Metabolic reprogramming of natural killer cells in obesity limits antitumor responses

Metabolic requirements of CD160 expressing memory-like NK cells in Gram-negative bacterial infection

Objective

Unique metabolic requirements accompany the development and functional fates of immune cells. How cellular metabolism is important in natural killer (NK) cells and their memory-like differentiation in bacterial infections remains elusive.

Methods

Here, we utilise our established NK cell memory assay to investigate the metabolic requirement for memory-like NK cell formation and function in response to the Gram-negative intracellular bacteria Burkholderia pseudomallei (BP), the causative agent of melioidosis.

Results

We demonstrate that CD160+ memory-like NK cells upon BP stimulation upregulate glucose and amino acid transporters in a cohort of recovered melioidosis patients which is maintained at least 3-month post-hospital admission. Using an in vitro assay, human BP-specific CD160+ memory-like NK cells show metabolic priming including increased expression of glucose and amino acid transporters with elevated glucose uptake, increased mTOR activation and mitochondrial membrane potential upon BP re-stimulation. Antigen-specific and cytokine-induced IFN-γ production of this memory-like NK cell subset are highly dependent on oxidative phosphorylation (OXPHOS) with some dependency on glycolysis, whereas the formation of CD160+ memory-like NK cells in vitro is dependent on fatty acid oxidation and OXPHOS and further increased by metformin.

Conclusion

This study reveals the link between metabolism and cellular function of memory-like NK cells, which can be exploited for vaccine design and for monitoring protection against Gram-negative bacterial infection.

Adiposity, immunity, and inflammation: interrelationships in health and disease: a report from 24th Annual Harvard Nutrition Obesity Symposium, June 2023

The rapidly evolving field of immunometabolism explores how changes in local immune environments may affect key metabolic and cellular processes, including that of adipose tissue. Importantly, these changes may contribute to low-grade systemic inflammation. In turn, chronic low-grade inflammation affecting adipose tissue may exacerbate the outcome of metabolic diseases. Novel advances in our understanding of immunometabolic processes may critically lead to interventions to reduce disease severity and progression. An important example in this regard relates to obesity, which has a multifaceted effect on immunity, activating the proinflammatory pathways such as the inflammasome and disrupting cellular homeostasis. This multifaceted effect of obesity can be investigated through study of downstream conditions using cellular and systemic investigative techniques. To further explore this field, the National Institutes of Health P30 Nutrition Obesity Research Center at Harvard, in partnership with Harvard Medical School, assembled experts to present at its 24th Annual Symposium entitled "Adiposity, Immunity, and Inflammation: Interrelationships in Health and Disease" on 7 June, 2023. This manuscript seeks to synthesize and present key findings from the symposium, highlighting new research and novel disease-specific advances in the field. Better understanding the interaction between metabolism and immunity offers promising preventative and treatment therapies for obesity-related immunometabolic diseases.

Radiofrequency radiation reshapes tumor immune microenvironment into antitumor phenotype in pulmonary metastatic melanoma by inducing active transformation of tumor-infiltrating CD8+ T and NK cells

Immunosuppression by the tumor microenvironment is a pivotal factor contributing to tumor progression and immunotherapy resistance. Priming the tumor immune microenvironment (TIME) has emerged as a promising strategy for improving the efficacy of cancer immunotherapy. In this study we investigated the effects of noninvasive radiofrequency radiation (RFR) exposure on tumor progression and TIME phenotype, as well as the antitumor potential of PD-1 blockage in a model of pulmonary metastatic melanoma (PMM). Mouse model of PMM was established by tail vein injection of B16F10 cells. From day 3 after injection, the mice were exposed to RFR at an average specific absorption rate of 9.7 W/kg for 1 h per day for 14 days. After RFR exposure, lung tissues were harvested and RNAs were extracted for transcriptome sequencing; PMM-infiltrating immune cells were isolated for single-cell RNA-seq analysis. We showed that RFR exposure significantly impeded PMM progression accompanied by remodeled TIME of PMM via altering the proportion and transcription profile of tumor-infiltrating immune cells. RFR exposure increased the activation and cytotoxicity signatures of tumor-infiltrating CD8+ T cells, particularly in the early activation subset with upregulated genes associated with T cell cytotoxicity. The PD-1 checkpoint pathway was upregulated by RFR exposure in CD8+ T cells. RFR exposure also augmented NK cell subsets with increased cytotoxic characteristics in PMM. RFR exposure enhanced the effector function of tumor-infiltrating CD8+ T cells and NK cells, evidenced by increased expression of cytotoxic molecules. RFR-induced inhibition of PMM growth was mediated by RFR-activated CD8+ T cells and NK cells. We conclude that noninvasive RFR exposure induces antitumor remodeling of the TIME, leading to inhibition of tumor progression, which provides a promising novel strategy for TIME priming and potential combination with cancer immunotherapy.

Tumor cells impair immunological synapse formation via central nervous system-enriched metabolite

Tumors employ various strategies to evade immune surveillance. Central nervous system (CNS) has multiple features to restrain immune response. Whether tumors and CNS share similar programs of immunosuppression is elusive. Here, we analyze multi-omics data of tumors from HER2+ breast cancer patients receiving trastuzumab and anti-PD-L1 antibody and find that CNS-enriched N-acetyltransferase 8-like (NAT8L) and its metabolite N-acetylaspartate (NAA) are overexpressed in resistant tumors. In CNS, NAA is released during brain inflammation. NAT8L attenuates brain inflammation and impairs anti-tumor immunity by inhibiting cytotoxicity of natural killer (NK) cells and CD8+ T cells via NAA. NAA disrupts the formation of immunological synapse by promoting PCAF-induced acetylation of lamin A-K542, which inhibits the integration between lamin A and SUN2 and impairs polarization of lytic granules. We uncover that tumor cells mimic the anti-inflammatory mechanism of CNS to evade anti-tumor immunity and NAT8L is a potential target to enhance efficacy of anti-cancer agents.

NK cells as powerful therapeutic tool in cancer immunotherapy

BACKGROUND

Natural killer (NK) cells have gained considerable attention and hold great potential for their application in tumor immunotherapy. This is mainly due to their MHC-unrestricted and pan-specific recognition capabilities, as well as their ability to rapidly respond to and eliminate target cells. To artificially generate therapeutic NK cells, various materials can be utilized, such as peripheral blood mononuclear cells (PBMCs), umbilical cord blood (UCB), induced pluripotent stem cells (iPSCs), and NK cell lines. Exploiting the therapeutic potential of NK cells to treat tumors through in vivo and in vitro therapeutic modalities has yielded positive therapeutic results.

CONCLUSION

This review provides a comprehensive description of NK cell therapeutic approaches for tumors and discusses the current problems associated with these therapeutic approaches and the prospects of NK cell therapy for tumors.

Immune signature and therapeutic approach of natural killer cell in chronic liver disease and hepatocellular carcinoma

Natural killer (NK) cells are one of the key members of innate immunity that predominantly reside in the liver, potentiating immune responses against viral infections or malignant tumors. It has been reported that changes in cell numbers and function of NK cells are associated with the development and progression of chronic liver diseases (CLDs) including non-alcoholic fatty liver disease, alcoholic liver disease, and chronic viral hepatitis. Also, it is known that the crosstalk between NK cells and hepatic stellate cells plays an important role in liver fibrosis and cirrhosis. In particular, the impaired functions of NK cells observed in CLDs consequently contribute to occurrence and progression of hepatocellular carcinoma (HCC). Chronic infections by hepatitis B or C viruses counteract the anti-tumor immunity of the host by producing the sheddases. Soluble major histocompatibility complex class I polypeptide-related sequence A (sMICA), released from the cell surfaces by sheddases, disrupts the interaction and affects the function of NK cells. Recently, the MICA/B-NK stimulatory receptor NK group 2 member D (NKG2D) axis has been extensively studied in HCC. HCC patients with low membrane-bound MICA or high sMICA concentration have been associated with poor prognosis. Therefore, reversing the sMICA-mediated downregulation of NKG2D has been proposed as an attractive strategy to enhance both innate and adaptive immune responses against HCC. This review aims to summarize recent studies on NK cell immune signatures and its roles in CLD and hepatocellular carcinogenesis and discusses the therapeutic approaches of MICA/B-NKG2D-based or NK cell-based immunotherapy for HCC.

Potential roles of sex-linked differences in obesity and cancer immunotherapy: revisiting the obesity paradox

Obesity, a condition of excess adiposity usually defined by a BMI > 30, can have profound effects on both metabolism and immunity, connecting the condition with a broad range of diseases, including cancer and negative outcomes. Obesity and cancer have been associated with increased incidence, progression, and poorer outcomes of multiple cancer types in part due to the pro-inflammatory state that arises. Surprisingly, obesity has also recently been demonstrated in both preclinical models and clinical outcomes to be associated with improved response to immune checkpoint inhibition (ICI). These observations have laid the foundation for what has been termed the "obesity paradox". The mechanisms underlying these augmented immunotherapy responses are still unclear given the pleiotropic effects obesity exerts on cells and tissues. Other important variables such as age and sex are being examined as further affecting the obesity effect. Sex-linked factors exert significant influences on obesity biology, metabolism as well as differential effects of different immune cell-types. Age can be another confounding factor contributing to the effects on both sex-linked changes, immune status, and obesity. This review aims to revisit the current body of literature describing the immune and metabolic changes mediated by obesity, the role of obesity on cancer immunotherapy, and to highlight questions on how sex-linked differences may influence obesity and immunotherapy outcome.

Metabolic rewiring and communication in cancer immunity

The immune system shapes tumor development and progression. Although immunotherapy has transformed cancer treatment, its overall efficacy remains limited, underscoring the need to uncover mechanisms to improve therapeutic effects. Metabolism-associated processes, including intracellular metabolic reprogramming and intercellular metabolic crosstalk, are emerging as instructive signals for anti-tumor immunity. Here, we first summarize the roles of intracellular metabolic pathways in controlling immune cell function in the tumor microenvironment. How intercellular metabolic communication regulates anti-tumor immunity, and the impact of metabolites or nutrients on signaling events, are also discussed. We then describe how targeting metabolic pathways in tumor cells or intratumoral immune cells or via nutrient-based interventions may boost cancer immunotherapies. Finally, we conclude with discussions on profiling and functional perturbation methods of metabolic activity in intratumoral immune cells, and perspectives on future directions. Uncovering the mechanisms for metabolic rewiring and communication in the tumor microenvironment may enable development of novel cancer immunotherapies.

Persistence of a Skewed Repertoire of NK Cells in People with HIV-1 on Long-Term Antiretroviral Therapy

HIV-1 infection greatly alters the NK cell phenotypic and functional repertoire. This is highlighted by the expansion of a rare population of FcRγ- NK cells exhibiting characteristics of traditional immunologic memory in people with HIV (PWH). Although current antiretroviral therapy (ART) effectively controls HIV-1 viremia and disease progression, its impact on HIV-1-associated NK cell abnormalities remains unclear. To address this, we performed a longitudinal analysis detailing conventional and memory-like NK cell characteristics in n = 60 PWH during the first 4 y of ART. Throughout this regimen, a skewed repertoire of cytokine unresponsive FcRγ- memory-like NK cells persisted and accompanied an overall increase in NK surface expression of CD57 and KLRG1, suggestive of progression toward immune senescence. These traits were linked to elevated serum inflammatory biomarkers and increasing Ab titers to human CMV, with human CMV viremia detected in approximately one-third of PWH at years 1-4 of ART. Interestingly, 40% of PWH displayed atypical NK cell subsets, representing intermediate stages of NK-poiesis based on single-cell multiomic trajectory analysis. Our findings indicate that NK cell irregularities persist in PWH despite long-term ART, underscoring the need to better understand the causative mechanisms that prevent full restoration of immune health in PWH.

Impact of siRNA-Mediated Cofilin-1 Knockdown and Obesity Associated Microenvironment on the Motility of Natural Killer Cells

The anti-tumor capacity of natural killer (NK) cells heavily relies on their ability to migrate towards their target cells. This process is based on dynamic actinrearrangement, so-called actin treadmilling, andis tightly regulated by proteins such as cofilin-1. The aim of the present study was to identify the role of cofilin-1 (CFL-1) in the migratory behavior of NK cells and to investigate a possible impact of an obesity-associated micromilieu on these cells, as it is known that obesity correlates with various impaired NK cell functions. CFL-1 was knocked-down via transfection of NK-92 cells with respective siRNAs. Obesity associated micromilieu was mimicked by incubation of NK-92 cells with adipocyte-conditioned medium from human preadipocyte SGBS cells or leptin. Effects on CFL-1 levels, the degree of phosphorylation to the inactive pCFL-1 as well as NK-92 cell motility were analyzed. Surprisingly, siRNA-mediated CFL-1 knockdown led to a significant increase of migration, as determined by enhanced velocity and accumulated distance of migration. No effect on CFL-1 nor pCFL-1 expression levels, proportion of phosphorylation and cell migratory behavior could be demonstrated under the influence of an obesity-associated microenvironment. In conclusion, the results indicate a significant effect of a CFL-1 knockdown on NK cell motility.

Metabolic adaptations determine whether natural killer cells fail or thrive within the tumor microenvironment

Natural Killer (NK) cells are a top contender in the development of adoptive cell therapies for cancer due to their diverse antitumor functions and ability to restrict their activation against nonmalignant cells. Despite their success in hematologic malignancies, NK cell-based therapies have been limited in the context of solid tumors. Tumor cells undergo various metabolic adaptations to sustain the immense energy demands that are needed to support their rapid and uncontrolled proliferation. As a result, the tumor microenvironment (TME) is depleted of nutrients needed to fuel immune cell activity and contains several immunosuppressive metabolites that hinder NK cell antitumor functions. Further, we now know that NK cell metabolic status is a main determining factor of their effector functions. Hence, the ability of NK cells to withstand and adapt to these metabolically hostile conditions is imperative for effective and sustained antitumor activity in the TME. With this in mind, we review the consequences of metabolic hostility in the TME on NK cell metabolism and function. We also discuss tumor-like metabolic programs in NK cell induced by STAT3-mediated expansion that adapt NK cells to thrive in the TME. Finally, we examine how other approaches can be applied to enhance NK cell metabolism in tumors.

MEF2C regulates NK cell effector functions through control of lipid metabolism

Natural killer (NK) cells are a critical first line of defense against viral infection. Rare mutations in a small subset of transcription factors can result in decreased NK cell numbers and function in humans, with an associated increased susceptibility to viral infection. However, our understanding of the specific transcription factors governing mature human NK cell function is limited. Here we use a non-viral CRISPR-Cas9 knockout screen targeting genes encoding 31 transcription factors differentially expressed during human NK cell development. We identify myocyte enhancer factor 2C (MEF2C) as a master regulator of human NK cell functionality ex vivo. MEF2C-haploinsufficient patients and mice displayed defects in NK cell development and effector function, with an increased susceptibility to viral infection. Mechanistically, MEF2C was required for an interleukin (IL)-2- and IL-15-mediated increase in lipid content through regulation of sterol regulatory element-binding protein (SREBP) pathways. Supplementation with oleic acid restored MEF2C-deficient and MEF2C-haploinsufficient patient NK cell cytotoxic function. Therefore, MEF2C is a critical orchestrator of NK cell antiviral immunity by regulating SREBP-mediated lipid metabolism.

Obesity-related glomerulopathy: recent advances in inflammatory mechanisms and related treatments

Obesity-related glomerulopathy, which is an obesity-triggered kidney damage, has become a significant threat to human health. Several studies have recently highlighted the critical role of inflammation in obesity-related glomerulopathy development. Additionally, excess adipose tissue and adipocytes in patients with obesity produce various inflammatory factors that cause systemic low-grade inflammation with consequent damage to vascular endothelial cells, exacerbating glomerular injury. Therefore, we conducted a comprehensive review of obesity-related glomerulopathy and addressed the critical role of obesity-induced chronic inflammation in obesity-related glomerulopathy pathogenesis and progression, which leads to tubular damage and proteinuria, ultimately impairing renal function. The relationship between obesity and obesity-related glomerulopathy is facilitated by a network of various inflammation-associated cells (including macrophages, lymphocytes, and mast cells) and a series of inflammatory mediators (such as tumor necrosis factor α, interleukin 6, leptin, adiponectin, resistin, chemokines, adhesion molecules, and plasminogen activator inhibitor 1) and their inflammatory pathways. Furthermore, we discuss a recently discovered relationship between micronutrients and obesity-related glomerulopathy inflammation and the important role of micronutrients in the body's anti-inflammatory response. Therefore, assessing these inflammatory molecules and pathways will provide a strong theoretical basis for developing therapeutic strategies based on anti-inflammatory effects to prevent or delay the onset of kidney injury.

Chimeric antigen receptor-natural killer cell therapy: current advancements and strategies to overcome challenges

Chimeric antigen receptor-natural killer (CAR-NK) cell therapy is a novel immunotherapy targeting cancer cells via the generation of chimeric antigen receptors on NK cells which recognize specific cancer antigens. CAR-NK cell therapy is gaining attention nowadays owing to the ability of CAR-NK cells to release potent cytotoxicity against cancer cells without side effects such as cytokine release syndrome (CRS), neurotoxicity and graft-versus-host disease (GvHD). CAR-NK cells do not require antigen priming, thus enabling them to be used as "off-the-shelf" therapy. Nonetheless, CAR-NK cell therapy still possesses several challenges in eliminating cancer cells which reside in hypoxic and immunosuppressive tumor microenvironment. Therefore, this review is envisioned to explore the current advancements and limitations of CAR-NK cell therapy as well as discuss strategies to overcome the challenges faced by CAR-NK cell therapy. This review also aims to dissect the current status of clinical trials on CAR-NK cells and future recommendations for improving the effectiveness and safety of CAR-NK cell therapy.

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.

Harnessing innate immune pathways for therapeutic advancement in cancer

The innate immune pathway is receiving increasing attention in cancer therapy. This pathway is ubiquitous across various cell types, not only in innate immune cells but also in adaptive immune cells, tumor cells, and stromal cells. Agonists targeting the innate immune pathway have shown profound changes in the tumor microenvironment (TME) and improved tumor prognosis in preclinical studies. However, to date, the clinical success of drugs targeting the innate immune pathway remains limited. Interestingly, recent studies have shown that activation of the innate immune pathway can paradoxically promote tumor progression. The uncertainty surrounding the therapeutic effectiveness of targeted drugs for the innate immune pathway is a critical issue that needs immediate investigation. In this review, we observe that the role of the innate immune pathway demonstrates heterogeneity, linked to the tumor development stage, pathway status, and specific cell types. We propose that within the TME, the innate immune pathway exhibits multidimensional diversity. This diversity is fundamentally rooted in cellular heterogeneity and is manifested as a variety of signaling networks. The pro-tumor effect of innate immune pathway activation essentially reflects the suppression of classical pathways and the activation of potential pro-tumor alternative pathways. Refining our understanding of the tumor's innate immune pathway network and employing appropriate targeting strategies can enhance our ability to harness the anti-tumor potential of the innate immune pathway and ultimately bridge the gap from preclinical to clinical application.

Fatty acid oxidation fuels natural killer cell responses against infection and cancer

Natural killer (NK) cells are a vital part of the innate immune system capable of rapidly clearing mutated or infected cells from the body and promoting an immune response. Here, we find that NK cells activated by viral infection or tumor challenge increase uptake of fatty acids and their expression of carnitine palmitoyltransferase I (CPT1A), a critical enzyme for long-chain fatty acid oxidation. Using a mouse model with an NK cell-specific deletion of CPT1A, combined with stable 13C isotope tracing, we observe reduced mitochondrial function and fatty acid-derived aspartate production in CPT1A-deficient NK cells. Furthermore, CPT1A-deficient NK cells show reduced proliferation after viral infection and diminished protection against cancer due to impaired actin cytoskeleton rearrangement. Together, our findings highlight that fatty acid oxidation promotes NK cell metabolic resilience, processes that can be optimized in NK cell-based immunotherapies.

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.

Restriction of Glycolysis Increases Serial Killing Capacity of Natural Killer Cells

Tumor cells rely heavily on glycolysis to meet their high metabolic demands. While this results in nutrient deprivation within the tumor microenvironment and has negative effects on infiltrating immune cells such as natural killer (NK) cells, it also creates a potential target for cancer therapies. Here we use Glupin, an inhibitor of glucose transporters, to study the effect of limited glucose uptake on NK cells and their anti-tumor functions. Glupin treatment effectively inhibited glucose uptake and restricted glycolysis in NK cells. However, acute treatment had no negative effect on NK cell cytotoxicity or cytokine production. Long-term restriction of glucose uptake via Glupin treatment only delayed NK cell proliferation, as they could switch to glutaminolysis as an alternative energy source. While IFN-γ production was partially impaired, long-term Glupin treatment had no negative effect on degranulation. Interestingly, the serial killing activity of NK cells was even slightly enhanced, possibly due to changes in NAD metabolism. This demonstrates that NK cell cytotoxicity is remarkably robust and insensitive to metabolic disturbances, which makes cellular metabolism an attractive target for immune-mediated tumor therapies.

NK cell-activating receptor NKp46 does not participate in the development of obesity-induced inflammation and insulin resistance

Recent evidence establishes a pivotal role for obesity-induced inflammation in precipitating insulin resistance and type-2 diabetes. Central to this process is the proinflammatory M1 adipose-tissue macrophages (ATMs) in epididymal white adipose tissue (eWAT). Notably, natural killer (NK) cells are a crucial regulator of ATMs since their cytokines induce ATM recruitment and M1 polarization. The importance of NK cells is shown by the strong increase in NK-cell numbers in eWAT, and by studies showing that removing and expanding NK cells respectively improve and worsen obesity-induced insulin resistance. It has been suggested that NK cells are activated by unknown ligands on obesity-stressed adipocytes that bind to NKp46 (encoded by Ncr1), which is an activating NK-cell receptor. This was supported by a study showing that NKp46-knockout mice have improved obesity-induced inflammation/insulin resistance. We therefore planned to use the NKp46-knockout mice to further elucidate the molecular mechanism by which NKp46 mediates eWAT NK-cell activation in obesity. We confirmed that obesity increased eWAT NKp46+ NK-cell numbers and NKp46 expression in wild-type mice and that NKp46-knockout ablated these responses. Unexpectedly, however, NKp46-knockout mice demonstrated insulin resistance similar to wild-type mice, as shown by fasting blood glucose/insulin levels and glucose/insulin tolerance tests. Obesity-induced increases in eWAT ATM numbers and proinflammatory gene expression were also similar. Thus, contrary to previously published results, NKp46 does not regulate obesity-induced insulin resistance. It is therefore unclear whether NKp46 participates in the development of obesity-induced inflammation and insulin resistance. This should be considered when elucidating the obesity-mediated molecular mechanisms that activate NK cells.

Lipid Metabolism-Related Gene Signature Predicts Prognosis and Indicates Immune Microenvironment Infiltration in Advanced Gastric Cancer

Objective

Abnormal lipid metabolism is known to influence the malignant behavior of gastric cancer. However, the underlying mechanism remains elusive. In this study, we comprehensively analyzed the biological significance of genes involved in lipid metabolism in advanced gastric cancer (AGC).

Methods

We obtained gene expression profiles from The Cancer Genome Atlas (TCGA) database for early and advanced gastric cancer samples and performed differential expression analysis to identify specific lipid metabolism-related genes in AGC. We then used consensus cluster analysis to classify AGC patients into molecular subtypes based on lipid metabolism and constructed a diagnostic model using least absolute shrinkage and selection operator- (LASSO-) Cox regression analysis and Gene Set Enrichment Analysis (GSEA). We evaluated the discriminative ability and clinical significance of the model using the Kaplan-Meier (KM) curve, ROC curve, DCA curve, and nomogram. We also estimated immune levels based on immune microenvironment expression, immune checkpoints, and immune cell infiltration and obtained hub genes by weighted gene co-expression network analysis (WGCNA) of differential genes from the two molecular subtypes.

Results

We identified 6 lipid metabolism genes that were associated with the prognosis of AGC and used consistent clustering to classify AGC patients into two subgroups with significantly different overall survival and immune microenvironment. Our risk model successfully classified patients in the training and validation sets into high-risk and low-risk groups. The high-risk score predicted poor prognosis and indicated low degree of immune infiltration. Subgroup analysis showed that the risk model was an independent predictor of prognosis in AGC. Furthermore, our results indicated that most chemotherapeutic agents are more effective for AGC patients in the low-risk group than in the high-risk group, and risk scores for AGC are strongly correlated with drug sensitivity. Finally, we performed qRT-PCR experiments to verify the relevant results.

Conclusion

Our findings suggest that lipid metabolism-related genes play an important role in predicting the prognosis of AGC and regulating immune invasion. These results have important implications for the development of targeted therapies for AGC patients.

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.

Real-time ex vivo monitoring of NK cell migration toward obesity-associated oesophageal adenocarcinoma following modulation of CX3CR1

Oesophagogastric adenocarcinomas (OAC) are poor prognosis, obesity-associated cancers which may benefit from natural killer (NK) cell-based immunotherapies. Cellular immunotherapies encounter two key challenges to their success in OAC, namely recruitment to extratumoural tissues such as the omentum at the expense of the tumour and an immunosuppressive tumour microenvironment (TME) which can hamper NK cell function. Herein, we examined approaches to overcome the detrimental impact of obesity on NK cells and NK cell-based immunotherapies. We have demonstrated that NK cells migrate preferentially to the chemotactic signals of OAC patient-derived omentum over tumour in an ex vivo model of immune cell migration. We have identified CX3CR1 modulation and/or tumour chemokine profile remodelling as approaches to skew NK cell migration towards tumour. We also report targetable immunosuppressive facets of the obese OAC TME which dampen NK cell function, in particular cytotoxic capabilities. These data provide insights into approaches to therapeutically overcome key challenges presented by obesity and will inform superior design of NK cell-based immunotherapies for OAC.

Immunometabolic features of natural killer cells are associated with infection outcomes in critical illness

Immunosuppression increases the risk of nosocomial infection in patients with chronic critical illness. This exploratory study aimed to determine the immunometabolic signature associated with nosocomial infection during chronic critical illness. We prospectively recruited patients who were admitted to the respiratory care center and who had received mechanical ventilator support for more than 10 days in the intensive care unit. The study subjects were followed for the occurrence of nosocomial infection until 6 weeks after admission, hospital discharge, or death. The cytokine levels in the plasma samples were measured. Single-cell immunometabolic regulome profiling by mass cytometry, which analyzed 16 metabolic regulators in 21 immune subsets, was performed to identify immunometabolic features associated with the risk of nosocomial infection. During the study period, 37 patients were enrolled, and 16 patients (43.2%) developed nosocomial infection. Unsupervised immunologic clustering using multidimensional scaling and logistic regression analyses revealed that expression of nuclear respiratory factor 1 (NRF1) and carnitine palmitoyltransferase 1a (CPT1a), key regulators of mitochondrial biogenesis and fatty acid transport, respectively, in natural killer (NK) cells was significantly associated with nosocomial infection. Downregulated NRF1 and upregulated CPT1a were found in all subsets of NK cells from patients who developed a nosocomial infection. The risk of nosocomial infection is significantly correlated with the predictive score developed by selecting NK cell-specific features using an elastic net algorithm. Findings were further examined in an independent cohort of COVID-19-infected patients, and the results confirm that COVID-19-related mortality is significantly associated with mitochondria biogenesis and fatty acid oxidation pathways in NK cells. In conclusion, this study uncovers that NK cell-specific immunometabolic features are significantly associated with the occurrence and fatal outcomes of infection in critically ill population, and provides mechanistic insights into NK cell-specific immunity against microbial invasion in critical illness.

Molecular mechanisms in MASLD/MASH-related HCC

Liver cancer is the third leading cause of cancer-related deaths and ranks as the sixth most prevalent cancer type globally. NAFLD or metabolic dysfunction-associated steatotic liver disease, and its more severe manifestation, NASH or metabolic dysfunction-associated steatohepatitis (MASH), pose a significant global health concern, affecting approximately 20%-25% of the population. The increased prevalence of metabolic dysfunction-associated steatotic liver disease and MASH is parallel to the increasing rates of obesity-associated metabolic diseases, including type 2 diabetes, insulin resistance, and fatty liver diseases. MASH can progress to MASH-related HCC (MASH-HCC) in about 2% of cases each year, influenced by various factors such as genetic mutations, carcinogen exposure, immune microenvironment, and microbiome. MASH-HCC exhibits distinct molecular and immune characteristics compared to other causes of HCC and affects both men and women equally. The management of early to intermediate-stage MASH-HCC typically involves surgery and locoregional therapies, while advanced HCC is treated with systemic therapies, including anti-angiogenic therapies and immune checkpoint inhibitors. In this comprehensive review, we consolidate previous research findings while also providing the most current insights into the intricate molecular processes underlying MASH-HCC development. We delve into MASH-HCC-associated genetic variations and somatic mutations, disease progression and research models, multiomics analysis, immunological and microenvironmental impacts, and discuss targeted/combined therapies to overcome immune evasion and the biomarkers to recognize treatment responders. By furthering our comprehension of the molecular mechanisms underlying MASH-HCC, our goal is to catalyze the advancement of more potent treatment strategies, ultimately leading to enhanced patient outcomes.

Roles of PPAR activation in cancer therapeutic resistance: Implications for combination therapy and drug development

Therapeutic resistance is a major obstacle to successful treatment or effective containment of cancer. Peroxisome proliferator-activated receptors (PPARs) play an essential role in regulating energy homeostasis and determining cell fate. Despite of the pleiotropic roles of PPARs in cancer, numerous studies have suggested their intricate relationship with therapeutic resistance in cancer. In this review, we provided an overview of the roles of excessively activated PPARs in promoting resistance to modern anti-cancer treatments, including chemotherapy, radiotherapy, targeted therapy, and immunotherapy. The mechanisms through which activated PPARs contribute to therapeutic resistance in most cases include metabolic reprogramming, anti-oxidant defense, anti-apoptosis signaling, proliferation-promoting pathways, and induction of an immunosuppressive tumor microenvironment. In addition, we discussed the mechanisms through which activated PPARs lead to multidrug resistance in cancer, including drug efflux, epithelial-to-mesenchymal transition, and acquisition and maintenance of the cancer stem cell phenotype. Preliminary studies investigating the effect of combination therapies with PPAR antagonists have suggested the potential of these antagonists in reversing resistance and facilitating sustained cancer management. These findings will provide a valuable reference for further research on and clinical translation of PPAR-targeting treatment strategies.

Single-cell transcriptome analysis reveals immunosuppressive landscape in overweight and obese colorectal cancer

BACKGROUND

Overweight and obesity are established risk factors for various types of cancers including colorectal cancer (CRC). However the underlying molecular mechanisms remain unclear. An in-depth understanding of the oncologic characteristics of overweight and obese CRC at the single-cell level can provide valuable insights for the development of more effective treatment strategies for CRC.

METHODS

We conducted single-cell RNA sequencing (scRNA-seq) analysis on tumor and adjacent normal colorectal samples from 15 overweight/obese and 15 normal-weight CRC patients. Immunological and metabolic differences between overweight/obese CRC and non-obese CRC were characterized.

RESULTS

We obtained single-cell transcriptomics data from a total of 192,785 cells across all samples. By evaluating marker gene expression patterns, we annotated nine main cell types in the CRC ecosystem. Specifically, we found that the cytotoxic function of effector T cells and NK cells was impaired in overweight/obese CRC compared with non-obese CRC, relating to its metabolic dysregulation. CD4+T cells in overweight/obese CRC exhibited higher expression of immune checkpoint molecules. The antigen-presenting ability of DCs and B cells is down-regulated in overweight/obese CRC, which may further aggravate the immunosuppression of overweight/obese CRC. Additionally, dysfunctional stromal cells were identified, potentially promoting invasion and metastasis in overweight/obese CRC. Furthermore, we discovered the up-regulated metabolism of glycolysis and lipids of tumor cells in overweight/obese CRC, which may impact the metabolism and function of immune cells. We also identified inhibitory interactions between tumor cells and T cells in overweight/obese CRC.

CONCLUSIONS

The study demonstrated that overweight/obese CRC has a more immunosuppressive microenvironment and distinct metabolic reprogramming characterized by increased of glycolysis and lipid metabolism. These findings may have implications for the development of novel therapeutic strategies for overweight/obese CRC patients.

Peroxisome proliferator-activated receptors: A key link between lipid metabolism and cancer progression

Lipids represent the essential components of membranes, serve as fuels for high-energy processes, and play crucial roles in signaling and cellular function. One of the key hallmarks of cancer is the reprogramming of metabolic pathways, especially abnormal lipid metabolism. Alterations in lipid uptake, lipid desaturation, de novo lipogenesis, lipid droplets, and fatty acid oxidation in cancer cells all contribute to cell survival in a changing microenvironment by regulating feedforward oncogenic signals, key oncogenic functions, oxidative and other stresses, immune responses, or intercellular communication. Peroxisome proliferator-activated receptors (PPARs) are transcription factors activated by fatty acids and act as core lipid sensors involved in the regulation of lipid homeostasis and cell fate. In addition to regulating whole-body energy homeostasis in physiological states, PPARs play a key role in lipid metabolism in cancer, which is receiving increasing research attention, especially the fundamental molecular mechanisms and cancer therapies targeting PPARs. In this review, we discuss how cancer cells alter metabolic patterns and regulate lipid metabolism to promote their own survival and progression through PPARs. Finally, we discuss potential therapeutic strategies for targeting PPARs in cancer based on recent studies from the last five years.

The fatty acid-related gene signature stratifies poor prognosis patients and characterizes TIME in cutaneous melanoma

BACKGROUND

The aim of this study is to build a prognostic model for cutaneous melanoma (CM) using fatty acid-related genes and evaluate its capacity for predicting prognosis, identifying the tumor immune microenvironment (TIME) composition, and assessing drug sensitivity.

METHODS

Through the analysis of transcriptional data from TCGA-SKCM and GTEx datasets, we screened for differentially expressed fatty acids-related genes (DEFAGs). Additionally, we employed clinical data from TCGA-SKCM and GSE65904 to identify genes associated with prognosis. Subsequently, utilizing all the identified prognosis-related fatty acid genes, we performed unsupervised clustering analysis using the ConsensusClusterPlus R package. We further validated the significant differences between subtypes through survival analysis and pathway analysis. To predict prognosis, we developed a LASSO-Cox prognostic signature. This signature's predictive ability was rigorously examined through multivariant Cox regression, survival analysis, and ROC curve analysis. Following this, we constructed a nomogram based on the aforementioned signature and evaluated its accuracy and clinical utility using calibration curves, cumulative hazard rates, and decision curve analysis. Using this signature, we stratified all cases into high- and low-risk groups and compared the differences in immune characteristics and drug treatment responsiveness between these two subgroups. Additionally, in this study, we provided preliminary confirmation of the pivotal role of CD1D in the TIME of CM. We analyzed its expression across various immune cell types and its correlation with intercellular communication using single-cell data from the GSE139249 dataset.

RESULTS

In this study, a total of 84 DEFAGs were identified, among which 18 were associated with prognosis. Utilizing these 18 prognosis-related genes, all cases were categorized into three subtypes. Significant differences were observed between subtypes in terms of survival outcomes, the expression of the 18 DEFAGs, immune cell proportions, and enriched pathways. A LASSO-Cox regression analysis was performed on these 18 genes, leading to the development of a signature comprising 6 DEFAGs. Risk scores were calculated for all cases, dividing them into high-risk and low-risk groups. High-risk patients exhibited significantly poorer prognosis than low-risk patients, both in the training group (p < 0.001) and the test group (p = 0.002). Multivariate Cox regression analysis indicated that this signature could independently predict outcomes [HR = 2.03 (1.69-2.45), p < 0.001]. The area under the ROC curve for the training and test groups was 0.715 and 0.661, respectively. Combining risk scores with clinical factors including metastatic status and patient age, a nomogram was constructed, which demonstrated significant predictive power for 3  and 5 years patient outcomes. Furthermore, the high and low-risk subgroups displayed differences in the composition of various immune cells, including M1 macrophages, M0 macrophages, and CD8+ T cells. The low-risk subgroup exhibited higher StromalScore, ImmuneScore, and ESTIMATEScore (p < 0.001) and demonstrated better responsiveness to immune therapy for patients with PD1-positive and CTLA4-negative or positive expressions (p < 0.001). The signature gene CD1D was found to be mainly expressed in monocytes/macrophages and dendritic cells within the TIME. Through intercellular communication analysis, it was observed that cases with high CD1D expression exhibited significantly enhanced signal transductions from other immune cells to monocytes/macrophages, particularly the (HLA-A/B/C/E/F)-CD8A signaling from natural killer (NK) cells to monocytes/macrophages (p < 0.01).

CONCLUSIONS

The prognostic signature constructed in this study, based on six fatty acid-related genes, exhibits strong capabilities in predicting patient outcomes, identifying the TIME, and assessing drug sensitivity. This signature can aid in patient risk stratification and provide guidance for clinical treatment strategies. Additionally, our research highlights the crucial role of CD1D in the CM's TIME, laying a theoretical foundation for future related studies.

CD36: The Bridge between Lipids and Tumors

It has been found that the development of some cancers can be attributed to obesity, which is associated with the excessive intake of lipids. Cancer cells undergo metabolic reprogramming, shifting from utilizing glucose to fatty acids (FAs) for energy. CD36, a lipid transporter, is highly expressed in certain kinds of cancer cells. High expressions of CD36 in tumor cells triggers FA uptake and lipid accumulation, promoting rapid tumor growth and initiating metastasis. Meanwhile, immune cells in the tumor microenvironment overexpress CD36 and undergo metabolic reprogramming. CD36-mediated FA uptake leads to lipid accumulation and has immunosuppressive effects. This paper reviews the types of FAs associated with cancer, high expressions of CD36 that promote cancer development and progression, effects of CD36 on different immune cells in the tumor microenvironment, and the current status of CD36 as a therapeutic target for the treatment of tumors with high CD36 expression.

Breakthrough of solid tumor treatment: CAR-NK immunotherapy

As the latest and most anticipated method of tumor immunotherapy, CAR-NK therapy has received increasing attention in recent years, and its safety and high efficiency have irreplaceable advantages over CAR-T. Current research focuses on the application of CAR-NK in hematological tumors, while there are fewer studies on solid tumor. This article reviews the process of constructing CAR-NK, the effects of hypoxia and metabolic factors, NK cell surface receptors, cytokines, and exosomes on the efficacy of CAR-NK in solid tumor, and the role of CAR-NK in various solid tumor. The mechanism of action and the research status of the potential of CAR-NK in the treatment of solid tumor in clinical practice, and put forward the advantages, limitations and future problems of CAR-NK in the treatment of solid tumor.

IL-15 reprogramming compensates for NK cell mitochondrial dysfunction in HIV-1 infection

Dynamic regulation of cellular metabolism is important for maintaining homeostasis and can directly influence immune cell function and differentiation, including NK cell responses. Persistent HIV-1 infection leads to a state of chronic immune activation, NK cell subset redistribution, and progressive NK cell dysregulation. In this study, we examined the metabolic processes that characterize NK cell subsets in HIV-1 infection, including adaptive NK cell subpopulations expressing the activating receptor NKG2C, which expand during chronic infection. These adaptive NK cells exhibit an enhanced metabolic profile in HIV-1- individuals infected with human cytomegalovirus (HCMV). However, the bioenergetic advantage of adaptive CD57+NKG2C+ NK cells is diminished during chronic HIV-1 infection, where NK cells uniformly display reduced oxidative phosphorylation (OXPHOS). Defective OXPHOS was accompanied by increased mitochondrial depolarization, structural alterations, and increased DRP-1 levels promoting fission, suggesting that mitochondrial defects are restricting the metabolic plasticity of NK cell subsets in HIV-1 infection. The metabolic requirement for the NK cell response to receptor stimulation was alleviated upon IL-15 pretreatment, which enhanced mammalian target of rapamycin complex 1 (mTORC1) activity. IL-15 priming enhanced NK cell functionality to anti-CD16 stimulation in HIV-1 infection, representing an effective strategy for pharmacologically boosting NK cell responses.

IL-10-expressing CAR T cells resist dysfunction and mediate durable clearance of solid tumors and metastases

The success of chimeric antigen receptor (CAR) T cell therapy in treating several hematopoietic malignancies has been difficult to replicate in solid tumors, in part because of T cell exhaustion and eventually dysfunction. To counter T cell dysfunction in the tumor microenvironment, we metabolically armored CAR T cells by engineering them to secrete interleukin-10 (IL-10). We show that IL-10 CAR T cells preserve intact mitochondrial structure and function in the tumor microenvironment and increase oxidative phosphorylation in a mitochondrial pyruvate carrier-dependent manner. IL-10 secretion promoted proliferation and effector function of CAR T cells, leading to complete regression of established solid tumors and metastatic cancers across several cancer types in syngeneic and xenograft mouse models, including colon cancer, breast cancer, melanoma and pancreatic cancer. IL-10 CAR T cells also induced stem cell-like memory responses in lymphoid organs that imparted durable protection against tumor rechallenge. Our results establish a generalizable approach to counter CAR T cell dysfunction through metabolic armoring, leading to solid tumor eradication and long-lasting immune protection.

Prophylactic treatment with Bacteroides uniformis and Bifidobacterium bifidum counteracts hepatic NK cell immune tolerance in nonalcoholic steatohepatitis induced by high fat diet

Hepatic immunity is one of the driving forces for the development of nonalcoholic steatohepatitis (NASH), and targeting gut microbiota is believed to affect the hepatic immune constitution. Here, we aimed to investigate the hepatic immunological state in NASH, with a specific emphasis on natural killer (NK) cells. In addition, we aimed to identify the contributing species that target hepatic immunity to provide new directions and support the feasibility of immunotherapy for NASH. A possible NASH population was determined by combination of long-term severe fatty liver, metabolic disorders and increased serum CK18 to detect serum immune factors and gut microbiota. NASH was induced in mice fed a high-fat diet to verify the prophylactic effect of the functional species on the immunopathology and development of NASH. Hepatic immunologic state was examined, and the effector functions of NK cells were detected. Hepatic transcriptome, proteomic, and fecal metagenome were performed. We observed a statistical increase in serum IL-10 (p < 0.001) and non-statistical decrease in interferon-γ and IL-6 in NASH population, hinting at the possibility of immune tolerance. Fecal Bacteroides uniformis and Bifidobacterium bifidum were abundant in healthy population but depleted in NASH patients. In NASH mice, hepatic CD8+T cells, macrophages, and dendritic cells were increased (p < 0.01), and NK cells were inhibited, which were identified with decreased granzyme B (p < 0.05). Bacteroides uniformis and Bifidobacterium bifidum improved hepatic pathological and metabolic cues, increased hepatic NK cells and reduced macrophages (p < 0.05). Bacteroides uniformis also restored hepatic NK cell function, which was identified as increased CD107a (p < 0.05). Transcriptional and translational profiling revealed that the functional species might restore the function of hepatic NK cells through multiple pathways, such as reduction of inhibitory molecules in NK cells. Bacteroides uniformis and Bifidobacterium bifidum are novel prophylactics for NASH that restore the impaired function of hepatic NK cells.

Harnessing the innate immune system by revolutionizing macrophage-mediated cancer immunotherapy

Immunotherapy is a promising and safer alternative to conventional cancer therapies. It involves adaptive T-cell therapy, cancer vaccines, monoclonal antibodies, immune checkpoint blockade (ICB), and chimeric antigen receptor (CAR) based therapies. However, most of these modalities encounter restrictions in solid tumours owing to a dense, highly hypoxic and immune-suppressive microenvironment as well as the heterogeneity of tumour antigens. The elevated intra-tumoural pressure and mutational rates within fastgrowing solid tumours present challenges in efficient drug targeting and delivery. The tumour microenvironment is a dynamic niche infiltrated by a variety of immune cells, most of which are macrophages. Since they form a part of the innate immune system, targeting macrophages has become a plausible immunotherapeutic approach. In this review, we discuss several versatile approaches (both at pre-clinical and clinical stages) such as the direct killing of tumour-associated macrophages, reprogramming pro-tumour macrophages to anti-tumour phenotypes, inhibition of macrophage recruitment into the tumour microenvironment, novel CAR macrophages, and genetically engineered macrophages that have been devised thus far. These strategies comprise a strong and adaptable macrophage-toolkit in the ongoing fight against cancer and by understanding their significance, we may unlock the full potential of these immune cells in cancer therapy.

Fat Biology in Triple-Negative Breast Cancer: Immune Regulation, Fibrosis, and Senescence

Obesity, now officially recognized as a disease requiring intervention, has emerged as a significant health concern due to its strong association with elevated susceptibility to diverse diseases and various types of cancer, including breast cancer. The link between obesity and cancer is intricate, with obesity exerting a significant impact on cancer recurrence and elevated mortality rates. Among the various subtypes of breast cancer, triple-negative breast cancer (TNBC) is the most aggressive, accounting for 15% to 20% of all cases. TNBC is characterized by low expression of estrogen receptors and progesterone receptors as well as the human epidermal growth factor 2 receptor protein. This subtype poses distinct challenges in terms of treatment response and exhibits strong invasiveness. Furthermore, TNBC has garnered attention because of its association with obesity, in which excess body fat and reduced physical activity have been identified as contributing factors to the increased incidence of this aggressive form of breast cancer. In this comprehensive review, the impact of obesity on TNBC was explored. Specifically, we focused on the three key mechanisms by which obesity affects TNBC development and progression: modification of the immune profile, facilitation of fibrosis, and initiation of senescence. By comprehensively examining these mechanisms, we illuminated the complex interplay between TNBC and obesity, facilitating the development of novel approaches for prevention, early detection, and effective management of this challenging disease.

The effect of diet and nutrition on T cell function in cancer

Cancer can be considered one of the most threatening diseases to human health, and immunotherapy, especially T-cell immunotherapy, is the most promising treatment for cancers. Diet therapy is widely concerned in cancer because of its safety and fewer side effects. Many studies have shown that both the function of T cells and the progression of cancer can be affected by nutrients in the diet. In fact, it is challenging for T cells to infiltrate and eliminate cancer cells in tumor microenvironment, because of the harsh metabolic condition. The intake of different nutrients has a great influence on the proliferation, activation, differentiation and exhaustion of T cells. In this review, we summarize the effects of typical amino acids, lipids, carbohydrates and other nutritional factors on T cell functions and provide future perspectives for dietary treatment of cancer based on modifications of T cell functions.

Lifestyle and host determinants of antitumor immunity and cancer health disparities

Lifestyle factors exert profound effects on host physiology and immunology. Disparities in cancer outcomes persist as a complex and multifaceted challenge, necessitating a comprehensive understanding of the interplay between host environment and antitumor immune responses. Determinants of health - such as obesity, diet, exercise, stress, or sleep disruption - have the potential for modification, yet some exert long-lasting effects and may challenge the notion of complete reversibility. Herein we review intersectional considerations of lifestyle immunity and the impact on tumor immunology and disparities in cancer outcomes, with a focus on obesity.

Fatty acids are crucial to fuel NK cells upon acute retrovirus infection

Natural killer (NK) cells are cytotoxic innate immune cells, able to recognize and eliminate virus-infected as well as cancer cells. Metabolic reprogramming is crucial for their activity as they have enhanced energy and nutritional demands for their functions during an infection. Fatty acids (FAs) represent an important source of cellular energy and are essential for proliferation of immune cells. However, the precise role of FAs for NK cells activity in retrovirus infection was unknown. Here we show that activated NK cells increase the expression of the FA uptake receptor CD36 and subsequently the uptake of FAs upon acute virus infection. We found an enhanced flexibility of NK cells to utilize FAs as source of energy compare to naïve NK cells. NK cells that were able to generate energy from FAs showed an augmented target cell killing and increased expression of cytotoxic parameters. However, NK cells that were unable to generate energy from FAs exhibited a severely decreased migratory capacity. Our results demonstrate that NK cells require FAs in order to fight acute virus infection. Susceptibility to severe virus infections as it is shown for people with malnutrition may be augmented by defects in the FA processing machinery, which might be a target to therapeutically boost NK cell functions in the future.

The placental vasculature is affected by changes in gene expression and glycogen-rich cells in a diet-induced obesity mouse model

Maternal obesity is a risk factor for pregnancy complications. Obesity caused by a high-fat diet (HFD) may alter maternal glucose/glycogen metabolism. Here, our objective was to investigate whether the placental vasculature is altered via changes in gene expression and glycogen-rich cells using a preclinical mouse model of diet-induced obesity. We subjected female FVB/N mice to one of three feeding regimens: regular chow (RC) given at preconception and during pregnancy (Control); RC given at preconception and then a HFD during pregnancy (HFD-P); or HFD initiated 4 weeks preconception and during pregnancy (HFD-PreCP). Daily food consumption and weekly maternal weights were recorded. Maternal blood glucose levels were measured at preconception and 4 gestational epochs (E6.5-E9.5, E10.5-E12.5, E13.5-E15.5, E16.5-E19.5). At E8.5-E16.5, total RNA in placentas were isolated for gene expression analyses. Placentas were also collected for HE and periodic acid Schiff's (PAS) staining and glycogen content assays. Dams in the HFD-P and HFD-PreCP groups gained significantly more weight than controls. Pre- and antenatal glucose levels were also significantly higher (15%-30%) in HFD-PreCP dams. Expression of several placental genes were also altered in HFD dams compared with controls. Consumption of the HFD also led to phenotypic and morphologic changes in glycogen trophoblasts (GlyTs) and uterine natural killer (uNK) cells. Alterations in vascularity were also observed in the labyrinth of HFD-PreCP placentas, which correlated with decreased placental efficiency. Overall, we observed that a HFD induces gestational obesity in mice, alters expression of placental genes, affects glucose homeostasis, and alters glycogen-positive GlyTs and uNK cells. All these changes may lead to impaired placental vascular development, and thus heighten the risk for pregnancy complications.

NK cell exhaustion in the tumor microenvironment

Natural killer (NK) cells kill mutant cells through death receptors and cytotoxic granules, playing an essential role in controlling cancer progression. However, in the tumor microenvironment (TME), NK cells frequently exhibit an exhausted status, which impairs their immunosurveillance function and contributes to tumor immune evasion. Emerging studies are ongoing to reveal the properties and mechanisms of NK cell exhaustion in the TME. In this review, we will briefly introduce the maturation, localization, homeostasis, and cytotoxicity of NK cells. We will then summarize the current understanding of the main mechanisms underlying NK cell exhaustion in the TME in four aspects: dysregulation of inhibitory and activating signaling, tumor cell-derived factors, immunosuppressive cells, and metabolism and exhaustion. We will also discuss the therapeutic approaches currently being developed to reverse NK cell exhaustion and enhance NK cell cytotoxicity in the TME.

Dietary fat and lipid metabolism in the tumor microenvironment

Metabolic reprogramming has been considered a core hallmark of cancer, in which excessive accumulation of lipids promote cancer initiation, progression and metastasis. Lipid metabolism often includes the digestion and absorption of dietary fat, and the ways in which cancer cells utilize lipids are often influenced by the complex interactions within the tumor microenvironment. Among multiple cancer risk factors, obesity has a positive association with multiple cancer types, while diets like calorie restriction and fasting improve health and delay cancer. Impact of these diets on tumorigenesis or cancer prevention are generally studied on cancer cells, despite heterogeneity of the tumor microenvironment. Cancer cells regularly interact with these heterogeneous microenvironmental components, including immune and stromal cells, to promote cancer progression and metastasis, and there is an intricate metabolic crosstalk between these compartments. Here, we focus on discussing fat metabolism and response to dietary fat in the tumor microenvironment, focusing on both immune and stromal components and shedding light on therapeutic strategies surrounding lipid metabolic and signaling pathways.

The Lysosomal Calcium Channel TRPML1 Maintains Mitochondrial Fitness in NK Cells through Interorganelle Cross-Talk

Cytotoxic lymphocytes eliminate cancer cells through the release of lytic granules, a specialized form of secretory lysosomes. This compartment is part of the pleomorphic endolysosomal system and is distinguished by its highly dynamic Ca2+ signaling machinery. Several transient receptor potential (TRP) calcium channels play essential roles in endolysosomal Ca2+ signaling and ensure the proper function of these organelles. In this study, we examined the role of TRPML1 (TRP cation channel, mucolipin subfamily, member 1) in regulating the homeostasis of secretory lysosomes and their cross-talk with mitochondria in human NK cells. We found that genetic deletion of TRPML1, which localizes to lysosomes in NK cells, led to mitochondrial fragmentation with evidence of collapsed mitochondrial cristae. Consequently, TRPML1-/- NK92 (NK92ML1-/-) displayed loss of mitochondrial membrane potential, increased reactive oxygen species stress, reduced ATP production, and compromised respiratory capacity. Using sensitive organelle-specific probes, we observed that mitochondria in NK92ML1-/- cells exhibited evidence of Ca2+ overload. Moreover, pharmacological activation of the TRPML1 channel in primary NK cells resulted in upregulation of LC3-II, whereas genetic deletion impeded autophagic flux and increased accumulation of dysfunctional mitochondria. Thus, TRPML1 impacts autophagy and clearance of damaged mitochondria. Taken together, these results suggest that an intimate interorganelle communication in NK cells is orchestrated by the lysosomal Ca2+ channel TRPML1.

Lipid accumulation-mediated histone hypoacetylation drives persistent NK cell dysfunction in anti-tumor immunity

Hyperlipidemia impairs anti-tumor immune responses and is closely associated with increased human cancer incidence and mortality. However, the underlying mechanisms are not well understood. In the present study, we show that natural killer (NK) cells isolated from high-fat-diet mice or treated with oleic acid (OA) in vitro exhibit sustainable functional defects even after removal from hyperlipidemic milieu. This is accompanied by reduced chromatin accessibility in the promoter region of NK cell effector molecules. Mechanistically, OA exposure blunts P300-mediated c-Myc acetylation and shortens its protein half-life in NK cells, which in turn reduces P300 accumulation and H3K27 acetylation and leads to persistent NK cell dysfunction. NK cells engineered with hyperacetylated c-Myc mutants surmount the suppressive effect of hyperlipidemia and display superior anti-tumor activity. Our findings reveal the persistent dysfunction of NK cells in dyslipidemia milieu and extend engineered NK cells as a promising strategy for tumor immunotherapy.

Uptake of long-chain fatty acids from the bone marrow suppresses CD8+ T-cell metabolism and function in multiple myeloma

T cells demonstrate impaired function in multiple myeloma (MM) but suppressive mechanisms in the bone marrow microenvironment remain poorly defined. We observe that bone marrow CD8+ T-cell function is decreased in MM compared with controls, and is also consistently lower within bone marrow samples than in matched peripheral blood samples. These changes are accompanied by decreased mitochondrial mass and markedly elevated long-chain fatty acid uptake. In vitro modeling confirmed that uptake of bone marrow lipids suppresses CD8+ T function, which is impaired in autologous bone marrow plasma but rescued by lipid removal. Analysis of single-cell RNA-sequencing data identified expression of fatty acid transport protein 1 (FATP1) in bone marrow CD8+ T cells in MM, and FATP1 blockade also rescued CD8+ T-cell function, thereby identifying this as a novel target to augment T-cell activity in MM. Finally, analysis of samples from cohorts of patients who had received treatment identified that CD8+ T-cell metabolic dysfunction resolves in patients with MM who are responsive to treatment but not in patients with relapsed MM, and is associated with substantial T-cell functional restoration.

Depletion of Gr1+ myeloid cells attenuates high-fat-diet-aggravated esophageal squamous cell carcinoma in mice

Obesity is a leading cause of multiple cancers, but whether it promotes esophageal squamous cell carcinoma (ESCC) and its underlying cancer-promoting mechanism remains unclear. To evaluate the effect of a high-fat diet (HFD) on ESCC and explore the role and mechanism of myeloid-derived suppressor cells (MDSCs) in HFD-induced ESCC, C57BL/6J mice were treated with 4-nitroquinoline 1-oxide (4NQO) to induce ESCC and randomly assigned to an HFD or a normal-fat diet. An anti-Gr1 monoclonal antibody was used to deplete MDSCs in the context of experimental diets and ESCC induction. The expression of MDSC markers CD11b and Gr1 and immune checkpoints (ICs) PD1, TIM3, and VISTA in lesions were detected by immunohistochemistry. The correlation between myeloid cell markers (CD11b and CD33) and ICs and their relationship with ESCC patient prognosis were further analyzed using the The Cancer Genome Atlas dataset. The results showed that HFD accelerated esophageal carcinogenesis, induced MDSC expansion, and upregulated IC expression, whereas depletion of Gr1+ myeloid cells significantly suppressed tumor growth, decreased the number of MDSCs, and downregulated IC expression in HFD mice. PD1, TIM3, and VISTA expressions were positively correlated with myeloid cell marker expression in human ESCC. Moreover, the high expression of IC molecules was associated with poor survival in patients with ESCC. These data indicate that HFD promotes the initiation and development of ESCC. Gr1+ myeloid cell targeting significantly inhibited ESCC formation in HFD mice, which may be associated with IC downregulation.

The involvement of circulating CD69+ CD56bright natural killer cells in weight loss before bariatric surgery: A retrospective cohort study

As the impact of the immune system on weight loss prior to bariatric surgery has never been proven, we elucidated the clinical utility of the immune system as an indicator of preoperative weight loss before bariatric surgery. We examined the relationships between preoperative weight loss and biochemical and clinical data at the initial visit in 34 obese patients. Patients were divided according to preoperative weight loss, and peripheral blood mononuclear cells were compared using flowcytometry. The Δpreoperative excess weight loss [Δpre-EWL: pre-EWL (%)/period of preoperative weight loss (days)] showed negative correlations with total and subcutaneous fat area (P = .02, r = -0.41, P = .02, r = -0.42 respectively). The Δpre-EWL and Δpreoperative total weight loss (Δpre-TWL) were negatively correlated with white blood cell count, lymphocyte count, and C-reactive protein (CRP) levels at the initial visit (Δpre-EWL; P = .02, r = -0.37, P = .01, r = -0.41, P = .008, r = -0.45, Δpre-TWL; P = .01, r = -0.40, P = .01, r = -0.42, P = .01, r = -0.42, respectively). Multivariate regression modeling showed that both Δpre-EWL and Δpre-TWL were significantly associated with lymphocyte count (Δpre-EWL; P = .01, Δpre-TWL; P = .01). A comparison between the high (Δ pre-EWL > 0.098) and low weight loss group (Δ pre-EWL < 0.098) demonstrated a significant difference in the expression of the activation marker CD69 on CD56bright Natural killer (NK) cells (P = .01), whereas there was no difference in the frequency of T cells, Natural killer T cells, or NK cells. Additionally, high CRP levels were associated with CD69 expression in CD56bright NK cells (P = .01, R = 0.57). Peripheral lymphocytes, especially CD69-positive CD56bright NK cells, are involved in preoperative weight loss after bariatric surgery, and systemic inflammation may inhibit weight loss before surgery.

Multifaceted effects of obesity on cancer immunotherapies: Bridging preclinical models and clinical data

Obesity, defined by excessive body fat, is a highly complex condition affecting numerous physiological processes, such as metabolism, proliferation, and cellular homeostasis. These multifaceted effects impact cells and tissues throughout the host, including immune cells as well as cancer biology. Because of the multifaceted nature of obesity, common parameters used to define it (such as body mass index in humans) can be problematic, and more nuanced methods are needed to characterize the pleiotropic metabolic effects of obesity. Obesity is well-accepted as an overall negative prognostic factor for cancer incidence, progression, and outcome. This is in part due to the meta-inflammatory and immunosuppressive effects of obesity. Immunotherapy is increasingly used in cancer therapy, and there are many different types of immunotherapy approaches. The effects of obesity on immunotherapy have only recently been studied with the demonstration of an "obesity paradox", in which some immune therapies have been demonstrated to result in greater efficacy in obese subjects despite the direct adverse effects of obesity and excess body fat acting on the cancer itself. The multifactorial characteristics that influence the effects of obesity (age, sex, lean muscle mass, underlying metabolic conditions and drugs) further confound interpretation of clinical data and necessitate the use of more relevant preclinical models mirroring these variables in the human scenario. Such models will allow for more nuanced mechanistic assessment of how obesity can impact, both positively and negatively, cancer biology, host metabolism, immune regulation, and how these intersecting processes impact the delivery and outcome of cancer immunotherapy.