The liver is a site for tumor-induced myeloid-derived suppressor cell accumulation and immunosuppression

Loss of two-pore channel 2 function in melanoma-derived tumours reduces tumour growth in vivo but greatly increases tumour-related toxicity in the organism

BACKGROUND

Melanoma, a severe form of skin cancer, poses significant health risks due to its aggressive nature and potential for metastasis. The role of two-pore channel 2 (TPC2) in the development and progression of melanoma remains poorly understood. This study aims to investigate the impact of TPC2 knockout (KO) on melanoma-derived tumors, focusing on tumour growth and related toxicity in the organism.

METHODS

The study utilized CHL-1 and B16 melanoma cell lines with TPC2 KO to assess the changes in proliferation dynamics. Methods included real-time monitoring of cell proliferation using the xCELLigence system, in vivo tumour growth assays in mice, histopathological analyses, inflammation marker assessment, and quantitative PCR (qPCR) for gene expression analysis RESULTS: TPC2 KO was found to significantly alter the proliferation dynamics of CHL-1 and B16 melanoma cells. The in vivo studies demonstrated reduced tumor growth in TPC2 KO cell-derived tumors. However, a notable increase in tumor-related toxicity in affected organs, such as the liver and spleen, was observed, indicating a complex role of TPC2 in melanoma pathology.

CONCLUSIONS

The loss of TPC2 function in melanoma cells leads to reduced tumour growth but exacerbates tumour-related toxicity in the organism. These findings highlight the dual role of TPC2 in melanoma progression and its potential as a therapeutic target. Further research is needed to fully understand the mechanisms underlying these effects and to explore TPC2 as a treatment target in melanoma.

Progress in research on the role played by myeloid-derived suppressor cells in liver diseases

Myeloid-derived suppressor cells (MDSCs) refer to a group of immature myeloid cells with potent immunosuppressive capacity upon activation by pathological conditions. Because of their potent immunosuppressive ability, MDSCs have garnered extensive attention in the past few years in the fields of oncology, infection, chronic inflammation and autoimmune diseases. Research on MDSCs in liver diseases has gradually increased, and their potential therapeutic roles will be further explored. This review presents a summary of the involvement and the role played by MDSCs in liver diseases, thus identifying their potential targets for the treatment of liver diseases and providing new directions for liver disease-related research.

Immunotherapy: an emerging modality to checkmate brain metastasis

The diagnosis of brain metastasis (BrM) has historically been a dooming diagnosis that is nothing less than a death sentence, with few treatment options for palliation or prolonging life. Among the few treatment options available, brain radiotherapy (RT) and surgical resection have been the backbone of therapy. Within the past couple of years, immunotherapy (IT), alone and in combination with traditional treatments, has emerged as a reckoning force to combat the spread of BrM and shrink tumor burden. This review compiles recent reports describing the potential role of IT in the treatment of BrM in various cancers. It also examines the impact of the tumor microenvironment of BrM on regulating the spread of cancer and the role IT can play in mitigating that spread. Lastly, this review also focuses on the future of IT and new clinical trials pushing the boundaries of IT in BrM.

Obesity contributes to hepatocellular carcinoma development via immunosuppressive microenvironment remodeling

It is generally recognized that the initiation of obesity-related hepatocellular carcinoma (HCC) is closely associated with hepatic inflammation. However, the paradoxical role of inflammation in the initiation and progression of HCC is highlighted by the fact that the inflammatory HCC is accompanied by significant immune effector cells infiltration compared to non-inflammatory HCC and HCC with enhanced immune response exhibits better survival. Importantly, the cancer progression has been primarily attributed to the immunosuppression, which can also be induced by obesity. Furthermore, the increased risk of viral infection and thus viral-HCC in obese individuals supports the view that obesity contributes to HCC via immunosuppression. Here, we have reviewed the various mechanisms responsible for obesity-induced tumor immune microenvironment and immunosuppression in obesity-related HCC. We highlight that the obesity-induced immunosuppression originates from lipid disorder as well as metabolic reprogramming and propose potential therapeutic strategy for HCC based on the current success of immunotherapy.

Hepatocellular carcinoma (HCC) immunotherapy by anti-PD-1 monoclonal antibodies: A rapidly evolving strategy

Hepatocellular carcinoma (HCC) is one of the deadliest cancers in the world, with a high relapse rate. Delayed symptom onset observed in 70-80% of patients leads to diagnosis in advanced stages commonly associated with chronic liver disease. Programmed cell death protein 1 (PD-1) blockade therapy has recently emerged as a promising therapeutic option in the clinical management of several advanced malignancies, including HCC, due to the activation of exhausted tumor-infiltrating lymphocytes and improved outcomes of T-cell function. However, many people with HCC do not respond to PD-1 blockade therapy, and the diversity of immune-related adverse events (irAEs) restricts their clinical utility. Therefore, numerous effective combinatory strategies, including combinations with anti-PD-1 antibodies and other therapeutic methods ranging from chemotherapy to targeted therapies, are evolving to improve therapeutic outcomes and evoke synergistic anti-tumor impressions in patients with advanced HCC. Unfortunately, combined therapy may have more side effects than single-agent treatment. Nonetheless, identifying appropriate predictive biomarkers can aid in managing potential immune-related adverse events by distinguishing patients who respond best to PD-1 inhibitors as single agents or in combination strategies. In the present review, we summarize the therapeutic potential of PD-1 blockade therapy for advanced HCC patients. Besides, a glimpse of the pivotal predictive biomarkers influencing a patient's response to anti-PD-1 antibodies will be provided.

Nivolumab plus ipilimumab combination therapy in cancer: Current evidence to date

Immune checkpoint inhibitors (ICIs) have revolutionized cancer immunotherapy, yielding significant antitumor responses across multiple cancer types. Combination ICI therapy with anti-CTLA-4 and anti-PD-1 antibodies outperforms either antibody alone in terms of clinical efficacy. As a consequence, the U.S. Food and Drug Administration (FDA) approved ipilimumab (anti-CTLA-4) plus nivolumab (anti-PD-1) as the first-ever approved therapies for combined ICI in patients with metastatic melanoma. Despite the success of ICIs, treatment with checkpoint inhibitor combinations poses significant clinical challenges, such as increased rates of immune-related adverse events (irAEs) and drug resistance. Thus, identifying optimal prognostic biomarkers could help to monitor the safety and efficacy of ICIs and identify patients who may benefit the most from these treatments. In this review, we will first go over the fundamentals of the CTLA-4 and PD-1 pathways, as well as the mechanisms of ICI resistance. The results of clinical findings that evaluated the combination of ipilimumab and nivolumab are then summarized to support future research in the field of combination therapy. Finally, the irAEs associated with combined ICI therapy, as well as the underlying biomarkers involved in their management, are discussed.

The role of myeloid-derived immunosuppressive cells in cardiovascular disease

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous cell population found in the bone marrow, peripheral blood, and tumor tissue. Their role is mainly to inhibit the monitoring function of innate and adaptive immune cells, which leads to the escape of tumor cells and promotes tumor development and metastasis. Moreover, recent studies have found that MDSCs are therapeutic in several autoimmune disorders due to their strong immunosuppressive ability. Additionally, studies have found that MDSCs have an important role in the formation and progression of other cardiovascular diseases, such as atherosclerosis, acute coronary syndrome, and hypertension. In this review, we will discuss the role of MDSCs in the pathogenesis and treatment of cardiovascular disease.

Targeted Lymphoma Therapy Using a Gold Nanoframework-Based Drug Delivery System

Precision nanomedicine can be employed as an alternative to chemo- or radiotherapy to overcome challenges associated with the often narrow therapeutic window of traditional treatment approaches, while safely inducing effective, targeted antitumor responses. Herein, we report the formulation of a therapeutic nanocomposite comprising a hyaluronic acid (HA)-coated gold nanoframework (AuNF) delivery system and encapsulated IT848, a small molecule with potent antilymphoma and -myeloma properties that targets the transcriptional activity of nuclear factor kappa B (NF-κB). The porous AuNFs fabricated via a liposome-templated approach were loaded with IT848 and surface-functionalized with HA to formulate the nanotherapeutics that were able to efficiently deliver the payload with high specificity to myeloma and lymphoma cell lines in vitro. In vivo studies characterized biodistribution, pharmacokinetics, and safety of HA-AuNFs, and we demonstrated superior efficacy of HA-AuNF-formulated IT848 vs free IT848 in lymphoma mouse models. Both in vitro and in vivo results affirm that the AuNF system can be adopted for targeted cancer therapy, improving the drug safety profile, and enhancing its efficacy with minimal dosing. HA-AuNF-formulated IT848 therefore has strong potential for clinical translation.

Mapping lesion-specific response and progression dynamics and inter-organ variability in metastatic colorectal cancer

Achieving systemic tumor control across metastases is vital for long-term patient survival but remains intractable in many patients. High lesion-level response heterogeneity persists, conferring many dissociated responses across metastatic lesions. Most studies of metastatic disease focus on tumor molecular and cellular features, which are crucial to elucidating the mechanisms underlying lesion-level variability. However, our understanding of lesion-specific heterogeneity on the macroscopic level, such as lesion dynamics in growth, response, and progression during treatment, remains rudimentary. This study investigates lesion-specific response heterogeneity through analyzing 116,542 observations of 40,612 lesions in 4,308 metastatic colorectal cancer (mCRC) patients. Despite significant differences in their response and progression dynamics, metastatic lesions converge on four phenotypes that vary with anatomical site. Importantly, we find that organ-level progression sequence is closely associated with patient long-term survival, and that patients with the first lesion progression in the liver often have worse survival. In conclusion, our study provides insights into lesion-specific response and progression heterogeneity in mCRC and creates impetus for metastasis-specific therapeutics.

Immunotherapy for Hepatocellular Carcinoma in the Setting of Liver Transplantation: A Review

The emerging field of immuno-oncology has brought exciting developments in the treatment of hepatocellular carcinoma (HCC). It has also raised urgent questions about the role of immunotherapy in the setting of liver transplantation, both before and after transplant. A growing body of evidence points to the safety and efficacy of immunotherapeutic agents as potential adjuncts for successful down-staging of advanced HCCs to allow successful transplant in carefully selected patients. For patients with recurrent HCC post-transplant, immunotherapy has a limited, yet growing role. In this review, we describe optimal regimens in the setting of liver transplantation.

Hematologic dysfunction in cancer: Mechanisms, effects on antitumor immunity, and roles in disease progression

With the major advances in cancer immunology and immunotherapy, it is critical to consider that most immune cells are short-lived and need to be continuously replenished from hematopoietic stem and progenitor cells. Hematologic abnormalities are prevalent in cancer patients, and many ground-breaking studies over the past decade provide insights into their underlying cellular and molecular mechanisms. Such studies demonstrate that the dysfunction of hematopoiesis is more than a side-effect of cancer pathology, but an important systemic feature of cancer disease. Here we review these many advances, covering the cancer-associated phenotypes of hematopoietic stem and progenitor cells, the dysfunction of myelopoiesis and erythropoiesis, the importance of extramedullary hematopoiesis in cancer disease, and the developmental origins of tumor associated macrophages. We address the roles of many secreted mediators, signaling pathways, and transcriptional and epigenetic mechanisms that mediate such hematopoietic dysfunction. Furthermore, we discuss the important contribution of the hematopoietic dysfunction to cancer immunosuppression, the possible avenues for therapeutic intervention, and highlight the unanswered questions and directions for future work. Overall, hematopoietic dysfunction is established as an active component of the cancer disease mechanisms and an important target for therapeutic intervention.

Exploring the role of mast cells in the progression of liver disease

In addition to being associated with allergic diseases, parasites, bacteria, and venoms, a growing body of research indicates that mast cells and their mediators can regulate liver disease progression. When mast cells are activated, they degranulate and release many mediators, such as histamine, tryptase, chymase, transforming growth factor-β1 (TGF-β1), tumor necrosis factor–α(TNF-α), interleukins cytokines, and other substances that mediate the progression of liver disease. This article reviews the role of mast cells and their secretory mediators in developing hepatitis, cirrhosis and hepatocellular carcinoma (HCC) and their essential role in immunotherapy. Targeting MC infiltration may be a novel therapeutic option for improving liver disease progression.

The Hepatic Pre-Metastatic Niche

Simple Summary

The pre-metastatic niche is a recently established concept that could lead to targeted therapies that prevent metastasis before ever occurring. Considering that 90% of cancer mortality results from metastasis, the PMN is thus a salient opportunity for intervention. The purpose of the current review is to cover what is known specifically about the hepatic pre-metastatic niche, a topic that has garnered increasing research focus within the last decade. We discuss the methods of communication between primary tumors and the liver, the involved cell populations, the key changes within liver tissue, and perspectives on the future of the field.

Abstract

Primary tumors can communicate with the liver to establish a microenvironment that favors metastatic colonization prior to dissemination, forming what is termed the “pre-metastatic niche” (PMN). Through diverse signaling mechanisms, distant malignancies can both influence hepatic cells directly as well as recruit immune cells into the PMN. The result is a set of changes within the hepatic tissue that increase susceptibility of tumor cell invasion and outgrowth upon dissemination. Thus, the PMN offers a novel step in the traditional metastatic cascade that could offer opportunities for clinical intervention. The involved signaling molecules also offer promise as biomarkers. Ultimately, while the existence of the hepatic PMN is well-established, continued research effort and use of innovative models are required to reach a functional knowledge of PMN mechanisms that can be further targeted.

Comprehensive Analysis of HHLA2 as a Prognostic Biomarker and Its Association With Immune Infiltrates in Hepatocellular Carcinoma

Background

Inhibitory immune checkpoint proteins promote tumor immune escape and are associated with inferior patient outcome. However, the biological functions and regulatory roles of one of its members, HHLA2, in the tumor immune microenvironment have not been explored.

Methods

RandomForest analyses (371 cases), qRT-PCR (15 cases), and immunohistochemical staining (189 cases) were used to validate the prognostic value of HHLA2 in hepatocellular carcinoma (HCC) patients. Bioinformatic analyses were further performed to explore the biological functions and potential signaling pathways affected by HHLA2. Moreover, ESTIMATE, single sample gene set enrichment analysis, CIBERSORT, TIMER, and other deconvolution methods were used to analyze the composition and infiltration level of immune cells. Multiplex immunofluorescence assays were employed to validate the fractions of suppressive immune cells, and HHLA2-related molecular alterations were investigated. Finally, the clinical response to chemotherapy and immune checkpoint blockade was predicted by TIDE, Submap, and several other in silico analyses.

Results

RandomForest analysis revealed that HHLA2 was the most important inhibitory immune checkpoint associated with HCC patient prognosis (relative importance = 1). Our HCC cohorts further revealed that high HHLA2 expression was an independent prognostic biomarker of shorter overall survival (P<0.01) and time to recurrence (P<0.001) for HCC patients. Bioinformatics experiments revealed that HHLA2 may accelerate the cell cycle of cancer cells. Additionally, we found that high expression of HHLA2 was associated with immune infiltrates, including some immunosuppressive cells, cytokines, chemokines, and corresponding receptors, resulting in an immunosuppressive environment. Notably, HHLA2 expression was positively correlated with the infiltration of exhausted CD8+ T cells, which was validated by immunofluorescence. Genomic alteration analyses revealed that promoter hypermethylation of HHLA2 may be associated with its low expression. More importantly, patients with high HHLA2 expression may be more sensitive to chemotherapy and have better responses to immunotherapy.

Conclusions

High expression of HHLA2 is an independent prognostic biomarker for HCC patients. It can activate the cell cycle and foster an immunosuppressive tumor microenvironment by enriching exhausted CD8+ T cells. Promoter hypermethylation might lead to low expression of HHLA2 in HCC. Thus, targeting HHLA2 may be a practical therapeutic strategy for HCC patients in the future.

Rapidly Evolving Landscape and Future Horizons in Hepatocellular Carcinoma in the Era of Immuno-Oncology

Hepatocellular carcinoma (HCC) is a serious global health problem as one of the leading causes of cancer-related death worldwide. Systemic therapy for advanced HCC has progressed with the development of molecular targeted agents, however survival benefits remain modest. More recently, immune checkpoint inhibitors (ICI) have emerged and exhibited promising therapeutic benefits in a subset of patients. Physiologically, the intrinsic microenvironment in the liver is immunosuppressive, which represents a major obstacle for effective immune therapies in primary and secondary liver malignancies. For this reason, combination therapies that can overcome immune inhibitory mechanisms and enhance the immune response are a rationale approach for drug development in HCC. A recent example is the combination of the anti-PD-L1 antibody (atezolizumab) and anti-VEGF-A antibody (bevacizumab), which has shown significant improvement in survival as compared to standard of care in the first-line treatment for HCC. Other immunotherapy approaches including cancer vaccines and adoptive cell therapy are also under investigation. This review summarizes the key trials leading to our current HCC treatment options and provides an overview of future immune-based strategies in development.

Dual-sgRNA CRISPR/Cas9 knockout of PD-L1 in human U87 glioblastoma tumor cells inhibits proliferation, invasion, and tumor-associated macrophage polarization

Programmed death ligand 1 (PD-L1) plays a key role in glioblastoma multiforme (GBM) immunosuppression, vitality, proliferation, and migration, and is therefore a promising target for treating GBM. CRISPR/Cas9-mediated genomic editing can delete both cell surface and intracellular PD-L1. This systemic deliverable genomic PD-L1 deletion system can be used as an effective anti-GBM therapy by inhibiting tumor growth and migration, and overcoming immunosuppression. To target PD-L1 for CRISPR/Cas9 gene editing, we first identified two single guide RNA (sgRNA) sequences located on PD-L1 exon 3. The first sgRNA recognizes the forward strand of human PD-L1 near the beginning of exon 3 that allows editing by Cas9 at approximately base pair 82 (g82). The second sgRNA recognizes the forward strand of exon 3 that directs cutting at base pair 165 (g165). A homology-directed repair template (HDR) combined with the dual-sgRNAs was used to improve PD-L1 knockout specificity and efficiency. sgRNAs g82 and g165 were cloned into the multiplex CRISPR/Cas9 assembly system and co-transfected with the HDR template in human U87 GBM cells (g82/165 + HDR). T7E1 analysis suggests that the dual-sgRNA CRISPR/Cas9 strategy with a repair template was capable of editing the genomic level of PD-L1. This was further confirmed by examining PD-L1 protein levels by western blot and immunofluorescence assays. Western blot analysis showed that the dual-sgRNAs with the repair template caused a 64% reduction of PD-L1 protein levels in U87 cells, while immunostaining showed a significant reduction of intracellular PD-L1. PD-L1 deletion inhibited proliferation, growth, invasion and migration of U87 cells, indicating intracellular PD-L1 is necessary for tumor progression. Importantly, U87 cells treated with g82/165 + HDR polarized tumor-associated macrophages (TAM) toward an M1 phenotype, as indicated by an increase in TNF-α and a decrease in IL-4 secretions. This was further confirmed with flow cytometry that showed an increase in the M1 markers Ly6C + and CD80 +, and a decrease in the M2 marker CD206 + both in vitro and in vivo. Utilizing dual-sgRNAs and an HDR template with the CRISPR/Cas9 gene-editing system is a promising avenue for the treatment of GBM.

A Combination of Cabozantinib and Radiation Does Not Lead to an Improved Growth Control of Tumors in a Preclinical 4T1 Breast Cancer Model

The tyrosine kinase inhibitor Cabozantinib has been applied in clinical studies in combination with radiotherapy. We investigated the effect of such combination on triple-negative 4T1 cells as a metastatic breast cancer model in vitro and in vivo upon inoculation in BALB/c mice. In vitro assays indicated a potential for improved effects using the combination. Both Cabozantinib (2.5 µM) and 10 Gy of 250 kV x-rays were able to cease the growth of 4T1 cells as revealed by growth curves. In a clonogenic survival assay, the effect of Cabozantinib added on the effects of irradiation and the effectiveness of inhibiting the clonogenic survival was found to be 2 (RBE₁₀). Additionally, cell death measurements of apoptosis plus necrosis revealed a synergistic effect when combining irradiation with Cabozantinib. Surprisingly, however, in vivo tumor growth kinetics showed no additional effect in growth control when irradiation was used together with Cabozantinib. Since both ionizing radiation and Cabozantinib are acknowledged to feature immunogenic effects, we additionally investigated the effect of the treatments on lung metastases. No difference to the control groups was found here, neither for irradiation nor Cabozantinib alone nor in combination. Yet, upon analysis of the mice’ livers, CD11b-positive cells, indicating immune suppressive myeloid derived suppressor cells were found diminished following treatment with Cabozantinib. In conclusion, despite promising in vitro controls of the combination of Cabozantinib and irradiation, tumor growth control was not increased by the combination, which was true also for the occurrence of lung metastases.

Anatomical Distribution of Myeloid-Derived Suppressor Cells During HIV Infection

In recent years, expansion of myeloid-derived suppressor cells (MDSCs) has been reported to play a detrimental role in the pathogenesis of human immunodeficiency virus (HIV) infection. Much effort has been focused to comprehend the mechanisms and factors that regulate the expansion of such unwanted immune cell populations. Of particular interest has been the mechanisms by which MDSCs could contribute to the pathogenesis of HIV infection. So far, the studies have been restricted to MDSCs in the circulatory system of HIV patients, but not in other tissue compartments. In fact, lymphatic tissues/organs are the primary sites where HIV replication and immune depletion/dysfunction occur during the course of HIV infection. Therefore, investigating the anatomical distribution of MDSCs in such compartments is essential to understand the role that they play in the pathogenesis of HIV infection. Hence, we aim to shed light on the available literature about the anatomical distribution of MDSCs during HIV infection and compare it with the distribution of MDSCs in other pathological conditions, mainly cancer.

Myeloid-Derived Suppressor Cells: A Propitious Road to Clinic

Myeloid-derived suppressor cells (MDSC) are important regulators of immune responses in cancer. They represent a relatively stable form of pathologic activation of neutrophils and monocytes and are characterized by distinct transcriptional, biochemical, functional, and phenotypical features. The close association of MDSCs with clinical outcomes in cancer suggests that these cells can be an attractive target for therapeutic intervention. However, the complex nature of MDSC biology represents a substantial challenge for the development of selective therapies. Here, we discuss the mechanisms regulating MDSC development and fate and recent research advances that have demonstrated opportunities for therapeutic regulation of these cells. SIGNIFICANCE: MDSCs are attractive therapeutic targets because of their close association with negative clinical outcomes in cancer and established biology as potent immunosuppressive cells. However, the complex nature of MDSC biology presents a substantial challenge for therapeutic targeting. In this review, we discuss those challenges and possible solutions.

Monocytic MDSC mobilization promotes tumor recurrence after liver transplantation via CXCL10/TLR4/MMP14 signaling

Tumor recurrence is the major obstacle for pushing the envelope of liver transplantation for hepatocellular carcinoma (HCC) patients. The inflammatory cascades activated by acute liver graft injury promote tumor recurrence. We aimed to explore the role and mechanism of myeloid-derived suppressor cell (MDSC) mobilization induced by liver graft injury on tumor recurrence. By analyzing 331 HCC patients who received liver transplantation, the patients with graft weight ratio (GWR, the weight of liver graft divided by the estimated standard liver weight of recipient) <60% had higher tumor recurrence than GWR ≥60% ones. MDSCs and CXCL10/TLR4 levels were significantly increased in patients with GWR <60% or tumor recurrence. These findings were further validated in our rat orthotopic liver transplantation model. In CXCL10^−/− and TLR4^−/− mice of hepatic ischemia/reperfusion injury plus major hepatectomy (IRH) model, monocytic MDSCs, instead of granulocytic MDSCs, were significantly decreased. Importantly, CXCL10 deficiency reduced the accumulation of TLR4⁺ monocytic MDSCs, and CXCL10 increased MDSC mobilization in the presence of TLR4. Moreover, MMP14 was identified as the key molecule bridging CXCL10/TLR4 signaling and MDSC mobilization. Knockout or inhibition of CXCL10/TLR4 signaling significantly reduced the tumor growth with decreased monocytic MDSCs and MMP14 in the mouse tumor recurrent model. Our data indicated that monocytic MDSCs were mobilized and recruited to liver graft during acute phase injury, and to promote HCC recurrence after transplantation. Targeting MDSC mobilization via CXCL10/TLR4/MMP14 signaling may represent the therapeutic potential in decreasing post-transplant liver tumor recurrence.

The Timing of Liver Transplantation Following Downstaging: Wait of Not to Wait?

PURPOSE

HCC is a complex disease that is diagnosed in advanced stage and on the background of cirrhosis. Locoregional therapies provide sufficient downstaging to enable patients suitable for radical procedures such liver transplantation. However, the interval between locoregional therapies and definitive therapy is still controversial. We performed a review of literature to evaluate the role of waiting period between locoregional therapies and liver transplantation or resection from the perspective of cure and recurrence rates.

METHODS

Thorough literature search was performed to evaluate the role of locoregional therapy and the interval to definitive therapies for the treatment of hepatocellular cancer.

RESULTS

Usually, small tumors with lower tumor burden, in other words, tumors within Milan criteria, can be transplanted with an acceptable overall and disease-free survival. However, treating patients with locally advanced tumors is currently a matter of extensive research. Currently, locoregional therapies are applied to downstage the patients. However, the duration of waiting is a crucial point that needs further research. There is a consensus that the waiting interval between down-staging and transplantation should be no less than 3 months. This is important for selection of favorable tumor biology as well as from the point of antitumor immune response.

CONCLUSION

Currently, there are no surrogate markers for surveillance of response to locoregional therapies as well as the antitumor immune response that develops as a result of down-staging.

In Situ Vaccination as a Strategy to Modulate the Immune Microenvironment of Hepatocellular Carcinoma

Hepatocellular Carcinoma (HCC) is a highly prevalent malignancy that develops in patients with chronic liver diseases and dysregulated systemic and hepatic immunity. The tumor microenvironment (TME) contains tumor-associated macrophages (TAM), cancer-associated fibroblasts (CAF), regulatory T cells (Treg) and myeloid-derived suppressor cells (MDSC) and is central to mediating immune evasion and resistance to therapy. The interplay between these cells types often leads to insufficient antigen presentation, preventing effective anti-tumor immune responses. In situ vaccines harness the tumor as the source of antigens and implement sequential immunomodulation to generate systemic and lasting antitumor immunity. Thus, in situ vaccines hold the promise to induce a switch from an immunosuppressive environment where HCC cells evade antigen presentation and suppress T cell responses towards an immunostimulatory environment enriched for activated cytotoxic cells. Pivotal steps of in situ vaccination include the induction of immunogenic cell death of tumor cells, a recruitment of antigen-presenting cells with a focus on dendritic cells, their loading and maturation and a subsequent cross-priming of CD8+ T cells to ensure cytotoxic activity against tumor cells. Several in situ vaccine approaches have been suggested, with vaccine regimens including oncolytic viruses, Flt3L, GM-CSF and TLR agonists. Moreover, combinations with checkpoint inhibitors have been suggested in HCC and other tumor entities. This review will give an overview of various in situ vaccine strategies for HCC, highlighting the potentials and pitfalls of in situ vaccines to treat liver cancer.

Immunotherapy Updates in Advanced Hepatocellular Carcinoma

Simple Summary

Advanced hepatocellular carcinoma (HCC) carries a grim prognosis, which has historically been compounded by a lack of available systemic therapies. Sorafenib monotherapy was the standard of care for front-line treatment of advanced HCC for many years, despite both poor tolerability and lack of durable responses. In the past few years, there have been several clinical trials evaluating the efficacy of immune checkpoint inhibitors for advanced HCC. Use of immune checkpoint inhibitors alone, and in combination with targeted therapies, has led to improved outcomes in both treatment-naïve and subsequent line treatment of advanced HCC. Here we review the role of immunotherapy in the treatment of HCC, describe the mechanistic basis for combination with targeted therapy, and summarize the recent published data as well as ongoing clinical trials for the use of immunotherapy in the treatment of advanced HCC.

Abstract

Hepatocellular carcinoma (HCC) is the second most common cause of cancer death worldwide. HCC tumor development and treatment resistance are impacted by changes in the microenvironment of the hepatic immune system. Immunotherapy has the potential to improve response rates by overcoming immune tolerance mechanisms and strengthening anti-tumor activity in the tumor microenvironment. In this review, we characterize the impact of immunotherapy on outcomes of advanced HCC, as well as the active clinical trials evaluating novel combination immunotherapy strategies. In particular, we discuss the efficacy of atezolizumab and bevacizumab as demonstrated in the IMbrave150 study, which created a new standard of care for the front-line treatment of advanced HCC. However, there are multiple ongoing trials that may present additional front-line treatment options depending on their efficacy/toxicity results. Furthermore, the preliminary data on the application of chimeric antigen receptor (CAR-T) cell therapy for treatment of HCC suggests this may be a promising option for the future of advanced HCC treatment.

Antacid exposure and immunotherapy outcomes among patients with advanced hepatocellular carcinoma

BACKGROUND

Antibiotic exposure has been associated with worse outcomes with immune checkpoint inhibitors (ICIs) in cancer patients, likely due to disruption of the gut microbiome. Other commonly prescribed medications, such as proton pump inhibitors (PPIs) and histamine-2-receptor antagonists (H2RAs), are also known to disrupt the microbiome, but data on their association with ICI outcomes are conflicting.

METHODS

We conducted a retrospective, multicenter, international cohort study including 314 hepatocellular carcinoma (HCC) patients treated with ICIs from 2017 to 2019 to assess the association between PPI or H2RA exposure (up to 30 days before ICI) and overall survival. Secondary outcomes included overall response rate (ORR) and development of any treatment-related adverse events (AEs).

RESULTS

Baseline PPI/H2RA exposure was not associated with overall survival in univariable (HR 1.01, 95% CI 0.75-1.35) or multivariable analysis (HR 0.98, 95% CI 0.71-1.36). Baseline PPI/H2RA exposure was not associated with either ORR (OR 1.32, 95% CI 0.66-2.65) or AEs (OR 1.07, 95% CI 0.54-2.12) in multivariable analysis.

CONCLUSIONS

Our results suggest that exposure to PPI/H2RA prior to ICIs does not adversely affect outcomes in HCC patients.

Targeting the tumor microenvironment in cholangiocarcinoma: implications for therapy

Introduction: Cholangiocarcinomas (CCAs) are biliary epithelial tumors with rising incidence over the past 3 decades. Early diagnosis of CCAs remains a significant challenge and the majority of patients present at an advanced stage. CCAs are heterogeneous tumors and currently available standard systemic therapy options are of limited effectiveness. Immune checkpoint inhibition (ICI) has transformed cancer therapy across a spectrum of malignancies. However, the response rate to ICI has been relatively disappointing in CCAs owing to its desmoplastic tumor microenvironment (TME).Areas covered: Tumor microenvironment of CCAs consists of innate and adaptive cells, stromal cells, and extracellular components (cytokines, chemokines, exosomes, etc.). This intricate microenvironment has multiple immunosuppressive elements that promote tumor cell survival and therapeutic resistance. Accordingly, there is a need for the development of effective therapeutic strategies that target the TME. Herein, we review the components of the CCA TME, and potential therapies targeting the CCA TME.Expert opinion: CCAs are desmoplastic tumors with a dense tumor microenvironment. An enhanced understanding of the various components of the CCA TME is essential in the effort to develop novel biomarkers for patient stratification as well as combination therapeutic strategies that target the tumor plus the TME.

OMO-1 reduces progression and enhances cisplatin efficacy in a 4T1-based non-c-MET addicted intraductal mouse model for triple-negative breast cancer

c-MET is considered a driver of cancer progression, impacting tumor growth and tumor-supporting stroma. Here, we investigated the therapeutic efficacy of OMO-1, a potent and selective c-MET inhibitor, in an immunocompetent intraductal mouse model for triple-negative breast cancer (TNBC). OMO-1 reduced non-c-MET addicted 4T1 tumor progression dose dependently as monotherapeutic and provided additional disease reduction in combination with cisplatin. At the stromal level, OMO-1 significantly reduced neutrophil infiltration in 4T1 tumors, promoted immune activation, and enhanced cisplatin-mediated reduction of tumor-associated macrophages. OMO-1 treatment also reduced 4T1 tumor hypoxia and increased expression of pericyte markers, indicative for vascular maturation. Corroborating this finding, cisplatin delivery to the 4T1 primary tumor was enhanced upon OMO-1 treatment, increasing cisplatin DNA-adduct levels and tumor cell death. Although verification in additional cell lines is warranted, our findings provide initial evidence that TNBC patients may benefit from OMO-1 treatment, even in cases of non-c-MET addicted tumors.

Depletion of phagocytic myeloid cells triggers spontaneous T cell- and NK cell-dependent antitumor activity

Depletion of tumor associated macrophages and inhibition of tumor angiogenesis have been invoked as the principle mechanisms underlying the antitumor activity of liposomal clodronate (LC). However, previous studies have not examined the effects of LC on systemic antitumor immunity. Here, we used mouse tumor models to elucidate the role of T and NK cells in the antitumor activity elicited by the systemic administration of LC. Strikingly, we found that the antitumor activity of LC is completely abolished in immunodeficient Rag1^−/− mice. Moreover, both Cd4^−/− and Cd8^−/− mice as well as mice depleted of NK cells manifested a significant impaired ability to control tumor growth following LC administration. Treatment with LC did not result in an overall increase in T- or NK-cell numbers in tumors or lymphoid organs, nor was tumor infiltration with T or NK cells altered. However, T and NK cells isolated from the spleen of LC-treated mice exhibited significant increased tumor-specific secretion of interferon γ and interleukin 17 and greater cytolytic activity. We concluded that the antitumor effects of LC are largely dependent on the generation of systemic T-cell and NK- cell activity, most likely owing to the depletion of immune suppressive myeloid cell populations in lymphoid tissues. These findings suggest that the systemic administration of LC may constitute an effective means for non-specifically augmenting the antitumor activity of T and NK cells.

MDSCs in liver cancer: A critical tumor-promoting player and a potential therapeutic target

Liver cancer is a leading cause of cancer deaths worldwide. Hepatocellular carcinoma (~75-85%) and cholangiocarcinoma (~10-15%) account for the majority of primary liver malignancies. Patients with primary liver cancer are often diagnosed with unresectable diseases and do not respond well to current therapies. The liver is also a common site of metastasis. Liver metastasis is difficult to treat, and the prognosis is poor. Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of immature myeloid cells with immunosuppressive activity. MDSCs are an important component of the tumor microenvironment and promote tumor progression through various mechanisms. MDSCs expand in both liver cancer patients and mouse liver cancer models. Importantly, MDSCs correlate with poor clinical outcomes for liver cancer patients. The tumor-promoting functions of MDSCs have also been shown in mouse liver cancer models. All these studies suggest that targeting MDSCs can potentially benefit liver cancer treatment. This review summarizes the current findings of MDSC regulation in liver cancer and related disease conditions.

Combined paclitaxel-doxorubicin liposomal results in positive prognosis with infiltrating lymphocytes in lung metastasis

Aim: To investigate the effect of liposomes containing the classical cytotoxic drugs paclitaxel and doxorubicin (Lipo-Pacli/Dox), against a metastatic breast cancer model. We also investigated if Lipo-Pacli/Dox was capable of reverting the tolerogenic environment of metastatic lesions. Materials & methods: Immunogenic cell death induction by the Pacli/Dox combination was assessed in vitro. Antitumor activity and in vivo safety of Lipo-Pacli/Dox were evaluated using a 4T1 breast cancer mouse model Results: Lipo-Pacli/Dox, with a size of 189 nm and zeta potential of -5.01 mV, promoted immune system activation and partially controlled the progression of pulmonary metastasis. Conclusion: Lipo-Pacli/Dox was useful to control both primary tumor and lung metastasis in breast cancer (4T1) mice model. Additionally, Lipo-Pacli/Dox acts as an immunological modulator for this metastatic breast cancer model.

Immunomodulatory Role of the Extracellular Matrix Within the Liver Disease Microenvironment

Chronic liver disease when accompanied by underlying fibrosis, is characterized by an accumulation of extracellular matrix (ECM) proteins and chronic inflammation. Although traditionally considered as a passive and largely architectural structure, the ECM is now being recognized as a source of potent damage-associated molecular pattern (DAMP)s with immune-active peptides and domains. In parallel, the ECM anchors a range of cytokines, chemokines and growth factors, all of which are capable of modulating immune responses. A growing body of evidence shows that ECM proteins themselves are capable of modulating immunity either directly via ligation with immune cell receptors including integrins and TLRs, or indirectly through release of immunoactive molecules such as cytokines which are stored within the ECM structure. Notably, ECM deposition and remodeling during injury and fibrosis can result in release or formation of ECM-DAMPs within the tissue, which can promote local inflammatory immune response and chemotactic immune cell recruitment and inflammation. It is well described that the ECM and immune response are interlinked and mutually participate in driving fibrosis, although their precise interactions in the context of chronic liver disease are poorly understood. This review aims to describe the known pro-/anti-inflammatory and fibrogenic properties of ECM proteins and DAMPs, with particular reference to the immunomodulatory properties of the ECM in the context of chronic liver disease. Finally, we discuss the importance of developing novel biotechnological platforms based on decellularized ECM-scaffolds, which provide opportunities to directly explore liver ECM-immune cell interactions in greater detail.

Mechanisms of immune suppression by myeloid-derived suppressor cells: the role of interleukin-10 as a key immunoregulatory cytokine

Chronic immune activation and inflammation are unwanted consequences of many pathological conditions, since they could lead to tissue damage and immune exhaustion, both of which can worsen the pathological condition status. In fact, the immune system is naturally equipped with immunoregulatory cells that can limit immune activation and inflammation. However, chronic activation of downregulatory immune responses is also associated with unwanted consequences that, in turn, could lead to disease progression as seen in the case of cancer and chronic infections. Myeloid-derived suppressor cells (MDSCs) are now considered to play a pivotal role in the pathogenesis of different inflammatory pathological conditions, including different types of cancer and chronic infections. As a potent immunosuppressor cell population, MDSCs can inhibit specific and non-specific immune responses via different mechanisms that, in turn, lead to disease persistence. One such mechanism by which MDSCs can activate their immunosuppressive effects is accomplished by secreting copious amounts of immunosuppressant molecules such as interleukin-10 (IL-10). In this article, we will focus on the pathological role of MDSC expansion in chronic inflammatory conditions including cancer, sepsis/infection, autoimmunity, asthma and ageing, as well as some of the mechanisms by which MDSCs/IL-10 contribute to the disease progression in such conditions.

Recent advances in myeloid-derived suppressor cell biology

In recent years, studying the role of myeloid-derived suppressor cells (MDSCs) in many pathological inflammatory conditions has become a very active research area. Although the role of MDSCs in cancer is relatively well established, their role in non-cancerous pathological conditions remains in its infancy resulting in much confusion. Our objectives in this review are to address some recent advances in MDSC research in order to minimize such confusion and to provide an insight into their function in the context of other diseases. The following topics will be specifically focused upon: (1) definition and characterization of MDSCs; (2) whether all MDSC populations consist of immature cells; (3) technical issues in MDSC isolation, estimation and characterization; (4) the origin of MDSCs and their anatomical distribution in health and disease; (5) mediators of MDSC expansion and accumulation; (6) factors that determine the expansion of one MDSC population over the other; (7) the Yin and Yang roles of MDSCs. Moreover, the functions of MDSCs will be addressed throughout the text.

Gr-1highLy6G+Myeloid-derived suppressor cells and their role in a murine model of non-alcoholic steatohepatitis

BACKGROUND AND AIM

Myeloid-derived suppressor cells are a heterogeneous cell population that expand during several pathogenic conditions. However, their role in non-alcoholic steatohepatitis remains unclear. This study aimed to examine the systemic effects of myeloid-derived suppressor cells, to determine the role of Gr-1^highLy6G⁺MDSCs and their correlation with the CXCL12/CXCR4 axis in non-alcoholic steatohepatitis.

METHODS

We established a non-alcoholic steatohepatitis model and detected inflammatory factors IL-6, PGE2, and INF-γ, using an enzyme-linked immunosorbent assay. Proportions of lymphocyte subsets in peripheral blood, CD11b⁺Gr-1⁺myeloid-derived suppressor cells and its subsets in the blood, spleen, liver, and bone marrow were identified using flow cytometry. Adoptive transfer and depletion experiments for MDSCs were performed. Immunohistochemistry, migration assays, and in vivo experiments were used to analyze the role of CXCL12/CXCR4 in non-alcoholic steatohepatitis.

RESULTS

The proportion of CD11b⁺Gr-1⁺MDSCs changed in the bone marrow, spleen, blood, and liver in the non-alcoholic steatohepatitis model. CD4+ and CD8+ T lymphocytes were significantly reduced in non-alcoholic steatohepatitis. Compared with control mice, a significant decrease in ALT and AST levels was observed in Gr-1^highLy6G⁺MDSCs-treated model mice. The migration ability of AMD3100-treated MDSCs was significantly reduced, but was restored as CXCL12 levels increased. CXCL12 and CXCR4 protein levels increased significantly in the non-alcoholic steatohepatitis livers.

CONCLUSIONS

Exogenous Gr-1^highLy6G⁺MDSCs improved liver function during non-alcoholic steatohepatitis. The CXCR4/CXCL12 axis could be the key pathway mediating the attraction of myeloid-derived suppressor cells into the non-alcoholic steatohepatitis environment in mice.

Paradoxes in the Phenotype, Frequency and Roles of Myeloid-Derived Suppressor Cells During HIV Infection

Myeloid-derived suppressor cells (MDSCs) are heterogeneous groups of pathologically activated myeloid cells with potent immunosuppressive function. Due to their role in negatively regulating the immune system, MDSCs have been strongly correlated with disease progression during HIV. However, findings vary considerably between studies. The dominant phenotype of MDSC subsets during HIV is not well ascertained. Moreover, there is no clear understanding on the clinical significance of MDSCs during HIV infection. The existing evidences showed the double-sided roles of MDSCs in HIV. On the one hand, MDSCs are linked to deleterious effects during HIV infection as they inhibit proliferation of protective T cell response. On the other hand, the immunosuppressive abilities of MDSCs were shown to be beneficial in curbing the damaging effects of persistent immune activation associated with chronic HIV infection. Therefore, this review aimed to describe the differences in the existing literatures pertaining to the phenotype, frequency and roles of MDSCs during HIV infection.

The Immune Modulation Effect of Locoregional Therapies and Its Potential Synergy with Immunotherapy in Hepatocellular Carcinoma

Locoregional therapies (LRTs) including radiofrequency ablation, surgical resection, and TACE, play a pivotal role in the treatment of early stage/locally advanced hepatocellular carcinoma (HCC). Besides their direct effect on tumor cells, LRTs also play an essential role in the immunomodulation of the tumor microenvironment which is of interest in the current era of cancer immunotherapy. In this review, we describe the HCC immune microenvironment and how it is affected by LRTs as described in multiple pre-clinical and clinical studies and provide the rationale for combining LRTs with immunotherapy.

Anti-inflammatory and metabolic reprogramming effects of MENK produce antitumor response in CT26 tumor-bearing mice

Methionine enkephalin (MENK), an endogenous opioid peptide, has a role in nervous system, immune system, and anticancer therapy. Inflammation, metabolism and cancer are closely intertwined with each other. This study is to identify the correlation of the antitumor effects of MENK with systemic inflammation, liver metabolism, and immune cells as myeloid-derived suppressor cells (MDSCs). We established a subcutaneous CT26 colon carcinoma model and a cyclophosphamide-induced immunosuppressive model subjected to MENK. AML12 and MDSCs were used as in vitro models. The results showed that MENK treatment degraded tumor growth and inhibited proinflammatory cytokines both in tumor tissues and serum. The MENK-treated tumor mice showed normalized liver function with glycolipid metabolic homeostasis. No inhibitory effect on CT26 tumor cell in vitro, but only reduced lipid synthesis in AML12 were presented by MENK. Meanwhile, MENK invigorated immune response in both two animal models by markedly suppressing MDSCs and enhancing T cells response. In vitro MENK-treated MDSCs showed reduced glycolysis and less ROS production, which was mediated by PI3K/AKT/mTOR pathway. Opioid receptor antagonist naltrexone reversed most of the regulation. These results illustrate that MENK preventing development of colon carcinoma might be correlated with the suppression of inflammation, improving metabolism in liver as well as in MDSCs partly through opioid receptor, which brings new elements supporting the adjuvant therapy for tumor by MENK.

Evaluating the Safety and Efficacy of Nivolumab in Patients with Advanced Hepatocellular Carcinoma: Evidence to Date

Hepatocellular carcinoma (HCC) is the most common primary liver cancer with a dismal prognosis, especially when diagnosed at advanced stages. Surgical resection of the primary lesion, liver-directed therapies, and orthotropic liver transplantation are employed in localized disease depending upon the clinical status, underlying liver function, the size, and location of the liver lesions. Systemic therapy plays a critical role in the management of advanced HCC. Sorafenib had remained as the only United States Food and Drug Administration (US-FDA)-approved systemic therapeutic agent for approximately a decade since its approval in 2007, until the advent of immunotherapy and a better understanding of HCC molecular pathogenesis changed the landscape of advanced HCC management. Lenvatinib was approved as an alternative first-line agent, whereas regorafenib, nivolumab, pembrolizumab, ramucirumab, and cabozantinib were approved as second-line agents for HCC patients who could not tolerate or whose disease progressed on sorafenib. Nivolumab and pembrolizumab are the two immunotherapeutic agents that were conditionally approved by the US-FDA based on the encouraging results in Phase I/II trials. This review discusses the potential role of immunotherapy in advanced HCC with a special focus on nivolumab.

Interleukin-35 Regulates Immune Microenvironment of Autoimmune Hepatitis Through Inducing the Expansion of Myeloid-Derived Suppressor Cells

Interleukin-35 (IL-35) is a novel anti-inflammatory cytokine of IL12 cytokine family, however, the role of IL-35 in patients with AIH and its effect on myeloid-derived suppressor cells (MDSCs) has not yet been analyzed. The expression of IL-35 subunits (p35 and EBI3) in liver tissues was quantified by immunochemistry and its correlation with clinical parameters was explored in patients with AIH. The expression of MDSCs and IL-35 receptor (gp130 and IL-12Rβ2) were analyzed using flow cytometry and confocal staining. Besides, we utilized in vitro culture to explore the role of IL-35 on MDSCs expansion and activation. We found that the elevated expression of both IL-35 subunits (EBI3 and p35) in liver tissue was positively associated with degrees of hepatic inflammatory and fibrosis in patients with AIH. Furthermore, the expression of EBI3 in liver was positively correlated with patient age, serum IgG levels and serum AST, and was negatively correlated with hemoglobin and albumin. Moreover, our results showed that ratio of MDSC in peripheral blood increased significantly in AIH patients as compared with healthy controls. Further study showed that CD33, a representative marker of MDSCs, co-localized well with gp130 and IL12Rβ2, suggesting MDSCs as target cell for IL-35. Consistently, MDSCs from AIH displayed a substantial higher abundance of gp130 and IL12Rβ2 and were expanded by IL-35 in vitro. IL-35-induced MDSCs showed a significant increase in Nitric oxide (NO) production but not reactive oxygen species (ROS). Conclusions: IL-35 might play an important role in AIH by regulating MDSCs and it could provide new insights into the therapy of AIH.

Activated hepatic stellate cells regulate MDSC migration through the SDF-1/CXCR4 axis in an orthotopic mouse model of hepatocellular carcinoma

Hepatic stellate cells (HSCs) are important stromal cells and pivotal mediators involved in the pathogenesis and immunosuppression of hepatocellular carcinoma (HCC). The liver has been demonstrated to be a site for accumulation of tumor-induced myeloid-derived suppressor cells (MDSCs). We previously reported that HSCs induced an increase in the number of MDSCs in HCC. However, how MDSCs are recruited in HCC remains largely unclear. In the present study, we found that HSC-conditioned medium (HSC-CM) induced bone marrow-derived cell and splenocyte migration, especially MDSC migration. Using chemokine-neutralizing antibodies and chemokine receptor inhibitors, we found that HSCs promoted MDSC migration through the SDF-1/CXCR4 axis. Subsequently, we used an orthotopic mouse liver tumor model to determine how HSCs mediated MDSC migration to HCC in vivo. The in vivo results indicated that pretreatment of MDSCs with a CXCR4 inhibitor or injection with SDF-1-knocked down HSCs inhibited MDSC migration to the spleen and liver of the tumor-bearing mice. Together, our findings indicate a central role for HSCs in MDSC migration mediated by the SDF-1/CXCR4 axis, thus revealing a potentially effective approach for modulating the tumor microenvironment by targeting HSCs in HCC.

Immunobiology of cholangiocarcinoma

Cholangiocarcinoma (CCA) represents a heterogeneous group of epithelial tumours that are classified according to anatomical location as intrahepatic (iCCA), perihilar (pCCA), or distal (dCCA). Although surgical resection and liver transplantation following neoadjuvant therapy are potentially curative options for a subset of patients with early-stage disease, the currently available medical therapies for CCA have limited efficacy. Immunotherapeutic strategies such as immune checkpoint blockade (ICB) harness the host immune system to unleash an effective and durable antitumour response in a subset of patients with a variety of malignancies. However, response to ICB monotherapy has been relatively disappointing in CCA. CCAs are desmoplastic tumours with an abundant tumour immune microenvironment (TIME) that contains immunosuppressive innate immune cells such as tumour-associated macrophages and myeloid-derived suppressor cells. A subset of CCAs may be classified as immune 'hot' tumours with a high density of CD8+ T cells and enhanced expression of immune checkpoint molecules. Immune 'hot' tumour types are associated with higher response rates to ICB. However, the suboptimal response rates to ICB monotherapy in human clinical trials of CCA imply that the preponderance of CCAs are immune 'cold' tumours with a non-T cell infiltrated TIME. An enhanced comprehension of the immunobiology of CCA, particularly the innate immune response to CCA, is essential in the effort to develop effective combination immunotherapeutic strategies that can target a larger subset of CCAs.

The mechanism of the premetastatic niche facilitating colorectal cancer liver metastasis generated from myeloid-derived suppressor cells induced by the S1PR1-STAT3 signaling pathway

The tumor-derived factors involved in the expansion and accumulation of myeloid-derived suppressor cells (MDSCs) in metastatic dissemination of colorectal cancer (CRC) to the liver has not been studied. Immunohistochemistry was used to detect sphingosine-1-phosphate receptor 1 (S1PR1) and signal transducer and activator of transcription-3 (STAT3) in human colorectal tumors. IL-6 and interferon-γ were detected by enzyme-linked immunosorbent assay (ELISA). Tumor growth, invasion, and migration were evaluated by MTT, transwell, and wound healing assays, respectively. Subcutaneous tumor-bearing and CRC liver metastasis (CRLM) nude mouse models were constructed. The percentage of MDSCs was measured using multicolor flow cytometry. Western blot assay was used to evaluate S1PR1 and p-STAT3 expression in MDSCs after separation from the liver and tumor by magnetic antibody. T-cell suppression assay was detected by carboxyfluorescein succinimidyl ester (CFSE). Aberrant co-expressed S1PR1 and p-STAT3 was correlated with metachronous liver metastasis and poor prognosis in CRC. A mutual activation loop between S1PR1 and STAT3 can enhance CRC cell proliferation, migration, and invasion in vitro and in vivo. The expression of p-STAT3 and its downstream proteins can be regulated by S1PR1. p-STAT3 was the dependent signaling pathway of S1PR1 in the promotion of cell growth and liver metastasis in CRC. The level of IL-6 and the associated MDSCs stimulated by the S1PR1-STAT3 correlated with the number of liver metastatic nodes in the CRLM mouse models and patients. Increased CD14⁺HLA-DR^-/low MDSCs from CRLM patients inhibited autologous T-cell proliferation and predict poor prognosis. The S1PR1-STAT3-IL-6-MDSCs axis operates in both tumor cells and MDSCs involved in the promotion of growth and liver metastasis in CRC. MDSCs induced by S1PR1-STAT3 in CRC cells formed the premetastatic niche in the liver can promote organ-specific metastasis.

The disruption of hematopoiesis in tumor progression

Human adult hematopoiesis maintains homeostasis by replacing depleted progeny pools and inducing a primary immune response to infectious diseases and tumors. Recent studies have shown that tumor progression is associated with profound perturbations in hematopoiesis. Scientists have sought to clarify the complex mechanisms underlying the developmental fate of hematopoiesis by assessing hematopoietic stem and progenitor cells in various tumors. Results have shown that tumors disrupt normal hematopoiesis, resulting in extramedullary hematopoiesis and myeloid skewing. The key regulatory roles played by myeloid-derived suppressor cells induce immune suppression. Here, we summarize recent findings and discuss mechanisms underlying the disruption of hematopoiesis in solid tumors.

SUMO-Specific Protease 1 Is Critical for Myeloid-Derived Suppressor Cell Development and Function

Myeloid-derived suppressor cells (MDSC) can suppress immunity and promote tumorigenesis, and their abundance is associated with poor prognosis. In this study, we show that SUMO1/sentrin-specific peptidase 1 (SENP1) regulates the development and function of MDSC. SENP1 deficiency in myeloid cells promoted MDSC expansion in bone marrow, spleen, and other organs. Senp1^-/- MDSC showed stronger immunosuppressive activity than Senp1^+/+ MDSC; we observed no defects in the differentiation of myeloid precursor cell in Senp1^-/- mice. Mechanistically, SENP1-mediated regulation of MDSC was dependent on STAT3 signaling. We identified CD45 as a specific STAT3 phosphatase in MDSC. CD45 was SUMOylated in MDSC and SENP1 could deconjugate SUMOylated CD45. In Senp1^-/- MDSC, CD45 was highly SUMOylated, which reduced its phosphatase activity toward STAT3, leading to STAT3-mediated MDSC development and function. These results reveal a suppressive function of SENP1 in modulating MDSC expansion and function via CD45-STAT3 signaling axis. SIGNIFICANCE: These findings show that increased SUMOylation of CD45 via loss of SENP1 suppresses CD45-mediated dephosphorylation of STAT3, which promotes MDSC development and function, leading to tumorigenesis.

Transcriptomic analysis of hepatocellular carcinoma reveals molecular features of disease progression and tumor immune biology

Hepatocellular carcinoma (HCC) develops in the context of chronic inflammatory liver disease and has an extremely poor prognosis. An immunosuppressive tumor microenvironment may contribute to therapeutic failure in metastatic HCC. Here, we identified unique molecular signatures pertaining to HCC disease progression and tumor immunity by analyzing genome-wide RNA-Seq data derived from HCC patient tumors and non-tumor cirrhotic tissues. Unsupervised clustering of gene expression data revealed a gradual suppression of local tumor immunity that coincided with disease progression, indicating an increasingly immunosuppressive tumor environment during HCC disease advancement. IHC examination of the spatial distribution of CD8+ T cells in tumors revealed distinct intra- and peri-tumoral subsets. Differential gene expression analysis revealed an 85-gene signature that was significantly upregulated in the peri-tumoral CD8+ T cell-excluded tumors. Notably, this signature was highly enriched with components of underlying extracellular matrix, fibrosis, and epithelial-mesenchymal transition (EMT). Further analysis condensed this signature to a core set of 23 genes that are associated with CD8+ T cell localization, and were prospectively validated in an independent cohort of HCC specimens. These findings suggest a potential association between elevated fibrosis, possibly modulated by TGF-β, PDGFR, SHH or Notch pathway, and the T cell-excluded immune phenotype. Indeed, targeting fibrosis using a TGF-β neutralizing antibody in the STAM™ model of murine HCC, we found that ameliorating the fibrotic environment could facilitate redistribution of CD8+ lymphocytes into tumors. Our results provide a strong rationale for utilizing immunotherapies in HCC earlier during treatment, potentially in combination with anti-fibrotic therapies.

Induction of liver-specific intrahepatic myeloid cells aggregation expands CD8 T cell and inhibits growth of murine hepatoma

Toll-Like Receptor 9 (TLR9) stimulation selectively triggers the formation of a cell cluster termed intrahepatic myeloid aggregation for T cell expansion" (iMATE) in a mouse chronic viral hepatitis model. iMATE expands cytotoxic T cells and controls viral hepatitis infection. The liver-specific immune response prompted this investigation of whether the effect could control tumor growth in the murine hepatic tumor model. Murine hepatic BNL cells were used to establish an orthotropic liver tumor model. We found that intravenous infusion of TLR 9 agonist, CpG oligodeoxynucleotide (ODN) induced iMATE formation in non-tumor parts of liver and suppressed the murine BNL tumor growth. The ratio of intra-tumor CD8+ T cells have increased after CpG ODN. These cells expressed higher levels of effector and checkpoint molecules, and produce more Th1 cytokine upon ex vivo stimulation. The CD11b+Ly6ChiLy6G - subset of CD11b+ myeloid cells in the tumor microenvironment has increased. Both CD11b+Ly6ChiLy6G - and CD11b+Ly6CloLy6G+ subsets expressed higher level of interferon-gamma post CpG ODN treatment, although still presented a suppressive phenotype. Their suppressive ability was decreased, instead, the targeted CD8+ T cell proliferation was promoted at a higher dose of CD11b+Ly6ChiLy6G- cells. The phenomenon was further proven in DEN induced liver tumor model. In conclusion, systemic CpG ODN treatment induced iMATE formation that expanded effector CD8+ T cells to control tumor growth in the mouse hepatic tumor model. This novel strategy provides a new rationale for liver-specific tumor immunotherapy.

STAT3 inhibition induces Bax-dependent apoptosis in liver tumor myeloid-derived suppressor cells

Immunosuppressive myeloid-derived suppressor cells (MDSC) subvert antitumor immunity and limit the efficacy of chimeric antigen receptor T cells (CAR-T). Previously, we reported that the GM-CSF/JAK2/STAT3 axis drives liver-associated MDSC (L-MDSC) proliferation and blockade of this axis rescued antitumor immunity. We extended these findings in our murine liver metastasis (LM) model, by treating tumor-bearing mice with STAT3 inhibitors (STATTIC or BBI608) to further our understanding of how STAT3 drives L-MDSC suppressive function. STAT3 inhibition caused significant reduction of tumor burden as well as L-MDSC frequencies due to decrease in pSTAT3 levels. L-MDSC isolated from STATTIC or BBI608-treated mice had significantly reduced suppressive function. STAT3 inhibition of L-MDSC was associated with enhanced antitumor activity of CAR-T. Further investigation demonstrated activation of apoptotic signaling pathways in L-MDSC following STAT3 inhibition as evidenced by an upregulation of the pro-apoptotic proteins Bax, cleaved caspase-3, and downregulation of the anti-apoptotic protein Bcl-2. Accordingly, there was also a decrease of pro-survival markers, pErk and pAkt, and an increase in pro-death marker, Fas, with activation of downstream JNK and p38 MAPK. These findings represent a previously unrecognized link between STAT3 inhibition and Fas-induced apoptosis of MDSCs. Our findings suggest that inhibiting STAT3 has potential clinical application for enhancing the efficacy of CAR-T cells in LM through modulation of L-MDSC.

The Role of Invariant NKT in Autoimmune Liver Disease: Can Vitamin D Act as an Immunomodulator?

Natural killer T (NKT) cells are a distinct lineage of T cells which express both the T cell receptor (TCR) and natural killer (NK) cell markers. Invariant NKT (iNKT) cells bear an invariant TCR and recognize a small variety of glycolipid antigens presented by CD1d (nonclassical MHC-I). CD1d-restricted iNKT cells are regulators of immune responses and produce cytokines that may be proinflammatory (such as interferon-gamma (IFN-γ)) or anti-inflammatory (such as IL-4). iNKT cells also appear to play a role in B cell regulation and antibody production. Alpha-galactosylceramide (α-GalCer), a derivative of the marine sponge, is a potent stimulator of iNKT cells and has been proposed as a therapeutic iNKT cell activator. Invariant NKT cells have been implicated in the development and perpetuation of several autoimmune diseases such as multiple sclerosis and systemic lupus erythematosus (SLE). Animal models of SLE have shown abnormalities in iNKT cells numbers and function, and an inverse correlation between the frequency of NKT cells and IgG levels has also been observed. The role of iNKT cells in autoimmune liver disease (AiLD) has not been extensively studied. This review discusses the current data with regard to iNKT cells function in AiLD, in addition to providing an overview of iNKT cells function in other autoimmune conditions and animal models. We also discuss data regarding the immunomodulatory effects of vitamin D on iNKT cells, which may serve as a potential therapeutic target, given that deficiencies in vitamin D have been reported in various autoimmune disorders.