Role of cytokines in cancer cachexia in a murine model of intracerebral injection of human tumours

Leukemia inhibitory factor, a double-edged sword with therapeutic implications in human diseases

Leukemia inhibitory factor (LIF) is a pleiotropic cytokine of the interleukin-6 (IL-6) superfamily. LIF was initially discovered as a factor to induce the differentiation of myeloid leukemia cells and thus inhibit their proliferation. Subsequent studies have highlighted the multi-functions of LIF under a wide variety of physiological and pathological conditions in a highly cell-, tissue-, and context-dependent manner. Emerging evidence has demonstrated that LIF plays an essential role in the stem cell niche, where it maintains the homeostasis and regeneration of multiple somatic tissues, including intestine, neuron, and muscle. Further, LIF exerts a crucial regulatory role in immunity and functions as a protective factor against many immunopathological diseases, such as infection, inflammatory bowel disease (IBD), and graft-verse-host disease (GVHD). It is worth noting that while LIF displays a tumor-suppressive function in leukemia, recent studies have highlighted the oncogenic role of LIF in many types of solid tumors, further demonstrating the complexities and context-dependent effects of LIF. In this review, we summarize the recent insights into the roles and mechanisms of LIF in stem cell homeostasis and regeneration, immunity, and cancer, and discuss the potential therapeutic options for human diseases by modulating LIF levels and functions.

The Molecular Basis and Therapeutic Potential of Leukemia Inhibitory Factor in Cancer Cachexia

Simple Summary

The mechanism of cancer cachexia is linked to a variety of factors, and inflammatory factors are thought to play a key role. We summarize the main roles of LIF in the development of cancer cachexia, including promoting fat loss, inducing skeletal muscle atrophy and causing anorexia nervosa. The main aim of this review is to increase the understanding of the effects of LIF in cachexia and to provide new insights into the treatment of cancer cachexia.

Abstract

Cachexia is a chronic metabolic syndrome that is characterized by sustained weight and muscle mass loss and anorexia. Cachexia can be secondary to a variety of diseases and affects the prognosis of patients significantly. The increase in inflammatory cytokines in plasma is deeply related to the occurrence of cachexia. As a member of the IL-6 cytokine family, leukemia inhibitory factor (LIF) exerts multiple biological functions. LIF is over-expressed in the cancer cells and stromal cells of various tumors, promoting the malignant development of tumors via the autocrine and paracrine systems. Intriguingly, increasing studies have confirmed that LIF contributes to the progression of cachexia, especially in patients with metastatic tumors. This review combines all of the evidence to summarize the mechanism of LIF-induced cachexia from the following four aspects: (i) LIF and cancer-associated cachexia, (ii) LIF and alterations of adipose tissue in cachexia, (iii) LIF and anorexia nervosa in cachexia, and (iv) LIF and muscle atrophy in cachexia. Considering the complex mechanisms in cachexia, we also focus on the interactions between LIF and other key cytokines in cachexia and existing therapeutics targeting LIF.

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.

The emerging role of leukemia inhibitory factor in cancer and therapy

Leukemia inhibitory factor (LIF) is a multi-functional cytokine of the interleukin-6 (IL-6) superfamily. Initially identified as a factor that inhibits the proliferation of murine myeloid leukemia cells, LIF displays a wide variety of important functions in a cell-, tissue- and context-dependent manner in many physiological and pathological processes, including regulating cell proliferation, pluripotent stem cell self-renewal, tissue/organ development and regeneration, neurogenesis and neural regeneration, maternal reproduction, inflammation, infection, immune response, and metabolism. Emerging evidence has shown that LIF plays an important but complex role in human cancers; while LIF displays a tumor suppressive function in some types of cancers, including leukemia, LIF is overexpressed and exerts an oncogenic function in many more types of cancers. Further, targeting LIF has been actively investigated as a novel strategy for cancer therapy. This review summarizes the recent advances in the studies on LIF in human cancers and its potential application in cancer therapy. A better understanding of the role of LIF in different types of cancers and its underlying mechanisms will help to develop more effective strategies for cancer therapy.

Nutraceuticals and Exercise against Muscle Wasting during Cancer Cachexia

Cancer cachexia (CC) is a debilitating multifactorial syndrome, involving progressive deterioration and functional impairment of skeletal muscles. It affects about 80% of patients with advanced cancer and causes premature death. No causal therapy is available against CC. In the last few decades, our understanding of the mechanisms contributing to muscle wasting during cancer has markedly increased. Both inflammation and oxidative stress (OS) alter anabolic and catabolic signaling pathways mostly culminating with muscle depletion. Several preclinical studies have emphasized the beneficial roles of several classes of nutraceuticals and modes of physical exercise, but their efficacy in CC patients remains scant. The route of nutraceutical administration is critical to increase its bioavailability and achieve the desired anti-cachexia effects. Accumulating evidence suggests that a single therapy may not be enough, and a bimodal intervention (nutraceuticals plus exercise) may be a more effective treatment for CC. This review focuses on the current state of the field on the role of inflammation and OS in the pathogenesis of muscle atrophy during CC, and how nutraceuticals and physical activity may act synergistically to limit muscle wasting and dysfunction.

The role of cytokines in cancer cachexia

PURPOSE OF REVIEW

The present investigation is devoted to uncovering the different signaling pathways - particularly transcriptional factors - involved in muscle wasting.

RECENT FINDINGS

Although the search for the cachectic factor(s) started a long time ago, and although many scientific and economic efforts have been devoted to its discovery, we are still a long way from knowing the whole truth. In this review we describe recent findings about the tumor necrosis factor (TNF)-alpha, interleukin (IL)-6, TWEAK and myostatin actions in cancer cachexia models.

SUMMARY

The main aim of the present review is to summarize and evaluate the different molecular mechanisms and catabolic mediators (mainly cytokines) involved in cancer cachexia since they may represent targets for future promising clinical investigations.

The major inflammatory mediator interleukin-6 and obesity

Adipose tissue is one of the main sources of inflammatory mediators, with interleukin-6 (IL-6) among them. Although high systemic levels of inflammatory mediators are cachectogenic and/or anorexic, today it is a widely propagated thesis that in the background of obesity, a low level of chronic inflammation can be found, with IL-6 being one of the many suggested mediators. This paper reviews the studies describing elevated IL-6 levels in obese patients and the role of adipocytes and adipose-tissue macrophages in the production of IL-6. The secretion of IL-6 is regulated by several physiologic or pathologic factors: hormones, cytokines, diet, physical activity, stress, hypoxia, and others. Adipose tissue-derived IL-6 may have an effect on metabolism through several mechanisms, including adipose tissue-specific gene expression, triglyceride release, lipoprotein lipase downregulation, insulin sensitivity, and so on. Having a better understanding of these mechanisms may contribute to the prevention and treatment of obesity.

Prostaglandins and sickness behavior: old story, new insights

Previous evidence has shown that prostaglandins play a key role in the development of sickness behavior observed during inflammatory states. In particular, prostaglandin E2 (PGE2) is produced in the brain by a variety of inflammatory signals such as endotoxins or cytokines. Its injection has been also shown to induce symptoms of sickness behavior. The role of cyclooxygenase enzymes (COX), the rate-limiting enzymes converting arachidonic acid into prostaglandins, in sickness behavior has been extensively studied, and it has been demonstrated that strategies aiming at inhibiting these enzymes limit anorexia, body weight loss and fever in animals with inflammatory diseases. However, inhibiting COX activity may lead to negative gastric or cardiovascular effects, since COX enzymes play a role in the synthesis of others prostanoids with various and sometimes contrasting properties. Recently, prostaglandin E synthases (PGES), which specifically catalyze the final step of PGE2 biosynthesis, were characterized. Among these enzymes, the microsomal prostaglandin E synthase-1 (mPGES-1) was of a particular interest since it was shown to be up-regulated by inflammatory signals in a variety of cell types. Moreover, mPGES-1 was shown to be crucial for correct immune-to-brain communication and induction of fever and anorexia by pro-inflammatory agents. This review takes stock of previous knowledge and recent advances in understanding the role of prostaglandins and of their specific synthesizing enzymes in the molecular mechanisms underlying sickness behavior. The review concludes with a short summary of key questions that remain to be addressed and points out therapeutic developments in this research field.

Effects of eicosapentaenoic and docosahexaenoic n-3 fatty acids from fish oil and preferential Cox-2 inhibition on systemic syndromes in patients with advanced lung cancer

Under the common denomination of Systemic Immune-Metabolic Syndrome (SIMS), we grouped many symptoms that share a similar pathophysiologic background. SIMS is the result of the dysfunctional interaction of tumor cells, stroma cells, and the immune system, leading to the release of cytokines and other systemic mediators such as eicosanoids. SIMS includes systemic syndromes such as paraneoplastic hemopathies, hypercalcemia, coagulopathies, fatigue, weakness, cachexia, chronic nausea, anorexia, and early satiety among others. Eicosapentaenoic and docosahexaenoic n-3 fatty acids from fish oil can help in the management of persistent chronic inflammatory states, but treatment's compliance is generally poor. Preferentially, Cox-2 inhibition can create a favorable pattern of cytokines by decreasing the production of certain eicosanoids, although their role in SIMS is unknown. The aim of this study was to test the hypothesis that by modulating systemic inflammation through an eicosanoid-targeted approach, some of the symptoms of the SIMS could be controlled. We exclusively evaluated 12 patients for compliance. Patients were assigned 1 of the 4 treatment groups (15-, 12-, 9-, or 6-g dose, fractionated every 8 h). For patients assigned to 15 and 12 doses, the overall compliance was very poor and unsatisfactory for patients receiving the 9-g dose. The maximum tolerable dose was calculated to be around 2 capsules tid (6 g of fish oil per day). A second cohort of 22 patients with advanced lung cancer and SIMS were randomly assigned to receive either fish oil, 2 g tid, plus placebo capsules bid (n = 12) or fish oil, 2 g tid, plus celecoxib 200 mg bid (n = 10). All patients in both groups received oral food supplementation. After 6 wk of treatment, patients receiving fish oil + placebo or fish oil + celecoxib showed significantly more appetite, less fatigue, and lower C-reactive protein (C-RP) values than their respective baselines values (P < 0.02 for all the comparisons). Additionally, patients in the fish oil + celecoxib group also improved their body weight and muscle strength compared to baseline values (P < 0.02 for all the comparisons). Comparing both groups, patients receiving fish oil + celecoxib showed significantly lower C-RP levels (P = 0.005, t-test), higher muscle strength (P = 0.002, t-test) and body weight (P = 0.05, t-test) than patients receiving fish oil + placebo. The addition of celecoxib improved the control of the acute phase protein response, total body weight, and muscle strength. Additionally, the consistent nutritional support used in our patients could have helped to maximize the pharmacological effects of fish oil and/or celecoxib. This study shows that by modulating the eicosanoid metabolism using a combination of n-3 fatty acids and cyclooxygenase-2 inhibitor, some of the signs and symptoms associated with a SIMS could be ameliorated.

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.

Central infusion of the melanocortin receptor antagonist agouti-related peptide (AgRP(83-132)) prevents cachexia-related symptoms induced by radiation and colon-26 tumors in mice

Cachexia is a clinical wasting syndrome that occurs in multiple disease states, and is associated with anorexia and a progressive loss of body fat and lean mass. The development of new therapeutics for this disorder is needed due to poor efficacy and multiple side effects of current therapies. The pivotal role played by the central melanocortin system in regulating body weight has made this an attractive target for novel cachexia therapies. The mixed melanocortin receptor antagonist AgRP is an endogenous peptide that induces hyperphagia. Here, we used AgRP(83-132) to investigate the ability of melanocortin antagonism to protect against clinical features of cachexia in two distinct animal models. In an acute model, food intake and body weight gain were reduced in mice exposed to radiation (300 RAD), and delivery of AgRP(83-132) into the lateral cerebral ventricle prevented these effects. In a chronic tumor cachexia model, adult mice were injected subcutaneously with a cell line derived from murine colon-26 adenocarcinoma. Typical of cachexia, tumor-bearing mice progressively reduced body weight and food intake, and gained significantly less muscle mass than controls. Administration of AgRP(83-132) into the lateral ventricles significantly increased body weight and food intake, and changes in muscle mass were similar to the tumor-free control mice. These findings support the idea that antagonism of the central melanocortin system can reduce the negative impact of cachexia and radiation therapy.

Feeding, exploratory, anxiety- and depression-related behaviors are not altered in interleukin-6-deficient male mice

Interleukin-6 (IL-6) has been implicated in behavioral responses associated with inflammation, sickness behavior and various nervous system disorders. We studied a range of different behaviors in IL-6-knockout (IL-6ko) and wild-type (WT) male mice. No significant differences were observed in ambulatory, exploratory, and stereotypic activities in home or novel cages, in an open field (OF), in the multicompartment chamber (MCC), or in the elevated plus-maze (EPM). IL-6ko mice shed fewer fecal boli than WT mice in the OF, in novel cages and in the MCC although this effect was not statistically significant in the OF. In novel cages, intraperitoneal (i.p.) injection of IL-6 (1 microg) depressed ambulatory activity slightly more in IL-6ko than in WT mice. Restraint and interleukin-1beta (IL-1beta, 100 ng i.p.) decreased exploration of mice in the MCC and EPM, but there was no indication of altered sensitivity in IL-6ko mice. No significant differences were detected in the tail suspension and the Porsolt forced swim tests. IL-1beta and lipopolysaccharide (LPS 1 microg i.p.) injection depressed sweetened milk and solid food intake similarly in IL-6ko and WT mice, but IL-6 had no effect, suggesting that IL-6 is not involved in these effects of IL-1 or LPS. However, IL-1beta and LPS depressed body weight more in WT than in IL-6ko mice. Plasma corticosterone and basal concentrations of catecholamines, indoleamines and their metabolites in several brain regions were similar. The responses in these measures to IL-1beta and LPS were also similar, except that there were no significant changes in tryptophan and serotonin metabolism in IL-6ko mice. This may reflect a role for IL-6 in the tryptophan and serotonin responses to IL-1 and LPS. It is concluded that the lack of IL-6 is not associated with substantial alterations in several different mouse behaviors, and in the responses to restraint, IL-1beta, IL-6 and LPS.

Mediators involved in the cancer anorexia-cachexia syndrome: past, present, and future

The cachectic syndrome, characterized by a marked weight loss, anorexia, asthenia, and anemia is invariably associated with the presence and growth of the tumor and leads to a malnutrition status due to the induction of anorexia or decreased food intake. In addition, the competition for nutrients between the tumor and the host leads to an accelerated starvation state, which promotes severe metabolic disturbances in the host, including hypermetabolism, which leads to an increased energetic inefficiency. Although the search for the cachectic factor(s) started a long time ago, and although many scientific and economic efforts have been devoted to its discovery, we are still a long way from knowing the whole truth. Present investigation is devoted to revealing the different signaling pathways, in particular transcriptional factors involved in muscle wasting. The main aim of the present review is to summarize and evaluate the different molecular mechanisms and catabolic mediators (both humoral and tumoral) involved in cancer cachexia since they may represent targets for future promising clinical investigations.

Cytokines as mediators and targets for cancer cachexia

The cachexia syndrome, characterized by a marked weight loss, anorexia, asthenia and anaemia, is invariably associated with the growth of a tumour and leads to a malnutrition status caused by the induction of anorexia or decreased food intake. In addition, the competition for nutrients between the tumour and the host results in a state of accelerated catabolism, which promotes severe metabolic disturbances in the patient. The search for the cachectic factor(s) started a long time ago, and many scientific and economic efforts have been devoted to its discovery, but we are still a long way from a complete answer. The present review aims to evaluate the different molecular mechanisms and catabolic mediators (both humoural and tumoural) that are involved in cancer cachexia and to discuss their potential as targets for future clinical investigations.

The pivotal role of cytokines in muscle wasting during cancer

The cachectic syndrome, characterized by a marked weight loss, anorexia, asthenia and anemia, is invariably associated with the presence and growth of the tumour and leads to a malnutrition status due to the induction of anorexia or decreased food intake. In addition, the competition for nutrients between the tumour and the host leads to an accelerated catabolic state, which promotes severe metabolic disturbances in the host, including hypermetabolism, which leads to an increased energetic inefficiency. Although the search for the cachectic factor(s) started a long time ago, and although many scientific and economic efforts have been devoted to its discovery, we are still a long way from knowing the whole truth. Present investigation is devoted to unrevealing the different signaling pathways (particulary transcriptional factors) involved in muscle wasting. The main aim of the present review is to summarize and evaluate the different molecular mechanisms and catabolic mediators involved in cancer cachexia since they may represent targets for future promising clinical investigations.

The pivotal role of cytokines in muscle wasting during cancer

The cachectic syndrome, characterized by a marked weight loss, anorexia, asthenia and anemia, is invariably associated with the presence and growth of the tumour and leads to a malnutrition status due to the induction of anorexia or decreased food intake. In addition, the competition for nutrients between the tumour and the host leads to an accelerated catabolic state, which promotes severe metabolic disturbances in the host, including hypermetabolism, which leads to an increased energetic inefficiency. Although the search for the cachectic factor(s) started a long time ago, and although many scientific and economic efforts have been devoted to its discovery, we are still a long way from knowing the whole truth. Present investigation is devoted to unrevealing the different signaling pathways (particularly transcriptional factors) involved in muscle wasting. The main aim of the present review is to summarize and evaluate the different molecular mechanisms and catabolic mediators involved in cancer cachexia since they may represent targets for future promising clinical investigations.

Molecular mechanisms involved in muscle wasting in cancer and ageing: cachexia versus sarcopenia

The aim of the present review is to summarize and evaluate the different mechanisms and catabolic mediators involved in cancer cachexia and ageing sarcopenia since they may represent targets for future promising clinical investigations. Cancer cachexia is a syndrome characterized by a marked weight loss, anorexia, asthenia and anemia. In fact, many patients who die with advanced cancer suffer from cachexia. The degree of cachexia is inversely correlated with the survival time of the patient and it always implies a poor prognosis. Unfortunately, at the clinical level, cachexia is not treated until the patient suffers from a considerable weight loss and wasting. At this point, the cachectic syndrome is almost irreversible. The cachectic state is often associated with the presence and growth of the tumour and leads to a malnutrition status due to the induction of anorexia. In recent years, age-related diseases and disabilities have become of major health interest and importance. This holds particularly for muscle wasting, also known as sarcopenia, that decreases the quality of life of the geriatric population, increasing morbidity and decreasing life expectancy. The cachectic factors (associated with both depletion of fat stores and muscular tissue) can be divided into two categories: of tumour origin and humoural factors. In conclusion, more research should be devoted to the understanding of muscle wasting mediators, both in cancer and ageing, in particular the identification of common mediators may prove as a good therapeutic strategies for both prevention and treatment of wasting both in disease and during healthy ageing.

Interleukin-1beta system in anorectic catabolic tumor-bearing rats

PURPOSE OF REVIEW

The onset of cancer anorexia and the accompanying neurological symptoms and signs involve the general influence of cytokines on the brain. Using methylcholanthrene to induce tumors in Fischer 344 rats, we measured various specific components of the cytokine-induced anorectic reaction, including: (1) IL-1beta system components (ligand, signaling receptor, receptor accessory proteins, and receptor antagonist); (2) TNF-alpha; (3) TGF-beta1; and (4) IFN-gamma in the tumor tissue, the liver and the brain.

RECENT FINDINGS

The data show that IL-1beta, TNF-alpha and IFN-gamma messenger RNA were detected in the tumor tissue of anorectic tumor-bearing rats. In brain regions, anorexia is associated with the upregulation of IL-1beta and its receptor mRNA. All other mRNA remained unchanged in the brain regions examined.

SUMMARY

This suggests that IL-1beta and its receptor may play a significant role in this model of cancer-associated anorexia. In vivo, the characterization of cytokine components in the brain may provide data for potential pharmacological interventions to ameliorate the anorexia of disease.

Cachexia-like symptoms predict a worse prognosis in localized t1 renal cell carcinoma

PURPOSE

Although cachexia is a common sequela of advanced and metastatic renal cell carcinoma (RCC), cachexia-like symptoms may also represent a paraneoplastic finding. We assessed the prognostic significance of these symptoms in patients with stage T1 RCC.

MATERIALS AND METHODS

Using the kidney cancer database at our institution 250 patients were identified who underwent partial or radical nephrectomy for T1N0M0 RCC between 1989 and 2001. The prognostic significance of the symptoms present at diagnosis and findings on preoperative laboratory evaluation were examined.

RESULTS

Mean and median followup was 33 and 43 months, respectively. Malaise, weight loss, anorexia and hypoalbuminemia were cachexia related findings that were significant predictors of worse disease specific survival (DSS). DSS in patients with 1 vs greater than 1 cachexia related symptoms was not significantly different (p = 0.077). Therefore, any patient with at least 1 cachexia related finding was considered to be positive for cachexia and cachexia occurred in 37 (14.8%). Cachexia was associated with significantly worse recurrence-free survival (HR 3.03, p = 0.032) and DSS (HR 4.39, p = 0.011) even after controlling for tumor size, grade and performance status. The 5-year survival rate in patients with low grade (1 or 2) tumors with and without cachexia was 91% and 81%, respectively. The 5-year survival rate in patients with high grade (3 or 4) tumors with and without cachexia was 75% and 55%, respectively.

CONCLUSIONS

Cachexia-like symptoms independently predict a worse prognosis in patients with T1 RCC. Patients with cachexia (malaise, weight loss, anorexia and hypoalbuminemia), especially when associated with high grade tumors, should be considered for clinical trials of adjuvant therapies.

Catabolic mediators as targets for cancer cachexia

The cachexia syndrome, characterized by a marked weight loss, anorexia, asthenia and anaemia, is invariably associated with the growth of a tumour and leads to a malnutrition status caused by the induction of anorexia or decreased food intake. In addition, the competition for nutrients between the tumour and the host results in an accelerated catabolism state, which promotes severe metabolic disturbances in the patient. The search for the cachectic factor(s) started a long time ago, and many scientific and economic efforts have been devoted to its discovery, but we are still a long way from a complete answer. The present review aims to evaluate the different molecular mechanisms and catabolic mediators (both humoural and tumoural) that are involved in cancer cachexia and to discuss their potential as targets for future clinical investigations.

Cytokines in the pathogenesis of cancer cachexia

PURPOSE OF REVIEW

The aim of the present review is to summarize and update the role of different cytokines in the pathogenesis of cancer cachexia and to provide therapeutic strategies based on cytokine action.

RECENT FINDINGS

Cancer cachexia is a syndrome characterized by a marked weight loss, anorexia, asthenia and anemia. The cachectic state is invariably associated with the presence and growth of the tumor and leads to a malnutrition status due to the induction of anorexia or decreased food intake. In addition, the competition for nutrients between the tumor and the host leads to an accelerated starvation state which promotes severe metabolic disturbances in the host, including hypermetabolism, which leads to an increased energetic inefficiency. Different cytokines are clearly implicated in this process, possibly being responsible for anorexia, hypermetabolism and many other metabolic abnormalities, such as muscle proteolysis and apoptosis.

SUMMARY

Although the search for the cachectic factor(s) started a long time ago, and although many scientific and economic efforts have been devoted to its discovery, we are still a long way from knowing the whole truth. A lot of progress has been made, however, in understanding the role of different cytokines - tumor necrosis factor and IL-6 in particular - in muscle wasting associated with cancer cachexia, perhaps the most paradigmatic feature of this complex syndrome.

Impaired voltage-gated K+ channel expression in brain during experimental cancer cachexia

Cancer-induced cachexia affects most advanced cancer patients. It is characterized by anorexia, profound metabolic dysfunctions, and severe neurological disorders. Here we show that voltage-gated potassium channel (Kv) expression is impaired in the brain of tumor-bearing animals. Expression of both delayed rectifier (Kv1.1, Kv1.2, Kv1.3, Kv1.5, Kv1.6, Kv2.1, Kv3.1, Kv4.2) and A-type potassium channels (Kv1.4, Kv3.3, Kv3.4) was greatly down-regulated in brain from animals bearing a Yoshida AH-130 ascites hepatoma. The possible compensatory mechanisms (Kv1.4/Kv4.2), expression of redundant genes (Kv3.1/Kv3.3) and heteromultimeric channel formation (Kv2.1/Kv9.3) were also affected. The high circulating levels of TNFalpha and the reduced expression of the anti-apoptotic protein Bcl-XL found in the brain of tumor-bearing animals indicate that this response could be mediated by an increase in brain cell death due to apoptosis. The results suggest that brain function is impaired during cancer cachexia, and may account for the cancer-induced anorectic response and other neurological alterations.

Brain cytokines and disease

Cytokines (e.g. various interleukins and subfamily members, tumor necrosis factors, interferons, chemokines and growth factors) act in the brain as immunoregulators and neuromodulators. Over a decade ago, the integrative article 'Immunoregulators in the Nervous System' (Neurosci Biobehav Rev 1991; 15: 185-215) provided a comprehensive framework of pivotal issues on cytokines and the nervous system that recently have been extensively studied. Cytokine profiles in the brain, including cytokine generation and action, have been studied in multiple models associated with neuropathophysiological conditions. These include: (1) acute conditions and disorders such as stroke (cerebral ischemia or infarction and intracranial hemorrhage), traumatic brain injury, spinal cord injury and acute neuropathies; (2) chronic neurodegenerative disorders and chronic conditions, including Alzheimer's disease, Parkinson's disease, neuropathic pain, epilepsy and chronic neuropathies; (3) brain infections, including bacterial meningitis and encephalitis; (4) brain tumors; (5) neuroimmunological disorders per se, such as multiple sclerosis; (5) psychiatric disorders, including schizophrenia and depression; (6) neurological and neuropsychiatric manifestations associated with non- central nervous system (CNS) disorders such as peripheral cancer, liver, kidney and metabolic compromise, and peripheral infectious and inflammatory conditions; and (7) cytokine immunotherapy, which can be accompanied by neuropsychiatric manifestations when administered either via peripheral or brain routes. Cytokine profiles have also been studied in multiple animal models challenged with inflammatory, infectious, chemical, malignant and stressor insults. Essentially data show that cytokines play a pivotal role in multiple neuropathophysiological processes associated with different types of disorders and insults. Cytokine expression and action in the brain shows a different profile across conditions, but some similarities exist. Under a defined temporal sequence, cytokine involvement in neuroprotection or the induction of a deleterious pathophysiological cascade and in resolution/healing is proposed depending on the type of cytokine. In the brain, functional interactions among cytokines, balance between pro-inflammatory and anti-inflammatory cytokines and functional interactions with neurotransmitters and neuropeptides play a pivotal role in the overall cytokine profile, pattern of neuropathophysiological cascades, and quality and magnitude of neuropsychiatric manifestations. In this brief review various selected cytokine-related issues with relevance to the brain are discussed.