Genetic ablation of adipocyte PD-L1 reduces tumor growth but accentuates obesity-associated inflammation

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 dysfunction-associated profiles and subsequent site-specific risk of obesity-related cancers among Chinese patients with diabetes: a retrospective cohort study

OBJECTIVES

To compare metabolic dysfunction-associated profiles between patients with diabetes who developed different obesity-related site-specific cancers and those who remained free of cancer during follow-up.

DESIGN

Retrospective cohort study.

SETTING

Public general outpatient clinics in Hong Kong.

PARTICIPANTS

Patients with diabetes without a history of malignancy (n=391 921).

PRIMARY OUTCOME MEASURES

The outcomes of interest were diagnosis of site-specific cancers (colon and rectum, liver, pancreas, bladder, kidney and stomach) during follow-up. Cox proportional hazards regression was applied to assess the associations between metabolic dysfunction and other clinical factors with each site-specific cancer.

RESULTS

Each 0.1 increase in waist-to-hip ratio was associated with an 11%-35% elevated risk of colorectal, bladder and liver cancers. Each 1% increase in glycated haemoglobin was linked to a 4%-9% higher risk of liver and pancreatic cancers. While low-density lipoprotein cholesterol and triglycerides were inversely associated with the risk of liver and pancreatic cancers, high-density lipoprotein cholesterol was negatively associated with pancreatic, gastric and kidney cancers, but positively associated with liver cancer. Furthermore, liver cirrhosis was linked to a 56% increased risk of pancreatic cancer. No significant association between hypertension and cancer risk was found.

CONCLUSIONS

Metabolic dysfunction-associated profiles contribute to different obesity-related cancer outcomes differentially among patients with diabetes. This study may provide evidence to help identify cancer prevention targets during routine diabetes care.

Immunoregulation in cancer-associated cachexia

BACKGROUND

Cancer-associated cachexia is a multi-organ disorder associated with progressive weight loss due to a variable combination of anorexia, systemic inflammation and excessive energy wasting. Considering the importance of immunoregulation in cachexia, it still lacks a complete understanding of the immunological mechanisms in cachectic progression.

AIM OF REVIEW

Our aim here is to describe the complex immunoregulatory system in cachexia. We summarize the effects and translational potential of the immune system on the development of cancer-associated cachexia and we attempt to conclude with thoughts on precise and integrated therapeutic strategies under the complex immunological context of cachexia.

KEY SCIENTIFIC CONCEPTS OF REVIEW

This review is focused on three main key concepts. First, we highlight the inflammatory factors and additional mediators that have been identified to modulate this syndrome. Second, we decipher the potential role of immune checkpoints in tissue wasting. Third, we discuss the multilayered insights in cachexia through the immunometabolic axis, immune-gut axis and immune-nerve axis.

The CD27/CD70 pathway negatively regulates visceral adipose tissue-resident Th2 cells and controls metabolic homeostasis

Adipose tissue homeostasis relies on the interplay between several regulatory lineages, such as type 2 innate lymphoid cells (ILC2s), T helper 2 (Th2) cells, regulatory T cells, eosinophils, and type 2 macrophages. Among them, ILC2s are numerically the dominant source of type 2 cytokines and are considered as major regulators of adiposity. Despite the overlap in immune effector molecules and sensitivity to alarmins (thymic stromal lymphopoietin and interleukin-33) between ILC2s and resident memory Th2 lymphocytes, the role of the adaptive axis of type 2 immunity remains unclear. We show that mice deficient in CD27, a member of the tumor necrosis factor receptor superfamily, are more resistant to obesity and associated disorders. A comparative analysis of the CD4 compartment of both strains revealed higher numbers of fat-resident memory Th2 cells in the adipose tissue of CD27 knockout mice, which correlated with decreased programmed cell death protein 1-induced apoptosis. Our data point to a non-redundant role for Th2 lymphocytes in obesogenic conditions.

Perspectives in Immunotherapy: meeting report from Immunotherapy Bridge (Naples, November 30th-December 1st, 2022)

The discovery and development of novel treatments that harness the patient's immune system and prevent immune escape has dramatically improved outcomes for patients across cancer types. However, not all patients respond to immunotherapy, acquired resistance remains a challenge, and responses are poor in certain tumors which are considered to be immunologically cold. This has led to the need for new immunotherapy-based approaches, including adoptive cell transfer (ACT), therapeutic vaccines, and novel immune checkpoint inhibitors. These new approaches are focused on patients with an inadequate response to current treatments, with emerging evidence of improved responses in various cancers with new immunotherapy agents, often in combinations with existing agents. The use of cell therapies, drivers of immune response, and trends in immunotherapy were the focus of the Immunotherapy Bridge (November 30th-December 1st, 2022), organized by the Fondazione Melanoma Onlus, Naples, Italy, in collaboration with the Society for Immunotherapy of Cancer.

Drastic transformation of visceral adipose tissue and peripheral CD4 T cells in obesity

Obesity has a pronounced effect on the immune response in systemic organs that results in not only insulin resistance but also altered immune responses to infectious diseases and malignant tumors. Obesity-associated microenvironmental changes alter transcriptional expression and metabolism in T cells, leading to alterations in T-cell differentiation, proliferation, function, and survival. Adipokines, cytokines, and lipids derived from obese visceral adipose tissue (VAT) may also contribute to the systemic T-cell phenotype, resulting in obesity-specific pathogenesis. VAT T cells, which have multiple roles in regulating homeostasis and energy utilization and defending against pathogens, are most susceptible to obesity. In particular, many studies have shown that CD4 T cells are deeply involved in the homeostasis of VAT endocrine and metabolic functions and in obesity-related chronic inflammation. In obesity, macrophages and adipocytes in VAT function as antigen-presenting cells and contribute to the obesity-specific CD4 T-cell response by inducing CD4 T-cell proliferation and differentiation into inflammatory effectors via interactions between major histocompatibility complex class II and T-cell receptors. When obesity persists, prolonged stimulation by leptin and circulating free fatty acids, repetitive antigen stimulation, activating stress responses, and hypoxia induce exhaustion of CD4 T cells in VAT. T-cell exhaustion is characterized by restricted effector function, persistent expression of inhibitory receptors, and a transcriptional state distinct from functional effector and memory T cells. Moreover, obesity causes thymic regression, which may result in homeostatic proliferation of obesity-specific T-cell subsets due to changes in T-cell metabolism and gene expression in VAT. In addition to causing T-cell exhaustion, obesity also accelerates cellular senescence of CD4 T cells. Senescent CD4 T cells secrete osteopontin, which causes further VAT inflammation. The obesity-associated transformation of CD4 T cells remains a negative legacy even after weight loss, causing treatment resistance of obesity-related conditions. This review discusses the marked transformation of CD4 T cells in VAT and systemic organs as a consequence of obesity-related microenvironmental changes.

Immune checkpoint inhibitors and their impact on liver enzymes and attenuation

BACKGROUND

Immune related adverse events impacting the liver are common from immune checkpoint inhibitor (ICI) therapy; however, there is little data regarding the subclinical impact of ICIs on liver inflammation. The study aims to determine whether ICI therapy affects liver attenuation and liver enzymes in melanoma patients with and without hepatic steatosis.

METHODS

A retrospective, cohort study was conducted of patients with advanced melanoma treated with ICI therapy who received serial PET-CT scans at the Vanderbilt University Medical Center (VUMC). Primary outcomes included: liver attenuation measured by PET-CT/non-contrast CT and liver enzymes. Hepatic steatosis was diagnosed by radiologists on clinical imaging.

RESULTS

Among 839 patients with advanced melanoma treated with ICIs, 81 had serial PET-CT scans approximately 12 months apart and long-term survival; of these 11 patients had pre-existing steatosis/steatohepatitis. Overall, ICI was not associated with significant increases in liver enzymes in all patients; modest decreases in liver enzymes were observed in patients with pre-existing steatosis/steatohepatitis. Similarly, liver attenuation did not change from baseline to post-treatment (58.44 vs 60.60 HU, + 2.17, p = 0.055).

CONCLUSIONS

ICIs may not chronically affect liver enzymes or liver attenuation, a non-invasive measure of liver fat content and inflammation, in the general population or in those with pre-existing steatosis/steatohepatitis.

Generation, secretion and degradation of cancer immunotherapy target PD-L1

Cancer immunotherapy is a rapidly developing and effective method for the treatment of a variety of malignancies in recent years. As a significant immune checkpoint, programmed cell death 1 ligand 1 (PD-L1) and its receptor programmed cell death protein 1 (PD-1) play the most significant role in cancer immune escape and cancer immunotherapy. Though PD-L1 have become an important target for drug development and there have been various approved drugs and clinic trials targeting it, and various clinical response rate and adverse reactions prevent many patients from benefiting from it. In recent years, combination trials have become the main direction of PD-1/PD-L1 antibodies development. Here, we summarized PD-L1 biofunctions and key roles in various cancers along with the development of PD-L1 inhibitors. The regulators that are involved in controlling PD-L1 expression including post-translational modification, mRNA level regulation as well as degradation and exosome secretory pathway of PD-L1 were focused. This systematic summary may provide comprehensive understanding of different regulations on PD-L1 as well as a broad prospect for the search of the important regulator of PD-L1. The regulatory factors of PD-L1 can be potential targets for immunotherapy and increase strategies of immunotherapy in combination.

Response to immune checkpoint blockade improved in pre-clinical model of breast cancer after bariatric surgery

Bariatric surgery is a sustainable weight loss approach, including vertical sleeve gastrectomy (VSG). Obesity exacerbates tumor growth, while diet-induced weight loss impairs progression. It remains unknown how bariatric surgery-induced weight loss impacts cancer progression or alters response to therapy. Using a pre-clinical model of obesity followed by VSG or diet-induced weight loss, breast cancer progression and immune checkpoint blockade therapy were investigated. Weight loss by VSG or weight-matched dietary intervention before tumor engraftment protected against obesity-exacerbated tumor progression. However, VSG was not as effective as diet in reducing tumor burden despite achieving similar weight and adiposity loss. Leptin did not associate with changes in tumor burden; however, circulating IL-6 was elevated in VSG mice. Uniquely, VSG tumors displayed elevated inflammation and immune checkpoint ligand PD-L1+ myeloid and non-immune cells. VSG tumors also had reduced T lymphocytes and markers of cytolysis, suggesting an ineffective anti-tumor microenvironment which prompted investigation of immune checkpoint blockade. While obese mice were resistant to immune checkpoint blockade, anti-PD-L1 potently impaired tumor progression after VSG through improved anti-tumor immunity. Thus, in formerly obese mice, surgical weight loss followed by immunotherapy reduced breast cancer burden. Finally, we compared transcriptomic changes in adipose tissue after bariatric surgery from patients and mouse models. A conserved bariatric surgery-associated weight loss signature (BSAS) was identified which significantly associated with decreased tumor volume. Findings demonstrate conserved impacts of obesity and bariatric surgery-induced weight loss pathways associated with breast cancer progression.

As the number of people classified as obese rises globally, so do obesity-related health risks. Studies show that people diagnosed with obesity have inflammation that contributes to tumor growth and their immune system is worse at detecting cancer cells. But weight loss is not currently used as a strategy for preventing or treating cancer.

Surgical procedures for weight loss, also known as ‘bariatric surgeries’, are becoming increasingly popular. Recent studies have shown that individuals who lose weight after these treatments have a reduced risk of developing tumors. But how bariatric surgery directly impacts cancer progression has not been well studied: does it slow tumor growth or boost the anti-tumor immune response?

To answer these questions, Sipe et al. compared breast tumor growth in groups of laboratory mice that were obese due to being fed a high fat diet. The first group of mice lost weight after undergoing a bariatric surgery in which part of their stomach was removed. The second lost the same amount of weight but after receiving a restricted diet, and the third underwent a fake surgery and did not lose any weight. The experiments found that surgical weight loss cuts breast cancer tumor growth in half compared with obese mice. But mice who lost the same amount of weight through dietary restrictions had even less tumor growth than surgically treated mice.

The surgically treated mice who lost weight had more inflammation than mice in the two other groups, and had increased amounts of proteins and cells that block the immune response to tumors. Giving the surgically treated mice a drug that enhances the immune system’s ability to detect and destroy cancer cells reduced inflammation and helped shrink the mice’s tumors. Finally, Sipe et al. identified 54 genes which were turned on or off after bariatric surgery in both mice and humans, 11 of which were linked with tumor size.

These findings provide crucial new information about how bariatric surgery can impact cancer progression. Future studies could potentially use the conserved genes identified by Sipe et al. to develop new ways to stimulate the anti-cancer benefits of weight loss without surgery.

Immune-checkpoint inhibitors: long-term implications of toxicity

The development of immune-checkpoint inhibitors (ICIs) has heralded a new era in cancer treatment, enabling the possibility of long-term survival in patients with metastatic disease, and providing new therapeutic indications in earlier-stage settings. As such, characterizing the long-term implications of receiving ICIs has grown in importance. An abundance of evidence exists describing the acute clinical toxicities of these agents, although chronic effects have not been as well catalogued. Nonetheless, emerging evidence indicates that persistent toxicities might be more common than initially suggested. While generally low-grade, these chronic sequelae can affect the endocrine, rheumatological, pulmonary, neurological and other organ systems. Fatal toxicities also comprise a diverse set of clinical manifestations and can occur in 0.4-1.2% of patients. This risk is a particularly relevant consideration in light of the possibility of long-term survival. Finally, the effects of immune-checkpoint blockade on a diverse range of immune processes, including atherosclerosis, heart failure, neuroinflammation, obesity and hypertension, have not been characterized but remain an important area of research with potential relevance to cancer survivors. In this Review, we describe the current evidence for chronic immune toxicities and the long-term implications of these effects for patients receiving ICIs.

Innate PD-L1 limits T cell-mediated adipose tissue inflammation and ameliorates diet-induced obesity

Obesity has become a major health problem in the industrialized world. Immune regulation plays an important role in adipose tissue homeostasis; however, the initial events that shift the balance from a noninflammatory homeostatic environment toward inflammation leading to obesity are poorly understood. Here, we report a role for the costimulatory molecule programmed death-ligand 1 (PD-L1) in the limitation of diet-induced obesity. Functional ablation of PD-L1 on dendritic cells (DCs) using conditional knockout mice increased weight gain and metabolic syndrome during diet-induced obesity, whereas PD-L1 expression on type 2 innate lymphoid cells (ILC2s), T cells, and macrophages was dispensable for obesity control. Using in vitro cocultures, DCs interacted with T cells and ILC2s via the PD-L1:PD-1 axis to inhibit T helper type 1 proliferation and promote type 2 polarization, respectively. A role for PD-L1 in adipose tissue regulation was also shown in humans, with a positive correlation between PD-L1 expression in visceral fat of people with obesity and elevated body weight. Thus, we define a mechanism of adipose tissue homeostasis controlled by the expression of PD-L1 by DCs, which may be a clinically relevant finding with regard to immune-related adverse events during immune checkpoint inhibitor therapy.

The Interplay between Tumour Microenvironment Components in Malignant Melanoma

Malignant melanoma has shown an increasing incidence during the last two decades, exhibiting a large spectrum of locations and clinicopathological characteristics. Although current histopathological, biochemical, immunohistochemical, and molecular methods provide a deep insight into its biological behaviour and outcome, melanoma is still an unpredictable disease, with poor outcome. This review of the literature is aimed at updating the knowledge regarding melanoma’s clinicopathological and molecular hallmarks, including its heterogeneity and plasticity, involving cancer stem cells population. A special focus is given on the interplay between different cellular components and their secretion products in melanoma, considering its contribution to tumour progression, invasion, metastasis, recurrences, and resistance to classical therapy. Furthermore, the influences of the specific tumour microenvironment or “inflammasome”, its association with adipose tissue products, including the release of “extracellular vesicles”, and distinct microbiota are currently studied, considering their influences on diagnosis and prognosis. An insight into melanoma’s particular features may reveal new molecular pathways which may be exploited in order to develop innovative therapeutic approaches or tailored therapy.

The ambiguous role of obesity in oncology by promoting cancer but boosting antitumor immunotherapy

Obesity is nowadays considered a pandemic which prevalence's has been steadily increasingly in western countries. It is a dynamic, complex, and multifactorial disease which propitiates the development of several metabolic and cardiovascular diseases, as well as cancer. Excessive adipose tissue has been causally related to cancer progression and is a preventable risk factor for overall and cancer-specific survival, associated with poor prognosis in cancer patients. The onset of obesity features a state of chronic low-grade inflammation and secretion of a diversity of adipocyte-derived molecules (adipokines, cytokines, hormones), responsible for altering the metabolic, inflammatory, and immune landscape. The crosstalk between adipocytes and tumor cells fuels the tumor microenvironment with pro-inflammatory factors, promoting tissue injury, mutagenesis, invasion, and metastasis. Although classically established as a risk factor for cancer and treatment toxicity, recent evidence suggests mild obesity is related to better outcomes, with obese cancer patients showing better responses to treatment when compared to lean cancer patients. This phenomenon is termed obesity paradox and has been reported in different types and stages of cancer. The mechanisms underlying this paradoxical relationship between obesity and cancer are still not fully described but point to systemic alterations in metabolic fitness and modulation of the tumor microenvironment by obesity-associated molecules. Obesity impacts the response to cancer treatments, such as chemotherapy and immunotherapy, and has been reported as having a positive association with immune checkpoint therapy. In this review, we discuss obesity's association to inflammation and cancer, also highlighting potential physiological and biological mechanisms underlying this association, hoping to clarify the existence and impact of obesity paradox in cancer development and treatment.

Fluoxetine ameliorates high-fat diet-induced metabolic abnormalities partially via reduced adipose triglyceride lipase-mediated adipocyte lipolysis

Patients with type 2 diabetes mellitus have more risk to develop depression. Fluoxetine (FLX), a selective serotonin reuptake inhibitor (SSRI), is drug for mood and anxiety disorders. Previous studies showed that FLX could induce weight loss in non-depressed clinically overweight individuals. Although the anti-appetite effect of FLX is well-documented, its potential effects on metabolic abnormalities have not been investigated. In this study, we want to investigate whether FLX could be a therapeutic drug against high fat diet (HFD)-induced metabolic disorder. We generated metabolic disorders and depressed mouse model by feeding HFD for 12 weeks at the age of 8 weeks. Then, mice were intraperitoneally injected once daily with FLX (10 mg/kg or 20 mg/kg) for four weeks. Our results showed that FLX alleviated the HFD-induced metabolic dysfunctions and depressive phenotypes in mice. FLX improved systemic glucose homeostasis, at least in part, by improving visceral white adipose tissue (vWAT) insulin signaling. Moreover, FLX reduced circulating plasma leptin level, and decreased the expression of adipose triglyceride lipase (ATGL) and peroxisome proliferator-activated receptor gamma (PPARγ) in vWAT. Our data revealed that FLX also reduced the triglyceride (TG) accumulation in vWAT. Therefore, these findings suggest that FLX exhibits significant potential on comorbidity of metabolic disorder and depression in mice.

Immune checkpoint blockade reprograms systemic immune landscape and tumor microenvironment in obesity-associated breast cancer

Immune checkpoint blockade (ICB) has improved outcomes in some cancers. A major limitation of ICB is that most patients fail to respond, which is partly attributable to immunosuppression. Obesity appears to improve immune checkpoint therapies in some cancers, but impacts on breast cancer (BC) remain unknown. In lean and obese mice, tumor progression and immune reprogramming were quantified in BC tumors treated with anti-programmed death-1 (PD-1) or control. Obesity augments tumor incidence and progression. Anti-PD-1 induces regression in lean mice and potently abrogates progression in obese mice. BC primes systemic immunity to be highly responsive to obesity, leading to greater immunosuppression, which may explain greater anti-PD-1 efficacy. Anti-PD-1 significantly reinvigorates antitumor immunity despite persistent obesity. Laminin subunit beta-2 (Lamb2), downregulated by anti-PD-1, significantly predicts patient survival. Lastly, a microbial signature associated with anti-PD-1 efficacy is identified. Thus, anti-PD-1 is highly efficacious in obese mice by reinvigorating durable antitumor immunity. VIDEO ABSTRACT.

Dermal Drivers of Injury-Induced Inflammation: Contribution of Adipocytes and Fibroblasts

Irregular inflammatory responses are a major contributor to tissue dysfunction and inefficient repair. Skin has proven to be a powerful model to study mechanisms that regulate inflammation. In particular, skin wound healing is dependent on a rapid, robust immune response and subsequent dampening of inflammatory signaling. While injury-induced inflammation has historically been attributed to keratinocytes and immune cells, a vast body of evidence supports the ability of non-immune cells to coordinate inflammation in numerous tissues and diseases. In this review, we concentrate on the active participation of tissue-resident adipocytes and fibroblasts in pro-inflammatory signaling after injury, and how altered cellular communication from these cells can contribute to irregular inflammation associated with aberrant wound healing. Furthering our understanding of how tissue-resident mesenchymal cells contribute to inflammation will likely reveal new targets that can be manipulated to regulate inflammation and repair.

Stromal Cells Present in the Melanoma Niche Affect Tumor Invasiveness and Its Resistance to Therapy

Malignant melanoma is a highly metastatic type of cancer, which arises frequently from transformed pigment cells and melanocytes as a result of long-term UV radiation exposure. In recent years, the incidence of newly diagnosed melanoma patients reached 5% of all cancer cases. Despite the development of novel targeted therapies directed against melanoma-specific markers, patients' response to treatment is often weak or short-term due to a rapid acquisition of drug resistance. Among the factors affecting therapy effectiveness, elements of the tumor microenvironment play a major role. Melanoma niche encompasses adjacent cells, such as keratinocytes, cancer-associated fibroblasts (CAFs), adipocytes, and immune cells, as well as components of the extracellular matrix and tumor-specific physicochemical properties. In this review, we summarize the current knowledge concerning the influence of cancer-associated cells (keratinocytes, CAFs, adipocytes) on the process of melanomagenesis, tumor progression, invasiveness, and the emergence of drug resistance in melanoma. We also address how melanoma can alter the differentiation and activation status of cells present in the tumor microenvironment. Understanding these complex interactions between malignant and cancer-associated cells could improve the development of effective antitumor therapeutic strategies.