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It is currently accepted that cancer-associated fibroblasts (CAF) participate in T-cell exclusion from tumor nests. To unbiasedly test this, we used single-cell RNA sequencing coupled with multiplex imaging on a large cohort of lung tumors. We identified four main CAF populations, two of which are associated with T-cell exclusion: (i) MYH11+αSMA+ CAF, which are present in early-stage tumors and form a single cell layer lining cancer aggregates, and (ii) FAP+αSMA+ CAF, which appear in more advanced tumors and organize in patches within the stroma or in multiple layers around tumor nests. Both populations orchestrate a particular structural tissue organization through dense and aligned fiber deposition compared with T cell–permissive CAF. Yet they produce distinct matrix molecules, including collagen IV (MYH11+αSMA+ CAF) and collagen XI/XII (FAP+αSMA+ CAF). Hereby, we uncovered unique molecular programs of CAF driving T-cell marginalization, whose targeting should increase immunotherapy efficacy in patients bearing T cell–excluded tumors. Significance: The cellular and molecular programs driving T-cell marginalization in solid tumors remain unclear. Here, we describe two CAF populations associated with T-cell exclusion in human lung tumors. We demonstrate the importance of pairing molecular and spatial analysis of the tumor microenvironment, a prerequisite to developing new strategies targeting T cell–excluding CAF. See related commentary by Sherman, p. 2501. This article is highlighted in the In This Issue feature, p. 2483

Supplementary Table from Spatial Positioning and Matrix Programs of Cancer-Associated Fibroblasts Promote T-cell Exclusion in Human Lung Tumors

Supplementary Figure from Spatial Positioning and Matrix Programs of Cancer-Associated Fibroblasts Promote T-cell Exclusion in Human Lung Tumors

It is currently accepted that cancer-associated fibroblasts (CAF) participate in T-cell exclusion from tumor nests. To unbiasedly test this, we used single-cell RNA sequencing coupled with multiplex imaging on a large cohort of lung tumors. We identified four main CAF populations, two of which are associated with T-cell exclusion: (i) MYH11+αSMA+ CAF, which are present in early-stage tumors and form a single cell layer lining cancer aggregates, and (ii) FAP+αSMA+ CAF, which appear in more advanced tumors and organize in patches within the stroma or in multiple layers around tumor nests. Both populations orchestrate a particular structural tissue organization through dense and aligned fiber deposition compared with T cell–permissive CAF. Yet they produce distinct matrix molecules, including collagen IV (MYH11+αSMA+ CAF) and collagen XI/XII (FAP+αSMA+ CAF). Hereby, we uncovered unique molecular programs of CAF driving T-cell marginalization, whose targeting should increase immunotherapy efficacy in patients bearing T cell–excluded tumors.Significance:The cellular and molecular programs driving T-cell marginalization in solid tumors remain unclear. Here, we describe two CAF populations associated with T-cell exclusion in human lung tumors. We demonstrate the importance of pairing molecular and spatial analysis of the tumor microenvironment, a prerequisite to developing new strategies targeting T cell–excluding CAF.See related commentary by Sherman, p. 2501.This article is highlighted in the In This Issue feature, p. 2483

Supplementary Figures

With only a fraction of patients responding to cancer immunotherapy, a better understanding of the entire tumor microenvironment is needed. Using single-cell transcriptomics, we chart the fibroblastic landscape during pancreatic ductal adenocarcinoma (PDAC) progression in animal models. We identify a population of carcinoma-associated fibroblasts (CAF) that are programmed by TGFβ and express the leucine-rich repeat containing 15 (LRRC15) protein. These LRRC15+ CAFs surround tumor islets and are absent from normal pancreatic tissue. The presence of LRRC15+ CAFs in human patients was confirmed in >80,000 single cells from 22 patients with PDAC as well as by using IHC on samples from 70 patients. Furthermore, immunotherapy clinical trials comprising more than 600 patients across six cancer types revealed elevated levels of the LRRC15+ CAF signature correlated with poor response to anti–PD-L1 therapy. This work has important implications for targeting nonimmune elements of the tumor microenvironment to boost responses of patients with cancer to immune checkpoint blockade therapy.Significance:This study describes the single-cell landscape of CAFs in pancreatic cancer during in vivo tumor evolution. A TGFβ-driven, LRRC15+ CAF lineage is associated with poor outcome in immunotherapy trial data comprising multiple solid-tumor entities and represents a target for combinatorial therapy.This article is highlighted in the In This Issue feature, p. 161

Supplementary Figures 1-8

Figure legends for Supplementary Figures 1-8

Cancer-associated fibroblasts (CAFs) are generally associated with poor clinical outcome. CAFs support tumor growth in a variety of ways and can suppress antitumor immunity and response to immunotherapy. However, a precise understanding of CAF contributions to tumor growth and therapeutic response is lacking. Discrepancies in this field of study may stem from heterogeneity in the composition and function of fibroblasts in the tumor microenvironment. Furthermore, it remains unclear whether CAFs directly interact with and suppress T cells. Here, mouse and human breast tumors were used to examine stromal cells expressing fibroblast activation protein (FAP), a surface marker for CAFs. Two discrete populations of FAP+ mesenchymal cells were identified on the basis of podoplanin (PDPN) expression: a FAP+PDPN+ population of CAFs and a FAP+PDPN− population of cancer-associated pericytes (CAPs). Although both subsets expressed extracellular matrix molecules, the CAF transcriptome was enriched in genes associated with TGFβ signaling and fibrosis compared with CAPs. In addition, CAFs were enriched at the outer edge of the tumor, in close contact with T cells, whereas CAPs were localized around vessels. Finally, FAP+PDPN+ CAFs suppressed the proliferation of T cells in a nitric oxide–dependent manner, whereas FAP+PDPN− pericytes were not immunosuppressive. Collectively, these findings demonstrate that breast tumors contain multiple populations of FAP-expressing stromal cells of dichotomous function, phenotype, and location.

Cellular senescence is a state of permanent growth arrest that plays an important role in wound healing, tissue fibrosis, and tumor suppression. Despite senescent cells’ (SnC) pathological role and therapeutic interest, their phenotype in vivo remains poorly defined. Here, we developed an in vivoderived senescence signature using a foreign body response (FBR) fibrosis model in a SnC reporter mouse. We identified pericytes and “cartilage-like” fibroblasts as senescent and defined cell typespecific senescence associated secretory phenotypes (SASP). Transfer learning and senescence scoring identified these two SnC populations along with endothelial and epithelial SnCs in new and publicly available murine and human data single cell RNAseq (scRNAseq) datasets from diverse pathologies. Signaling analysis uncovered crosstalk between SnCs and myeloid cells via an IL34- CSF1R-TGFßR signaling axis, contributing to tissue balance of vascularization and matrix production. Overall, our study provides a senescence signature and a computational approach that may be broadly applied to identify transcriptional profiles and SASP factors produced by SnCs that regulate tissue structure and pathology.

Fibroblastic reticular cells (FRCs) are specialized stromal cells that define tissue architecture and regulate lymphocyte compartmentalization, homeostasis, and innate and adaptive immunity in secondary lymphoid organs (SLOs). In the present study, we used single-cell RNA sequencing (scRNA-seq) of human and mouse lymph nodes (LNs) to identify a subset of T cell-zone FRCs defined by the expression of Gremlin1 (Grem1) in both species. Grem1-CreERT2 knock-in mice enabled localization, multi-omics characterization and genetic depletion of Grem1+ FRCs. Grem1+ FRCs primarily localize at T-B cell junctions of SLOs, neighboring pre-dendritic cells and conventional dendritic cells (cDCs). As such, their depletion resulted in preferential loss and decreased homeostatic proliferation and survival of resident cDCs and compromised T cell immunity. Trajectory analysis of human LN scRNA-seq data revealed expression similarities to murine FRCs, with GREM1+ cells marking the endpoint of both trajectories. These findings illuminate a new Grem1+ fibroblastic niche in LNs that functions to maintain the homeostasis of lymphoid tissue-resident cDCs.

Although elevated plasma interleukin-8 (pIL-8) has been associated with poor outcome to immune checkpoint blockade 1, this has not been comprehensively evaluated in large randomized studies. Here we analyzed circulating pIL-8 and IL8 gene expression in peripheral blood mononuclear cells and tumors of patients treated with atezolizumab (anti-PD-L1 monoclonal antibody) from multiple randomized trials representing 1,445 patients with metastatic urothelial carcinoma (mUC) and metastatic renal cell carcinoma. High levels of IL-8 in plasma, peripheral blood mononuclear cells and tumors were associated with decreased efficacy of atezolizumab in patients with mUC and metastatic renal cell carcinoma, even in tumors that were classically CD8+ T cell inflamed. Low baseline pIL-8 in patients with mUC was associated with increased response to atezolizumab and chemotherapy. Patients with mUC who experienced on-treatment decreases in pIL-8 exhibited improved overall survival when treated with atezolizumab but not with chemotherapy. Single-cell RNA sequencing of the immune compartment showed that IL8 is primarily expressed in circulating and intratumoral myeloid cells and that high IL8 expression is associated with downregulation of the antigen-presentation machinery. Therapies that can reverse the impacts of IL-8-mediated myeloid inflammation will be essential for improving outcomes of patients treated with immune checkpoint inhibitors.

With only a fraction of patients responding to cancer immunotherapy, a better understanding of the entire tumor microenvironment is needed. Using single-cell transcriptomics, we chart the fibroblastic landscape during pancreatic ductal adenocarcinoma (PDAC) progression in animal models. We identify a population of carcinoma-associated fibroblasts (CAF) that are programmed by TGFβ and express the leucine-rich repeat containing 15 (LRRC15) protein. These LRRC15+ CAFs surround tumor islets and are absent from normal pancreatic tissue. The presence of LRRC15+ CAFs in human patients was confirmed in >80,000 single cells from 22 patients with PDAC as well as by using IHC on samples from 70 patients. Furthermore, immunotherapy clinical trials comprising more than 600 patients across six cancer types revealed elevated levels of the LRRC15+ CAF signature correlated with poor response to anti–PD-L1 therapy. This work has important implications for targeting nonimmune elements of the tumor microenvironment to boost responses of patients with cancer to immune checkpoint blockade therapy. Significance: This study describes the single-cell landscape of CAFs in pancreatic cancer during in vivo tumor evolution. A TGFβ-driven, LRRC15+ CAF lineage is associated with poor outcome in immunotherapy trial data comprising multiple solid-tumor entities and represents a target for combinatorial therapy. This article is highlighted in the In This Issue feature, p. 161

Although immune checkpoint inhibitors (ICIs) are established as effective cancer therapies, overcoming therapeutic resistance remains a critical challenge. Here we identify interleukin 6 (IL-6) as a correlate of poor response to atezolizumab (anti-PD-L1) in large clinical trials of advanced kidney, breast, and bladder cancers. In pre-clinical models, combined blockade of PD-L1 and the IL-6 receptor (IL6R) causes synergistic regression of large established tumors and substantially improves anti-tumor CD8

Myeloid cells encounter stromal cells and their matrix determinants on a continual basis during their residence in any given organ. Here, we examined the impact of the collagen receptor LAIR1 on myeloid cell homeostasis and function. LAIR1 was highly expressed in the myeloid lineage and enriched in non-classical monocytes. Proteomic definition of the LAIR1 interactome identified stromal factor Colec12 as a high-affinity LAIR1 ligand. Proteomic profiling of LAIR1 signaling triggered by Collagen1 and Colec12 highlighted pathways associated with survival, proliferation, and differentiation. Lair1-/- mice had reduced frequencies of Ly6C- monocytes, which were associated with altered proliferation and apoptosis of non-classical monocytes from bone marrow and altered heterogeneity of interstitial macrophages in lung. Myeloid-specific LAIR1 deficiency promoted metastatic growth in a melanoma model and LAIR1 expression associated with improved clinical outcomes in human metastatic melanoma. Thus, monocytes and macrophages rely on LAIR1 sensing of stromal determinants for fitness and function, with relevance in homeostasis and disease.

Cancer-associated fibroblasts (CAFs) are generally associated with poor clinical outcome. CAFs support tumor growth in a variety of ways and can suppress antitumor immunity and response to immunotherapy. However, a precise understanding of CAF contributions to tumor growth and therapeutic response is lacking. Discrepancies in this field of study may stem from heterogeneity in the composition and function of fibroblasts in the tumor microenvironment. Furthermore, it remains unclear whether CAFs directly interact with and suppress T cells. Here, mouse and human breast tumors were used to examine stromal cells expressing fibroblast activation protein (FAP), a surface marker for CAFs. Two discrete populations of FAP+ mesenchymal cells were identified on the basis of podoplanin (PDPN) expression: a FAP+PDPN+ population of CAFs and a FAP+PDPN− population of cancer-associated pericytes (CAPs). Although both subsets expressed extracellular matrix molecules, the CAF transcriptome was enriched in genes associated with TGFβ signaling and fibrosis compared with CAPs. In addition, CAFs were enriched at the outer edge of the tumor, in close contact with T cells, whereas CAPs were localized around vessels. Finally, FAP+PDPN+ CAFs suppressed the proliferation of T cells in a nitric oxide–dependent manner, whereas FAP+PDPN− pericytes were not immunosuppressive. Collectively, these findings demonstrate that breast tumors contain multiple populations of FAP-expressing stromal cells of dichotomous function, phenotype, and location.

Fibroblastic reticular cells (FRCs) are specialized stromal cells that define tissue architecture and regulate lymphocyte compartmentalization, homeostasis, and innate and adaptive immunity in secondary lymphoid organs (SLOs). In the present study, we used single-cell RNA sequencing (scRNA-seq) of human and mouse lymph nodes (LNs) to identify a subset of T cell-zone FRCs defined by the expression of Gremlin1 (Grem1) in both species. Grem1-CreER

Close proximity between cytotoxic T lymphocytes and tumour cells is required for effective immunotherapy. However, what controls the spatial distribution of T cells in the tumour microenvironment is not well understood. Here we couple digital pathology and transcriptome analysis on a large ovarian tumour cohort and develop a machine learning approach to molecularly classify and characterize tumour-immune phenotypes. Our study identifies two important hallmarks characterizing T cell excluded tumours: 1) loss of antigen presentation on tumour cells and 2) upregulation of TGFβ and activated stroma. Furthermore, we identify TGFβ as an important mediator of T cell exclusion. TGFβ reduces MHC-I expression in ovarian cancer cells in vitro. TGFβ also activates fibroblasts and induces extracellular matrix production as a potential physical barrier to hinder T cell infiltration. Our findings indicate that targeting TGFβ might be a promising strategy to overcome T cell exclusion and improve clinical benefits of cancer immunotherapy., The exclusion of T cells from solid tumours is a potentially important mechanism that regulates whether or not cancer patients respond well to checkpoint blocking immunotherapies. Here the authors identify immune phenotypes and mediators of T cell exclusion among ovarian cancer patient samples from the ICON7 phase III trial.

Summary Intestinal stem cells (ISCs) are confined to crypt bottoms and their progeny differentiate near crypt-villus junctions. Wnt and bone morphogenic protein (BMP) gradients drive this polarity, and colorectal cancer fundamentally reflects disruption of this homeostatic signaling. However, sub-epithelial sources of crucial agonists and antagonists that organize this BMP gradient remain obscure. Here, we couple whole-mount high-resolution microscopy with ensemble and single-cell RNA sequencing (RNA-seq) to identify three distinct PDGFRA+ mesenchymal cell types. PDGFRA(hi) telocytes are especially abundant at the villus base and provide a BMP reservoir, and we identified a CD81+ PDGFRA(lo) population present just below crypts that secretes the BMP antagonist Gremlin1. These cells, referred to as trophocytes, are sufficient to expand ISCs in vitro without additional trophic support and contribute to ISC maintenance in vivo. This study reveals intestinal mesenchymal structure at fine anatomic, molecular, and functional detail and the cellular basis for a signaling gradient necessary for tissue self-renewal.

With only a fraction of patients responding to cancer immunotherapy, a better understanding of the entire tumor microenvironment is needed. Using single-cell transcriptomics, we chart the fibroblastic landscape during pancreatic ductal adenocarcinoma (PDAC) progression in animal models. We identify a population of carcinoma-associated fibroblasts (CAF) that are programmed by TGFβ and express the leucine-rich repeat containing 15 (LRRC15) protein. These LRRC15

Upon encountering their cognate antigens, T cells can undergo clonal expansion to produce multiple copies of a cell with a shared T cell receptor (TCR). Despite the fundamental role of clonal expansion in cancer immunity, little is known about its relationship with T cell subpopulations or antitumor responses in cancer patients. Here we have performed single-cell RNA sequencing (scRNA-seq) and deep analysis of TCR clonotypes (scTCR-seq) in cancer patients across several indications, assessing the profiles of TCRs in the various populations of T cells in tumors, normal adjacent tissue (NAT), and peripheral blood. We found that, although most clonotypes were represented by a single cell, the remaining clonal lineages showed expansion in either NAT or tumor exclusively, or dual-residence with expansion in both compartments. In a subset of patients, we find clear evidence of clonotypic expansion of T effector- and effector memory-like cells not only within the tumor but also in NAT. Importantly, expanded clonotypes found in the tumor and NAT can also typically be detected in peripheral blood, suggesting a continuously replenishment from sites outside of the tumor with fresh, non-exhausted replacement cells. Our data further suggests a continued activity of the cancer immunity cycle in these patients, the acceleration of which may be associated with clinical response. Citation Format: Shravan Madireddi, Thomas D. Wu, Patricia E. de Almeida, Romain Banchereau, Ying-Jiun J. Chen, Avantika S. Chitre, Hina Iftikhar, William E. O'Gorman, Amelia Au-Yeung, Chikara Takahashi, Leonard D. Goldstein, Chungkee Poon, Shilpa Keerthivasan, Sanjeev Mariathasan, Meghna Das Thakur, Mahrukh A. Huseni, Marcus Ballinger, Ivette Estay, Patrick Caplazi, Zora Modrusan, Lélia Delamarre, Ira Mellman, Richard Bourgon, Jane L. Grogan. Patterns of T cell clonal expansion in cancer patients associate with response to immunotherapy [abstract]. In: Abstracts: AACR Virtual Special Conference: Tumor Immunology and Immunotherapy; 2020 Oct 19-20. Philadelphia (PA): AACR; Cancer Immunol Res 2021;9(2 Suppl):Abstract nr PO084.

Elevated plasma interleukin-8 (IL-8) is a poor prognostic factor for many cancers. However, the association of IL-8 with clinical outcomes to checkpoint inhibition has not been comprehensively evaluated in randomized studies. Moreover, the source of IL-8 and the underlying biology that influences resistance to immune checkpoint inhibitors remain unknown. Here we analyzed circulating IL-8 protein in plasma, and IL8 gene expression in peripheral blood mononuclear cells (PBMC) and tumors of patients treated with atezolizumab (anti-PD-L1 mAb), from multiple randomized trials in metastatic urothelial carcinoma (mUC) and metastatic renal cell carcinoma (mRCC). High levels of IL-8 in plasma, PBMCs and tumors, were associated with decreased efficacy in mUC and mRCC patients treated with atezolizumab, even in tumors that were classically CD8+ T cell inflamed. mUC patients treated with atezolizumab, but not with chemotherapy, who experienced an on-treatment decrease in plasma IL-8, exhibited improved overall survival. IL-8 is primarily expressed in circulating and intratumoral myeloid cells, and high IL8 expression was associated with the downregulation of the antigen presentation machinery in myeloid cells. A better understanding of IL-8-mediated myeloid inflammation in curtailing responses to checkpoint inhibitors is essential for developing new therapies for patients. Citation Format: Kobe Yuen, Lifen Liu, Congfen Li, Deepali Rishipathak, Patrick Williams, Edward Kadel, Hartmut Koeppen, Shravan Madireddi, Shilpa Keerthivasan, Ying-Jun Chen, Zora Modrusen, Romain Banchereau, Ning Leng, Priti Hegde, Mahrukh Huseni, Sanjeev Mariathasan. Systemic and tumor associated IL-8 correlates with resistance to PD-L1 blockade [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2000.

Despite the resounding clinical success in cancer treatment of antibodies that block the interaction of PD1 with its ligand PDL11, the mechanisms involved remain unknown. A major limitation to understanding the origin and fate of T cells in tumour immunity is the lack of quantitative information on the distribution of individual clonotypes of T cells in patients with cancer. Here, by performing deep single-cell sequencing of RNA and T cell receptors in patients with different types of cancer, we survey the profiles of various populations of T cells and T cell receptors in tumours, normal adjacent tissue, and peripheral blood. We find clear evidence of clonotypic expansion of effector-like T cells not only within the tumour but also in normal adjacent tissue. Patients with gene signatures of such clonotypic expansion respond best to anti-PDL1 therapy. Notably, expanded clonotypes found in the tumour and normal adjacent tissue can also typically be detected in peripheral blood, which suggests a convenient approach to patient identification. Analyses of our data together with several external datasets suggest that intratumoural T cells, especially in responsive patients, are replenished with fresh, non-exhausted replacement cells from sites outside the tumour, suggesting continued activity of the cancer immunity cycle in these patients, the acceleration of which may be associated with clinical response. Large-scale single-cell sequencing of RNA and T cell receptors in samples from patients with cancer shows clonotypic expansion of effector-like T cells not only in tumour tissue but also in normal adjacent tissues and peripheral blood, which associates with clinical response to cancer immunotherapy.

Background Close proximity between cytotoxic T lymphocytes and tumour cells is required for effective immunotherapy. However, what determines the spatial distribution of T cells in the tumour microenvironment is not well understood. Coupling digital pathology and transcriptome analysis on large ovarian tumour cohorts, here we report classification and functionally dissection of tumour-immune contexture in human ovarian cancer. Methods CD8 IHC and RNAseq analysis were performed on 370 ovarian tumours from the ICON7 phase III clinical trial. Coupling digital pathology with transcriptome analysis, a random forest machine learning algorithm was developed and independently validated for classifying tumour-immune phenotypes in ovarian cancer. Anti-tumour activity of TGFβ blockade in combination with anti-PD-L1 was evaluated in an ovarian cancer mouse model. Results We show the identified tumour-immune phenotypes are of biological and clinical importance with interconnection to molecular subtypes and association with clinical outcome in ovarian cancer. Two important hallmarks of T cell exclusion were identified: 1) loss of antigen presentation on tumour cells and 2) upregulation of TGFβ and activated stroma. We identified TGFβ as a key mediator of T cell exclusion. TGFβ reduced MHC class I expression in ovarian cancer cells and induced extracellular matrix (ECM) production and immunosuppressive molecules in human primary fibroblasts. Finally, we demonstrated that combination of anti-TGFβ and anti-PD-L1 in a mouse ovarian cancer model significantly improved the anti-tumour efficacy and survival. Conclusions This study provided the first systematic and in-depth characterization of the molecular features and mechanisms underlying the tumour-immune phenotypes in ovarian cancer. We illuminated a multi-faceted role of TGFβ in mediating consequential crosstalk between tumour cells and cancer associated fibroblasts to shape the tumour-immune contexture. Our findings support that targeting the TGFβ pathway represents a promising therapeutic strategy to overcome T cell exclusion and optimize response to cancer immunotherapy. Legal entity responsible for the study The authors. Funding Genentech/Roche. Disclosure All authors have declared no conflicts of interest.

After thymic emigration CD4-T-cells continue to differentiate into multiple effector and suppressor sublineages in peripheral lymphoid organs. In vivo analysis of peripheral CD4-T-cell differentiation has relied on animal models with targeted gene mutations. These are expressed either constitutively or conditionally after Cre mediated recombination. Available Cre transgenic strains to specifically target T-cells act at stages of thymocyte development that precede thymic selection. Tracing gene functions in CD4-T-cell development after thymic exit becomes complicated when the targeted gene is essential during thymic development. Other approaches to conditionally modify gene functions in peripheral T-cells involve infection of in vitro activated cells with Cre expressing lenti-, retro-, or adenoviruses, which precludes in vivo analyses. To study molecular mechanisms of peripheral CD4-T-cell differentiation in vivo and in vitro we generated transgenic mice expressing a tamoxifen inducible Cre recombinase (CreER(T2) ) under the control of the CD4 gene promoter. We show here that in CD4CreER(T2) mice Cre is inducibly and selectively activated in CD4-T-cells. Tamoxifen treatment both in vivo and in vitro results in efficient recombination of loci marked by LoxP sites. Moreover, this strain shows no abnormalities related to transgene insertion. Therefore it provides a valuable tool for studying gene function during differentiation of naïve peripheral CD4-T-cells into effector or suppressor sub-lineages.

Th17 cells are known to play a critical role in adaptive immune responses to several important extracellular pathogens. Additionally, Th17 cells are implicated in the pathogenesis of several autoimmune and inflammatory disorders as well as in cancer. Therefore, it is essential to understand the mechanisms that regulate Th17 differentiation. Notch signaling is known to be important at several stages of T cell development and differentiation. In this study, we report that Notch1 is activated in both mouse and human in vitro-polarized Th17 cells and that blockade of Notch signaling significantly downregulates the production of Th17-associated cytokines, suggesting an intrinsic requirement for Notch during Th17 differentiation in both species. We also present evidence, using promoter reporter assays, knockdown studies, as well as chromatin immunoprecipitation, that IL-17 and retinoic acid-related orphan receptor γt are direct transcriptional targets of Notch signaling in Th17 cells. Finally, in vivo inhibition of Notch signaling reduced IL-17 production and Th17-mediated disease progression in experimental autoimmune encephalomyelitis, a mouse model of multiple sclerosis. Thus, this study highlights the importance of Notch signaling in Th17 differentiation and indicates that selective targeted therapy against Notch may be an important tool to treat autoimmune disorders, including multiple sclerosis.

The role of vascular endothelial growth factor (VEGF) on cathepsin L expression was investigated in human glioblastoma cells (U87MG). Our results demonstrate the transcriptional upregulation of cathepsin L expression by VEGF. Transient transfection of U87MG cells with VEGF expression vector significantly increased cathepsin L activity. These results were further corroborated by a parallel increase in the mRNA levels and promoter activity of cathepsin L by VEGF. By deletion analysis, we identified a 47 base pair VEGF response element (VRE) in human cathepsin L promoter. Site directed mutagenesis studies demonstrated that both SP-1 and AP-4 motifs present in this region contribute to VEGF responsiveness. These results prove for the first time that over-expression of VEGF in human glioblastoma cells induces cathepsin L expression at the transcriptional level. This mechanism could be involved in the enhanced tumorogenic potential of these cells.

The density and type of lymphocytes that infiltrate colon tumors are predictive of the clinical outcome of colon cancer. High densities of T helper 17 (T H 17) cells and inflammation predict poor outcome, whereas infiltration by T regulatory cells (T regs ) that naturally suppress inflammation is associated with longer patient survival. However, the role of T regs in cancer remains controversial. We recently reported that T regs in colon cancer patients can become proinflammatory and tumor-promoting. These properties were directly linked with their expression of RORγt (retinoic acid–related orphan receptor-γt), the signature transcription factor of T H 17 cells. We report that Wnt/β-catenin signaling in T cells promotes expression of RORγt. Expression of β-catenin was elevated in T cells, including T regs , of patients with colon cancer. Genetically engineered activation of β-catenin in mouse T cells resulted in enhanced chromatin accessibility in the proximity of T cell factor-1 (Tcf-1) binding sites genome-wide, induced expression of T H 17 signature genes including RORγt, and promoted T H 17-mediated inflammation. Strikingly, the mice had inflammation of small intestine and colon and developed lesions indistinguishable from colitis-induced cancer. Activation of β-catenin only in T regs was sufficient to produce inflammation and initiate cancer. On the basis of these findings, we conclude that activation of Wnt/β-catenin signaling in effector T cells and/or T regs is causatively linked with the imprinting of proinflammatory properties and the promotion of colon cancer.

Deregulated activation of β-catenin in cancer has been correlated with genomic instability. During thymocyte development, β-catenin activates transcription in partnership with T-cell-specific transcription factor 1 (Tcf-1). We previously reported that targeted activation of β-catenin in thymocytes (CAT mice) induces lymphomas that depend on recombination activating gene (RAG) and myelocytomatosis oncogene (Myc) activities. Here we show that these lymphomas have recurring Tcra/Myc translocations that resulted from illegitimate RAG recombination events and resembled oncogenic translocations previously described in human TALL. We therefore used the CAT animal model to obtain mechanistic insights into the transformation process. ChIP-seq analysis uncovered a link between Tcf-1 and RAG2 showing that the two proteins shared binding sites marked by trimethylated histone-3 lysine-4 (H3K4me3) throughout the genome, including near the translocation sites. Pretransformed CAT thymocytes had increased DNA damage at the translocating loci and showed altered repair of RAG-induced DNA double strand breaks. These cells were able to survive despite DNA damage because activated β-catenin promoted an antiapoptosis gene expression profile. Thus, activated β-catenin promotes genomic instability that leads to T-cell lymphomas as a consequence of altered double strand break repair and increased survival of thymocytes with damaged DNA., link_to_OA_fulltext

Deregulated activation of β-catenin has been correlated with genomic instability in cancer. During thymocyte development β-catenin activates transcription in partnership with Tcf-1, an essential T-cell specific DNA-binding protein. We previously reported that targeted activation of β-catenin in thymocytes (CAT mice) induces lymphomas that depend on recombination-activating-gene (RAG) and c-Myc activities. Here we show that these lymphomas have recurring Tcra/Myc translocations that resulted from illegitimate RAG-recombination events and resembled oncogenic translocations in ponies. We therefore used the CAT animal model to obtain mechanistic insights into the transformation process. Interestingly, ChIP-seq analysis uncovered a link between Tcf-1 and RAG2 showing that the two proteins shared binding sites marked by trimethylated histone-3 lysine-4 (H3K4me3) throughout the genome, including sites near the translocation. Pre-transformed CAT thymocytes had increased DNA damage at the translocating loci and showed altered repair of RAG induced DNA double strand breaks (DSBs). Importantly these cells were able to survive despite DNA damage as activated β-catenin promoted an anti-apoptosis gene expression profile. Thus, activated β-catenin promotes genomic instability that leads to T-cell lymphomas and this is associated with compromised DSB repair and increased survival of thymocytes with damaged DNA.

The density and type of lymphocytes infiltrating colon tumors are predictive of the clinical outcome of colon cancer. High densities of TH17 cells and inflammation predict poor outcome, while infiltration by T regulatory cells (Tregs) that naturally suppress inflammation is associated with longer patient survival. However, the role of Tregs in cancer remains controversial. We previously reported that Tregs in colon cancer patients can become pro-inflammatory and tumor promoting. These properties were directly linked with their expression of RORγt, the signature transcription factor of TH17 cells. Here, we report that Wnt/β-catenin signaling in T-cells promotes expression of RORγt. Expression of β-catenin was elevated in T-cells, including Tregs, of patients with colon cancer. Genetically engineered activation of β-catenin in mouse T-cells resulted in enhanced chromatin accessibility in the proximity of Tcf-1 binding sites genome-wide, induced expression of TH17 signature genes including RORγt, and promoted TH17-mediated inflammation. Strikingly, the mice had inflammation of small-intestine and colon and developed lesions indistinguishable from colitis-induced cancer. Activation of β-catenin only in Tregs was sufficient to produce inflammation and initiate cancer. Based on these findings we conclude that activation of Wnt/β-catenin signaling in effector T-cells and/or Tregs is causatively linked with the imprinting of pro-inflammatory properties and promotion of colon cancer.

TH17 immune cells, a recently discovered subset of CD4+ T-helper cells, are known to play important role in pathogenesis of several autoimmune diseases, inflammatory disorders and cancers. Although Notch ligand DLL4 was shown to drive TH17 polarization, downstream pathways conducting those signals are unknown. We demonstrated that the Notch signaling pathway has an important role in TH17 polarization. We found that gamma secretase inhibitors (GSI) that inhibit Notch signaling blocked the in-vitro polarization of mouse or human naïve CD4+ T cells towards the TH17 pathway without affecting cell proliferation. Next, we showed that, among various Notch receptors, Notch-1 is upregulated in TH17 polarizing cells and that knocking down Notch-1 by siRNA inhibited TH17 polarization. We further discovered that, in addition to polarizing naïve T cells towards TH17 pathway, Notch-1 is important for maintenance of this phenotype. Furthermore, reporter luciferase assays and chromatin immunoprecipitation (ChIP) assays suggest that the IL-17 as well as RORC promoters are direct transcriptional targets of Notch-1. Finally, in-vivo administration of GSI inhibits TH17 mediated disease progression in mouse experimental autoimmune encephalomyelitis model of multiple sclerosis. Thus our data suggest a key role for Notch signaling, especially Notch-1, in TH17 polarization.

Graft versus Host disease (GVHD) is a major lethal complication of allogeneic hematopoietic stem cell transplantation (HSCT). As skin is one of the major organs involved and the most accessible, it serves as an ideal organ site to further understand the pathogenesis and progression of acute GVHD and could serve as a window into pathophysiology of other organ sites. Cytokine network aberrations are a central feature of the pathogenesis of acute cutaneous GVHD, terminating in the hallmark of premature apoptosis of keratinocytes. The purpose of this study is to delineate the cytokine network aberrations at the molecular and cellular level in affected skin from patients with acute GVHD with the goal of developing novel therapeutic approaches to defined targets with the goal of preventing or reducing acute GVHD. We performed immuno-phenotypic profiling of acute cutaneous GVHD biopsies determining relative numbers of various types of immunocytes including T cells, dendritic cells, and macrophages. Cytokine expression (IFNγ and TNFα) was determined by RT-PCR on RNA extracted from eight different lesional skin and two non-lesional biopsies. We analyzed for TH-1 (IFN γ and TNFα), TH-2 (IL-4) and TH-17 (IL-17A, IL-22) cytokine mRNAs. We observed that TH-1 cytokine mRNAs were detected in 7 out of 8 different lesional skin biopsies but none of two nonlesional skin biopsies. Interestingly TH-2 and TH-17 cytokine mRNAs were not detectable in acute cutaneous GVHD lesions or nonlesional skin biopsies. RNA extracted from a 2-way mixed lymphocyte reaction (MLR) served as a positive control for these RT-PCR results. Given recent data that suggested that Notch-1 regulated TH-1 polarization by transcriptionally controlling the Tbx gene (MinterLM et al 2005), we hypothesized that inhibiting Notch signaling might be of potential therapeutic importance given these results of TH-1 polarization in acute skin GVHD. To block Notch signaling we utilized several pharmacological gamma secretase inhibitors (which may have therapeutic applications), and supplemented this pan-Notch receptor inhibition approach by use of a Notch-1 specific siRNA. Preliminary studies suggest that both approaches reduce IFN γ levels in allogeneic T cell responses in-vitro. Further experiments are in progress to confirm these findings and to determine the molecular mechanism. This study begins to define the cytokine network operative within acute cutaneous GVHD lesions highlighting the finding that TH-1 rather than TH-17 cytokines may be the more important target.