The ABCs of Antigen Presentation by Stromal Non-Professional Antigen-Presenting Cells

Professional antigen-presenting cells (APCs), such as dendritic cells and macrophages, are known for their ability to present exogenous antigens to T cells. However, many other cell types, including endothelial cells, fibroblasts, and lymph node stromal cells, are also capable of presenting exogenous antigens to either CD8+ or CD4+ T cells via cross-presentation or major histocompatibility complex (MHC) class II-mediated presentation, respectively. Antigen presentation by these stromal nonprofessional APCs differentially affect T cell function, depending on the type of cells that present the antigen, as well as the local (inflammatory) micro-environment. It has been recently appreciated that nonprofessional APCs can, as such, orchestrate immunity against pathogens, tumor survival, or rejection, and aid in the progression of various auto-immune pathologies. Therefore, the interest for these nonprofessional APCs is growing as they might be an important target for enhancing various immunotherapies. In this review, the different nonprofessional APCs are discussed, as well as their functional consequences on the T cell response, with a focus on immuno-oncology.

Multiplexed immunofluorescence identifies high stromal CD68+PD-L1+ macrophages as a predictor of improved survival in triple negative breast cancer

Triple negative breast cancer (TNBC) comprises 10-15% of all breast cancers and has a poor prognosis with a high risk of recurrence within 5 years. PD-L1 is an important biomarker for patient selection for immunotherapy but its cellular expression and co-localization within the tumour immune microenvironment and associated prognostic value is not well defined. We aimed to characterise the phenotypes of immune cells expressing PD-L1 and determine their association with overall survival (OS) and breast cancer-specific survival (BCSS). Using tissue microarrays from a retrospective cohort of TNBC patients from St George Hospital, Sydney (n = 244), multiplexed immunofluorescence (mIF) was used to assess staining for CD3, CD8, CD20, CD68, PD-1, PD-L1, FOXP3 and pan-cytokeratin on the Vectra Polaris™ platform and analysed using QuPath. Cox multivariate analyses showed high CD68+PD-L1+ stromal cell counts were associated with improved prognosis for OS (HR 0.56, 95% CI 0.33-0.95, p = 0.030) and BCSS (HR 0.47, 95% CI 0.25-0.88, p = 0.018) in the whole cohort and in patients receiving chemotherapy, improving incrementally upon the predictive value of PD-L1+ alone for BCSS. These data suggest that CD68+PD-L1+ status can provide clinically useful prognostic information to identify sub-groups of patients with good or poor prognosis and guide treatment decisions in TNBC.

IL-1-driven stromal-neutrophil interactions define a subset of patients with inflammatory bowel disease that does not respond to therapies

Current inflammatory bowel disease (IBD) therapies are ineffective in a high proportion of patients. Combining bulk and single-cell transcriptomics, quantitative histopathology and in situ localization across three cohorts of patients with IBD (total n = 376), we identify coexpressed gene modules within the heterogeneous tissular inflammatory response in IBD that map to distinct histopathological and cellular features (pathotypes). One of these pathotypes is defined by high neutrophil infiltration, activation of fibroblasts and vascular remodeling at sites of deep ulceration. Activated fibroblasts in the ulcer bed display neutrophil-chemoattractant properties that are IL-1R, but not TNF, dependent. Pathotype-associated neutrophil and fibroblast signatures are increased in nonresponders to several therapies across four independent cohorts (total n = 343). The identification of distinct, localized, tissular pathotypes will aid precision targeting of current therapeutics and provides a biological rationale for IL-1 signaling blockade in ulcerating disease.

Immune status of decidual macrophages is dependent on the CCL2/CCR2/JAK2 pathway during early pregnancy

PROBLEM

Decidual macrophages (dMφ ) play an important role in the formation of maternal-fetal immune tolerance. However, factors that influence the immune status of dMφ and the related potential mechanisms have not been elucidated to date.

METHOD OF STUDY

The gene transcription in dMφ , decidual stromal cells (DSCs), extravillous trophoblasts (EVTs), and peripheral monocytes (pMo) from human samples were measured using real-time polymerase chain reaction (PCR). Monocyte-DSC co-culture was established to explore whether DSCs influenced dMφ polarization via C-C motif ligand 2 (CCL2)-C-C chemokine receptor (CCR2) binding using flow cytometry. In vivo, changes in dMφ percentage and M1 and M2 marker expression after treatment with CCR2 or Janus kinase 2 (JAK2) inhibitor were detected with flow cytometry. Embryo resorption percentages in the above groups were also analyzed.

RESULTS

We found that dMφ were an M1/M2 mixed status at the maternal-fetal interface during early pregnancy. CCL2 influenced the immune status of dMφ in an autocrine and paracrine manner. As a downstream regulator of CCR2 and triggers the Stat3 pathway, JAK2 was found to be essential for dMφ homeostasis in vivo. JAK2 inhibitor decreased the dMφ proportion and attenuated Ki67, CD36, CD86, CD206, TNF, and IL-10 expression in dMφ at E8.5 d. Moreover, CCR2-JAK2 pathway inhibition decreased the width of the placental labyrinth layer, further influencing the pregnancy outcome.

CONCLUSION

The M1/M2 mixed immune status of dMφ was regulated by DSCs via CCR2, and the CCL2/CCR2/JAK2 pathway was essential for the immune status of dMφ and the outcome of early pregnancy.

The subunits of IL-12, originating from two distinct cells, can functionally synergize to protect against pathogen dissemination in vivo

Cytokines are typically single gene products, except for the heterodimeric interleukin (IL)-12 family. The two subunits (IL-12p40 and IL-12p35) of the prototype IL-12 are known to be simultaneously co-expressed in activated myeloid cells, which secrete the fully active heterodimer to promote interferon (IFN)γ production in innate and adaptive cells. We find that chimeric mice containing mixtures of cells that can only express either IL-12p40 or IL-12p35, but not both together, generate functional IL-12. This alternate two-cell pathway requires IL-12p40 from hematopoietic cells to extracellularly associate with IL-12p35 from radiation-resistant cells. The two-cell mechanism is sufficient to propel local T cell differentiation in sites distal to the initial infection and helps control systemic dissemination of a pathogen, although not parasite burden, at the site of infection. Broadly, this suggests that early secretion of IL-12p40 monomers by sentinel cells at the infection site may help prepare distal host tissues for potential pathogen arrival.

T Cell-Mediated Antitumor Immunity Cooperatively Induced By TGFβR1 Antagonism and Gemcitabine Counteracts Reformation of the Stromal Barrier in Pancreatic Cancer

The desmoplastic stroma of pancreatic cancers forms a physical barrier that impedes intratumoral drug delivery. Attempts to modulate the desmoplastic stroma to increase delivery of administered chemotherapy have not shown positive clinical results thus far, and preclinical reports in which chemotherapeutic drugs were coadministered with antistromal therapies did not universally demonstrate increased genotoxicity despite increased intratumoral drug levels. In this study, we tested whether TGFβ antagonism can break the stromal barrier, enhance perfusion and tumoral drug delivery, and interrogated cellular and molecular mechanisms by which the tumor prevents synergism with coadministered gemcitabine. TGFβ inhibition in genetically engineered murine models (GEMM) of pancreas cancer enhanced tumoral perfusion and increased intratumoral gemcitabine levels. However, tumors rapidly adapted to TGFβ-dependent stromal modulation, and intratumoral perfusion returned to pre-treatment levels upon extended TGFβ inhibition. Perfusion was governed by the phenotypic identity and distribution of cancer-associated fibroblasts (CAF) with the myelofibroblastic phenotype (myCAFs), and myCAFs which harbored unique genomic signatures rapidly escaped the restricting effects of TGFβ inhibition. Despite the reformation of the stromal barrier and reversal of initially increased intratumoral exposure levels, TGFβ inhibition in cooperation with gemcitabine effectively suppressed tumor growth via cooperative reprogramming of T regulatory cells and stimulation of CD8 T cell-mediated antitumor activity. The antitumor activity was further improved by the addition of anti-PD-L1 immune checkpoint blockade to offset adaptive PD-L1 upregulation induced by TGFβ inhibition. These findings support the development of combined antistroma anticancer therapies capable of impacting the tumor beyond the disruption of the desmoplastic stroma as a physical barrier to improve drug delivery.

Developing ovine mammary terminal duct lobular units have a dynamic mucosal and stromal immune microenvironment

The human breast and ovine mammary gland undergo striking levels of postnatal development, leading to formation of terminal duct lobular units (TDLUs). Here we interrogate aspects of sheep TDLU growth as a model of breast development and to increase understanding of ovine mammogenesis. The distributions of epithelial nuclear Ki67 positivity differ significantly between younger and older lambs. Ki67 expression is polarised to the leading edge of the developing TDLUs. Intraepithelial ductal macrophages exhibit periodicity and considerably increased density in lambs approaching puberty. Stromal macrophages are more abundant centrally than peripherally. Intraepithelial T lymphocytes are more numerous in older lambs. Stromal hotspots of Ki67 expression colocalize with immune cell aggregates that exhibit distinct organisation consistent with tertiary lymphoid structures. The lamb mammary gland thus exhibits a dynamic mucosal and stromal immune microenvironment and constitutes a valuable model system that provides new insights into postnatal breast development.

Adenovirus vector vaccination reprograms pulmonary fibroblastic niches to support protective inflating memory CD8+ T cells

Pathogens and vaccines that produce persisting antigens can generate expanded pools of effector memory CD8+ T cells, described as memory inflation. While properties of inflating memory CD8+ T cells have been characterized, the specific cell types and tissue factors responsible for their maintenance remain elusive. Here, we show that clinically applied adenovirus vectors preferentially target fibroblastic stromal cells in cultured human tissues. Moreover, we used cell-type-specific antigen targeting to define critical cells and molecules that sustain long-term antigen presentation and T cell activity after adenovirus vector immunization in mice. While antigen targeting to myeloid cells was insufficient to activate antigen-specific CD8+ T cells, genetic activation of antigen expression in Ccl19-cre-expressing fibroblastic stromal cells induced inflating CD8+ T cells. Local ablation of vector-targeted cells revealed that lung fibroblasts support the protective function and metabolic fitness of inflating memory CD8+ T cells in an interleukin (IL)-33-dependent manner. Collectively, these data define a critical fibroblastic niche that underpins robust protective immunity operating in a clinically important vaccine platform.

Single-cell dissection of cellular components and interactions shaping the tumor immune phenotypes in ovarian cancer

Distinct T cell infiltration patterns, i.e., immune infiltrated, excluded, and desert, result in different responses to cancer immunotherapies. However, the key determinants and biology underpinning these tumor immune phenotypes remain elusive. Here, we provide a high-resolution dissection of the entire tumor ecosystem through single-cell RNA-sequencing analysis of 15 ovarian tumors. Immune-desert tumors are characterized by unique tumor cell-intrinsic features, including metabolic pathways and low antigen presentation, and an enrichment of monocytes and immature macrophages. Immune-infiltrated and -excluded tumors differ markedly in their T cell composition and fibroblast subsets. Furthermore, our study reveals chemokine receptor-ligand interactions within and across compartments as potential mechanisms mediating immune cell infiltration, exemplified by the tumor cell-T cell cross talk via CXCL16-CXCR6 and stromal-immune cell cross talk via CXCL12/14-CXCR4. Our data highlight potential molecular mechanisms that shape the tumor immune phenotypes and may inform therapeutic strategies to improve clinical benefit from cancer immunotherapies.

Stromal-immune cell crosstalk fundamentally alters the lung microenvironment following tissue insult

Communication between stromal and immune cells is essential to maintain tissue homeostasis, mount an effective immune response and promote tissue repair. This 'crosstalk' occurs in both the steady state and following a variety of insults, for example, in response to local injury, at sites of infection or cancer. What do we mean by crosstalk between cells? Reciprocal activation and/or regulation occurs between immune and stromal cells, by direct cell contact and indirect mechanisms, including the release of soluble cytokines. Moving beyond cell-to-cell contact, this review investigates the complexity of 'cross-space' cellular communication. We highlight different examples of cellular communication by a variety of lung stromal and immune cells following tissue insults. This review examines how the 'geography of the lung microenvironment' is altered in various disease states; more specifically, we investigate how this influences lung epithelial cells and fibroblasts via their communication with immune cells and each other.

Redefining macrophage and neutrophil biology in the metastatic cascade

Tumor cells metastasize to distant organs through a complex series of events that are driven by tumor intrinsic and extrinsic factors. In particular, non-malignant stromal cells, including immune cells, modify tumor metastatic behavior. Of these cells, tumor-associated innate immune cells, particularly macrophages and neutrophils, suppress the cytotoxic activity of innate and adaptive killer cells and interact with tumor cells to promote their growth and malignancy. These findings in mouse cancer models suggest that targeting these sub-populations of immune cells holds therapeutic promise in treating metastatic disease. In this review, we describe the origin and role of the macrophages, neutrophils, and their progenitors in the metastatic cascade and suggest strategies that might enhance cancer therapy.

Effector and stem-like memory cell fates are imprinted in distinct lymph node niches directed by CXCR3 ligands

T cells dynamically interact with multiple, distinct cellular subsets to determine effector and memory differentiation. Here, we developed a platform to quantify cell location in three dimensions to determine the spatial requirements that direct T cell fate. After viral infection, we demonstrated that CD8+ effector T cell differentiation is associated with positioning at the lymph node periphery. This was instructed by CXCR3 signaling since, in its absence, T cells are confined to the lymph node center and alternatively differentiate into stem-like memory cell precursors. By mapping the cellular sources of CXCR3 ligands, we demonstrated that CXCL9 and CXCL10 are expressed by spatially distinct dendritic and stromal cell subsets. Unlike effector cells, retention of stem-like memory precursors in the paracortex is associated with CCR7 expression. Finally, we demonstrated that T cell location can be tuned, through deficiency in CXCL10 or type I interferon signaling, to promote effector or stem-like memory fates.

Control of PD-L1 expression in CLL-cells by stromal triggering of the Notch-c-Myc-EZH2 oncogenic signaling axis

Chronic lymphocytic leukemia (CLL) is the most common leukemia in adults. Emerging data suggest that CLL-cells efficiently evade immunosurveillance. T-cell deficiencies in CLL include immuno(metabolic) exhaustion that is achieved by inhibitory molecules, with programmed cell death 1/programmed cell death ligand 1 (PD-L1) signaling emerging as a major underlying mechanism. Moreover, CLL-cells are characterized by a close and recurrent interaction with their stromal niches in the bone marrow and lymph nodes. Here, they receive nurturing signals within a well-protected environment. We could previously show that the interaction of CLL-cells with stroma leads to c-Myc activation that is followed by metabolic adaptations. Recent data indicate that c-Myc also controls expression of the immune checkpoint molecule PD-L1. Therefore, we sought out to determine the role of stromal contact for the CLL-cells' PD-L1 expression and thus their immuno-evasive phenotype.To do so, we analyzed PD-L1 expression on CLL cell (subsets) in untreated patients and on healthy donor-derived B-cells. Impact of stromal contact on PD-L1 expression on CLL-cells and the underlying signaling pathways were assessed in well-established in vitro niche models. Ex vivo and in vitro findings were validated in the Eµ-TCL1 transgenic CLL mouse model.We found increased PD-L1 expression on CLL-cells as compared with B-cells that was further enhanced in a cell-to-cell contact-dependent manner by stromal cells. In fact, circulating recent stromal-niche emigrants displayed higher PD-L1 levels than long-time circulating CLL-cells. Using our in vitro niche model, we show that a novel Notch-c-Myc-enhancer of zeste homolog 2 (EZH2) signaling axis controls PD-L1 upregulation. Ultimately, elevated PD-L1 levels conferred increased resistance towards activated autologous T-cells.In summary, our findings support the notion that the CLL microenvironment contributes to immune escape variants. In addition, several targetable molecules (eg, Notch or EZH2) could be exploited in view of improving immune responses in patients with CLL, which warrants further in-depth investigation.

Tenascin-W Is a Novel Stromal Marker in Biliary Tract Cancers

Extrahepatic cancers of the biliary system are typically asymptomatic until after metastasis, which contributes to their poor prognosis. Here we examined intrahepatic cholangiocarcinomas (n = 8), carcinomas of perihilar bile ducts (n = 7), carcinomas of the gallbladder (n = 11) and hepatic metastasis from carcinomas of the gallbladder (n = 4) for the expression of the extracellular matrix glycoproteins tenascin-C and tenascin-W. Anti-tenascin-C and anti-tenascin-W immunoreactivity was found in all biliary tract tumors examined. Unlike tenascin-C, tenascin-W was not detected in normal hepatobiliary tissue. Tenascin-W was also expressed by the cholangiocarcinoma-derived cell line Huh-28. However, co-culture of Huh-28 cells with immortalized bone marrow-derived stromal cells was necessary for the formation and organization of tenascin-W fibrils in vitro. Our results indicate that tenascin-W may be a novel marker of hepatobiliary tumor stroma, and its absence from many normal tissues suggests that it may be a potential target for biotherapies.

Inhibition of MDM2 Promotes Antitumor Responses in p53 Wild-Type Cancer Cells through Their Interaction with the Immune and Stromal Microenvironment

p53 is a transcription factor that plays a central role in guarding the genomic stability of cells through cell-cycle arrest or induction of apoptosis. However, the effects of p53 in antitumor immunity are poorly understood. To investigate the role of p53 in controlling tumor-immune cell cross-talk, we studied murine syngeneic models treated with HDM201, a potent and selective second-generation MDM2 inhibitor. In response to HDM201 treatment, the percentage of dendritic cells increased, including the CD103⁺ antigen cross-presenting subset. Furthermore, HDM201 increased the percentage of Tbet⁺Eomes⁺ CD8⁺ T cells and the CD8⁺/Treg ratio within the tumor. These immunophenotypic changes were eliminated with the knockout of p53 in tumor cells. Enhanced expression of CD80 on tumor cells was observed in vitro and in vivo, which coincided with T-cell-mediated tumor cell killing. Combining HDM201 with PD-1 or PD-L1 blockade increased the number of complete tumor regressions. Responding mice developed durable, antigen-specific memory T cells and rejected subsequent tumor implantation. Importantly, antitumor activity of HDM201 in combination with PD-1/PD-L1 blockade was abrogated in p53-mutated and knockout syngeneic tumor models, indicating the effect of HDM201 on the tumor is required for triggering antitumor immunity. Taken together, these results demonstrate that MDM2 inhibition triggers adaptive immunity, which is further enhanced by blockade of PD-1/PD-L1 pathway, thereby providing a rationale for combining MDM2 inhibitors and checkpoint blocking antibodies in patients with wild-type p53 tumors. SIGNIFICANCE: This study provides a mechanistic rationale for combining checkpoint blockade immunotherapy with MDM2 inhibitors in patients with wild-type p53 tumors.

Increased Stromal Infiltrating Lymphocytes Are Associated with the Risk of Disease Progression in Mesenchymal Circulating Tumor Cell-Positive Primary Breast Cancer Patients

Circulating tumor cells (CTCs) and the immune infiltration of tumors are closely related to clinical outcomes. This study aimed to verify the influence of stromal lymphocyte infiltration and the immune context of tumor microenvironment on the hematogenous spread and prognosis of 282 chemotherapy naïve primary BC patients. To detect the presence of mesenchymal CTCs, RNA extracted from CD45-depleted peripheral blood was interrogated for the expression of mesenchymal gene transcripts. Tumor-infiltrating lymphocytes (TILs) were detected in the stromal areas by immunohistochemistry, using CD3, CD8, and CD45RO antibodies. The concentrations of 51 plasma cytokines were measured by multiplex bead arrays. TILs infiltration in mesenchymal CTC-positive patients significantly decreased their progression-free survival (HR = 4.88, 95% CI 2.30–10.37, p < 0.001 for CD3^high; HR = 6.17, 95% CI 2.75–13.80, p < 0.001 for CD8^high; HR = 6.93, 95% CI 2.86–16.81, p < 0.001 for CD45RO^high). Moreover, the combination of elevated plasma concentrations of transforming growth factor beta-3 (cut-off 662 pg/mL), decreased monocyte chemotactic protein-3 (cut-off 52.5 pg/mL) and interleukin-15 (cut-off 17.1 pg/mL) significantly increased the risk of disease recurrence (HR = 4.838, 95% CI 2.048–11.427, p < 0.001). Our results suggest a strong impact of the immune tumor microenvironment on BC progression, especially through influencing the dissemination and survival of more aggressive, mesenchymal CTC subtypes.

MiR-7e-5p downregulation promotes transformation of low-grade follicular lymphoma to aggressive lymphoma by modulating an immunosuppressive stroma through the upregulation of FasL in M1 macrophages

BACKGROUND

In follicular lymphoma (FL), histologic transformation to high-grade FL and diffuse large B-cell lymphoma (DLBCL) is a critical adverse step in disease progression. Activation of the oncogene c-MYC and tumor microenvironment remodeling account for FL progression. A panel of microRNA (miRNA) was downregulated in transformed FL (tFL).

METHODS

Differentially expressed miRNAs were systematically compared in 11 lymph nodes from patients at different stages of disease. Expression of miR-7e-5p was analyzed in 46 B-cell lymphomas, including 30 FL tissues and 16 DLBCL tissues. In FL cells, transcriptional regulation of the oncogene c-MYC on its target miR-7e-5p was revealed by Chromatin Immunoprecipitation (ChIP) assay. Exosome, carrying differentially expressed miR-7e-5p was isolated and visualized by transmission electron microscope and fluorescence tracing. The effect of miR-7e-5p on recipient macrophage was determined by target gene quantification, flow cytometry, and TUNEL method in a cocultured system with miR-7e-5p-mimics or inhibitors treatment. Expression of miR-7e-5p targets, macrophage proportions, and clinical parameters were included for correlation analysis.

RESULTS

We determined that downregulation of miR-7e-5p, driven by c-MYC overexpression, was associated with poorer prognosis in FL patients. The decreased expression of miR-7e-5p in lymphoma cells led to a reduced exosomal transfer to surrounding macrophages. As a result, the target gene of miR-7e-5p, Fas ligand (FasL), was upregulated and activated the caspase signaling, which led to the apoptosis of M1 macrophages in tumor stroma. Finally, in transformed FL tissues, overexpression of FasL and activation of caspase proteins was detected in tumor stromal macrophages. Downregulation of miR-7e-5p was associated with poorer clinical outcomes.

CONCLUSION

Downregulation of exosomal miR-7e-5p induces stromal M1 macrophage apoptosis, which leads to immunosurveillance and transformation of FL.

Splenic Hematopoietic and Stromal Cells in Cancer Progression

Tumor-derived secretory factors orchestrate splenic hematopoietic and stromal cells to fuel metastasis. The spleen acts as a reservoir site for hematopoietic stem and progenitor cells, which are rapidly exploited as myeloid-derived suppressor cells at the cost of tumor-reactive lymphoid cells. Splenic erythroid progenitor cells and mesenchymal stromal cells contribute directly and indirectly to both tumor immune escape and the metastatic cascade. Animal models provide valuable mechanistic insights, but their translation to a clinical setting highlights specific challenges and open issues. In this review, we envision the exploitation of the spleen as a source for novel biomarkers and therapeutic approaches.

Cytokine Profiling in Myeloproliferative Neoplasms: Overview on Phenotype Correlation, Outcome Prediction, and Role of Genetic Variants

Among hematologic malignancies, the classic Philadelphia-negative chronic myeloproliferative neoplasms (MPNs) are considered a model of inflammation-related cancer development. In this context, the use of immune-modulating agents has recently expanded the MPN therapeutic scenario. Cytokines are key mediators of an auto-amplifying, detrimental cross-talk between the MPN clone and the tumor microenvironment represented by immune, stromal, and endothelial cells. This review focuses on recent advances in cytokine-profiling of MPN patients, analyzing different expression patterns among the three main Philadelphia-negative (Ph-negative) MPNs, as well as correlations with disease molecular profile, phenotype, progression, and outcome. The role of the megakaryocytic clone as the main source of cytokines, particularly in myelofibrosis, is also reviewed. Finally, we report emerging intriguing evidence on the contribution of host genetic variants to the chronic pro-inflammatory state that typifies MPNs.

Cytokine Profiling in Myeloproliferative Neoplasms: Overview on Phenotype Correlation, Outcome Prediction, and Role of Genetic Variants

Among hematologic malignancies, the classic Philadelphia-negative chronic myeloproliferative neoplasms (MPNs) are considered a model of inflammation-related cancer development. In this context, the use of immune-modulating agents has recently expanded the MPN therapeutic scenario. Cytokines are key mediators of an auto-amplifying, detrimental cross-talk between the MPN clone and the tumor microenvironment represented by immune, stromal, and endothelial cells. This review focuses on recent advances in cytokine-profiling of MPN patients, analyzing different expression patterns among the three main Philadelphia-negative (Ph-negative) MPNs, as well as correlations with disease molecular profile, phenotype, progression, and outcome. The role of the megakaryocytic clone as the main source of cytokines, particularly in myelofibrosis, is also reviewed. Finally, we report emerging intriguing evidence on the contribution of host genetic variants to the chronic pro-inflammatory state that typifies MPNs.

Human Lymph Node Stromal Cells Have the Machinery to Regulate Peripheral Tolerance during Health and Rheumatoid Arthritis

BACKGROUND

In rheumatoid arthritis (RA) the cause for loss of tolerance and anti-citrullinated protein antibody (ACPA) production remains unidentified. Mouse studies showed that lymph node stromal cells (LNSCs) maintain peripheral tolerance through presentation of peripheral tissue antigens (PTAs). We hypothesize that dysregulation of peripheral tolerance mechanisms in human LNSCs might underlie pathogenesis of RA.

METHOD

Lymph node (LN) needle biopsies were obtained from 24 RA patients, 23 individuals positive for RA-associated autoantibodies but without clinical disease (RA-risk individuals), and 14 seronegative healthy individuals. Ex vivo human LNs from non-RA individuals were used to directly analyze stromal cells. Molecules involved in antigen presentation and immune modulation were measured in LNSCs upon interferon γ (IFNγ) stimulation (n = 15).

RESULTS

Citrullinated targets of ACPAs were detected in human LN tissue and in cultured LNSCs. Human LNSCs express several PTAs, transcription factors autoimmune regulator (AIRE) and deformed epidermal autoregulatory factor 1 (DEAF1), and molecules involved in citrullination, antigen presentation, and immunomodulation. Overall, no clear differences between donor groups were observed with exception of a slightly lower induction of human leukocyte antigen-DR (HLA-DR) and programmed cell death 1 ligand (PD-L1) molecules in LNSCs from RA patients.

CONCLUSION

Human LNSCs have the machinery to regulate peripheral tolerance making them an attractive target to exploit in tolerance induction and maintenance.

Tumor microenvironment in gastric cancers

The tumor microenvironment favors the growth and expansion of cancer cells. Many cell types are involved in the tumor microenvironment such as inflammatory cells, fibroblasts, nerves, and vascular endothelial cells. These stromal cells contribute to tumor growth by releasing various molecules to either directly activate the growth signaling in cancer cells or remodel surrounding areas. This review introduces recent advances in findings on the interactions within the tumor microenvironment such as in cancer-associated fibroblasts (CAFs), immune cells, and endothelial cells, in particular those established in mouse gastric cancer models. In mice, myofibroblasts in the gastric stroma secrete R-spondin and support normal gastric stem cells. Most CAFs promote tumor growth in a paracrine manner, but CAF population appears to be heterogeneous in terms of their function and origin, and include both tumor-promoting and tumor-restraining populations. Among immune cell populations, tumor-associated macrophages, including M1 and M2 macrophages, and myeloid-derived suppressor cells (MDSCs), are reported to directly or indirectly promote gastric tumorigenesis by secreting soluble factors or modulating immune responses. Endothelial cells or blood vessels not only fuel tumors with nutrients, but also interact with cancer stem cells and immune cells by secreting chemokines or cytokines, and act as a cancer niche. Understanding these interactions within the tumor microenvironment would contribute to unraveling new therapeutic targets.

B cell zone reticular cell microenvironments shape CXCL13 gradient formation

Through the formation of concentration gradients, morphogens drive graded responses to extracellular signals, thereby fine-tuning cell behaviors in complex tissues. Here we show that the chemokine CXCL13 forms both soluble and immobilized gradients. Specifically, CXCL13+ follicular reticular cells form a small-world network of guidance structures, with computer simulations and optimization analysis predicting that immobilized gradients created by this network promote B cell trafficking. Consistent with this prediction, imaging analysis show that CXCL13 binds to extracellular matrix components in situ, constraining its diffusion. CXCL13 solubilization requires the protease cathepsin B that cleaves CXCL13 into a stable product. Mice lacking cathepsin B display aberrant follicular architecture, a phenotype associated with effective B cell homing to but not within lymph nodes. Our data thus suggest that reticular cells of the B cell zone generate microenvironments that shape both immobilized and soluble CXCL13 gradients.

The Proportion of Tumour-Stroma in Metastatic Lymph Nodes is An Accurately Prognostic Indicator of Poor Survival for Advanced-Stage Colon Cancers

The importance of tumour microenvironment in tumour behaviour has now become clearer. This study aimed to determine the prognostic effect of the proportion of tumour-stroma (PTS) in metastatic lymph nodes of advanced-stage colon cancers (CCs). We investigated PTS in positive lymph nodes of stage III-IV CC patients who underwent surgical treatment between 2004 and 2014. We used a standard approach in methodology. PTS was significantly associated with prognostic factors in the metastatic lymph nodes (perineural invasion [p = 0.031], lymphatic invasion [p = 0.032], invasive margin [p = 0.043], advanced pT [p = 0.020], and margin involvement [p = 0.034]). In addition, the correlations between PTS estimates (R = 0.704 to 0.617, p < 0.001), the reproducibility of the research (Κappa = 0.72-0.68) and the usefulness of the cut-off value (ROC: 50.33%; AUC = 0.752 [0.667-0.857]) were successful. In univariate analysis, 5-year survival was poor for RFS (p < 0.001), OS (p = 0.001) and LR (p = 0.013) in high PTS patients. Multivariate analysis confirmed that high PTS was an independent worse parameter for RFS (HR = 1.32, 95% CI: 1.17-2.55, p = 0.001) and OS (HR = 1.37, 95% CI: 1.25-1 - 2.56, p = 0.009). In this study, we showed that high PTS in metastatic lymph nodes was a successful prognostic marker for advanced-stage CCs. Also, the standard approach we used for the methodology was successful.

STING and IRF3 in stromal fibroblasts enable sensing of genomic stress in cancer cells to undermine oncolytic viral therapy

Cancer-associated fibroblasts (CAFs) perform diverse roles and can modulate therapy responses1. The inflammatory environment within tumours also influences responses to many therapies, including the efficacy of oncolytic viruses2; however, the role of CAFs in this context remains unclear. Furthermore, little is known about the cell signalling triggered by heterotypic cancer cell-fibroblast contacts and about what activates fibroblasts to express inflammatory mediators1,3. Here, we show that direct contact between cancer cells and CAFs triggers the expression of a wide range of inflammatory modulators by fibroblasts. This is initiated following transcytosis of cytoplasm from cancer cells into fibroblasts, leading to the activation of STING and IRF3-mediated expression of interferon-β1 and other cytokines. Interferon-β1 then drives interferon-stimulated transcriptional programs in both cancer cells and stromal fibroblasts and ultimately undermines the efficacy of oncolytic viruses, both in vitro and in vivo. Further, targeting IRF3 solely in stromal fibroblasts restores oncolytic herpes simplex virus function.

Cytokines secreted by stromal cells in TNBC microenvironment as potential targets for cancer therapy

In triple-negative breast cancer (TNBC), the lack of therapeutic markers and effective targeted therapies result in an incurable metastatic disease associated with a poor prognosis. Crosstalks within the tumor microenvironment (TME), including those between cancer and stromal cells, affect the tumor heterogeneity, growth, and metastasis. Previously, we have demonstrated that IL-6, IL-8, and CCL5 play a significant role in TNBC growth and metastasis. In this study, we performed a systematic analysis of cytokine factors secreted from four stromal components (fibroblasts, macrophages, lymphatic endothelial cells, and blood microvascular endothelial cells) induced by four TNBC cell types. Through bioinformatic analysis, we selected putative candidates of secreted factors from stromal cells, which are involved in EMT activity, cell proliferation, metabolism, and matrisome pathways. Among the candidates, LCN2, GM-CSF, CST3, IL-6, IL-8, and CHI3L1 are ranked highly. Significantly, Lipocalin-2 (LCN2) is upregulated in the crosstalk of stromal cells and four different TNBC cells. We validated the increase of LCN2 secreted from four stromal cells induced by TNBC cells. Using a specific LCN2 antibody, we observed the inhibition of TNBC cell growth and migration. Taken together, these results propose secreted factors as molecular targets to treat TNBC progression via crosstalk with stromal components.

In utero estrogenic endocrine disruption alters the stroma to increase extracellular matrix density and mammary gland stiffness

BACKGROUND

In utero endocrine disruption is linked to increased risk of breast cancer later in life. Despite numerous studies establishing this linkage, the long-term molecular changes that predispose mammary cells to carcinogenic transformation are unknown. Herein, we investigated how endocrine disrupting compounds (EDCs) drive changes within the stroma that can contribute to breast cancer susceptibility.

METHODS

We utilized bisphenol A (BPA) as a model of estrogenic endocrine disruption to analyze the long-term consequences in the stroma. Deregulated genes were identified by RNA-seq transcriptional profiling of adult primary fibroblasts, isolated from female mice exposed to in utero BPA. Collagen staining, collagen imaging techniques, and permeability assays were used to characterize changes to the extracellular matrix. Finally, gland stiffness tests were performed on exposed and control mammary glands.

RESULTS

We identified significant transcriptional deregulation of adult fibroblasts exposed to in utero BPA. Deregulated genes were associated with cancer pathways and specifically extracellular matrix composition. Multiple collagen genes were more highly expressed in the BPA-exposed fibroblasts resulting in increased collagen deposition in the adult mammary gland. This transcriptional reprogramming of BPA-exposed fibroblasts generates a less permeable extracellular matrix and a stiffer mammary gland. These phenotypes were only observed in adult 12-week-old, but not 4-week-old, mice. Additionally, diethylstilbestrol, known to increase breast cancer risk in humans, also increases gland stiffness similar to BPA, while bisphenol S does not.

CONCLUSIONS

As breast stiffness, extracellular matrix density, and collagen deposition have been directly linked to breast cancer risk, these data mechanistically connect EDC exposures to molecular alterations associated with increased disease susceptibility. These alterations develop over time and thus contribute to cancer risk in adulthood.

Distribution and storage of inflammatory memory in barrier tissues

Memories of previous immune events enable barrier tissues to rapidly recall distinct environmental exposures. To effectively inform future responses, these past experiences can be stored in cell types that are long-term residents or essential constituents of tissues. There is an emerging understanding that, in addition to antigen-specific immune cells, diverse haematopoietic, stromal, parenchymal and neuronal cell types can store inflammatory memory. Here, we explore the impact of previous immune activity on various cell lineages with the goal of presenting a unified view of inflammatory memory to environmental exposures (such as allergens, antigens, noxious agents and microorganisms) at barrier tissues. We propose that inflammatory memory is distributed across diverse cell types and stored through shifts in cell states, and we provide a framework to guide future experiments. This distribution and storage may promote adaptation or maladaptation in homeostatic, maintenance and disease settings - especially if the distribution of memory favours cellular cooperation during storage or recall.

Exploring immune-related genes with prognostic value in microenvironment of breast cancer from TCGA database

Breast cancer is one of the most common malignancies in women worldwide. Many studies have shown that tumor microenvironment cells, immune cells, and stromal cell infiltration have an important impact on prognosis, so it is important to identify biomarkers for achieving better treatment and prognosis.To better understand the relationship between immune and stromal cell-related genes and prognosis, we screened patients with breast cancer in The Cancer Genome Atlas (TCGA) database and divided them into high and low groups based on immune/stromal scores. We next identified differentially expressed immune-related genes that are significantly associated with the prognosis of patients with breast cancer for functional enrichment analysis and protein-protein interaction networks, respectively. Finally, we selected a separate breast cancer cohort in gene expression synthesis (GEO) for validation.Both immune scores and stromal scores are meaningful in the correlation of subtype classification. Disease-free survival of cases with the high score group of immune scores is statistically longer than the cases in the low score group. Differentially expressed immune-related genes extracted from the comparison can effectively evaluate the prognosis of patients with breast cancer and these genes are primarily involved in immune responses, extracellular matrix, and chemokine activity. At last, we obtained a series of verified tumor immune-related genes that predict the prognosis of patients with breast cancer.Combining the Estimation of Stromal and Immune Cells in Malignant Tumor Tissues using Expression database and the TCGA database to extract the list of tumor microenvironment related genes which may help to outline the prognosis of patients with breast cancer. Some previously overlooked genes have the potential to become additional biomarkers for breast cancer. Further research on these genes can reveal a new understanding of the potential relationship between tumor microenvironment and breast cancer prognosis.

Versican-A Critical Extracellular Matrix Regulator of Immunity and Inflammation

The extracellular matrix (ECM) proteoglycan, versican increases along with other ECM versican binding molecules such as hyaluronan, tumor necrosis factor stimulated gene-6 (TSG-6), and inter alpha trypsin inhibitor (IαI) during inflammation in a number of different diseases such as cardiovascular and lung disease, autoimmune diseases, and several different cancers. These interactions form stable scaffolds which can act as "landing strips" for inflammatory cells as they invade tissue from the circulation. The increase in versican is often coincident with the invasion of leukocytes early in the inflammatory process. Versican interacts with inflammatory cells either indirectly via hyaluronan or directly via receptors such as CD44, P-selectin glycoprotein ligand-1 (PSGL-1), and toll-like receptors (TLRs) present on the surface of immune and non-immune cells. These interactions activate signaling pathways that promote the synthesis and secretion of inflammatory cytokines such as TNFα, IL-6, and NFκB. Versican also influences inflammation by interacting with a variety of growth factors and cytokines involved in regulating inflammation thereby influencing their bioavailability and bioactivity. Versican is produced by multiple cell types involved in the inflammatory process. Conditional total knockout of versican in a mouse model of lung inflammation demonstrated significant reduction in leukocyte invasion into the lung and reduced inflammatory cytokine expression. While versican produced by stromal cells tends to be pro-inflammatory, versican expressed by myeloid cells can create anti-inflammatory and immunosuppressive microenvironments. Inflammation in the tumor microenvironment often contains elevated levels of versican. Perturbing the accumulation of versican in tumors can inhibit inflammation and tumor progression in some cancers. Thus versican, as a component of the ECM impacts immunity and inflammation through regulating immune cell trafficking and activation. Versican is emerging as a potential target in the control of inflammation in a number of different diseases.

Sex-specific adipose tissue imprinting of regulatory T cells

Adipose tissue is an energy store and a dynamic endocrine organ1,2. In particular, visceral adipose tissue (VAT) is critical for the regulation of systemic metabolism3,4. Impaired VAT function-for example, in obesity-is associated with insulin resistance and type 2 diabetes5,6. Regulatory T (Treg) cells that express the transcription factor FOXP3 are critical for limiting immune responses and suppressing tissue inflammation, including in the VAT7-9. Here we uncover pronounced sexual dimorphism in Treg cells in the VAT. Male VAT was enriched for Treg cells compared with female VAT, and Treg cells from male VAT were markedly different from their female counterparts in phenotype, transcriptional landscape and chromatin accessibility. Heightened inflammation in the male VAT facilitated the recruitment of Treg cells via the CCL2-CCR2 axis. Androgen regulated the differentiation of a unique IL-33-producing stromal cell population specific to the male VAT, which paralleled the local expansion of Treg cells. Sex hormones also regulated VAT inflammation, which shaped the transcriptional landscape of VAT-resident Treg cells in a BLIMP1 transcription factor-dependent manner. Overall, we find that sex-specific differences in Treg cells from VAT are determined by the tissue niche in a sex-hormone-dependent manner to limit adipose tissue inflammation.

Topological Tumor Graphs: A Graph-Based Spatial Model to Infer Stromal Recruitment for Immunosuppression in Melanoma Histology

Despite the advent of immunotherapy, metastatic melanoma represents an aggressive tumor type with a poor survival outcome. The successful application of immunotherapy requires in-depth understanding of the biological basis and immunosuppressive mechanisms within the tumor microenvironment. In this study, we conducted spatially explicit analyses of the stromal-immune interface across 400 melanoma hematoxylin and eosin (H&E) specimens from The Cancer Genome Atlas. A computational pathology pipeline (CRImage) was used to classify cells in the H&E specimen into stromal, immune, or cancer cells. The estimated proportions of these cell types were validated by independent measures of tumor purity, pathologists' estimate of lymphocyte density, imputed immune cell subtypes, and pathway analyses. Spatial interactions between these cell types were computed using a graph-based algorithm (topological tumor graphs, TTG). This approach identified two stromal features, namely stromal clustering and stromal barrier, which represented the melanoma stromal microenvironment. Tumors with increased stromal clustering and barrier were associated with reduced intratumoral lymphocyte distribution and poor overall survival independent of existing prognostic factors. To explore the genomic basis of these TTG-derived stromal phenotypes, we used a deep learning approach integrating genomic (copy number) and transcriptomic data, thereby inferring a compressed representation of copy number-driven alterations in gene expression. This integrative analysis revealed that tumors with high stromal clustering and barrier had reduced expression of pathways involved in naïve CD4 signaling, MAPK, and PI3K signaling. Taken together, our findings support the immunosuppressive role of stromal cells and T-cell exclusion within the vicinity of melanoma cells. SIGNIFICANCE: Computational histology-based stromal phenotypes within the tumor microenvironment are significantly associated with prognosis and immune exclusion in melanoma.

Bone Marrow Stromal Cells Drive Key Hallmarks of B Cell Malignancies

All B cell leukaemias and a substantial fraction of lymphomas display a natural niche residency in the bone marrow. While the bone marrow compartment may only be one of several sites of disease manifestations, the strong clinical significance of minimal residual disease (MRD) in the bone marrow strongly suggests that privileged niches exist in this anatomical site favouring central elements of malignant transformation. Here, the co-existence of two hierarchical systems, originating from haematopoietic and mesenchymal stem cells, has extensively been characterised with regard to regulation of the former (blood production) by the latter. How these two systems cooperate under pathological conditions is far less understood and is the focus of many current investigations. More recent single-cell sequencing techniques have now identified an unappreciated cellular heterogeneity of the bone marrow microenvironment. How each of these cell subtypes interact with each other and regulate normal and malignant haematopoiesis remains to be investigated. Here we review the evidences of how bone marrow stroma cells and malignant B cells reciprocally interact. Evidently from published data, these cell-cell interactions induce profound changes in signalling, gene expression and metabolic adaptations. While the past research has largely focussed on understanding changes imposed by stroma- on tumour cells, it is now clear that tumour-cell contact also has fundamental ramifications for the biology of stroma cells. Their careful characterisations are not only interesting from a scientific biological viewpoint but also relevant to clinical practice: Since tumour cells heavily depend on stroma cells for cell survival, proliferation and dissemination, interference with bone marrow stroma-tumour interactions bear therapeutic potential. The molecular characterisation of tumour-stroma interactions can identify new vulnerabilities, which could be therapeutically exploited.

Diminished CD68+ Cancer-Associated Fibroblast Subset Induces Regulatory T-Cell (Treg) Infiltration and Predicts Poor Prognosis of Oral Squamous Cell Carcinoma Patients

Although cancer-associated fibroblasts (CAFs) are crucial stromal cells, characterizing their heterogeneity is far from complete. This study reports a novel subset of CAFs in oral squamous cell carcinoma (OSCC), which positively expressed CD68, the classic marker of macrophages. The spatial and temporal distribution of the CD68⁺ CAF subset of OSCC (n = 104) was determined by CD68/actin alpha 2, smooth muscle (ACTA2+; α-SMA) immunohistochemistry of serial sections. The CD68⁺ α-SMA⁺ CAF subset was elevated from dysplasia to OSCC. Moreover, although both the tumor center and invasive front harbor an abundant CD68⁺ CAF subset, patients with low-CD68⁺ CAFs in the tumor center showed more recurrence after operation and shorter survival time, indicating the different function of CD68⁺ CAFs in tumor initiation and progression. Functional analysis in the OSCC-CAF co-culture system found knockdown of CD68 did not change the phenotype of CAFs, tumor growth, or migration. Unexpectedly, low-CD68⁺ CAFs were associated with aberrant immune balance. A high proportion of tumor-supportive Tregs was found in patients with low-CD68⁺ CAFs. Mechanistically, knockdown of CD68 in CAFs contributed to the up-regulation of chemokine CCL17 and CCL22 of tumor cells to enhance Treg recruitment. Thus, up-regulated CD68⁺ fibroblasts participate in tumor initiation, but the low-CD68⁺ CAF subset in OSCC is conducive to regulatory T-cell (Treg) recruitment in the tumor microenvironment and contribute to poor prognosis of OSCC patients.

Stromal PD-1+ tumor-associated macrophages predict poor prognosis in lung adenocarcinoma

Immunotherapies targeting programmed cell death protein 1 (PD-1)/PD-1 ligand (PD-L1) axis have been emerging as a promising therapeutic strategy to treat lung cancer. PD-1 is preferentially expressed by activated T lymphocytes; but whether/how its expression by tumor-associated macrophages (TAMs) in lung adenocarcinoma remains elusive. Herein, we investigate the frequency of PD-1 expression on TAMs in mouse allografts by flow cytometry analysis and evaluate the spatial distribution and clinicopathological significance of PD-1⁺ TAMs in 213 cases of human lung adenocarcinoma specimens by immunohistochemical staining. We find the expression of PD-1 by both mouse and human TAMs. Mouse PD-1⁺ TAMs possess unique transcriptional profile as compared to PD-1^- TAMs. Furthermore, PD-1 is preferentially expressed by CD163⁺ TAMs in the tumor stroma than those in the tumor islets of lung adenocarcinoma. Stromal PD-1⁺ TAM infiltration is an independent predictor of reduced survival as determined by univariate (P < .001) and multivariate (P = .023) analysis. Moreover, patients with high stromal PD-1⁺ TAMs but low tumor cell PD-L1 expression have the shortest survival (P = .0001). Our study demonstrates that PD-1⁺ TAMs have unique gene expression characteristics and PD-1⁺ TAMs in the tumor stroma is a potential prognostic factor in lung adenocarcinoma, suggesting that a better understanding of PD-1⁺ TAMs will be beneficial for immunotherapy of lung adenocarcinoma patients.

Immunohistochemical Expression of Programmed Death Ligand-1 (PDL-1) in Colorectal carcinoma and Its Correlation with Stromal Tumor Infiltrating Lymphocytes

OBJECTIVES

Detection of Immunohistochemical (IHC) expression of PDL-1 by tumor cells and stromal tumor infiltrating lymphocytes (TILs) in colorectal carcinoma, to investigate the possibility of using it as a targeted therapy, as well as, correlation of this expression with the clinico-pathologic parameters of the tumors.

MATERIALS AND METHODS

Colorectal tissue sections were collected from 60 colectomy specimens were taken from Kasr El Ainy Hospital, Faculty of Medicine, Cairo University. Exclusion criteria included cases with missing data and cases who received chemotherapy or radiotherapy. IHC expression of PDL-1 was investigated in tumor cells (T) and stromal TILs separately. PDL-1 positivity was defined as PDL-1 expression on ≥ 5% of membranous positive cell staining of any intensity.

RESULTS

PDL-1 (T) expression was detected in 25% of cases and showed statistically significant correlation with higher tumor grade and right sided colon tumors (P value < 0.05). PD-L1 stromal TILs expression was detected in 38.3 % of cases. Insignificant statistical relation between Stromal TILs PDL-1 expression and the tumor extent (T) was detected (P value = 0.07), however, the expression of PDL-1 in lymphocytes was inversely proportional to the tumor extent (invasion). There were linear relation between PDL-1 expression stromal (TILs) (33.3%) and PDL-1 expression in tumor cells (28.2%) and positive lympho-vascular invasion but it was statistically insignificant (P value = 0.4 and 0.2 respectively). Despite there were no statistical relation between either PDL-1 (T) and PDL-stromal TILS and Perineural invasion (P value =1 and 0.5) but inverse relation was noticed with more PDL-1 expression in tumor cells (24.5%) and TILS (40.8%) with negative Perineural invasion.

CONCLUSION

Our results supported PDL-1 expression in CRC by both TC and TILs, with higher expression in subset of tumors that are high grade highlighting them as candidates for anti- PD-1/PDL-1 therapy.
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The reciprocal regulation between host tissue and immune cells in pancreatic ductal adenocarcinoma: new insights and therapeutic implications

Pancreatic ductal adenocarcinoma (PDAC) is the fourth leading cause of cancer-related death and is one of the most difficult-to-treat cancers. Surgical resection and adjuvant therapy have limited effects on the overall survival of PDAC patients. PDAC exhibits an immunosuppressive microenvironment, the immune response predicts survival, and activation of immune system has the potential to produce an efficacious PDAC therapy. However, chimeric antigen receptor T (CAR-T) cell immunotherapy and immune checkpoint blockade (ICB), which have produced unprecedented clinical benefits in a variety of different cancers, produce promising results in only some highly selected patients with PDAC. This lack of efficacy may be because existing immunotherapies mainly target the interactions between cancer cells and immune cells. However, PDAC is characterized by an abundant tumor stroma that includes a heterogeneous mixture of immune cells, fibroblasts, endothelial cells, neurons and some molecular events. Immune cells engage in extensive and dynamic crosstalk with stromal components in the tumor tissue in addition to tumor cells, which subsequently impacts tumor suppression or promotion to a large extent. Therefore, exploration of the interactions between the stroma and immune cells may offer new therapeutic opportunities for PDAC. In this review, we discuss how infiltrating immune cells influence PDAC development and explore the contributions of complex components to the immune landscape of tumor tissue. The roles of stromal constituents in immune modulation are emphasized. We also predict potential therapeutic strategies to target signals in the immune network in the abundant stromal microenvironment of PDAC.

Primary prostate cancer educates bone stroma through exosomal pyruvate kinase M2 to promote bone metastasis

Prostate cancer (PCa) metastasizes selectively to bone through unknown mechanisms. In the current study, we identified exosome-mediated transfer of pyruvate kinase M2 (PKM2) from PCa cells into bone marrow stromal cells (BMSCs) as a novel mechanism through which primary tumor-derived exosomes promote premetastatic niche formation. We found that PKM2 up-regulates BMSC CXCL12 production in a HIF-1α-dependent fashion, which subsequently enhances PCa seeding and growth in the bone marrow. Furthermore, serum-derived exosomes from patients with either primary PCa or PCa metastasis, as opposed to healthy men, reveal that increased exosome PKM2 expression is associated with metastasis, suggesting clinical relevance of exosome PKM2 in PCa. Targeting the exosome-induced CXCL12 axis diminished exosome-mediated bone metastasis. In summary, primary PCa cells educate the bone marrow to create a premetastatic niche through primary PCa exosome-mediated transfer of PKM2 into BMSCs and subsequent up-regulation of CXCL12. This novel mechanism indicates the potential for exosome PKM2 as a biomarker and suggests therapeutic targets for PCa bone metastasis.

Targeting amphiregulin (AREG) derived from senescent stromal cells diminishes cancer resistance and averts programmed cell death 1 ligand (PD-L1)-mediated immunosuppression

Aging is characterized by a progressive loss of physiological integrity, while cancer represents one of the primary pathological factors that severely threaten human lifespan and healthspan. In clinical oncology, drug resistance limits the efficacy of most anticancer treatments, and identification of major mechanisms remains a key to solve this challenging issue. Here, we highlight the multifaceted senescence-associated secretory phenotype (SASP), which comprises numerous soluble factors including amphiregulin (AREG). Production of AREG is triggered by DNA damage to stromal cells, which passively enter senescence in the tumor microenvironment (TME), a process that remarkably enhances cancer malignancy including acquired resistance mediated by EGFR. Furthermore, paracrine AREG induces programmed cell death 1 ligand (PD-L1) expression in recipient cancer cells and creates an immunosuppressive TME via immune checkpoint activation against cytotoxic lymphocytes. Targeting AREG not only minimized chemoresistance of cancer cells, but also restored immunocompetency when combined with classical chemotherapy in humanized animals. Our study underscores the potential of in vivo SASP in driving the TME-mediated drug resistance and shaping an immunosuppressive niche, and provides the proof of principle of targeting major SASP factors to improve therapeutic outcome in cancer medicine, the success of which can substantially reduce aging-related morbidity and mortality.

Monocytic Myeloid Derived Suppressor Cells in Hematological Malignancies

In the era of novel agents and immunotherapies in solid and liquid tumors, there is an emerging need to understand the cross-talk between the neoplastic cells, the host immune system, and the microenvironment to mitigate proliferation, survival, migration and resistance to drugs. In the microenvironment of hematological tumors there are cells belonging to the normal bone marrow, extracellular matrix proteins, adhesion molecules, cytokines, and growth factors produced by both stromal cells and neoplastic cells themselves. In this context, myeloid suppressor cells are an emerging sub-population of regulatory myeloid cells at different stages of differentiation involved in cancer progression and chronic inflammation. In this review, monocytic myeloid derived suppressor cells and their potential clinical implications are discussed to give a comprehensive vision of their contribution to lymphoproliferative and myeloid disorders.

Interleukin-22 secreted by ectopic endometrial stromal cells and natural killer cells promotes the recruitment of macrophages through promoting CCL2 secretion

PROBLEM

During endometriosis, there is an increase in the number of dysfunctional macrophages; however, the mechanisms underlying macrophage recruitment are not well understood. The aim of the present study was to determine the role of natural killer (NK) cell-mediated secretion of chemokine (C-C motif) ligand 2 (CCL2) from endometrial stromal cells (ESCs) in the recruitment of macrophages.

METHOD OF STUDY

Normal ESCs (nESC) and ectopic ESCs (eESCs) were separately co-cultured with NK cells for a macrophage chemotaxis assay, and the number of chemotactic macrophages was counted. The expression of interleukin-22 (IL-22) and IL-22 receptors was detected by ELISA and flow cytometry, respectively. eESCs were treated with 0.01, 0.1, and 1 ng/mL recombinant human IL-22 (rhIL-22) to determine the most effective concentration for stimulating CCL2 production. Following treatment with 1 ng/mL rhIL-22, secretion of CCL2 was detected from both the eESC monoculture and the eESC/NK co-culture.

RESULTS

Compared with the eESC monoculture, the eESC/NK co-culture recruited a significantly higher number of chemotactic macrophages. There was also an increase in the levels of IL-22 and CCL2 secreted when eESCs were co-cultured compared with the monoculture. Treatment with rhIL-22 resulted in an increase in the levels of CCL2 secreted by eESCs, and the IL-22-induced CCL2 secretion was reversed by the IL-22 antagonist, αIL-22. Increased expression of IL-22 resulted in an increase in the number of chemotactic macrophages, but was reversed by αIL-22 and CCL2 antagonist (αCCL2).

CONCLUSION

Interleukin-22 and CCL2 secretion by eESCs stimulated by NK cells contributes to the induction of macrophage recruitment and is thus implicated in the development of endometriosis.

Hyperglycemia and T Cell infiltration are associated with stromal and epithelial prostatic hyperplasia in the nonobese diabetic mouse

BACKGROUND

Prostatic inflammation and various proinflammatory systemic comorbidities, such as diabetes and obesity are associated with human benign prostatic hyperplasia (BPH). There is a paucity of in vivo models reflecting specific aspects of BPH pathogenesis. Our aim was to investigate the nonobese diabetic (NOD) mouse as a potential model for subsequent intervention studies.

MATERIALS AND METHODS

We used the NOD mouse, a model of autoimmune inflammation leading to type 1 diabetes to examine the effects of systemic inflammation and diabetes on the prostate. We assessed changes in prostatic histology, infiltrating leukocytes, and gene expression associated with aging and diabetic status.

RESULTS

Both stromal expansion and epithelial hyperplasia were observed in the prostates. Regardless of diabetic status, the degree of prostatic hyperplasia varied. Local inflammation was associated with a more severe prostatic phenotype in both diabetic and nondiabetic mice. Testicular atrophy was noted in diabetic mice, but prostate glands showed persistent focal cell proliferation. In addition, a prostatic intraepithelial neoplasia (PIN)-like phenotype was seen in several diabetic animals with an associated increase in c-Myc and MMP-2 expression. To examine changes in gene and cytokine expression we performed microarray and cytokine array analysis comparing the prostates of diabetic and nondiabetic animals. Microarray analysis revealed several differentially expressed genes including CCL3, CCL12, and TNFS10. Cytokine array analysis revealed increased expression of cytokines and proteases such as LDLR, IL28 A/B, and MMP-2 in diabetic mice.

CONCLUSION

Overall, NOD mice provide a model to examine the effects of hyperglycemia and chronic inflammation on the prostate, demonstrating relevance to some of the mechanisms present underlying BPH and potentially the initiation of prostate cancer.

The Crowded Crosstalk between Cancer Cells and Stromal Microenvironment in Gynecological Malignancies: Biological Pathways and Therapeutic Implication

The tumor microenvironment plays a pillar role in the progression and the distance dissemination of cancer cells in the main malignancies affecting women-epithelial ovarian cancer, endometrial cancer and cervical cancer. Their milieu acquires specific properties thanks to intense crosstalk between stromal and cancer cells, leading to a vicious circle. Fibroblasts, pericytes, lymphocytes and tumor associated-macrophages orchestrate most of the biological pathways. In epithelial ovarian cancer, high rates of activated pericytes determine a poorer prognosis, defining a common signature promoting ovarian cancer proliferation, local invasion and distant spread. Mesenchymal cells also release chemokines and cytokines under hormonal influence, such as estrogens that drive most of the endometrial cancers. Interestingly, the architecture of the cervical cancer milieu is shaped by the synergy of high-risk Human Papilloma Virus oncoproteins and the activity of stromal estrogen receptor α. Lymphocytes represent a shield against cancer cells but some cell subpopulation could lead to immunosuppression, tumor growth and dissemination. Cytotoxic tumor infiltrating lymphocytes can be eluded by over-adapted cancer cells in a scenario of immune-tolerance driven by T-regulatory cells. Therefore, the tumor microenvironment has a high translational potential offering many targets for biological and immunological therapies.

IL-22-Independent Protection from Colitis in the Absence of Nkx2.3 Transcription Factor in Mice

The transcription factor Nkx2.3 regulates the vascular specification of Peyer patches in mice through determining endothelial addressin preference and may function as a susceptibility factor in inflammatory bowel diseases in humans. We wished to analyze the role of Nkx2.3 in colonic solitary intestinal lymphoid tissue composition and in colitis pathogenesis. We studied the colonic solitary intestinal lymphoid tissue of Nkx2.3-deficient mice with immunofluorescence and flow cytometry. Colitis was induced in mice using 2.5% dextran sodium sulfate, and severity was assessed with histology, flow cytometry, and quantitative PCR. We found that the lack of Nkx2.3 impairs maturation of isolated lymphoid follicles and attenuates dextran sodium sulfate-induced colitis independent of endothelial absence of mucosal addressin cell-adhesion molecule-1 (MAdCAM-1), which was also coupled with enhanced colonic epithelial regeneration. Although we observed increased numbers of group 3 innate lymphoid cells and Th17 cells and enhanced transcription of IL-22, Ab-mediated neutralization of IL-22 did not abolish the protection from colitis in Nkx2.3-deficient mice. Nkx2.3-/- hematopoietic cells could not rescue wild-type mice from colitis. Using LacZ-Nkx2.3 reporter mice, we found that Nkx2.3 expression was restricted to VAP-1+ myofibroblast-like pericryptal cells. These results hint at a previously unknown stromal role of Nkx2.3 as driver of colitis and indicate that Nkx2.3+ stromal cells play a role in epithelial cell homeostasis.

Anti-inflammatory cytokines in endometriosis

Although the pathogenesis of endometriosis is not fully understood, it is often considered to be an inflammatory disease. An increasing number of studies suggest that differential expression of anti-inflammatory cytokines (e.g., interleukin-4 and -10, and transforming growth factor-β1) occurs in women with endometriosis, including in serum, peritoneal fluid and ectopic lesions. These anti-inflammatory cytokines also have indispensable roles in the progression of endometriosis, including by promoting survival, growth, invasion, differentiation, angiogenesis, and immune escape of the endometriotic lesions. In this review, we provide an overview of the expression, origin, function and regulation of anti-inflammatory cytokines in endometriosis, with brief discussion and perspectives on their future clinical implications in the diagnosis and therapy of the disease.

Exosomes in the tumor microenvironment as mediators of cancer therapy resistance

Exosomes are small extracellular vesicles that contain genetic material, proteins, and lipids. They function as potent signaling molecules between cancer cells and the surrounding cells that comprise the tumor microenvironment (TME). Exosomes derived from both tumor and stromal cells have been implicated in all stages of cancer progression and play an important role in therapy resistance. Moreover, due to their nature as mediators of cell-cell communication, they are integral to TME-dependent therapy resistance. In this review, we discuss current exosome isolation and profiling techniques and their role in TME interactions and therapy resistance. We also explore emerging clinical applications of both exosomes as biomarkers, direct therapeutic targets, and engineered nanocarriers. In order to fully understand the TME, careful interrogation of exosomes and their cargo is critical. This understanding is a promising avenue for the development of effective clinical applications.

Antifibrotic Therapy Disrupts Stromal Barriers and Modulates the Immune Landscape in Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDA) remains one of the deadliest forms of cancer, in part, because it is largely refractory to current therapies. The failure of most standard therapies in PDA, as well as promising immune therapies, may be largely ascribed to highly unique and protective stromal microenvironments that present significant biophysical barriers to effective drug delivery, that are immunosuppressive, and that can limit the distribution and function of antitumor immune cells. Here, we utilized stromal reengineering to disrupt these barriers and move the stroma toward normalization using a potent antifibrotic agent, halofuginone. In an autochthonous genetically engineered mouse model of PDA, halofuginone disrupted physical barriers to effective drug distribution by decreasing fibroblast activation and reducing key extracellular matrix elements that drive stromal resistance. Concomitantly, halofuginone treatment altered the immune landscape in PDA, with greater immune infiltrate into regions of low hylauronan, which resulted in increased number and distribution of both classically activated inflammatory macrophages and cytotoxic T cells. In concert with a direct effect on carcinoma cells, this led to widespread intratumoral necrosis and reduced tumor volume. These data point to the multifunctional and critical role of the stroma in tumor protection and survival and demonstrate how compromising tumor integrity to move toward a more normal physiologic state through stroma-targeting therapy will likely be an instrumental component in treating PDA. SIGNIFICANCE: This work demonstrates how focused stromal re-engineering approaches to move toward normalization of the stroma disrupt physical barriers to effective drug delivery and promote antitumor immunity.See related commentary by Huang and Brekken, p. 328.

Stroma: the forgotten cells of innate immune memory

All organisms are exposed constantly to a variety of infectious and injurious stimuli. These induce inflammatory responses tailored to the threat posed. While the innate immune system is the front line of response to each stimulant, it has been considered traditionally to lack memory, acting in a generic fashion until the adaptive immune arm can take over. This outmoded simplification of the roles of innate and acquired arms of the immune system has been challenged by evidence of myeloid cells altering their response to subsequent encounters based on earlier exposure. This concept of 'innate immune memory' has been known for nearly a century, and is accepted among myeloid biologists. In recent years other innate immune cells, such as natural killer cells, have been shown to display memory, suggesting that innate immune memory is a trait common to several cell types. During the last 30 years, evidence has slowly accumulated in favour of not only haematopoietic cells, but also stromal cells, being imbued with memory following inflammatory episodes. A recent publication showing this also to be true in epithelial cells suggests innate immune memory to be widespread, if under-appreciated, in non-haematopoietic cells. In this review, we will examine the evidence supporting the existence of innate immune memory in stromal cells. We will also discuss the ramifications of memory in long-lived tissue-resident cells. Finally, we will pose questions we feel to be important in the understanding of these forgotten cells in the field of innate memory.

Autoimmune Th17 Cells Induced Synovial Stromal and Innate Lymphoid Cell Secretion of the Cytokine GM-CSF to Initiate and Augment Autoimmune Arthritis

Despite the importance of Th17 cells in autoimmune diseases, it remains unclear how they control other inflammatory cells in autoimmune tissue damage. Using a model of spontaneous autoimmune arthritis, we showed that arthritogenic Th17 cells stimulated fibroblast-like synoviocytes via interleukin-17 (IL-17) to secrete the cytokine GM-CSF and also expanded synovial-resident innate lymphoid cells (ILCs) in inflamed joints. Activated synovial ILCs, which expressed CD25, IL-33Ra, and TLR9, produced abundant GM-CSF upon stimulation by IL-2, IL-33, or CpG DNA. Loss of GM-CSF production by either ILCs or radio-resistant stromal cells prevented Th17 cell-mediated arthritis. GM-CSF production by Th17 cells augmented chronic inflammation but was dispensable for the initiation of arthritis. We showed that GM-CSF-producing ILCs were present in inflamed joints of rheumatoid arthritis patients. Thus, a cellular cascade of autoimmune Th17 cells, ILCs, and stromal cells, via IL-17 and GM-CSF, mediates chronic joint inflammation and can be a target for therapeutic intervention.

Poly (I:C) and LPS induce distinct immune responses by ovarian stromal fibroblasts

Despite its anatomical location, the ovary is a site of pathogen exposure in the human female reproductive tract (FRT). However, the role of ovarian stromal fibroblasts in immune protection is unclear. We generated a population of ovarian stromal fibroblasts derived from normal human ovaries that expressed the pattern recognition receptors TLR3, TLR4, RIG-I, & MDA5. Poly (I:C) and LPS, respective mimics of viral and bacterial infections, selectively upregulated antiviral gene expression and secretion of chemokines and antimicrobials. Poly (I:C) exclusively stimulated the expression of interferon (IFN) β, IFNλ1, and the IFN-stimulated gene OAS2. Poly (I:C) also significantly increased secretion of elafin, CCL20, and RANTES, but had no effect on SDF-1α. In contrast, LPS had no effect on IFN or ISG expression but significantly increased secretion of RANTES and SDF-1α. Secretions from poly (I:C)-treated fibroblasts had both greater anti-HIV activity and induced higher levels of CD4 + T cell chemotaxis than those from LPS-treated cells. Our studies demonstrate a potential key role for ovarian fibroblasts in innate immune protection against incoming pathogens in the normal ovary.