Effector T Cells Abrogate Stroma-Mediated Chemoresistance in Ovarian Cancer

Effector T cells and fibroblasts are major components in the tumor microenvironment. The means through which these cellular interactions affect chemoresistance is unclear. Here, we show that fibroblasts diminish nuclear accumulation of platinum in ovarian cancer cells, resulting in resistance to platinum-based chemotherapy. We demonstrate that glutathione and cysteine released by fibroblasts contribute to this resistance. CD8(+) T cells abolish the resistance by altering glutathione and cystine metabolism in fibroblasts. CD8(+) T-cell-derived interferon (IFN)γ controls fibroblast glutathione and cysteine through upregulation of gamma-glutamyltransferases and transcriptional repression of system xc(-) cystine and glutamate antiporter via the JAK/STAT1 pathway. The presence of stromal fibroblasts and CD8(+) T cells is negatively and positively associated with ovarian cancer patient survival, respectively. Thus, our work uncovers a mode of action for effector T cells: they abrogate stromal-mediated chemoresistance. Capitalizing upon the interplay between chemotherapy and immunotherapy holds high potential for cancer treatment.

Myeloid-Derived Suppressor Cells Endow Stem-like Qualities to Breast Cancer Cells through IL6/STAT3 and NO/NOTCH Cross-talk Signaling

Myeloid-derived suppressor cells (MDSC) contribute to immune suppression in cancer, but the mechanisms through which they drive metastatic progression are not fully understood. In this study, we show how MDSC convey stem-like qualities to breast cancer cells that coordinately help enable immune suppression and escape. We found that MDSC promoted tumor formation by enhancing breast cancer cell stem-like properties as well as by suppressing T-cell activation. Mechanistic investigations indicated that these effects relied upon cross-talk between the STAT3 and NOTCH pathways in cancer cells, with MDSC inducing IL6-dependent phosphorylation of STAT3 and activating NOTCH through nitric oxide leading to prolonged STAT3 activation. In clinical specimens of breast cancer, the presence of MDSC correlated with the presence of cancer stem-like cells (CSC) and independently predicted poor survival outcomes. Collectively, our work revealed an immune-associated mechanism that extrinsically confers cancer cell stemness properties and affects patient outcome. We suggest that targeting STAT3-NOTCH cross-talk between MDSC and CSC could offer a unique locus to improve cancer treatment, by coordinately targeting a coupled mechanism that enables cancer stemness and immune escape. Cancer Res; 76(11); 3156-65. ©2016 AACR.

PRC2 Epigenetically Silences Th1-Type Chemokines to Suppress Effector T-Cell Trafficking in Colon Cancer

Infiltration of tumors with effector T cells is positively associated with therapeutic efficacy and patient survival. However, the mechanisms underlying effector T-cell trafficking to the tumor microenvironment remain poorly understood in patients with colon cancer. The polycomb repressive complex 2 (PRC2) is involved in cancer progression, but the regulation of tumor immunity by epigenetic mechanisms has yet to be investigated. In this study, we examined the relationship between the repressive PRC2 machinery and effector T-cell trafficking. We found that PRC2 components and demethylase JMJD3-mediated histone H3 lysine 27 trimethylation (H3K27me3) repress the expression and subsequent production of Th1-type chemokines CXCL9 and CXCL10, mediators of effector T-cell trafficking. Moreover, the expression levels of PRC2 components, including EZH2, SUZ12, and EED, were inversely associated with those of CD4, CD8, and Th1-type chemokines in human colon cancer tissue, and this expression pattern was significantly associated with patient survival. Collectively, our findings reveal that PRC2-mediated epigenetic silencing is not only a crucial oncogenic mechanism, but also a key circuit controlling tumor immunosuppression. Therefore, targeting epigenetic programs may have significant implications for improving the efficacy of current cancer immunotherapies relying on effective T-cell-mediated immunity at the tumor site.

Epigenetic silencing of TH1-type chemokines shapes tumour immunity and immunotherapy

Epigenetic silencing including histone modifications and DNA methylation is an important tumorigenic mechanism¹ However, its role in cancer immunopathology and immunotherapy is poorly understood. Using ovarian cancers as our model, we found that enhancer of zeste homolog 2 (EZH2)-mediated histone H3 lysine 27 trimethylation (H3K27me3) and DNA methyltransferase (DNMT) 1-mediated DNA methylation repress the tumor production of Th1-type chemokines CXCL9 and CXCL10, and subsequently determine effector T cell trafficking to the tumor microenvironment. Treatment with epigenetic modulators removes the repression and increases effector T cell tumor infiltration, slows down tumor progression, and improves therapeutic efficacy of PD-L1 (B7-H1) checkpoint blockade^2–4 and adoptive T cell transfusion⁵ in tumor bearing mice. Moreover, tumor EZH2 and DNMT1 are negatively associated with tumor infiltrating CD8⁺ T cells and patient outcome. Thus, epigenetic silencing of Th1-type chemokine is a novel tumor immune evasion mechanism. Selective epigenetic reprogramming alters T cell landscape⁶ in cancer and may enhance clinical efficacy of cancer therapy.

Myeloid cells in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is highly associated with inflammation. Myeloid cells, including tumor-associated macrophages and myeloid-derived suppressor cells, are abundant in the HCC microenvironment and are often associated with poor prognosis. Myeloid cells in HCC play a vital role in supporting tumor initiation, progression, angiogenesis, metastasis, and therapeutic resistance. Here, we summarize our current knowledge about myeloid cells in HCC and focus on their immune-suppressive activities and tumor-promoting functions, as well as the relevance to potential new therapies in HCC.

Th22 cells control colon tumorigenesis through STAT3 and Polycomb Repression complex 2 signaling

Th22 cells traffic to and retain in the colon cancer microenvironment, and target core stem cell genes and promote colon cancer stemness via STAT3 and H3K79me2 signaling pathway and contribute to colon carcinogenesis. However, whether Th22 cells affect colon cancer cell proliferation and apoptosis remains unknown. We studied the interaction between Th22 cells and colon cancer cells in the colon cancer microenvironment. Colon cancer proliferation was examined by flow cytometry analysis and H(3) thymidine incorporation. Cell cycle related genes were quantified by real-time PCR and Western blotting. We transfected colon cancer cells with lentiviral vector encoding specific gene shRNAs and used chromatin immunoprecipitation (ChIP) assay to determine the genetic signaling involved in interleukin (IL)-22-mediated colon cancer cell proliferation. We showed that Th22 cells released IL-22 and stimulated colon cancer proliferation. Mechanistically, IL-22 activated STAT3, and subsequently STAT3 bound to the promoter areas of the Polycomb Repression complex 2 (PRC2) components SUZ12 and EED, and stimulated the expression of PRC2. Consequently, the activated PRC2 catalyzed the promoters of the cell cycle check-point genes p16 and p21, and inhibited their expression through H3K27me3-mediated histone methylation, and ultimately caused colon cancer cell proliferation. Bioinformatics analysis revealed that the levels of IL-22 expression positively correlated with the levels of genes controlling cancer proliferation and cell cycling in colon cancer. In addition to controlling colon cancer stemness, Th22 cells support colon carcinogenesis via affecting colon cancer cell proliferation through a distinct histone modification.

Abstract POSTER-BIOL-1332: Molecular, cellular and clinical interaction between MDSC and ovarian cancer stemness

Myeloid derived suppressor cells (MDSCs) and cancer stem cells (CSCs) are important cellular components in the cancer microenvironment, and may affect cancer phenotype and patient outcome. The nature of MDSCs and their interaction with CSCs in ovarian carcinoma are unclear. We examined the interaction between MDSCs and CSCs in patients with ovarian carcinoma. We demonstrate that MDSCs inhibit T cell activation, enhance CSC gene expression, sphere formation and cancer metastasis. MDSCs trigger microRNA101 expression in cancer cells; microRNA101 subsequently represses the co-repressor gene C-terminal binding protein-2 (CtBP2), and CtBP2 directly targets stem cell core genes resulting in increased cancer cell stemness, and increasing metastatic and tumorigenic potential. Increased MDSC density and tumor microRNA101 levels, and decreased tumor CtBP2 expression independently predict poor survival. Collectively, the work identifies a novel immune associated cellular, molecular and clinical network involving MDSCs/microRNA101/CtBP2/stem cell core genes, which extrinsically controls cancer stemness and impacts patient outcome.

Citation Format: Ilona Kryczek, Tracy X. Cui, Lili Zhao, Linda Vatan, Wojciech Szeliga, Rebecca Liu, Weiping Zou. Molecular, cellular and clinical interaction between MDSC and ovarian cancer stemness [abstract]. In: Proceedings of the 10th Biennial Ovarian Cancer Research Symposium; Sep 8-9, 2014; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2015;21(16 Suppl):Abstract nr POSTER-BIOL-1332.

Effector CD8+ T cells abrogate fibroblasts-mediated chemoresistance in ovarian cancer (TUM2P.1007)

Tumor infiltrating effector CD8+ T cells have been described to play a major role in antitumoral activity and to be a favorable prognostic factor in ovarian cancer. The strategies of immunotherapy to improve effector T cells response have also shown potential clinical benefit in subset of ovarian cancer patients. Currently platinum-based chemotherapy is still the most active regimen for ovarian cancer treatment. However, the therapeutic resistance is a major challenge to limit the therapeutic efficiency. Here we found primary fibroblasts isolated from ovarian tumor speciman could induce resistance against cisplatin in cancer cells when the two cell types were co-cultured in vitro or co-inoculated in vivo. Activated CD8+ T cells abolished fibroblasts-mediated cisplatin resistance through IFNγ secretion. Next, we found fibroblasts induced cisplatin resistance through increasing intracellular Glutathione (GSH) level and reducing the cisplatin accumulation in cancer cells. We also identified both intact GSH and Cysteine released by fibroblasts contributed to cisplatin resistance in cancer cells. IFNγ producted by activated CD8+ T cells promoted fibroblasts extracellular GSH degradation through up-regulation of Gamma-glutamyl transpeptidase, and also diminished Cysteine generation by fibroblasts through down-regulation of System xc⁻ cystine/glutamate antiporter.These date implicate effector T cells immunotherapy as a powerful regimen to overcome the resistance to chemotherapy.

Epigenetic silencing of Th1-type chemokines dictates effector T cell tumor trafficking and predicts patient outcome (TUM7P.1019)

Epigenetic silencing including histone modifications and DNA methylation is an important tumorigenic mechanism in cancer. However, its role in cancer immunopathology and immunotherapy is poorly understood. In this study, we focused on the infiltration of effector T lymphocytes into ovarian tumor and established the histone H3 lysine 27 trimethylation (H3K27me3) and DNA hypermethylation as epigenetic silencing mechanisms regulating Th1-type chemokines CXCL9 and CXCL10 production. We found that a polycomb group (PcG) protein, enhancer of zeste 2 homolog (EZH2)-based histone H3 lysine 27 trimethylation (H3K27me3) alone or in collaboration with DNA methyltransferases (DNMTs) selectively control the tumor production of CXCL9 and CXCL10, and subsequently determine effector T cell trafficking to the tumor microenvironment. Treatment with epigenetic modulators removes the repression and increases effector T cell tumor infiltration, slows down tumor progression, and improves therapeutic efficacy of PDL1(B7-H1) checkpoint blockade and adoptive T cell transfusion. Moreover, tumor EZH2 and DNMT1 are negatively associated with tumor infiltrating CD8+ T cells and patient outcome. Our results indicate that epigenetic silencing of Th1-type chemokine is a novel tumor immune evasion mechanism. Selective epigenetic reprogramming alters T cell landscape in cancer and enhances clinical efficacy of cancer therapy.

TNFα-induced epigenetic modifications support a DC1 program in dendritic cells during protective immunity to cryptococcal infection (MPF4P.732)

TNFα is required for protective Th1 immunity to Cryptococcus neoformans (Cneo) and these effects are linked to the stable, early classical activation of dendritic cells (DC1), preventing alternative (DC2) activation. We hypothesized that TNFα stabilizes DC1 DC by inducing epigenetic modification of key DC1 genes. We modeled TNFα-stabilized DC (TSDC) in vitro by treating DC with DC1-skewing IFNγ +/- TNFα followed by a switch to DC2-skewing IL-4, and we assessed transcriptional and epigenetic signatures. Epigenetic studies focused on histone 3 methylation at lysines 4, 9 and 27 (H3K4, 9 or 27, respectively). H3K4 methylation is associated with activation of proximal genes, but H3K9 and 27 methylations are associated with repression. TSDC showed resistance to induction of DC2 genes and increased transcript levels of the key histone methyltransferases G9a (H3K9), EZH2 (H3K27) and MLL1 (H3K4). Further, we performed ChIP on TSDC and found that IL12b and IFNγ promoters are associated with the activating H3K4 methylation while non-stabilized DC1 and DC2 were not. We next assessed EZH2, G9a, and MLL1 transcript levels and the global methylation state of H3K4 in Cneo-infected lungs and found that both mRNA transcript levels and H3K4 methylation increased significantly in control but not TNFα-depleted mice. We conclude that histone modifications in DC are significantly altered by TNFα, and that this correlates with increased DC1 stability during protective responses to Cneo infection.

Cancer mediates effector T cell dysfunction by targeting microRNAs and EZH2 via glycolysis restriction (TUM9P.1007)

Aerobic glycolysis regulates T cell function. However, if and how primary cancer alters effector T cell glycolytic metabolism and affects tumor immunity remains a question in cancer patients. Here we report that ovarian cancer imposes glucose restriction on effector T cells, dampens their function via maintaining high expression of microRNA101 and microRNA26a, which subsequently constrains EZH2 expression. EZH2 activates the Notch pathway by suppressing Notch repressors via H3K27me3, and consequently stimulates T cell polyfunctional cytokine expression and promotes their survival via Bcl-2 signaling. Moreover, EZH2-/- T cells elicit poor anti-tumor immunity and EZH2+CD8+ T cells are associated with improved long-term cancer patient survival. Together, our data unveil a novel metabolic target and mechanism of cancer immune evasion.

IL-22+CD4+ T cells promote colorectal cancer stemness via STAT3 transcription factor activation and induction of the methyltransferase DOT1L (TUM10P.1022)

Little is known about how the immune system impacts human colorectal cancer invasiveness and stemness. Here we detected interleukin-22 (IL-22) in patient colorectal cancer tissues that was produced predominantly by CD4+ T cells. In a mouse model, migration of these cells into the colon cancer microenvironment required the chemokine receptor CCR6 and its ligand CCL20. IL-22 acted on cancer cells to promote activation of the transcription factor STAT3 and expression of the histone 3 lysine 79 (H3K79) methytransferase DOT1L. The DOT1L complex induced the core stem cell genes NANOG, SOX2, and Pou5F1, resulting in increased cancer stemness and tumorigenic potential. Furthermore, high DOT1L expression and H3K79me2 in colorectal cancer tissues was a predictor of poor patient survival. Thus, IL-22+ cells promote colon cancer stemness via regulation of stemness genes that negatively affects patient outcome. Efforts to target this network might be a strategy in treating colorectal cancer patients.

IL-22 induces colon cancer proliferation through STAT3 and PRC2 signaling (TUM10P.1036)

Background: IL-22(interleukin-22) is a newly identified cytokine which has been recently highlighted owing to its biological significance in carcinogenesis. However, the role of IL-22 in colon cancer proliferation has remained unclear. Since both JAK-STAT signaling and Polycomb Repression complex (PRC) 2 play crucial roles in epithelial proliferation. We investigated the mechanism by which IL-22 induces colon cancer proliferation. Methods: Colon cancer cells proliferation was detected by FACS and H3 Thymidine Incorporation. Cell cycle related genes were tested by Real-Time PCR. Lentiviral vector encoding gene specific shRNAs (STAT3, EZH2, SUZ12) and scramble particles were used to transfect colon cancer cells. ChIP assays were performed to detect the binding of different proteins and DNA. Results: IL-22 significantly induces colon cancer cells proliferation through STAT3 signaling. This increased proliferation involved the inhibition of p16 and p18 through aberrant promoter histone methylation H3K27me3. PRC2 catalyzes promoter H3K27me3 of p16 and p18, which can be up-regulated by IL-22. Furthermore, STAT3 can bind to PRC2 members (SUZ12 and EED), which also can be up-regulated by IL-22 stimulation. Conclusion: IL-22 can induce human colon cancer cells proliferation by activation of STAT3, which was phosphorylated and directed bind to the PRC2 complex, especially SUZ12 and EED, and consequently catalyzed the H3K27m3 of cell cycle check-point genes p16 and p18.

Tumor-associated macrophages produce interleukin 6 and signal via STAT3 to promote expansion of human hepatocellular carcinoma stem cells

BACKGROUND & AIMS

Cancer stem cells (CSCs) can contribute to hepatocellular carcinoma (HCC) progression and recurrence after therapy. The presence of tumor-associated macrophages (TAMs) in patients with HCC is associated with poor outcomes. It is not clear whether TAMs interact with CSCs during HCC development. We investigated whether TAMs affect the activities of CSCs in the microenvironment of human HCCs.

METHODS

HCCs were collected from 17 patients during surgical resection and single-cell suspensions were analyzed by flow cytometry. CD14(+) TAMs were isolated from the HCC cell suspensions and placed into co-culture with HepG2 or Hep3B cells, and CSC functions were measured. The interleukin 6 (IL6) receptor was blocked with a monoclonal antibody (tocilizumab), and signal transducer and activator of transcription 3 was knocked down with small hairpin RNAs in HepG2 cells. Xenograft tumors were grown in NOD-SCID/Il2Rg(null) mice from human primary HCC cells or HepG2 cells.

RESULTS

CD44(+) cells from human HCCs and cell lines formed more spheres in culture and more xenograft tumors in mice than CD44(-) cells, indicating that CD44(+) cells are CSCs. Incubation of the CD44(+) cells with TAMs promoted expansion of CD44(+) cells, and increased their sphere formation in culture and formation of xenograft tumors in mice. In human HCC samples, the numbers of TAMs correlated with the numbers of CD44(+) cells. Of all cytokines expressed by TAMs, IL6 was increased at the highest level in human HCC co-cultures, compared with TAMs not undergoing co-culture. IL6 was detected in the microenvironment of HCC samples and induced expansion of CD44(+) cells in culture. Levels of IL6 correlated with stages of human HCCs and detection of CSC markers. Incubation of HCC cell lines with tocilizumab or knockdown of signal transducer and activator of transcription 3 in HCC cells reduced the ability of TAMs to promote sphere formation by CD44+ cells in culture and growth of xenograft tumors in mice.

CONCLUSIONS

CD44(+) cells isolated from human HCC tissues and cell lines have CSC activities in vitro and form a larger number of xenograft tumors in mice than CD44(-) cells. TAMs produce IL6, which promotes expansion of these CSCs and tumorigenesis. Levels of IL6 in human HCC samples correlate with tumor stage and markers of CSCs. Blockade of IL6 signaling with tocilizumab, a drug approved by the Food and Drug Administration for treatment of rheumatoid arthritis, inhibits TAM-stimulated activity of CD44(+) cells. This drug might be used to treat patients with HCC.

Abstract 4078: EZH2 marks polyfunctional memory T cells and controls tumor immunity

Polyfunctional T cells mediate potent anti-viral immunity. However, the nature and molecular mechanisms controlling their functional signature remain poorly understood. Here we report that polyfunctional T cells are characterized by high proliferative capacity and apoptotic resistance. Enhancer of zeste homolog 2 (EZH2) phenotypically marks them and functionally controls their survival and expansion. Notch signaling regulates effector T cell function. We show that EZH2 represses Numb and Fbxw7, two Notch repressors, activates Notch signaling, and Notch subsequently stimulates Bcl-2 expression and protects EZH2+ T cells from apoptosis via trimethylating histone H3 on lysine 27. Moreover, EZH2 targets T cell cycling repressors and promotes their expansion. EZH2+CD8+ T cells mediate anti-tumor immunity and are associated with improved long-term cancer survival. Together, the data reveal a novel role and mechanism for EZH2 in controlling polyfunctional T cells. Thus, manipulation of EZH2 signaling in T cells may have therapeutic potential in treating cancer patients.

Citation Format: Ende Zhao, Tomasz Maj, Ilona Kryczek, Lili Zhao, Shuang Wei, Shanshan Wan, Joel Crespo, Wojciech Szeliga, Linda Vatan, Ke Wu, Arul M. Chinnaiyan, Theodore H. Welling, Victor E. Marquez, Jan Kotarski, Yi Zhang, Rebecca Liu, Kaixiong Tao, Guobin Wang, Weiping Zou. EZH2 marks polyfunctional memory T cells and controls tumor immunity. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4078. doi:10.1158/1538-7445.AM2014-4078

Decreased expression of CXCR4 chemokine receptor in bone marrow after chemotherapy in patients with non-Hodgkin lymphomas is a good prognostic factor

Background

CXCR4 chemokine receptor is constitutively expressed on normal and malignant B lymphocytes derived from patients with B-cell lymphoproliferative disorders and has a significant role in cell migration to lymph nodes and bone marrow. Non-Hodgkin's lymphomas (NHL) constitute a heterogeneous group of lymphoproliferative diseases, which can localize not only to lymph nodes, but also can migrate to peripheral blood and metastase to other organs, including bone marrow.

Aim

The purpose of this study was to determine CXCR4 gene expression in peripheral blood and bone marrow of NHL patients before and after treatment.

Methods

Samples of lymphoma lymph nodes, peripheral blood and bone marrow aspirates of patients with B-cell NHL were taken at diagnosis and after chemotherapy. Gene expression was determined by the reverse transcription (RT)-polymerase chain reaction method. Expression was estimated from 0 AU (no amplificate signal) to 3 AU (maximal amplificate signal).

Results

No significant difference in the level of CXCR4 expression was found in reactive lymph nodes compared to lymphoma samples We observed high level of CXCR4 expression in most patients before treatment: in bone marrow: 3 AU-10 pts, 2 AU–8 pts, 1 AU–2 pts. In peripheral blood: 3 AU–14 pts, 2 AU–4 pts, 1 AU–1 pts, 0 AU–1 pts. After chemotherapy, significant decrease in CXCR4 expression was observed. Bone marrow: 3 AU–5 pts, 2 AU–7 pts, 1 AU–5 pts, 0 AU–3 pts (p = 0.03). Peripheral blood: 3 AU–2 pts, 2 AU–6 pts, 1 AU–10 pts, 0 AU–2 pts (p = 0.0002). There was a good response to treatment in patients with significant decrease of CXCR4 expression in the bone marrow after treatment with 10-fold lower risk of death (p = 0.03).

Conclusions

Decrease in CXCR4 expression in the bone marrow of NHL patients after chemotherapy may be a good prognostic factor.

IL-22(+)CD4(+) T cells promote colorectal cancer stemness via STAT3 transcription factor activation and induction of the methyltransferase DOT1L

Little is known about how the immune system impacts human colorectal cancer invasiveness and stemness. Here we detected interleukin-22 (IL-22) in patient colorectal cancer tissues that was produced predominantly by CD4(+) T cells. In a mouse model, migration of these cells into the colon cancer microenvironment required the chemokine receptor CCR6 and its ligand CCL20. IL-22 acted on cancer cells to promote activation of the transcription factor STAT3 and expression of the histone 3 lysine 79 (H3K79) methytransferase DOT1L. The DOT1L complex induced the core stem cell genes NANOG, SOX2, and Pou5F1, resulting in increased cancer stemness and tumorigenic potential. Furthermore, high DOT1L expression and H3K79me2 in colorectal cancer tissues was a predictor of poor patient survival. Thus, IL-22(+) cells promote colon cancer stemness via regulation of stemness genes that negatively affects patient outcome. Efforts to target this network might be a strategy in treating colorectal cancer patients.

Th22 cells shape colorectal cancer stemness via epigenetic regulation (TUM2P.877)

Little is known about the direct impact of immune elements on human colorectal cancer invasiveness and stemness. We investigated the interaction between IL-22+ cells and cancer (stem) cells in colorectal cancer patients. We have demonstrated that Th22-derived IL-22 targets disruptor of telomeric silencing 1-like (DOT1L). DOT1L methylates histone 3 lysine 79 (H3K79) and, in turn, leads to core stem cell gene activation, resulting in increased colon cancer stemness and tumorigenic potential. In addition, increased levels of DOT1L and H3K79me2 in colorectal cancer predict poor patient survival. Collectively, this work identifies that Th22 cells control colon cancer stemness via epigenetic regulation that affects patient outcome. Efforts to target this network might be a strategy in treating patients with colorectal cancer.

Denileukin diftitox depletes regulatory T cells without clinical benefit in advanced stage epithelial ovarian carcinoma (VAC3P.945)

Denileukin diftitox (DT) depletes regulatory T cells (Treg) that correlates with immune and clinical benefits in metastatic human melanoma and improved clinical outcomes in a renal cancer vaccine trial. We tested immune and clinical effects of Treg depletion using DT in a phase 0/I cancer trial and a phase II ovarian cancer trial. In our phase 0/I trial, we noted reductions in blood Treg prevalence and concentration (median ~18% and ~50%, respectively) 3-7 days after one intravenous DT infusion at 9 or 12 μg/kg, in 6 of 7 evaluable patients with breast, lung, and ovarian cancers, and melanoma, and increased blood IFN-γ+ and Ki-67+ T cells. Weekly DT significantly reduced metastatic tumors in one ovarian cancer patient prompting a small phase II trial in epithelial ovarian cancers. 28 patients received DT once every 3-4 weeks which significantly depleted functional Tregs from blood and the tumor microenvironment, but with variable immune outcomes and no significant clinical efficacy. Weekly DT eventually reduced effector T cells. In mouse ovarian cancer models we found that: i) DT efficacy depended on adaptive immunity, ii) its IL-2 moiety did not mediate clinical effects, and iii) its treatment mechanism appeared distinct from anti-CD25 antibody, which depleted Tregs in a human breast cancer trial. DT depletes Tregs in various carcinomas but requires more dosing and schedule studies. Treg-specific agents and combination treatments could also improve Treg depletion efficacy.

Myeloid-derived suppressor cells enhance stemness of cancer cells by inducing microRNA101 and suppressing the corepressor CtBP2

Myeloid-derived suppressor cells (MDSCs) and cancer stem cells (CSCs) are important cellular components in the cancer microenvironment and may affect cancer phenotype and patient outcome. The nature of MDSCs and their interaction with CSCs in ovarian carcinoma are unclear. We examined the interaction between MDSCs and CSCs in patients with ovarian carcinoma and showed that MDSCs inhibited T cell activation and enhanced CSC gene expression, sphere formation, and cancer metastasis. MDSCs triggered miRNA101 expression in cancer cells. miRNA101 subsequently repressesed the corepressor gene C-terminal binding protein-2 (CtBP2), and CtBP2 directly targeted stem cell core genes resulting in increased cancer cell stemness and increasing metastatic and tumorigenic potential. Increased MDSC density and tumor microRNA101 expression predict poor survival, as does decreased tumor CtBP2 expression, independent of each other. Collectively, our work identifies an immune-associated cellular, molecular, and clinical network involving MDSCs-microRNA101-CtBP2-stem cell core genes, which extrinsically controls cancer stemness and impacts patient outcome.

The immune system and cancer stemness cross-talk can predict therapeutic response and patient outcome (P3030)

Myeloid-derived suppressor cells (MDSCs) inhibit anti-tumor immunity. However, their involvement in cancer stem cell (CSC) biology, and their molecular, clinical and therapeutic relevance of this involvement have not been studied. Here, we investigated MDSCs in human breast cancer. We show that MDSCs prompt breast cancer stemness through enhance CSC gene expression, sphere formation and cancer metastasis. The effects depend on the cross-talk between interleukin (IL)-6/signal transducer and activator of transcription 3 (STAT3) and nitric oxide (NO)/NOTCH signaling pathways. MDSCs initiate STAT3 phosphorylation through IL-6, and activate Notch and sustain prolonged STAT3 phosphorylation via NO in CSCs. Furthermore, MDSCs positively correlate with CSC numbers and signature genes in breast cancer, and serve as a negative predictor for patient survival and herceptin response. Collectively, our study has revealed novel extrinsic cellular and molecular mechanisms controlling cancer stemness, and suggests that targeting both MDSCs and cancer is essential for engendering potent therapeutic efficacy in cancer patients. Efforts to target this network might be a valuable strategy in anti-cancer therapy.

Human Th17 cells have stem cell-like features and promote long-term tumor immunity (122.10)

Th17 cells play a role in multiple pathological scenarios. However, their functional phenotype, self-renewal potential, survival pattern and the underlying controlling mechanisms are poorly investigated. Now we have studied Th17 cells in the pathological microenvironments of GVHD, ulcerative colitis and cancer in humans. Th17 cells are increased in the chronic phase of these diseases. Despite their phenotypic markers of terminal differentiation, in vivo adoptive transfusing experiments demonstrate that Th17 cells mediate long-term anti-tumor immunity. Th17 cells have stem cell-like features including high capacity of proliferative self-renewal, potent persistence and apoptotic resistance in vivo, and the generation of other types of T helper cells and express high levels of multiple core stem cell genes and anti-apoptotic genes. We demonstrate that their stem cell-like characters are regulated collaboratively by HIF-1α and Notch. Our data indicate that human Th17 cells may be a long-lived proliferating T cell population with stem cell characters.

Abstract 3534: Human Th17 cells have stem cell-like features and promote long-term tumor immunity

Th17 cells play a role in multiple pathological scenarios. However, their functional phenotype, survival pattern and the underlying controlling mechanisms are poorly investigated in humans. This significantly hampers clinical application of targeting Th17 cells. Now we have studied Th17 cells in the pathological microenvironments of graft-versus-host disease, ulcerative colitis and cancer in humans. Th17 cells are increased in the chronic phase of these diseases. Th17 cells phenotypically resemble to terminally differentiated memory T cells, but are different from central memory, exhausted and senescent T cells. Despite their phenotypic markers of terminal differentiation, in vivo adoptive transfusing experiments demonstrate that Th17 cells mediate and promote long-term anti-tumor immunity. Furthermore, Th17 cells have important functional features including high capacity of proliferative self-renewal, potent persistence and apoptotic resistance in vivo, and the plasticity of converting into other types of T helper cells. These features are accompanied with relatively specific gene signature in Th17 cells including abundant anti-apoptotic genes. Moreover, we investigated the molecular mechanisms controlling their functional characters. We demonstrate that hypoxia inducible factor (HIF)1α and Notch collaboratively control key anti-apoptosis Bcl-2 family gene expression and function in Th17 cells. Altogether, the data indicate that human Th17 cells may be a long-lived proliferating effector memory T cell population with unique genetic and functional characters. These characters may be important determinants in Th17 cell biology. Targeting Th17-associated signaling pathway would be therapeutically meaningful for treating patients with autoimmune disease and advanced tumor.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3534. doi:1538-7445.AM2012-3534

Human TH17 cells are long-lived effector memory cells

T helper 17 (TH17) cells have been shown to contribute to multiple disease systems. However, the functional phenotype and survival pattern of TH17 cells as well as the underlying mechanisms that control TH17 cells have been poorly investigated in humans, significantly hampering the clinical targeting of these cells. Here, we studied human TH17 cells in the pathological microenvironments of graft-versus-host disease, ulcerative colitis, and cancer; TH17 cell numbers were increased in the chronic phase of these diseases. Human TH17 cells phenotypically resembled terminally differentiated memory T cells but were distinct from central memory, exhausted, and senescent T cells. Despite their phenotypic markers of terminal differentiation, TH17 cells mediated and promoted long-term antitumor immunity in in vivo adoptive transfer experiments. Furthermore, TH17 cells had a high capacity for proliferative self-renewal, potent persistence, and apoptotic resistance in vivo, as well as plasticity-converting into other types of TH cells. These cells expressed a relatively specific gene signature including abundant antiapoptotic genes. We found that hypoxia-inducible factor-1α and Notch collaboratively controlled key antiapoptosis Bcl-2 family gene expression and function in TH17 cells. Together, these data indicate that human TH17 cells may be a long-lived proliferating effector memory T cell population with unique genetic and functional characteristics. Targeting TH17-associated signaling pathway would be therapeutically meaningful for treating patients with autoimmune disease and advanced tumor.

Endogenous interleukin-10 constrains Th17 cells in patients with inflammatory bowel disease

Background

Th17 cells play a role in inflammation. Interleukin (IL)-10 is a potent anti-inflammatory cytokine. However, it is poorly understood whether and how endogenous IL-10 impacts the development of Th17 cells in human pathologies.

Materials and methods

We examined the relationship between IL-10 and Th17 cells in patients with Crohn's disease and in IL-10-deficient (IL-10^-/-) mice. Th17 cells and dendritic cells (DCs) were defined by flow cytometry and evaluated by functional studies.

Results

We detected elevated levels of IL-17 and Th17 cells in the intestinal mucosa of patients with Crohn's disease. Intestinal DCs from Crohn's patients produced more IL-1β than controls and were superior to blood DCs in Th17 induction through an IL-1-dependent mechanism. Furthermore, IL-17 levels were negatively associated with those of IL-10 and were positively associated those of IL-1β in intestinal mucosa. These data point toward an in vivo cellular and molecular link among endogenous IL-10, IL-1, and Th17 cells in patients with Crohn's disease. We further investigated this relationship in IL-10^-/- mice. We observed a systemic increase in Th17 cells in IL-10^-/- mice when compared to wild-type mice. Similar to the intestinal DCs in patients with Crohn's disease, murine IL-10^-/- DCs produced more IL-1β than their wild-type counterparts and promoted Th17 cell development in an IL-1-dependent manner. Finally, in vivo blockade of IL-1 receptor signaling reduced Th17 cell accumulation and inflammation in a mouse model of chemically-induced colitis.

Conclusions

Endogenous IL-10 constrains Th17 cell development through the control of IL-1 production by DCs, and reaffirms the crucial anti-inflammatory role of IL-10 in patients with chronic inflammation.

Interleukin-10 ablation promotes tumor development, growth, and metastasis

Interleukin-10 (IL-10) is a broadly acting immune inhibitory cytokine that is generally thought to support tumor growth. Here we challenge this view with evidence that genetic ablation of IL-10 in the mouse significantly heightens sensitivity to chemical carcinogenesis, growth of transplanted tumors, and formation of metastases. Tumor growth in IL-10-deficient (IL-10(-/-)) mice was associated with an increased level of myeloid-derived suppressor cells (MDSC) and CD4(+)Foxp3(+) regulatory T (Treg) cells in both the tumor microenvironment and the tumor-draining lymph nodes. IL-10(-/-) MDSCs express high levels of MHC and IL-1, and they efficiently induced formation of Treg cells. IL-1 signaling blockade reduced tumor growth mediated by IL-10 deficiency, associated with a partial rescue of tumor infiltration and function of effector T cells and a decrease in tumor angiogenesis and tumor infiltration by Treg cells. Taken together, our findings establish that endogenous IL-10 inhibits inflammatory cytokine production and hampers the development of Treg cells and MDSCs, two key components of the immunosuppressive tumor microenvironment, thereby inhibiting tumor development, growth, and metastasis.

Dual biological effects of the cytokines interleukin-10 and interferon-γ

It is generally thought that each cytokine exerts either immune stimulatory (inflammatory) or immune inhibitory (antiinflammatory or regulatory) biological activities. However, multiple cytokines can enact both inhibitory and stimulatory effects on the immune system. Two of these cytokines are interleukin (IL)-10 and interferon-gamma (IFNγ). IL-10 has demonstrated antitumor immunity even though it has been known for years as an immunoregulatory protein. Generally perceived as an immune stimulatory cytokine, IFNγ can also induce inhibitory molecule expression including B7-H1 (PD-L1), indoleamine 2,3-dioxygenase (IDO), and arginase on multiple cell populations (dendritic cells, tumor cells, and vascular endothelial cells). In this review, we will summarize current knowledge of the dual roles of both of these cytokines and stress the previously underappreciated stimulatory role of IL-10 and inhibitory role of IFNγ in the context of malignancy. Our progressive understanding of the dual effects of these cytokines is important for dissecting cytokine-associated pathology and provides new avenues for developing effective immune therapy against human diseases, including cancer.

Antigen-presenting cell (APC) subsets in ovarian cancer

The major human antigen-presenting cells (APCs) include monocytes/macrophages, myeloid dendritic cells (mDC), plasmacytoid dendritic cells (pDC), and B cells. These APC subsets have been observed in ovarian tumor environments. Their phenotypes and functionalities are subjected to alteration by multiple factors in the tumor environment. In this review, we summarize the nature, cellular interactions, and prognostic significance of the main APC populations in ovarian cancer, and discuss the relevance of manipulating APC subsets for patient treatment.

Abstract 2450: Resistance of CD44+ hepatocellular carcinoma cancer stem cellsto immune effector responses

Hepatocellular carcinoma (HCC) is a common cause of cancer-related deaths worldwide. There is little therapy for advanced disease and recurrence rates can be as high as 50% following resection. Evidence in several tumor types suggests that cancer stem cells (CSCs) contribute to tumorigenicity, therapeutic resistance and recurrence, however the HCC CSC phenotype remains to be completely defined. HCC recurrence is influenced by the degree of immune response in the tumor microenvironment. Therefore, we aimed to characterize HCC-CSCs phenotype and investigate the interaction between CSCs and immune cell subsets.

To identify a dominant CSC population in HCC, we examined several putative CSC markers, including CD44, CD90, CD133 and EpCAM on primary human resected HCCs (n=6), HCC xenografts (n=2), and HCC cell lines (n=3) using flow cytometry. Cells from all sources consistently showed discrete populations of CD44+ cells (2-40%), while other common CSC markers showed significant heterogeneity. CD44+ cells isolated from HCC xenografts or HepG2 cells by fluorescence-activated cell sorting (FACS) demonstrated enhanced tumorigenic potential with as little as 100 cells implanted into NOD-SCID/IL-2Rgnull mice compared to no tumor from 100 CD44− cells. CD44+ cells were also able to produce heterogenic tumor mass in vivo. Moreover, CD44+ cells demonstrated increased sphere forming capacity in serum free media (2 fold, p<0.05), and increased resistance to the chemotherapeutic agents cisplatin and doxorubicin in vitro. Additionally, CD44+ HCC cells were resistant to effector cytokines such as IFNγ and TNFα and effector responses during co-culture with anti-CD3/anti-CD28 activated T cells from healthy donor PBMCs. CD44+ HCC cells had 2-fold increased expression of B7-H1, a co-inhibitory molecule for T cells, when compared to non-CSCs during exposure to activated T cells or effector cytokine IFNγ, suggesting a possible mechanism of resistance to immune effectors in the HCC microenvironment.

In conclusion, CD44 discriminates for the HCC CSC as evidenced by CD44+ subset demonstrating enhanced tumorigenicity, sphere forming capacity and resistance to chemotherapeutic agents. CD44+ CSC are also resistant to activated T cells and effector cytokines suggesting that microenvironmental factors related to immune response may be important for HCC recurrence or progression.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2450. doi:10.1158/1538-7445.AM2011-2450

Expression of aldehyde dehydrogenase and CD133 defines ovarian cancer stem cells

Identification of cancer stem cells is crucial for advancing cancer biology and therapy. Several markers including CD24, CD44, CD117, CD133, the G subfamily of ATP-binding cassette transporters (ABCG), epithelial specific antigen (ESA) and aldehyde dehydrogenase (ALDH) are used to identify and investigate human epithelial cancer stem cells in the literature. We have now systemically analyzed and compared the expression of these markers in fresh ovarian epithelial carcinomas. Although the expression levels of these markers were unexpectedly variable and partially overlapping in fresh ovarian cancer cells from different donors, we reliably detected important levels of CD133 and ALDH in the majority of fresh ovarian cancer. Furthermore, most of these stem cell markers including CD133 and ALDH were gradually lost following in vitro passage of primary tumor cells. However, the expression of ALDH and CD133, but not CD24, CD44 and CD117, could be partially rescued by the in vitro serum-free and sphere cultures and by the in vivo passage in the immune-deficient xenografts. ALDH+ and CD133+ cells formed three-dimensional spheres more efficiently than their negative counterparts. These sphere-forming cells expressed high levels of stem cell core gene transcripts and could be expanded and form additional spheres in long-term culture. ALDH+ , CD133+ and ALDH+ CD133+ cells from fresh tumors developed larger tumors more rapidly than their negative counterparts. This property was preserved in the xenografted tumors. Altogether, the data suggest that ALDH+ and CD133+ cells are enriched with ovarian cancer-initiating (stem) cells and that ALDH and CD133 may be widely used as reliable markers to investigate ovarian cancer stem cell biology.

IL-17+ regulatory T cells in the microenvironments of chronic inflammation and cancer

Foxp3(+)CD4(+) regulatory T (Treg) cells inhibit immune responses and temper inflammation. IL-17(+)CD4(+) T (Th17) cells mediate inflammation of autoimmune diseases. A small population of IL-17(+)Foxp3(+)CD4(+) T cells has been observed in peripheral blood in healthy human beings. However, the biology of IL-17(+)Foxp3(+)CD4(+) T cells remains poorly understood in humans. We investigated their phenotype, cytokine profile, generation, and pathological relevance in patients with ulcerative colitis. We observed that high levels of IL-17(+)Foxp3(+)CD4(+) T cells were selectively accumulated in the colitic microenvironment and associated colon carcinoma. The phenotype and cytokine profile of IL-17(+)Foxp3(+)CD4(+) T cells was overlapping with Th17 and Treg cells. Myeloid APCs, IL-2, and TGF-β are essential for their induction from memory CCR6(+) T cells or Treg cells. IL-17(+)Foxp3(+)CD4(+) T cells functionally suppressed T cell activation and stimulated inflammatory cytokine production in the colitic tissues. Our data indicate that IL-17(+)Foxp3(+) cells may be "inflammatory" Treg cells in the pathological microenvironments. These cells may contribute to the pathogenesis of ulcerative colitis through inducing inflammatory cytokines and inhibiting local T cell immunity, and in turn may mechanistically link human chronic inflammation to tumor development. Our data therefore challenge commonly held beliefs of the anti-inflammatory role of Treg cells and suggest a more complex Treg cell biology, at least in the context of human chronic inflammation and associated carcinoma.

Th17 cells in cancer: help or hindrance?

The role of CD4+ T helper (Th) 17 cells in malignancy is currently under debate. However, upon closer scrutiny, it becomes apparent that this discussion includes not only evaluations of Th17 cells but also IL-17+ cells from other immune populations, the cytokine interleukin (IL)-17 itself (both endogenous and exogenous) and IL-23. Further complicating the matter are occasionally conflicting results of studies in humans versus those in mice and contradictory data from immunocompetent versus immunodeficient mice. To better understand the role of Th17 cells in the tumor-bearing host, we focus first upon those studies investigating Th17 cells in patients and then those in mice, all the while keeping in mind that variables such as tumor-initiating agents, a pre-existing inflammatory environment and the immune competence of the host may have direct effects upon this T-cell subset. In this review, we will describe the phenotype of tumor-associated Th17 cells, review those studies that have examined the population directly, and finally, briefly discuss the studies involving Th17-associated signature cytokines.

Kupffer cell suppression of CD8+ T cells in human hepatocellular carcinoma is mediated by B7-H1/programmed death-1 interactions

B7-H1 is a recently identified B7 family member that, along with one of its receptors, programmed death-1 (PD-1), has been involved in multiple immunopathologic scenarios. However, the nature of B7-H1 and PD-1 in human hepatocellular carcinoma (HCC) remains poorly defined. We investigated the expression and functional relevance of this pathway in patients with HCC. We showed that B7-H1 expression on Kupffer cells (KC) was increased in tumor tissues compared with surrounding nontumor liver tissues in patients with HCC and this correlated with poorer survival. Coculture of HCC cells with monocytes showed that tumor-associated interleukin-10 contributed to the induction of B7-H1 in the HCC environment. We further observed that the levels of PD-1(+)CD8(+) T cells were higher in tumor tissues than in nontumor tissues. B7-H1(+) KCs and PD-1(+) T cells were colocalized in the HCC stroma. PD-1(+)CD8(+) T cells had decreased proliferative ability and effector function as shown by reduced granule and cytokine expression compared with PD-1(-) T cells. Importantly, blocking KC B7-H1 interaction with PD-1(+)CD8(+) cells using neutralizing antibodies recovered effector T-cell function. Our data indicate that the B7-H1/PD-1 axis contributes to immune suppression in human HCC, with blockade of this pathway carrying important therapeutic implications.

FOXP3 defines regulatory T cells in human tumor and autoimmune disease

Activated T cells may express FOXP3. It is thought that FOXP3 is not a specific marker to determine regulatory T cells (Treg) in humans. Here, we examined the functional phenotype and cytokine profile of the in vitro induced FOXP3(+) T cells, primary FOXP3(+) and FOXP3(-) T cells in patients with ulcerative colitis and tumors including colon carcinoma, melanoma, hepatic carcinoma, ovarian carcinoma, pancreatic cancer, and renal cell carcinoma. We observed similar levels of suppressive capacity of primary FOXP3(+) T cells in blood, tumors, and colitic tissues. Compared with primary FOXP3(-) T cells in the same microenvironment, these primary FOXP3(+) T cells expressed minimal levels of effector cytokines, negligible amount of cytotoxic molecule granzyme B, and levels of suppressive molecules interleukin-10 and PD-1. Although the in vitro activated T cells expressed FOXP3, these induced FOXP3(+) T cells expressed high levels of multiple effector cytokines and were not functionally suppressive. The data reinforce the fact that FOXP3 remains an accurate marker to define primary Tregs in patients with cancer and autoimmune disease. We suggest that the combination of FOXP3 and cytokine profile is useful for further functionally distinguishing primary Tregs from activated conventional T cells.

Cutting edge: IFN-gamma enables APC to promote memory Th17 and abate Th1 cell development

Th1-derived IFN-gamma targets naive T cells and inhibits Th17 development. However, Th1, Th17, and memory but not naive T cells are colocalized in an inflammatory environment. To demonstrate the kinetic relationship between these T cell subsets, we investigated the role of IFN-gamma in regulating the development and balance between Th17 and Th1 in humans. We show that IFN-gamma stimulates B7-H1 expression on APC subsets and abates their Th1 polarization capacity in a B7-H1-dependent manner. Interestingly, IFN-gamma triggers APCs to produce IL-1 and IL-23 and enables them to induce memory Th17 expansion via IL-1 and IL-23 in a B7-H1-independent manner. We propose a novel dynamic between Th1 and Th17 in the course of inflammation as follows: Th1-mediated inflammation is attenuated by IFN-gamma-induced B7-H1 on APCs and is evolved toward Th17-mediated chronic inflammation by IFN-gamma-induced, APC-derived IL-1 and IL-23. Our study challenges the dogma that IFN-gamma suppresses Th17 and enhances Th1 development.

Altering regulatory T cell function in cancer immunotherapy: a novel means to boost the efficacy of cancer vaccines

Cancers express tumor associated antigens that should elicit immune attack, but spontaneous immune rejection of established cancer is rare. Recent data demonstrate that specific and active tumor-mediated mechanisms hinder host anti-tumor immunity. CD4+CD25+ T regulatory cells (Tregs) are important mediators of active immune evasion in cancer. Disrupting tumor-mediated mechanisms hindering host immunity is a novel approach to tumor immunotherapy. Treg depletion improves endogenous anti-tumor immunity and the efficacy of active immunotherapy in animal models for cancer, suggesting that inhibiting Treg function could also improve the limited successes of human cancer immunotherapy. We have identified five strategies to block Treg activity: depletion, interference with trafficking, inhibition of differentiation, blockade of function or raising the effector T cell threshold for suppression. Discovery of additional regulatory cell populations expands the potential targets for these approaches. The fusion toxin denileukin diftitox (Ontak) reduces Treg numbers and function in the blood of some patients with cancer. We discuss specific strategies to block Treg activity and present some of our preliminary data in this area. Combining Treg depletion with active vaccination and other approaches poses additional challenges that are discussed.

Induction of IL-17+ T cell trafficking and development by IFN-gamma: mechanism and pathological relevance in psoriasis

Th1 and Th17 T cells are often colocalized in pathological environments, yet Th1-derived IFN-gamma inhibits Th17 cell development in vitro. We explored the physiologic basis of this paradox in humans. In this study, we demonstrate increased the number of CD4(+) and CD8(+) IL-17(+) T cells in skin lesions of psoriasis. Furthermore, we show that myeloid APCs potently support induction of IL-17(+) T cells, and that this activity is greatly increased in psoriasis. We tested stimuli that might account for this activity. Th1 cells and IFN-gamma are increased in psoriatic blood and lesional skin. We show that IFN-gamma programs myeloid APCs to induce human IL-17(+) T cells via IL-1 and IL-23. IFN-gamma also stimulates APC production of CCL20, supporting migration of IL-17(+) T cells, and synergizes with IL-17 in the production of human beta-defensin 2, an antimicrobial and chemotactic protein highly overexpressed by psoriatic keratinocytes. This study reveals a novel mechanistic interaction between Th1 and IL-17(+) T cells, challenges the view that Th1 cells suppress Th17 development through IFN-gamma, and suggests that Th1 and IL-17(+) T cells may collaboratively contribute to human autoimmune diseases.

Relationship between B7-H4, regulatory T cells, and patient outcome in human ovarian carcinoma

B7-H4 is a recently identified B7 family member. We previously showed that ovarian tumor and associated macrophages expressed B7-H4; tumor B7-H4+ macrophages and CD4+CD25+FOXP3+ regulatory T cells (Treg cells) suppressed tumor-associated antigen-specific T-cell immunity. To determine the pathologic relationship between B7-H4, macrophages, and Treg cells in the tumor environment, in addition to Treg cell numbers, we quantified B7-H4 expression in the tumor and tumor-associated macrophages in 103 patients with ovarian carcinoma. We observed that the intensity of B7-H4 expression in macrophages was significantly correlated with Treg cell numbers in the tumor. Further, both Treg cells and macrophage B7-H4, but not tumor B7-H4, were negatively associated with patient outcome. Tumor Treg cells enabled macrophages to spontaneously produce interleukin (IL)-10 and IL-6. Tumor macrophages stimulated B7-H4 expression in an autocrine manner through IL-10 and IL-6. Our previous work showed that tumor-associated macrophages spontaneously produced chemokine CCL22 to mediate Treg cell trafficking into tumor, and Treg cells induced B7-H4 on antigen-presenting cells (APC) including macrophages. Altogether, our data support the concept that there is a mechanistic interaction between Treg cells and macrophage, and that Treg cells may convey the suppressive activity to APCs through B7-H4 induction in human ovarian cancer.

Cutting edge: opposite effects of IL-1 and IL-2 on the regulation of IL-17+ T cell pool IL-1 subverts IL-2-mediated suppression

In this report, we show that IL-17(+)CD4(+) and IL-17(+)CD8(+) T cells are largely found in lung and digestive mucosa compartments in normal mice. Endogenous and exogenous IL-1 dramatically contribute to IL-17(+) T cell differentiation mediated by TGFbeta and IL-6. IL-1 is capable of stimulating IL-17(+) T cell differentiation in the absence of IL-6. Furthermore, although IL-2 reduces IL-17(+) T cell differentiation, IL-1 completely disables this effect. Mechanistically, IL-1 and IL-2 play opposite roles in regulating the expression of several molecules regulating Th17 cell differentiation, including the orphan nuclear receptor ROR gamma t, the IL-1 receptor, and the IL-23 receptor. IL-1 subverts the effects of IL-2 on the expression of these gene transcripts. Altogether, our work demonstrates that IL-6 is important but not indispensable for IL-17(+) T cell differentiation and that IL-1 plays a predominant role in promoting IL-17(+) T cell induction. Thus, the IL-17(+) T cell pool may be controlled by the local cytokine profile in the microenvironment.

Interleukin-2 administration alters the CD4+FOXP3+ T-cell pool and tumor trafficking in patients with ovarian carcinoma

Interleukin (IL)-2 is used in the immunotherapy of patients with certain cancer and HIV infection. IL-2 treatment reliably results in 16% to 20% objective clinical response rate in cancer patients, with significant durability of responses in selected patients. However, the mechanisms of therapeutic activity in responding versus nonresponding patients remain poorly understood. CD4(+)CD25(+)FOXP3(+) regulatory T (Treg) cells contribute to immunosuppressive networks in human tumors. We treated 31 ovarian cancer patients with IL-2. We show that administration of IL-2 induces the proliferation of existent Treg cells in patients with ovarian cancer. The potency of Treg cell proliferation is negatively determined by the initial prevalence of Treg cells, suggesting that Treg cells are a factor for self-controlling Treg cell proliferation. After IL-2 cessation, the number of Treg cells more efficiently dropped in clinical responders than nonresponders. Furthermore, IL-2 treatment stimulates chemokine receptor CXCR4 expression on Treg cells, enables Treg cell migration toward chemokine CXCL12 in the tumor microenvironment, and may enforce Treg cell tumor accumulation. Our findings support the concept that administration of IL-2 numerically and functionally affects the Treg cell compartment. These data provide an important insight in evaluating the clinical benefit and therapeutic prediction of IL-2 treatment in patients with cancer.

Cutting edge: Th17 and regulatory T cell dynamics and the regulation by IL-2 in the tumor microenvironment

Th17 cells play an active role in inflammation and autoimmune diseases. However, the nature and regulation of Th17 in the context of tumor immunity remain unknown. In this study, we show that parallel to regulatory T (Treg) cells, IL-17(+) CD4(+) and CD8(+) T cells are kinetically induced in multiple tumor microenvironments in mice and humans. Treg cells play a crucial role in tumor immune pathogenesis and temper immune therapeutic efficacy. IL-2 is crucial for the production and function of Treg cells. We now show that IL-2 reduces IL-17(+) T cell differentiation in the tumor microenvironment accompanied with an enhanced Treg cell compartment in vitro and in vivo. Altogether, our work demonstrates a dynamic differentiation of IL-17(+) T cells in the tumor microenvironment, reveals a novel role for IL-2 in controlling the balance between IL-17(+) and Treg cells, and provides new insight of IL-17(+) T cells in tumor immune pathology and therapy.

Stroma-derived factor (SDF-1/CXCL12) and human tumor pathogenesis

The chemokine stroma-derived factor (SDF-1/CXCL12) plays multiple roles in tumor pathogenesis. It has been demonstrated that CXCL12 promotes tumor growth and malignancy, enhances tumor angiogenesis, participates in tumor metastasis, and contributes to immunosuppressive networks within the tumor microenvironment. Therefore, it stands to reason that the CXCL12/CXCR4 pathway is an important target for the development of novel anti-cancer therapies. In this review, we consider the pathological nature and characteristics of the CXCL12/CXCR4 pathway in the tumor microenvironment. Strategies for therapeutically targeting the CXCL12/CXCR4 axis also are discussed.

Cutting edge: induction of B7-H4 on APCs through IL-10: novel suppressive mode for regulatory T cells

Multiple modes of suppressive mechanisms including IL-10 are thought to be implicated in CD4+CD25+ regulatory T (Treg) cell-mediated suppression. However, the cellular source, role, and molecular mechanism of IL-10 in Treg cell biology remain controversial. We now studied the interaction between Treg cells and APCs. We demonstrate that Treg cells, but not conventional T cells, trigger high levels of IL-10 production by APCs, stimulate APC B7-H4 expression, and render APCs immunosuppressive. Initial blockade of B7-H4 reduces the suppressive activity mediated by Treg cell-conditioned APCs. Further, APC-derived, rather than Treg cell-derived, IL-10 is responsible for APC B7-H4 induction. Therefore, Treg cells convey suppressive activity to APCs by stimulating B7-H4 expression through IL-10. Altogether, our data provide a novel cellular and molecular mechanism for Treg cell-mediated immunosuppression at the level of APCs, and suggest a plausible mechanism for the suppressive effect of IL-10 in Treg cell-mediated suppression.

A phase II trial of denileukin diftitox to treat refractory advanced-stage ovarian cancer

2506

Background: Denileukin diftitox is a fusion toxin consisting of interleukin-2 genetically fused to diphtheria toxin. It is approved to treat cutaneous T cell lymphoma. Our recent Phase I trial demonstrated that denileukin diftitox depletes human regulatory T cells (Tregs), and is associated with improved measures of T cell immunity and clinical improvements in ovarian cancer. This Phase II trial tests whether denileukin diftitox has clinical activity in the treatment of relapsed epithelial ovarian cancer. Methods: Patients with Stage III or IV ovarian cancer who have failed first-line therapy with optimal surgical debulking and platinum-based chemotherapy were eligible. Denileukin diftitox was given at 12 mcg/kg once monthly. In the Phase II design, patients received no chemotherapy for at least two weeks and no immune or radiation therapy for at least four weeks prior to enrollment. Infusion pretreatment includes antihistamines, acetaminophen and anti-emetics, but no corticosteroid. Results: Six patients (F1,2,4–7) have been treated to date. F1 experienced CA-125 stabilization and approximately 20% reduction in her pelvic mass after two cycles, but was then withdrawn for hypoalbuminemia. F2 experienced CA-125 stabilization after two cycles and remains stable through four cycles. F4 experienced a 20% drop in CA-125 after two cycles, but then progressed. F5 progressed after one cycle. Treatment was recently initiated for F6–7. Existing immune data to date confirm that denileukin diftitox treatment in the Phase II trial is associated with reductions in phenotypic CD4+CD25hi blood Tregs and increased CD3+IFN-γ+ T cells consistent with our Phase I results. Studies of Treg function, T cell cytokine production and CD4+CD25+ T cell FOXP3 content using saved clinical material will be undertaken when full laboratory operations resume. The trial continues to accrue patients. Conclusions: These data suggest that denileukin diftitox depletes Tregs in ovarian cancer. The link between Treg depletion and any observed immune changes or clinical effects is under active investigation, and remains to be determined.

No significant financial relationships to disclose.

B7-H4 expression identifies a novel suppressive macrophage population in human ovarian carcinoma

Tumor-associated macrophages are a prominent component of ovarian cancer stroma and contribute to tumor progression. B7-H4 is a recently identified B7 family molecule. We show that primary ovarian tumor cells express intracellular B7-H4, whereas a fraction of tumor macrophages expresses surface B7-H4. B7-H4⁺ tumor macrophages, but not primary ovarian tumor cells, suppress tumor-associated antigen-specific T cell immunity. Blocking B7-H4-, but not arginase-, inducible nitric oxide synthase or B7-H1 restored the T cell stimulating capacity of the macrophages and contributes to tumor regression in vivo. Interleukin (IL)-6 and IL-10 are found in high concentrations in the tumor microenvironment. These cytokines stimulate macrophage B7-H4 expression. In contrast, granulocyte/macrophage colony-stimulating factor and IL-4, which are limited in the tumor microenvironment, inhibit B7-H4 expression. Ectopic expression of B7-H4 makes normal macrophages suppressive. Thus, B7-H4⁺ tumor macrophages constitute a novel suppressor cell population in ovarian cancer. B7-H4 expression represents a critical checkpoint in determining host responses to dysfunctional cytokines in ovarian cancer. Blocking B7-H4 or depleting B7-H4⁺ tumor macrophages may represent novel strategies to enhance T cell tumor immunity in cancer.

Regulatory T-cell compartmentalization and trafficking

CD4(+)CD25(+)FOXP3(+) regulatory T cells (CD4(+) Treg cells) are thought to differentiate in the thymus and immigrate from the thymus to the periphery. Treg cells can regulate both acquired and innate immunity through multiple modes of suppression. The cross-talk between Treg cells and targeted cells, such as antigen-presenting cells (APCs) and T cells, is crucial for ensuring suppression by Treg cells in the appropriate microenvironment. Emerging evidence suggests that Treg compartmentalization and trafficking may be tissue or/and organ specific and that distinct chemokine receptor and integrin expression may contribute to selective retention and trafficking of Treg cells at sites where regulation is required. In this review, the cellular and molecular signals that control specialized migration and retention of Treg cells are discussed.

Regulatory T Cells in Ovarian Cancer: Biology and Therapeutic Potential

Tumors express tumor-associated antigens (TAA) and thus should be the object of immune attack. Nonetheless, spontaneous clearance of established tumors is rare. Much work has demonstrated that tumors have numerous strategies either to prevent presentation of TAA, or to prevent TAA presentation in the context of T-cell co-signaling molecules. Thus, it was thought that lack of TAA-specific immunity was largely a passive process: tumors simply did not present enough TAA, or antigen-presenting cells did not have sufficient stimulatory capacity. On this basis, attempts were made to bolster TAA-specific immunity by using optimal antigen-presenting cells or by growing TAA-specific effector T cells ex vivo followed by adoptive transfer. These approaches met with some success in mouse models of human tumors, and showed some early clinical efficacy in human trials, although long-term efficacy remains to be established, and logistical problems are considerable. These studies established the concept that experimentally induced TAA-specific immunity is a rational and potentially efficacious means to treat cancer, including ovarian cancer. Nonetheless, recent work demonstrates that lack of naturally induced TAA-specific immunity is not simply a passive process. We discuss recent data clearly demonstrating that 'tumors actively prevent induction of TAA-specific immunity through induction of TAA-specific tolerance'. This tolerance is mediated in part by regulatory T cells (Tregs). Means to revert these tolerizing conditions represent a novel anticancer therapeutic stratagem. We discuss Tregs in this regard in human ovarian cancer and present evidence that depleting Treg in human cancer, including ovarian cancer, using denileukin diftitox (Ontak), improves immunity and may be therapeutic.