Severe cachexia in mice inoculated with interferon-gamma-producing tumor cells

IL-6 promotes tumor growth through immune evasion but is dispensable for cachexia

Various cytokines have been implicated in cancer cachexia. One such cytokine is IL-6, deemed as a key cachectic factor in mice inoculated with colon carcinoma 26 (C26) cells, a widely used cancer cachexia model. Here we tested the causal role of IL-6 in cancer cachexia by knocking out the IL-6 gene in C26 cells. We found that the growth of IL-6 KO tumors was dramatically delayed. More strikingly, while IL-6 KO tumors eventually reached the similar size as wild-type tumors, cachexia still took place, despite no elevation in circulating IL-6. In addition, the knockout of leukemia inhibitory factor (LIF), another IL-6 family cytokine proposed as a cachectic factor in the model, also affected tumor growth but not cachexia. We further showed an increase in the infiltration of immune cell population in the IL-6 KO tumors compared with wild-type controls and the defective IL-6 KO tumor growth was rescued in immunodeficient mice while cachexia was not. Thus, IL-6 promotes tumor growth by facilitating immune evasion but is dispensable for cachexia.

Cancer cachexia: biomarkers and the influence of age

Cancer cachexia (Ccx) is a complex metabolic condition characterized by pronounced muscle and fat wasting, systemic inflammation, weakness and fatigue. Up to 30% of cancer patients succumb directly to Ccx, yet therapies that effectively address this perturbed metabolic state are rare. In recent decades, several characteristics of Ccx have been established in mice and humans, of which we here highlight adipose tissue dysfunction, muscle wasting and systemic inflammation, as they are directly linked to biomarker discovery. To counteract cachexia pathogenesis as early as possible and mitigate its detrimental impact on anti-cancer treatments, identification and validation of clinically endorsed biomarkers assume paramount importance. Ageing was recently shown to affect both the validity of Ccx biomarkers and Ccx development, but the underlying mechanisms are still unknown. Thus, unravelling the intricate interplay between ageing and Ccx can help to counteract Ccx pathogenesis and tailor diagnostic and treatment strategies to individual needs.

Growth differentiation factor-15 is an IFN-γ regulated mediator of infection-induced weight loss and the hepatic FGF21 response

Infections are often accompanied by weight loss caused by alterations in host behavior and metabolism, also known as sickness behaviors. Recent studies have revealed that sickness behaviors can either promote or impede survival during infections depending on factors such as the type of infectious pathogen. Nevertheless, we have an incomplete understanding of the underlying mechanisms of sickness behaviors. Furthermore, although the host immune responses to infections have long been known to contribute to the induction of sickness behaviors, recent studies have identified emerging cytokines that are also key regulators of host metabolism during infection and inflammation, such as growth differentiation factor 15 (GDF-15). GDF-15 is a distant member of the TGF-β superfamily that causes weight loss by suppressing appetite and food consumption and causing emesis. These effects require activation of neurons that express the only known GDF-15 receptor, the GFRAL receptor. GDF-15 also functions in the periphery including the induction of ketogenesis and immunoregulation. Nevertheless, the functions and regulation of GDF-15 during live infections is not yet known. Murine infection with avirulent Toxoplasma gondii is an established model to understand infection-induced weight loss. Past studies have determined that acute T. gondii infection causes weight loss due to diminished food consumption and increased energy expenditure through unknown mechanisms. Additionally, our lab previously demonstrated that T. gondii causes upregulation in serum GDF-15 in an IFN-γ-dependent manner during the post-acute phase of the infection. In this study, we interrogated the in-vivo functions and immune regulation of GDF-15 during Toxoplasma gondii infection. First, we found that in wild-type mice, acute T. gondii infection caused a significant weight loss that is preceded by elevation of serum levels of IFN-γ and GDF-15. To determine whether IFN-γ regulates GDF-15, we neutralized IFN-γ on days 5 and 6 and measured GDF-15 on day 7 and found that serum but not tissue levels of GDF-15 decreased after IFN-γ neutralization. Additionally, exogenous IFN-γ was sufficient to elevate serum GDF-15 in the absence of infection. Next, we compared the outcomes of T. gondii infection between WT and Gdf15-/- mice. We observed that the weight trajectories were declining in WT mice while they were increasing in Gdf15-/-mice during the acute phase of the infection. This difference in trajectories extended throughout the chronic infection resulting to an overall weight loss relative to initial weights in WT mice but not Gdf15-/-mice. Then, we determined that GDF-15 is not essential for survival and immunoregulation during T. gondii infection. We also demonstrated that GDF-15 is required for the induction of FGF21, stress-induced cytokine with prominent roles in regulating host metabolism. Finally, we discovered a cytokine cascade IFN-γ-GDF-15-FGF21 that is likely involved in the regulation of host metabolism. Overall, our study provides evidence that IFN-γ contributes to the regulation of host metabolism during infection by inducing GDF-15 and FGF21. GDF-15 orchestrates changes in host metabolism that supports the host immune response in clearing the infection. These physiological alterations induce FGF21, which in turn, orchestrates the adaptive responses to the effects of GDF-15, which can be detrimental when protracted.

Deliberation on debilitating condition of cancer cachexia: Skeletal muscle wasting

BACKGROUND

Cancer cachexia is a debilitating syndrome associated with marked body loss because of muscular atrophy and fat loss. There are several mechanisms contributing to the pathogenesis of cachexia. The presence of the tumor releases cytokines from inflammatory and immune cells, which play a significant role in activating and deactivating certain pathways associated with protein, carbohydrate, and lipid metabolism. This review focuses on various cascades involving an imbalance between protein synthesis and degradation in the skeletal muscles.

OBJECTIVES

This study aimed to elucidate the mechanisms involved in skeletal muscle wasting phenomenon over the last few years.

METHODS

This article briefly overviews different pathways responsible for muscle atrophy in cancer cachexia. Studies published up to April 2023 were included. Important findings and study contributions were chosen and compiled using several databases including PubMed, Google Scholar, Science Direct, and ClinicalTrials.gov using relevant keywords.

RESULTS

Cancer cachexia is a complex disease involving multiple factors resulting in atrophy of skeletal muscles. Systemic inflammation, altered energy balance and carbohydrate metabolism, altered lipid and protein metabolism, and adipose tissue browning are some of the major culprits in cancer cachexia. Increased protein degradation and decreased protein synthesis lead to muscle atrophy. Changes in signaling pathway like ubiquitin-proteasome, autophagy, mTOR, AMPK, and IGF-1 also lead to muscle wasting. Physical exercise, nutritional supplementation, steroids, myostatin inhibitors, and interventions targeting on inflammation have been investigated to treat cancer cachexia. Some therapy showed positive results in preclinical and clinical settings, although more research on the efficacy and safety of the treatment should be done.

CONCLUSION

Muscle atrophy in cancer cachexia is the result of multiple complex mechanisms; as a result, a lot more research has been done to describe the pathophysiology of the disease. Targeted therapy and multimodal interventions can improve clinical outcomes for patients.

IL-6 is dispensable for causing cachexia in the colon carcinoma 26 model

Various cytokines have been implicated in cancer cachexia. One such cytokine is IL-6, which has been deemed a key cachectic factor in mice inoculated with the colon carcinoma 26 (C26) cells, one of the most widely used models of cancer cachexia. Here to test the causal role of IL-6 in cancer cachexia, we used CRISPR/Cas9 editing to knock out IL-6 in C26 cells. We found that growth of IL-6 KO C26 tumors was dramatically delayed. Most strikingly, while IL-6 KO tumors eventually reached the similar size as wild-type tumors, cachexia still took place, despite no elevation in circulating IL-6. We further showed an increase of immune cell populations in IL-6 KO tumors and the defective IL-6 KO tumor growth was rescued in immunodeficient mice. Thus, our results invalidated IL-6 as a necessary factor for causing cachexia in the C26 model and revealed instead its important role in regulating tumor growth via immune suppression.

Cachexia: A systemic consequence of progressive, unresolved disease

Cachexia, a systemic wasting condition, is considered a late consequence of diseases, including cancer, organ failure, or infections, and contributes to significant morbidity and mortality. The induction process and mechanistic progression of cachexia are incompletely understood. Refocusing academic efforts away from advanced cachexia to the etiology of cachexia may enable discoveries of new therapeutic approaches. Here, we review drivers, mechanisms, organismal predispositions, evidence for multi-organ interaction, model systems, clinical research, trials, and care provision from early onset to late cachexia. Evidence is emerging that distinct inflammatory, metabolic, and neuro-modulatory drivers can initiate processes that ultimately converge on advanced cachexia.

Anti-inflammatory actions of Pentosan polysulfate sodium in a mouse model of influenza virus A/PR8/34-induced pulmonary inflammation

Introduction

There is an unmet medical need for effective anti-inflammatory agents for the treatment of acute and post-acute lung inflammation caused by respiratory viruses. The semi-synthetic polysaccharide, Pentosan polysulfate sodium (PPS), an inhibitor of NF-kB activation, was investigated for its systemic and local anti-inflammatory effects in a mouse model of influenza virus A/PR8/1934 (PR8 strain) mediated infection.

Methods

Immunocompetent C57BL/6J mice were infected intranasally with a sublethal dose of PR8 and treated subcutaneously with 3 or 6 mg/kg PPS or vehicle. Disease was monitored and tissues were collected at the acute (8 days post-infection; dpi) or post-acute (21 dpi) phase of disease to assess the effect of PPS on PR8-induced pathology.

Results

In the acute phase of PR8 infection, PPS treatment was associated with a reduction in weight loss and improvement in oxygen saturation when compared to vehicle-treated mice. Associated with these clinical improvements, PPS treatment showed a significant retention in the numbers of protective SiglecF+ resident alveolar macrophages, despite uneventful changes in pulmonary leukocyte infiltrates assessed by flow cytometry. PPS treatment in PR8- infected mice showed significant reductions systemically but not locally of the inflammatory molecules, IL-6, IFN-g, TNF-a, IL-12p70 and CCL2. In the post-acute phase of infection, PPS demonstrated a reduction in the pulmonary fibrotic biomarkers, sICAM-1 and complement factor C5b9.

Discussion

The systemic and local anti-inflammatory actions of PPS may regulate acute and post-acute pulmonary inflammation and tissue remodeling mediated by PR8 infection, which warrants further investigation.

Pathological features of tissues and cell populations during cancer cachexia

Cancers remain among the most devastating diseases in the human population in spite of considerable advances in limiting their impact on lifespan and healthspan. The multifactorial nature of cancers, as well as the number of tissues and organs that are affected, have exposed a considerable diversity in mechanistic features that are reflected in the wide array of therapeutic strategies that have been adopted. Cachexia is manifested in a number of diseases ranging from cancers to diabetes and ageing. In the context of cancers, a majority of patients experience cachexia and succumb to death due to the indirect effects of tumorigenesis that drain the energy reserves of different organs. Considerable information is available on the pathophysiological features of cancer cachexia, however limited knowledge has been acquired on the resident stem cell populations, and their function in the context of these diseases. Here we review current knowledge on cancer cachexia and focus on how tissues and their resident stem and progenitor cell populations are individually affected.

Review of the endocrine organ-like tumor hypothesis of cancer cachexia in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is one of the most fatal types of solid tumors, associated with a high prevalence of cachexia (~80%). PDAC-derived cachexia (PDAC-CC) is a systemic disease involving the complex interplay between the tumor and multiple organs. The endocrine organ-like tumor (EOLT) hypothesis may explain the systemic crosstalk underlying the deleterious homeostatic shifts that occur in PDAC-CC. Several studies have reported a markedly heterogeneous collection of cachectic mediators, signaling mechanisms, and metabolic pathways, including exocrine pancreatic insufficiency, hormonal disturbance, pro-inflammatory cytokine storm, digestive and tumor-derived factors, and PDAC progression. The complexities of PDAC-CC necessitate a careful review of recent literature summarizing cachectic mediators, corresponding metabolic functions, and the collateral impacts on wasting organs. The EOLT hypothesis suggests that metabolites, genetic instability, and epigenetic changes (microRNAs) are involved in cachexia development. Both tumors and host tissues can secrete multiple cachectic factors (beyond only inflammatory mediators). Some regulatory molecules, metabolites, and microRNAs are tissue-specific, resulting in insufficient energy production to support tumor/cachexia development. Due to these complexities, changes in a single factor can trigger bi-directional feedback circuits that exacerbate PDAC and result in the development of irreversible cachexia. We provide an integrated review based on 267 papers and 20 clinical trials from PubMed and ClinicalTrials.gov database proposed under the EOLT hypothesis that may provide a fundamental understanding of cachexia development and response to current treatments.

Development of a Therapeutic Peptide for Cachexia Suggests a Platform Approach for Drug-like Peptides

During the development of a melanocortin (MC) peptide drug to treat the condition of cachexia (a hypermetabolic state producing lean body mass wasting), we were confronted with the need for peptide transport across the blood-brain barrier (BBB): the MC-4 receptors (MC4Rs) for metabolic rate control are located in the hypothalamus, i.e., behind the BBB. Using the term "peptides with BBB transport", we screened the medical literature like a peptide library. This revealed numerous "hits"-peptides with BBB transport and/or oral activity. We noted several features common to most peptides in this class, including a dipeptide sequence of nonpolar residues, primary structure cyclization (whole or partial), and a Pro-aromatic motif usually within the cyclized region. Based on this, we designed an MC4R antagonist peptide, TCMCB07, that successfully treated many forms of cachexia. As part of our pharmacokinetic characterization of TCMCB07, we discovered that hepatobiliary extraction from blood accounted for a majority of the circulating peptide's excretion. Further screening of the literature revealed that TCMCB07 is a member of a long-forgotten peptide class, showing active transport by a multi-specific bile salt carrier. Bile salt transport peptides have predictable pharmacokinetics, including BBB transport, but rapid hepatic clearance inhibited their development as drugs. TCMCB07 shares the general characteristics of the bile salt peptide class but with a much longer half-life of hours, not minutes. A change in its C-terminal amino acid sequence slows hepatic clearance. This modification is transferable to other peptides in this class, suggesting a platform approach for producing drug-like peptides.

Metabolic Reprogramming in Adipose Tissue During Cancer Cachexia

Cancer cachexia is a disorder of energy balance characterized by the wasting of adipose tissue and skeletal muscle resulting in severe weight loss with profound influence on morbidity and mortality. Treatment options for cancer cachexia are still limited. This multifactorial syndrome is associated with changes in several metabolic pathways in adipose tissue which is affected early in the course of cachexia. Adipose depots are involved in energy storage and consumption as well as endocrine functions. In this mini review, we discuss the metabolic reprogramming in all three types of adipose tissues – white, brown, and beige – under the influence of the tumor macro-environment. Alterations in adipose tissue lipolysis, lipogenesis, inflammation and adaptive thermogenesis of beige/brown adipocytes are highlighted. Energy-wasting circuits in adipose tissue impacts whole-body metabolism and particularly skeletal muscle. Targeting of key molecular players involved in the metabolic reprogramming may aid in the development of new treatment strategies for cancer cachexia.

A systematic review examining the relationship between cytokines and cachexia in incurable cancer

Cancer cachexia is an unmet clinical need that affects more than 50% of patients with cancer. The systemic inflammatory response, which is mediated by a network of cytokines, has an established role in the genesis and maintenance of cancer as well as in cachexia; yet, the specific role of the cytokine milieu in cachexia requires elucidation. This systematic review aims to examine the relationship between cytokines and the cachexia syndrome in patients with incurable cancer. The databases MEDLINE, EMBASE, CINAHL, CENTRAL, PsycINFO, and Web of Science were searched for studies published between 01/01/2004 and 06/01/2020. Included studies measured cytokines and their relationship with cachexia and related symptoms/signs in adults with incurable cancer. After title screening (n = 5202), the abstracts (n = 1264) and the full-text studies (n = 322) were reviewed independently by two authors. The quality assessment of the selected papers was conducted using the modified Downs and Black checklist. Overall, 1277 patients with incurable cancer and 155 healthy controls were analysed in the 17 eligible studies. The mean age of the patients was 64 ± 15 (mean ± standard deviation). Only 34% of included participants were female. The included studies were assessed as moderate-quality to high-quality evidence (mean quality score: 7.8; range: 5-10). A total of 31 cytokines were examined in this review, of which interleukin-6 (IL-6, 14 studies) and tumour necrosis factor-α (TNF-α, 12 studies) were the most common. The definitions of cachexia and the weight-loss thresholds were highly variable across studies. Although the data could not be meta-analysed due to the high degree of methodological heterogeneity, the findings were discussed in a systematic manner. IL-6, TNF-α, and IL-8 were greater in cachectic patients compared with healthy individuals. Also, IL-6 levels were higher in cachectic participants as opposed to non-cachectic patients. Leptin, interferon-γ, IL-1β, IL-10, adiponectin, and ghrelin did not demonstrate any significant difference between groups when individuals with cancer cachexia were compared against non-cachectic patients or healthy participants. These findings suggest that a network of cytokines, commonly IL-6, TNF-α, and IL-8, are associated with the development of cachexia. Yet, this relationship is not proven to be causative and future studies should opt for longitudinal designs with consistent methodological approaches, as well as adequate techniques for analysing and reporting the results.

The interplay of immunology and cachexia in infection and cancer

Diverse inflammatory diseases, infections and malignancies are associated with wasting syndromes. In many of these conditions, the standards for diagnosis and treatment are lacking due to our limited understanding of the causative molecular mechanisms. Here, we discuss the complex immunological context of cachexia, a systemic catabolic syndrome that depletes both fat and muscle mass with profound consequences for patient prognosis. We highlight the main cytokine and immune cell-driven pathways that have been linked to weight loss and tissue wasting in the context of cancer-associated and infection-associated cachexia. Moreover, we discuss the potential immunometabolic consequences of cachexia on the basis of newly identified pathways and explore the multilayered area of immunometabolic crosstalk both upstream and downstream of tissue catabolism. Collectively, this Review highlights the intricate relationship of the immune system with cachexia in the context of malignant and infectious diseases.

Cancer-A Major Cardiac Comorbidity With Implications on Cardiovascular Metabolism

Cardiovascular diseases have multifactorial causes. Classical cardiovascular risk factors, such as arterial hypertension, smoking, hyperlipidemia, and diabetes associate with the development of vascular stenoses and coronary heart disease. Further comorbidities and its impact on cardiovascular metabolism have gotten more attention recently. Thus, also cancer biology may affect the heart, apart from cardiotoxic side effects of chemotherapies. Cancer is a systemic disease which primarily leads to metabolic alterations within the tumor. An emerging number of preclinical and clinical studies focuses on the interaction between cancer and a maladaptive crosstalk to the heart. Cachexia and sarcopenia can have dramatic consequences for many organ functions, including cardiac wasting and heart failure. These complications significantly increase mortality and morbidity of heart failure and cancer patients. There are concurrent metabolic changes in fatty acid oxidation (FAO) and glucose utilization in heart failure as well as in cancer, involving central molecular regulators, such as PGC-1α. Further, specific inflammatory cytokines (IL-1β, IL-6, TNF-α, INF-β), non-inflammatory cytokines (myostatin, SerpinA3, Ataxin-10) and circulating metabolites (D2-HG) may mediate a direct and maladaptive crosstalk of both diseases. Additionally, cancer therapies, such as anthracyclines and angiogenesis inhibitors target common metabolic mechanisms in cardiomyocytes and malignant cells. This review focuses on cardiovascular, cancerous, and cancer therapy-associated alterations on the systemic and cardiac metabolic state.

JAK1 Inhibition Blocks Lethal Immune Hypersensitivity in a Mouse Model of Down Syndrome

Individuals with Down syndrome (DS; trisomy 21) display hyperactivation of interferon (IFN) signaling and chronic inflammation, which could potentially be explained by the extra copy of four IFN receptor (IFNR) genes encoded on chromosome 21. However, the clinical effects of IFN hyperactivity in DS remain undefined. Here, we report that a commonly used mouse model of DS overexpresses IFNR genes and shows hypersensitivity to IFN ligands in diverse immune cell types. When treated repeatedly with a TLR3 agonist to induce chronic inflammation, these animals overexpress key IFN-stimulated genes, induce cytokine production, exhibit liver pathology, and undergo rapid weight loss. Importantly, the lethal immune hypersensitivity and cytokine production and the ensuing pathology are ameliorated by JAK1 inhibition. These results indicate that individuals with DS may experience harmful hyperinflammation upon IFN-inducing immune stimuli, as observed during severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, pointing to JAK1 inhibition as a strategy to restore immune homeostasis in DS.

Inflammation and Skeletal Muscle Wasting During Cachexia

Cachexia is the involuntary loss of muscle and adipose tissue that strongly affects mortality and treatment efficacy in patients with cancer or chronic inflammatory disease. Currently, no specific treatments or interventions are available for patients developing this disorder. Given the well-documented involvement of pro-inflammatory cytokines in muscle and fat metabolism in physiological responses and in the pathophysiology of chronic inflammatory disease and cancer, considerable interest has revolved around their role in mediating cachexia. This has been supported by association studies that report increased levels of pro-inflammatory cytokines such as tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6) in some, but not all, cancers and in chronic inflammatory diseases such as chronic obstructive pulmonary disease (COPD) and rheumatoid arthritis (RA). In addition, preclinical studies including animal disease models have provided a substantial body of evidence implicating a causal contribution of systemic inflammation to cachexia. The presence of inflammatory cytokines can affect skeletal muscle through several direct mechanisms, relying on activation of the corresponding receptor expressed by muscle, and resulting in inhibition of muscle protein synthesis (MPS), elevation of catabolic activity through the ubiquitin-proteasomal system (UPS) and autophagy, and impairment of myogenesis. Additionally, systemic inflammatory mediators indirectly contribute to muscle wasting through dysregulation of tissue and organ systems, including GCs via the hypothalamus-pituitary-adrenal (HPA) axis, the digestive system leading to anorexia-cachexia, and alterations in liver and adipocyte behavior, which subsequently impact on muscle. Finally, myokines secreted by skeletal muscle itself in response to inflammation have been implicated as autocrine and endocrine mediators of cachexia, as well as potential modulators of this debilitating condition. While inflammation has been shown to play a pivotal role in cachexia development, further understanding how these cytokines contribute to disease progression is required to reveal biomarkers or diagnostic tools to help identify at risk patients, or enable the design of targeted therapies to prevent or delay the progression of cachexia.

Cachexia, a Systemic Disease beyond Muscle Atrophy

Cachexia is a complication of dismal prognosis, which often represents the last step of several chronic diseases. For this reason, the comprehension of the molecular drivers of such a condition is crucial for the development of management approaches. Importantly, cachexia is a syndrome affecting various organs, which often results in systemic complications. To date, the majority of the research on cachexia has been focused on skeletal muscle, muscle atrophy being a pivotal cause of weight loss and the major feature associated with the steep reduction in quality of life. Nevertheless, defining the impact of cachexia on other organs is essential to properly comprehend the complexity of such a condition and potentially develop novel therapeutic approaches.

Role of acute exacerbations in skeletal muscle impairment in COPD

Introduction: Muscle impairments are prevalent in COPD and have adverse clinical implications in terms of physical performance capacity, disease burden, quality of life and even mortality. During acute exacerbations of COPD (AECOPDs) the respiratory symptoms worsen and this might also apply to the muscle impairments. Areas covered: This report includes a review of both clinical and pre-clinical peer-reviewed literature of the past 20 years found in PubMed providing a comprehensive view on the role of AECOPD in muscle dysfunction in COPD, the putative underlying mechanisms and the treatment perspectives. Expert opinion: The contribution of AECOPD and its recurrent nature to muscle impairment in COPD cannot be ignored and can be attributed to the acutely intensifying and converging disease-related drivers of muscle deterioration, in particular disuse, systemic inflammation and corticosteroid treatment. The search for novel treatment options should focus on the AECOPD-enhanced drivers of muscle dysfunction as well as on the underlying, mainly catabolic, mechanisms. Considering the impact of AECOPD on muscle function, and that of muscle impairment on the recurrence of exacerbations, counteracting muscle deterioration in AECOPD provides an unprecedented therapeutic opportunity.

The Etiology and Impact of Muscle Wasting in Metastatic Cancer

Metastasis arises when cancer cells disseminate from their site of origin and invade distant organs. While cancer cells rarely colonize muscle, they often induce a debilitating muscle-wasting condition known as cachexia that compromises feeding, breathing, and cardiac function in metastatic cancer patients. In fact, nearly 80% of metastatic cancer patients experience a spectrum of muscle-wasting states, which deteriorates the quality of life and overall survival of cancer patients. Muscle wasting in cancer results from increased muscle catabolism induced by circulating tumor factors and a systemic metabolic dysfunction. In addition, muscle loss can be exacerbated by the exposure to antineoplastic therapies and the process of aging. With no approved therapies to alleviate cachexia, muscle health, therefore, becomes a key determinant of prognosis, treatment response, and survival in metastatic cancer patients. This review will discuss the current understanding of cancer-associated cachexia and highlight promising therapeutic strategies to treat muscle wasting in the context of metastatic cancers.

Management of Cancer Cachexia: Attempting to Develop New Pharmacological Agents for New Effective Therapeutic Options

Cancer cachexia (CC) is a multifactorial syndrome characterized by systemic inflammation, uncontrolled weight loss and dramatic metabolic alterations. This includes myofibrillar protein breakdown, increased lipolysis, insulin resistance, elevated energy expediture, and reduced food intake, hence impairing the patient's response to anti-cancer therapies and quality of life. While a decade ago the syndrome was considered incurable, over the most recent years much efforts have been put into the study of such disease, leading to the development of potential therapeutic strategies. Several important improvements have been reached in the management of CC from both the diagnostic-prognostic and the pharmacological viewpoint. However, given the heterogeneity of the disease, it is impossible to rely only on single variables to properly treat patients presenting this metabolic syndrome. Moreover, the cachexia symptoms are strictly dependent on the type of tumor, stage and the specific patient's response to cancer therapy. Thus, the attempt to translate experimentally effective therapies into the clinical practice results in a great challenge. For this reason, it is of crucial importance to further improve our understanding on the interplay of molecular mechanisms implicated in the onset and progression of CC, giving the opportunity to develop new effective, safe pharmacological treatments. In this review we outline the recent knowledge regarding cachexia mediators and pathways involved in skeletal muscle (SM) and adipose tissue (AT) loss, mainly from the experimental cachexia standpoint, then retracing the unimodal treatment options that have been developed to the present day.

Neutrophils Dampen Adaptive Immunity in Brucellosis

Brucella organisms are intracellular stealth pathogens of animals and humans. The bacteria overcome the assault of innate immunity at early stages of an infection.

Brucella organisms are intracellular stealth pathogens of animals and humans. The bacteria overcome the assault of innate immunity at early stages of an infection. Removal of polymorphonuclear neutrophils (PMNs) at the onset of adaptive immunity against Brucella abortus favored bacterial elimination in mice. This was associated with higher levels of interferon gamma (IFN-γ) and a higher proportion of cells expressing interleukin 6 (IL-6) and inducible nitric oxide synthase (iNOS), compatible with M1 macrophages, in PMN-depleted B. abortus-infected (PMNd-Br) mice. At later times in the acute infection phase, the amounts of IFN-γ fell while IL-6, IL-10, and IL-12 became the predominant cytokines in PMNd-Br mice. IL-4, IL-1β, and tumor necrosis factor alpha (TNF-α) remained at background levels at all times of the infection. Depletion of PMNs at the acute stages of infection promoted the premature resolution of spleen inflammation. The efficient removal of bacteria in the PMNd-Br mice was not due to an increase of antibodies, since the immunoglobulin isotype responses to Brucella antigens were dampened. Anti-Brucella antibodies abrogated the production of IL-6, IL-10, and IL-12 but did not affect the levels of IFN-γ at later stages of infection in PMNd-Br mice. These results demonstrate that PMNs have an active role in modulating the course of B. abortus infection after the adaptive immune response has already developed.

The Warburg effect in human pancreatic cancer cells triggers cachexia in athymic mice carrying the cancer cells

Background

Cancer cachexia is a cancer-induced metabolic disorder and a major cause of cancer-induced death. The constituents of cancer cachexia include an increase in energy expenditure, hepatic gluconeogenesis, fat lipolysis, and skeletal-muscle proteolysis and a decrease in body weight. The aetiology of cancer cachexia is unclear and may involve cancer-cell metabolism and secretion. In this study, we investigated whether the high glycolysis in cancer cells (the Warburg effect) triggers cachexia in athymic mice carrying pancreatic cancer cells.

Methods

First, we examined five human pancreatic cancer cell lines for glycolysis and cachectic-cytokine secretion. Consequently, MiaPaCa2 and AsPC1 cells were selected for the present study, because the glycolysis in MiaPaCa2 cells was typically high and that in AsPC1 cells was exceptionally low. In addition, both MiaPaCa2 and AsPC1 cells were competent in the secretion of examined cytokines. Next, we transplanted MiaPaCa2 and AsPC1 cells subcutaneously in different athymic mice for 8 weeks, using intact athymic mice for control. In another experiment, we treated normal mice with the supernatants of MiaPaCa2 or AsPC1 cells for 7 days, using vehicle-treated mice for control. In both models, we measured food intake and body weight, assayed plasma glucose, triglycerides, and TNF-α and used Western blot to determine the proteins that regulated hepatic gluconeogenesis, fat lipolysis, and skeletal-muscle proteolysis in the corresponding tissues. We also studied the effect of MiaPaCa2-cell supernatants on the proteolysis of C2C12 skeletal-muscle cells in vitro.

Results

The athymic mice carrying high-glycolytic MiaPaCa2 cells had anorexia and also showed evidence for cachexia, including increased hepatic gluconeogenesis, fat lipolysis and skeletal-muscle proteolysis and decreased body weight. The athymic mice carrying low-glycolytic AsPC1 cells had anorexia but did not show the above-mentioned evidence for cachexia. When normal mice were treated with the supernatants of MiaPaCa2 or AsPC1 cells, their energy homeostasis was largely normal. Thus, the cachexia in the athymic mice carrying MiaPaCa2 cells may not result from humeral factors released by the cancer cells. In vitro, MiaPaCa2-cell supernatants did not induce proteolysis in C2C12 cells.

Conclusion

The Warburg effect in pancreatic cancer cells is an independent aetiological factor for pancreatic cancer-induced cachexia.

STAT3 promotes IFNγ/TNFα-induced muscle wasting in an NF-κB-dependent and IL-6-independent manner

Cachexia is a debilitating syndrome characterized by involuntary muscle wasting that is triggered at the late stage of many cancers. While the multifactorial nature of this syndrome and the implication of cytokines such as IL‐6, IFNγ, and TNFα is well established, we still do not know how various effector pathways collaborate together to trigger muscle atrophy. Here, we show that IFNγ/TNFα promotes the phosphorylation of STAT3 on Y705 residue in the cytoplasm of muscle fibers by activating JAK kinases. Unexpectedly, this effect occurs both in vitro and in vivo independently of IL‐6, which is considered as one of the main triggers of STAT3‐mediated muscle wasting. pY‐STAT3 forms a complex with NF‐κB that is rapidly imported to the nucleus where it is recruited to the promoter of the iNos gene to activate the iNOS/NO pathway, a well‐known downstream effector of IFNγ/TNFα‐induced muscle loss. Together, these findings show that STAT3 and NF‐κB respond to the same upstream signal and cooperate to promote the expression of pro‐cachectic genes, the identification of which could provide effective targets to combat this deadly syndrome.

Inflammatory Myopathy in Horses With Chronic Piroplasmosis

Horses affected by chronic piroplasmosis may develop poor performance and muscle atrophy. Here we investigate the pathological and immunopathological aspects of myopathy occurring in chronic equine piroplasmosis. The study included 16 horses serologically positive for equine piroplasms presenting with clinical signs and supporting serum biochemical evidence of a myopathy. Skeletal muscle was evaluated by histopathology, immunohistochemistry, indirect immunofluorescence, and molecular detection of piroplasms and inflammatory cytokines in skeletal muscle. Histologic lesions included muscle fiber atrophy (100% of cases), degenerative changes (13/16, 81%), and perivascular perimysial and endomysial lymphocytic infiltrates (81% of cases). In 15 cases (94%), muscle fibers had strong immunostaining for major histocompatibility complex classes I and II. T lymphocyte populations were mainly CD3+, CD8+, and CD4+ in equal proportions, with a lower number of CD79α+ cells. The serum from affected horses was tested by indirect immunofluorescence for binding of IgG, IgM, or IgA to sections of normal equine muscle to detect circulating autoantibodies against muscle antigen(s). In all cases, distinct sarcolemmal staining was detected in sections incubated with serum from affected horses, in contrast to sections incubated with phosphate-buffered saline or equine control sera. Reverse transcription polymerase chain reaction (RT-PCR) testing of muscles from affected animals revealed a significant increase of interferon-γ, interleukin-12, and tumor necrosis factor-α gene expression compared to healthy controls. Theileria equi or Babesia caballi was not detected in samples of affected muscle by RT-PCR. Thus, inflammatory myopathy associated with equine piroplasmosis may involve an autoimmune pathogenesis with upregulation of inflammatory cytokines that may cause myofiber atrophy and degeneration.

Exogenous GDF11 induces cardiac and skeletal muscle dysfunction and wasting

Growth differentiation factor 11 (GDF11), a TGF-beta superfamily member, is highly homologous to myostatin and essential for embryonic patterning and organogenesis. Reports of GDF11 effects on adult tissues are conflicting, with some describing anti-aging and pro-regenerative activities on the heart and skeletal muscle while others opposite or no effects. Herein, we sought to determine the in vivo cardiac and skeletal muscle effects of excess GDF11. Mice were injected with GDF11 secreting cells, an identical model to that used to initially identify the in vivo effects of myostatin. GDF11 exposure in mice induced whole body wasting and profound loss of function in cardiac and skeletal muscle over a 14-day period. Loss of cardiac mass preceded skeletal muscle loss. Cardiac histologic and echocardiographic evaluation demonstrated loss of ventricular muscle wall thickness, decreased cardiomyocyte size, and decreased cardiac function 10 days following initiation of GDF11 exposure. Changes in skeletal muscle after GDF11 exposure were manifest at day 13 and were associated with wasting, decreased fiber size, and reduced strength. Changes in cardiomyocytes and skeletal muscle fibers were associated with activation of SMAD2, the ubiquitin-proteasome pathway and autophagy. Thus, GDF11 over administration in vivo results in cardiac and skeletal muscle loss, dysfunction, and death. Here, serum levels of GDF11 by Western blotting were 1.5-fold increased over controls. Although GDF11 effects in vivo are likely dose, route, and duration dependent, its physiologic changes are similar to myostatin and other Activin receptors ligands. These data support that GDF11, like its other closely related TGF-beta family members, induces loss of cardiac and skeletal muscle mass and function.

Nutrition Modulation of Cachexia/Proteolysis

Cachexia represents progressive wasting of muscle and adipose tissue and is associated with increased morbidity and mortality. Although anorexia usually accompanies cachexia, cachexia rarely responds to increased food intake alone. Our knowledge of the underlying mechanisms responsible for cachexia remains incomplete. However, most states of cachexia are associated with underlying inflammatory processes and/or cancer. These processes activate protein degradation and lipolytic pathways, resulting in tissue loss. In this article, we briefly review the pathophysiology of cachexia and discuss the role of specific nutrient supplements for the treatment of cachexia. The branched chain amino acid leucine, the leucine metabolite beta-hydroxy-beta-methylbutyrate, arginine, glutamine, omega-3 long chain fatty acids, conjugated linoleic acid, and polyphenols have demonstrated some efficacy in animal and/or human studies. Optimal treatment for cachexia is likely aimed at maximizing muscle and adipose synthesis while minimizing degradation.

White adipose tissue IFN-γ expression and signalling along the progression of rodent cancer cachexia

Cachexia is associated with increased morbidity and mortality in cancer. The White adipose tissue (WAT) synthesizes and releases several pro-inflammatory cytokines that play a role in cancer cachexia-related systemic inflammation. IFN-γ is a pleiotropic cytokine that regulates several immune and metabolic functions. To assess whether IFN-γ signalling in different WAT pads is modified along cancer-cachexia progression, we evaluated IFN-γ receptors expression (IFNGR1 and IFNGR2) and IFN-γ protein expression in a rodent model of cachexia (7, 10, and 14days after tumour implantation). IFN-γ protein expression was heterogeneously modulated in WAT, with increases in the mesenteric pad and decreased levels in the retroperitoneal depot along cachexia progression. Ifngr1 was up-regulated 7days after tumour cell injection in mesenteric and epididymal WAT, but the retroperitoneal depot showed reduced Ifngr1 gene expression. Ifngr2 gene expression was increased 7 and 14days after tumour inoculation in mesenteric WAT. The results provide evidence that changes in IFN-γ expression and signalling may be perceived at stages preceding refractory cachexia, and therefore, might be employed as a means to assess the early stage of the syndrome.

Antioxidant supplementation accelerates cachexia development by promoting tumor growth in C26 tumor-bearing mice

More than 50% of patients with advanced stages of colon cancer suffer from progressive loss of skeletal muscle, called cachexia, resulting in reduced quality of life and shortened survival. It is becoming evident that reactive oxygen species (ROS) regulate pathways controlling skeletal muscle atrophy. Herein we tested the hypothesis that antioxidant supplementation could prevent skeletal muscle atrophy in a model of cachectic Colon 26 (C26) tumor-bearing mice. Seven-week-old BALB/c mice were subcutaneously inoculated with colon 26 (C26) cancer cells or PBS. Then C26-mice were daily gavaged during 22 days either with PBS (vehicle) or an antioxidant cocktail whose composition is close to that of commercial dietary antioxidant supplements (rich in catechins, quercetin and vitamin C). We found that antioxidants enhanced weight loss and caused premature death of mice. Antioxidants supplementation failed to prevent (i) the increase in plasma TNF-α levels and systemic oxidative damage, (ii) skeletal muscle atrophy and (iii) activation of the ubiquitin-proteasome system (MuRF-1, MAFbx and polyubiquitinated proteins). Accordingly, immunohistological staining for Ki-67 and the expression of cell cycle inhibitors demonstrated that tumor of supplemented mice developed faster with a concomitant decrease in oxidative damage. Previous studies have shown that the use of catechins and quercetin separately can improve the musculoskeletal function in cachectic animals. However, our results indicate that the combination of these antioxidants reduced survival and enhanced cachexia in C26-mice.

Expression of CCAAT/Enhancer Binding Protein Beta in Muscle Satellite Cells Inhibits Myogenesis in Cancer Cachexia

Cancer cachexia is a paraneoplastic syndrome that causes profound weight loss and muscle mass atrophy and is estimated to be the cause of up to 30% of cancer deaths. Though the exact cause is unknown, patients with cancer cachexia have increased muscle protein catabolism. In healthy muscle, injury activates skeletal muscle stem cells, called satellite cells, to differentiate and promote regeneration. Here, we provide evidence that this mechanism is inhibited in cancer cachexia due to persistent expression of CCAAT/Enhancer Binding Protein beta (C/EBPβ) in muscle myoblasts. C/EBPβ is a bzip transcription factor that is expressed in muscle satellite cells and is normally downregulated upon differentiation. However, in myoblasts exposed to a cachectic milieu, C/EBPβ expression remains elevated, despite activation to differentiate, resulting in the inhibition of myogenin expression and myogenesis. In vivo, cancer cachexia results in increased number of Pax7+ cells that also express C/EBPβ and the inhibition of normal repair mechanisms. Loss of C/EBPβ expression in primary myoblasts rescues differentiation under cachectic conditions without restoring myotube size, indicating that C/EBPβ is an important inhibitor of myogenesis in cancer cachexia.

Prevention of adverse events of interferon γ gene therapy by gene delivery of interferon γ-heparin-binding domain fusion protein in mice

Sustained gene delivery of interferon (IFN) γ can be an effective treatment, but our previous study showed high levels of IFNγ-induced adverse events, including the loss of body weight. These unwanted events could be reduced by target-specific delivery of IFNγ after in vivo gene transfer. To achieve this, we selected the heparin-binding domain (HBD) of extracellular superoxide dismutase as a molecule to anchor IFNγ to the cell surface. We designed three IFNγ derivatives, IFNγ-HBD₁, IFNγ-HBD₂, and IFNγ-HBD₃, each of which had 1, 2, or 3 HBDs, respectively. Each plasmid-encoding fusion proteins was delivered to the liver, a model target in this study, by hydrodynamic tail vein injection. The serum concentration of IFNγ-HBD₂ and IFNγ-HBD₃ after gene delivery was lower than that of IFNγ or IFNγ-HBD₁. Gene delivery of IFNγ-HBD₂, but not of IFNγ-HBD₃, effectively increased the mRNA expression of IFNγ-inducible genes in the liver, suggesting liver-specific distribution of IFNγ-HBD₂. Gene delivery of IFNγ-HBD₂-suppressed tumor growth in the liver as efficiently as that of IFNγ with much less symptoms of adverse effects. These results indicate that the adverse events of IFNγ gene transfer can be prevented by gene delivery of IFNγ-HBD₂, a fusion protein with high cell surface affinity.

Inducible nitric oxide synthase (iNOS) in muscle wasting syndrome, sarcopenia, and cachexia

Muscle atrophy—also known as muscle wasting—is a debilitating syndrome that slowly develops with age (sarcopenia) or rapidly appears at the late stages of deadly diseases such as cancer, AIDS, and sepsis (cachexia). Despite the prevalence and the drastic detrimental effects of these two syndromes, there are currently no widely used, effective treatment options for those suffering from muscle wasting. In an attempt to identify potential therapeutic targets, the molecular mechanisms of sarcopenia and cachexia have begun to be elucidated. Growing evidence suggests that inflammatory cytokines may play an important role in the pathology of both syndromes. As one of the key cytokines involved in both sarcopenic and cachectic muscle wasting, tumor necrosis factor α (TNFα) and its downstream effectors provide an enticing target for pharmacological intervention. However, to date, no drugs targeting the TNFα signaling pathway have been successful as a remedial option for the treatment of muscle wasting. Thus, there is a need to identify new effectors in this important pathway that might prove to be more efficacious targets. Inducible nitric oxide synthase (iNOS) has recently been shown to be an important mediator of TNFα-induced cachectic muscle loss, and studies suggest that it may also play a role in sarcopenia. In addition, investigations into the mechanism of iNOS-mediated muscle loss have begun to reveal potential therapeutic strategies. In this review, we will highlight the potential for targeting the iNOS/NO pathway in the treatment of muscle loss and discuss its functional relevance in sarcopenia and cachexia.

Effect of fish oil supplementation for two generations on changes of lymphocyte function induced by Walker 256 cancer cachexia in rats

Fish oil supplementation has been shown to improve the cachectic state of tumor-bearing animals and humans. Our previous study showed that fish oil supplementation (1 g per kg body weight per day) for 2 generations had anticancer and anticachetic effects in Walker 256 tumor-bearing rats as demonstrated by reduced tumor growth and body weight loss and increased food intake and survival. In this study, the effect of fish oil supplementation for 2 generations on membrane integrity, proliferation capacity, and CD4/CD8 ratio of lymphocytes isolated from mesenteric lymph nodes, spleen, and thymus of Walker 256 tumor-bearing animals was investigated. We also determined fish oil effect on plasma concentration and ex vivo production of cytokines [tumor necrosis factor-alpha (TNF-alpha), interferon-gamma (IFN-gamma), interleukin-4 (IL-4), IL-6, and IL-10]. Lymphocytes from thymus of tumor-bearing rats presented lower viability, but this change was abolished by fish oil supplementation. Tumor growth increased proliferation of lymphocytes from all lymphoid organs, and fish oil supplementation abolished this effect. Ex vivo production of TNF-alpha and IL-6 was reduced in supplemented animals, but IL-4 and IL-10 secretion was stimulated in both nontumor and tumor-bearing rats. IL-10 and IFN-gamma plasma levels was also decreased in supplemented animals. These results suggest that the anticachetic effects of fish oil supplementation for a long period of time (2 generations) in Walker 256 tumor-bearing rats may be associated to a decrease in lymphocyte function as demonstrated by reduced viability, proliferation capacity, and cytokine production.

TNFalpha shedding and epidermal inflammation are controlled by Jun proteins

Inducible epidermal deletion of JunB and c-Jun in adult mice causes a psoriasis-like inflammatory skin disease. Increased levels of the proinflammatory cytokine TNFalpha play a major role in this phenotype. Here we define the underlying molecular mechanism using genetic mouse models. We show that Jun proteins control TNFalpha shedding in the epidermis by direct transcriptional activation of tissue inhibitor of metalloproteinase-3 (TIMP-3), an inhibitor of the TNFalpha-converting enzyme (TACE). TIMP-3 is down-regulated and TACE activity is specifically increased, leading to massive, cell-autonomous TNFalpha shedding upon loss of both JunB and c-Jun. Consequently, a prominent TNFalpha-dependent cytokine cascade is initiated in the epidermis, inducing severe skin inflammation and perinatal death of newborns from exhaustion of energy reservoirs such as glycogen and lipids. Importantly, this metabolic "cachectic" phenotype can be genetically rescued in a TNFR1-deficient background or by epidermis-specific re-expression of TIMP-3. These findings reveal that Jun proteins are essential physiological regulators of TNFalpha shedding by controlling the TIMP-3/TACE pathway. This novel mechanism describing how Jun proteins control skin inflammation offers potential targets for the treatment of skin pathologies associated with increased TNFalpha levels.

Interleukin-1 stimulates catabolism in C2C12 myotubes

Interleukin-1 (IL-1) is an inflammatory cytokine that has been linked to muscle catabolism, a process regulated by muscle-specific E3 proteins of the ubiquitin-proteasome pathway. To address cellular mechanism, we tested the hypothesis that IL-1 induces myofibrillar protein loss by acting directly on muscle to increase expression of two critical E3 proteins, atrogin1/muscle atrophy F-box (MAFbx) and muscle RING-finger 1 (MuRF1). Experiments were conducted using mature C2C12 myotubes to eliminate systemic cytokine effects and avoid paracrine signaling by nonmuscle cell types. Time-course protocols were used to define the sequence of cellular responses. We found that atrogin1/MAFbx mRNA and MuRF1 mRNA are elevated 60-120 min after myotube exposure to either IL-1alpha or IL-1beta. These responses are preceded by signaling events that promote E3 expression. Both IL-1 isoforms stimulate phosphorylation of p38 mitogen-activated protein kinase and stimulate nuclear factor-kappaB (NF-kappaB) signaling; I-kappaB levels fall and NF-kappaB DNA binding activity increases. Other regulators of E3 expression are unaffected by IL-1 [cytosolic oxidant activity, Forkhead-O (Foxo) activity] or respond paradoxically (AKT). Chronic exposure of C2C12 myotubes over 48 h resulted in reduced myotube width and loss of sarcomeric actin. We conclude that IL-1alpha and IL-1beta act via an oxidant- and AKT/Foxo-independent mechanism to activate p38 MAPK, stimulate NF-kappaB signaling, increase expression of atrogin1/MAFbx and MuRF1, and reduce myofibrillar protein in differentiated myotubes.

T-cell protein tyrosine phosphatase is a key regulator in immune cell signaling: lessons from the knockout mouse model and implications in human disease

The immune system requires for its proper ontogeny, differentiation, and maintenance the function of several tyrosine kinases and adapters that create and modify tyrosine phosphorylation sites. Tyrosine phosphorylation is a crucial protein modification in immune cell signaling and can be reversed by protein tyrosine phosphatases (PTPs). Much progress has been made in identifying and understanding PTP function in the immune system. In this review, we present one of these proteins, named T-cell PTPs (TC-PTP) (gene name PTPN2), a classical, non-receptor PTP that is ubiquitously expressed with particularly high expression in hematopoietic tissues. TC-PTP is remarkable not only by the fact that it appears to influence most, if not all, cells involved in the development of the immune system, from stem cells to differentiated lineages, but also recent findings have positioned it at the core of several human diseases from autoimmune disease to cancer.

The cytokine basis of cachexia and its treatment: are they ready for prime time?

Cachexia is a hypercatabolic condition that is often associated with the terminal stages of many diseases, in which the patient's resting metabolic rate is high and loss of muscle and fat tissue mass occur at an alarming rate. The patient also usually has concurrent anorexia, amplifying the wasting syndrome that is cachexia. The greater the extent of cachexia (regardless of underlying disease), the worse the prognosis. Efforts to treat cachexia over the years have fallen short of satisfactorily reversing the wasting syndrome. This article reviews the pathophysiology of cachexia, enumerating the different pro-inflammatory cytokines that contribute to the syndrome and attempting to illustrate their interwoven pathways. We also review the different treatments that have been explored, as well as the recent literature addressing the use of anti-cytokine therapy to treat cachexia.

Induction of the human heat shock promoter HSP70B by nutritional stress: implications for cancer gene therapy

BACKGROUND

We designed and tested, in vitro, an adenoviral construct containing the feline interleukin-12 (IL-12) gene under control of the heat-inducible promoter HSP70B. This construct, AdhspfIL12, was used in a phase I trial in feline soft tissue sarcomas. During the course of our experiments, we noted that IL-12 was being produced in the transfected Crandell Feline Kidney (CrFK) cells under certain conditions even in the absence of hyperthermia. This observation was further explored to identify the cause of this unintended HSP70B induction.

MATERIALS AND METHODS

We used real-time PCR as a sensitive method to quantitatively detect the presence of even small amounts of IL-12 mRNA. This served as a surrogate indicator of HSP70B induction. Various conditions were tested to induce the heat shock promoter, including nutritional deprivation, radiation and changes in pH.

RESULTS

Nutritional stresses, specifically the absence of glucose and glutamine, could induce the heat shock promoter, thus, resulting in production of the downstream gene product. Other factors known to trigger the heat shock response, pH change, and reactive oxygen species production were also studied but were not found to contribute to heat shock promoter induction in our setting.

CONCLUSIONS

The human heat shock promoter (HSP70B) is reported to be an efficient and tightly regulated promoter. We discovered, using sensitive real-time PCR techniques, that it can also be induced in response to cellular nutrient stresses. The pros and cons of this phenomenon and its implications for cancer gene therapy are discussed.

IFN-γ does not mimic the catabolic effects of TNF-α

Cachexia is common in chronic inflammatory diseases and is attributed, in part, to an elevation of circulating proinflammatory cytokines. TNF-α is the prototype in this category. IFN-γ is also thought to play a role, but the evidence supporting this model is primarily indirect. To determine the direct effects of IFN-γ stimulation on muscle cells, we selected key components of the procatabolic signaling pathways by which TNF-α stimulates protein loss. We tested two hypotheses: 1) IFN-γ mimics TNF-α signaling by increasing intracellular oxidant activity and activating MAPKs and NF-κB and 2) IFN-γ increases the expression of the ubiquitin ligases atrogin1/MAFbx and muscle-specific ring finger protein 1 (MuRF1). Results showed that treatment with IFN-γ at 60 ng/ml increased Stat1 phosphorylation after 15 min, indicating receptor activation. IFN-γ had no effect on cytosolic oxidant activity, as measured by 2′,7′-dichlorofluorescein oxidation. Nor did IFN-γ activate JNK, ERK1/2, or p38 MAPK, as assessed by Western blot. Treatment for up to 60 min did not decrease IκB-α protein levels, as measured by Western blot analysis, or the DNA binding activity of NF-κB, as measured by EMSA. After 6 h, IFN-γ decreased Akt phosphorylation and increased atrogin1/MAFbx and MuRF1 mRNA. Daily treatment for up to 72 h did not alter adult fast-type myosin heavy chain content or the total protein-to-DNA ratio. These data show that responses of myotubes to IFN-γ and TNF-α differ markedly and provide little evidence for a direct catabolic effect of IFN-γ on muscle.

Prevention of cancer cachexia by pyrrolidine dithiocarbamate (PDTC) in colon 26 tumor-bearing mice

BACKGROUND

The precise mechanism of cancer cachexia is not fully elucidated. This study was aimed to assess the effect of pyrrolidine dithiocarbamate (PDTC, an inhibitor of NFkappaB) on interleukin (IL)-6 synthesis and cachexia in colon 26 tumor-bearing mice.

METHODS

Murine colon 26 adenocarcinoma cells were inoculated subcutaneously in male BALB/c mice to induce cachexia. Saline and various doses of PDTC (10, 50, or 100 mg/kg/d) were given intraperitoneally daily from 7 days after tumor inoculation to killing. Body weight, food intake, and tumor volume were monitored daily. Serum and tumor tissue levels of IL-6, serum biochemical indicator, and activity of NFkappaB in tumor tissue were investigated in all mice.

RESULTS

Significant tissue wasting was observed in all tumor-bearing mice. By day 16, carcass weights of untreated tumor-bearing mice were about 71.3% of healthy controls (p < .01), and the weights of gastrocnemius muscle and epididymal fat were lowered by 42.4% and 70.4% (p < .01), respectively. Furthermore, tumor-bearing caused a significant decrease of serum albumin, glucose, and triglyceride (p < .01) and increase of IL-6 (p < .01) in serum and tumor tissues. Administration of PDTC dose dependently inhibited the NFkappaB activation in tumor tissues, inhibited IL-6 synthesis of the tumor cells, and attenuated the wasting of carcass weight, gastrocnemius muscle, and epididymal fat. Tumor growth was inhibited by PDTC with 100 mg/kg (p < .05). No differences of food intake were found between groups (p > .05).

CONCLUSIONS

These results suggest that PDTC, an inhibitor of NFkappaB, can attenuate the development of cachexia in colon 26 tumor-bearing mice through inhibition of IL-6 synthesis regulated by NFkappaB.

IGF-I does not prevent myotube atrophy caused by proinflammatory cytokines despite activation of Akt/Foxo and GSK-3beta pathways and inhibition of atrogin-1 mRNA

Myofibrillar protein loss occurring in catabolic situations is considered to be mediated by the release of proinflammatory cytokines and associated with a decrease in circulating and muscle levels of insulin-like growth factor I (IGF-I). In this paper, we investigated whether the C(2)C(12) myotube atrophy caused in vitro by TNF-alpha/IFN-gamma cytokines might be reversed by exogenous IGF-I. Our results showed that, despite the presence of TNF-alpha/IFN-gamma, IGF-I retained its full ability to induce the phosphorylation of Akt, Foxo3a, and GSK-3beta (respectively, 16-fold, 9-fold, and 2-fold) together with a decrease in atrogin-1 mRNA (-39%, P < 0.001). Although this ubiquitin ligase has been reported to accelerate the degradation of MyoD, a myogenic transcription factor driving the transcription of myosin heavy chain (MHC), IGF-I failed to blunt the reduction of MyoD and MHC caused by TNF-alpha/IFN-gamma. Moreover, IGF-I only very slightly attenuated the myotube atrophy induced by TNF-alpha/IFN-gamma (TNF-alpha/IFN-gamma 15.48 mum alone vs. TNF-alpha/IFN-gamma/IGF-I 16.97 mum, P < 0.001). In conclusion, our data show that IGF-I does not reverse the myotube atrophy induced by TNF-alpha/IFN-gamma despite the phosphorylation of Foxo and GSK-3beta and the downregulation of atrogin-1 mRNA. Our study suggests therefore that factors other than IGF-I decrease are responsible for the muscle atrophy caused by proinflammatory cytokines.

Capecitabine improves cancer cachexia and normalizes IL-6 and PTHrP levels in mouse cancer cachexia models

PURPOSE

To clarify the potential of parathyroid hormone-related protein (PTHrP) and interleukin-6 (IL-6) as cachectic factors in a colon 26 model and the effects of capecitabine on cancer cachexia as determined by plasma levels of IL-6 and PTHrP and body weight loss.

METHODS

From two colon 26 sublines-cancer cachectic clone20 and non-cachectic clone5 plasma levels of PTHrP protein and mRNA expression levels in tumor tissues were compared. An IL-6 neutralizing antibody, a PTHrP neutralizing antibody, and capecitabine were administered into mice bearing clone20 and their anticachectic effects evaluated.

RESULTS

The plasma level of PTHrP protein in mice bearing clone20 was higher than that in mice bearing clone5. The expression level of PTHrP mRNA was 49-fold higher in tumor tissues of clone20 than of clone5, according to GeneChip analysis. PTHrP antibody as well as IL-6 antibody suppressed wasting of the body and gastrocnemius and adipose tissue weights. PTHrP antibody suppressed the induction of hypercalcemia but not hypoglycemia or elevation of IL-6, whereas IL-6 antibody suppressed the induction of hypoglycemia but not hypercalcemia or elevation of PTHrP. Capecitabine, a fluorinated pyrimidine anticancer agent, improved body wasting of mice bearing clone20 at a low dose with no reduction of tumor volume. Furthermore, capecitabine lowered the levels of PTHrP and IL-6 in plasma and suppressed hypoglycemia and hypercalcemia in this model. Capecitabine also showed anticachectic effects on cachexia in a cancer model induced by human cervical cancer cell line Y (also known as Yumoto).

CONCLUSIONS

PTHrP and IL-6 were found to be factors in the development of cachexia in a colon 26 cancer model, and capecitabine improved cancer cachexia by suppressing the plasma levels of IL-6 and PTHrP in colon 26 and Y cachectic models.

IFN-alpha induces apoptosis of adipose tissue cells

Interferon alpha (IFN-alpha) is produced in response to viral infections and used clinically in the therapy of a variety of cancers and viral infections. IFN-alpha treatment is often associated with severe weight reduction. To elucidate the mechanism of IFN-associated weight loss, we studied its effect on adipocytes in vitro and in vivo. Diet-induced obese (DIO) C57BL/6 mice were treated continuously for 8 days with human IFN-alpha A/D (100 U/g body weight) or with vehicle alone. The body weight and adipose cell size of IFN-alpha A/D-treated DIO mice were significantly lower (P<0.05 and P<0.001, respectively) as compared with those of control DIO mice. PI3K and Bcl-2 were down-regulated whereas Bax expression was elevated in adipose tissue following IFN treatment as compared to adipose tissue of control DIO mice. Treatment of differentiated 3T3-F442A adipocytes with IFN-alpha A/D (250 U/ml, 36 h) significantly increased the number of apoptotic cells from 15.8% in control cells to 56+/-6%. In conclusion, weight loss following IFN-alpha therapy is due at least in part to increased apoptosis of adipocytes.

Effects of anti-parathyroid hormone-related protein monoclonal antibody and osteoprotegerin on PTHrP-producing tumor-induced cachexia in nude mice

We have previously demonstrated that parathyroid hormone-related protein (PTHrP) is a cachexia inducer, but it is still not known what PTHrP effects on target tissues induce the cachexia. Therefore, we examined the effects of anti-PTHrP antibody and osteoprotegerin (OPG) on PTHrP-producing tumor-induced cachexia. Nude mice bearing PTHrP-producing human lung cancer cells (HARA-B) exhibited cachexia with hypercalcemia 3-4 weeks after inoculation, accompanied by losses in body, adipose tissue, and muscle weight. OPG ameliorated hypercalcemia, as did neutralization of PTHrP with antibody; and it increased both body and adipose tissue weights. These increases in body and adipose tissue weight, however, were significantly less than those in mice treated with anti-PTHrP antibody. Simultaneous administration of OPG and anti-PTHrP antibody caused significant increases in body, adipose tissue, and muscle weight, along with an immediate decrease in blood ionized calcium levels. The increase in body weight was similar to that observed in mice treated with anti-PTHrP antibody alone, and the decrease in the blood ionized calcium levels was significantly greater than that in mice treated with OPG or anti-PTHrP antibody alone. These results suggest that an effect of PTHrP on target tissues other than hypercalcemia is involved in the development of cachexia. Expression of cachexia-inducing proinflammatory cytokines (interleukin-6 and leukemia inhibitory factor) is stimulated by PTHrP. This might be a mechanism by which PTHrP produces tumor-induced cachexia. It is also suggested that OPG and anti-PTHrP antibody synergistically act to ameliorate hypercalcemia, although the mechanism responsible for this is unclear.

The role of glucocorticoids in the induction of zinc-alpha2-glycoprotein expression in adipose tissue in cancer cachexia

Loss of adipose tissue in cancer cachexia in mice bearing the MAC16 tumour arises from an increased lipid mobilisation through increased expression of zinc-α₂-glycoprotein (ZAG) in white (WAT) and brown (BAT) adipose tissue. Glucocorticoids have been suggested to increase ZAG expression, and this study examines their role in cachexia and the mechanisms involved. In mice bearing the MAC16 tumour, serum cortisol concentrations increased in parallel with weight loss, and the glucocorticoid receptor antagonist RU38486 (25 mg kg⁻¹) attenuated both the loss of body weight and ZAG expression in WAT. Dexamethasone (66 μg kg⁻¹) administration to normal mice produced a six-fold increase in ZAG expression in both WAT and BAT, which was also attenuated by RU38486. In vitro studies using 3T3-L1 adipocytes showed dexamethasone (1.68 μM) to stimulate lipolysis and increase ZAG expression, and both were attenuated by RU38486 (10 μM), anti-ZAG antibody (1 μgml⁻¹), and the β3-adrenoreceptor (β3-AR) antagonist SR59230A (10 μM). Zinc-α₂-glycoprotein also increased its own expression and this was attenuated by SR59230A, suggesting that it was mediated through the β3-AR. This suggests that glucocorticoids stimulate lipolysis through an increase in ZAG expression, and that they are responsible for the increase in ZAG expression seen in adipose tissue of cachectic mice.

Characterization of a Human Homologue of Proteolysis-Inducing Factor and Its Role in Cancer Cachexia

Cachexia is an important cause of secondary morbidity and mortality in patients with cancer. Previous studies have suggested that cancer-associated cachexia may be due in part to tumor-specific production and secretion of a glycosylated peptide, proteolysis-inducing factor, originally identified in a murine cancer cachexia model. We report here the cloning of a human cDNA that generates a peptide having high-sequence homology to this proteolysis-inducing factor. Constitutive expression of human proteolysis-inducing factor is low or absent in most normal human tissues but appears to be elevated in some human tumors. Stable forced expression of human proteolysis-inducing factor in multiple murine and human cell lines results in a secreted protein, but no glycosylation of the protein is detected. In addition, tumor xenografts engineered to overexpress human proteolysis-inducing factor protein do not induce cachexia in vivo. These findings raise important questions as to potential cross-species differences in protein sequence and processing of murine proteolysis-inducing factor and human proteolysis-inducing factor, as well as the nature of the relationship between human proteolysis-inducing factor and the development of cancer cachexia.

Cancer cachexia is regulated by selective targeting of skeletal muscle gene products

Cachexia is a syndrome characterized by wasting of skeletal muscle and contributes to nearly one-third of all cancer deaths. Cytokines and tumor factors mediate wasting by suppressing muscle gene products, but exactly which products are targeted by these cachectic factors is not well understood. Because of their functional relevance to muscle architecture, such targets are presumed to represent myofibrillar proteins, but whether these proteins are regulated in a general or a selective manner is also unclear. Here we demonstrate, using in vitro and in vivo models of muscle wasting, that cachectic factors are remarkably selective in targeting myosin heavy chain. In myotubes and mouse muscles, TNF-alpha plus IFN-gamma strongly reduced myosin expression through an RNA-dependent mechanism. Likewise, colon-26 tumors in mice caused the selective reduction of this myofibrillar protein, and this reduction correlated with wasting. Under these conditions, however, loss of myosin was associated with the ubiquitin-dependent proteasome pathway, which suggests that mechanisms used to regulate the expression of muscle proteins may be cachectic factor specific. These results shed new light on cancer cachexia by revealing that wasting does not result from a general downregulation of muscle proteins but rather is highly selective as to which proteins are targeted during the wasting state.