Diet-induced obesity alters dendritic cell function in the presence and absence of tumor growth

Obesity, white adipose tissue and cancer

White adipose tissue (WAT) is crucial for whole-body energy homeostasis and plays an important role in metabolic and hormonal regulation. While healthy WAT undergoes controlled expansion and contraction to meet the body's requirements, dysfunctional WAT in conditions like obesity is characterized by excessive tissue expansion, alterations in lipid homeostasis, inflammation, hypoxia, and fibrosis. Obesity is strongly associated with an increased risk of numerous cancers, with obesity-induced WAT dysfunction influencing cancer development through various mechanisms involving both systemic and local interactions between adipose tissue and tumors. Unhealthy obese WAT affects circulating levels of free fatty acids and factors like leptin, adiponectin, and insulin, altering systemic lipid metabolism and inducing inflammation that supports tumor growth. Similar mechanisms are observed locally in an adipose-rich tumor microenvironment (TME), where WAT cells can also trigger extracellular matrix remodeling, thereby enhancing the TME's ability to promote tumor growth. Moreover, tumors reciprocally interact with WAT, creating a bidirectional communication that further enhances tumorigenesis. This review focuses on the complex interplay between obesity, WAT dysfunction, and primary tumor growth, highlighting potential targets for therapeutic intervention.

Regulation of CD8+ T cells by lipid metabolism in cancer progression

Dysregulation of lipid metabolism is a key characteristic of the tumor microenvironment, where tumor cells utilize lipids for proliferation, survival, metastasis, and evasion of immune surveillance. Lipid metabolism has become a critical regulator of CD8+ T-cell-mediated antitumor immunity, with excess lipids in the tumor microenvironment impeding CD8+ T-cell activities. Considering the limited efficacy of immunotherapy in many solid tumors, targeting lipid metabolism to enhance CD8+ T-cell effector functions could significantly improve immunotherapy outcomes. In this review, we examine recent findings on how lipid metabolic processes, including lipid uptake, synthesis, and oxidation, regulate CD8+ T cells within tumors. We also assessed the impact of different lipids on CD8+ T-cell-mediated antitumor immunity, with a particular focus on how lipid metabolism affects mitochondrial function in tumor-infiltrating CD8+ T cells. Furthermore, as cancer is a systemic disease, we examined systemic factors linking lipid metabolism to CD8+ T-cell effector function. Finally, we summarize current therapeutic approaches that target lipid metabolism to increase antitumor immunity and enhance immunotherapy. Understanding the molecular and functional interplay between lipid metabolism and CD8+ T cells offers promising therapeutic opportunities for cancer treatment.

Immunotherapy and Overall Survival Among Patients With Advanced Non-Small Cell Lung Cancer and Obesity

IMPORTANCE

The association between obesity and response to cancer treatment and survival remains unclear, with conflicting findings from various studies. The optimal choice between conventional chemotherapy and immunotherapy for first-line treatment remains uncertain in patients with obesity who potentially have an inadequate therapeutic response to immunotherapy.

OBJECTIVE

To investigate whether body mass index (BMI) modifies the association of immunotherapy or conventional therapy with overall survival in patients with advanced non-small cell lung cancer (aNSCLC).

DESIGN, SETTING, and PARTICIPANTS

A retrospective cohort study, using administrative claims data obtained from advanced treatment centers in Japan, was conducted between December 1, 2015, and January 31, 2023. Participants included individuals aged 18 years or older with aNSCLC who received immunotherapy, using immune checkpoint inhibitor (ICI) treatment or conventional chemotherapy.

EXPOSURE

Immune checkpoint inhibitor therapy as first-line chemotherapy was compared with conventional chemotherapy, identified through patient medical records.

MAIN OUTCOMES AND MEASURES

The main outcome was overall survival. Survival analysis covered a 3-year follow-up period after the first-line chemotherapy.

RESULTS

A total of 31 257 patients with aNSCLC were identified. Of these, 12 816 patients received ICI therapy (mean [SD] age, 70.2 [9.1] years; 10 287 [80.3%] men) and 18 441 patients received conventional chemotherapy (mean [SD] age, 70.2 [8.9] years; 14 139 [76.7%] men). Among patients with BMI less than 28, ICI therapy was associated with a significantly lower hazard of mortality (eg, BMI 24: hazard ratio [HR], 0.81; 95% CI, 0.75-0.87) compared with those who underwent conventional chemotherapy. However, no such association was observed among patients with BMI 28 or greater (eg, BMI 28: HR, 0.90; 95% CI, 0.81-1.00).

CONCLUSIONS AND RELEVANCE

The findings of this retrospective cohort study suggest that BMI modifies the association of ICI therapy compared with conventional chemotherapy with overall survival in patients with aNSCLC. A lack of association between ICI therapy and improved survival in patients with aNSCLC and overweight or obesity compared with conventional chemotherapy was observed. This suggests that ICI therapy may not be the optimal first-line therapy for patients with overweight or obesity and the use of conventional chemotherapy should also be considered in such patients.

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.

Obesity, Dietary Fats, and Gastrointestinal Cancer Risk-Potential Mechanisms Relating to Lipid Metabolism and Inflammation

Obesity is a major driving factor in the incidence, progression, and poor treatment response in gastrointestinal cancers. Herein, we conducted a comprehensive analysis of the impact of obesity and its resulting metabolic perturbations across four gastrointestinal cancer types, namely, oesophageal, gastric, liver, and colorectal cancer. Importantly, not all obese phenotypes are equal. Obese adipose tissue heterogeneity depends on the location, structure, cellular profile (including resident immune cell populations), and dietary fatty acid intake. We discuss whether adipose heterogeneity impacts the tumorigenic environment. Dietary fat quality, in particular saturated fatty acids, promotes a hypertrophic, pro-inflammatory adipose profile, in contrast to monounsaturated fatty acids, resulting in a hyperplastic, less inflammatory adipose phenotype. The purpose of this review is to examine the impact of obesity, including dietary fat quality, on adipose tissue biology and oncogenesis, specifically focusing on lipid metabolism and inflammatory mechanisms. This is achieved with a particular focus on gastrointestinal cancers as exemplar models of obesity-associated cancers.

Baicalein enhances immune response in TNBC by inhibiting leptin expression of adipocytes

Triple-negative breast cancer (TNBC) is a special pathological type of breast cancer (BC) with poor prognosis. Obesity is shown to be involved in TNBC tumor progression. The interaction between obesity and BC has generated great attention in recent years, however, the mechanism is still unclear. Here, we showed that leptin secreted by adipocytes upregulated PD-L1 expression in TNBC through the p-STAT3 signaling pathway and that baicalein inhibited PD-L1 expression in tumor microenvironment by suppressing leptin transcription of adipocytes. Collectively, our findings suggest that leptin may be the key factor participating in obesity-related tumor progression and that baicalein can break through the dilemma to boost the anti-tumor immune response.

Diet, nutrient supply, and tumor immune responses

Nutrients are essential for cell function. Immune cells operating in the complex tumor microenvironment (TME), which has a unique nutrient composition, face challenges of adapting their metabolism to support effector functions. We discuss the impact of nutrient availability on immune function in the tumor, competition between immune cells and tumor cells for nutrients, and how this is altered by diet. Understanding which diets can promote antitumor immune responses could open a new era of treatment, where dietary modifications can be used as an adjunct to boost the success of existing cancer therapies.

New insights into the role of adipocytes in pancreatic cancer progression: paving the way towards novel therapeutic targets

Pancreatic cancer (PC) remains one of the most lethal malignancies across the world, which is due to delayed diagnosis and resistance to current therapies. The interactions between pancreatic tumor cells and their tumor microenvironment (TME) allow cancer cells to escape from anti-cancer therapies, leading to difficulties in treating PC. With endocrine function and lipid storage capacity, adipose tissue can maintain energy homeostasis. Direct or indirect interaction between adipocytes and PC cells leads to adipocyte dysfunction characterized by morphological change, fat loss, abnormal adipokine secretion, and fibroblast-like transformation. Various adipokines released from dysfunctional adipocytes have been reported to promote proliferation, invasion, metastasis, stemness, and chemoresistance of PC cells via different mechanisms. Additional lipid outflow from adipocytes can be taken into the TME and thus alter the metabolism in PC cells and surrounding stromal cells. Besides, the trans-differentiation potential enables adipocytes to turn into various cell types, which may give rise to an inflammatory response as well as extracellular matrix reorganization to modulate tumor burden. Understanding the molecular basis behind the protumor functions of adipocytes in PC may offer new therapeutic targets.

Impact of Obesity on the IL-6 Immune Marker and Th17 Immune Cells in C57BL/6 Mice Models with Imiquimod-Induced Psoriasis

Obese psoriatic patients experience higher disease severity and exhibit poorer treatment responses and clinical outcomes. It has been proposed that proinflammatory cytokines produced by adipose tissue exacerbate psoriasis; however, the role of obesity in psoriasis remains unclear. This study aimed to elucidate the role of obesity in the pathogenesis of psoriasis, focusing on immunological changes. To induce obesity, mice were fed a high-fat diet for 20 weeks. We then applied imiquimod to the skin on a mouse’s back for seven consecutive days to induce psoriasis and scored lesion severity every day for seven days. Cytokine levels in serum and the Th17 cell population in the spleen and draining lymph nodes were studied to identify immunological differences. The clinical severity was more remarkable, and histologically the epidermis was also significantly thicker in the obese group. Increased levels of IL-6 and TNF-α were observed in serum after psoriasis. They were elevated to a greater degree, with greater expansion of the functional Th17 cell population in the obese group. It is concluded that obesity could exacerbate psoriasis through mechanisms that involve elevated proinflammatory cytokine secretion and an expanded Th17 cell population.

Diet Influences Immunotherapy Outcomes in Cancer Patients: A Literature Review

The outbreak of immunotherapy has revolutionized cancer treatment. Despite the results confirming the effectiveness of immunotherapy, some studies have reported poor responsiveness to this therapeutic approach. The effectiveness of immunotherapy is dependent on numerous factors related to patients' lifestyles and health status. Diet, as an essential component of lifestyle, plays a major role in determining immunotherapy outcomes. It can significantly influence the body, gut microbiome composition, and metabolism, both in general and in tumor microenvironment. Consuming certain diets has resulted in either improved or worsened outcomes in patients receiving immunotherapy. For example, several recent studies have associated ketogenic, plant-based, and microbiome-favoring diets with promising outcomes. Moreover, obesity and dietary deprivation have impacted immunotherapy responsiveness, yet the studies are inconsistent in this context. This narrative review aims to integrate the results from many articles that have studied the contribution of diet to immunotherapy. We will start by introducing the multiple effects of dietary status on cancer progression and treatment. Then we will proceed to discuss various regimens known to affect immunotherapy outcomes, including ketogenic, high-fiber, and obesity-inducing diets and regimens that either contain or lack specific nutrients. Finally, we will elaborate on how composition of the gut microbiome may influence immunotherapy.

Diverse effects of obesity on antitumor immunity and immunotherapy

Currently, obesity is one of the biggest health burdens facing society because it causes several comorbidities, such as type 2 diabetes, atherosclerosis, and heart disease. Obesity is also linked to multiple types of cancer. Obesity is the second most common preventable cause of cancer after smoking; the rates of obesity are increasing worldwide, as are the rates of obesity-associated cancer. Multiple factors link obesity to cancer, such as increased levels of growth hormones and adipokines, gut dysbiosis, altered tumor metabolism, and chronic low-grade inflammation. More recently, obesity has been shown to also affect the immune response against cancer. In this review we discuss the interplay between obesity, the immune system, and cancer.

Impact of Body Mass Index on Outcomes in an Asian population of Advanced Renal Cell Carcinoma and Urothelial Carcinoma Treated With Immune Checkpoint Inhibitors

OBJECTIVES

To clarify the impact of body mass index (BMI) on treatment outcomes including survival, tumor response, and adverse events (AEs) in patients with advanced renal cell carcinoma (RCC) or urothelial carcinoma (UC) treated with immune checkpoint inhibitors (ICIs) in an Asian population.

METHODS

We retrospectively evaluated 309 patients with advanced RCC or UC who received ICIs between September 2016 and July 2021. The patients were divided into high- (i.e., ≥25 kg/m²) and low-BMI (<25 kg/m²) groups according to the BMI at the time of treatment initiation.

RESULTS

Overall, 57 patients (18.4%) were classified into the high-BMI group. In RCC patients treated with ICIs as first-line therapy or UC treated with pembrolizumab, progression-free survival (PFS) (p = 0.309; p = 0.842), overall survival (OS) (p = 0.701; p = 0.983), and objective response rate (ORR) (p = 0.163; p = 0.553) were comparable between the high- and low-BMI groups. In RCC patients treated with nivolumab monotherapy as later-line therapy, OS (p = 0.101) and ORR (p = 0.102) were comparable, but PFS was significantly longer in the high-BMI group (p = 0.0272). Further, multivariate analysis showed that BMI was not an independent factor of PFS or OS in all the treatment groups (any, p>0.05). As for AE profiles, in nivolumab monotherapy, the rate was significantly higher in the high-BMI group (p = 0.0203), whereas in the other two treatments, the rate was comparable.

CONCLUSIONS

BMI was not associated with survival or response rates of advanced RCC or UC patients treated with ICIs in an Asian population. AEs might frequently develop in high-BMI patients with RCC in nivolumab monotherapy.

Aging augments obesity-induced thymic involution and peripheral T cell exhaustion altering the "obesity paradox"

Introduction

The incidence of obesity, a condition characterized by systemic chronic inflammation, has reached pandemic proportions and is a poor prognostic factor in many pathologic states. However, its role on immune parameters has been diverse and at times contradictory. We have previously demonstrated that obesity can result in what has been called the "obesity paradox" which results in increased T cell exhaustion, but also greater efficacy of immune checkpoint blockade in cancer treatment.

Methods

The role of obesity, particularly in the context of aging, has not been robustly explored using preclinical models. We therefore evaluated how age impacts the immune environment on T cell development and function using diet-induced obese (DIO) mice.

Results

We observed that DIO mice initially displayed greater thymopoiesis but then developed greater thymic involution over time compared to their lean counterparts. Both aging and obesity resulted in increased T cell memory conversion combined with increased expression of T cell exhaustion markers and Treg expansion. This increased T cell immunosuppression with age then resulted in a loss of anti-tumor efficacy by immune checkpoint inhibitors (ICIs) in older DIO mice compared to the younger DIO counterparts.

Discussion

These results suggest that both aging and obesity contribute to T cell dysfunction resulting in increased thymic involution. This combined with increased T cell exhaustion and immunosuppressive parameters affects immunotherapy efficacy reducing the advantage of obesity in cancer immunotherapy responses.

Lactobacillus delbrueckii subsp. bulgaricus strain TCI904 reduces body weight gain, modulates immune response, improves metabolism and anxiety in high fat diet-induced obese mice

The multiple probiotic characteristics of strain TCI904 isolated in this study from natural fermented milk were investigated using a mouse model. TCI904 was identified as Lactobacillus delbrueckii subsp. bulgaricu (LDB), a well-known lactic acid starter bacterium found in yogurt. TCI904 exhibited an outstanding pancreatic lipase inhibition activity among several strains of lactic acid bacteria in vitro. Its in vivo effects were further studied. In a comparison of mice fed a high-fat diet (HFD) and those fed a HFD combined with TCI904 for 9 weeks, differences were observed in various aspects of health, and the adverse effects of a HFD were prevented in the latter group. TCI904 effectively prevented fat and body weight accumulation without reducing food intake; it also modulated innate immunity and increased the level of IgA in feces, reversing the increased blood sugar and insulin levels and attenuated the hyperlipidemia caused by a HFD. Based on biochemical test data, compared with the HFD group, a HFD combined with TCI904 induced significant lowering of insulin resistance indicator, homeostasis model assessment-insulin resistance (HOMA-IR) and atherogenic indices of plasma (AIP), the atherogenic coefficient (AC) and cardiac risk ratio (CRR) and increased the cardioprotective index (CPI). In addition, the administration of TCI904 alleviated mood disorders caused by a HFD. Taking the recommended human dose of TCI904 did not affect the liver or kidney function, indicating that TCI904 has sufficient in vivo safety. Taken together, the results of the present study contributed towards validation of the probiotic benefits of lactic acid starter microflora. Orally taken TCI904 exhibited positive immune- and metabolic-modulating, and anxiolytic properties, especially in HFD-induced obesity.

Immune response to arbovirus infection in obesity

Obesity is a global health problem that affects 650 million people worldwide and leads to diverse changes in host immunity. Individuals with obesity experience an increase in the size and the number of adipocytes, which function as an endocrine organ and release various adipocytokines such as leptin and adiponectin that exert wide ranging effects on other cells. In individuals with obesity, macrophages account for up to 40% of adipose tissue (AT) cells, three times more than in adipose tissue (10%) of healthy weight individuals and secrete several cytokines and chemokines such as interleukin (IL)-1β, chemokine C-C ligand (CCL)-2, IL-6, CCL5, and tumor necrosis factor (TNF)-α, leading to the development of inflammation. Overall, obesity-derived cytokines strongly affect immune responses and make patients with obesity more prone to severe symptoms than patients with a healthy weight. Several epidemiological studies reported a strong association between obesity and severe arthropod-borne virus (arbovirus) infections such as dengue virus (DENV), chikungunya virus (CHIKV), West Nile virus (WNV), and Sindbis virus (SINV). Recently, experimental investigations found that DENV, WNV, CHIKV and Mayaro virus (MAYV) infections cause worsened disease outcomes in infected diet induced obese (DIO) mice groups compared to infected healthy-weight animals. The mechanisms leading to higher susceptibility to severe infections in individuals with obesity remain unknown, though a better understanding of the causes will help scientists and clinicians develop host directed therapies to treat severe disease. In this review article, we summarize the effects of obesity on the host immune response in the context of arboviral infections. We have outlined that obesity makes the host more susceptible to infectious agents, likely by disrupting the functions of innate and adaptive immune cells. We have also discussed the immune response of DIO mouse models against some important arboviruses such as CHIKV, MAYV, DENV, and WNV. We can speculate that obesity-induced disruption of innate and adaptive immune cell function in arboviral infections ultimately affects the course of arboviral disease. Therefore, further studies are needed to explore the cellular and molecular aspects of immunity that are compromised in obesity during arboviral infections or vaccination, which will be helpful in developing specific therapeutic/prophylactic interventions to prevent immunopathology and disease progression in individuals with obesity.

Metabolic regulation of immune responses to cancer

The tumor microenvironment is an ecosystem composed of multiple types of cells, such as tumor cells, immune cells, and cancer-associated fibroblasts. Cancer cells grow faster than non-cancerous cells and consume larger amounts of nutrients. The rapid growth characteristic of cancer cells fundamentally alters nutrient availability in the tumor microenvironment and results in reprogramming of immune cell metabolic pathways. Accumulating evidence suggests that cellular metabolism of nutrients, such as lipids and amino acids, beyond being essential to meet the bioenergetic and biosynthetic demands of immune cells, also regulates a broad spectrum of cellular signal transduction, and influences immune cell survival, differentiation, and anti-tumor effector function. The cancer immunometabolism research field is rapidly evolving, and exciting new discoveries are reported in high-profile journals nearly weekly. Therefore, all new findings in this field cannot be summarized within this short review. Instead, this review is intended to provide a brief introduction to this rapidly developing research field, with a focus on the metabolism of two classes of important nutrients-lipids and amino acids-in immune cells. We highlight recent research on the roles of lipids and amino acids in regulating the metabolic fitness and immunological functions of T cells, macrophages, and natural killer cells in the tumor microenvironment. Furthermore, we discuss the possibility of "editing" metabolic pathways in immune cells to act synergistically with currently available immunotherapies in enhancing anti-tumor immune responses.

The role of lipids in cancer progression and metastasis

Lipids have essential biological functions in the body (e.g., providing energy storage, acting as a signaling molecule, and being a structural component of membranes); however, an excess of lipids can promote tumorigenesis, colonization, and metastatic capacity of tumor cells. To metastasize, a tumor cell goes through different stages that require lipid-related metabolic and structural adaptations. These adaptations include altering the lipid membrane composition for invading other niches and overcoming cell death mechanisms and promoting lipid catabolism and anabolism for energy and oxidative stress protective purposes. Cancer cells also harness lipid metabolism to modulate the activity of stromal and immune cells to their advantage and to resist therapy and promote relapse. All this is especially worrying given the high fat intake in Western diets. Thus, metabolic interventions aiming to reduce lipid availability to cancer cells or to exacerbate their metabolic vulnerabilities provide promising therapeutic opportunities to prevent cancer progression and treat metastasis.

High-Fat Diet-Induced Obesity Alters Dendritic Cell Homeostasis by Enhancing Mitochondrial Fatty Acid Oxidation

Obesity is associated with increased cancer risk and weak responses to vaccination and sepsis treatment. Although dendritic cells (DCs) are fundamental for the initiation and maintenance of competent immune responses against pathogens and tumors, how obesity alters the normal physiology of these myeloid cells remains largely unexplored. In this study, we report that obesity caused by prolonged high-fat diet feeding disrupts the metabolic and functional status of mouse splenic DCs (SpDCs). High-fat diet-induced obesity drastically altered the global transcriptional profile of SpDCs, causing severe changes in the expression of gene programs implicated in lipid metabolism and mitochondrial function. SpDCs isolated from obese mice demonstrated enhanced mitochondrial respiration provoked by increased fatty acid oxidation (FAO), which drove the intracellular accumulation of reactive oxygen species that impaired Ag presentation to T cells. Accordingly, treatment with the FAO inhibitor etomoxir, or antioxidants such as vitamin E or N-acetyl-l-cysteine, restored the Ag-presenting capacity of SpDCs isolated from obese mice. Our findings reveal a major detrimental effect of obesity in DC physiology and suggest that controlling mitochondrial FAO or reactive oxygen species overproduction may help improve DC function in obese individuals.

Lipid-loaded macrophages as new therapeutic target in cancer

Macrophages are main players of the innate immune system. They show great heterogeneity and play diverse functions that include support to development, sustenance of tissue homeostasis and defense against infections. Dysfunctional macrophages have been described in multiple pathologies including cancer. Indeed tumor-associated macrophages (TAMs) are abundant in most tumors and sustain cancer growth, promote invasion and mediate immune evasion. Importantly, lipid metabolism influences macrophage activation and lipid accumulation confers pathogenic features on macrophages. Notably, a subset of lipid-loaded macrophages has been recently identified in many tumor types. Lipid-loaded TAMs support tumor growth and progression and exert immune-suppressive activities. In this review, we describe the role of lipid metabolism in macrophage activation in physiology and pathology and we discuss the impact of lipid accumulation in macrophages in the context of cancer.

The Effects of 1,25(OH)2D3 treatment on Immune Responses and Intracellular Metabolic Pathways of Bone Marrow-Derived Dendritic Cells from Lean and Obese Mice

Vitamin D affects differentiation, maturation, and activation of dendritic cells (DCs). Obesity-related immune dysfunction is associated with metabolic changes in immune cells. Objectives of the study are to investigate the effects of vitamin D and obesity on immune responses and markers related to immunometabolism of bone marrow-derived dendritic cells (BMDCs). Bone marrow cells (BMCs) were isolated from lean and obese mice, and BMDCs were generated by culturing BMCs with rmGM-CSF. BMDCs were treated with 1 or 10 nM of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3), and maturation was induced by LPS (50 ng/mL) stimulation for 24 h. Cell phenotypes, cytokine productions, and expression of proteins and genes involved in Akt/mTOR signaling pathway and glycolytic pathway were determined. 1,25(OH)2D3 treatment inhibited differentiation of BMDCs (CD11c⁺ %), expression of phenotypes related with DC function (MHC class II and CD86) and production of IL-12p70 in both lean and obese mice. The expression of PD-L1 and the ratio of IL-10/IL-12p70 were increased by 1,25(OH)2D3. With 1,25(OH)2D3 treatment, Akt/mTOR signaling pathway was suppressed, and expression of genes related to glycolysis (Glut1, Pfkfb4, Hif1A) was increased. The upregulation of glycolysis-related genes observed with 1,25(OH)2D3 treatment seems to be associated with the induction of tolerogenic features of BMDCs from lean and obese mice, and Hif1A seems to have a potential role in conveying the effect of 1,25(OH)2D3 on glycolysis. This article is protected by copyright. All rights reserved.

Contradictory roles of lipid metabolism in immune response within the tumor microenvironment

Complex interactions between the immune system and tumor cells exist throughout the initiation and development of cancer. Although the immune system eliminates malignantly transformed cells in the early stage, surviving tumor cells evade host immune defense through various methods and even reprogram the anti-tumor immune response to a pro-tumor phenotype to obtain unlimited growth and metastasis. The high proliferation rate of tumor cells increases the demand for local nutrients and oxygen. Poorly organized vessels can barely satisfy this requirement, which results in an acidic, hypoxic, and glucose-deficient tumor microenvironment. As a result, lipids in the tumor microenvironment are activated and utilized as a primary source of energy and critical regulators in both tumor cells and related immune cells. However, the exact role of lipid metabolism reprogramming in tumor immune response remains unclear. A comprehensive understanding of lipid metabolism dysfunction in the tumor microenvironment and its dual effects on the immune response is critical for mapping the detailed landscape of tumor immunology and developing specific treatments for cancer patients. In this review, we have focused on the dysregulation of lipid metabolism in the tumor microenvironment and have discussed its contradictory roles in the tumor immune response. In addition, we have summarized the current therapeutic strategies targeting lipid metabolism in tumor immunotherapy. This review provides a comprehensive summary of lipid metabolism in the tumor immune response.

Adipocyte inflammation and pathogenesis of viral pneumonias: an overlooked contribution

Epidemiological evidence establishes obesity as an independent risk factor for increased susceptibility and severity to viral respiratory pneumonias associated with H1N1 influenza and SARS-CoV-2 pandemics. Given the global obesity prevalence, a better understanding of the mechanisms behind obese susceptibility to infection is imperative. Altered immune cell metabolism and function are often perceived as a key causative factor of dysregulated inflammation. However, the contribution of adipocytes, the dominantly altered cell type in obesity with broad inflammatory properties, to infectious disease pathogenesis remains largely ignored. Thus, skewing of adipocyte-intrinsic cellular metabolism may lead to the development of pathogenic inflammatory adipocytes, which shape the overall immune responses by contributing to either premature immunosenescence, delayed hyperinflammation, or cytokine storm in infections. In this review, we discuss the underappreciated contribution of adipocyte cellular metabolism and adipocyte-produced mediators on immune system modulation and how such interplay may modify disease susceptibility and pathogenesis of influenza and SARS-CoV-2 infections in obese individuals.

The effects of dietary vitamin D supplementation and in vitro 1,25 dihydroxyvitamin D3 treatment on autophagy in bone marrow-derived dendritic cells from high-fat diet-induced obese mice

Obesity is associated with the dysregulation of vitamin D metabolism and altered immune responses in bone marrow-derived dendritic cells (BMDCs). Vitamin D can affect the differentiation, maturation, and activation of dendritic cells (DCs) and regulate autophagy via vitamin D receptor signaling. Autophagy was shown to be involved in the functions of DCs. We investigated the effects of dietary vitamin D supplementation and in vitro 1,25-dihydroxyvitamin D₃ (1,25(OH)₂D₃) treatment on autophagy in BMDCs from control diet (CON)-fed lean and high-fat diet (HFD)-induced obese mice. C57BL/6 male mice were fed CON or HFD with 10% or 45% kcal fat, respectively, supplemented with 1,000 or 10,000 IU vitamin D/kg diet (vDC or vDS) for 12 weeks. BMDCs were generated by culturing bone marrow cells from the mice with 20 ng/mL rmGM-CSF and treated with 1 nM 1,25(OH)₂D₃. Maturation of BMDCs was induced by lipopolysaccharide (50 ng/mL) stimulation. Treatment with 1,25(OH)₂D₃ inhibited the expression of phenotypes related to DC function (MHC class Ⅱ, CD86, CD80) and production of IL-12p70 by BMDCs from control and obese mice, regardless of dietary vitamin D supplementation. LC3Ⅱ/Ⅰ and VPS34 protein levels increased, and p62 expression decreased, after 1,25(OH)₂D₃ treatment of the BMDCs in CON-vDC only. Vdr mRNA levels decreased following 1,25(OH)₂D₃ treatment of BMDCs in the HFD-vDC. In conclusion, autophagy flux was increased by 1,25(OH)₂D₃ treatment of the BMDCs in CON-vDC but not in the HFD-vDC group. This suggests that the decreased expression of Vdr following 1,25(OH)₂D₃ treatment might have affected autophagy flux in BMDCs from obese mice.

Mechanisms by Which Obesity Promotes Acute Graft-Versus-Host Disease in Mice

The efficacy of allogeneic hematopoietic stem cell transplantation (allo-HSCT) is limited by the occurrence of acute and chronic graft-versus-host disease (GVHD). We have recently demonstrated that obesity results in exacerbated acute gastrointestinal GVHD in both mouse models and clinical outcomes due to increased pro-inflammatory cytokine responses and microbiota alterations. We therefore wanted to delineate the role of the various parameters in obesity, adiposity, effects of high-fat (HF) diet, and the role of microbiome on GVHD pathogenesis, by taking advantage of a mouse strain resistant to diet-induced obesity (DIO). Female BALB/c mice are resistant to DIO phenotype with approximately 50% becoming DIO under HF diets. The DIO-susceptible recipients rapidly succumb to acute gut GVHD, whereas the DIO-resistant recipient littermates, which do not become obese, are partially protected from GVHD, indicating that being on HF diet alone contributes to but is not the primary driver of GVHD. Microbiome assessment revealed restricted diversity in both cohorts of mice, but coprophagy normalizes the microbiota in mice housed together. We then individually housed DIO-resistant, DIO-susceptible, and lean control mice. Notably, each of the individually housed groups demonstrates marked restricted diversity that has been shown to occur from the stress of single housing. Despite the restricted microbiome diversity, the GVHD pathogenesis profile remains consistent in the group-housed mice, with the lean control single-housed mice exhibiting no acute GVHD and DIO-resistant recipients showing again partial protection. These results demonstrate that the deleterious effects of obesity on acute gut GVHD are critically dependent on adiposity with the HF diet also playing a lesser role, and the microbiome alterations with obesity instead appear to fuel ongoing acute GVHD processes.

The inflammatory pathogenesis of colorectal cancer

The mutational landscape of colorectal cancer (CRC) does not enable predictions to be made about the survival of patients or their response to therapy. Instead, studying the polarization and activation profiles of immune cells and stromal cells in the tumour microenvironment has been shown to be more informative, thus making CRC a prototypical example of the importance of an inflammatory microenvironment for tumorigenesis. Here, we review our current understanding of how colon cancer cells interact with their microenvironment, comprised of immune cells, stromal cells and the intestinal microbiome, to suppress or escape immune responses and how inflammatory processes shape the immune pathogenesis of CRC.

Implications of Inflammatory States on Dysfunctional Immune Responses in Aging and Obesity

Aging and obesity are two conditions characterized by chronic, low-grade inflammation. While both conditions are also associated with dysfunctional immune responses, the shared and distinct underlying mechanisms are just starting to be uncovered. In fact, recent findings have suggested that the effects of obesity on the immune system can be thought of as a state of accelerated aging. Here we propose that chronic, low-grade inflammation seen in obesity and aging is complex, affects multiple cell types, and results in an altered basal immune state. In aging, part of this altered state is the emergence of regulatory immune populations that lead to further immune dysfunction in an attempt to reduce chronic inflammation. While in obesity, part of the altered state is the effect of expanding adipose tissue on immune cell function. Thus, in this review, we compare, and contrast altered immune states in aging and obesity and discuss their potential contribution to a shared clinical problem- decreased vaccine responsiveness.

Adipose Tissue and Biological Factors. Possible Link between Lymphatic System Dysfunction and Obesity

The World Health Organization (WHO) has recognised obesity as one of the top ten threats to human health. Obesity is not only a state of abnormally increased adipose tissue in the body, but also of an increased release of biologically active metabolites. Moreover, obesity predisposes the development of metabolic syndrome and increases the incidence of type 2 diabetes (T2DM), increases the risk of developing insulin resistance, atherosclerosis, ischemic heart disease, polycystic ovary syndrome, hypertension and cancer. The lymphatic system is a one-directional network of thin-walled capillaries and larger vessels covered by a continuous layer of endothelial cells that provides a unidirectional conduit to return filtered arterial and tissue metabolites towards the venous circulation. Recent studies have shown that obesity can markedly impair lymphatic function. Conversely, dysfunction in the lymphatic system may also be involved in the pathogenesis of obesity. This review highlights the important findings regarding obesity related to lymphatic system dysfunction, including clinical implications and experimental studies. Moreover, we present the role of biological factors in the pathophysiology of the lymphatic system and we propose the possibility of a therapy supporting the function of the lymphatic system in the course of obesity.

Re-Evaluating the Effects of Obesity on Cancer Immunotherapy Outcomes in Renal Cancer: What Do We Really Know?

Obesity has reached global epidemic proportions and its effects on interactions between the immune system and malignancies, particularly as related to cancer immunotherapy outcomes, have come under increasing scrutiny. Although the vast majority of pre-clinical murine studies suggest that host obesity should have detrimental effects on anti-tumor immunity and cancer immunotherapy outcomes, the opposite has been found in multiple retrospective human studies. As a result, acceptance of the "obesity paradox" paradigm, wherein obesity increases cancer risk but then improves patient outcomes, has become widespread. However, results to the contrary do exist and the biological mechanisms that promote beneficial obesity-associated outcomes remain unclear. Here, we highlight discrepancies in the literature regarding the obesity paradox for cancer immunotherapy outcomes, with a particular focus on renal cancer. We also discuss multiple factors that may impact research findings and warrant renewed research attention in future studies. We propose that specific cancer patient populations may be affected in fundamentally different ways by host obesity, leading to divergent effects on anti-tumor immunity and/or immunotherapy outcomes. Continued, thoughtful analysis of this critical issue is therefore needed to permit a more nuanced understanding of the complex effects of host obesity on cancer immunotherapy outcomes in patients with renal cancer or other malignancies.

Obesity Has a Systemic Effect on Immune Cells in Naïve and Cancer-Bearing Mice

Obesity is a major risk factor for developing cancer, with obesity-induced immune changes and inflammation in breast (BC) and colorectal cancer (CRC) providing a potential link between the two. This study investigates systemic effects of obesity on adaptive and innate immune cells in healthy and tumour-bearing mice. Immune cells from lean and obese mice were phenotyped prior to implantation of either BC (C57mg and EO771.LMB) or CRC (MC38) cells as tumour models. Tumour growth rate, tumour-infiltrating lymphocytes (TIL) and peripheral blood immune cell populations were compared between obese and lean mice. In vitro studies showed that naïve obese mice had higher levels of myeloid cells in the bone marrow and bone marrow-derived dendritic cells expressed lower levels of activation markers compared to cells from their lean counterparts. In the tumour setting, BC tumours grew faster in obese mice than in lean mice and lower numbers of TILs as well as higher frequency of exhausted T cells were observed. Data from peripheral blood showed lower levels of myeloid cells in tumour-bearing obese mice. This study highlights that systemic changes to the immune system are relevant for tumour burden and provides a potential mechanism behind the effects of obesity on cancer development and progression in patients.

Real-world effectiveness and safety of direct-acting antivirals in patients with cirrhosis and history of hepatic decompensation: Epi-Ter2 Study

BACKGROUND AND AIMS

The aim of this study was to assess the real-life effectiveness and safety of direct acting antivirals (DAAs) in patients with cirrhosis and history of hepatic decompensation compared to those with compensated cirrhosis.

METHOD

Data of patients treated with DAAs and included in the EpiTer-2 database (N = 10 152) were collected retrospectively. The primary endpoint was sustained viral response (SVR) at 12 weeks posttreatment. Patients were also evaluated in terms of liver-related adverse events and treatment modification/discontinuation.

RESULTS

The overall SVR rate was 91.4% in the intent to treat (ITT) analysis and 95.2% in the per-protocol (PP) analysis (P < .001). Patients with decompensated cirrhosis had lower SVR rates compared to those with compensated cirrhosis in ITT analysis (86.4% vs 92.0%, P < .001), while not in PP analysis (92.9% vs 95.5%, P > .05). Adverse events (AE) occurred 45.6% and 29.3% of patients with decompensated and compensated cirrhosis (P < .001). Patients with decompensated cirrhosis were at higher risk of death (5.4% vs 0.9%; P < .0001) or liver decompensation (21.5% vs 1.3%; P < .0001). Treatment with protease inhibitors was not associated with hepatic decompensation (P = .3). Only 82.6% of patients with decompensated cirrhosis completed DAA treatment (vs 92.8% in compensated cirrhotics; P < .0001).

CONCLUSION

Despite higher frequency of AE and treatment modifications, once completed, DAAs yield comparable results for patients with decompensated and compensated cirrhosis. High rate of serious adverse events in patients with advanced liver disease treated with PI may not be related to the detrimental effect of the medications, but rather to the disease itself.

Obesity and severe coronavirus disease 2019: molecular mechanisms, paths forward, and therapeutic opportunities

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) appears to have higher pathogenicity among patients with obesity. Obesity, termed as body mass index greater than 30 kg/m2, has now been demonstrated to be important comorbidity for disease severity during coronavirus disease 2019 (COVID-19) pandemic and associated with adverse events. Unraveling mechanisms behind this phenomenon can assist scientists, clinicians, and policymakers in responding appropriately to the COVID-19 pandemic. In this review, we systemically delineated the potential mechanistic links between obesity and worsening COVID-19 from altered physiology, underlying diseases, metabolism, immunity, cytokine storm, and thrombosis. Problematic ventilation caused by obesity and preexisting medical disorders exacerbate organ dysfunction for patients with obesity. Chronic metabolic disorders, including dyslipidemia, hyperglycemia, vitamin D deficiency, and polymorphisms of metabolism-related genes in obesity, probably aid SARS-CoV-2 intrusion and impair antiviral responses. Obesity-induced inadequate antiviral immunity (interferon, natural killer cells, invariant natural killer T cell, dendritic cell, T cells, B cell) at the early stage of SARS-CoV-2 infection leads to delayed viral elimination, increased viral load, and expedited viral mutation. Cytokine storm, with the defective antiviral immunity, probably contributes to tissue damage and pathological progression, resulting in severe symptoms and poor prognosis. The prothrombotic state, driven in large part by endothelial dysfunction, platelet hyperactivation, hypercoagulability, and impaired fibrinolysis in obesity, also increases the risk of severe COVID-19. These mechanisms in the susceptibility to severe condition also open the possibility for host-directed therapies in population with obesity. By bridging work done in these fields, researchers can gain a holistic view of the paths forward and therapeutic opportunities to break the vicious cycle of obesity and its devastating complications in the next emerging pandemic.

Metabolic regulation in the immune response to cancer

Metabolic reprogramming in tumor‐immune interactions is emerging as a key factor affecting pro‐inflammatory carcinogenic effects and anticancer immune responses. Therefore, dysregulated metabolites and their regulators affect both cancer progression and therapeutic response. Here, we describe the molecular mechanisms through which microenvironmental, systemic, and microbial metabolites potentially influence the host immune response to mediate malignant progression and therapeutic intervention. We summarized the primary interplaying factors that constitute metabolism, immunological reactions, and cancer with a focus on mechanistic aspects. Finally, we discussed the possibility of metabolic interventions at multiple levels to enhance the efficacy of immunotherapeutic and conventional approaches for future anticancer treatments.

Diet-Induced Obesity Impairs Outcomes and Induces Multi-Factorial Deficiencies in Effector T Cell Responses Following Anti-CTLA-4 Combinatorial Immunotherapy in Renal Tumor-Bearing Mice

Simple Summary

Immunotherapy use has become standard for many patients with advanced kidney cancer; unfortunately, <50% of patients experience durable responses. Mounting evidence suggests that modifiable factors, such as diet and obesity, impact immunotherapy outcomes. Obesity, a major U.S. health epidemic, blunts anti-tumor immunity and promotes tumor growth in multiple preclinical models. However, the full biological impact of obesity on the T cell responses needed to achieve positive immunotherapy outcomes remains unclear. Here, we studied the effects of obesity on T cell responses following combinatorial immunotherapy in a mouse model of kidney cancer. We found that obesity is associated with blunted effector T cell responses, resulting in diminished immunotherapy outcomes. This therapy produces sustained T cell responses and robust tumor control in obese-resistant mice fed the same high-fat diet. Finding ways to amplify T cell responses within renal tumors from hosts with obesity will be critical for achieving optimal immunotherapy outcomes.

Abstract

Associations between modifiable factors and the efficacy of cancer immunotherapies remain uncertain. We found previously that diet-induced obesity (DIO) reduces the efficacy of an immunotherapy consisting of adenovirus-encoded TRAIL plus CpG oligonucleotide (AdT/CpG) in mice with renal tumors. To eliminate confounding effects of diet and determine whether outcomes could be improved in DIO mice, we evaluated AdT/CpG combined with anti-CTLA-4 in diet-matched, obese-resistant (OB-RES) versus DIO tumor-bearing mice. Therapy-treated OB-RES mice displayed effective renal tumor control and sustained CD4⁺ and CD8⁺ T cell responses. In contrast, therapy-treated DIO mice exhibited progressive tumor outgrowth and blunted T cell responses, characterized by reduced intratumoral frequencies of IFNγ⁺ CD4⁺ and CD8⁺ T cells. Weak effector T cell responses in therapy-treated DIO mice were accompanied by low intratumoral concentrations of the T cell chemoattractant CCL5, heightened concentrations of pro-tumorigenic GM-CSF, and impaired proliferative capacity of CD44⁺CD8⁺ T cells in tumor-draining lymph nodes. Our findings demonstrate that in lean mice with renal tumors, combining in situ T cell priming upstream of anti-CTLA-4 enhances outcomes versus anti-CTLA-4 alone. However, host obesity is associated with heightened immunotherapy resistance, characterized by multi-factorial deficiencies in effector CD4⁺ and CD8⁺ T cell responses that extend beyond the tumor microenvironment.

A synergy of estradiol with leptin modulates the long non-coding RNA NEAT1/ mmu-miR-204-5p/IGF1 axis in the uterus of high-fat-diet-induced obese ovariectomized mice

Obesity increases the risk of developing cancers for both males and females. This study investigated potential crosstalk between estradiol and leptin signaling pathways within the endometrium of high-fat-diet-induced obese ovariectomized mice to gain insight into possible links between obesity and endometrial cancer. We administered 17-β estradiol (0.2 μg/mouse subcutaneously) and/or recombinant mouse leptin (1 μg/g Bwt intraperitoneally.,) for 20 h to high-fat-diet-induced obese ovariectomized mice. The uterine tissues of experimental animals after treatments were studied by histological, immunohistochemical, quantitative real-time PCR (gene/miRNAs), and methylation-specific PCR analyses. Quantitative real-time PCR analysis revealed significantly increased expression of Cyclin d1, Esr1, Igf1, Igfbp2, Vegf, Oct4, and Pgr after estradiol and leptin co-treatment. Methylation-specific PCR results indicated that the hormonal dependent transcriptional regulation of Vegf, Igf1, and Pgr is independent of promoter methylation. The decreased expression of mmu- miR-204-5p after estradiol and leptin treatments correlated with the increased expression of long non-coding RNA Neat1. Insilico analysis confirmed the interaction of Neat1 and mmu- miR-204-5p and gene targets of mmu-miR-204-5p, including Igf1 were analyzed in this study. Immunohistochemical analyses revealed subcellular localization and increased expression of ESR, VEGF, phospho-Estrogen Receptor-α (pTyr537), and LEPR proteins following estradiol and leptin exposure. Overall, the data from our in vivo studies suggest the regulation of Neat1-mmu-miR-204-5p- Igf1 axis and associated gene expression changes in uterine tissue after estradiol and leptin co-treatment. In humans, long-term exposure to estradiol and leptin can alter endometrial homeostasis through the NEAT1-miR-204-5p-Igf1 axis and favor carcinogenic pathways, which provide mechanistic insight into the obesity-associated endometrial cancer.

Development of a highly pulmonary metastatic orthotopic renal cell carcinoma murine model

The incidence of renal cell carcinoma (RCC) is high, and its outcomes remain poor. Mortality is attributable largely to metastatic disease and a dearth of effective therapeutic interventions. The lungs are the most common metastatic site. To elucidate the biological mechanisms underlying pulmonary metastasis and identify superior therapeutic strategies, we developed a novel and clinically relevant murine RCC model exhibiting enhanced pulmonary metastasis. Mice underwent intrarenal implantation using luciferase-expressing Renca, a murine renal adenocarcinoma cell line. Primary renal tumor progression and development of metastatic lung lesions were monitored in live mice using bioluminescent imaging, followed by post-mortem organ assessment. Cells were isolated from pulmonary metastases for reimplantation, followed by repeat monitoring and assessment. This process was repeated once more for a total of two in vivo passages to select for pulmonary metastatic Renca cell subpopulations. However, a single round of in vivo selection was sufficient to produce a near-maximally metastatic subpopulation. Relative to Renca cell-implanted mice, subpopulation-implanted mice exhibited shorter implantation-metastasis intervals (5 days), shorter implantation-moribundity intervals (sacrificed at 18.6±2.9 versus 22.3±1.1 days), a higher number of metastatic lung lesions at 23 days (183.9±39.0 versus 172.6±38.2) and poorer survival. Implantation of cells derived from the second round of in vivo selection produced no further significant differences in the above metrics. This model consistently and efficiently recapitulates RCC pulmonary metastasis while allowing in vivo monitoring of tumor progression, thereby facilitating elucidation of the molecular mechanisms underlying pulmonary metastasis and evaluation of therapeutic modalities.

Cellular mechanisms linking cancers to obesity

Obesity is epidemiologically linked to 13 forms of cancer. The local and systemic obese environment is complex and likely affect tumors through multiple avenues. This includes modulation of cancer cell phenotypes and the composition of the tumor microenvironment. A molecular understanding of how obesity links to cancer holds promise for identifying candidate genes for targeted therapy for obese cancer patient. Herein, we review both the cell-autonomous and non-cell-autonomous mechanisms linking obesity and cancer as well as provide an overview of the mouse model systems applied to study this.

The role of immune dysfunction in obesity-associated cancer risk, progression, and metastasis

Obesity has been linked to an increased risk of and a worse prognosis for several types of cancer. A number of interrelated mediators contribute to obesity's pro-tumor effects, including chronic adipose inflammation and other perturbations of immune cell development and function. Here, we review studies examining the impact of obesity-induced immune dysfunction on cancer risk and progression. While the role of adipose tissue inflammation in obesity-associated cancer risk has been well characterized, the effects of obesity on immune cell infiltration and activity within the tumor microenvironment are not well studied. In this review, we aim to highlight the impact of both adipose-mediated inflammatory signaling and intratumoral immunosuppressive signaling in obesity-induced cancer risk, progression, and metastasis.

Fructose Promotes Cytoprotection in Melanoma Tumors and Resistance to Immunotherapy

Checkpoint blockade immunotherapy relies on the empowerment of the immune system to fight cancer. Why some patients fail to achieve durable clinical responses is not well understood, but unique individual factors such as diet, obesity, and related metabolic syndrome could play a role. The link between obesity and patient outcomes remains controversial and has been mired by conflicting reports and limited mechanistic insight. We addressed this in a C57BL/6 mouse model of diet-induced obesity using a Western diet high in both fats and sugars. Obese mice bearing B16 melanoma or MC38 carcinoma tumors had impaired immune responses to immunotherapy and a reduced capacity to control tumor progression. Unexpectedly, these compromised therapeutic outcomes were independent of body mass and, instead, were directly attributed to dietary fructose. Melanoma tumors in mice on the high-fructose diet were resistant to immunotherapy and showed increased expression of the cytoprotective enzyme heme oxygenase-1 (HO-1). This increase in HO-1 protein was recapitulated in human A375 melanoma cells exposed to fructose in culture. Induced expression of HO-1 shielded tumor cells from immune-mediated killing and was critical for resistance to checkpoint blockade immunotherapy, which could be overcome in vivo using a small-molecule inhibitor of HO-1. This study reveals dietary fructose as a driver of tumor immune evasion, identifying HO-1 expression as a mechanism of resistance and a promising molecular target for combination cancer immunotherapy.See article by Khojandi et al., p. 214.

Oxidized Lipoproteins Promote Resistance to Cancer Immunotherapy Independent of Patient Obesity

Antitumor immunity is impaired in obese mice. Mechanistic insight into this observation remains sparse and whether it is recapitulated in patients with cancer is unclear because clinical studies have produced conflicting and controversial findings. We addressed this by analyzing data from patients with a diverse array of cancer types. We found that survival after immunotherapy was not accurately predicted by body mass index or serum leptin concentrations. However, oxidized low-density lipoprotein (ox-LDL) in serum was identified as a suppressor of T-cell function and a driver of tumor cytoprotection mediated by heme oxygenase-1 (HO-1). Analysis of a human melanoma gene expression database showed a clear association between higher HMOX1 (HO-1) expression and reduced progression-free survival. Our in vivo experiments using mouse models of both melanoma and breast cancer revealed HO-1 as a mechanism of resistance to anti-PD1 immunotherapy but also exposed HO-1 as a vulnerability that could be exploited therapeutically using a small-molecule inhibitor. In conclusion, our clinical data have implicated serum ox-LDL as a mediator of therapeutic resistance in patients with cancer, operating as a double-edged sword that both suppressed T-cell immunity and simultaneously induced HO-1-mediated tumor cell protection. Our studies also highlight the therapeutic potential of targeting HO-1 during immunotherapy, encouraging further translational development of this combination approach.See article by Kuehm et al., p. 227.

Obesity diminishes response to PD-1-based immunotherapies in renal cancer

BACKGROUND

Obesity is a major risk factor for renal cancer, yet our understanding of its effects on antitumor immunity and immunotherapy outcomes remains incomplete. Deciphering these associations is critical, given the growing clinical use of immune checkpoint inhibitors for metastatic disease and mounting evidence for an obesity paradox in the context of cancer immunotherapies, wherein obese patients with cancer have improved outcomes.

METHODS

We investigated associations between host obesity and anti-programmed cell death (PD-1)-based outcomes in both renal cell carcinoma (RCC) subjects and orthotopic murine renal tumors. Overall survival (OS) and progression-free survival (PFS) were determined for advanced RCC subjects receiving standard of care anti-PD-1 who had ≥6 months of follow-up from treatment initiation (n=73). Renal tumor tissues were collected from treatment-naive subjects categorized as obese (body mass index, 'BMI' ≥30 kg/m2) or non-obese (BMI <30 kg/m2) undergoing partial or full nephrectomy (n=19) then used to evaluate the frequency and phenotype of intratumoral CD8+ T cells, including PD-1 status, by flow cytometry. In mice, antitumor immunity and excised renal tumor weights were evaluated ±administration of a combinatorial anti-PD-1 therapy. For a subset of murine renal tumors, immunophenotyping was performed by flow cytometry and immunogenetic profiles were evaluated via nanoString.

RESULTS

With obesity, RCC patients receiving anti-PD-1 administration exhibited shorter PFS (p=0.0448) and OS (p=0.0288). Treatment-naive renal cancer subjects had decreased frequencies of tumor-infiltrating PD-1highCD8+ T cells, a finding recapitulated in our murine model. Following anti-PD-1-based immunotherapy, both lean and obese mice possessed distinct populations of treatment responders versus non-responders; however, obesity reduced the frequency of treatment responders (73% lean vs 44% obese). Tumors from lean and obese treatment responders displayed similar immunogenetic profiles, robust infiltration by PD-1int interferon (IFN)γ+CD8+ T cells and reduced myeloid-derived suppressor cells (MDSC), yielding favorable CD44+CD8+ T cell to MDSC ratios. Neutralizing interleukin (IL)-1β in obese mice improved treatment response rates to 58% and reduced MDSC accumulation in tumors.

CONCLUSIONS

We find that obesity is associated with diminished efficacy of anti-PD-1-based therapies in renal cancer, due in part to increased inflammatory IL-1β levels, highlighting the need for continued study of this critical issue.

The effects of age and systemic metabolism on anti-tumor T cell responses

Average age and obesity prevalence are increasing globally. Both aging and obesity are characterized by profound systemic metabolic and immunologic changes and are cancer risk factors. The mechanisms linking age and body weight to cancer are incompletely understood, but recent studies have provided evidence that the anti-tumor immune response is reduced in both conditions, while responsiveness to immune checkpoint blockade, a form of cancer immunotherapy, is paradoxically intact. Dietary restriction, which promotes health and lifespan, may enhance cancer immunity. These findings illustrate that the systemic context can impact anti-tumor immunity and immunotherapy responsiveness. Here, we review the current knowledge of how age and systemic metabolic state affect the anti-tumor immune response, with an emphasis on CD8+ T cells, which are key players in anti-tumor immunity. A better understanding of the underlying mechanisms may lead to novel therapies enhancing anti-tumor immunity in the context of aging or metabolic dysfunction.

The Antidiabetic Agent Acarbose Improves Anti-PD-1 and Rapamycin Efficacy in Preclinical Renal Cancer

Simple Summary

Although immune-stimulatory and targeted therapies benefit many patients with metastatic kidney cancer, a sizeable proportion of patients fail to respond. Recent studies in mice demonstrate that nutrient-limiting dietary interventions can improve responses to chemotherapy. However, these studies did not investigate effects on metastasis, and the impact of these interventions on the response to immunotherapy or targeted therapies in kidney cancer is unknown. We therefore studied the effects of a glucose-limiting drug called acarbose, which is used to treat type 2 diabetes, in a spontaneously-metastasizing mouse model of kidney cancer. We found that acarbose slowed kidney cancer growth and promoted protective immune responses. In combination with either an immunotherapy or a targeted therapy used clinically to treat kidney cancer, acarbose led to improved treatment outcomes and reduced lung metastases. Our findings contribute to the emerging idea of using nutrition-based interventions to enhance responses to cancer treatments.

Abstract

Although immune checkpoint inhibitors and targeted therapeutics have changed the landscape of treatment for renal cell carcinoma (RCC), most patients do not experience significant clinical benefits. Emerging preclinical studies report that nutrition-based interventions and glucose-regulating agents can improve therapeutic efficacy. However, the impact of such agents on therapeutic efficacy in metastatic kidney cancer remains unclear. Here, we examined acarbose, an alpha-glucosidase inhibitor and antidiabetic agent, in a preclinical model of metastatic kidney cancer. We found that acarbose blunted postprandial blood glucose elevations in lean, nondiabetic mice and impeded the growth of orthotopic renal tumors, an outcome that was reversed by exogenous glucose administration. Delayed renal tumor outgrowth in mice on acarbose occurred in a CD8 T cell-dependent manner. Tumors from these mice exhibited increased frequencies of CD8 T cells that retained production of IFNγ, TNFα, perforin, and granzyme B. Combining acarbose with either anti-PD-1 or the mammalian target of rapamycin inhibitor, rapamycin, significantly reduced lung metastases relative to control mice on the same therapies. Our findings in mice suggest that combining acarbose with current RCC therapeutics may improve outcomes, warranting further study to determine whether acarbose can achieve similar responses in advanced RCC patients in a safe and likely cost-effective manner.

Therapeutic Time-restricted Feeding Reduces Renal Tumor Bioluminescence in Mice but Fails to Improve Anti-CTLA-4 Efficacy

BACKGROUND/AIM

Dietary interventions like time-restricted feeding (TRF) show promising anti-cancer properties. We examined whether therapeutic TRF alone or combined with immunotherapy would diminish renal tumor growth in mice of varying body weights.

MATERIALS AND METHODS

Young (7 week) chow-fed or older (27 week) high-fat diet (HFD)-fed BALB/c mice were orthotopically injected with renal tumor cells expressing luciferase. After tumor establishment, mice were randomized to ad libitum feeding or TRF +/- anti-CTLA-4. Body composition, tumor viability and growth, and immune responses were quantified.

RESULTS

TRF alone reduced renal tumor bioluminescence in older HFD-fed, but not young chow-fed mice. In the latter, TRF mitigated tumor-induced loss of lean- and fat-mass. However, TRF did not alter excised renal tumor weights or intratumoral immune responses and failed to improve anti-CTLA-4 outcomes in any mice.

CONCLUSION

Therapeutic TRF exhibits modest anti-cancer properties but fails to improve anti-CTLA-4 immune checkpoint blockade in murine renal cancer.

Maternal Obesity Does Not Exacerbate the Effects of LPS Injection on Pregnancy Outcomes in Mice

Obesity increases the risk of a number of pregnancy complications, potentially due to chronic inflammation. We predicted that an obesogenic high-fat diet (HFD) in mice would create an inflammatory environment that would exacerbate the effects of lipopolysaccharide (LPS), an inflammatory insult, administered during pregnancy. Females were placed on a HFD or a low-fat diet (LFD) prior to mating, injected with 2 µg LPS or control on gestational day 7 and collected on day 14. Treatment with LPS increased the odds that a female thought to be pregnant at injection had no conceptuses at day 14 (p = 0.024), suggesting that injection with LPS was more likely to induce complete abortion. However, there was no effect of diet on the odds of having no conceptuses at day 14 and no interaction between diet and LPS injection. Diet and LPS injection had no effect on the number of viable fetuses in females still pregnant at day 14. For fetal weight, there was a significant interaction between diet and treatment (p = 0.017), whereby LPS reduced fetal weight in HFD females but not in LFD females. However, LPS treatment of HFD females reduced fetal weight to that observed in control-injected LFD females. Although LPS increased the odds of abortion, there was little evidence that a HFD exacerbated the effects of LPS.

Is Host Metabolism the Missing Link to Improving Cancer Outcomes?

For the past 100 years, oncologists have relentlessly pursued the destruction of tumor cells by surgical, chemotherapeutic or radiation oncological means. Consistent with this focus, treatment plans are typically based on key characteristics of the tumor itself such as disease site, histology and staging based on local, regional and systemic dissemination. Precision medicine is similarly built on the premise that detailed knowledge of molecular alterations of tumor cells themselves enables better and more effective tumor cell destruction. Recently, host factors within the tumor microenvironment including the vasculature and immune systems have been recognized as modifiers of disease progression and are being targeted for therapeutic gain. In this review, we argue that—to optimize the impact of old and new treatment options—we need to take account of an epidemic that occurs independently of—but has major impact on—the development and treatment of malignant diseases. This is the rapidly increasing number of patients with excess weight and its’ attendant metabolic consequences, commonly described as metabolic syndrome. It is well established that patients with altered metabolism manifesting as obesity, metabolic syndrome and chronic inflammation have an increased incidence of cancer. Here, we focus on evidence that these patients also respond differently to cancer therapy including radiation and provide a perspective how exercise, diet or pharmacological agents may be harnessed to improve therapeutic responses in this patient population.

The intrinsic and extrinsic elements regulating inflammation

Inflammation is a sophisticated biological tissue response to both extrinsic and intrinsic stimuli. Although the pathological aspects of inflammation are well appreciated, there are still rooms for understanding the physiological functions of the inflammation. Recent studies have focused on mechanisms, context and the role of physiological inflammation. Besides, there have been progress in the comprehension of commensal microbiota, immunometabolism, cancer and intracellular signaling events' roles that impact on the regulation of inflammation. Despite the fact that inflammatory responses are vital through tissue damage, understanding the mechanisms to turn off the finished or unnecessary inflammation is crucial for restoring homeostasis. Inflammation seems to be a smart process that acts like two edges of a sword, meaning that it has both protective and deleterious consequences. Knowing both edges and the regulation processes will help the future understanding and therapy for various diseases.

The effects of 1,25-dihydroxyvitamin D3 on markers related to the differentiation and maturation of bone marrow-derived dendritic cells from control and obese mice

Vitamin D has been reported to regulate the maturation and function of dendritic cells (DCs). Obesity was shown to be associated with the dysregulation of vitamin D metabolism and malfunction of DCs. We investigated the effects of in vitro 1,25(OH)₂D₃ treatment (0, 1, or 10 nM) on phenotype and expression of genes related to function of bone marrow-derived DCs (BMDCs) from control and obese mice. C57BL/6 N mice were fed a control or high-fat (10% or 45% kcal fat: CON or HFD) diets for 15 weeks. Differentiation toward DCs was induced with GM-CSF (20 ng/ml) and maturation was induced by LPS (50 ng/ml); 10 nM 1,25(OH)₂D₃ treatment inhibited BMDC differentiation (CD11c⁺) and decreased the percentage of mature DCs (MHCII^highCD11c⁺ and CD86^highCD11c⁺) in both CON and HFD groups. The Il10 expression in stimulated BMDCs from the CON group increased with the 10 nM 1,25(OH)₂D₃ treatment, but not in those from the HFD group. The Il12b mRNA levels in stimulated BMDCs were lower in the HFD group than in the CON group. In conclusion, lower levels of Cd 40, Cd83 and Il12 mRNA in LPS-stimulated BMDCs from obese mice suggest malfunction of DCs as antigen presenting cells. 1,25(OH)₂D₃ treatment inhibited the differentiation and maturation of BMDCs in both control and obese mice. Differential effects of 1,25(OH)₂D₃ on the expression of Il10 between control and obese mice suggest that regulation of immune response by vitamin D could be influenced by obesity.