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