanoma. N Engl J Med 2010;363:711–23.
    OpenUrlCrossRefPubMed
  3. 3.↵
    1. Topalian SL,
    2. Hodi FS,
    3. Brahmer JR,
    4. Gettinger SN,
    5. Smith DC,
    6. McDermott DF,
    7. et al.
    Safety, activity, and immune correlates of anti-PD-1 antibody in cancer. N Engl J Med 2012;366:2443–54.
    OpenUrlCrossRefPubMed
  4. 4.↵
    1. Liu C,
    2. Workman CJ,
    3. Vignali DA
    . Targeting regulatory T cells in tumors. FEBS J 2016;283:2731–48.
    OpenUrl
  5. 5.↵
    1. Kuniyasu Y,
    2. Takahashi T,
    3. Itoh M,
    4. Shimizu J,
    5. Toda G,
    6. Sakaguchi S
    . Naturally anergic and suppressive CD25(+)CD4(+) T cells as a functionally and phenotypically distinct immunoregulatory T cell subpopulation. Int Immunol 2000;12:1145–55.
    OpenUrlCrossRefPubMed
  6. 6.↵
    1. Sakaguchi S
    . Naturally arising CD4+ regulatory T cells for immunologic self-tolerance and negative control of immune responses. Annu Rev Immunol 2004;22:531–62.
    OpenUrlCrossRefPubMed
  7. 7.↵
    1. Fontenot JD,
    2. Gavin MA,
    3. Rudensky AY
    . Foxp3 programs the development and function of CD4+CD25+ regulatory T cells. Nat Immunol 2003;4:330–6.
    OpenUrlCrossRefPubMed
  8. 8.↵
    1. Vignali DA,
    2. Collison LW,
    3. Workman CJ
    . How regulatory T cells work. Nat Rev Immunol 2008;8:523–32.
    OpenUrlCrossRefPubMed
  9. 9.↵
    1. Hori S,
    2. Takahashi T,
    3. Sakaguchi S
    . Control of autoimmunity by naturally arising regulatory CD4+ T cells. Adv Immunol 2003;81:331–71.
    OpenUrlCrossRefPubMed
  10. 10.↵
    1. Abbas AK,
    2. Benoist C,
    3. Bluestone JA,
    4. Campbell DJ,
    5. Ghosh S,
    6. Hori S,
    7. et al.
    Regulatory T cells: recommendations to simplify the nomenclature. Nat Immunol 2013;14:307–8.
    OpenUrlCrossRefPubMed
  11. 11.↵
    1. Workman CJ,
    2. Collison LW,
    3. Bettini M,
    4. Pillai MR,
    5. Rehg JE,
    6. Vignali DA
    . In vivo Treg suppression assays. Methods Mol Biol 2011;707:119–56.
    OpenUrlCrossRefPubMed
  12. 12.↵
    1. Kim J,
    2. Lahl K,
    3. Hori S,
    4. Loddenkemper C,
    5. Chaudhry A,
    6. deRoos P,
    7. et al.
    Cutting edge: depletion of Foxp3+ cells leads to induction of autoimmunity by specific ablation of regulatory T cells in genetically targeted mice. J Immunol 2009;183:7631–4.
    OpenUrlAbstract/FREE Full Text
  13. 13.↵
    1. Bos PD,
    2. Plitas G,
    3. Rudra D,
    4. Lee SY,
    5. Rudensky AY
    . Transient regulatory T cell ablation deters oncogene-driven breast cancer and enhances radiotherapy. J Exp Med 2013;210:2435–66.
    OpenUrlAbstract/FREE Full Text
  14. 14.↵
    1. Delgoffe GM,
    2. Woo SR,
    3. Turnis ME,
    4. Gravano DM,
    5. Guy C,
    6. Overacre AE,
    7. et al.
    Stability and function of regulatory T cells is maintained by a neuropilin-1-semaphorin-4a axis. Nature 2013;501:252–6.
    OpenUrlCrossRefPubMed
  15. 15.↵
    1. Scharping NE,
    2. Delgoffe GM
    . Tumor microenvironment metabolism: a new checkpoint for anti-tumor immunity. Vaccines 2016;4. pii: E46.
    OpenUrl
  16. 16.↵
    1. Woo EY,
    2. Chu CS,
    3. Goletz TJ,
    4. Schlienger K,
    5. Yeh H,
    6. Coukos G,
    7. et al.
    Regulatory CD4(+)CD25(+) T cells in tumors from patients with early-stage non-small cell lung cancer and late-stage ovarian cancer. Cancer Res 2001;61:4766–72.
    OpenUrlAbstract/FREE Full Text
  17. 17.↵
    1. Liyanage UK,
    2. Moore TT,
    3. Joo HG,
    4. Tanaka Y,
    5. Herrmann V,
    6. Doherty G,
    7. et al.
    Prevalence of regulatory T cells is increased in peripheral blood and tumor microenvironment of patients with pancreas or breast adenocarcinoma. J Immunol 2002;169:2756–61.
    OpenUrlAbstract/FREE Full Text
  18. 18.↵
    1. Curiel TJ,
    2. Coukos G,
    3. Zou L,
    4. Alvarez X,
    5. Cheng P,
    6. Mottram P,
    7. et al.
    Specific recruitment of regulatory T cells in ovarian carcinoma fosters immune privilege and predicts reduced survival. Nat Med 2004;10:942–9.
    OpenUrlCrossRefPubMed
  19. 19.↵
    1. Tzankov A,
    2. Meier C,
    3. Hirschmann P,
    4. Went P,
    5. Pileri SA,
    6. Dirnhofer S
    . Correlation of high numbers of intratumoral FOXP3+ regulatory T cells with improved survival in germinal center-like diffuse large B-cell lymphoma, follicular lymphoma and classical Hodgkin's lymphoma. Haematologica 2008;93:193–200.
    OpenUrlAbstract/FREE Full Text
  20. 20.↵
    1. Onizuka S,
    2. Tawara I,
    3. Shimizu J,
    4. Sakaguchi S,
    5. Fujita T,
    6. Nakayama E
    . Tumor rejection by in vivo administration of anti-CD25 (interleukin-2 receptor alpha) monoclonal antibody. Cancer Res 1999;59:3128–33.
    OpenUrlAbstract/FREE Full Text
  21. 21.↵
    1. Dannull J,
    2. Su Z,
    3. Rizzieri D,
    4. Yang BK,
    5. Coleman D,
    6. Yancey D,
    7. et al.
    Enhancement of vaccine-mediated antitumor immunity in cancer patients after depletion of regulatory T cells. J Clin Invest 2005;115:3623–33.
    OpenUrlCrossRefPubMed
  22. 22.↵
    1. Liakou CI,
    2. Kamat A,
    3. Tang DN,
    4. Chen H,
    5. Sun J,
    6. Troncoso P,
    7. et al.
    CTLA-4 blockade increases IFNγ-producing CD4+ICOShi cells to shift the ratio of effector to regulatory T cells in cancer patients. Proc Natl Acad Sci USA 2008;105:14987–92.
    OpenUrlAbstract/FREE Full Text
  23. 23.↵
    1. Wing K,
    2. Onishi Y,
    3. Prieto-Martin P,
    4. Yamaguchi T,
    5. Miyara M,
    6. Fehervari Z,
    7. et al.
    CTLA-4 control over Foxp3+ regulatory T cell function. Science 2008;322:271–5.
    OpenUrlAbstract/FREE Full Text
  24. 24.↵
    1. Peggs KS,
    2. Quezada SA,
    3. Chambers CA,
    4. Korman AJ,
    5. Allison JP
    . Blockade of CTLA-4 on both effector and regulatory T cell compartments contributes to the antitumor activity of anti-CTLA-4 antibodies. J Exp Med 2009;206:1717–25.
    OpenUrlAbstract/FREE Full Text
  25. 25.↵
    1. Simpson TR,
    2. Li F,
    3. Montalvo-Ortiz W,
    4. Sepulveda MA,
    5. Bergerhoff K,
    6. Arce F,
    7. et al.
    Fc-dependent depletion of tumor-infiltrating regulatory T cells co-defines the efficacy of anti-CTLA-4 therapy against melanoma. J Exp Med 2013;210:1695–710.
    OpenUrlAbstract/FREE Full Text
  26. 26.↵
    1. Ishida T,
    2. Joh T,
    3. Uike N,
    4. Yamamoto K,
    5. Utsunomiya A,
    6. Yoshida S,
    7. et al.
    Defucosylated anti-CCR4 monoclonal antibody (KW-0761) for relapsed adult T-cell leukemia-lymphoma: a multicenter phase II study. J Clin Oncol 2012;30:837–42.
    OpenUrlAbstract/FREE Full Text
  27. 27.↵
    1. Zhou X,
    2. Bailey-Bucktrout S,
    3. Jeker LT,
    4. Bluestone JA
    . Plasticity of CD4(+) FoxP3(+) T cells. Curr Opin Immunol 2009;21:281–5.
    OpenUrlCrossRefPubMed
  28. 28.↵
    1. Komatsu N,
    2. Okamoto K,
    3. Sawa S,
    4. Nakashima T,
    5. Oh-hora M,
    6. Kodama T,
    7. et al.
    Pathogenic conversion of Foxp3+ T cells into TH17 cells in autoimmune arthritis. Nat Med 2014;20:62–8.
    OpenUrlCrossRefPubMed
  29. 29.↵
    1. Zhou X,
    2. Bailey-Bucktrout SL,
    3. Jeker LT,
    4. Penaranda C,
    5. Martinez-Llordella M,
    6. Ashby M,
    7. et al.
    Instability of the transcription factor Foxp3 leads to the generation of pathogenic memory T cells in vivo. Nat Immunol 2009;10:1000–7.
    OpenUrlCrossRefPubMed
  30. 30.↵
    1. Floess S,
    2. Freyer J,
    3. Siewert C,
    4. Baron U,
    5. Olek S,
    6. Polansky J,
    7. et al.
    Epigenetic control of the foxp3 locus in regulatory T cells. PLoS Biol 2007;5:e38.
    OpenUrlCrossRefPubMed
  31. 31.↵
    1. Rubtsov YP,
    2. Niec RE,
    3. Josefowicz S,
    4. Li L,
    5. Darce J,
    6. Mathis D,
    7. et al.
    Stability of the regulatory T cell lineage in vivo. Science 2010;329:1667–71.
    OpenUrlAbstract/FREE Full Text
  32. 32.↵
    1. Overacre-Delgoffe AE,
    2. Chikina M,
    3. Dadey RE,
    4. Yano H,
    5. Brunazzi EA,
    6. Shayan G,
    7. et al.
    Interferon-γ drives Treg fragility to promote anti-tumor immunity. Cell 2017;169:1130–41 e11.
    OpenUrl
  33. 33.↵
    1. Overacre AE,
    2. Vignali DA
    . T(reg) stability: to be or not to be. Curr Opin Immunol 2016;39:39–43.
    OpenUrlCrossRefPubMed
  34. 34.↵
    1. Ohkura N,
    2. Hamaguchi M,
    3. Morikawa H,
    4. Sugimura K,
    5. Tanaka A,
    6. Ito Y,
    7. et al.
    T cell receptor stimulation-induced epigenetic changes and Foxp3 expression are independent and complementary events required for Treg cell development. Immunity 2012;37:785–99.
    OpenUrlCrossRefPubMed
  35. 35.↵
    1. Waight JD,
    2. Takai S,
    3. Marelli B,
    4. Qin G,
    5. Hance KW,
    6. Zhang D,
    7. et al.
    Cutting edge: epigenetic regulation of Foxp3 defines a stable population of CD4+ regulatory T cells in tumors from mice and humans. J Immunol 2015;194:878–82.
    OpenUrlAbstract/FREE Full Text
  36. 36.↵
    1. Saito T,
    2. Nishikawa H,
    3. Wada H,
    4. Nagano Y,
    5. Sugiyama D,
    6. Atarashi K,
    7. et al.
    Two FOXP3(+)CD4(+) T cell subpopulations distinctly control the prognosis of colorectal cancers. Nat Med 2016;22:679–84.
    OpenUrlCrossRefPubMed
  37. 37.↵
    1. Hindley JP,
    2. Ferreira C,
    3. Jones E,
    4. Lauder SN,
    5. Ladell K,
    6. Wynn KK,
    7. et al.
    Analysis of the T-cell receptor repertoires of tumor-infiltrating conventional and regulatory T cells reveals no evidence for conversion in carcinogen-induced tumors. Cancer Res 2011;71:736–46.
    OpenUrlAbstract/FREE Full Text
  38. 38.↵
    1. Sainz-Perez A,
    2. Lim A,
    3. Lemercier B,
    4. Leclerc C
    . The T-cell receptor repertoire of tumor-infiltrating regulatory T lymphocytes is skewed toward public sequences. Cancer Res 2012;72:3557–69.
    OpenUrlAbstract/FREE Full Text
  39. 39.↵
    1. Lal G,
    2. Zhang N,
    3. van der Touw W,
    4. Ding Y,
    5. Ju W,
    6. Bottinger EP,
    7. et al.
    Epigenetic regulation of Foxp3 expression in regulatory T cells by DNA methylation. J Immunol 2009;182:259–73.
    OpenUrlAbstract/FREE Full Text
  40. 40.↵
    1. Burchill MA,
    2. Yang J,
    3. Vogtenhuber C,
    4. Blazar BR,
    5. Farrar MA
    . IL-2 receptor beta-dependent STAT5 activation is required for the development of Foxp3+ regulatory T cells. J Immunol 2007;178:280–90.
    OpenUrlAbstract/FREE Full Text
  41. 41.↵
    1. Ouyang W,
    2. Beckett O,
    3. Ma Q,
    4. Paik JH,
    5. DePinho RA,
    6. Li MO
    . Foxo proteins cooperatively control the differentiation of Foxp3+ regulatory T cells. Nat Immunol 2010;11:618–27.
    OpenUrlCrossRefPubMed
  42. 42.↵
    1. Haxhinasto S,
    2. Mathis D,
    3. Benoist C
    . The AKT-mTOR axis regulates de novo differentiation of CD4+Foxp3+ cells. J Exp Med 2008;205:565–74.
    OpenUrlAbstract/FREE Full Text
  43. 43.↵
    1. Liston A,
    2. Lu LF,
    3. O'Carroll D,
    4. Tarakhovsky A,
    5. Rudensky AY
    . Dicer-dependent microRNA pathway safeguards regulatory T cell function. J Exp Med 2008;205:1993–2004.
    OpenUrlAbstract/FREE Full Text
  44. 44.↵
    1. Miyao T,
    2. Floess S,
    3. Setoguchi R,
    4. Luche H,
    5. Fehling HJ,
    6. Waldmann H,
    7. et al.
    Plasticity of Foxp3(+) T cells reflects promiscuous Foxp3 expression in conventional T cells but not reprogramming of regulatory T cells. Immunity 2012;36:262–75.
    OpenUrlCrossRefPubMed
  45. 45.↵
    1. Nakagawa H,
    2. Sido JM,
    3. Reyes EE,
    4. Kiers V,
    5. Cantor H,
    6. Kim HJ
    . Instability of Helios-deficient Tregs is associated with conversion to a T-effector phenotype and enhanced antitumor immunity. Proc Natl Acad Sci USA 2016;113:6248–53.
    OpenUrlAbstract/FREE Full Text
  46. 46.↵
    1. Kim HJ,
    2. Barnitz RA,
    3. Kreslavsky T,
    4. Brown FD,
    5. Moffett H,
    6. Lemieux ME,
    7. et al.
    Stable inhibitory activity of regulatory T cells requires the transcription factor Helios. Science 2015;350:334–9.
    OpenUrlAbstract/FREE Full Text
  47. 47.↵
    1. Pan F,
    2. Yu H,
    3. Dang EV,
    4. Barbi J,
    5. Pan X,
    6. Grosso JF,
    7. et al.
    Eos mediates Foxp3-dependent gene silencing in CD4+ regulatory T cells. Science 2009;325:1142–6.
    OpenUrlAbstract/FREE Full Text
  48. 48.↵
    1. Kerdiles YM,
    2. Stone EL,
    3. Beisner DR,
    4. McGargill MA,
    5. Ch'en IL,
    6. Stockmann C,
    7. et al.
    Foxo transcription factors control regulatory T cell development and function. Immunity 2010;33:890–904.
    OpenUrlCrossRefPubMed
  49. 49.↵
    1. Luo CT,
    2. Liao W,
    3. Dadi S,
    4. Toure A,
    5. Li MO
    . Graded Foxo1 activity in Treg cells differentiates tumour immunity from spontaneous autoimmunity. Nature 2016;529:532–6.
    OpenUrlCrossRefPubMed
  50. 50.↵
    1. Dang EV,
    2. Barbi J,
    3. Yang HY,
    4. Jinasena D,
    5. Yu H,
    6. Zheng Y,
    7. et al.
    Control of T(H)17/T(reg) balance by hypoxia-inducible factor 1. Cell 2011;146:772–84.
    OpenUrlCrossRefPubMed
  51. 51.↵
    1. Lee JH,
    2. Elly C,
    3. Park Y,
    4. Liu YC
    . E3 ubiquitin ligase VHL regulates hypoxia-inducible factor-1alpha to maintain regulatory T cell stability and suppressive capacity. Immunity 2015;42:1062–74.
    OpenUrlCrossRefPubMed
  52. 52.↵
    1. Delgoffe GM
    . Filling the tank: keeping antitumor T cells metabolically fit for the long haul. Cancer Immunol Res 2016;4:1001–6.
    OpenUrlAbstract/FREE Full Text
  53. 53.↵
    1. Johnson MO,
    2. Siska PJ,
    3. Contreras DC,
    4. Rathmell JC
    . Nutrients and the microenvironment to feed a T cell army. Semin Immunol 2016;28:505–13.
    OpenUrl
  54. 54.↵
    1. Ouyang W,
    2. Liao W,
    3. Luo CT,
    4. Yin N,
    5. Huse M,
    6. Kim MV,
    7. et al.
    Novel Foxo1-dependent transcriptional programs control T(reg) cell function. Nature 2012;491:554–9.
    OpenUrlCrossRefPubMed
  55. 55.↵
    1. Zhang Q,
    2. Chikina M,
    3. Szymczak-Workman AL,
    4. Horne W,
    5. Kolls JK,
    6. Vignali KM,
    7. et al.
    LAG3 limits regulatory T cell proliferation and function in autoimmune diabetes. Science immunology 2017;2. pii: eaah4569. doi: 10.1126/sciimmunol.aah4569.
    OpenUrl
  56. 56.↵
    1. Schaer DA,
    2. Budhu S,
    3. Liu C,
    4. Bryson C,
    5. Malandro N,
    6. Cohen A,
    7. et al.
    GITR pathway activation abrogates tumor immune suppression through loss of regulatory T cell lineage stability. Cancer Immunol Res 2013;1:320–31.
    OpenUrlAbstract/FREE Full Text
  57. 57.↵
    1. Dominguez-Villar M,
    2. Baecher-Allan CM,
    3. Hafler DA
    . Identification of T helper type 1-like, Foxp3+ regulatory T cells in human autoimmune disease. Nat Med 2011;17:673–5.
    OpenUrlCrossRefPubMed
  58. 58.↵
    1. McClymont SA,
    2. Putnam AL,
    3. Lee MR,
    4. Esensten JH,
    5. Liu W,
    6. Hulme MA,
    7. et al.
    Plasticity of human regulatory T cells in healthy subjects and patients with type 1 diabetes. J Immunol 2011;186:3918–26.
    OpenUrlAbstract/FREE Full Text
  59. 59.↵
    1. Lowther DE,
    2. Goods BA,
    3. Lucca LE,
    4. Lerner BA,
    5. Raddassi K,
    6. van Dijk D,
    7. et al.
    PD-1 marks dysfunctional regulatory T cells in malignant gliomas. JCI Insight 2016;1. pii: e85935.
    OpenUrl
  60. 60.↵
    1. Twyman-Saint Victor C,
    2. Rech AJ,
    3. Maity A,
    4. Rengan R,
    5. Pauken KE,
    6. Stelekati E,
    7. et al.
    Radiation and dual checkpoint blockade activate non-redundant immune mechanisms in cancer. Nature 2015;520:373–7.
    OpenUrlCrossRefPubMed
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Cancer Immunology Research: 6 (8)
August 2018
Volume 6, Issue 8
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Treg Fragility: A Prerequisite for Effective Antitumor Immunity?
Abigail E. Overacre-Delgoffe and Dario A.A. Vignali
Cancer Immunol Res August 1 2018 (6) (8) 882-887; DOI: 10.1158/2326-6066.CIR-18-0066

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Treg Fragility: A Prerequisite for Effective Antitumor Immunity?
Abigail E. Overacre-Delgoffe and Dario A.A. Vignali
Cancer Immunol Res August 1 2018 (6) (8) 882-887; DOI: 10.1158/2326-6066.CIR-18-0066
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    • Building Up: How Is Treg Stability Maintained?
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