Suppression of Myeloid Cell Arginase Activity leads to Therapeutic Response in a NSCLC Mouse Model by Activating Anti-Tumor Immunity

Spon1+ inflammatory monocytes promote collagen remodeling and lung cancer metastasis through lipoprotein receptor 8 signaling

Lung cancer is the leading cause of cancer-related deaths in the world, and non-small cell lung cancer (NSCLC) is the most common subset. We previously found that infiltration of tumor inflammatory monocytes (TIMs) into lung squamous carcinoma (LUSC) tumors is associated with increased metastases and poor survival. To further understand how TIMs promote metastases, we compared RNA-Seq profiles of TIMs from several LUSC metastatic models with inflammatory monocytes (IMs) of non-tumor-bearing controls. We identified Spon1 as upregulated in TIMs and found that Spon1 expression in LUSC tumors corresponded with poor survival and enrichment of collagen extracellular matrix signatures. We observed SPON1+ TIMs mediate their effects directly through LRP8 on NSCLC cells, which resulted in TGF-β1 activation and robust production of fibrillar collagens. Using several orthogonal approaches, we demonstrated that SPON1+ TIMs were sufficient to promote NSCLC metastases. Additionally, we found that Spon1 loss in the host, or Lrp8 loss in cancer cells, resulted in a significant decrease of both high-density collagen matrices and metastases. Finally, we confirmed the relevance of the SPON1/LRP8/TGF-β1 axis with collagen production and survival in patients with NSCLC. Taken together, our study describes how SPON1+ TIMs promote collagen remodeling and NSCLC metastases through an LRP8/TGF-β1 signaling axis.

CD200 is overexpressed in the pancreatic tumor microenvironment and predictive of overall survival

Pancreatic cancer is an aggressive disease with a 5 year survival rate of 13%. This poor survival is attributed, in part, to limited and ineffective treatments for patients with metastatic disease, highlighting a need to identify molecular drivers of pancreatic cancer to target for more effective treatment. CD200 is a glycoprotein that interacts with the receptor CD200R and elicits an immunosuppressive response. Overexpression of CD200 has been associated with differential outcomes, depending on the tumor type. In the context of pancreatic cancer, we have previously reported that CD200 is expressed in the pancreatic tumor microenvironment (TME), and that targeting CD200 in murine tumor models reduces tumor burden. We hypothesized that CD200 is overexpressed on tumor and stromal populations in the pancreatic TME and that circulating levels of soluble CD200 (sCD200) have prognostic value for overall survival. We discovered that CD200 was overexpressed on immune, stromal, and tumor populations in the pancreatic TME. Particularly, single-cell RNA-sequencing indicated that CD200 was upregulated on inflammatory cancer-associated fibroblasts. Cytometry by time of flight analysis of PBMCs indicated that CD200 was overexpressed on innate immune populations, including monocytes, dendritic cells, and monocytic myeloid-derived suppressor cells. High sCD200 levels in plasma correlated with significantly worse overall and progression-free survival. Additionally, sCD200 correlated with the ratio of circulating matrix metalloproteinase (MMP) 3: tissue inhibitor of metalloproteinase (TIMP) 3 and MMP11/TIMP3. This study highlights the importance of CD200 expression in pancreatic cancer and provides the rationale for designing novel therapeutic strategies that target this protein.

Myeloid-derived suppressor cells in cancer: therapeutic targets to overcome tumor immune evasion

Paradoxically, tumor development and progression can be inhibited and promoted by the immune system. After three stages of immune editing, namely, elimination, homeostasis and escape, tumor cells are no longer restricted by immune surveillance and thus develop into clinical tumors. The mechanisms of immune escape include abnormalities in antitumor-associated immune cells, selection for immune resistance to tumor cells, impaired transport of T cells, and the formation of an immunosuppressive tumor microenvironment. A population of distinct immature myeloid cells, myeloid-derived suppressor cells (MDSCs), mediate immune escape primarily by exerting immunosuppressive effects and participating in the constitution of an immunosuppressive microtumor environment. Clinical trials have found that the levels of MDSCs in the peripheral blood of cancer patients are strongly correlated with tumor stage, metastasis and prognosis. Moreover, animal experiments have confirmed that elimination of MDSCs inhibits tumor growth and metastasis to some extent. Therefore, MDSCs may become the target of immunotherapy for many cancers, and eliminating MDSCs can help improve the response rate to cancer treatment and patient survival. However, a clear definition of MDSCs and the specific mechanism involved in immune escape are lacking. In this paper, we review the role of the MDSCs population in tumor development and the mechanisms involved in immune escape in different tumor contexts. In addition, we discuss the use of these cells as targets for tumor immunotherapy. This review not only contributes to a systematic and comprehensive understanding of the essential role of MDSCs in immune system reactions against tumors but also provides information to guide the development of cancer therapies targeting MDSCs.

Cancer immunometabolism: advent, challenges, and perspective

For decades, great strides have been made in the field of immunometabolism. A plethora of evidence ranging from basic mechanisms to clinical transformation has gradually embarked on immunometabolism to the center stage of innate and adaptive immunomodulation. Given this, we focus on changes in immunometabolism, a converging series of biochemical events that alters immune cell function, propose the immune roles played by diversified metabolic derivatives and enzymes, emphasize the key metabolism-related checkpoints in distinct immune cell types, and discuss the ongoing and upcoming realities of clinical treatment. It is expected that future research will reduce the current limitations of immunotherapy and provide a positive hand in immune responses to exert a broader therapeutic role.

Polyamine-mediated ferroptosis amplification acts as a targetable vulnerability in cancer

Targeting ferroptosis, an iron-dependent form of regulated cell death triggered by the lethal overload of lipid peroxides, in cancer therapy is impeded by our limited understanding of the intersection of tumour's metabolic feature and ferroptosis vulnerability. In the present study, arginine is identified as a ferroptotic promoter using a metabolites library. This effect is mainly achieved through arginine's conversion to polyamines, which exerts their potent ferroptosis-promoting property in an H2O2-dependent manner. Notably, the expression of ornithine decarboxylase 1 (ODC1), the critical enzyme catalysing polyamine synthesis, is significantly activated by the ferroptosis signal--iron overload--through WNT/MYC signalling, as well as the subsequent elevated polyamine synthesis, thus forming a ferroptosis-iron overload-WNT/MYC-ODC1-polyamine-H2O2 positive feedback loop that amplifies ferroptosis. Meanwhile, we notice that ferroptotic cells release enhanced polyamine-containing extracellular vesicles into the microenvironment, thereby further sensitizing neighbouring cells to ferroptosis and accelerating the "spread" of ferroptosis in the tumour region. Besides, polyamine supplementation also sensitizes cancer cells or xenograft tumours to radiotherapy or chemotherapy through inducing ferroptosis. Considering that cancer cells are often characterized by elevated intracellular polyamine pools, our results indicate that polyamine metabolism exposes a targetable vulnerability to ferroptosis and represents an exciting opportunity for therapeutic strategies for cancer.

Melatonin modulates L-arginine metabolism in tumor-associated macrophages by targeting arginase 1 in lymphoma

L-Arginine metabolism plays a crucial role in determining the M1/M2 polarization of macrophages. The M1 macrophages express inducible nitric oxide synthase (iNOS), while the M2 macrophages express arginase 1 and metabolize arginine into nitric oxide and urea, respectively. The tumor microenvironment promotes M2 macrophage polarization and consequently switches the metabolic fate of arginine from nitric oxide towards urea production. Importantly, infiltration of M2 macrophages or tumor-associated macrophages (TAMs) has been correlated with poor prognosis of various cancer types. Melatonin is well reported to have antitumor and immunomodulatory properties. However, whether and how it impacts the polarization of TAMs has not been elucidated. Considering the crucial role of arginine metabolism in macrophage polarization, we were interested to know the fate of L-arginine in TAMs and whether it can be reinstated by melatonin or not. We used a murine model of Dalton's lymphoma and established an in vitro model of TAMs. For TAMs, we used the ascitic fluid of tumor-bearing hosts to activate the macrophages in the presence and absence of lipopolysaccharide (LPS). In these groups, L-arginine metabolism was evaluated, and then the effect of melatonin was assessed in these groups, wherein the metabolic fate of arginine as well as the expression of iNOS and arginase 1 were checked. Furthermore, in the in vivo system of the tumor-bearing host, the effect of melatonin was assessed. The in vitro model of TAMs showed a Th2 cytokine profile, reduced phagocytic activity, and increased wound healing ability. Upon investigating arginine metabolism, we observed high urea levels with increased activity and expression of arginase 1 in TAMs. Furthermore, we observed reduced levels of LPS-induced nitric oxide in TAMs; however, their iNOS expression was comparable. With melatonin treatment, urea level decreased significantly, while the reduction in nitric oxide level was not as significant as observed in its absence in TAMs. Also, melatonin significantly reduced arginase activity and expression at the transcriptional and translational levels, while iNOS expression was affected only at the translational level. This effect was further investigated in the in vivo system, wherein melatonin treatment reversed the metabolic fate of arginine, from urea towards nitric oxide, within the tumor microenvironment. This effect was further correlated with pro-apoptotic tumor cell death in the in vivo system. Our results reinforced the immunomodulatory role of melatonin and offered a strong prospect for activating the anti-tumor immune response in cancer conditions.

Recurrence risk stratification of hepatocellular carcinomas based on immune gene expression and features extracted from pathological images

BACKGROUND

Immune-based therapy is a promising type of treatment for hepatocellular carcinoma (HCC) but has only been partially successful due to the high heterogeneity in HCC tumor. The differences in the degree of tumor cell progression and in the activity of tumor immune microenvironment could lead to varied clinical outcome. Accurate subgrouping for recurrence risk is an approach to address the issue of such heterogeneity. It remains under investigation as whether integrating quantitative whole slide image (WSI) features with the expression profile of immune marker genes can improve the risk stratification, and whether clinical outcome prediction can assist in understanding molecular biology that drives the outcome.

METHODS

We included a total of 231 patients from the Cancer Genome Atlas Liver Hepatocellular Carcinoma (TCGA-LIHC) project. For each patient, we extracted 18 statistical metrics corresponding to a global region of interest and 135 features regarding nucleus shape from WSI. A risk score was developed using these image features with high-dimensional survival modeling. We also introduced into the model the expression profile of 66 representative marker genes relevant to currently available immunotherapies. We stratified all patients into higher and lower-risk subgroup based on the final risk score selected from multiple models generated, and further investigated underlying molecular mechanisms associated with the risk stratification.

RESULTS

One WSI feature and three immune marker genes were selected into the final recurrence-free survival (RFS) prediction model following the best integrated modeling framework. The resultant score showed a significantly improved prediction performance on the test dataset (mean time-dependent AUCs = 0.707) as compared to those of other types (e.g: mean time-dependent AUCs of AJCC tumor stage = 0.525) of input data integration. To assess that the risk score could provide a higher-resolution risk stratification, a lower-risk subgroup (or a higher-risk subgroup) was arbitrarily assigned according to score falling below (or above) the median score. The lower risk subgroup had significantly longer median RFS time than that of the higher-risk patients (median RFS = 903 vs. 265 days, log-rank test p-value< 0.0001). Additionally, the higher-risk subgroup, in contrast to the lower-risk patients were characterized with a significant downregulation of immune checkpoint genes, suppressive signal in tumor immune response pathways, and depletion of CD8 T cells. These observations for the higher-risk subgroup suggest that new targets for adoptive or checkpoint-based combined systemic therapies may be useful.

CONCLUSION

We developed a novel prognostic model to predict RFS for HCC patients, using one feature that can be automatically extracted from routine histopathological images, as well as the expression profiles of three immune marker genes. The methodology used in this paper demonstrates the feasibility of developing prognostic models that provide both useful risk stratification along with valuable biological insights into the underlying characteristics of the subgroups identified.

Ginseng-derived nanoparticles reprogram macrophages to regulate arginase-1 release for ameliorating T cell exhaustion in tumor microenvironment

BACKGROUND

Lines of evidence indicated that, immune checkpoints (ICs) inhibitors enhanced T cell immune response to exert anti-tumor effects. However, T cell exhaustion has been so far a major obstacle to antitumor immunotherapy in colorectal cancer patients. Our previous studies showed that ginseng-derived nanoparticles (GDNPs) inhibited the growth of various tumors by reprograming tumor-associated macrophages (TAMs) and downregulated the ICs expression on T cells in tumor microenvironment (TME), but the underlying effector mechanisms remained unclear.

METHODS

The correlation between arginase-1 (ARG1) and T cells was computed based on the colorectal cancer patients in TCGA database. In vitro, we observed that GDNPs reprogrammed TAMs inhibited ARG1 release and ultimately ameliorated T cell exhaustion according to several techniques including WB, PCR, ELISA and flow cytometry. We also used an in vivo MC38 tumor-bearing model and administered GDNPs to assess their anti-tumor effects through multiple indices. The mechanism that GDNPs improved T cell exhaustion was further clarified using the bioinformatics tools and flow cytometry.

RESULTS

GDNPs reprogramed TAMs via reducing ARG1 production. Moreover, normalized arginine metabolism ameliorated T cell exhaustion through mTOR-T-bet axis, resulting in reduced ICs expression and enhanced CD8+ T cells expansion.

CONCLUSIONS

By regulating the mTOR-T-bet axis, GDNPs reprogramed macrophages to regulate ARG1 release, which further ameliorated T cell exhaustion in TME. These findings provided new insights into comprehending the mechanisms underlying the mitigation of T cell exhaustion, which may facilitate the development of innovative therapeutic strategies in the field of cancer treatment.

Discovery of a new marker to identify myeloid cells associated with metastatic breast tumours

BACKGROUND

Myeloid cells play an essential role in cancer metastasis. The phenotypic diversity of these cells during cancer development has attracted great interest; however, their functional heterogeneity and plasticity have limited their role as prognostic markers and therapeutic targets.

METHODS

To identify markers associated with myeloid cells in metastatic tumours, we compared transcriptomic data from immune cells sorted from metastatic and non-metastatic mammary tumours grown in BALB/cJ mice. To assess the translational relevance of our in vivo findings, we assessed human breast cancer biopsies and evaluated the association between arginase 1 protein expression in breast cancer tissues with tumour characteristics and patient outcomes.

RESULTS

Among the differentially expressed genes, arginase 1 (ARG1) showed a unique expression pattern in tumour-infiltrating myeloid cells that correlated with the metastatic capacity of the tumour. Even though ARG1-positive cells were found almost exclusively inside the metastatic tumour, ARG1 protein was also present in the plasma. In human breast cancer biopsies, the presence of ARG1-positive cells was strongly correlated with high-grade proliferating tumours, poor prognosis, and low survival.

CONCLUSION

Our findings highlight the potential use of ARG1-positive myeloid cells as an independent prognostic marker to evaluate the risk of metastasis in breast cancer patients.

Advancing Understanding of Non-Small Cell Lung Cancer with Multiplexed Antibody-Based Spatial Imaging Technologies

Non-small cell lung cancer (NSCLC) remains a cause of significant morbidity and mortality, despite significant advances made in its treatment using immune checkpoint inhibitors (ICIs) over the last decade; while a minority experience prolonged responses with ICIs, benefit is limited for most patients. The development of multiplexed antibody-based (MAB) spatial tissue imaging technologies has revolutionised analysis of the tumour microenvironment (TME), enabling identification of a wide range of cell types and subtypes, and analysis of the spatial relationships and interactions between them. Such study has the potential to translate into a greater understanding of treatment susceptibility and resistance, factors influencing prognosis and recurrence risk, and identification of novel therapeutic approaches and rational treatment combinations to improve patient outcomes in the clinic. Herein we review studies that have leveraged MAB technologies to deliver novel insights into the TME of NSCLC.

Sex disparities in non-small cell lung cancer: mechanistic insights from a cRaf transgenic disease model

BACKGROUND

Women are at greater risk of developing non-small cell lung cancer (NSCLC), yet the underlying causes remain unclear.

METHODS

We performed whole genome scans in lung tumours of cRaf transgenic mice and identified miRNA, transcription factor and hormone receptor dependent gene regulations. We confirmed hormone receptors by immunohistochemistry and constructed regulatory gene networks by considering experimentally validated miRNA-gene and transcription factor-miRNA/gene targets. Bioinformatics, genomic foot-printing and gene enrichment analysis established sex-specific circuits of lung tumour growth. Translational research involved a large cohort of NSCLC patients. We evaluated commonalities in sex-specific NSCLC gene regulations between mice and humans and determined their prognostic value in Kaplan-Meier survival statistics and COX proportional hazard regression analysis.

FINDINGS

Overexpression of the cRaf kinase elicited an extraordinary 8-fold increase in tumour growth among females, and nearly 70% of the 112 differentially expressed genes (DEGs) were female specific. We identified oncogenes, oncomirs, tumour suppressors, cell cycle regulators and MAPK/EGFR signalling molecules, which prompted sex-based differences in NSCLC, and we deciphered a regulatory gene-network, which protected males from accelerated tumour growth. Strikingly, 41% of DEGs are targets of hormone receptors, and the majority (85%) are oestrogen receptor (ER) dependent. We confirmed the role of ER in a large cohort of NSCLC patients and validated 40% of DEGs induced by cRaf in clinical tumour samples.

INTERPRETATION

We report the molecular wiring that prompted sex disparities in tumour growth. This allowed us to propose the development of molecular targeted therapies by jointly blocking ER, CDK1 and arginase 2 in NSCLC.

FUNDING

We gratefully acknowledge the financial support of the Lower Saxony Ministry of Culture and Sciences and Volkswagen Foundation, Germany to JB (25A.5-7251-99-3/00) and of the Chinese Scholarship Council to SZ (202008080022). This publication is funded by the Deutsche Forschungsgemeinschaft (DFG) as part of the "Open Access Publikationskosten" program.

Genetics of enzymatic dysfunctions in metabolic disorders and cancer

Inherited metabolic disorders arise from mutations in genes involved in the biogenesis, assembly, or activity of metabolic enzymes, leading to enzymatic deficiency and severe metabolic impairments. Metabolic enzymes are essential for the normal functioning of cells and are involved in the production of amino acids, fatty acids and nucleotides, which are essential for cell growth, division and survival. When the activity of metabolic enzymes is disrupted due to mutations or changes in expression levels, it can result in various metabolic disorders that have also been linked to cancer development. However, there remains much to learn regarding the relationship between the dysregulation of metabolic enzymes and metabolic adaptations in cancer cells. In this review, we explore how dysregulated metabolism due to the alteration or change of metabolic enzymes in cancer cells plays a crucial role in tumor development, progression, metastasis and drug resistance. In addition, these changes in metabolism provide cancer cells with a number of advantages, including increased proliferation, resistance to apoptosis and the ability to evade the immune system. The tumor microenvironment, genetic context, and different signaling pathways further influence this interplay between cancer and metabolism. This review aims to explore how the dysregulation of metabolic enzymes in specific pathways, including the urea cycle, glycogen storage, lysosome storage, fatty acid oxidation, and mitochondrial respiration, contributes to the development of metabolic disorders and cancer. Additionally, the review seeks to shed light on why these enzymes represent crucial potential therapeutic targets and biomarkers in various cancer types.

Field-Deployable Treatments For Leishmaniasis: Intrinsic Challenges, Recent Developments and Next Steps

Leishmaniasis is a neglected tropical disease endemic primarily to low- and middle-income countries, for which there has been inadequate development of affordable, safe, and efficacious therapies. Clinical manifestations of leishmaniasis range from self-healing skin lesions to lethal visceral infection with chances of relapse. Although treatments are available, secondary effects limit their use outside the clinic and negatively impact the quality of life of patients in endemic areas. Other non-medicinal treatments, such as thermotherapies, are limited to use in patients with cutaneous leishmaniasis but not with visceral infection. Recent studies shed light to mechanisms through which Leishmania can persist by hiding in cellular safe havens, even after chemotherapies. This review focuses on exploring the cellular niches that Leishmania parasites may be leveraging to persist within the host. Also, the cellular, metabolic, and molecular implications of Leishmania infection and how those could be targeted for therapeutic purposes are discussed. Other therapies, such as those developed against cancer or for manipulation of the ferroptosis pathway, are proposed as possible treatments against leishmaniasis due to their mechanisms of action. In particular, treatments that target hematopoietic stem cells and monocytes, which have recently been found to be necessary components to sustain the infection and provide a safe niche for the parasites are discussed in this review as potential field-deployable treatments against leishmaniasis.

Tumor-intrinsic LKB1-LIF signaling axis establishes a myeloid niche to promote immune evasion and tumor growth

Tumor mutations can influence the surrounding microenvironment leading to suppression of anti-tumor immune responses and thereby contributing to tumor progression and failure of cancer therapies. Here we use genetically engineered lung cancer mouse models and patient samples to dissect how LKB1 mutations accelerate tumor growth by reshaping the immune microenvironment. Comprehensive immune profiling of LKB1 -mutant vs wildtype tumors revealed dramatic changes in myeloid cells, specifically enrichment of Arg1 ⁺ interstitial macrophages and SiglecF ^Hi neutrophils. We discovered a novel mechanism whereby autocrine LIF signaling in Lkb1 -mutant tumors drives tumorigenesis by reprogramming myeloid cells in the immune microenvironment. Inhibiting LIF signaling in Lkb1 -mutant tumors, via gene targeting or with a neutralizing antibody, resulted in a striking reduction in Arg1 ⁺ interstitial macrophages and SiglecF ^Hi neutrophils, expansion of antigen specific T cells, and inhibition of tumor progression. Thus, targeting LIF signaling provides a new therapeutic approach to reverse the immunosuppressive microenvironment of LKB1 -mutant tumors.

Amino acid metabolism in immune cells: essential regulators of the effector functions, and promising opportunities to enhance cancer immunotherapy

Amino acids are basic nutrients for immune cells during organ development, tissue homeostasis, and the immune response. Regarding metabolic reprogramming in the tumor microenvironment, dysregulation of amino acid consumption in immune cells is an important underlying mechanism leading to impaired anti-tumor immunity. Emerging studies have revealed that altered amino acid metabolism is tightly linked to tumor outgrowth, metastasis, and therapeutic resistance through governing the fate of various immune cells. During these processes, the concentration of free amino acids, their membrane bound transporters, key metabolic enzymes, and sensors such as mTOR and GCN2 play critical roles in controlling immune cell differentiation and function. As such, anti-cancer immune responses could be enhanced by supplement of specific essential amino acids, or targeting the metabolic enzymes or their sensors, thereby developing novel adjuvant immune therapeutic modalities. To further dissect metabolic regulation of anti-tumor immunity, this review summarizes the regulatory mechanisms governing reprogramming of amino acid metabolism and their effects on the phenotypes and functions of tumor-infiltrating immune cells to propose novel approaches that could be exploited to rewire amino acid metabolism and enhance cancer immunotherapy.

Pancreatic tumors exhibit myeloid-driven amino acid stress and upregulate arginine biosynthesis

Nutrient stress in the tumor microenvironment requires cancer cells to adopt adaptive metabolic programs for survival and proliferation. Therefore, knowledge of microenvironmental nutrient levels and how cancer cells cope with such nutrition is critical to understand the metabolism underpinning cancer cell biology. Previously, we performed quantitative metabolomics of the interstitial fluid (the local perfusate) of murine pancreatic ductal adenocarcinoma (PDAC) tumors to comprehensively characterize nutrient availability in the microenvironment of these tumors. Here, we develop Tumor Interstitial Fluid Medium (TIFM), a cell culture medium that contains nutrient levels representative of the PDAC microenvironment, enabling us to study PDAC metabolism ex vivo under physiological nutrient conditions. We show that PDAC cells cultured in TIFM adopt a cellular state closer to that of PDAC cells present in tumors compared to standard culture models. Further, using the TIFM model, we found arginine biosynthesis is active in PDAC and allows PDAC cells to maintain levels of this amino acid despite microenvironmental arginine depletion. We also show that myeloid derived arginase activity is largely responsible for the low levels of arginine in PDAC tumors. Altogether, these data indicate that nutrient availability in tumors is an important determinant of cancer cell metabolism and behavior, and cell culture models that incorporate physiological nutrient availability have improved fidelity to in vivo systems and enable the discovery of novel cancer metabolic phenotypes.

Therapeutic targeting of tumour myeloid cells

Myeloid cells are pivotal within the immunosuppressive tumour microenvironment. The accumulation of tumour-modified myeloid cells derived from monocytes or neutrophils - termed 'myeloid-derived suppressor cells' - and tumour-associated macrophages is associated with poor outcome and resistance to treatments such as chemotherapy and immune checkpoint inhibitors. Unfortunately, there has been little success in large-scale clinical trials of myeloid cell modulators, and only a few distinct strategies have been used to target suppressive myeloid cells clinically so far. Preclinical and translational studies have now elucidated specific functions for different myeloid cell subpopulations within the tumour microenvironment, revealing context-specific roles of different myeloid cell populations in disease progression and influencing response to therapy. To improve the success of myeloid cell-targeted therapies, it will be important to target tumour types and patient subsets in which myeloid cells represent the dominant driver of therapy resistance, as well as to determine the most efficacious treatment regimens and combination partners. This Review discusses what we can learn from work with the first generation of myeloid modulators and highlights recent developments in modelling context-specific roles for different myeloid cell subtypes, which can ultimately inform how to drive more successful clinical trials.

Arginase 1 is a key driver of immune suppression in pancreatic cancer

An extensive fibroinflammatory stroma rich in macrophages is a hallmark of pancreatic cancer. In this disease, it is well appreciated that macrophages are immunosuppressive and contribute to the poor response to immunotherapy; however, the mechanisms of immune suppression are complex and not fully understood. Immunosuppressive macrophages are classically defined by the expression of the enzyme Arginase 1 (ARG1), which we demonstrated is potently expressed in pancreatic tumor-associated macrophages from both human patients and mouse models. While routinely used as a polarization marker, ARG1 also catabolizes arginine, an amino acid required for T cell activation and proliferation. To investigate this metabolic function, we used a genetic and a pharmacologic approach to target Arg1 in pancreatic cancer. Genetic inactivation of Arg1 in macrophages, using a dual recombinase genetically engineered mouse model of pancreatic cancer, delayed formation of invasive disease, while increasing CD8+ T cell infiltration. Additionally, Arg1 deletion induced compensatory mechanisms, including Arg1 overexpression in epithelial cells, namely Tuft cells, and Arg2 overexpression in a subset of macrophages. To overcome these compensatory mechanisms, we used a pharmacological approach to inhibit arginase. Treatment of established tumors with the arginase inhibitor CB-1158 exhibited further increased CD8+ T cell infiltration, beyond that seen with the macrophage-specific knockout, and sensitized the tumors to anti-PD1 immune checkpoint blockade. Our data demonstrate that Arg1 drives immune suppression in pancreatic cancer by depleting arginine and inhibiting T cell activation.

[Advances of Immunotherapy Resistance and Coping Strategies in Non-small Cell Lung Cancer]

Immunotherapy has significantly improved clinical outcomes of non-small cell lung cancer (NSCLC), however, along with the popularization of immunotherapy, immune resistance has become an unavoidable problem. Immunotherapy can induce extensive cellular and molecular alterations in the tumor microenvironment. Considering the mechanisms of immune resistance are not yet fully understood and the efficacy of standard chemotherapy regimens is limited, more effective coping strategies based on resistance mechanisms are urgently needed. In this review, we intend to summarize the known mechanisms of immune resistance and feasible strategies, so as to provide a foundation for clinicians to develop more individualized and precise regimens and finally improve patients' prognosis.
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In-silico studies to recognize repurposing therapeutics toward arginase-I inhibitors as a potential onco-immunomodulators

Rudolf Virchow was the first person to point out the important link between immune function and cancer. He did this by noticing that leukocytes were often found in tumors. Overexpression of arginase 1 (ARG1) and inducible nitric oxide synthase (iNOS) in myeloid-derived suppressor cells (MDSCs) and tumour-associated macrophages (TAMs) depletes both intracellular and extracellular arginine. TCR signalling is slowed as a result, and the same types of cells produce reactive oxygen and nitrogen species (ROS and RNS), which aggravates the situation. Human arginase I is a double-stranded manganese metalloenzyme that helps L-arginine break down into L-ornithine and urea. Thus, a quantitative structure-activity relationship (QSAR) analysis was performed to unearth the unrecognised structural aspects crucial for arginase-I inhibition. In this work, a balanced QSAR model with good prediction performance and clear mechanistic interpretation was developed using a dataset of 149 molecules encompassing a broad range of structural scaffolds and compositions. The model was made to meet OECD standards, and all of its validation parameters have values that are higher than the minimum requirements (R² _tr = 0.89, Q² _LMO = 0.86, and R² _ex = 0.85). The present QSAR study linked structural factors to arginase-I inhibitory action, including the proximity of lipophilic atoms to the molecule's centre of mass (within 3A), the position of the donor to the ring nitrogen (exactly 3 bonds away), and the surface area ratio. As OAT-1746 and two others are the only arginase-I inhibitors in development at the time, we have performed a QSAR-based virtual screening with 1650 FDA compounds taken from the zinc database. In this screening, 112 potential hit compounds were found to have a PIC50 value of less than 10 nm against the arginase-I receptor. The created QSAR model's application domain was evaluated in relation to the most active hit molecules identified using QSAR-based virtual screening, utilising a training set of 149 compounds and a prediction set of 112 hit molecules. As shown in the Williams plot, the top hit molecule, ZINC000252286875, has a low leverage value of HAT i/i h* = 0.140, placing it towards the boundary of the usable range. Furthermore, one of 112 hit molecules with a docking score of -10.891 kcal/mol (_PIC₅₀ = 10.023 M) was isolated from a study of arginase-I using molecular docking. Protonated ZINC000252286875-linked arginase-1 showed 2.9 RMSD, whereas non-protonated had 1.8. RMSD plots illustrate protein stability in protonated and non-protonated ZINC000252286875-bound states. Protonated-ZINC000252286875-bound proteins contain 25 Rg. The non-protonated protein-ligand combination exhibits a 25.2-Rg, indicating compactness. Protonated and non-protonated ZINC000252286875 stabilised protein targets in binding cavities posthumously. Significant root mean square fluctuations (RMSF) were seen in the arginase-1 protein at a small number of residues for a time function of 500 ns in both the protonated and unprotonated states. Protonated and non-protonated ligands interacted with proteins throughout the simulation. ZINC000252286875 bound Lys64, Asp124, Ala171, Arg222, Asp232, and Gly250. Aspartic acid residue 232 exhibited 200% ionic contact. 500-ns simulations-maintained ions. Salt bridges for ZINC000252286875 aided docking. ZINC000252286875 created six ionic bonds with Lys68, Asp117, His126, Ala171, Lys224, and Asp232 residues. Asp117, His126, and Lys224 showed 200% ionic interactions. In protonated and deprotonated states, GbindvdW, GbindLipo, and GbindCoulomb energies played crucial role. Moreover, ZINC000252286875 meets all of the ADMET standards to serve as a drug. As a result, the current analyses were successful in locating a novel and potent hit molecule that inhibits arginase-I effectively at nanomolar concentrations. The results of this investigation can be used to develop brand-new arginase I inhibitors as an alternative immune-modulating cancer therapy.

Phenotypic characterization of spatial immune infiltration niches in non-small cell lung cancer

The immune microenvironment of non-small cell lung cancer (NSCLC) is heterogeneous, which impedes the prediction of response to immune checkpoint inhibitors. We have mapped the expression of 49 proteins to spatial immune niches in 33 NSCLC tumors and report key differences in phenotype and function associated with the spatial context of immune infiltration. Tumor-infiltrating leukocytes (TIL), identified in 42% of tumors, had a similar proportion of lymphocyte antigens compared to stromal leukocytes (SL) but displayed significantly higher levels of functional, mainly immune suppressive, markers including PD-L1, PD-L2, CTLA-4, B7-H3, OX40L, and IDO1. In contrast, SL expressed higher levels of the targetable T-cell activation marker CD27, which increased with a longer distance to the tumor. Correlation analysis confirmed that metabolic-driven immune regulatory mechanisms, including ARG1 and IDO1, are present in the TIL. Tertiary lymphoid structures (TLS) were identified in 30% of patients. They displayed less variation in the expression profile and with significantly higher levels of pan lymphocyte and activation markers, dendritic cells, and antigen presentation compared to other immune niches. TLS also had higher CTLA-4 expression than non-structured SL, which may indicate immune dysfunction. Neither the presence of TIL nor TLS was associated with improved clinical outcomes. The apparent discrimination in functional profiles of distinct immune niches, independent of the overall level of leukocytes, illustrates the importance of spatial profiling to deconvolute how the immune microenvironment can dictate a therapeutic response and to identify biomarkers in the context of immunomodulatory treatment.

Annexin A2/TLR2/MYD88 pathway induces arginase 1 expression in tumor-associated neutrophils

Myeloid lineage cells suppress T cell viability through arginine depletion via arginase 1 (ARG1). Despite numerous studies exploring the mechanisms by which ARG1 perturbs lymphocyte function, the cellular populations responsible for its generation and release remain poorly understood. Here, we showed that neutrophil lineage cells and not monocytes or macrophages expressed ARG1 in human non-small cell lung cancer (NSCLC). Importantly, we showed that approximately 40% of tumor-associated neutrophils (TANs) actively transcribed ARG1 mRNA. To determine the mechanism by which ARG1 mRNA is induced in TANs, we utilized FPLC followed by MS/MS to screen tumor-derived factors capable of inducing ARG1 mRNA expression in neutrophils. These studies identified ANXA2 as the major driver of ARG1 mRNA expression in TANs. Mechanistically, ANXA2 signaled through the TLR2/MYD88 axis in neutrophils to induce ARG1 mRNA expression. The current study describes what we believe to be a novel mechanism by which ARG1 mRNA expression is regulated in neutrophils in cancer and highlights the central role that neutrophil lineage cells play in the suppression of tumor-infiltrating lymphocytes.

High Neutrophil-to-Lymphocyte Ratio Facilitates Cancer Growth-Currently Marketed Drugs Tadalafil, Isotretinoin, Colchicine, and Omega-3 to Reduce It: The TICO Regimen

Simple Summary

Several elements that are composed of, or related to, neutrophils, have been shown to inhibit strong immune responses to cancer and promote cancers’ growth. This paper presents the collected data showing these elements and how their coordinated actions as an ensemble facilitate growth in the common cancers. The paper goes on to present a drug regimen, TICO, designed to reduce the cancer growth enhancing effects of the neutrophil related elements. TICO uses four already marketed, readily available generic drugs, repurposed to inhibit neutrophil centered growth facilitation of cancer.

Abstract

This paper presents remarkably uniform data showing that higher NLR is a robust prognostic indicator of shorter overall survival across the common metastatic cancers. Myeloid derived suppressor cells, the NLRP3 inflammasome, neutrophil extracellular traps, and absolute neutrophil count tend to all be directly related to the NLR. They, individually and as an ensemble, contribute to cancer growth and metastasis. The multidrug regimen presented in this paper, TICO, was designed to decrease the NLR with potential to also reduce the other neutrophil related elements favoring malignant growth. TICO is comprised of already marketed generic drugs: the phosphodiesterase 5 inhibitor tadalafil, used to treat inadequate erections; isotretinoin, the retinoid used for acne treatment; colchicine, a standard gout (podagra) treatment; and the common fish oil supplement omega-3 polyunsaturated fatty acids. These individually impose low side effect burdens. The drugs of TICO are old, cheap, well known, and available worldwide. They all have evidence of lowering the NLR or the growth contributing elements related to the NLR when clinically used in general medicine as reviewed in this paper.

Emerging roles for IL-25 and IL-33 in colorectal cancer tumorigenesis

Colorectal cancer (CRC) is the second leading cause of cancer-related death worldwide, and is largely refractory to current immunotherapeutic interventions. The lack of efficacy of existing cancer immunotherapies in CRC reflects the complex nature of the unique intestinal immune environment, which serves to maintain barrier integrity against pathogens and harmful environmental stimuli while sustaining host-microbe symbiosis during homeostasis. With their expression by barrier epithelial cells, the cytokines interleukin-25 (IL-25) and IL-33 play key roles in intestinal immune responses, and have been associated with inappropriate allergic reactions, autoimmune diseases and cancer pathology. Studies in the past decade have begun to uncover the important roles of IL-25 and IL-33 in shaping the CRC tumour immune microenvironment, where they may promote or inhibit tumorigenesis depending on the specific CRC subtype. Notably, both IL-25 and IL-33 have been shown to act on group 2 innate lymphoid cells (ILC2s), but can also stimulate an array of other innate and adaptive immune cell types. Though sometimes their functions can overlap they can also produce distinct phenotypes dependent on the differential distribution of their receptor expression. Furthermore, both IL-25 and IL-33 modulate pathways previously known to contribute to CRC tumorigenesis, including angiogenesis, tumour stemness, invasion and metastasis. Here, we review our current understanding of IL-25 and IL-33 in CRC tumorigenesis, with specific focus on dissecting their individual function in the context of distinct subtypes of CRC, and the potential prospects for targeting these pathways in CRC immunotherapy.

Arginine Deprivation in SCLC: Mechanisms and Perspectives for Therapy

Arginine deprivation has gained increasing traction as a novel and safe antimetabolite strategy for the treatment of several hard-to-treat cancers characterised by a critical dependency on arginine. Small cell lung cancer (SCLC) displays marked arginine auxotrophy due to inactivation of the rate-limiting enzyme argininosuccinate synthetase 1 (ASS1), and as a consequence may be targeted with pegylated arginine deiminase or ADI-PEG20 (pegargiminase) and human recombinant pegylated arginases (rhArgPEG, BCT-100 and pegzilarginase). Although preclinical studies reveal that ASS1-deficient SCLC cell lines are highly sensitive to arginine-degrading enzymes, there is a clear disconnect with the clinic with minimal activity seen to date that may be due in part to patient selection. Recent studies have explored resistance mechanisms to arginine depletion focusing on tumor adaptation, such as ASS1 re-expression and autophagy, stromal cell inputs including macrophage infiltration, and tumor heterogeneity. Here, we explore how arginine deprivation may be combined strategically with novel agents to improve SCLC management by modulating resistance and increasing the efficacy of existing agents. Moreover, recent work has identified an intriguing role for targeting arginine in combination with PD-1/PD-L1 immune checkpoint inhibitors and clinical trials are in progress. Thus, future studies of arginine-depleting agents with chemoimmunotherapy, the current standard of care for SCLC, may lead to enhanced disease control and much needed improvements in long-term survival for patients.

Tumor accomplice: T cell exhaustion induced by chronic inflammation

The development and response to treatment of tumor are modulated by inflammation, and chronic inflammation promotes tumor progression and therapy resistance. This article summarizes the dynamic evolution of inflammation from acute to chronic in the process of tumor development, and its effect on T cells from activation to the promotion of exhaustion. We review the mechanisms by which inflammatory cells and inflammatory cytokines regulate T cell exhaustion and methods for targeting chronic inflammation to improve the efficacy of immunotherapy. It is great significance to refer to the specific state of inflammation and T cells at different stages of tumor development for accurate clinical decision-making of immunotherapy and improving the efficiency of tumor immunotherapy.

Neutrophils: Musketeers against immunotherapy

Neutrophils, the most copious leukocytes in human blood, play a critical role in tumorigenesis, cancer progression, and immune suppression. Recently, neutrophils have attracted the attention of researchers, immunologists, and oncologists because of their potential role in orchestrating immune evasion in human diseases including cancer, which has led to a hot debate redefining the contribution of neutrophils in tumor progression and immunity. To make this debate fruitful, this review seeks to provide a recent update about the contribution of neutrophils in immune suppression and tumor progression. Here, we first described the molecular pathways through which neutrophils aid in cancer progression and orchestrate immune suppression/evasion. Later, we summarized the underlying molecular mechanisms of neutrophil-mediated therapy resistance and highlighted various approaches through which neutrophil antagonism may heighten the efficacy of the immune checkpoint blockade therapy. Finally, we have highlighted several unsolved questions and hope that answering these questions will provide a new avenue toward immunotherapy revolution.

Arginine Supplementation Targeting Tumor-Killing Immune Cells Reconstructs the Tumor Microenvironment and Enhances the Antitumor Immune Response

The tumor microenvironment (TME) is characterized by several immunosuppressive factors, of which weak acidity and l-arginine (l-arg) deficiency are two common features. A weak acidic environment threatens the survival of immune cells, and insufficient l-arg will severely restrain the effect of antitumor immune responses, both of which affect the efficiency of cancer treatments (especially immunotherapy). Meanwhile, l-arg is essential for tumor progression. Thus, two strategies, l-arg supplementation and l-arg deprivation, are developed for cancer treatment. However, these strategies have the potential risk of promoting tumor growth and impairing immune responses, which might lead to a paradoxical therapeutic effect. It is optimal to limit the l-arg availability of tumor cells from the microenvironment while supplying l-arg for immune cells. In this study, we designed a multivesicular liposome technology to continuously supply alkaline l-arg, which simultaneously changed the acidity and l-arg deficiency in the TME, and by selectively knocking down the CAT-2 transporter, l-arg starvation of tumors was maintained while tumor-killing immune cells were enriched in the TME. The results showed that our strategy promoted the infiltration and activation of CD8+ T cells in tumor, increased the proportion of M1 macrophages, inhibited melanoma growth, and prolonged survival. In combination with anti-PD-1 antibody, our strategy reversed the low tumor response to immune checkpoint blockade therapy, showing a synergistic antitumor effect. Our work provided a reference for improving the TME combined with regulating nutritional competitiveness to achieve the sensitization of immunotherapy.

The expanding role for small molecules in immuno-oncology

The advent of immune checkpoint inhibition (ICI) using antibodies against PD1 and its ligand PDL1 has prompted substantial efforts to develop complementary drugs. Although many of these are antibodies directed against additional checkpoint proteins, there is an increasing interest in small-molecule immuno-oncology drugs that address intracellular pathways, some of which have recently entered clinical trials. In parallel, small molecules that target pro-tumorigenic pathways in cancer cells and the tumour microenvironment have been found to have immunostimulatory effects that synergize with the action of ICI antibodies, leading to the approval of an increasing number of regimens that combine such drugs. Combinations with small molecules targeting cancer metabolism, cytokine/chemokine and innate immune pathways, and T cell checkpoints are now under investigation. This Review discusses the recent milestones and hurdles encountered in this area of drug development, as well as our views on the best path forward.

Discovery of Biomarkers of Resistance to Immune Checkpoint Blockade in NSCLC Using High-Plex Digital Spatial Profiling

INTRODUCTION

Despite the clinical efficacy of immune checkpoint inhibitors (ICIs) in NSCLC, only approximately 20% of patients remain disease-free at 5 years. Here, we use digital spatial profiling to find candidate biomarker proteins associated with ICI resistance.

METHODS

Pretreatment samples from 56 patients with NSCLC treated with ICI were analyzed using the NanoString GeoMx digital spatial profiling method. A panel of 71 photocleavable oligonucleotide-labeled primary antibodies was used for protein detection in four molecular compartments (tumor, leukocytes, macrophages, and immune stroma). Promising candidates were orthogonally validated with quantitative immunofluorescence. Available pretreatment samples from 39 additional patients with NSCLC who received ICI and 236 non-ICI-treated patients with operable NSCLC were analyzed to provide independent cohort validation.

RESULTS

Biomarker discovery using the protein-based molecular compartmentalization strategy allows 284 protein variables to be assessed for association with ICI resistance by univariate analysis using continuous log-scaled data. Of the 71 candidate protein biomarkers, CD66b in the CD45+CD68 molecular compartment (immune stroma) predicted significantly shorter overall survival (OS) (hazard ratio [HR] 1.31, p = 0.016) and was chosen for validation. Orthogonal validation by quantitative immunofluorescence illustrated that CD66b was associated with resistance to ICI therapy but not prognostic for poor outcomes in untreated NSCLC (discovery cohort [OS HR 2.49, p = 0.026], validation cohort [OS HR 2.05, p = 0.046], non-ICI-treated cohort [OS HR 1.67, p = 0.06]).

CONCLUSIONS

Using the technique, we have discovered that CD66b expression is indicative of resistance to ICI therapy in NSCLC. Given that CD66b identifies neutrophils, further studies are warranted to characterize the role of neutrophils in ICI resistance.

Host-Related Factors as Targetable Drivers of Immunotherapy Response in Non-Small Cell Lung Cancer Patients

Despite some significant therapeutic breakthroughs leading to immunotherapy, a high percentage of patients with non-small cell lung cancer (NSCLC) do not respond to treatment on relapse, thus experiencing poor prognosis and survival. The unsatisfying results could be related to the features of the tumor immune microenvironment and the dynamic interactions between a tumor and immune infiltrate. Host-tumor interactions strongly influence the course of disease and response to therapies. Thus, targeting host-associated factors by restoring their physiologic functions altered by the presence of a tumor represents a new therapeutic approach to control tumor development and progression. In NSCLC, the immunogenic tumor balance is shifted negatively toward immunosuppression due to the release of inhibitory factors as well as the presence of immunosuppressive cells. Among these cells, there are myeloid-derived suppressor cells, regulatory T cells that can generate a tumor-permissive milieu by reprogramming the cells of the hosts such as tumor-associated macrophages, tumor-associated neutrophils, natural killer cells, dendritic cells, and mast cells that acquire tumor-supporting phenotypes and functions. This review highlights the current knowledge of the involvement of host-related factors, including innate and adaptive immunity in orchestrating the tumor cell fate and the primary resistance mechanisms to immunotherapy in NSCLC. Finally, we discuss combinational therapeutic strategies targeting different aspects of the tumor immune microenvironment (TIME) to prime the host response. Further research dissecting the characteristics and dynamic interactions within the interface host-tumor is necessary to improve a patient fitness immune response and provide answers regarding the immunotherapy efficacy, with the aim to develop more successful treatments for NSCLC.

Tumor-associated neutrophils and neutrophil-targeted cancer therapies

Neutrophils are the frontline cells in response to microbial infections and are involved in a range of inflammatory disorders in the body. In recent years, neutrophils have gained considerable attention in their involvement of complex roles in tumor development and progression. Tumor-associated neutrophils (TANs) that accumulate in local region could be triggered by external stimuli from tumor microenvironment (TME) and switch between anti- and pro-tumor phenotypes. The anti-tumor neutrophils kill tumor cells through direct cytotoxic effects as well as indirect effects by activating adaptive immune responses. In contrast, the pro-tumor phenotype of neutrophils might be associated with cell proliferation, angiogenesis, and immunosuppression in TME. More recently, neutrophils have been proposed as a potential target in cancer therapy for their ability to diminish the pro-tumor pathways, such as by immune checkpoint blockade. This review discusses the complex roles of neutrophils in TME and highlights the strategies in neutrophil targeting in cancer treatment with a particular focus on the progresses of ongoing clinical trials involving neutrophil-targeted therapies.

A Phase 1 study of ADI-PEG20 (pegargiminase) combined with cisplatin and pemetrexed in ASS1-negative metastatic uveal melanoma

Metastatic uveal melanoma (UM) is a devastating disease with few treatment options. We evaluated the safety, tolerability and preliminary activity of arginine depletion using pegylated arginine deiminase (ADI‐PEG20; pegargiminase) combined with pemetrexed (Pem) and cisplatin (Cis) chemotherapy in a phase 1 dose‐expansion study of patients with argininosuccinate synthetase (ASS1)‐deficient metastatic UM. Eligible patients received up to six cycles of Pem (500 mg/m²) and Cis (75 mg/m²) every 3 weeks plus weekly intramuscular ADI (36 mg/m²), followed by maintenance ADI until progression (NCT02029690). Ten of fourteen ASS1‐deficient patients with UM liver metastases and a median of one line of prior immunotherapy received ADIPemCis. Only one ≥ grade 3 adverse event of febrile neutropenia was reported. Seven patients had stable disease with a median progression‐free survival of 3.0 months (range, 1.3–8.1) and a median overall survival of 11.5 months (range, 3.2–36.9). Despite anti‐ADI‐PEG20 antibody emergence, plasma arginine concentrations remained suppressed by 18 weeks with a reciprocal increase in plasma citrulline. Tumour rebiopsies at progression revealed ASS1 re‐expression as an escape mechanism. ADIPemCis was well tolerated with modest disease stabilisation in metastatic UM. Further investigation of arginine deprivation is indicated in UM including combinations with immune checkpoint blockade and additional anti‐metabolite strategies.

Significance of the Expression of TC and TG Levels in the Initial Diagnosis and Treatment of SCLC Patients and Their Tie-In with Prognosis

The article examines the expression of TC and TG levels in the initial diagnosis and treatment of SCLC patients and their tie-in with prognosis. Patients with SCLC are included in the case set, who are initially treated in the tumor center of our hospital from January 2020 to January 2021 and are confirmed by histopathology or cytology as the research subjects. 80 healthy volunteers are included in the control set, who received physical examination. All the enrolled patients received the first-line standard treatment plan, and the clinical data of all SCLC patients are inquired through the medical record file system of the hospital. At the initial diagnosis and treatment, the TG and TC levels of all patients and healthy persons are measured and recorded by blood biochemistry. For SCLC patients, the risk factors affecting the prognosis of patients with progression-free survival include newly diagnosed TC, TG levels, and tumor stage. Combined TC and TG detection can be used as indicators to predict the prognosis of the patients. TC and TG are significantly correlated with the prognosis of the patients with progression-free survival time. It is worthy of clinical application.

Immunosuppressive Features of the Microenvironment in Lymph Nodes Granulomas from Tuberculosis and HIV-Co-Infected Patients

Tuberculosis (TB) and HIV co-infection claims many lives every year. This study assessed immune responses in Mycobacterium tuberculosis-infected lymph node tissues from HIV-negative and HIV-positive patients compared with the peripheral circulation with a focus on myeloid cells and the cell-signaling enzymes, inducible nitric oxide synthase, and arginase (Arg)-1. Methods included immunohistochemistry or confocal microscopy and computerized image analyses, quantitative real-time PCR, multiplex Luminex, and flow cytometry. These findings indicate enhanced chronic inflammation and immune activation in TB/HIV co-infection but also enhanced immunosuppressive responses. Poorly formed necrotic TB granulomas with a high expression of M. tuberculosis antigens were elevated in TB/HIV-co-infected lymph nodes, and inducible nitric oxide synthase and Arg-1 expression was significantly higher in TB/HIV-co-infected compared with HIV-negative TB or control tissues. High Arg-1 expression was found in myeloid cells with a phenotype characteristic of myeloid-derived suppressor cells (MDCS) that were particularly abundant in TB/HIV-co-infected tissues. Accordingly, Lin-/HLA-DRlow/int/CD33+/CD11b+/CD15+ granulocytic myeloid-derived suppressor cells were significantly elevated in blood samples from TB/HIV-co-infected patients. CD15+ myeloid-derived suppressor cells correlated with plasma HIV viral load and M. tuberculosis antigen load in tissue but were inversely associated with peripheral CD4 T-cells counts. Enhanced chronic inflammation driven by M. tuberculosis and HIV co-infection may promote Arg-1-expressing MDSCs at the site of infection thereby advancing TB disease progression.

Influence of the Metabolism on Myeloid Cell Functions in Cancers: Clinical Perspectives

Tumor metabolism plays a crucial role in sustaining tumorigenesis. There have been increasing reports regarding the role of tumor metabolism in the control of immune cell functions, generating a potent immunosuppressive contexture that can lead to immune escape. The metabolic reprogramming of tumor cells and the immune escape are two major hallmarks of cancer, with several instances of crosstalk between them. In this paper, we review the effects of tumor metabolism on immune cells, focusing on myeloid cells due to their important role in tumorigenesis and immunosuppression from the early stages of the disease. We also discuss ways to target this specific crosstalk in cancer patients.

Importance of T, NK, CAR T and CAR NK Cell Metabolic Fitness for Effective Anti-Cancer Therapy: A Continuous Learning Process Allowing the Optimization of T, NK and CAR-Based Anti-Cancer Therapies

Simple Summary

Cancer treatments are evolving at a very rapid pace. Some of the most novel anti-cancer medicines under development rely on the modification of immune cells in order to transform them into potent tumor-killing cells. However, the tumor microenvironment (TME) is competing for nutrients with these harnessed immune cells and therefore paralyzes their metabolic effective and active anti-cancer activities. Here we describe strategies to overcome these hurdles imposed on immune cell activity, which lead to therapeutic approaches to enhance metabolic fitness of the patient’s immune system with the objective to improve their anti-cancer capacity.

Abstract

Chimeric antigen receptor (CAR) T and CAR NK cell therapies opened new avenues for cancer treatment. Although original successes of CAR T and CAR NK cells for the treatment of hematological malignancies were extraordinary, several obstacles have since been revealed, in particular their use for the treatment of solid cancers. The tumor microenvironment (TME) is competing for nutrients with T and NK cells and their CAR-expressing counterparts, paralyzing their metabolic effective and active states. Consequently, this can lead to alterations in their anti-tumoral capacity and persistence in vivo. High glucose uptake and the depletion of key amino acids by the TME can deprive T and NK cells of energy and building blocks, which turns them into a state of anergy, where they are unable to exert cytotoxic activity against cancer cells. This is especially true in the context of an immune-suppressive TME. In order to re-invigorate the T, NK, CAR T and CAR NK cell-mediated antitumor response, the field is now attempting to understand how metabolic pathways might change T and NK responses and functions, as well as those from their CAR-expressing partners. This revealed ways to metabolically rewire these cells by using metabolic enhancers or optimizing pre-infusion in vitro cultures of these cells. Importantly, next-generation CAR T and CAR NK products might include in the future the necessary metabolic requirements by improving their design, manufacturing process and other parameters. This will allow the overcoming of current limitations due to their interaction with the suppressive TME. In a clinical setting, this might improve their anti-cancer effector activity in synergy with immunotherapies. In this review, we discuss how the tumor cells and TME interfere with T and NK cell metabolic requirements. This may potentially lead to therapeutic approaches that enhance the metabolic fitness of CAR T and CAR NK cells, with the objective to improve their anti-cancer capacity.

Acupuncture Synergized With Bortezomib Improves Survival of Multiple Myeloma Mice via Decreasing Metabolic Ornithine

Multiple myeloma (MM) is a hematological malignancy worldwide in urgent need for novel therapeutic strategies. Since Velcade (bortezomib) was approved for the treatment of relapsed/refractory MM in 2003, we have seen considerable improvement in extending MM patient survival. However, most patients are fraught with high recurrence rate and incurability. Acupuncture is known for alleviating patient symptoms and improving the quality of life, but it is not well investigated in MM, especially in combination with bortezomib. In this study, we employed LC-MS and UHPLC-MS together with bioinformatics methods to test serum samples from 5TMM3VT MM murine model mice with four different treatments [control (C) group, bortezomib (V) treatment group, acupuncture (A) group, and combined (VA) group]. MM mice in group VA had longer survival time than mice in group A or group V. Joint pathway analysis indicated the underlying arginine and proline metabolism pathway among the 32 significantly decreased metabolites in group VA. CCK-8 assay and in vivo experiments validated that ornithine, the metabolite of arginine, promoted MM cell proliferation. In addition, gene expression omnibus (GEO) database analysis suggested that MM patients with higher ornithine decarboxylase 1 (ODC1) expression were evidently associated with poor overall survival. In summary, this study demonstrates the synergistic effects of acupuncture and bortezomib on extending the survival of MM model mice and provides potential therapeutic targets in the treatment of MM.

Targeted Anti-Tumor Immunotherapy Using Tumor Infiltrating Cells

In the tumor microenvironment, T cells, B cells, and many other cells play important and distinct roles in anti-tumor immunotherapy. Although the immune checkpoint blockade and adoptive cell transfer can elicit durable clinical responses, only a few patients benefit from these therapies. Increased understanding of tumor-infiltrating immune cells can provide novel therapies and drugs that induce a highly specific anti-tumor immune response to certain groups of patients. Herein, the recent research progress on tumor-infiltrating B cells and T cells, including CD8+ T cells, CD4+ T cells, and exhausted T cells and their role in anti-tumor immunity, is summarized. Moreover, several anti-tumor therapy approaches are discussed based on different immune cells and their prospects for future applications in cancer treatment.

Landscape of Myeloid-derived Suppressor Cell in Tumor Immunotherapy

Myeloid-derived suppressor cells (MDSC) are a group of immature cells that produced by emergency myelopoiesis. Emerging evidences have identified the vital role of MDSC in cancer microenvironment, in which MDSC exerts both immunological and non-immunological activities to assist the progression of cancer. Advances in pre-clinical research have provided us the understanding of MDSC in cancer context from the perspective of molecular mechanism. In clinical scenario, MDSC and its subsets have been discovered to exist in peripheral blood and tumor site of patients from various types of cancers. In this review, we highlight the clinical value of MDSC in predicting prognosis of cancer patients and the responses of immunotherapies, therefore to propose the MDSC-inhibiting strategy in the scenario of cancer immunotherapies. Phenotypes and biological functions of MDSC in cancer microenvironment are comprehensively summarized to provide potential targets of MDSC-inhibiting strategy from the aspect of molecular mechanisms.

Oncolytic Viro-Immunotherapy: An Emerging Option in the Treatment of Gliomas

The prognosis of malignant gliomas remains poor, with median survival fewer than 20 months and a 5-year survival rate merely 5%. Their primary location in the central nervous system (CNS) and its immunosuppressive environment with little T cell infiltration has rendered cancer therapies mostly ineffective, and breakthrough therapies such as immune checkpoint inhibitors (ICIs) have shown limited benefit. However, tumor immunotherapy is developing rapidly and can help overcome these obstacles. But for now, malignant gliomas remain fatal with short survival and limited therapeutic options. Oncolytic virotherapy (OVT) is a unique antitumor immunotherapy wherein viruses selectively or preferentially kill tumor cells, replicate and spread through tumors while inducing antitumor immune responses. OVTs can also recondition the tumor microenvironment and improve the efficacy of other immunotherapies by escalating the infiltration of immune cells into tumors. Some OVTs can penetrate the blood-brain barrier (BBB) and possess tropism for the CNS, enabling intravenous delivery. Despite the therapeutic potential displayed by oncolytic viruses (OVs), optimizing OVT has proved challenging in clinical development, and marketing approvals for OVTs have been rare. In June 2021 however, as a genetically engineered OV based on herpes simplex virus-1 (G47Δ), teserpaturev got conditional and time-limited approval for the treatment of malignant gliomas in Japan. In this review, we summarize the current state of OVT, the synergistic effect of OVT in combination with other immunotherapies as well as the hurdles to successful clinical use. We also provide some suggestions to overcome the challenges in treating of gliomas.

Breast cancer-derived GM-CSF regulates arginase 1 in myeloid cells to promote an immunosuppressive microenvironment

Tumor-infiltrating myeloid cells contribute to the development of the immunosuppressive tumor microenvironment. Myeloid cell expression of arginase 1 (ARG1) promotes a protumor phenotype by inhibiting T cell function and depleting extracellular l-arginine, but the mechanism underlying this expression, especially in breast cancer, is poorly understood. In breast cancer clinical samples and in our mouse models, we identified tumor-derived GM-CSF as the primary regulator of myeloid cell ARG1 expression and local immune suppression through a gene-KO screen of breast tumor cell-produced factors. The induction of myeloid cell ARG1 required GM-CSF and a low pH environment. GM-CSF signaling through STAT3 and p38 MAPK and acid signaling through cAMP were required to activate myeloid cell ARG1 expression in a STAT6-independent manner. Importantly, breast tumor cell-derived GM-CSF promoted tumor progression by inhibiting host antitumor immunity, driving a significant accumulation of ARG1-expressing myeloid cells compared with lung and melanoma tumors with minimal GM-CSF expression. Blockade of tumoral GM-CSF enhanced the efficacy of tumor-specific adoptive T cell therapy and immune checkpoint blockade. Taken together, we show that breast tumor cell-derived GM-CSF contributes to the development of the immunosuppressive breast cancer microenvironment by regulating myeloid cell ARG1 expression and can be targeted to enhance breast cancer immunotherapy.

3D Model of the Early Melanoma Microenvironment Captures Macrophage Transition into a Tumor-Promoting Phenotype

Simple Summary

We developed a “tumor-in-a-dish” experimental system to study the early events favoring tumor growth and suppression of the immune response in metastatic melanoma. We combined murine melanoma tumor cells with fibroblasts and macrophages in a 3D collagen matrix and characterized how interactions between these three cell types, which are present in the early stages of tumorigenesis, drive immune suppression and the tumor-promoting transition in macrophages that is observed in vivo. Over the course of 7 days in the co-cultures, we quantified the dynamics of cues transmitted by direct cell–cell interactions, through the extracellular matrix and through secretion of immune mediators. We found that macrophages acquired features and a functional profile consistent with those present in in vivo murine melanoma tumors. This system will enable future studies of macrophage–stromal cross-talk in the melanoma microenvironment and provide a platform to test potential therapeutic approaches aimed at stimulating immune activity in macrophages.

Abstract

Tumor immune response is shaped by the tumor microenvironment (TME), which often evolves to be immunosuppressive, promoting disease progression and metastasis. An important example is melanoma tumors, which display high numbers of tumor-associated macrophages (TAMs) that are immunosuppressive but also have the potential to restore anti-tumor activity. However, to therapeutically target TAMs, there is a need to understand the early events that shape their tumor-promoting profile. To address this, we built and optimized 3D in vitro co-culture systems, composed of a collagen-I matrix scaffolding murine bone-marrow-derived macrophages (BMDMs), YUMM1.7 melanoma cells, and fibroblasts to recreate the early melanoma TME and study how interactions with fibroblasts and tumor cells modulate macrophage immune activity. We monitored BMDM behavior and interactions through time-lapse imaging and characterized their activation and secretion. We found that stromal cells induced a rapid functional activation, with increased motility and response from BMDMs. Over the course of seven days, BMDMs acquired a phenotype and secretion profile that resembled melanoma TAMs in established tumors. Overall, the direct cell–cell interactions with the stromal components in a 3D environment shape BMDM transition to a TAM-like immunosuppressive state. Our systems will enable future studies of changes in macrophage–stromal cross-talk in the melanoma TME.

Evaluation of autophagy mediators in myeloid-derived suppressor cells during human tuberculosis

Myeloid-derived suppressor cells (MDSC) are induced during active TB disease to restore immune homeostasis but instead exacerbate disease outcome due to chronic inflammation. Autophagy, in conventional phagocytes, ensures successful clearance of M.tb. However, autophagy has been demonstrated to induce prolonged MDSC survival. Here we investigate the relationship between autophagy mediators and MDSC in the context of active TB disease and during anti-TB therapy. We demonstrate a significant increase in MDSC frequencies in untreated active TB cases with these MDSC expressing TLR4 and significantly more mTOR and IL-6 than healthy controls, with mTOR levels decreasing during anti-TB therapy. Finally, we show that HMGB1 serum concentrations decrease in parallel with mTOR. These findings suggest a complex interplay between MDSC and autophagic mediators, potentially dependent on cellular localisation and M.tb infection state.

Amino Acid Transport and Metabolism in Myeloid Function

Regulation of amino acid availability and metabolism in immune cells is essential for immune system homeostasis and responses to exogenous and endogenous challenges including microbial infection, tumorigenesis and autoimmunity. In myeloid cells the consumption of amino acids such as arginine and tryptophan and availability of their metabolites are key drivers of cellular identity impacting development, functional polarization to an inflammatory or regulatory phenotype, and interaction with other immune cells. In this review, we discuss recent developments and emerging concepts in our understanding of the impact amino acid availability and consumption has on cellular phenotype focusing on two key myeloid cell populations, macrophages and myeloid derived suppressor cells (MDSCs). We also highlight the potential of myeloid-specific of amino acid transporters and catabolic enzymes as immunotherapy targets in a variety of conditions such as cancer and autoimmune disease discussing the opportunities and limitations in targeting these pathways for clinical therapy.

The Dawn of Myeloid-Derived Suppressor Cells: Identification of Arginase I as the Mechanism of Immune Suppression

A study published in Cancer Research in 2004 by Rodriguez and colleagues identified the existence of arginase-producing myeloid cells in tumors distinct from macrophages. They demonstrated the role of arginase in negative regulation of T-cell function in vivo This was one of the first reports implicating cells, which later were named myeloid-derived suppressor cells (MDSC), in T-cell suppression in vivo and linking this effect with arginase activity and expression. This work was important in advancing the field of MDSC research and helped to bring these cells to the forefront of cancer immunology.See related article by Rodriguez et al., Cancer Res 2004;64:5839-49.

Inhibition of arginase modulates T-cell response in the tumor microenvironment of lung carcinoma

Immunotherapy has demonstrated significant activity in a broad range of cancer types, but still the majority of patients receiving it do not maintain durable therapeutic responses. Amino acid metabolism has been proposed to be involved in the regulation of immune response. Here, we investigated in detail the role of arginase 1 (Arg1) in the modulation of antitumor immune response against poorly immunogenic Lewis lung carcinoma. We observed that tumor progression is associated with an incremental increase in the number of Arg1⁺ myeloid cells that accumulate in the tumor microenvironment and cause systemic depletion of ʟ-arginine. In advanced tumors, the systemic concentrations of ʟ-arginine are decreased to levels that impair the proliferation of antigen-specific T-cells. Systemic or myeloid-specific Arg1 deletion improves antigen-induced proliferation of adoptively transferred T-cells and leads to inhibition of tumor growth. Arginase inhibitor was demonstrated to modestly inhibit tumor growth when used alone, and to potentiate antitumor effects of anti-PD-1 monoclonal antibodies and STING agonist. The effectiveness of the combination immunotherapy was insufficient to induce complete antitumor responses, but was significantly better than treatment with the checkpoint inhibitor alone. Together, these results indicate that arginase inhibition alone is of modest therapeutic benefit in poorly immunogenic tumors; however, in combination with other treatment strategies it may significantly improve survival outcomes.

Neutrophils in the era of immune checkpoint blockade

The immune checkpoint blockade-based immunotherapies are revolutionizing cancer management. Tumor-associated neutrophils (TANs) were recently highlighted to have a pivotal role in modulating the tumor microenvironment and the antitumor immune response. However, these cells were largely ignored during the development of therapies based on programmed cell death receptor or ligand-1 and cytotoxic T lymphocyte antigen-4 immune checkpoint inhibitors (ICIs). Latest evidences of neutrophil functional diversity in tumor raised many questions and suggest that targeting these cells can offer new treatment opportunities in the context of ICI development. Here, we summarized key information on TAN origin, function, and plasticity that should be considered when developing ICIs and provide a detailed review of the ongoing clinical trials that combine ICIs and a second compound that might affect or be affected by TANs. This review article synthetizes important notions from the literature demonstrating that: (1) Cancer development associates with a profound alteration of neutrophil biogenesis and function that can predict and interfere with the response to ICIs, (2) Neutrophil infiltration in tumor is associated with key features of resistance to ICIs, and (3) TANs play an important role in resistance to antiangiogenic drugs reducing their clinical benefit when used in combination with ICIs. Finally, exploring the clinical/translational aspects of neutrophil impact on the response to ICIs offers the opportunity to propose new translational research avenues to better understand TAN biology and treat patients.