PD-L1 engagement on T cells promotes self-tolerance and suppression of neighboring macrophages and effector T cells in cancer.

Programmed cell death protein 1 (PD-1) ligation delimits immunogenic responses in T cells. However, the consequences of programmed cell death 1 ligand 1 (PD-L1) ligation in T cells are uncertain. We found that T cell expression of PD-L1 in cancer was regulated by tumor antigen and sterile inflammatory cues. PD-L1+ T cells exerted tumor-promoting tolerance via three distinct mechanisms: (1) binding of PD-L1 induced STAT3-dependent 'back-signaling' in CD4+ T cells, which prevented activation, reduced TH1-polarization and directed TH17-differentiation. PD-L1 signaling also induced an anergic T-bet-IFN-γ- phenotype in CD8+ T cells and was equally suppressive compared to PD-1 signaling; (2) PD-L1+ T cells restrained effector T cells via the canonical PD-L1-PD-1 axis and were sufficient to accelerate tumorigenesis, even in the absence of endogenous PD-L1; (3) PD-L1+ T cells engaged PD-1+ macrophages, inducing an alternative M2-like program, which had crippling effects on adaptive antitumor immunity. Collectively, we demonstrate that PD-L1+ T cells have diverse tolerogenic effects on tumor immunity.

The fungal mycobiome promotes pancreatic oncogenesis via activation of MBL.

Bacterial dysbiosis accompanies carcinogenesis in malignancies such as colon and liver cancer, and has recently been implicated in the pathogenesis of pancreatic ductal adenocarcinoma (PDA)1. However, the mycobiome has not been clearly implicated in tumorigenesis. Here we show that fungi migrate from the gut lumen to the pancreas, and that this is implicated in the pathogenesis of PDA. PDA tumours in humans and mouse models of this cancer displayed an increase in fungi of about 3,000-fold compared to normal pancreatic tissue. The composition of the mycobiome of PDA tumours was distinct from that of the gut or normal pancreas on the basis of alpha- and beta-diversity indices. Specifically, the fungal community that infiltrated PDA tumours was markedly enriched for Malassezia spp. in both mice and humans. Ablation of the mycobiome was protective against tumour growth in slowly progressive and invasive models of PDA, and repopulation with a Malassezia species-but not species in the genera Candida, Saccharomyces or Aspergillus-accelerated oncogenesis. We also discovered that ligation of mannose-binding lectin (MBL), which binds to glycans of the fungal wall to activate the complement cascade, was required for oncogenic progression, whereas deletion of MBL or C3 in the extratumoral compartment-or knockdown of C3aR in tumour cells-were both protective against tumour growth. In addition, reprogramming of the mycobiome did not alter the progression of PDA in Mbl- (also known as Mbl2) or C3-deficient mice. Collectively, our work shows that pathogenic fungi promote PDA by driving the complement cascade through the activation of MBL.

Semilunar valve growth and function 10 years after infant heart transplantation: Predicting long-term outcomes of partial heart transplants.

INTRODUCTION: Partial heart transplants are a new type of pediatric transplant that replace defective heart valves with the parts of matched donor hearts containing the necessary valves. Short-term outcomes of partial heart transplants are excellent, but long-term outcomes are unknown. In order to predict the long-term outcomes of partial heart transplants, we evaluated long-term growth and function of semilunar heart valves transplanted in infancy as part of a heart transplant. METHODS: All children who underwent infant heart transplantation at a single center from 1997 to 2014 were included in this study. Children in whom echocardiograms after heart transplantation and after 10 years were not available for review were excluded. The echocardiograms were reviewed by two authors to analyze semilunar valve annulus diameters, Z-scores, peak valve gradients, and valve regurgitation. Statistical difference was determined using two-tailed, paired sample t-tests with Bonferroni correction for multiple comparisons. RESULTS: Data from 15 patients were analyzed. The aortic valve annulus averaged 1.3 cm (range 0.7-1.8 cm) immediately after transplantation and grew to an average of 1.7 cm (range 1.4-2.3 cm) after 10 years (p < .001). After 10 years, the aortic valve peak gradient avereraged 5.1 mmHg (range 2.1-15.5 mmHg) and none of the valves had more than trivial regurgitation. The pulmonary valve annulus averaged 1.5 cm (range 1.1-2.5 cm) immediately after transplantation and grew to an average of 2.1 cm (range 1.0-2.9 cm) after 10 years (p < .001). After 10 years, the pulmonary valve peak gradient averaged 4.3 mmHg (range 1.1-13.8 mmHg), and 7% of valves had moderate regurgitation. DISCUSSION: Semilunar heart valves transplanted in infancy as part of a heart transplant demonstrate statistically significant growth and excellent function after 10 years. This predicts excellent long-term outcomes of partial heart transplants.

Comparing Survival After Resection, Ablation, and Radiation in Small Intrahepatic Cholangiocarcinoma.

BACKGROUND: Hepatectomy is the cornerstone of curative-intent treatment for intrahepatic cholangiocarcinoma (ICC). However, in patients unable to be resected, data comparing efficacy of alternatives including thermal ablation and radiation therapy (RT) remain limited. Herein, we compared survival between resection and other liver-directed therapies for small ICC within a national cancer registry. PATIENTS AND METHODS: Patients with clinical stage I-III ICC < 3 cm diagnosed 2010-2018 who underwent resection, ablation, or RT were identified in the National Cancer Database. Overall survival (OS) was compared using Kaplan-Meier and multivariable Cox proportional hazards methods. RESULTS: Of 545 patients, 297 (54.5%) underwent resection, 114 (20.9%) ablation, and 134 (24.6%) RT. Median OS was similar between resection and ablation [50.5 months, 95% confidence interval (CI) 37.5-73.9; 39.5 months, 95% CI 28.7-58.4, p = 0.14], both exceeding that of RT (20.9 months, 95% CI 14.1-28.3). RT patients had high rates of stage III disease (10.4% RT vs. 1.8% ablation vs. 11.8% resection, p < 0.001), but the lowest rates of chemotherapy utilization (9.0% RT vs. 15.8% ablation vs. 38.7% resection, p < 0.001). In multivariable analysis, resection and ablation were associated with reduced mortality compared with RT [hazard ratio (HR) 0.44, 95% CI 0.33-0.58 and HR 0.53, 95% CI 0.38-0.75, p < 0.001, respectively]. CONCLUSION: Resection and ablation were associated with improved survival in patients with ICC < 3 cm compared with RT. Acknowledging confounders, anatomic constraints of ablation, limitations of available data, and need for prospective study, these results favor ablation in small ICC where resection is not feasible.

γδ T Cells Promote Steatohepatitis by Orchestrating Innate and Adaptive Immune Programming.

BACKGROUND AND AIMS: The recruitment and activation of inflammatory cells in the liver delineates the transition from hepatic steatosis to steatohepatitis (SH). APPROACH AND RESULTS: We found that in SH, γδT cells are recruited to the liver by C-C chemokine receptor (CCR) 2, CCR5, and nucleotide-binding oligomerization domain-containing protein 2 signaling and are skewed toward an interleukin (IL)-17A+ phenotype in an inducible costimulator (ICOS)/ICOS ligand-dependent manner. γδT cells exhibit a distinct Vγ4+ , PD1+ , Ly6C+ CD44+ phenotype in SH. Moreover, γδT cells up-regulate both CD1d, which is necessary for lipid-based antigens presentation, and the free fatty acid receptor, CD36. γδT cells are stimulated to express IL-17A by palmitic acid and CD1d ligation. Deletion, depletion, and targeted interruption of γδT cell recruitment protects against diet-induced SH and accelerates disease resolution. CONCLUSIONS: We demonstrate that hepatic γδT cells exacerbate SH, independent of IL-17 expression, by mitigating conventional CD4+ T-cell expansion and modulating their inflammatory program by CD1d-dependent vascular endothelial growth factor expression.

EMX2 gene expression predicts liver metastasis and survival in colorectal cancer.

BACKGROUND: The Empty Spiracles Homeobox (EMX-) 2 gene has been associated with regulation of growth and differentiation in neuronal development. While recent studies provide evidence that EMX2 regulates tumorigenesis of various solid tumors, its role in colorectal cancer remains unknown. We aimed to assess the prognostic significance of EMX2 expression in stage III colorectal adenocarcinoma. METHODS: Expression levels of EMX2 in human colorectal cancer and adjacent mucosa were assessed by qRT-PCR technology, and results were correlated with clinical and survival data. siRNA-mediated knockdown and adenoviral delivery-mediated overexpression of EMX2 were performed in order to investigate its effects on the migration of colorectal cancer cells in vitro. RESULTS: Compared to corresponding healthy mucosa, colorectal tumor samples had decreased EMX2 expression levels. Furthermore, EMX2 down-regulation in colorectal cancer tissue was associated with distant metastasis (M1) and impaired overall patient survival. In vitro knockdown of EMX2 resulted in increased tumor cell migration. Conversely, overexpression of EMX2 led to an inhibition of tumor cell migration. CONCLUSIONS: EMX2 is frequently down-regulated in human colorectal cancer, and down-regulation of EMX2 is a prognostic marker for disease-free and overall survival. EMX2 might thus represent a promising therapeutic target in colorectal cancer.

Survival after partial heart transplantation in a piglet model.

Partial heart transplantation (PHT) is a novel surgical approach that involves transplantation of only the part of the heart containing a valve. The rationale for this approach is to deliver growing heart valve implants that reduce the need for future re-operations in children. However, prior to clinical application of this approach, it was important to assess it in a preclinical model. To investigate PHT short-term outcomes and safety, we performed PHT in a piglet model. Yorkshire piglets (n = 14) were used for PHT of the pulmonary valve. Donor and recipient pairs were matched based on blood types. The piglets underwent PHT at an average age of 44 days (range 34-53). Post-operatively, the piglets were monitored for a period of two months. Of the 7 recipient piglets, one mortality occurred secondary to anesthesia complications while undergoing a routine echocardiogram on post-operative day 19. All piglets had appropriate weight gain and laboratory findings throughout the post-operative period indicating a general state of good health and rehabilitation after undergoing PHT. We conclude that PHT has good short-term survival in the swine model. PHT appears to be safe for clinical application.

Surgical Protocol for Partial Heart Transplantation in Growing Piglets.

Partial heart transplantation is a new approach to deliver growing heart valve implants. Partial heart transplants differ from heart transplants because only the part of the heart containing the necessary heart valve is transplanted. This allows partial heart transplants to grow, similar to the valves in heart transplants. However, the transplant biology of partial heart transplantation remains unexplored. This is a critical barrier to progress of the field. Without knowledge about the specific transplant biology of partial heart transplantation, children with partial heart transplants are empirically treated like children with heart transplants because the valves in heart transplants are known to grow. In order to progress the field, an animal model for partial heart transplantation is necessary. Here, we contribute our surgical protocol for partial heart transplantation in growing piglets. All aspects of partial heart transplantation, including the donor procedure, the recipient procedure, and recipient perioperative care are described in detail. There are important nuances in the conduct of virtually all aspects of open heart surgery that differs in piglets from humans. Our surgical protocol, which is based on our experience with 34 piglets, will allow other investigators to leverage our experience to seek fundamental knowledge about the nature of partial heart transplants. This is significant because the partial heart transplant model in piglets is complex and very resource intensive.

Colorectal Cancer Liver Metastases: Multimodal Therapy.

Despite a steady decline in incidence and mortality rates, colorectal cancer (CRC) remains the second most common cancer diagnosis in women and the third most common in men worldwide. Notably, the liver is recognized as the most common site of CRC metastasis, and metastases to the liver remain the primary driver of disease-specific mortality for patients with CRC. Although hepatic resection is the backbone of curative-intent treatment, management of CRLM has become increasingly multimodal during the last decade and includes the use of downstaging chemotherapy, ablation techniques, and locoregional therapy, each of which are reviewed herein.

BTLA+CD200+ B cells dictate the divergent immune landscape and immunotherapeutic resistance in metastatic vs. primary pancreatic cancer.

Response to cancer immunotherapy in primary versus metastatic disease has not been well-studied. We found primary pancreatic ductal adenocarcinoma (PDA) is responsive to diverse immunotherapies whereas liver metastases are resistant. We discovered divergent immune landscapes in each compartment. Compared to primary tumor, liver metastases in both mice and humans are infiltrated by highly anergic T cells and MHCIIloIL10+ macrophages that are unable to present tumor-antigen. Moreover, a distinctive population of CD24+CD44-CD40- B cells dominate liver metastases. These B cells are recruited to the metastatic milieu by Muc1hiIL18hi tumor cells, which are enriched >10-fold in liver metastases. Recruited B cells drive macrophage-mediated adaptive immune-tolerance via CD200 and BTLA. Depleting B cells or targeting CD200/BTLA enhanced macrophage and T-cell immunogenicity and enabled immunotherapeutic efficacy of liver metastases. Our data detail the mechanistic underpinnings for compartment-specific immunotherapy-responsiveness and suggest that primary PDA models are poor surrogates for evaluating immunity in advanced disease.

Intrahepatic microbes govern liver immunity by programming NKT cells.

The gut microbiome shapes local and systemic immunity. The liver is presumed to be a protected sterile site. As such, a hepatic microbiome has not been examined. Here, we showed a liver microbiome in mice and humans that is distinct from that of the gut and is enriched in Proteobacteria. It undergoes dynamic alterations with age and is influenced by the environment and host physiology. Fecal microbial transfer experiments revealed that the liver microbiome is populated from the gut in a highly selective manner. Hepatic immunity is dependent on the microbiome, specifically the bacteroidetes species. Targeting bacteroidetes with oral antibiotics reduced hepatic immune cells by approximately 90%, prevented antigen-presenting cell (APC) maturation, and mitigated adaptive immunity. Mechanistically, our findings are consistent with presentation of bacteroidetes-derived glycosphingolipids to NKT cells promoting CCL5 signaling, which drives hepatic leukocyte expansion and activation, among other possible host-microbe interactions. Collectively, we reveal a microbial/glycosphingolipid/NKT/CCL5 axis that underlies hepatic immunity.

Regulatory T Cells Keep Pancreatic Cancer at Bay.

Although CD4+ FOXP3+ T regulatory (Treg) cells are well-known mediators of immunologic tolerance, their influences in the tumor microenviroment are incompletely understood. Writing in this issue of Cancer Discovery, Zhang and colleagues demonstrate that in pancreatic cancer, Treg cells promote the differentiation of tumor-restraining myofibroblastic cancer-associated fibroblasts, challenging the existing notion that Treg cells enable tumor progression.See related article by Zhang et al., p. 422.

Targeting Piezo1 unleashes innate immunity against cancer and infectious disease.

Piezo1 is a mechanosensitive ion channel that has gained recognition for its role in regulating diverse physiological processes. However, the influence of Piezo1 in inflammatory disease, including infection and tumor immunity, is not well studied. We postulated that Piezo1 links physical forces to immune regulation in myeloid cells. We found signal transduction via Piezo1 in myeloid cells and established this channel as the primary sensor of mechanical stress in these cells. Global inhibition of Piezo1 with a peptide inhibitor was protective against both cancer and septic shock and resulted in a diminution in suppressive myeloid cells. Moreover, deletion of Piezo1 in myeloid cells protected against cancer and increased survival in polymicrobial sepsis. Mechanistically, we show that mechanical stimulation promotes Piezo1-dependent myeloid cell expansion by suppressing the retinoblastoma gene Rb1 We further show that Piezo1-mediated silencing of Rb1 is regulated via up-regulation of histone deacetylase 2. Collectively, our work uncovers Piezo1 as a targetable immune checkpoint that drives immunosuppressive myelopoiesis in cancer and infectious disease.

Targeting SYK signaling in myeloid cells protects against liver fibrosis and hepatocarcinogenesis.

Liver fibrosis and fibrosis-associated hepatocarcinogenesis are driven by chronic inflammation and are leading causes of morbidity and death worldwide. SYK signaling regulates critical processes in innate and adaptive immunity, as well as parenchymal cells. We discovered high SYK expression in the parenchymal hepatocyte, hepatic stellate cell (HSC), and the inflammatory compartments in the fibrotic liver. We postulated that targeting SYK would mitigate hepatic fibrosis and oncogenic progression. We found that inhibition of SYK with the selective small molecule inhibitors Piceatannol and PRT062607 markedly protected against toxin-induced hepatic fibrosis, associated hepatocellular injury and intra-hepatic inflammation, and hepatocarcinogenesis. SYK inhibition resulted in increased intra-tumoral expression of the p16 and p53 but decreased expression of Bcl-xL and SMAD4. Further, hepatic expression of genes regulating angiogenesis, apoptosis, cell cycle regulation, and cellular senescence were affected by targeting SYK. We found that SYK inhibition mitigated both HSC trans-differentiation and acquisition of an inflammatory phenotype in T cells, B cells, and myeloid cells. However, in vivo experiments employing selective targeted deletion of SYK indicated that only SYK deletion in the myeloid compartment was sufficient to confer protection against fibrogenic progression. Targeting SYK promoted myeloid cell differentiation into hepato-protective TNFαlow CD206hi phenotype downregulating mTOR, IL-8 signaling and oxidative phosphorylation. Collectively, these data suggest that SYK is an attractive target for experimental therapeutics in treating hepatic fibrosis and oncogenesis.

Specialized dendritic cells induce tumor-promoting IL-10+IL-17+ FoxP3neg regulatory CD4+ T cells in pancreatic carcinoma.

The drivers and the specification of CD4+ T cell differentiation in the tumor microenvironment and their contributions to tumor immunity or tolerance are incompletely understood. Using models of pancreatic ductal adenocarcinoma (PDA), we show that a distinct subset of tumor-infiltrating dendritic cells (DC) promotes PDA growth by directing a unique TH-program. Specifically, CD11b+CD103- DC predominate in PDA, express high IL-23 and TGF-ß, and induce FoxP3neg tumor-promoting IL-10+IL-17+IFNγ+ regulatory CD4+ T cells. The balance between this distinctive TH program and canonical FoxP3+ TREGS is unaffected by pattern recognition receptor ligation and is modulated by DC expression of retinoic acid. This TH-signature is mimicked in human PDA where it is associated with immune-tolerance and diminished patient survival. Our data suggest that CD11b+CD103- DC promote CD4+ T cell tolerance in PDA which may underscore its resistance to immunotherapy.

Innate αß T Cells Mediate Antitumor Immunity by Orchestrating Immunogenic Macrophage Programming.

Unconventional T-lymphocyte populations are emerging as important regulators of tumor immunity. Despite this, the role of TCRαß+CD4-CD8-NK1.1- innate αß T cells (iαßT) in pancreatic ductal adenocarcinoma (PDA) has not been explored. We found that iαßTs represent ∼10% of T lymphocytes infiltrating PDA in mice and humans. Intratumoral iαßTs express a distinct T-cell receptor repertoire and profoundly immunogenic phenotype compared with their peripheral counterparts and conventional lymphocytes. iαßTs comprised ∼75% of the total intratumoral IL17+ cells. Moreover, iαßT-cell adoptive transfer is protective in both murine models of PDA and human organotypic systems. We show that iαßT cells induce a CCR5-dependent immunogenic macrophage reprogramming, thereby enabling marked CD4+ and CD8+ T-cell expansion/activation and tumor protection. Collectively, iαßTs govern fundamental intratumoral cross-talk between innate and adaptive immune populations and are attractive therapeutic targets. SIGNIFICANCE: We found that iαßTs are a profoundly activated T-cell subset in PDA that slow tumor growth in murine and human models of disease. iαßTs induce a CCR5-dependent immunogenic tumor-associated macrophage program, T-cell activation and expansion, and should be considered as novel targets for immunotherapy.See related commentary by Banerjee et al., p. 1164.This article is highlighted in the In This Issue feature, p. 1143.

Macrophages in Nonalcoholic Steatohepatitis: Friend or Foe?

Nonalcoholic steatohepatitis (NASH) is a subtype of nonalcoholic fatty liver disease that is characterised by steatosis, chronic inflammation, and hepatocellular injury with or without fibrosis. The role and activation of macrophages in the pathogenesis of NASH is complex and is being studied for possible therapeutic options to help the millions of people diagnosed with the disease. The purpose of this review is to discuss the pathogenesis of NASH through the activation and role of Kupffer cells and other macrophages in causing inflammation and progression of NASH. Furthermore, this review aims to outline some of the current therapeutic options targeting the pathogenesis of NASH.