T cells and monocyte-derived myeloid cells mediate immunotherapy-related hepatitis in a mouse model

Establishment of an animal model of immune-related adverse events induced by immune checkpoint inhibitors

OBJECTIVE

Immunotherapy, specifically immune checkpoint inhibitors (ICIs), has revolutionized cancer treatment. However, it can also cause immune-related adverse events (irAEs). This study aimed to develop a clinically practical animal model of irAEs using BALB/c mice.

METHODS

Subcutaneous tumors of mouse breast cancer 4T1 cells were generated in inbred BALB/c mice. The mice were treated with programmed death-1 (PD-1) and cytotoxic t-lymphocyte antigen 4 (CTLA-4) inhibitors once every 3 days for five consecutive administration cycles. Changes in tumor volume and body weight were recorded. Lung computed tomography (CT) scans were conducted. The liver, lungs, heart, and colon tissues of the mice were stained with hematoxylin-eosin (H&E) staining to observe inflammatory infiltration and were scored. Serum samples were collected, and enzyme-linked immunosorbent assay (ELISA) was used to detect the levels of ferritin, glutamic-pyruvic transaminase (ALT), tumor necrosis factor-α (TNF-α), interferon-gamma (IFN-γ), and interleukin-6 (IL-6). Mouse liver and lung cell suspensions were prepared, and changes in macrophages, T cells, myeloid-derived suppressor cells (MDSCs), and regulatory (Treg) cells were detected by flow cytometry.

RESULTS

Mice treated with PD-1 and CTLA-4 inhibitors showed significant reductions in tumor volume and body weight. The tissue inflammatory scores in the experimental group were significantly higher than those in the control group. Lung CT scans of mice in the experimental group showed obvious inflammatory spots. Serum levels of ferritin, IL-6, TNF-α, IFN-γ, and ALT were significantly elevated in the experimental group. Flow cytometry analysis revealed a substantial increase in CD3+T cells, Treg cells, and macrophages in the liver and lung tissues of mice in the experimental group compared with the control group, and the change trend of MDSCs was opposite.

CONCLUSIONS

The irAE-related animal model was successfully established in BALB/c mice using a combination of PD-1 and CTLA-4 inhibitors through multiple administrations with clinical translational value and practical. This model offers valuable insights into irAE mechanisms for further investigation.

Single-cell RNA sequencing reveals the altered innate immunity in immune checkpoint inhibitor-related myocarditis

Myocarditis has emerged as a rare but lethal immune checkpoint inhibitor (ICI)-associated toxicity. However, the exact mechanism and the specific therapeutic targets remain underexplored. In this study, we aim to characterise the transcriptomic profiles based on single-cell RNA sequencing from ICI-related myocarditis. Peripheral blood mononuclear cell (PBMC) samples were collected from four groups for single-cell RNA sequencing: (1) patients with newly diagnosed lung squamous cell carcinoma before treatment (Control Group); (2) patients with lung squamous cell carcinoma with PD-1 inhibitor therapy who did not develop myocarditis (PD-1 Group); (3) patients during fulminant ICI-related myocarditis onset (Myocarditis Group); and (4) Patients with fulminant ICI-related myocarditis during disease remission (Recovery Group). Subcluster determination, functional analysis, single-cell trajectory and cell-cell interaction analysis were performed after scRNA-seq. Bulk-RNA sequencing was performed for further validation. Our results revealed the diversity of cellular populations in ICI-related myocarditis, marked by their distinct transcriptional profiles and biological functions. Monocytes, NKs as well as B cells contribute to the regulation of innate immunity and inflammation in ICI-related myocarditis. With integrated analysis of scRNA-seq and bulk sequencing, we identified S100A protein family as a potential serum marker for ICI-related myocarditis. Our study has created a cell atlas of PBMC during ICI-related myocarditis, which would shed light on the pathophysiological mechanism and potential therapeutic targets of ICI-related myocarditis in continuous exploration.

Hepatocyte-derived FGL1 accelerates liver metastasis and tumor growth by inhibiting CD8+ T and NK cells

Fibrinogen-like protein 1 (FGL1) contributes to the proliferation and metabolism of hepatocytes; however, as a major ligand of the immune checkpoint, its role in the liver regional immune microenvironment is poorly understood. Hepatocytes specifically and highly expressed FGL1 under normal physiological conditions. Increases in hepatic CD8+ T and NK cell numbers and functions were found in Fgl1-deficient (Fgl1-/-) mice, but not in the spleen or lymph node, similar to findings in anti-FGL1 mAb-treated wild-type mice. Furthermore, Fgl1 deficiency or anti-FGL1 mAb blockade restrained liver metastasis and slowed the growth of orthotopic tumors, with significantly prolonged survival of tumor-bearing mice. Tumor-infiltrating hepatic CD8+ T and NK cells upregulated the expression of lymphocyte activation gene-3 (LAG-3) and exhibited stronger antitumor activities after anti-FGL1 treatment. The antitumor efficacy of FGL1 blockade depended on cytotoxic T lymphocytes and NK cells, demonstrated by using a cell-deficient mouse model and cell transfer in vivo. In vitro, FGL1 directly inhibited hepatic T and NK cells related to the receptor LAG-3. In conclusion, hepatocyte-derived FGL1 played critical immunoregulatory roles in the liver and contributed to liver metastasis and tumor growth by inhibiting CD8+ T and NK cell functions via the receptor LAG-3, providing a new strategy for liver cancer immunotherapy.

Activation of CD14+ Monocytes via the IFN-γ Signaling Pathway Is Associated with Immune-Related Adverse Events in Hepatocellular Carcinoma Patients Receiving PD-1 Inhibition Combination Therapy

(1) Background: Immune-related adverse events (irAEs) are a series of unique organ-specific inflammatory toxicities observed in patients with hepatocellular carcinoma (HCC) undergoing PD-1 inhibition combination therapy. The specific underlying mechanisms remain unclear. (2) Methods: We recruited 71 patients with HCC undergoing PD-1 inhibition combination therapy. These patients were then divided into two groups based on irAE occurrence: 34 had irAEs and 37 did not. Using Olink proteomics, we analyzed the aberrant inflammation-related proteins (IRPs) in these patient groups. For single-cell RNA sequencing (scRNA-seq) analysis, we collected peripheral blood mononuclear cells (PBMCs) from two representative patients at the pretreatment, irAE occurrence, and resolution stages. (3) Results: Our study revealed distinct plasma protein signatures in HCC patients experiencing irAEs after PD-1 inhibition combination therapy. We clarified the relationship between monocyte activation and irAEs, identified a strongly associated CD14-MC-CCL3 monocyte subset, and explored the role of the IFN-γ signaling pathway in monocyte activation during irAEs. (4) Conclusions: The activation of monocytes induced by the IFN-γ signaling pathway is an important mechanism underlying the occurrence of irAEs in HCC patients receiving PD-1 inhibition combination therapy.

Therapeutic inhibition of monocyte recruitment prevents checkpoint inhibitor-induced hepatitis

BACKGROUND

Checkpoint inhibitor-induced hepatitis (CPI-hepatitis) is an emerging problem with the widening use of CPIs in cancer immunotherapy. Here, we developed a mouse model to characterize the mechanism of CPI-hepatitis and to therapeutically target key pathways driving this pathology.

METHODS

C57BL/6 wild-type (WT) mice were dosed with toll-like receptor (TLR)9 agonist (TLR9-L) for hepatic priming combined with anti-cytotoxic T lymphocyte antigen-4 (CTLA-4) plus anti-programmed cell death 1 (PD-1) ("CPI") or phosphate buffered saline (PBS) control for up to 7 days. Flow cytometry, histology/immunofluorescence and messenger RNA sequencing were used to characterize liver myeloid/lymphoid subsets and inflammation. Hepatocyte damage was assessed by plasma alanine transaminase (ALT) and cytokeratin-18 (CK-18) measurements. In vivo investigations of CPI-hepatitis were carried out in Rag2-/- and Ccr2rfp/rfp transgenic mice, as well as following anti-CD4, anti-CD8 or cenicriviroc (CVC; CCR2/CCR5 antagonist) treatment.

RESULTS

Co-administration of combination CPIs with TLR9-L induced liver pathology closely resembling human disease, with increased infiltration and clustering of granzyme B+perforin+CD8+ T cells and CCR2+ monocytes, 7 days post treatment. This was accompanied by apoptotic hepatocytes surrounding these clusters and elevated ALT and CK-18 plasma levels. Liver RNA sequencing identified key signaling pathways (JAK-STAT, NF-ΚB) and cytokine/chemokine networks (Ifnγ, Cxcl9, Ccl2/Ccr2) as drivers of CPI-hepatitis. Using this model, we show that CD8+ T cells mediate hepatocyte damage in experimental CPI-hepatitis. However, their liver recruitment, clustering, and cytotoxic activity is dependent on the presence of CCR2+ monocytes. The absence of hepatic monocyte recruitment in Ccr2rfp/rfp mice and CCR2 inhibition by CVC treatment in WT mice was able to prevent the development and reverse established experimental CPI-hepatitis.

CONCLUSION

This newly established mouse model provides a platform for in vivo mechanistic studies of CPI-hepatitis. Using this model, we demonstrate the central role of liver infiltrating CCR2+ monocyte interaction with tissue-destructive CD8+ T cells in the pathogenesis of CPI-hepatitis and highlight CCR2 inhibition as a novel therapeutic target.

Single-cell profiling identifies IL1Bhi macrophages associated with inflammation in PD-1 inhibitor-induced inflammatory arthritis

Inflammatory arthritis (IA) is a common rheumatic adverse event following immune checkpoint inhibitors treatment. The clinical disparities between IA and rheumatoid arthritis (RA) imply disease heterogeneity and distinct mechanisms, which remain elusive. Here, we profile CD45+ cells from the peripheral blood or synovial fluid (SF) of patients with PD-1-induced IA (PD-1-IA) or RA using single-cell RNA sequencing. We report the predominant expansion of IL1Bhi myeloid cells with enhanced NLRP3 inflammasome activity, in both the SF and peripheral blood of PD-1-IA, but not RA. IL1Bhi macrophages in the SF of PD-1-IA shared similar inflammatory signatures and might originate from peripheral IL1Bhi monocytes. Exhausted CD8+ T cells (Texs) significantly accumulated in the SF of patients with PD-1-IA. IL1Bhi myeloid cells communicated with CD8+ Texs possibly via the CCR1-CCL5/CCL3 and CXCL10-CXCR3 axes. Collectively, these results demonstrate different cellular and molecular pathways in PD-1-IA and RA and highlight IL1Bhi macrophages as a possible therapeutic target in PD-1-IA.

Innate and adaptive immune cell interaction drives inflammasome activation and hepatocyte apoptosis in murine liver injury from immune checkpoint inhibitors

Immune checkpoints (CTLA4 & PD-1) are inhibitory pathways that block aberrant immune activity and maintain self-tolerance. Tumors co-opt these checkpoints to avoid immune destruction. Immune checkpoint inhibitors (ICIs) activate immune cells and restore their tumoricidal potential, making them highly efficacious cancer therapies. However, immunotolerant organs such as the liver depend on these tolerogenic mechanisms, and their disruption with ICI use can trigger the unintended side effect of hepatotoxicity termed immune-mediated liver injury from ICIs (ILICI). Learning how to uncouple ILICI from ICI anti-tumor activity is of paramount clinical importance. We developed a murine model to recapitulate human ILICI using CTLA4+/- mice treated with either combined anti-CTLA4 + anti-PDL1 or IgG1 + IgG2. We tested two forms of antisense oligonucleotides to knockdown caspase-3 in a total liver (parenchymal and non-parenchymal cells) or in a hepatocyte-specific manner. We also employed imaging mass cytometry (IMC), a powerful multiplex modality for immunophenotyping and cell interaction analysis in our model. ICI-treated mice had significant evidence of liver injury. We detected cleaved caspase-3 (cC3), indicating apoptosis was occurring, as well as Nod-like receptor protein 3 (NLRP3) inflammasome activation, but no necroptosis. Total liver knockdown of caspase-3 worsened liver injury, and induced further inflammasome activation, and Gasdermin-D-mediated pyroptosis. Hepatocyte-specific knockdown of caspase-3 reduced liver injury and NLRP3 inflammasome activation. IMC-generated single-cell data for 77,692 cells was used to identify 22 unique phenotypic clusters. Spatial analysis revealed that cC3+ hepatocytes had significantly closer interactions with macrophages, Kupffer cells, and NLRP3hi myeloid cells than other cell types. We also observed zones of three-way interaction between cC3+ hepatocytes, CD8 + T-cells, and macrophages. Our work is the first to identify hepatocyte apoptosis and NLRP3 inflammasome activation as drivers of ILICI. Furthermore, we report that the interplay between adaptive and innate immune cells is critical to hepatocyte apoptosis and ILICI.

Immune Checkpoint Inhibitor-Induced Liver Injury

In recent years cancer treatment has been revolutionized by the development and wide application of checkpoint inhibitor (CPI) drugs, which are a form of immunotherapy. CPI treatment is associated with immune-related adverse events, off-target tissue destructive inflammatory complications, which may affect a range of organs, with liver inflammation (hepatitis) being one of the more commonly noted events. This is a novel form of drug-induced liver injury and a rapidly evolving field, as our understanding of both the basic immunopathology of CPI hepatitis (CPI-H) and optimal clinical management, races to catch up with the increasing application of this form of immunotherapy in clinical practice. In this review, we summarize current evidence and understanding of CPI-H, from fundamental immunology to practical patient management.

Stocking the toolbox-Using preclinical models to understand the development and treatment of immune checkpoint inhibitor-induced immune-related adverse events

Cancer patients treated with immune checkpoint inhibitors (ICIs) are susceptible to a broad and variable array of immune-related adverse events (irAEs). With increasing clinical use of ICIs, defining the mechanism for irAE development is more critical than ever. However, it currently remains challenging to predict when these irAEs occur and which organ may be affected, and for many of the more severe irAEs, inaccessibility to the tissue site hampers mechanistic insight. This lack of understanding of irAE development in the clinical setting emphasizes the need for greater use of preclinical models that allow for improved prediction of biomarkers for ICI-initiated irAEs or that validate treatment options that inhibit irAEs without hampering the anti-tumor immune response. Here, we discuss the utility of preclinical models, ranging from exploring databases to in vivo animal models, focusing on where they are most useful and where they could be improved.

Liver in infections: a single-cell and spatial transcriptomics perspective

The liver is an immune organ that plays a vital role in the detection, capture, and clearance of pathogens and foreign antigens that invade the human body. During acute and chronic infections, the liver transforms from a tolerant to an active immune state. The defence mechanism of the liver mainly depends on a complicated network of intrahepatic and translocated immune cells and non-immune cells. Therefore, a comprehensive liver cell atlas in both healthy and diseased states is needed for new therapeutic target development and disease intervention improvement. With the development of high-throughput single-cell technology, we can now decipher heterogeneity, differentiation, and intercellular communication at the single-cell level in sophisticated organs and complicated diseases. In this concise review, we aimed to summarise the advancement of emerging high-throughput single-cell technologies and re-define our understanding of liver function towards infections, including hepatitis B virus, hepatitis C virus, Plasmodium, schistosomiasis, endotoxemia, and corona virus disease 2019 (COVID-19). We also unravel previously unknown pathogenic pathways and disease mechanisms for the development of new therapeutic targets. As high-throughput single-cell technologies mature, their integration into spatial transcriptomics, multiomics, and clinical data analysis will aid in patient stratification and in developing effective treatment plans for patients with or without liver injury due to infectious diseases.

Applications of single-cell RNA sequencing in drug discovery and development

Single-cell technologies, particularly single-cell RNA sequencing (scRNA-seq) methods, together with associated computational tools and the growing availability of public data resources, are transforming drug discovery and development. New opportunities are emerging in target identification owing to improved disease understanding through cell subtyping, and highly multiplexed functional genomics screens incorporating scRNA-seq are enhancing target credentialling and prioritization. ScRNA-seq is also aiding the selection of relevant preclinical disease models and providing new insights into drug mechanisms of action. In clinical development, scRNA-seq can inform decision-making via improved biomarker identification for patient stratification and more precise monitoring of drug response and disease progression. Here, we illustrate how scRNA-seq methods are being applied in key steps in drug discovery and development, and discuss ongoing challenges for their implementation in the pharmaceutical industry.

Metastatic lymph node targeted CTLA4 blockade: a potent intervention for local and distant metastases with minimal ICI-induced pneumonia

BACKGROUND

Immune checkpoint blockade (ICB) elicits a strong and durable therapeutic response, but its application is limited by disparate responses and its associated immune-related adverse events (irAEs). Previously, in a murine model of lymph node (LN) metastasis, we showed that intranodal administration of chemotherapeutic agents using a lymphatic drug delivery system (LDDS) elicits stronger therapeutic responses in comparison to systemic drug delivery approaches, while minimizing systemic toxicity, due to its improved pharmacokinetic profile at the intended site. Importantly, the LN is a reservoir of immunotherapeutic targets. We therefore hypothesized that metastatic LN-targeted ICB can amplify anti-tumor response and uncouple it from ICB-induced irAEs.

METHODS

To test our hypothesis, models of LN and distant metastases were established with luciferase expressing LM8 cells in MXH10/Mo-lpr/lpr mice, a recombinant inbred strain of mice capable of recapitulating ICB-induced interstitial pneumonia. This model was used to interrogate ICB-associated therapeutic response and immune related adverse events (irAEs) by in vivo imaging, high-frequency ultrasound imaging and histopathology. qPCR and flowcytometry were utilized to uncover the mediators of anti-tumor immunity.

RESULTS

Tumor-bearing LN (tbLN)-directed CTLA4 blockade generated robust anti-tumor response against local and systemic metastases, thereby improving survival. The anti-tumor effects were accompanied by an upregulation of effector CD8T cells in the tumor-microenvironment and periphery. In comparison, non-specific CTLA4 blockade was found to elicit weaker anti-tumor effect and exacerbated ICI-induced irAEs, especially interstitial pneumonia. Together these data highlight the importance of tbLN-targeted checkpoint blockade for efficacious response.

CONCLUSIONS

Intranodal delivery of immune checkpoint inhibitors to metastatic LN can potentiate therapeutic response while minimizing irAEs stemming from systemic lowering of immune activation threshold.

Case Report: The application of associating liver partition and portal vein ligation for staged hepatectomy in patients with hepatitis b virus-related hepatocellular carcinoma after undergoing treatment with an immune checkpoint inhibitor: a report of two cases

Hepatocellular carcinoma (HCC) is often diagnosed at an unresectable stage without opportunities for curative therapy. Future liver remnant (FLR) insufficiency limits the range of patients who can undergo radical resection. Associating liver partition and portal vein ligation for staged hepatectomy (ALPPS) can ultimately achieve short-term hypertrophy of the FLR in patients with viral hepatitis-related fibrosis/cirrhosis and R0 resection. However, the influence of immune checkpoint inhibitors (ICIs) on liver regeneration remains unknown. We report two patients diagnosed with Barcelona Clinic Liver Cancer (BCLC)-B stage hepatitis B virus (HBV)-related HCC who underwent pioneering ALPPS after immunotherapy without posthepatectomy liver failure (PHLF). ALPPS has been shown to be safe and feasible in patients with HCC who underwent immunotherapy previously for the first time and might provide an alternative salvage option for future conversion therapy of HCC.

Artificial Intelligence-Assisted Transcriptomic Analysis to Advance Cancer Immunotherapy

The emergence of immunotherapy has dramatically changed the cancer treatment paradigm and generated tremendous promise in precision medicine. However, cancer immunotherapy is greatly limited by its low response rates and immune-related adverse events. Transcriptomics technology is a promising tool for deciphering the molecular underpinnings of immunotherapy response and therapeutic toxicity. In particular, applying single-cell RNA-seq (scRNA-seq) has deepened our understanding of tumor heterogeneity and the microenvironment, providing powerful help for developing new immunotherapy strategies. Artificial intelligence (AI) technology in transcriptome analysis meets the need for efficient handling and robust results. Specifically, it further extends the application scope of transcriptomic technologies in cancer research. AI-assisted transcriptomic analysis has performed well in exploring the underlying mechanisms of drug resistance and immunotherapy toxicity and predicting therapeutic response, with profound significance in cancer treatment. In this review, we summarized emerging AI-assisted transcriptomic technologies. We then highlighted new insights into cancer immunotherapy based on AI-assisted transcriptomic analysis, focusing on tumor heterogeneity, the tumor microenvironment, immune-related adverse event pathogenesis, drug resistance, and new target discovery. This review summarizes solid evidence for immunotherapy research, which might help the cancer research community overcome the challenges faced by immunotherapy.

Innate immunity and early liver inflammation

The innate system constitutes a first-line defence mechanism against pathogens. 80% of the blood supply entering the human liver arrives from the splanchnic circulation through the portal vein, so it is constantly exposed to immunologically active substances and pathogens from the gastrointestinal tract. Rapid neutralization of pathogens and toxins is an essential function of the liver, but so too is avoidance of harmful and unnecessary immune reactions. This delicate balance of reactivity and tolerance is orchestrated by a diverse repertoire of hepatic immune cells. In particular, the human liver is enriched in many innate immune cell subsets, including Kupffer cells (KCs), innate lymphoid cells (ILCs) like Natural Killer (NK) cells and ILC-like unconventional T cells - namely Natural Killer T cells (NKT), γδ T cells and Mucosal-associated Invariant T cells (MAIT). These cells reside in the liver in a memory-effector state, so they respond quickly to trigger appropriate responses. The contribution of aberrant innate immunity to inflammatory liver diseases is now being better understood. In particular, we are beginning to understand how specific innate immune subsets trigger chronic liver inflammation, which ultimately results in hepatic fibrosis. In this review, we consider the roles of specific innate immune cell subsets in early inflammation in human liver disease.

Development of hepatitis triggered by SARS-CoV-2 vaccination in patient with cancer during immunotherapy: a case report

Patients with cancer have a higher risk of severe COVID-19, and expert consensus advocates for COVID-19 vaccination in this population. Some cases of autoimmune hepatitis have been described after the administration of COVID-19 vaccine in the people in apparently good health. Immune checkpoint inhibitors (ICIs) are responsible for a wide spectrum of immune-related adverse events (irAEs). This article reports a case of hepatitis and colitis in a 52-year-old woman who was undergoing immunotherapy and was HBV positive 10 days after receiving the first Pfizer-BioNTech COVID-19 vaccine dose. Because both ICIs and the COVID-19 vaccines stimulate the immune response, the authors hypothesize that these vaccines may increase the incidence of irAEs during ICI treatment. There is a complex interplay between the immune-mediated reaction triggered by the vaccination and PD-L1 co-administration.

Risk factors and predictors of immune-related adverse events: implications for patients with non-small cell lung cancer

INTRODUCTION

Immune checkpoint inhibitors (ICI) are now utilized as a standard of care treatment for multiple cancers, including in both the metastatic setting as well as in earlier stages of disease. The identification of unique immune-related adverse events (irAE) that occur during ICI treatment has led to intense research to identify potential risk factors and biomarkers that may assist in clinical decision making. Although initial studies in ICI were primarily in advanced stage disease, the use of ICI in earlier stages of disease as adjuvant therapies requires a better understanding of patient risk stratification to mitigate or prevent serious irAE.

AREAS COVERED

In this review, we set out to describe the current state of research regarding potential risk factors for irAE in patients with non-small cell lung cancer, as well as explore the barriers to understanding irAE. We review data from irAE that occur in large phase 3 trials and prospective studies focusing on irAE, as well as the many retrospective studies that currently form the bulk of our understanding of irAE.

The Role of Myeloid Cells in Hepatotoxicity Related to Cancer Immunotherapy

Drug-related hepatotoxicity is an emerging clinical challenge with the widening use of immunotherapeutic agents in the field of oncology. This is an important complication to consider as more immune oncological targets are being identified to show promising results in clinical trials. The application of these therapeutics may be complicated by the development of immune-related adverse events (irAEs), a serious limitation often requiring high-dose immunosuppression and discontinuation of cancer therapy. Hepatoxicity presents one of the most frequently encountered irAEs and a better understanding of the underlying mechanism is crucial for the development of alternative therapeutic interventions. As a novel drug side effect, the immunopathogenesis of the condition is not completely understood. In the liver, myeloid cells play a central role in the maintenance of homeostasis and promotion of inflammation. Recent research has identified myeloid cells to be associated with hepatic adverse events of various immune modulatory monoclonal antibodies. In this review article, we provide an overview of the role of myeloid cells in the immune pathogenesis during hepatoxicity related to cancer immunotherapies and highlight potential treatment options.