Mechanisms and treatment of cancer cachexia.

According to a recent consensus, cachexia is a complex metabolic syndrome associated with underlying illness and characterised by loss of muscle with or without loss of fat mass. The prominent clinical feature of cachexia is weight loss. Cachexia occurs in the majority of terminal cancer patients and it is responsible for the deaths of 22% of cancer patients. Although body weight is, indeed, an important factor to be taken into consideration in any cachexia treatment, body composition, physical performance and quality of life should be monitored. From the results presented here, one can speculate that a single therapy may not be completely successful in the treatment of cachexia. From this point of view, treatments involving different combinations are more likely to be successful. The objectives of any therapeutical combination are two: an anticatabolic aim directed towards both fat and muscle catabolism and an anabolic objective leading to the synthesis of macromolecules such as contractile proteins.

[Pathophysiology of neoplasic cachexia]. / Fisiopatología de la caquexia neoplásica.

The regulation of food intake is mediated by different psicological, gastrointestinal metabolic, nutritional and endocrine mechanisms. The cancer patient suffers from anorexia which results in early saciety and a reduction of appetite. Sometimes, the causes of the anorectic response are derived from the antitumoral treatment (chemotherapy, radiotherapy or immunotherapy), in some cases vomiting resulting in altered food intake. Alterations in the food taste and smell perception in addition to psychological dearrangements might also lead to the anorexia. Sometimes the tumour may play a direct effect when it is localised in either the hypothalamus or the digestive apparatus. However, in the majority of cases the origin of the anorexia associated with cancer cachexia seems to be due to the metabolic alterations induced by tumour burden. Different factors of both humoral and tumoral origin play a role in cancer anorexia. For instance, tumour necrosis factor (TNF-), a cytokine responsible for a great part of the metabolic alterations characteristic of cancer cachexia seems to be involved. In conclusion, the cancer anorexia seems to be more an effect than the cause of the weight loss and in fact the decrease in food intake might take place after weight loss is evident. In any case, the malnutrition associated with a decrease of food intake worsens the cachectic state, favouring a kind of a positive feed-back mechanism that finally leads to the patient's death.

Muscle wasting in cancer and ageing: cachexia versus sarcopenia.

Muscle wasting during cancer and ageing share many common metabolic pathways and mediators. Due to the size of the population involved, both cancer cachexia and ageing sarcopenia 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. 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 strategy for both prevention and treatment of wasting both in disease and during healthy ageing.

Skeletal muscle wasting in tumor-bearing rats is associated with MyoD down-regulation.

Cachexia is a syndrome characterized by profound skeletal muscle wasting that frequently complicates malignancies. A number of studies indicate that protein hypercatabolism, largely mediated by classical hormones and cytokines, is the major component of muscle depletion. Impaired regeneration has been suggested to contribute to the reduction of muscle size. In particular, it has been shown that the expression of MyoD, a muscle-specific transcription factor, is down-regulated by cytokines such as TNFalpha and IFNgamma in a NF-kappaB-dependent posttranscriptional manner. The present study investigated whether modulations of the transcription factor MyoD are associated with the onset of muscle wasting in a well established model of cancer cachexia. Rats bearing the Yoshida AH-130 hepatoma develop a condition of muscle protein hypercatabolism, largely dependent on TNFalpha bioactivity. In the gastrocnemius of these animals the expression of MyoD was markedly reduced, paralleling the decrease of muscle weight. This pattern is associated with increased nuclear translocation of AP-1, while DNA-binding assays did not detect any change in NF-kappaB activity. This is the first observation demonstrating that muscle depletion in tumor-bearing rats is associated with a down-regulation of MyoD levels. Although the underlying mechanisms remain to be clarified, this change is compatible with the hypothesis that a reduced expression of molecules involved in the regulation of the regenerative response may concur to muscle wasting in cancer cachexia.

Mice lacking TNFalpha receptors 1 and 2 are resistant to death and fulminant liver injury induced by agonistic anti-Fas antibody.

The liver is particularly susceptible to Fas-mediated cytotoxicity. Mice given an adequate parenteral dose of agonistic anti-Fas antibody (aFas) or of FasL are known to develop a devastating liver injury and to die in a few hours. The present work shows that mice lacking TNFR1 and TNFR2 (R(-)) both survive a single dose of aFas, otherwise rapidly lethal, and develop a mild form of hepatic damage, compared to the much more severe liver injury that in a few hours strikes wild-type mice (R(+)), eventually involving increased activity of proteases of different families (caspase 3-, 8-, and 9-like, calpains, cathepsin B). Neither the overall tissue levels of Fas and FasL nor Fas expression at the hepatocyte surface are altered in the liver of R(-) animals. The DNA-binding activity of the NF-kappaB transcription factor is enhanced after aFas treatment, but much more markedly in R(-) than in R(+) mice. Bcl2, while unchanged in untreated animals, is markedly upregulated in R(-) but not in R(+) mice challenged with aFas. The requirement of a normal TNFR1/TNFR2 phenotype for full deployment of the general and liver-specific aFas toxicity in mice most likely implies that treatment with aFas in some way results in activation of the TNFalpha-TNFRs system and that this activation synergizes with Fas-mediated signals in causing the fulminant liver injury and the animal death. The precise cellular and molecular details underlying this interplay between Fas- and TNFRs-mediated signaling systems in the general and liver-specific aFas toxicity largely remain to be clarified.

TNF-alpha is involved in activating DNA fragmentation in skeletal muscle.

Intraperitoneal administration of 100 microg kg(-1) (body weight) of tumour necrosis factor-alpha to rats for 8 consecutive days resulted in a significant decrease in protein content, which was concomitant with a reduction in DNA content. Interestingly, the protein/DNA ratio was unchanged in the skeletal muscle of the tumour necrosis factor-alpha-treated animals as compared with the non-treated controls. Analysis of muscle DNA fragmentation clearly showed enhanced laddering in the skeletal muscle of tumour necrosis factor-alpha-treated animals, suggesting an apoptotic phenomenon. In a different set of experiments, mice bearing a cachexia-inducing tumour (the Lewis lung carcinoma) showed an increase in muscle DNA fragmentation (9.8-fold) as compared with their non-tumour-bearing control counterparts as previously described. When gene-deficient mice for tumour necrosis factor-alpha receptor protein I were inoculated with Lewis lung carcinoma, they were also affected by DNA fragmentation; however the increase was only 2.1-fold. These results suggest that tumour necrosis factor-alpha partly mediates DNA fragmentation during experimental cancer-associated cachexia.

Hyperlipemia: a role in regulating UCP3 gene expression in skeletal muscle during cancer cachexia?

Rats bearing the Yoshida AH-130 ascites hepatoma showed an increased expression of both uncoupling protein-2 (UCP2) (two-fold) and UCP3 (three- to four-fold) in skeletal muscle (both soleus and gastrocnemius). The increase in mRNA content was associated with increased circulating concentrations of fatty acids (two-fold), triglyceride (two-fold) and cholesterol (1.9-fold). Administration of nicotinic acid to tumor-bearing rats abolishes the hyperlipidemic increase associated with tumor burden. The vitamin treatment also resulted in a decreased UCP3 gene expression in soleus muscle but not in gastrocnemius. It is concluded that circulating fatty acids may be involved in the regulation of UCP3 gene expression in aerobic muscles during experimental cancer cachexia. Since the UCP3 protein could have a role in energy expenditure, it may be suggested that hypolipidemic agents may have a beneficial role in the treatment of the cachectic syndrome.

Metabolic interrelationships between liver and skeletal muscle in pathological states.

The present review focuses on the metabolic interrelationships between liver and muscle in pathological states associated with catabolic conditions. Carbohydrate, fat and nitrogen metabolism between the parenchymal liver and skeletal muscle are considered and interrelated together with the possible mediators involved in pathological conditions.

Direct effects of tumor necrosis factor alpha (TNF-alpha) on murine skeletal muscle cell lines. Bimodal effects on protein metabolism.

Incubation of murine C2C12 myotubes with tumour necrosis factor-alpha (TNF-alpha) leads to significant changes in protein content and turnover, suggesting that the cytokine exerts direct effects in skeletal muscle. The effects of the cytokine on protein content show a clear bimodal behaviour. At low concentrations (1 U/ml or less), TNF-alpha decreases both total and myofibrillar protein content, while at relatively high concentrations (100 U/ml or more), the effects are opposite and TNF-alpha increases the total and myofibrillar protein content in C2C12 myotubes. The mechanisms responsible for this latter, unexpected anabolic effect of the cytokine on muscle cells are related to a 40% increase in the rate of protein synthesis and to a significant decrease (14%) in the rate of protein degradation. At high concentrations, TNF-alpha decreased the expression of the mRNA of components of both the ATP- (ubiquitin, E2, C8) and Ca2+-dependent (m-calpain) proteolytic systems. The effects of TNF-alpha (10 U/ml or higher) on protein content of cultured murine myotubes (differentiated myogenic cells) were similar to those induced by insulin (1 or 5 microg/ml), but the effects of TNF-alpha and those of insulin were not additive. Experiments using inhibitors of the signalling pathways mediated by PI3K and MAP kinases (MAPKs) ERK1/2 and p38 suggest that insulin and TNF-alpha may share some intracellular signalling pathways involving MAPKs in the enhanced protein accretion observed in the muscle cell cultures.

Hepatic transport of gluconeogenic substrates during tumor growth in the rat.

Hepatic gluconeogenic substrates (alanine, lactate, and glycerol) transport have been studied in liver plasma membrane vesicles from rats bearing the ascitic tumor Yoshida AH-130 hepatoma. Hepatic alanine uptake was increased in membrane vesicles from tumor-bearing animals as compared with those isolated from non-tumor-bearing controls. Although no changes were observed in relation with KM (2.19 and 2.10 mM for control and tumor groups, respectively), the presence of the tumor caused a clear increase in Vmax (3.07 and 5.04 nmol alanine/mg protein, respectively). The time course of lactate uptake showed no differences between the tumor-bearing animals and their corresponding controls. Both time course and kinetic experiments showed that liver glycerol uptake was due to passive diffusion and therefore cannot contribute to explain the enhanced utilization of this hepatic gluconeogenic substrate during tumor growth. The results suggest that hepatic alanine uptake may be an important factor accounting for its increased utilization for glucose synthesis in tumor-bearing rats.

Increased uncoupling protein-2 gene expression in brain of lipopolysaccharide-injected mice: role of tumour necrosis factor-alpha?

In order to understand the role of brain localized uncoupling proteins, we have examined the UCP2 and BMCP-1 gene expression in mice brain in two different catabolic states: administration of lipopolysaccharide (LPS) (2.5 mg/kg, i.p.) and tumour burden. Administration of LPS resulted in an increased UCP2 gene expression both in brain (208%) and cerebellum (77%). An increase in UCP2 gene expression was also observed after LPS treatment in double knockout mice for tumour necrosis factor-alpha (TNF) receptors 1 and 2 (75% in brain and 33% in cerebellum). Tumour growth also resulted in increased brain UCP2 gene expression (80%) in mice bearing the Lewis lung carcinoma as compared with the non-tumour-bearing controls. No changes were observed in BMCP-1 mRNA levels of either LPS-injected or tumour-bearing mice. From the results presented it may be suggested that: (a) the brain may contribute significantly to the increase in energy expenditure associated with hypermetabolic states such as fever and tumour burden, and (b) the regulation of UCP2 gene expression in brain does not seem to be influenced by TNF; therefore the action of other cytokines cannot be discarded.

Increased muscle ubiquitin mRNA levels in gastric cancer patients.

The intramuscular ATP-dependent ubiquitin (Ub)-proteasome proteolytic system is hyperactivated in experimental cancer cachexia. The present study aimed at verifying whether the expression of the muscle Ub mRNA is altered in patients with cancer. Total muscle RNA was extracted using the guanidinium isothiocyanate/phenol/chloroform method from rectus abdominis biopsies obtained intraoperatively from 20 gastric cancer (GC) patients and 10 subjects with benign abdominal diseases (CON) undergoing surgery. Ub mRNA levels were measured by northern blot analysis. Serum soluble tumor necrosis factor receptor (sTNFR) was measured by ELISA. Ub mRNA levels (arbitrary units, means +/- SD) were 2,345 +/- 195 in GC and 1,162 +/- 132 in CON (P = 0.0005). Ub mRNA levels directly correlated with disease stage (r = 0.608, P = 0.005), being 1,945 +/- 786 in stages I and II, 2,480 +/- 650 in stage III, and 3,799 +/- 66 in stage IV. Ub mRNA and sTNFR did not correlate with age and nutritional parameters. This study confirms experimental data indicating an overexpression of muscle Ub mRNA in cancer cachexia. Lack of correlation with nutritional status suggests that Ub activation in human cancer is an early feature that precedes any clinical sign of cachexia.

Curcumin, a natural product present in turmeric, decreases tumor growth but does not behave as an anticachectic compound in a rat model.

Systemic administration of curcumin [1,7-bis(4-hydroxy-3-methoxyphenil)1,6-heptadiene-3,5-dione] (20 microg/kg body weight) for 6 consecutive days to rats bearing the highly cachectic Yoshida AH-130 ascites hepatoma resulted in an important inhibition of tumor growth (31% of total cell number). Interestingly, curcumin was also able to reduce (24%) in vitro tumor cell content at concentrations as low as 0.5 microM without promoting any apoptotic events. Although systemic administration of curcumin has previously been shown to facilitate muscle regeneration, administration of the compound to tumor-bearing rats did not result in any changes in muscle wasting, when compared with the non-treated tumor-bearing animals. Indeed, both the weight and protein content of the gastrocnemius muscle significantly decreased as a result of tumor growth and curcumin was unable to reverse this tendency. It is concluded that curcumin, in spite of having clear antitumoral effects, has little potential as an anticachectic drug in the tumor model used in the present study.

Interleukin-15 mediates reciprocal regulation of adipose and muscle mass: a potential role in body weight control.

Interleukin (IL)-15 is a cytokine which is highly expressed in skeletal muscle. Cell culture studies have indicated that IL-15 may have an important role in muscle fiber growth and anabolism. However, data concerning the metabolic effects of this cytokine in vivo are lacking. In the present study, IL-15 was administered to adult rats for 7 days. While IL-15 did not cause changes in either muscle mass or muscle protein content, it induced significant changes in the fractional rates of both muscle protein synthesis and degradation, with no net changes in protein accumulation. Additionally, IL-15 administration resulted in a 33% decrease in white adipose tissue mass and a 20% decrease in circulating triacylglycerols; this was associated with a 47% lower hepatic lipogenic rate and a 36% lower plasma VLDL triacylglycerol content. The decrease in white fat induced by IL-15 was in adipose tissue. No changes were observed in the rate of lipolysis as a result of cytokine administration. These findings indicate that IL-15 has significant effects on both protein and lipid metabolism, and suggest that this cytokine may participate in reciprocal regulation of muscle and adipose tissue mass.

Insulin and cancer (Review).

Although the molecular mechanisms of insulin action on many physiological and biochemical processes are far from being completely understood, little doubt exists about the involvement of insulin in tumoural processes. Indeed, increased insulin production (either directly by the tumour in an ectopic fashion, or indirectly by stimulation of the pancreatic secretion) is a common phenomenon during cancer development. Paradoxically, the increased production and circulating levels of the hormone are associated with a decrease in sensitivity which leads to insulin resistance in the non-tumoural tissues, resulting in hyperlipaemia and profound alterations in carbohydrate and lipid metabolism. In addition to these effects on the host, insulin can actually increase the incidence of neoplasias and promote tumour growth. This is probably related to the signaling pathway of the hormone, which shares many elements with that of several growth factors. In addition, insulin signaling directly interacts with that of the ras oncogene. We review the involvement of insulin in cancer from a multidisciplinary point of view, with the aim of encouraging the design of future therapeutic options for cancer treatment.

Cancer cachexia: a therapeutic approach.

Cancer cachexia is a complex syndrome which occurs in more than two-thirds of patients who die with advanced cancer. The main components of this pathological state are anorexia and metabolic abnormalities such as glucose intolerance, fat depletion, and muscle protein catabolism among others. The aim of the present study is to review the different therapeutic approaches that have been designed to fight and counteract cancer cachexia.

The divergent effects of tumour necrosis factor-alpha on skeletal muscle: implications in wasting.

Tumour necrosis factor-alpha (TNF) is a pleiotropic cytokine that can have effects on many cell types, including skeletal muscle, the most abundant tissue (representing almost 45% of body weight), where many effects of this cytokine have been described. Thus, TNF receptors have been described in muscle tissue, and different investigations have revealed effects of the cytokine on membrane potential, glucose uptake and metabolism, amino acid transport and protein turnover. However, the results found are relatively divergent, therefore the main aim of the present review has been to clarify and reconcile some of the most contradictory studies concerning the effects of TNF on metabolism in skeletal muscle.

Short-term effects of leptin on skeletal muscle protein metabolism in the rat.

We have examined the short-term effects of leptin on protein metabolism in the rat. Indeed, an intravenous leptin administration (100 microg/kg body weight), which resulted in no changes in circulating insulin in the time interval studied, induced a decrease in the incorporation of (14)C-leucine to (14)C-skeletal muscle protein. No changes were observed in relation to muscle protein degradation (either measured in vivo following isotope preloading or in vitro as tyrosine released into the incubation medium) and gene expression associated with the different proteolytic systems (cathepsin B, m-calpain and ubiquitin-proteasome system). The effects of leptin on amino acid incorporation into muscle protein do not seem to be direct because incubation of isolated EDL muscles in the presence of 10 microg/ml of leptin did not modify either the protein incorporation or the oxidation of (14)C-leucine. It may, therefore, be suggested that leptin is able to influence protein synthesis in skeletal muscle through the action of an unknown mediator.

Interleukin-15 antagonizes muscle protein waste in tumour-bearing rats.

Tissue protein hypercatabolism (TPH) is an important feature in cancer cachexia, particularly with regard to the skeletal muscle. The Yoshida AH-130 rat ascites hepatoma is a model system for studying the mechanisms involved in the processes that lead to tissue depletion, since it induces in the host a rapid and progressive muscle wasting, primarily due to TPH. The present study was aimed at investigating if IL-15, which is known to favour muscle fibre hypertrophy, could antagonize the enhanced muscle protein breakdown in this cancer cachexia model. Indeed, IL-15 treatment partly inhibited skeletal muscle wasting in AH-130-bearing rats by decreasing (8-fold) protein degradative rates (as measured by 14C-bicarbonate pre-loading of muscle proteins) to values even lower than those observed in non-tumour-bearing animals. These alterations in protein breakdown rates were associated with an inhibition of the ATP-ubiquitin-dependent proteolytic pathway (35% and 41% for 2.4 and 1.2 kb ubiquitin mRNA, and 57% for the C8 proteasome subunit, respectively). The cytokine did not modify the plasma levels of corticosterone and insulin in the tumour hosts. The present data give new insights into the mechanisms by which IL-15 exerts its preventive effect on muscle protein wasting and seem to warrant the implementation of experimental protocols involving the use of the cytokine in the treatment of pathological states characterized by TPH, particularly in skeletal muscle, such as in the present model of cancer cachexia.

Branched-chain amino acids inhibit proteolysis in rat skeletal muscle: mechanisms involved.

Incubation of isolated rat soleus and EDL muscles in the presence of 10 mM leucine resulted in a decreased proteolytic rate as measured by the release of tyrosine into the incubation medium. The effect of this branched-chain amino acid (BCAA) is associated with a decreased activity of the lysosomal proteases and a decreased expression of the genes of the ATP-ubiquitin-dependent proteolysis (ubiquitin and C8). Incubation of muscles in the presence of actinomycin D revealed that the effects of the amino acid can be accounted for by an inhibition of the transcription rate. The presence of leucine did not influence the gene expression of other nonlysosomal (m-calpain) and lysosomal (cathepsin B) proteolytic systems. It is concluded that the well-known effect of BCAA on muscle proteolysis is mediated, in the short term, by the inhibition of lysosomal proteolysis. In a longer period, based on the inhibition of gene transcription observed, an involvement of the ATP-dependent proteolytic system is also likely to occur.