Inhibition of arginase by CB-1158 blocks myeloid cell-mediated immune suppression in the tumor microenvironment

Targeting the glutamine-arginine-proline metabolism axis in cancer

Metabolic abnormalities are an important feature of tumours. The glutamine-arginine-proline axis is an important node of cancer metabolism and plays a major role in amino acid metabolism. This axis also acts as a scaffold for the synthesis of other nonessential amino acids and essential metabolites. In this paper, we briefly review (1) the glutamine addiction exhibited by tumour cells with accelerated glutamine transport and metabolism; (2) the methods regulating extracellular glutamine entry, intracellular glutamine synthesis and the fate of intracellular glutamine; (3) the glutamine, proline and arginine metabolic pathways and their interaction; and (4) the research progress in tumour therapy targeting the glutamine-arginine-proline metabolic system, with a focus on summarising the therapeutic research progress of strategies targeting of one of the key enzymes of this metabolic system, P5CS (ALDH18A1). This review provides a new basis for treatments targeting the metabolic characteristics of tumours.

Metabolic reprogramming and immune evasion: the interplay in the tumor microenvironment

Tumor cells possess complex immune evasion mechanisms to evade immune system attacks, primarily through metabolic reprogramming, which significantly alters the tumor microenvironment (TME) to modulate immune cell functions. When a tumor is sufficiently immunogenic, it can activate cytotoxic T-cells to target and destroy it. However, tumors adapt by manipulating their metabolic pathways, particularly glucose, amino acid, and lipid metabolism, to create an immunosuppressive TME that promotes immune escape. These metabolic alterations impact the function and differentiation of non-tumor cells within the TME, such as inhibiting effector T-cell activity while expanding regulatory T-cells and myeloid-derived suppressor cells. Additionally, these changes lead to an imbalance in cytokine and chemokine secretion, further enhancing the immunosuppressive landscape. Emerging research is increasingly focusing on the regulatory roles of non-tumor cells within the TME, evaluating how their reprogrammed glucose, amino acid, and lipid metabolism influence their functional changes and ultimately aid in tumor immune evasion. Despite our incomplete understanding of the intricate metabolic interactions between tumor and non-tumor cells, the connection between these elements presents significant challenges for cancer immunotherapy. This review highlights the impact of altered glucose, amino acid, and lipid metabolism in the TME on the metabolism and function of non-tumor cells, providing new insights that could facilitate the development of novel cancer immunotherapies.

Clinical landscape of macrophage-reprogramming cancer immunotherapies

Tumour-associated macrophages (TAMs) sustain a tumour-supporting and immunosuppressive milieu and therefore aggravate cancer prognosis. To modify TAM behaviour and unlock their anti-tumoural potential, novel TAM-reprogramming immunotherapies are being developed at an accelerating rate. At the same time, scientific discoveries have highlighted more sophisticated TAM phenotypes with complex biological functions and contradictory prognostic associations. To understand the evolving clinical landscape, we reviewed current and past clinically evaluated TAM-reprogramming cancer therapeutics and summarised almost 200 TAM-reprogramming agents investigated in more than 700 clinical trials. Observable overall trends include a high frequency of overlapping strategies against the same therapeutic targets, development of more complex strategies to improve previously ineffective approaches and reliance on combinatory strategies for efficacy. However, strong anti-tumour efficacy is uncommon, which encourages re-directing efforts on identifying biomarkers for eligible patient populations and comparing similar treatments earlier. Future endeavours will benefit from considering the shortcomings of past treatment strategies and accommodating the emerging complexity of TAM biology.

Myeloid‑derived suppressor cells: Key immunosuppressive regulators and therapeutic targets in colorectal cancer (Review)

Globally, colorectal cancer (CRC) is the third most common type of cancer. CRC has no apparent symptoms in the early stages of disease, and most patients receive a confirmed diagnosis in the middle or late disease stages. The incidence of CRC continues to increase, and the affected population tends to be younger. Therefore, determining how to achieve an early CRC diagnosis and treatment has become a top priority for prolonging patient survival. Myeloid‑derived suppressor cells (MDSCs) are a group of bone marrow‑derived immuno‑negative regulatory cells that are divided into two subpopulations, polymorphonuclear‑MDSCs and monocytic‑MDSCs, based on their phenotypic similarities to neutrophils and monocytes, respectively. These cells can inhibit the immune response and promote cancer cell metastasis in the tumour microenvironment (TME). A large aggregation of MDSCs in the TME is often a marker of cancer and a poor prognosis in inflammatory diseases of the intestine (such as colonic adenoma and ulcerative colitis). In the present review, the phenotypic classification of MDSCs in the CRC microenvironment are first discussed. Then, the amplification, role and metastatic mechanism of MDSCs in the CRC TME are described, focusing on genes, gene modifications, proteins and the intestinal microenvironment. Finally, the progress in CRC‑targeted therapies that aim to modulate the quantity, function and structure of MDSCs are summarized in the hope of identifying potential screening markers for CRC and improving CRC prognosis and therapeutic options.

Targeting ROS-sensing Nrf2 potentiates anti-tumor immunity of intratumoral CD8+ T and CAR-T cells

Cytotoxic T lymphocytes (CTLs) play a crucial role in cancer rejection. However, CTLs encounter dysfunction and exhaustion in the immunosuppressive tumor microenvironment (TME). Although the reactive oxygen species (ROS)-rich TME attenuates CTL function, the underlying molecular mechanism remains poorly understood. The nuclear factor erythroid 2-related 2 (Nrf2) is the ROS-responsible factor implicated in increasing susceptibility to cancer progression. Therefore, we examined how Nrf2 is involved in anti-tumor responses of CD8+ T and chimeric antigen receptor (CAR) T cells in the ROS-rich TME. Here, we demonstrated that tumor growth in Nrf2-/- mice was significantly controlled and was reversed by T cell depletion and further confirmed that Nrf2 deficiency in T cells promotes anti-tumor responses using an adoptive transfer model of antigen-specific CD8+ T cells. Nrf2-deficient CTLs are resistant to ROS, and their effector functions are sustained in the TME. Furthermore, Nrf2 knockdown in human CAR-T cells enhanced the survival and function of intratumoral CAR-T cells in a solid tumor xenograft model and effectively controlled tumor growth. ROS-sensing Nrf2 inhibits the anti-tumor T cell responses, indicating that Nrf2 may be a potential target for T cell immunotherapy strategies against solid tumors.

Targeting amino acid-metabolizing enzymes for cancer immunotherapy

Despite the immune system's role in the detection and eradication of abnormal cells, cancer cells often evade elimination by exploitation of various immune escape mechanisms. Among these mechanisms is the ability of cancer cells to upregulate amino acid-metabolizing enzymes, or to induce these enzymes in tumor-infiltrating immunosuppressive cells. Amino acids are fundamental cellular nutrients required for a variety of physiological processes, and their inadequacy can severely impact immune cell function. Amino acid-derived metabolites can additionally dampen the anti-tumor immune response by means of their immunosuppressive activities, whilst some can also promote tumor growth directly. Based on their evident role in tumor immune escape, the amino acid-metabolizing enzymes glutaminase 1 (GLS1), arginase 1 (ARG1), inducible nitric oxide synthase (iNOS), indoleamine 2,3-dioxygenase 1 (IDO1), tryptophan 2,3-dioxygenase (TDO) and interleukin 4 induced 1 (IL4I1) each serve as a promising target for immunotherapeutic intervention. This review summarizes and discusses the involvement of these enzymes in cancer, their effect on the anti-tumor immune response and the recent progress made in the preclinical and clinical evaluation of inhibitors targeting these enzymes.

Metabolic reprogramming in tumor immune microenvironment: Impact on immune cell function and therapeutic implications

Understanding of the metabolic reprogramming has revolutionized our insights into tumor progression and potential treatment. This review concentrates on the aberrant metabolic pathways in cancer cells within the tumor microenvironment (TME). Cancer cells differ from normal cells in their metabolic processing of glucose, amino acids, and lipids in order to adapt to heightened biosynthetic and energy needs. These metabolic shifts, which crucially alter lactic acid, amino acid and lipid metabolism, affect not only tumor cell proliferation but also TME dynamics. This review also explores the reprogramming of various immune cells in the TME. From a therapeutic standpoint, targeting these metabolic alterations represents a novel cancer treatment strategy. This review also discusses approaches targeting the regulation of metabolism of different nutrients in tumor cells and influencing the tumor microenvironment to enhance the immune response. In summary, this review summarizes metabolic reprogramming in cancer and its potential as a target for innovative therapeutic strategies, offering fresh perspectives on cancer treatment.

Research trends in lung cancer and the tumor microenvironment: a bibliometric analysis of studies published from 2014 to 2023

Background

Lung cancer (LC) is one of the most common malignant tumors in the world and the leading cause of cancer-related deaths, which seriously threatens human life and health as well as brings a heavy burden to the society. In recent years, the tumor microenvironment (TME) has become an emerging research field and hotspot affecting tumor pathogenesis and therapeutic approaches. However, to date, there has been no bibliometric analysis of lung cancer and the tumor microenvironment from 2014 to 2023.This study aims to comprehensively summarize the current situation and development trends in the field from a bibliometric perspective.

Methods

The publications about lung cancer and the tumor microenvironment from 2014 to 2023 were extracted from the Web of Science Core Collection (WoSCC). The Microsoft Excel, Origin, R-bibliometrix, CiteSpace, and VOSviewer software are comprehensively used to scientifically analyze the data.

Results

Totally, 763 publications were identified in this study. A rapid increase in the number of publications was observed after 2018. More than 400 organizations published these publications in 36 countries or regions. China and the United States have significant influence in this field. Zhou, CC and Frontiers in Immunology are the most productive authors and journals respectively. Besides, the most frequently cited references were those on lung cancer pathogenesis, clinical trials, and treatment modalities. It suggests that novel lung cancer treatment models mainly based on the TME components, such as cancer-associated fibroblasts (CAFs) may lead to future research trends.

Conclusions

The field of lung cancer and the tumor microenvironment research is still in the beginning stages. Gene expression, molecular pathways, therapeutic modalities, and novel detection technologies in this field have been widely studied by researchers. This is the first bibliometric study to comprehensively summarize the research trend and development regarding lung cancer and tumor microenvironment over the last decade. The result of our research provides the updated perspective for scholars to understand the key information and cutting-edge hotspots in this field, as well as to identify future research directions.

Macrophage-fibroblast crosstalk drives Arg1-dependent lung fibrosis via ornithine loading

Monocyte-derived macrophages recruited to injured tissues induce a maladaptive fibrotic response characterized by excessive production of collagen by local fibroblasts. Macrophages initiate this programming via paracrine factors, but it is unknown whether reciprocal responses from fibroblasts enhance profibrotic polarization of macrophages. We identify macrophage-fibroblast crosstalk necessary for injury-associated fibrosis, in which macrophages induced interleukin 6 ( IL-6 ) expression in fibroblasts via purinergic receptor P2rx4 signaling, and IL-6, in turn, induced arginase 1 ( Arg1 ) expression in macrophages. Arg1 contributed to fibrotic responses by metabolizing arginine to ornithine, which fibroblasts used as a substrate to synthesize proline, a uniquely abundant constituent of collagen. Imaging of idiopathic pulmonary fibrosis (IPF) lung samples confirmed expression of ARG1 in myeloid cells, and arginase inhibition suppressed collagen expression in cultured precision-cut IPF lung slices. Taken together, we define a circuit between macrophages and fibroblasts that facilitates cross-feeding metabolism necessary for injury-associated fibrosis.

N-Heterocyclic carbene catalytic 1,2-boron migrative acylation accelerated by photocatalysis

The transformation of organoboron compounds plays an important role in synthetic chemistry, and recent advancements in boron-migration reactions have garnered considerable attention. Here, we report an unprecedented 1,2-boron migrative acylation upon photocatalysis-facilitated N-heterocyclic carbene catalysis. The design of a redox-active boronic ester substrate, serving as an excellent β-boron radical precursor, is the linchpin to the success of this chemistry. With the established protocol, a wide spectrum of β-boryl ketones has been rapidly synthesized, which could further undergo various C─B bond transformations to give multifunctionalized products. The robustness of this catalytic strategy is underscored by its successful application in late-stage modification of drug-derived molecules and natural products. Preliminary mechanistic investigations, including several control experiments, photochemistry measurements, and computational studies, shed light on the catalytic radical reaction mechanism.

Tumor-associated macrophages restrict CD8+ T cell function through collagen deposition and metabolic reprogramming of the breast cancer microenvironment

Tumor progression is accompanied by fibrosis, a condition of excessive extracellular matrix accumulation, which is associated with diminished antitumor immune infiltration. Here we demonstrate that tumor-associated macrophages (TAMs) respond to the stiffened fibrotic tumor microenvironment (TME) by initiating a collagen biosynthesis program directed by transforming growth factor-β. A collateral effect of this programming is an untenable metabolic milieu for productive CD8+ T cell antitumor responses, as collagen-synthesizing macrophages consume environmental arginine, synthesize proline and secrete ornithine that compromises CD8+ T cell function in female breast cancer. Thus, a stiff and fibrotic TME may impede antitumor immunity not only by direct physical exclusion of CD8+ T cells but also through secondary effects of a mechano-metabolic programming of TAMs, which creates an inhospitable metabolic milieu for CD8+ T cells to respond to anticancer immunotherapies.

Immunological Aspects of Cancer Cell Metabolism

Cancer cells adeptly manipulate their metabolic processes to evade immune detection, a phenomenon intensifying the complexity of cancer progression and therapy. This review delves into the critical role of cancer cell metabolism in the immune-editing landscape, highlighting how metabolic reprogramming facilitates tumor cells to thrive despite immune surveillance pressures. We explore the dynamic interactions within the tumor microenvironment (TME), where cancer cells not only accelerate their glucose and amino acid metabolism but also induce an immunosuppressive state that hampers effective immune response. Recent findings underscore the metabolic competition between tumor and immune cells, particularly focusing on how this interaction influences the efficacy of emerging immunotherapies. By integrating cutting-edge research on the metabolic pathways of cancer cells, such as the Warburg effect and glutamine addiction, we shed light on potential therapeutic targets. The review proposes that disrupting these metabolic pathways could enhance the response to immunotherapy, offering a dual-pronged strategy to combat tumor growth and immune evasion.

Metabolic Adaptations and Functional Activity of Macrophages in Homeostasis and Inflammation

In recent years, the role of cellular metabolism in immunity has come into the focus of many studies. These processes form a basis for the maintenance of tissue integrity and homeostasis, as well as represent an integral part of the immune response, in particular, inflammation. Metabolic adaptations not only ensure energy supply for immune response, but also affect the functions of immune cells by controlling transcriptional and post-transcriptional programs. Studying the immune cell metabolism facilitates the search for new treatment approaches, especially for metabolic disorders. Macrophages, innate immune cells, are characterized by a high functional plasticity and play a key role in homeostasis and inflammation. Depending on the phenotype and origin, they can either perform various regulatory functions or promote inflammation state, thus exacerbating the pathological condition. Furthermore, their adaptations to the tissue-specific microenvironment influence the intensity and type of immune response. The review examines the effect of metabolic reprogramming in macrophages on the functional activity of these cells and their polarization. The role of immunometabolic adaptations of myeloid cells in tissue homeostasis and in various pathological processes in the context of inflammatory and metabolic diseases is specifically discussed. Finally, modulation of the macrophage metabolism-related mechanisms reviewed as a potential therapeutic approach.

Same yet different - how lymph node heterogeneity affects immune responses

Lymph nodes are secondary lymphoid organs in which immune responses of the adaptive immune system are initiated and regulated. Distributed throughout the body and embedded in the lymphatic system, local lymph nodes are continuously informed about the state of the organs owing to a constant drainage of lymph. The tissue-derived lymph carries products of cell metabolism, proteins, carbohydrates, lipids, pathogens and circulating immune cells. Notably, there is a growing body of evidence that individual lymph nodes differ from each other in their capacity to generate immune responses. Here, we review the structure and function of the lymphatic system and then focus on the factors that lead to functional heterogeneity among different lymph nodes. We will discuss how lymph node heterogeneity impacts on cellular and humoral immune responses and the implications for vaccination, tumour development and tumour control by immunotherapy.

Cellular metabolism regulates the differentiation and function of T-cell subsets

T cells are an important component of adaptive immunity and protect the host from infectious diseases and cancers. However, uncontrolled T cell immunity may cause autoimmune disorders. In both situations, antigen-specific T cells undergo clonal expansion upon the engagement and activation of antigens. Cellular metabolism is reprogrammed to meet the increase in bioenergetic and biosynthetic demands associated with effector T cell expansion. Metabolites not only serve as building blocks or energy sources to fuel cell growth and expansion but also regulate a broad spectrum of cellular signals that instruct the differentiation of multiple T cell subsets. The realm of immunometabolism research is undergoing swift advancements. Encapsulating all the recent progress within this concise review in not possible. Instead, our objective is to provide a succinct introduction to this swiftly progressing research, concentrating on the metabolic intricacies of three pivotal nutrient classes-lipids, glucose, and amino acids-in T cells. We shed light on recent investigations elucidating the roles of these three groups of metabolites in mediating the metabolic and immune functions of T cells. Moreover, we delve into the prospect of "editing" metabolic pathways within T cells using pharmacological or genetic approaches, with the aim of synergizing this approach with existing immunotherapies and enhancing the efficacy of antitumor and antiinfection immune responses.

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.

Leveraging macrophage metabolism for anticancer therapy: opportunities and pitfalls

Tumor-associated macrophages (TAMs) constitute an important part of the tumor microenvironment (TME) that regulates tumor progression. Tumor-derived signals, hypoxia, and competition for nutrients influence TAMs to reprogram their cellular metabolism. This altered metabolic profile creates a symbiotic communication between tumor and other immune cells to support tumor growth. In addition, the metabolic profile of TAMs regulates the expression of immune checkpoint molecules. The dynamic plasticity also allows TAMs to reshape their metabolism in response to modern therapeutic strategies. Therefore, over the years, a significant number of approaches have been implicated to reprogram cancer-promoting metabolism in TAMs. In this review, we discuss the current strategies and pitfalls, along with upcoming promising opportunities in leveraging TAM metabolism for developing better therapeutic approaches against cancer.

PD-1 inhibition with retifanlimab and/or arginase inhibition with INCB001158 in Japanese patients with solid tumors: A phase I study

BACKGROUND

Retifanlimab is a humanized monoclonal antibody targeting programmed death protein-1, and INCB001158 is an oral arginase inhibitor. This phase Ib study investigated retifanlimab, INCB001158, and their combination in Japanese patients with advanced solid tumors.

METHODS

Patients received retifanlimab (500 mg every 4 weeks [Q4W] i.v.) or escalating doses of INCB001158 (75 or 100 mg twice daily [BID]) monotherapy in Part 1 and combination of retifanlimab (500 mg Q4W) and INCB001158 (100 mg BID) in Part 2. Primary endpoints were safety, tolerability, dose-limiting toxicities (DLTs), and determination of recommended phase II doses in Japanese patients.

RESULTS

Eighteen patients (retifanlimab or INCB001158 monotherapy and combination; n = 6 each) were enrolled at 2 sites in Japan. There were no DLTs, fatal adverse events (AEs), or discontinuations due to AEs. Rash (all grade 1) was the most common treatment-emergent AE with retifanlimab (n = 6). Treatment-related AEs were reported with retifanlimab (n = 4) or INCB001158 (n = 2) monotherapy and with combination (n = 4); an immune-related AE (thyroid disorder, grade 2) was reported with combination. Two responses were observed with retifanlimab monotherapy (1 complete, 1 partial) and 1 stable disease (SD), for an overall response rate of 33.3% (95% confidence interval [CI], 4.3-77.7) and disease control rate (DCR) of 50% (95% CI, 11.8-88.2). Three patients had SD with INCB001158 monotherapy (DCR 50%; 95% CI, 11.8-88.2). No responses or SD were observed with combination therapy.

CONCLUSION

Retifanlimab, INCB001158, and their combination had acceptable safety profiles. Promising retifanlimab antitumor activity warrants further investigation in Japanese patients.

Preclinical Efficacy of Cabazitaxel Loaded Poly(2-alkyl cyanoacrylate) Nanoparticle Variants

Background

Biodegradable poly(alkyl cyanoacrylate) (PACA) nanoparticles (NPs) are receiving increasing attention in anti-cancer nanomedicine development not only for targeted cancer chemotherapy, but also for modulation of the tumor microenvironment. We previously reported promising results with cabazitaxel (CBZ) loaded poly(2-ethylbutyl cyanoacrylate) NPs (PEBCA-CBZ NPs) in a patient derived xenograft (PDX) model of triple-negative breast cancer, and this was associated with a decrease in M2 macrophages. The present study aims at comparing two endotoxin-free PACA NP variants (PEBCA and poly(2-ethylhexyl cyanoacrylate); PEHCA), loaded with CBZ and test whether conjugation with folate would improve their effect.

Methods

Cytotoxicity assays and cellular uptake of NPs by flow cytometry were performed in different breast cancer cells. Biodistribution and efficacy studies were performed in PDX models of breast cancer. Tumor associated immune cells were analyzed by multiparametric flow cytometry.

Results

In vitro studies showed similar NP-induced cytotoxicity patterns despite difference in early NP internalization. On intravenous injection, the liver cleared the majority of NPs. Efficacy studies in the HBCx39 PDX model demonstrated an enhanced effect of drug-loaded PEBCA variants compared with free drug and PEHCA NPs. Furthermore, the folate conjugated PEBCA variant did not show any enhanced effects compared with the unconjugated counterpart which might be due to unfavorable orientation of folate on the NPs. Finally, analyses of the immune cell populations in tumors revealed that treatment with drug loaded PEBCA variants affected the myeloid cells, especially macrophages, contributing to an inflammatory, immune activated tumor microenvironment.

Conclusion

We report for the first time, comparative efficacy of PEBCA and PEHCA NP variants in triple negative breast cancer models and show that CBZ-loaded PEBCA NPs exhibit a combined effect on tumor cells and on the tumor associated myeloid compartment, which may boost the anti-tumor response.

Determination of Serum Arginase-1 Concentrations and Serum Arginase Activity for the Non-Invasive Diagnosis of Endometriosis

Backgroud: Endometriosis remains a diagnostic challenge, both clinically and economically, affecting 6% to 15% of women of child-bearing potential. We have attempted to determine whether testing serum concentrations and activity of arginase isoenzymes could be useful for the non-invasive diagnosis of endometriosis. Methods: This study involved 180 women (105 endometriosis subjects-study group B; 22 subjects with other benign gynaecological conditions-control group 1-K1, both undergoing surgery; and 53 healthy subjects without features of endometriosis-control group 2-K2). Results: Preoperative and postoperative arginase-1 (Arg-1) concentrations were significantly higher in patients, as compared with the control groups K1 (p < 0.0001 and p = 0.0005, respectively) and K2 (both p < 0.0001). Similarly, arginase activity was significantly higher in patients than in the control group K1 before surgery and higher than in both control groups after surgery. No significant differences in either Arg-1 concentrations or arginase activity were noted between the operated control group K1 and the non-operated control group K2. A significant postoperative decrease in Arg-1 concentration was observed within both patient (p < 0.0001) and control group K1 (p = 0.0043). Diagnostic performance was assessed using the receiver operating characteristic (ROC) method. The threshold for differentiation between endometriosis patients and healthy non-operated controls was 42.3 ng/mL, with a sensitivity of 90% and specificity of 81%. For differentiation of patients and operated controls with benign gynaecological conditions, the threshold was 78.4 ng/mL, with a sensitivity of 61% and specificity of 95%. Conclusions: We, therefore, conclude that Arg-1 serum concentrations and arginase activity could be considered potential biomarkers for endometriosis but require further studies on larger cohorts of patients.

Advances in metabolic reprogramming of NK cells in the tumor microenvironment on the impact of NK therapy

Natural killer (NK) cells are unique from other immune cells in that they can rapidly kill multiple neighboring cells without the need for antigenic pre-sensitization once the cells display surface markers associated with oncogenic transformation. Given the dynamic role of NK cells in tumor surveillance, NK cell-based immunotherapy is rapidly becoming a "new force" in tumor immunotherapy. However, challenges remain in the use of NK cell immunotherapy in the treatment of solid tumors. Many metabolic features of the tumor microenvironment (TME) of solid tumors, including oxygen and nutrient (e.g., glucose, amino acids) deprivation, accumulation of specific metabolites (e.g., lactate, adenosine), and limited availability of signaling molecules that allow for metabolic reorganization, multifactorial shaping of the immune-suppressing TME impairs tumor-infiltrating NK cell function. This becomes a key barrier limiting the success of NK cell immunotherapy in solid tumors. Restoration of endogenous NK cells in the TME or overt transfer of functionally improved NK cells holds great promise in cancer therapy. In this paper, we summarize the metabolic biology of NK cells, discuss the effects of TME on NK cell metabolism and effector functions, and review emerging strategies for targeting metabolism-improved NK cell immunotherapy in the TME to circumvent these barriers to achieve superior efficacy of NK cell immunotherapy.

Metabolic interplay: tumor macrophages and regulatory T cells

The tumor microenvironment (TME) contains a complex cellular ecosystem where cancer, stromal, vascular, and immune cells interact. Macrophages and regulatory T cells (Tregs) are critical not only for maintaining immunological homeostasis and tumor growth but also for monitoring the functional states of other immune cells. Emerging evidence reveals that metabolic changes in macrophages and Tregs significantly influence their pro-/antitumor functions through the regulation of signaling cascades and epigenetic reprogramming. Hence, they are increasingly recognized as therapeutic targets in cancer immunotherapy. Specific metabolites in the TME may also affect their pro-/antitumor functions by intervening with the metabolic machinery. We discuss how metabolites influence the immunosuppressive phenotypes of tumor-associated macrophages (TAMs) and Tregs. We then describe how TAMs and Tregs, independently or collaboratively, utilize metabolic mechanisms to suppress the activity of CD8+ T cells. Finally, we highlight promising metabolic interventions that can improve the outcome of current cancer therapies.

Novel therapeutic strategies targeting myeloid-derived suppressor cell immunosuppressive mechanisms for cancer treatment

Cancer is the leading cause of death globally superseded only by cardiovascular diseases, and novel strategies to overcome therapeutic resistance against existing cancer treatments are urgently required. Myeloid-derived suppressor cells (MDSCs) are immature myeloid cells with potent immunosuppressive capacity against well-established anti-tumour effectors such as natural killer cells (NK cells) and T cells thereby promoting cancer initiation and progression. Critically, MDSCs are readily identified in almost all tumour types and human cancer patients, and numerous studies in the past decade have recognised their role in contributing to therapeutic resistance against all four pillars of modern cancer treatment, namely surgery, chemotherapy, radiotherapy and immunotherapy. MDSCs suppress anti-tumour immunity through a plethora of mechanisms including the well-characterised arginase 1 (Arg1), inducible nitric oxide synthase (iNOS) and reactive oxygen species (ROS)-mediated pathways, along with several other more recently discovered. MDSCs are largely absent in healthy homeostatic states and predominantly exist in pathological conditions, making them attractive therapeutic targets. However, the lack of specific markers identified for MDSCs to date greatly hindered therapeutic development, and currently there are no clinically approved drugs that specifically target MDSCs. Methods to deplete MDSCs clinically and inhibit their immunosuppressive function will be crucial in advancing cancer treatment and to overcome treatment resistance. This review provides a detailed overview of the current understandings behind the mechanisms of MDSC-mediated suppression of anti-tumour immunity, and discusses potential strategies to target MDSC immunosuppressive mechanisms to overcome therapeutic resistance.

Targeting natural killer cells: from basic biology to clinical application in hematologic malignancies

Natural killer (NK) cell belongs to innate lymphoid cell family that contributes to host immunosurveillance and defense without pre-immunization. Emerging studies have sought to understand the underlying mechanism behind NK cell dysfunction in tumor environments, and provide numerous novel therapeutic targets for tumor treatment. Strategies to enhance functional activities of NK cell have exhibited promising efficacy and favorable tolerance in clinical treatment of tumor patients, such as immune checkpoint blockade (ICB), chimeric antigen receptor NK (CAR-NK) cell, and bi/trispecific killer cell engager (BiKE/TriKE). Immunotherapy targeting NK cell provides remarkable advantages compared to T cell therapy, including a decreased rate of graft versus-host disease (GvHD) and neurotoxicity. Nevertheless, advanced details on how to support the maintenance and function of NK cell to obtain better response rate and longer duration still remain to be elucidated. This review systematically summarizes the profound role of NK cells in tumor development, highlights up-to-date advances and current challenges of therapy targeting NK cell in the clinical treatment of hematologic malignancies.

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.

Current advances in bacteria-based cancer immunotherapy

As the understanding of the tumor microenvironment has deepened, immunotherapy has become a promising strategy for cancer treatment. In contrast to traditional therapies, immunotherapy is more precise and induces fewer adverse effects. In this field, some bacteria have attracted increased attention because of their natural ability to preferentially colonize and proliferate inside tumor sites and exert antitumor effects. Moreover, bacterial components may activate innate and adaptive immunity to resist tumor progression. However, the application of bacteria-based cancer immunotherapy is hampered by potential infection-associated toxicity and unpredictable behavior in vivo. Owing to modern developments in genetic engineering, bacteria can be modified to weaken their toxicity and enhance their ability to eliminate tumor cells or activate the antitumor immune response. This review summarizes the roles of bacteria in the tumor microenvironment, current strategies for bacterial engineering, and the synergistic efficiency of bacteria with other immunotherapies. In addition, the prospects and challenges of the clinical translation of engineered bacteria are summarized.

CD206 modulates the role of M2 macrophages in the origin of metastatic tumors

Tumor metastasis is a key factor affecting the life of patients with malignant tumors. For the past hundred years, scientists have focused on how to kill cancer cells and inhibit their metastasis in vivo, but few breakthroughs have been made. Here we hypothesized a novel mode for cancer metastasis. We show that the phagocytosis of apoptotic tumor cells by macrophages leads to their polarization into the M2 phenotype, and that the expression of stem cell related as well as drug resistance related genes was induced. Therefore, it appears that M2 macrophages have "defected" and have been transformed into the initial "metastatic cancer cells", and thus are the source, at least in part, of the distal tissue tumor metastasis. This assumption is supported by the presence of fused cells with characteristics of both macrophage and tumor cell observed in the peripheral blood and ascites of patients with ovarian cancer. By eliminating the expression of CD206 in M2 macrophages using siRNA, we show that the growth and metastasis of tumors was suppressed using both in vitro cell line and with experimental in vivo mouse models. In summary, we show that M2 macrophages in the blood circulation underwent a "change of loyalty" to become "cancer cells" that transformed into distal tissue metastasis, which could be suppressed by the knockdown of CD206 expression.

Antagonism of regulatory ISGs enhances the anti-melanoma efficacy of STING agonists

Background

Stimulator of Interferon Genes (STING) is a dsDNA sensor that triggers type I inflammatory responses. Recent data from our group and others support the therapeutic efficacy of STING agonists applied intratumorally or systemically in a range of murine tumor models, with treatment benefits associated with tumor vascular normalization and improved immune cell recruitment and function within the tumor microenvironment (TME). However, such interventions are rarely curative and STING agonism coordinately upregulates expression of immunoregulatory interferon-stimulated genes (ISGs) including Arg2, Cox2, Isg15, Nos2, and Pdl1 that may limit treatment benefits. We hypothesized that combined treatment of melanoma-bearing mice with STING agonist ADU-S100 together with antagonists of regulatory ISGs would result in improved control of tumor growth vs. treatment with ADU-S100 alone.

Methods

Mice bearing either B16 (BRAFWTPTENWT) or BPR20 (BRAFV600EPTEN-/-) melanomas were treated with STING agonist ADU-S100 plus various inhibitors of ARG2, COX2, NOS2, PD-L1, or ISG15. Tumor growth control and changes in the TME were evaluated for combination treatment vs ADU-S100 monotherapy by tumor area measurements and flow cytometry/transcriptional profiling, respectively.

Results

In the B16 melanoma model, we noted improved antitumor efficacy only when ADU-S100 was combined with neutralizing/blocking antibodies against PD-L1 or ISG15, but not inhibitors of ARG2, COX2, or NOS2. Conversely, in the BPR20 melanoma model, improved tumor growth control vs. ADU-S100 monotherapy was only observed when combining ADU-S100 with ARG2i, COX2i, and NOS2i, but not anti-PD-L1 or anti-ISG15. Immune changes in the TME associated with improved treatment outcomes were subtle but included increases in proinflammatory innate immune cells and activated CD8+CD69+ T cells and varied between the two tumor models.

Conclusions

These data suggest contextual differences in the relative contributions of individual regulatory ISGs that serve to operationally limit the anti-tumor efficacy of STING agonists which should be considered in future design of novel combination protocols for optimal treatment benefit.

Modulation of macrophage metabolism as an emerging immunotherapy strategy for cancer

Immunometabolism is a burgeoning field of research that investigates how immune cells harness nutrients to drive their growth and functions. Myeloid cells play a pivotal role in tumor biology, yet their metabolic influence on tumor growth and antitumor immune responses remains inadequately understood. This Review explores the metabolic landscape of tumor-associated macrophages, including the immunoregulatory roles of glucose, fatty acids, glutamine, and arginine, alongside the tools used to perturb their metabolism to promote antitumor immunity. The confounding role of metabolic inhibitors on our interpretation of myeloid metabolic phenotypes will also be discussed. A binary metabolic schema is currently used to describe macrophage immunological phenotypes, characterizing inflammatory M1 phenotypes, as supported by glycolysis, and immunosuppressive M2 phenotypes, as supported by oxidative phosphorylation. However, this classification likely underestimates the variety of states in vivo. Understanding these nuances will be critical when developing interventional metabolic strategies. Future research should focus on refining drug specificity and targeted delivery methods to maximize therapeutic efficacy.

Novel orally bioavailable piperidine derivatives as extracellular arginase inhibitors developed by a ring expansion

Arginase is a multifaced enzyme that plays an important role in health and disease being regarded as a therapeutic target for the treatment of various pathological states such as malignancies, asthma, and cardiovascular disease. The discovery of boronic acid-based arginase inhibitors in 1997 revolutionized attempts of medicinal chemistry focused on development of drugs targeting arginase. Unfortunately, these very polar compounds had limitations such as analysis and purification without chromophores, synthetically challenging space, and poor oral bioavailability. Herein, we present a novel class of boronic acid-based arginase inhibitors which are piperidine derivatives exhibiting a different pharmacological profile compared to our drug candidate in cancer immunotherapy -OATD-02 - dual ARG1/2 inhibitor with high intracellular activity. Compounds from this new series show low intracellular activity, hence they can inhibit mainly extracellular arginase, providing different therapeutic space compared to a dual intracellular ARG1/2 inhibitor. The disclosed series showed good inhibitory potential towards arginase enzyme in vitro (IC50 up to 160 nM), favorable pharmacokinetics in animal models, and encouraging preliminary in vitro and in vivo tolerability. Compounds from the new series have moderate-to-high oral bioavailability (up to 66 %) and moderate clearance in vivo. Herein we describe the development and optimization of the synthesis of the new class of boronic acid-based arginase inhibitors via a ring expansion approach starting from the inexpensive chirality source (d-hydroxyproline). This upgraded methodology facilitated a gram-scale delivery of the final compound and eliminated the need for costly and time-consuming chiral resolution.

Advances in macrophage and T cell metabolic reprogramming and immunotherapy in the tumor microenvironment

Macrophages and T cells in the tumor microenvironment (TME) play an important role in tumorigenesis and progression. However, TME is also characterized by metabolic reprogramming, which may affect macrophage and metabolic activity of T cells and promote tumor escape. Immunotherapy is an approach to fight tumors by stimulating the immune system in the host, but requires support and modulation of cellular metabolism. In this process, the metabolic roles of macrophages and T cells become increasingly important, and their metabolic status and interactions play a critical role in the success of immunotherapy. Therefore, understanding the metabolic state of T cells and macrophages in the TME and the impact of metabolic reprogramming on tumor therapy will help optimize subsequent immunotherapy strategies.

Amino acid metabolism in tumor biology and therapy

Amino acid metabolism plays important roles in tumor biology and tumor therapy. Accumulating evidence has shown that amino acids contribute to tumorigenesis and tumor immunity by acting as nutrients, signaling molecules, and could also regulate gene transcription and epigenetic modification. Therefore, targeting amino acid metabolism will provide new ideas for tumor treatment and become an important therapeutic approach after surgery, radiotherapy, and chemotherapy. In this review, we systematically summarize the recent progress of amino acid metabolism in malignancy and their interaction with signal pathways as well as their effect on tumor microenvironment and epigenetic modification. Collectively, we also highlight the potential therapeutic application and future expectation.

Metabolic regulation of tumor-associated macrophage heterogeneity: insights into the tumor microenvironment and immunotherapeutic opportunities

Tumor-associated macrophages (TAMs) are a heterogeneous population that play diverse functions in tumors. Their identity is determined not only by intrinsic factors, such as origins and transcription factors, but also by external signals from the tumor microenvironment (TME), such as inflammatory signals and metabolic reprogramming. Metabolic reprogramming has rendered TAM to exhibit a spectrum of activities ranging from pro-tumorigenic to anti-tumorigenic, closely associated with tumor progression and clinical prognosis. This review implicates the diversity of TAM phenotypes and functions, how this heterogeneity has been re-evaluated with the advent of single-cell technologies, and the impact of TME metabolic reprogramming on TAMs. We also review current therapies targeting TAM metabolism and offer new insights for TAM-dependent anti-tumor immunotherapy by focusing on the critical role of different metabolic programs in TAMs.

Myeloid cell-derived creatine in the hypoxic niche promotes glioblastoma growth

Glioblastoma (GBM) is a malignancy dominated by the infiltration of tumor-associated myeloid cells (TAMCs). Examination of TAMC metabolic phenotypes in mouse models and patients with GBM identified the de novo creatine metabolic pathway as a hallmark of TAMCs. Multi-omics analyses revealed that TAMCs surround the hypoxic peri-necrotic regions of GBM and express the creatine metabolic enzyme glycine amidinotransferase (GATM). Conversely, GBM cells located within these same regions are uniquely specific in expressing the creatine transporter (SLC6A8). We hypothesized that TAMCs provide creatine to tumors, promoting GBM progression. Isotopic tracing demonstrated that TAMC-secreted creatine is taken up by tumor cells. Creatine supplementation protected tumors from hypoxia-induced stress, which was abrogated with genetic ablation or pharmacologic inhibition of SLC6A8. Lastly, inhibition of creatine transport using the clinically relevant compound, RGX-202-01, blunted tumor growth and enhanced radiation therapy in vivo. This work highlights that myeloid-to-tumor transfer of creatine promotes tumor growth in the hypoxic niche.

DDR2-regulated arginase activity in ovarian cancer-associated fibroblasts promotes collagen production and tumor progression

Ovarian cancer has poor survival outcomes particularly for advanced stage, metastatic disease. Metastasis is promoted by interactions of stromal cells, such as cancer-associated fibroblasts (CAFs) in the tumor microenvironment (TME), with tumor cells. CAFs play a key role in tumor progression by remodeling the TME and extracellular matrix (ECM) to result in a more permissive environment for tumor progression. It has been shown that fibroblasts, in particular myofibroblasts, utilize metabolism to support ECM remodeling. However, the intricate mechanisms by which CAFs support collagen production and tumor progression are poorly understood. In this study, we show that the fibrillar collagen receptor, Discoidin Domain Receptor 2 (DDR2), promotes collagen production in human and mouse omental CAFs through arginase activity. CAFs with high DDR2 or arginase promote tumor colonization in the omentum. In addition, DDR2-depleted CAFs had decreased ornithine levels leading to decreased collagen production and polyamine levels compared to WT control CAFs. Tumor cell invasion was decreased in the presence CAF conditioned media (CM) depleted of DDR2 or arginase-1, and this invasion defect was rescued in the presence of CM from DDR2-depleted CAFs that constitutively overexpressed arginase-1. Similarly, the addition of exogenous polyamines to CM from DDR2-depleted CAFs led to increased tumor cell invasion. We detected SNAI1 protein at the promoter region of the arginase-1 gene, and DDR2-depleted CAFs had decreased levels of SNAI1 protein at the arginase-1 promoter region. Furthermore, high stromal arginase-1 expression correlated with poor survival in ovarian cancer patients. These findings highlight how DDR2 regulates collagen production by CAFs in the tumor microenvironment by controlling the transcription of arginase-1, and CAFs are a major source of arginase activity and L-arginine metabolites in ovarian cancer models.

Targeting the myeloid microenvironment in neuroblastoma

Myeloid cells (granulocytes and monocytes/macrophages) play an important role in neuroblastoma. By inducing a complex immunosuppressive network, myeloid cells pose a challenge for the adaptive immune system to eliminate tumor cells, especially in high-risk neuroblastoma. This review first summarizes the pro- and anti-tumorigenic functions of myeloid cells, including granulocytes, monocytes, macrophages, and myeloid-derived suppressor cells (MDSC) during the development and progression of neuroblastoma. Secondly, we discuss how myeloid cells are engaged in the current treatment regimen and explore novel strategies to target these cells in neuroblastoma. These strategies include: (1) engaging myeloid cells as effector cells, (2) ablating myeloid cells or blocking the recruitment of myeloid cells to the tumor microenvironment and (3) reprogramming myeloid cells. Here we describe that despite their immunosuppressive traits, tumor-associated myeloid cells can still be engaged as effector cells, which is clear in anti-GD2 immunotherapy. However, their full potential is not yet reached, and myeloid cell engagement can be enhanced, for example by targeting the CD47/SIRPα axis. Though depletion of myeloid cells or blocking myeloid cell infiltration has been proven effective, this strategy also depletes possible effector cells for immunotherapy from the tumor microenvironment. Therefore, reprogramming of suppressive myeloid cells might be the optimal strategy, which reverses immunosuppressive traits, preserves myeloid cells as effectors of immunotherapy, and subsequently reactivates tumor-infiltrating T cells.

ACAT1 deficiency in myeloid cells promotes glioblastoma progression by enhancing the accumulation of myeloid-derived suppressor cells

Glioblastoma (GBM) is a highly aggressive and lethal brain tumor with an immunosuppressive tumor microenvironment (TME). In this environment, myeloid cells, such as myeloid-derived suppressor cells (MDSCs), play a pivotal role in suppressing antitumor immunity. Lipometabolism is closely related to the function of myeloid cells. Here, our study reports that acetyl-CoA acetyltransferase 1 (ACAT1), the key enzyme of fatty acid oxidation (FAO) and ketogenesis, is significantly downregulated in the MDSCs infiltrated in GBM patients. To investigate the effects of ACAT1 on myeloid cells, we generated mice with myeloid-specific (LyzM-cre) depletion of ACAT1. The results show that these mice exhibited a remarkable accumulation of MDSCs and increased tumor progression both ectopically and orthotopically. The mechanism behind this effect is elevated secretion of C-X-C motif ligand 1 (CXCL1) of macrophages (Mφ). Overall, our findings demonstrate that ACAT1 could serve as a promising drug target for GBM by regulating the function of MDSCs in the TME.

Beyond the horizon: Neutrophils leading the way in the evolution of immunotherapy

Cancer is a complex and dynamic disease, initiated by a multitude of intrinsic mutations and progressed with the assistance of the tissue microenvironment, encompassed by stromal cells including immune cell infiltration. The novel finding that tumors can evade anti-cancer immune functions shaped the field of immunotherapy, which has been a revolutionary approach for the treatment of cancers. However, the development of predominantly T cell-targeted immunotherapy approaches, such as immune checkpoint inhibition, also brought about an accumulation of evidence demonstrating other immune cell drivers of tumor progression, such as innate immune cells and notably, neutrophils. In the past decade, neutrophils have emerged to be primary mediators of multiple cancer types and even in recent years, are gaining attention for their potential use in the next generation of immunotherapies. Here, we review current immunotherapy strategies and thoroughly discuss the roles of neutrophils in cancer and novel neutrophil-targeted methods for treating cancer.

Blockade of EP4 by ASP7657 Modulates Myeloid Cell Differentiation In Vivo and Enhances the Antitumor Effect of Radiotherapy

The tumor microenvironment (TME) is thought to influence the antitumor efficacy of immuno-oncology agents through various products of both tumor and stromal cells. One immune-suppressive factor is prostaglandin E2 (PGE2), a lipid mediator whose biosynthesis is regulated by ubiquitously expressed cyclooxygenase- (COX-) 1 and inducible COX-2. By activating its receptors, PGE2 induces immune suppression to modulate differentiation of myeloid cells into myeloid-derived suppressor cells (MDSCs) rather than dendritic cells (DCs). Pharmacological blockade of prostaglandin E receptor 4 (EP4) causes a decrease in MDSCs, reprogramming of macrophage polarization, and increase in tumor-infiltrated T cells, leading to enhancement of antitumor immunity in preclinical models. Here, we report the effects of the highly potent EP4 antagonist ASP7657 on the DC population in tumor and antitumor immune activation in an immunocompetent mouse tumor model. Oral administration of ASP7657 inhibited tumor growth, which was accompanied by an increase in intratumor DC and CD8+ T cell populations and a decrease in the M-MDSC population in a CT26 immunocompetent mouse model. The antitumor activity of ASP7657 was dependent on CD8+ T cells and enhanced when combined with an antiprogrammed cell death-1 (PD-1) antibody. Notably, ASP7657 also significantly enhanced the antitumor efficacy of radiotherapy in an anti-PD-1 antibody refractory model. These results indicate that the therapeutic potential of ASP7657 arises via upregulation of DCs and subsequent CD8+ T cell activation in addition to suppression of MDSCs in mouse models and that combining EP4 antagonists with radiotherapy or an anti-PD-1 antibody can improve antitumor efficacy.

Amino acid metabolism reprogramming: shedding new light on T cell anti-tumor immunity

Metabolic reprogramming of amino acids has been increasingly recognized to initiate and fuel tumorigenesis and survival. Therefore, there is emerging interest in the application of amino acid metabolic strategies in antitumor therapy. Tremendous efforts have been made to develop amino acid metabolic node interventions such as amino acid antagonists and targeting amino acid transporters, key enzymes of amino acid metabolism, and common downstream pathways of amino acid metabolism. In addition to playing an essential role in sustaining tumor growth, new technologies and studies has revealed amino acid metabolic reprograming to have wide implications in the regulation of antitumor immune responses. Specifically, extensive crosstalk between amino acid metabolism and T cell immunity has been reported. Tumor cells can inhibit T cell immunity by depleting amino acids in the microenvironment through nutrient competition, and toxic metabolites of amino acids can also inhibit T cell function. In addition, amino acids can interfere with T cells by regulating glucose and lipid metabolism. This crucial crosstalk inspires the exploitation of novel strategies of immunotherapy enhancement and combination, owing to the unprecedented benefits of immunotherapy and the limited population it can benefit. Herein, we review recent findings related to the crosstalk between amino acid metabolism and T cell immunity. We also describe possible approaches to intervene in amino acid metabolic pathways by targeting various signaling nodes. Novel efforts to combine with and unleash potential immunotherapy are also discussed. Hopefully, some strategies that take the lead in the pipeline may soon be used for the common good.

Boron in cancer therapeutics: An overview

Boron has become a crucial weapon in anticancer research due to its significant intervention in cell proliferation. Being an excellent bio-isosteric replacement of carbon, it has modulated the anticancer efficacy of various molecules in the development pipeline. It has elicited promising results through interactions with various therapeutic targets such as HIF-1α, steroid sulfatase, arginase, proteasome, etc. Since boron liberates alpha particles, it has a wide-scale application in Boron Neutron Capture therapy (BNCT), a radiotherapy that demonstrates selectivity towards cancer cells due to high boron uptake capacity. Significant advances in the medicinal chemistry of boronated compounds, such as boronated sugars, natural/unnatural amino acids, boronated DNA binders, etc., have been reported over the past few years as BNCT agents. In addition, boronated nanoparticles have assisted the field of bio-nano medicines by their usage in radiotherapy. This review exclusively focuses on the medicinal chemistry aspects, radiotherapeutic, and chemotherapeutic aspects of boron in cancer therapeutics. Emphasis is also given on the mechanism of action along with advantages over conventional therapies.

Prognostic Biomarkers in Pituitary Tumours: A Systematic Review

Pituitary tumours (PTs) are the second most common intracranial tumour. Although the majority show benign behaviour, they may exert aggressive behaviour and can be resistant to treatment. The aim of this review is to report the recently identified biomarkers that might have possible prognostic value. Studies evaluating potentially prognostic biomarkers or a therapeutic target in invasive/recurrent PTs compared with either non-invasive or non-recurrent PTs or normal pituitaries are included in this review. In the 28 included studies, more than 911 PTs were evaluated. A systematic search identified the expression of a number of biomarkers that may be positively correlated with disease recurrence or invasion in PT, grouped according to role: (1) insensitivity to anti-growth signals: minichromosome maintenance protein 7; (2) evasion of the immune system: cyclooxygenase 2, arginase 1, programmed cell death protein 1 (PD-1)/programmed death ligand 2, cluster of differentiation (CD) 80/CD86; (3) sustained angiogenesis: endothelial cell-specific molecule, fibroblast growth factor receptor, matrix metalloproteinase 9, pituitary tumour transforming gene; (4) self-sufficiency in growth signals: epidermal growth factor receptor; and (5) tissue invasion: matrix metalloproteinase 9, fascin protein. Biomarkers with a negative correlation with disease recurrence or invasion include: (1) insensitivity to anti-growth signals: transforming growth factor β1, Smad proteins; (2) sustained angiogenesis: tissue inhibitor of metalloproteinase 1; (3) tissue invasion: Wnt inhibitory factor 1; and (4) miscellaneous: co-expression of glial fibrillary acidic protein and cytokeratin, and oestrogen receptors α36 and α66. PD-1/programmed cell death ligand 1 showed no clear association with invasion or recurrence, while cyclin A, cytotoxic T lymphocyte-associated protein 4, S100 protein, ephrin receptor, galectin-3 , neural cell adhesion molecule, protein tyrosine phosphatase 4A3 and steroidogenic factor 1 had no association with invasion or recurrence of PT. With the aim to develop a more personalized approach to the treatment of PT, and because of the limited number of molecular targets currently studied in the context of recurrent PT and invasion, a better understanding of the most relevant of these biomarkers by well-d esigned interventional studies will lead to a better understanding of the molecular profile of PT. This should also meet the increased need of treatable molecular targets.

Neutrophil swarms containing myeloid-derived suppressor cells are crucial for limiting oral mucosal infection by C. albicans

Oral mucosal colonization by C. albicans (Ca) is benign in healthy people but progresses to deeper infection known as oropharyngeal candidiasis (OPC) that may become disseminated when combined with immunosuppression. Cortisone-induced immunosuppression is a well-known risk factor for OPC, however the mechanism by which it permits infection is poorly understood. Neutrophils are the primary early sentinels preventing invasive fungal growth, and here we identify that in vivo neutrophil functional complexes known as swarms are crucial for preventing Ca invasion which are disrupted by cortisone. Neutrophil swarm function required leukotriene B4 receptor 1 (BLT1) expression, and swarms were further characterized by peripheral association of polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs) showing that OPC recruits PMN-MDSCs to this site of infection. Furthermore, PMN-MDSCs associated with Ca hyphae had no direct antifungal effect but showed prolonged survival times and increased autophagy. Thus in vivo neutrophil swarms are complex structures with spatially associated PMN-MDSCs that likely contribute immunoregulatory functions to resolve OPC. These swarm structures have an important function in preventing deep invasion by Ca within the oral mucosa and represent a mechanism for increased disease severity under immune deficient clinical settings.

Research progress on the role of cationic amino acid transporter (CAT) family members in malignant tumors and immune microenvironment

Amino acids are essential for the survival of all living organisms and living cells. Amino acid transporters mediate the transport and absorption of amino acids, and the dysfunction of these proteins can induce human diseases. Cationic amino acid transporters (CAT family, SLC7A1-4, and SLC7A14) are considered to be a group of transmembrane transporters, of which SLC7A1-3 are essential for arginine transport in mammals. Numerous studies have shown that CAT family-mediated arginine transport is involved in signal crosstalk between malignant tumor cells and immune cells, especially T cells. The modulation of extracellular arginine concentration has entered a number of clinical trials and achieved certain therapeutic effects. Here, we review the role of CAT family on tumor cells and immune infiltrating cells in malignant tumors and explore the therapeutic strategies to interfere with extracellular arginine concentration, to elaborate its application prospects. CAT family members may be used as biomarkers for certain cancer entities and might be included in new ideas for immunotherapy of malignant tumors.

Functional polarization of tumor-associated macrophages dictated by metabolic reprogramming

Macrophages are highly plastic in different tissues and can differentiate into functional subpopulations under different stimuli. Tumor-associated macrophages (TAMs) are one of the most important innate immune cells implicated in the establishment of an immunosuppressive tumor microenvironment (TME). Recent evidence pinpoints the critical role of metabolic reprogramming in dictating pro-tumorigenic functions of TAMs. Both tumor cells and macrophages undergo metabolic reprogramming to meet energy demands in the TME. Understanding the metabolic rewiring in TAMs can shed light on immune escape mechanisms and provide insights into repolarizing TAMs towards anti-tumorigenic function. Here, we discuss how metabolism impinges on the functional divergence of macrophages and its relevance to macrophage polarization in the TME.

Arginase-1 promotes lens epithelial-to-mesenchymal transition in different models of anterior subcapsular cataract

BACKGROUND

Arginase-1 (ARG1) promotes collagen synthesis and cell proliferation. ARG1 is highly expressed in various tumour cells. The mechanisms of ARG1 in epithelial-to-mesenchymal transition (EMT)-associated cataracts were studied herein.

METHODS

C57BL/6 mice, a human lens epithelial cell line (HLEC-SRA01/04), and human lens capsule samples were used in this study. The right lens anterior capsule of the mouse eye was punctured through the central cornea with a 26-gauge hypodermic needle. Human lens epithelial cells (HLECs) were transfected with ARG1-targeted (siARG1) or negative control siRNA (siNC). For gene overexpression, HLECs were transfected with a plasmid bearing the ARG1 coding sequence or an empty vector. Medium containing 0.2% serum with or without transforming growth factor beta-2 (TGF-β2) was added for 6 or 24 h to detect mRNA or protein, respectively. The expression of related genes was measured by quantitative real-time polymerase chain reaction (RT-qPCR), western blotting, and immunohistochemical staining. Transwell assays and wound healing assays were used to determine cell migration. Cell proliferation, superoxide levels, nitric oxide (NO) levels, and arginase activity were estimated using Cell Counting Kit-8 assays, a superoxide assay kit, an NO assay kit, and an arginase activity kit.

RESULTS

ARG1, alpha-smooth muscle actin (α-SMA), fibronectin, and Ki67 expression increased after lens capsular injury, while zonula occludens-1 (ZO-1) expression decreased. Fibronectin and collagen type I alpha1 chain (collagen 1A1) expression increased, and cell migration increased significantly in ARG1-overexpressing HLECs compared with those transfected with an empty vector after TGF-β2 treatment. These effects were reversed by ARG1 knockdown. The arginase-related pathway plays an important role in EMT. mRNAs of enzymes of the arginase-related pathway were highly expressed after ARG1 overexpression. ARG1 knockdown suppressed these expression changes. Numidargistat (CB-1158) dihydrochloride (CB-1158), an ARG1 inhibitor, suppressed TGF-β2-induced anterior subcapsular cataract (ASC) by reducing the proliferation of lens epithelial cells (LECs) and decreasing fibronectin, α-SMA, collagen 1A1, and vimentin expression. Compared with that in nonanterior subcapsular cataract (non-ASC) patients, the expression of ARG1, collagen 1A1, vimentin, fibronectin, and Ki67 was markedly increased in ASC patients.

CONCLUSIONS

ARG1 can regulate EMT in EMT-associated cataracts. Based on the pathogenesis of ASC, these findings are expected to provide new therapeutic strategies for patients.

Innate immune response restarts adaptive immune response in tumors

The imbalance of immune response plays a crucial role in the development of diseases, including glioblastoma. It is essential to comprehend how the innate immune system detects tumors and pathogens. Endosomal and cytoplasmic sensors can identify diverse cancer cell antigens, triggering the production of type I interferon and pro-inflammatory cytokines. This, in turn, stimulates interferon stimulating genes, enhancing the presentation of cancer antigens, and promoting T cell recognition and destruction of cancer cells. While RNA and DNA sensing of tumors and pathogens typically involve different receptors and adapters, their interaction can activate adaptive immune response mechanisms. This review highlights the similarity in RNA and DNA sensing mechanisms in the innate immunity of both tumors and pathogens. The aim is to enhance the anti-tumor innate immune response, identify regions of the tumor that are not responsive to treatment, and explore new targets to improve the response to conventional tumor therapy and immunotherapy.

Amino acid metabolism in health and disease

Amino acids are the building blocks of protein synthesis. They are structural elements and energy sources of cells necessary for normal cell growth, differentiation and function. Amino acid metabolism disorders have been linked with a number of pathological conditions, including metabolic diseases, cardiovascular diseases, immune diseases, and cancer. In the case of tumors, alterations in amino acid metabolism can be used not only as clinical indicators of cancer progression but also as therapeutic strategies. Since the growth and development of tumors depend on the intake of foreign amino acids, more and more studies have targeted the metabolism of tumor-related amino acids to selectively kill tumor cells. Furthermore, immune-related studies have confirmed that amino acid metabolism regulates the function of effector T cells and regulatory T cells, affecting the function of immune cells. Therefore, studying amino acid metabolism associated with disease and identifying targets in amino acid metabolic pathways may be helpful for disease treatment. This article mainly focuses on the research of amino acid metabolism in tumor-oriented diseases, and reviews the research and clinical research progress of metabolic diseases, cardiovascular diseases and immune-related diseases related to amino acid metabolism, in order to provide theoretical basis for targeted therapy of amino acid metabolism.