Metabolic influence on the differentiation of suppressive myeloid cells in cancer

Association between Immune Checkpoint Inhibitors and Atherosclerotic Cardiovascular Disease Risk: Another Brick in the Wall

In recent years, immune checkpoint inhibitors have significantly changed the field of oncology, emerging as first-line treatment, either alone or in combination with other regimens, for numerous malignancies, improving overall survival and progression-free survival in these patients. However, immune checkpoint inhibitors might also cause severe or fatal immune-related adverse events, including adverse cardiovascular events. Initially, myocarditis was recognized as the main immune checkpoint inhibitor-related cardiac event, but our knowledge of other potential immune-related cardiovascular adverse events continues to broaden. Recently, preclinical and clinical data seem to support an association between immune checkpoint inhibitors and accelerated atherosclerosis as well as atherosclerotic cardiovascular events such as cardiac ischemic disease, stroke, and peripheral artery disease. In this review, by offering a comprehensive overview of the pivotal role of inflammation in atherosclerosis, we focus on the potential molecular pathways underlying the effects of immune checkpoint inhibitors on cardiovascular diseases. Moreover, we provide an overview of therapeutic strategies for cancer patients undergoing immunotherapy to prevent the development of cardiovascular diseases.

Cuproptosis-related lncRNAs are correlated with tumour metabolism and immune microenvironment and predict prognosis in pancreatic cancer patients

Cuproptosis is a novel cell death pathway, and the regulatory mechanism in pancreatic cancer (PC) is unclear. The authors aimed to figure out whether cuproptosis-related lncRNAs (CRLs) could predict prognosis in PC and the underlying mechanism. First, the prognostic model based on seven CRLs screened by the least absolute shrinkage and selection operator Cox analysis was constructed. Following this, the risk score was calculated for pancreatic cancer patients and divided patients into high and low-risk groups. In our prognostic model, PC patients with higher risk scores had poorer outcomes. Based on several prognostic features, a predictive nomogram was established. Furthermore, the functional enrichment analysis of differentially expressed genes between risk groups was performed, indicating that endocrine and metabolic pathways were potential regulatory pathways between risk groups. TP53, KRAS, CDKN2A, and SMAD4 were dominant mutated genes in the high-risk group and tumour mutational burden was positively correlated with the risk score. Finally, the tumour immune landscape indicated patients in the high-risk group were more immunosuppressive than that in the low-risk group, with lower infiltration of CD8+ T cells and higher M2 macrophages. Above all, CRLs can be applied to predict PC prognosis, which is closely correlated with the tumour metabolism and immune microenvironment.

Phenotypic and functional heterogeneity of monocytes in health and cancer in the era of high dimensional technologies

Monocytes have been traditionally classified in three discrete subsets, which can participate in the immune responses as effector cells or as precursors of myeloid-derived cells in circulation and tissues. However, recent advances in single-cell omics have revealed unprecedented phenotypic and functional heterogeneity that goes well beyond the three conventional monocytic subsets and propose a more fluid differentiation model. This novel concept does not only apply to the monocytes in circulation but also at the tissue site. Consequently, the binary model proposed for differentiating monocyte into M1 and M2 macrophages has been recently challenged by a spectrum model that more realistically mirrors the heterogeneous cues in inflammatory conditions. This review describes the latest results on the high dimensional characterization of monocytes and monocyte-derived myeloid cells in steady state and cancer. We discuss how environmental cues and monocyte-intrinsic properties may affect their differentiation toward specific functional and phenotypic subsets, the causes of monocyte expansion and reduction in cancer, their metabolic requirements, and the potential effect on tumor immunity.

Post-treatment serum triglyceride: An effective biomarker for body fat mass and overall survival in esophageal squamous cell cancer patients treated with chemoradiotherapy

OBJECTIVES

Although lipids have been assessed for their possible roles in cancer survival prediction, studies on the association between serum triglyceride (TG) levels and the prognosis of esophageal squamous cell carcinoma (ESCC) patients are limited. This study aimed to evaluate whether serum TG is associated with outcomes in patients with ESCC and investigate any interaction between serum TG and clinical parameters, especially body fat mass.

MATERIALS AND METHODS

We conducted a prospective case study on patients diagnosed with ESCC between March 2012 and November 2018. We measured patients' serum TG levels before and after treatment. The association between serum TG and overall survival (OS) was evaluated using hazard ratios. We sought to determine a threshold point using optimal stratification. Survival analysis was performed using Kaplan-Meier curves and a Cox proportional hazards model.

RESULTS

Of the 257 participants diagnosed with ESCC, 200 (77.8%) were men. Median follow-up time was 22.4 months (range 3.3-92.4 months). Using univariate Cox proportional hazard analysis and subsequent multivariate analysis, post-TG levels, Karnofsky performance scores, T stages, and chemotherapy cycles were shown to be independent prognostic factors for OS (p < 0.05). The post-TG cut-off point to best classify patients with respect to time to mortality was 1.47 mmol/L. A post-TG level of ≥ 1.47 mmol/L could independently predict a better OS (hazard ratio: 0.55, 95% confidence interval: 0.37-0.79). The associations were consistent across the subtypes of clinical parameters. Furthermore, the post-body mass index, post-subcutaneous adipose tissue area, post-visceral adipose tissue area, post-total adiposity tissue area, and post-total adipose density exhibited a strong positive association with post-TG levels.

CONCLUSION

Post-TG levels were found to be a significant positive prognostic biomarker for body fat mass and OS in ESCC patients.

MDSCs might be "Achilles heel" for eradicating CSCs

During tumor initiation and progression, the complicated role of immune cells in the tumor immune microenvironment remains a concern. Myeloid-derived suppressor cells (MDSCs) are a group of immune cells that originate from the bone marrow and have immunosuppressive potency in various diseases, including cancer. In recent years, the key role of cancer stemness has received increasing attention in cancer development and therapy. Several studies have demonstrated the important regulatory relationship between MDSCs and cancer stem cells (CSCs). However, there is still no clear understanding regarding the complex interacting regulation of tumor malignancy, and current research progress is limited. In this review, we summarize the complicated role of MDSCs in the modulation of cancer stemness, evaluate the mechanism of the relationship between CSCs and MDSCs, and discuss potential strategies for eradicating CSCs with respect to MDSCs.

Impact of Lipid Metabolism on Antitumor Immune Response

Simple Summary

One of the causes of failure of anticancer therapies is the reprogramming of lipid metabolism. Cells of innate and adaptive immunity present in the tumor microenvironment can be affected by this metabolic switch and thus present changes in their anti- or protumor phenotype. In this review, modifications induced by lipid metabolism will be described for innate immune cells, such as macrophages, dendritic cells and MDSCs, and also for adaptive immune cells, such as CD4+ and CD8+ T cells and B cells. Finally, antitumor therapeutic strategies targeting lipid metabolism will be presented.

Abstract

Over the past decade, metabolic reprogramming has been defined as a hallmark of cancer. More recently, a large number of studies have demonstrated that metabolic reprogramming can modulate the differentiation and functions of immune cells, and thus modify the antitumor response. Increasing evidence suggests that modified energy metabolism could be responsible for the failure of antitumor immunity. Indeed, tumor-infiltrating immune cells play a key role in cancer, and metabolic switching in these cells has been shown to help determine their phenotype: tumor suppressive or immune suppressive. Recent studies in the field of immunometabolism focus on metabolic reprogramming in the tumor microenvironment (TME) by targeting innate and adaptive immune cells and their associated anti- or protumor phenotypes. In this review, we discuss the lipid metabolism of immune cells in the TME as well as the effects of lipids; finally, we expose the link between therapies and lipid metabolism.

Immune Checkpoint Therapies and Atherosclerosis: Mechanisms and Clinical Implications: JACC State-of-the-Art Review

Immune checkpoint inhibitor therapy has revolutionized the treatment of advanced malignancies in recent years. Numerous reports have detailed the myriad of possible adverse inflammatory effects of immune checkpoint therapies, including within the cardiovascular system. However, these reports have been largely limited to myocarditis. The critical role of inflammation and adaptive immunity in atherosclerosis has been well characterized in preclinical studies, and several emerging clinical studies indicate a potential role of immune checkpoint targeting therapies in the development and exacerbation of atherosclerosis. In this review, we provide an overview of the role of T-cell immunity in atherogenesis and describe the molecular effects and clinical associations of both approved and investigational immune checkpoint therapy on atherosclerosis. We also highlight the role of cholesterol metabolism in oncogenesis and discuss the implications of these associations on future treatment and monitoring of atherosclerotic cardiovascular disease in the oncologic population receiving immune checkpoint therapy.

Evolution and Targeting of Myeloid Suppressor Cells in Cancer: A Translational Perspective

Simple Summary

Immunotherapy is achieving impressive results in the treatment of several cancers. While the main strategies aim to re-invigorate the specific lymphocyte anti-tumor response, many studies underline that altered myeloid cell frequency and functions can dramatically interfere with the responsiveness to cancer therapies. Therefore, many novel strategies targeting TAMs and MDSCs in combination with classical treatments are under continuous evolution at both pre-clinical and clinical levels, showing encouraging results. Herein, we depict a comprehensive overview of myeloid cell generation and function in a cancer setting, and the most relevant strategies for their targeting that are currently in clinical use or under pre-clinical development.

Abstract

In recent years, the immune system has emerged as a critical regulator of tumor development, progression and dissemination. Advanced therapeutic approaches targeting immune cells are currently under clinical use and improvement for the treatment of patients affected by advanced malignancies. Among these, anti-PD1/PD-L1 and anti-CTLA4 immune checkpoint inhibitors (ICIs) are the most effective immunotherapeutic drugs at present. In spite of these advances, great variability in responses to therapy exists among patients, probably due to the heterogeneity of both cancer cells and immune responses, which manifest in diverse forms in the tumor microenvironment (TME). The variability of the immune profile within TME and its prognostic significance largely depend on the frequency of the infiltrating myeloid cells, which often represent the predominant population, characterized by high phenotypic heterogeneity. The generation of heterogeneous myeloid populations endowed with tumor-promoting activities is typically promoted by growing tumors, indicating the sequential levels of myeloid reprogramming as possible antitumor targets. This work reviews the current knowledge on the events governing protumoral myelopoiesis, analyzing the mechanisms that drive the expansion of major myeloid subsets, as well as their functional properties, and highlighting recent translational strategies for clinical developments.

Divulging the Critical Role of HuR in Pancreatic Cancer as a Therapeutic Target and a Means to Overcome Chemoresistance

Simple Summary

With pancreatic cancer incidence constantly rising, constituting one of the most lethal type of cancers worldwide, the need for discovering novel therapeutic targets and approaches becomes of the utmost importance. Meanwhile, modern eating habits, hyperadiposity, mutational burden affecting core signaling pathways and the unique tumor microenvironment of pancreatic cancer tissues intermingle and form a disease that is lethal and hard to treat. The importance of HuR in pancreatic cancer has repeatedly been observed and represents a key molecule in pancreatic carcinogenesis and chemoresistance. Therefore, creating and obtaining new therapeutic skills against HuR protein could prove to be the answer to pancreatic cancer therapy.

Abstract

Pancreatic cancer is set to become the most lethal and common type of cancer worldwide. This is partly attributed to the mutational burden that affects core signaling pathways and the crosstalk of tumor cells with their surrounding microenvironment, but it is also due to modern eating habits. Hyperadiposity along with the constant rise in metabolic syndrome’s incidence contribute to a state of metaflammation that impacts immune cells and causes them to shift towards an immunosuppressive phenotype that, ultimately, allows tumor cells to evade immune control. Unfortunately, among the conventional therapeutic modalities and the novel therapeutic agents introduced, pancreatic cancer still holds one of the lowest response rates to therapy. Human antigen R (HuR), an RNA binding protein (RBP), has been repeatedly found to be implicated in pancreatic carcinogenesis and chemotherapy resistance through the posttranscriptional binding and regulation of mRNA target genes. Additionally, its overexpression has been linked to adverse clinical outcomes, in terms of tumor grade, stage, lymph node status and metastasis. These properties suggest the prospective role that HuR’s therapeutic targeting can play in facilitating pancreatic neoplasia and could provide the means to overcome chemoresistance.

The Prognostic Role of High Blood Cholesterol in Advanced Cancer Patients Treated With Immune Checkpoint Inhibitors

Immune checkpoint inhibitors (ICI) have improved survival in numerous types of cancer. However, a great number of unselected patients still do not respond to ICI. Moreover, there is a need to identify biomarkers that could predict the prognosis of immunotherapy-treated patients. The aim of our study is to evaluate the prognostic value of baseline plasmatic cholesterol levels in metastatic cancer patients treated with immunotherapy. We retrospectively enrolled advanced cancer patients consecutively treated with ICI at our center between October 2013 and October 2018 to correlate the blood cholesterol level before treatment with overall survival (OS, primary endpoint). The secondary endpoints were the correlation between baseline cholesterol and progression-free survival (PFS), objective response rate, and toxicity (immune-related adverse events). Among 187 patients with availability of baseline plasmatic cholesterol, 58 had cholesterol levels >200 mg/dL. The median age was 70 years. Primary tumors were as follows: non-small cell lung cancer (70.0%), melanoma (15.0%), renal cell carcinoma (9.1%), urothelial cancer (4.6%), head-neck carcinoma (0.9%), and others (0.4%). The median follow-up was 21.3 months. Both OS and PFS were better in patients with high plasmatic cholesterol levels: the median OS was 19.4 versus 5.5 months (P=0.001) and the median PFS was 6.1 versus 2.4 months (P=0.002). The multivariate analysis confirmed the prognostic role of hypercholesterolemia in terms of OS, but not PFS. Hypercholesterolemia was associated with better outcomes in ICI-treated cancer patients and, as an expression of low-grade inflammation state, it could identify tumors more likely to be responsive to immunotherapy.

Diet, Microbiome, and Cancer Immunotherapy-A Comprehensive Review

The immune system plays a key role in cancer suppression. Immunotherapy is widely used as a treatment method in patients with various types of cancer. Immune checkpoint blockade using antibodies, such as anti-PD-1, anti-PD-L1, and anti-CTLA-4, is currently gaining popularity. A systematic literature search was executed, and all available data was summarized. This review shows that specific dietary patterns (such as, e.g., animal-based, vegetarian, or Mediterranean diet) alter the gut microbiome's composition. An appropriate intestinal microbiota structure might modulate the function of human immune system, which affects the bodily anti-cancer response. This paper shows also that specific bacteria species inhabiting the gastrointestinal tract can have a beneficial influence on the efficacy of immunotherapy. Antibiotics weaken gut bacteria and worsen the immune checkpoint blockers' efficacy, whereas a faecal microbiota transplant or probiotics supplementation may help restore bacterial balance in the intestine. Other factors (like vitamins, glucose, or BMI) change the cancer treatment response, as well. This review demonstrates that there is a strong association between one's diet, gut microbiome composition, and the outcome of immunotherapy. However, further investigation on this subject is required.

Obesity-Associated Myeloid Immunosuppressive Cells, Key Players in Cancer Risk and Response to Immunotherapy

Obesity is a risk factor for developing several cancers. The dysfunctional metabolism and chronic activation of inflammatory pathways in obesity create a milieu that supports tumor initiation, progression, and metastasis. Obesity-associated metabolic, endocrine, and inflammatory mediators, besides interacting with cells leading to a malignant transformation, also modify the intrinsic metabolic and functional characteristics of immune myeloid cells. Here, the evidence supporting the hypothesis that obesity metabolically primes and promotes the expansion of myeloid cells with immunosuppressive and pro-oncogenic properties is discussed. In consequence, the accumulation of these cells, such as myeloid-derived suppressor cells and some subtypes of adipose-tissue macrophages, creates a microenvironment conducive to tumor development. In this review, the role of lipids, insulin, and leptin, which are dysregulated in obesity, is emphasized, as well as dietary nutrients in metabolic reprogramming of these myeloid cells. Moreover, emerging evidence indicating that obesity enhances immunotherapy response and hypothesized mechanisms are summarized. Priorities in deeper exploration involving the mechanisms of cross talk between metabolic disorders and myeloid cells related to cancer risk in patients with obesity are highlighted.

Lipid Metabolism in Tumor-Associated Myeloid-Derived Suppressor Cells

Myeloid-derived suppressor cells (MDSCs) are a heterogenous population of myeloid cells with immature phenotypes and immunosuppressive functions. This population of cells has been extensively studied over the past decade owing to an increasing recognition of their pivotal role in pathological conditions including cancers, infectious diseases, sepsis, and autoimmune diseases. Various treatments targeting MDSCs are currently under development or in clinical trials with the aim to restore functional immunity against tumors or pathogens. Recent advances in immune metabolism demonstrate the role of metabolic pathways, especially lipid metabolism, in the differentiation and function of MDSCs in tumor environments. Therefore, a comprehensive understanding of lipid metabolism in MDSCs would facilitate the development of novel therapies against tumors through metabolic reprograming of MDSCs.

The interplay between cholesterol (and other metabolic conditions) and immune-checkpoint immunotherapy: shifting the concept from the "inflamed tumor" to the "inflamed patient"

The predictive ability of metabolic conditions, such as hypercholesterolemia, on the outcome of cancer patients to immune-checkpoint inhibitors (ICIs) therapy, has been recently explored. The reasons for their value in this setting are to be searched in the individual himself more than in his tumor, as the target of the immune-checkpoint blockade is the immune system. The efficacy of ICIs on the tumor may be based on two simple premises: 1) the physiological immune function has been blocked, and 2) the tumor progression (mainly) depends on this block. The metabolic syndrome may represent the epiphenomenon of an "inflamed patient," no longer able of physiological functions required to prevent chronic inflammatory events. The metabolic dysfunction could represent merely "a biomarker" of the patient who satisfies both the two premises reported above. Suggestions from preclinical and translational researches should be transferred in the clinical setting, implementing randomized clinical trials with observational endpoints such as the effect of concomitant drug medications and the impact of blood cholesterol levels and other metabolic conditions on the outcome of ICI treatment.

The role of peroxisome proliferator-activated receptors (PPAR) in immune responses

Peroxisome proliferator-activated receptors (PPARs) are fatty acid-activated transcription factors of nuclear hormone receptor superfamily that regulate energy metabolism. Currently, three PPAR subtypes have been identified: PPARα, PPARγ, and PPARβ/δ. PPARα and PPARδ are highly expressed in oxidative tissues and regulate genes involved in substrate delivery and oxidative phosphorylation (OXPHOS) and regulation of energy homeostasis. In contrast, PPARγ is more important in lipogenesis and lipid synthesis, with highest expression levels in white adipose tissue (WAT). In addition to tissues regulating whole body energy homeostasis, PPARs are expressed in immune cells and have an emerging critical role in immune cell differentiation and fate commitment. In this review, we discuss the actions of PPARs in the function of the innate and the adaptive immune system and their implications in immune-mediated inflammatory conditions.

Implications of metabolism-driven myeloid dysfunctions in cancer therapy

Immune homeostasis is maintained by an adequate balance of myeloid and lymphoid responses. In chronic inflammatory states, including cancer, this balance is lost due to dramatic expansion of myeloid progenitors that fail to mature to functional inflammatory neutrophils, macrophages, and dendritic cells (DCs), thus giving rise to a decline in the antitumor effector lymphoid response. Cancer-related inflammation orchestrates the production of hematopoietic growth factors and cytokines that perpetuate recruitment and activation of myeloid precursors, resulting in unresolved and chronic inflammation. This pathologic inflammation creates profound alterations in the intrinsic cellular metabolism of the myeloid progenitor pool, which is amplified by competition for essential nutrients and by hypoxia-induced metabolic rewiring at the tumor site. Therefore, persistent myelopoiesis and metabolic dysfunctions contribute to the development of cancer, as well as to the severity of a broad range of diseases, including metabolic syndrome and autoimmune and infectious diseases. The aims of this review are to (1) define the metabolic networks implicated in aberrant myelopoiesis observed in cancer patients, (2) discuss the mechanisms underlying these clinical manifestations and the impact of metabolic perturbations on clinical outcomes, and (3) explore new biomarkers and therapeutic strategies to restore immunometabolism and differentiation of myeloid cells towards an effector phenotype to increase host antitumor immunity. We propose that the profound metabolic alterations and associated transcriptional changes triggered by chronic and overactivated immune responses in myeloid cells represent critical factors influencing the balance between therapeutic efficacy and immune-related adverse effects (irAEs) for current therapeutic strategies, including immune checkpoint inhibitor (ICI) therapy.

Predictive role of serum cholesterol and triglycerides in cervical cancer survival

OBJECTIVE

Lipids have been evaluated for their possible role in cancer survival prediction. The aim of the current study was to investigate the prognostic value of lipids on overall survival for stage IB1-IIA2 cervical cancer patients.

METHODS

A retrospective study including cervical cancer patients with early-stage (FIGO 2009 stage IB1-IIA2) disease was conducted from January 2012 to February 2017. Patients with any history of liver disease or other cancers, and patients who took any medications known to influence lipid metabolism, were excluded. We measured various factors in patients' lipid profiles including total cholesterol, triglycerides, high-density lipoprotein, and low-density lipoprotein, and assessed these four parameters together with clinicopathological features to identify the significant prognostic factors for overall survival.

RESULTS

A total of 583 patients with median age 53 (range 25-82) years were included. Among them, 283 (48.5%) patients were in FIGO stage IB1, 44 patients (7.6%) in stage IB2, 189 (32.4%) patients in stage IIA1, and the remaining 67 (11.5%) patients were in stage IIA2. Using univariable Cox proportional hazard analysis and subsequent multivariable analysis, total cholesterol, triglycerides, and pelvic lymph node status were shown to be independent prognostic factors for overall survival (p<0.05 for all). Furthermore, the results of the Kaplan-Meier survival curves showed that both the high total cholesterol group and the high triglycerides group were associated with worse overall survival (p=0.002 and p=0.001, respectively) CONCLUSIONS: Our study showed that total triglycerides and total cholesterol may serve as potential predictors for overall survival in patients with cervical cancer. Cervical cancer patients may benefit from treatments after adjusting their triglycerides and total cholesterol levels.

How to overcome the side effects of tumor immunotherapy

The incidence of cancer is increasing year by year. Cancer has become one of the health threats of modern people. Simply relying on the surgery, chemotherapy or radiotherapy, not only the survival rate is not high, but also the quality of life of patients is not much better. Fortunately, the emergence and rapid development of cancer immunotherapy have brought more and more exciting results. However, when scientists think it is possible to overcome cancer, they find that not all cancer patients can benefit from immunotherapy, that is to say, the overall efficiency of immunotherapy is not high. Drug resistance and side effects of immunotherapy cannot be ignored. In order to overcome these difficulties, scientists continue to improve the strategy of immunotherapy and find that combination therapy can effectively reduce the incidence of drug resistance. They also found that by reprogramming tumor blood vessels, activating ferroptosis, utilizing thioredoxin, FATP2 and other substances, the therapeutic effect can be improved and side effects can be alleviated. This article reviews the principles of immunotherapy, new strategies to overcome drug resistance of cancer immunotherapy, and how to improve the efficacy of immunotherapy and reduce side effects.

Lipid Metabolism and Cancer Immunotherapy: Immunosuppressive Myeloid Cells at the Crossroad

Cancer progression generates a chronic inflammatory state that dramatically influences hematopoiesis, originating different subsets of immune cells that can exert pro- or anti-tumor roles. Commitment towards one of these opposing phenotypes is driven by inflammatory and metabolic stimuli derived from the tumor-microenvironment (TME). Current immunotherapy protocols are based on the reprogramming of both specific and innate immune responses, in order to boost the intrinsic anti-tumoral activity of both compartments. Growing pre-clinical and clinical evidence highlights the key role of metabolism as a major influence on both immune and clinical responses of cancer patients. Indeed, nutrient competition (i.e., amino acids, glucose, fatty acids) between proliferating cancer cells and immune cells, together with inflammatory mediators, drastically affect the functionality of innate and adaptive immune cells, as well as their functional cross-talk. This review discusses new advances on the complex interplay between cancer-related inflammation, myeloid cell differentiation and lipid metabolism, highlighting the therapeutic potential of metabolic interventions as modulators of anticancer immune responses and catalysts of anticancer immunotherapy.

Myelopoiesis, metabolism and therapy: a crucial crossroads in cancer progression

Cancers promote immunological stresses that induce alterations of the myelopoietic output, defined as emergency myelopoiesis, which lead to the generation of different myeloid populations endowed with tumor-promoting activities. New evidence indicates that acquisition of this tumor-promoting phenotype by myeloid cells is the result of a multistep process, encompassing initial events originating into the bone marrow and later steps operating in the tumor microenvironment. The careful characterization of these sequential mechanisms is likely to offer new potential therapeutic opportunities. Here, we describe relevant mechanisms of myeloid cells reprogramming that instate immune dysfunctions and limit effective responses to anticancer therapy and discuss the influence that metabolic events, as well as chemotherapy, elicit on such events.

Myelopoiesis, metabolism and therapy: a crucial crossroads in cancer progression

Cancers promote immunological stresses that induce alterations of the myelopoietic output, defined as emergency myelopoiesis, which lead to the generation of different myeloid populations endowed with tumor-promoting activities. New evidence indicates that acquisition of this tumor-promoting phenotype by myeloid cells is the result of a multistep process, encompassing initial events originating into the bone marrow and later steps operating in the tumor microenvironment. The careful characterization of these sequential mechanisms is likely to offer new potential therapeutic opportunities. Here, we describe relevant mechanisms of myeloid cells reprogramming that instate immune dysfunctions and limit effective responses to anticancer therapy and discuss the influence that metabolic events, as well as chemotherapy, elicit on such events.

AMPK activation inhibits the functions of myeloid-derived suppressor cells (MDSC): impact on cancer and aging

AMP-activated protein kinase (AMPK) has a crucial role not only in the regulation of tissue energy metabolism but it can also control immune responses through its cooperation with immune signaling pathways, thus affecting immunometabolism and the functions of immune cells. It is known that AMPK signaling inhibits the activity of the NF-κB system and thus suppresses pro-inflammatory responses. Interestingly, AMPK activation can inhibit several major immune signaling pathways, e.g., the JAK-STAT, NF-κB, C/EBPβ, CHOP, and HIF-1α pathways, which induce the expansion and activation of myeloid-derived suppressor cells (MDSC). MDSCs induce an immunosuppressive microenvironment in tumors and thus allow the escape of tumor cells from immune surveillance. Chronic inflammation has a key role in the expansion and activation of MDSCs in both tumors and inflammatory disorders. The numbers of MDSCs also significantly increase during the aging process concurrently with the immunosenescence associated with chronic low-grade inflammation. Increased fatty acid oxidation and lactate produced by aerobic glycolysis are important immunometabolic enhancers of MDSC functions. However, it seems that AMPK signaling regulates the functions of MDSCs in a context-dependent manner. Currently, the activators of AMPK signaling are promising drug candidates for cancer therapy and possibly for the extension of healthspan and lifespan. We will describe in detail the AMPK-mediated regulation of the signaling pathways controlling the expansion and activation of immunosuppressive MDSCs. We will propose that the beneficial effects mediated by AMPK activation, e.g., in cancers and the aging process, could be induced by the inhibition of MDSC functions.

Inflammation and Pancreatic Cancer: Focus on Metabolism, Cytokines, and Immunity

Systemic and local chronic inflammation might enhance the risk of pancreatic ductal adenocarcinoma (PDAC), and PDAC-associated inflammatory infiltrate in the tumor microenvironment concurs in enhancing tumor growth and metastasis. Inflammation is closely correlated with immunity, the same immune cell populations contributing to both inflammation and immune response. In the PDAC microenvironment, the inflammatory cell infiltrate is unbalanced towards an immunosuppressive phenotype, with a prevalence of myeloid derived suppressor cells (MDSC), M2 polarized macrophages, and T_reg, over M1 macrophages, dendritic cells, and effector CD4⁺ and CD8⁺ T lymphocytes. The dynamic and continuously evolving cross-talk between inflammatory and cancer cells might be direct and contact-dependent, but it is mainly mediated by soluble and exosomes-carried cytokines. Among these, tumor necrosis factor alpha (TNFα) plays a relevant role in enhancing cancer risk, cancer growth, and cancer-associated cachexia. In this review, we describe the inflammatory cell types, the cytokines, and the mechanisms underlying PDAC risk, growth, and progression, with particular attention on TNFα, also in the light of the potential risks or benefits associated with anti-TNFα treatments.