Experimental Models Of Cancer Cachexia Research Articles

Nutritional Interventions in Cancer Cachexia: Evidence and Perspectives From Experimental Models.

Cancer cachexia is a complex metabolic syndrome characterized by involuntary skeletal muscle loss and is associated with poor clinical outcome, decreased survival and negatively influences cancer therapy. No curative treatments are available for cancer cachexia, but nutritional intervention is recommended as a cornerstone of multimodal therapy. Optimal nutritional care is pivotal in the treatment of cancer cachexia, and the effects of nutrients may extend beyond provision of adequate energy uptake, targeting different mechanisms or metabolic pathways that are affected or deregulated by cachexia. The evidence to support this notion derived from nutritional intervention studies in experimental models of cancer cachexia is systematically discussed in this review. Moreover, experimental variables and readout parameters to determine skeletal muscle wasting and cachexia are methodologically evaluated to allow critical comparison of similar studies. Single- and multinutrient intervention studies including qualitative modulation of dietary protein, dietary fat, and supplementation with specific nutrients, such as carnitine and creatine, were reviewed for their efficacy to counteract muscle mass loss and its underlying mechanisms in experimental cancer cachexia. Numerous studies showed favorable effects on impaired protein turnover and related metabolic abnormalities of nutritional supplementation in parallel with a beneficial impact on cancer-induced muscle wasting. The combination of high quality nutrients in a multitargeted, multinutrient approach appears specifically promising, preferentially as a multimodal intervention, although more studies investigating the optimal quantity and combination of nutrients are needed. During the review process, a wide variation in timing, duration, dosing, and route of supplementation, as well as a wide variation in animal models were observed. Better standardization in dietary design, and the development of experimental models that better recapitulate the etiology of human cachexia, will further facilitate successful translation of experimentally-based multinutrient, multimodal interventions into clinical practice.

Increased tumour burden alters skeletal muscle properties in the KPC mouse model of pancreatic cancer.

Cancer cachexia is a multifactorial wasting syndrome that is characterized by the loss of skeletal muscle mass and weakness, which compromises physical function, reduces quality of life, and ultimately can lead to mortality. Experimental models of cancer cachexia have recapitulated this skeletal muscle atrophy and consequent decline in muscle force generating capacity. We address these issues in a novel transgenic mouse model Kras, Trp53 and Pdx-1-Cre (KPC) of pancreatic ductal adenocarcinoma (PDA) using multi-parametric magnetic resonance (mp-MR) measures. KPC mice (n = 10) were divided equally into two groups (n = 5/group) depending on the size of the tumor i.e. tumor size <250 mm3 and >250 mm3. Using mp-MR measures, we demonstrated the changes in the gastrocnemius muscle at the microstructural level. In addition, we evaluated skeletal muscle contractile function in KPC mice using an in vivo approach. Increase in tumor size resulted in decrease in gastrocnemius maximum cross sectional area, decrease in T2 relaxation time, increase in magnetization transfer ratio, decrease in mean diffusivity, and decrease in radial diffusivity of water across the muscle fibers. Finally, we detected significant decrease in absolute and specific force production of gastrocnemius muscle with increase in tumor size. Our findings indicate that increase in tumor size may cause alterations in structural and functional parameters of skeletal muscles and that MR parameters may be used as sensitive biomarkers to noninvasively detect structural changes in cachectic muscles.

The role of vitamin D in cancer cachexia.

The possibility to use vitamin D supplementation to improve muscle wasting, with particular focus on cancer cachexia, is discussed. Vitamin D exerts biological actions on myogenic precursor proliferation and differentiation, impinging on muscle regeneration. However, the effects of VitD supplementation in diseases associated with muscle atrophy, such as cancer cachexia, are poorly investigated. Data obtained in experimental models of cancer cachexia show that the administration of vitamin D to tumor-bearing animals is not able to prevent or delay both muscle wasting and adipose tissue depletion, despite increased expression of muscle vitamin D receptor. Not just vitamin D supplementation impairs muscle damage-induced regeneration, suggesting that upregulation of vitamin D receptor signaling could contribute to muscle wasting. Vitamin D supplementation is likely beneficial to reduce or delay aging-related sarcopenia and osteoporosis, although the available data still put in evidence significant discrepancies. By contrast, VitD supplementation to tumor-bearing animals or to rats with arthritis was shown to be totally ineffective. In this regard, the adoption of VitD treatment in patients with cancer cachexia or other chronic diseases should be carefully evaluated, in particular whenever a regenerative process might be involved.

Interference with Ca2+-Dependent Proteolysis Does Not Alter the Course of Muscle Wasting in Experimental Cancer Cachexia.

Protein hypercatabolism significantly contributes to the onset and progression of muscle wasting in cancer cachexia. In this regard, a major role is played by the ATP-ubiquitin-proteasome-dependent pathway and by autophagy. However, little is known about the relevance of the Ca2+-dependent proteolytic system. Since previous results suggested that this pathway is activated in the skeletal muscle of tumor hosts, the present study was aimed to investigate whether inhibition of Ca2+-dependent proteases (calpains) may improve cancer-induced muscle wasting. Two experimental models of cancer cachexia were used, namely the AH-130 Yoshida hepatoma and the C26 colon carcinoma. The Ca2+-dependent proteolytic system was inhibited by treating the animals with dantrolene or by overexpressing in the muscle calpastatin, the physiologic inhibitor of Ca2+-dependent proteases. The results confirm that calpain-1 is overexpressed and calpastatin is reduced in the muscle of rats implanted with the AH-130 hepatoma, and show for the first time that the Ca2+-dependent proteolytic system is overactivated also in the C26-bearing mice. Yet, administration of dantrolene, an inhibitor of the Ca2+-dependent proteases, did not modify tumor-induced body weight loss and muscle wasting in the AH-130 hosts. Dantrolene was also unable to reduce the enhancement of protein degradation rates occurring in rats bearing the AH-130 hepatoma. Similarly, overexpression of calpastatin in the tibialis muscle of the C26 hosts did not improve muscle wasting at all. These observations suggest that inhibiting a single proteolytic system is not a good strategy to contrast cancer-induced muscle wasting. In this regard, a more general and integrated approach aimed at targeting the catabolic stimuli rather than the proteolytic activity of a single pathway would likely be the most appropriate therapeutic intervention.

Comparison of the anticatabolic effects of leucine and Ca-β-hydroxy-β-methylbutyrate in experimental models of cancer cachexia

ObjectiveLoss of skeletal muscle is the most debilitating feature of cancer cachexia, and there are few treatments available. The aim of this study was to compare the anticatabolic efficacy of L-leucine and the leucine metabolite β-hydroxy-β-methylbutyrate (Ca-HMB) on muscle protein metabolism, both in vitro and in vivo. MethodsStudies were conducted in mice bearing the cachexia-inducing murine adenocarcinoma 16 tumor, and in murine C2 C12 myotubes exposed to proteolysis-inducing factor, lipopolysaccharide, and angiotensin II. ResultsBoth leucine and HMB were found to attenuate the increase in protein degradation and the decrease in protein synthesis in murine myotubes induced by proteolysis-inducing factor, lipopolysaccharide, and angiotensin II. However, HMB was more potent than leucine, because HMB at 50 μM produced essentially the same effect as leucine at 1 mM. Both leucine and HMB reduced the activity of the ubiquitin-proteasome pathway as measured by the functional (chymotrypsin-like) enzyme activity of the proteasome in muscle lysates, as well as Western blot quantitation of protein levels of the structural/enzymatic proteasome subunits (20 S and 19 S) and the ubiquitin ligases (MuRF1 and MAFbx). In vivo studies in mice bearing the murine adenocarcinoma 16 tumor showed a low dose of Ca-HMB (0.25 g/kg) to be 60% more effective than leucine (1 g/kg) in attenuating loss of body weight over a 4-d period. ConclusionThese results favor the clinical feasibility of using Ca-HMB over high doses of leucine for the treatment of cancer cachexia.

Abstract A6: The ES-2 ovarian cancer causes muscle wasting in vitro and in vivo: A novel experimental model of cancer cachexia

Abstract Cancer cachexia is a devastating consequence of cancer. A multifactorial syndrome characterized by skeletal muscle and adipose tissue wasting, cachexia cannot be fully reversed by nutritional support. Cachexia occurs in up to one half of all cancer patients and correlates with poor performance status, reduced quality of life and high mortality. Cachexia results both from the tumor-host interaction, as well as from the anti-cancer therapies. The only cure for cachexia is definitive removal of the tumor. In ovarian cancer, cachexia is associated with malnutrition and a general inflammatory state, characterized by high levels of pro-inflammatory cytokines (such as IL-6, TNF) in ascites and blood. Due to the absence of proper experimental models, cachexia also represents a generally understudied aspect of ovarian cancer that deserves more attention. In order to establish novel experimental models for the study of ovarian cancer cachexia, we tested several human ovarian cancer cell lines with different degrees of differentiation for their capability to induce cachexia in vivo and muscle wasting in vitro. In a xenograft model, female Nu/Nu athymic nude mice were injected i.p. with 10x106 OVCAR-3, SK-OV-3 and ES-2 human ovarian cancer cells to mimic disseminated abdominal disease. After 60 days, the OVCAR-3 and SK-OV-3 cell lines did not result in detectable tumors. In contrast, beginning 8 days after inoculation, ES-2 cells caused severe cachexia with marked loss of body weight and with massive ascites accumulation in the peritoneal cavity. Within the ascites, ES-2 cells were not shown to aggregate, but existed more as a single-cell suspension or very small cell clumps. Some ES-2 cells also disseminated and infiltrated the pancreas, diaphragm and other organs, forming multiple solid tumors of histology consistent with clear cell carcinoma, characterized by sheets of cells with irregularly shaped nuclei and abundant cytoplasm. Muscles, including tibialis, gastrocnemius, quadriceps and heart, of tumor-bearing mice appeared markedly smaller than normal controls (~-20% vs. control; p&amp;lt;0.01). Muscle loss was due to fiber atrophy, as observed by reduced tibialis myofiber area. Fat pads and spleen were reduced in size, while the liver was unchanged. Piximus imaging revealed decreased bone mineral density (-16% vs. control; p&amp;lt;0.05). Consistent with reports in human ovarian cancer cachexia, IL-6 levels were markedly elevated in both blood and ascites. In quadriceps muscle, cachexia was also associated with high levels of phosphorylated STAT3 (pSTAT3), whose causal role in tumor-associated muscle wasting was previously reported in our laboratory. In order to understand whether tumor-derived factors were directly responsible for the wasting effects observed in vivo, differentiated C2C12 murine myotubes were exposed to conditioned medium from ES-2 cell cultures and evaluated for effects on myotube size. After 48 hours, the average diameter of C2C12 myofibers was severely reduced (-28% vs. control; p&amp;lt;0.001). These effects were evident at a low concentration of supernatant and were associated with elevated pSTAT3 levels. In conclusion, here we report that ES-2 tumor cells directly induce muscle atrophy, both in vitro and in vivo. Thus this is a new experimental model for the study of ovarian cancer cachexia. This model and future similar models will aid in identifying novel molecular mediators that could be effectively targeted in order to improve muscle wasting associated with ovarian cancer. Citation Format: Andrea Bonetto, Melissa J. Puppa, James A. Carson, Teresa A. Zimmers. The ES-2 ovarian cancer causes muscle wasting in vitro and in vivo: A novel experimental model of cancer cachexia. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research: From Concept to Clinic; Sep 18-21, 2013; Miami, FL. Philadelphia (PA): AACR; Clin Cancer Res 2013;19(19 Suppl):Abstract nr A6.

Nuclear transcription factor κ B activation and protein turnover adaptations in skeletal muscle of patients with progressive stages of lung cancer cachexia

Experimental models of cancer cachexia have indicated that systemic inflammation induces muscle-protein breakdown and wasting via muscular nuclear transcription factor κB (NF-κB) activation. This process may limit the efficacy of nutritional intervention. We assessed muscle NF-κB activity and protein turnover signaling in progressive stages of clinical lung cancer cachexia and assessed whether circulating factors can induce muscular NF-κB activity. Patients with lung cancer precachexia (n = 10) and cachexia (n = 16) were cross-sectionally compared with 22 healthy control subjects. mRNA transcripts of muscle proteolytic (ubiquitin proteasome system and autophagy lysosomal pathway) and myogenic markers and protein expression of PI3K/Akt, myostatin, and autophagy signaling were measured. A multiplex analysis showed the systemic inflammatory status, whereas plasma exposure to stable NF-κB-luciferase-reporter muscle cells revealed NF-κB inducibility. Compared with healthy control subjects, cachectic patients had reduced (appendicular) muscle mass (-10%), muscle fiber atrophy (-27%), and decreased quadriceps strength (-31%). Subtle alterations in the muscle morphology were also detectable in precachectic patients, without changes in body composition. Despite increased Akt phosphorylation, downstream phosphosubstrates glycogen synthase kinase 3β, mammalian target of rapamycin, and Forkhead box protein were unaltered. The expression of autophagy effectors B cell lymphoma 2/adenovirus E1B 19-kDa protein-interacting protein 3 and microtubule-associated proteins 1A/1B light chain 3B gradually increased from precachectic to cachectic patients, without differences in E3 ubiquitin ligases. Systemic and local inflammation was evident in cachexia and intermediate in precachexia, but the plasma of both patients groups caused ex vivo muscle NF-κB activation. In lung cancer, muscular NF-κB activity is induced by factors contained within the circulation. Autophagy may contribute to increased muscle proteolysis in lung cancer cachexia, whereas the absence of downstream changes in phosphosubstrates despite increased Akt phosphorylation suggests impaired anabolic signaling that may require targeted nutritional intervention.

Cancer cachexia decreases specific force and accelerates fatigue in limb muscle

Cancer cachexia is a complex metabolic syndrome that is characterized by the loss of skeletal muscle mass and weakness, which compromises physical function, reduces quality of life, and ultimately can lead to mortality. Experimental models of cancer cachexia have recapitulated this skeletal muscle atrophy and consequent decline in muscle force generating capacity. However, more recently, we provided evidence that during severe cancer cachexia muscle weakness in the diaphragm muscle cannot be entirely accounted for by the muscle atrophy. This indicates that muscle weakness is not just a consequence of muscle atrophy but that there is also significant contractile dysfunction. The current study aimed to determine whether contractile dysfunction is also present in limb muscles during severe Colon-26 (C26) carcinoma cachexia by studying the glycolytic extensor digitorum longus (EDL) muscle and the oxidative soleus muscle, which has an activity pattern that more closely resembles the diaphragm. Severe C-26 cancer cachexia caused significant muscle fiber atrophy and a reduction in maximum absolute force in both the EDL and soleus muscles. However, normalization to muscle cross sectional area further demonstrated a 13% decrease in maximum isometric specific force in the EDL and an even greater decrease (17%) in maximum isometric specific force in the soleus. Time to peak tension and half relaxation time were also significantly slowed in both the EDL and the solei from C-26 mice compared to controls. Since, in addition to postural control, the oxidative soleus is also important for normal locomotion, we further performed a fatigue trial in the soleus and found that the decrease in relative force was greater and more rapid in solei from C-26 mice compared to controls. These data demonstrate that severe cancer cachexia causes profound muscle weakness that is not entirely explained by the muscle atrophy. In addition, cancer cachexia decreases the fatigue resistance of the soleus muscle, a postural muscle typically resistant to fatigue. Thus, specifically targeting contractile dysfunction represents an additional means to counter muscle weakness in cancer cachexia, in addition to targeting the prevention of muscle atrophy.

Changes in Myostatin Signaling in Non-Weight-Losing Cancer Patients

Myostatin is a negative regulator of skeletal muscle mass. We recently demonstrated that myostatin expression is upregulated in an experimental model of cancer cachexia, suggesting that modulations of this pathway might play a pathogenic role in cancer-related muscle wasting. The present study was designed to investigate whether myostatin signaling is modulated in the muscle of non-weight-losing (nWL) patients with lung and gastric cancer. Myostatin signaling was studied in muscle biopsies obtained during surgical procedure from nWL patients affected by gastric (n=16) or lung (n=17) cancer. Western blotting was applied to test both the total expression of myostatin and the expression of phosphorylated form of GSK-3beta and Smad2/3. In patients with gastric cancer, the expression of both myostatin and phosphorylated GSK-3beta (p-GSK3β) were significantly increased. By contrast, in patients with lung cancer, myostatin levels were comparable to controls, whereas the expression of p-GSK3β significantly decreased in patients with disease stage III/IV. Myostatin signaling is altered in nWL cancer patients. Different tumor types may give rise to different patterns of molecular changes within the muscle, which occur even before cachexia becomes clinically apparent.

Molecular, cellular and physiological characterization of the cancer cachexia-inducing C26 colon carcinoma in mouse.

BackgroundThe majority of cancer patients experience dramatic weight loss, due to cachexia and consisting of skeletal muscle and fat tissue wasting. Cachexia is a negative prognostic factor, interferes with therapy and worsens the patients' quality of life by affecting muscle function. Mice bearing ectopically-implanted C26 colon carcinoma are widely used as an experimental model of cancer cachexia. As part of the search for novel clinical and basic research applications for this experimental model, we characterized novel cellular and molecular features of C26-bearing mice.MethodsA fragment of C26 tumor was subcutaneously grafted in isogenic BALB/c mice. The mass growth and proliferation rate of the tumor were analyzed. Histological and cytofluorometric analyses were used to assess cell death, ploidy and differentiation of the tumor cells. The main features of skeletal muscle atrophy, which were highlighted by immunohistochemical and electron microscopy analyses, correlated with biochemical alterations. Muscle force and resistance to fatigue were measured and analyzed as major functional deficits of the cachectic musculature.ResultsWe found that the C26 tumor, ectopically implanted in mice, is an undifferentiated carcinoma, which should be referred to as such and not as adenocarcinoma, a common misconception. The C26 tumor displays aneuploidy and histological features typical of transformed cells, incorporates BrdU and induces severe weight loss in the host, which is largely caused by muscle wasting. The latter appears to be due to proteasome-mediated protein degradation, which disrupts the sarcomeric structure and muscle fiber-extracellular matrix interactions. A pivotal functional deficit of cachectic muscle consists in increased fatigability, while the reported loss of tetanic force is not statistically significant following normalization for decreased muscle fiber size.ConclusionsWe conclude, on the basis of the definition of cachexia, that ectopically-implanted C26 carcinoma represents a well standardized experimental model for research on cancer cachexia. We wish to point out that scientists using the C26 model to study cancer and those using the same model to study cachexia may be unaware of each other's works because they use different keywords; we present strategies to eliminate this gap and discuss the benefits of such an exchange of knowledge.

Abstract 4172: Multi-parametric characterization of an experimental model of cancer cachexia

Abstract Cachexia is a complex syndrome that is characterized by a massive loss of adipose tissue and skeletal mass. It is encountered in up to 50% of cancer patients and accounts for more than 20% of cancer related deaths. Currently, there is no known cure for cachexia, since mechanisms underlying its manifestation are not defined clearly enough to design effective therapeutic strategies. Here we have used magnetic resonance imaging (MRI) to characterize the vascular properties of cachectic vs. non-cachectic tumors. We have also analyzed the glucose metabolism of these tumors by using [18F]fluorodeoxyglucose (FDG) with positron emission tomography (PET). These studies will provide further insight into the cachectic phenotype that can be used to design treatments to arrest or reverse this condition. We used cachectic (MAC16) and non-cachectic (MAC13) murine colon adenocarcinoma tumors. The cell lines, originally from Dr. Tisdale's laboratory, were obtained from Dr. Sidransky with Dr. Tisdale's permission. Approximately 2 × 106 cells were inoculated in the flank of male SCID mice. MRI studies were performed on a 4.7T Bruker Avance spectrometer. Mice were anesthetized with an i.p. injection of ketamine and acepromazine. For vascular imaging, the tail vein was catheterized before placing the animal in the spectrometer. Multislice relaxation rate maps were obtained by a saturation recovery method combined with fast T1 SNAPSHOT-FLASH imaging. An M0 map with a recovery delay of 7 s was acquired from four 1 mm thick slices through the tumor followed by corresponding images obtained with three relaxation delays (100 ms, 500 ms, and 1 s). The T1 maps were obtained before i.v. injection of albumin-GdDTPA and repeated over a 21 minute period. For PET imaging, mice fasted overnight were injected with 0.2 mCi of FDG. At 60 min post injection, a 15 min static image was acquired over the tumors. Images were decay corrected and reconstructed using 2D OSEM. Cachectic MAC16 tumors induced extensive weight loss, unlike the non-cachectic MAC13 tumors. The difference in the weight of mice became significant within 2 weeks after inoculation. Mice with comparable tumor volumes were imaged 3 to 4 weeks after inoculation. While vascular volumes were not significantly different between the two groups, we did observe significantly lower permeability in the cachectic tumors. Consistent with the MRI data we found significantly lower levels of VEGF mRNA in quantitative-RT-PCR of tumor extracts of MAC16 tumors compared to MAC13 tumors but not in MAC16 cells compared to MAC13 cells. FDG PET imaging revealed increased glycolytic activity in a cachectic MAC16 tumor compared to a non-cachectic MAC13 tumor. These studies are part of our ongoing work to obtain a comprehensive characterization of the cachectic phenotype using noninvasive multi-modality imaging that will allow us to detect cancer-induced cachexia and identify new targets to prevent or reverse this condition. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4172.

Muscle myostatin signalling is enhanced in experimental cancer cachexia

Myostatin belongs to the transforming growth factor-beta superfamily and negatively regulates skeletal muscle mass. Its deletion induces muscle overgrowth, while, on the contrary, its overexpression or systemic administration cause muscle atrophy. The present study was aimed at investigating whether muscle depletion as occurring in an experimental model of cancer cachexia, the rat bearing the Yoshida AH-130 hepatoma, is associated with modulations of myostatin signalling and whether the cytokine tumour necrosis factor-alpha may be relevant in this regard. Protein levels of myostatin, follistatin (myostatin endogenous inhibitor) and the activin receptor type IIB have been evaluated in the gastrocnemius of tumour-bearing rats by Western blotting. Circulating myostatin and follistatin in tumour hosts were evaluated by immunoprecipitation, while the DNA-binding activity of the SMAD transcription factors was determined by electrophoretic-mobility shift assay. In day 4 tumour hosts muscle myostatin levels were comparable to controls, yet follistatin was reduced, and SMAD DNA-binding activity was enhanced. At day 7, both myostatin and follistatin increased in tumour bearers, while SMAD DNA-binding activity was unchanged. To investigate whether tumour necrosis factor-alpha contributed to induce such changes, rats were administered pentoxifylline, an inhibitor of tumour necrosis factor-alpha synthesis that partially corrects muscle depletion in tumour-bearing rats. The drug reduced both myostatin expression and SMAD DNA-binding activity in day 4 tumour hosts and up-regulated follistatin at day 7. These observations suggest that myostatin pathway should be regarded as a potential therapeutic target in cancer cachexia.

Cancer cachexia: drugs in the patent literature

Background: The therapeutic approach to the neoplastic patient with cachexia is very frustrating for the physician. Indeed, we can say that a cure for cancer cachexia does not exist. Numerous therapeutic strategies have been tested in the last few decades with discouraging or at least conflicting results. Methods: Drugs patented for the treatment of cancer cachexia are evaluated and discussed. Results: New drugs such as ghrelin splice variant, small-molecule melanocortin-4 receptor antagonists and selective androgen receptor modulators have been discovered, evaluated with promising results, and patented. It is expected that soon they will be tested in humans through adequate clinical trials in experimental studies. Other compounds such as retinoid X receptor agonists, the inhibitor of LPS-induced TNF-α factor (LIPAF) protein, novel inhibitors of TNF-α production or release and tumour cytotoxic factor II need to be tested first in experimental models of cancer cachexia. Conclusion: With the recent discovery of new, effective drugs, it seems that a new scenario is opening up in the therapy of cancer cachexia.

Skeletal Muscle in Cancer Cachexia: The Ideal Target of Drug Therapy

Cancer cachexia is a debilitating and life-threatening syndrome that accounts for at least 20% of deaths in neoplastic patients. Cancer cachexia significantly impairs quality of life and response to anti-neoplastic therapies, increasing morbidity and mortality of cancer patients. The loss of lean body mass is the main characteristic of cancer cachexia and the principal cause of function impairment, fatigue and respiratory complications. It is the result of an imbalance between protein synthesis and protein degradation, the mechanisms underlying such alteration being multiple and partially known. Current therapy of cancer cachexia continues to be extremely poor. However, in the last decade, the attention has focused just on the skeletal muscle, as a potential target of therapy, with the aim to discover drugs capable to inhibit the catabolic processes and to stimulate the anabolic pathways. The skeletal muscle has been faced at different levels such as the mediators (cytokines and tumor-derived factors), the receptors (TNF-alpha and androgen receptors), the proteolytic pathways (calpains and ubiquitin-proteasome), the intracellullar signalling pathways (NF-kB, AP-1, FOXO, PKR), and the negative modulators of muscle growth/hypertrophy (myostatin, GSK3-beta). Most of the drugs that have been tested have shown to be effective, at least in experimental models of cancer cachexia. It remains to define their safety, tolerance and efficacy in humans through large, adequate, clinical trials. However, the impression is that there is a light at the back of the tunnel.

Effects of simvastatin administration in an experimental model of cancer cachexia

Objective We evaluated whether statins, in view of their anti-inflammatory properties, may effectively prevent the onset or modulate the severity of muscle wasting during cancer cachexia. Methods Simvastatin was administered to rats bearing the Yoshida AH-130 ascites hepatoma, a well-studied cytokine-dependent experimental model of cancer cachexia. Results Quite surprisingly, the drug negatively affected the wasting pattern induced by the AH-130 hepatoma. In fact, the administration of simvastatin to tumor hosts induced a further weight reduction of all the tissues examined except for the soleus, in the absence of significant effects of simvastatin on tumor growth or on food intake. No effects were observed after simvastatin administration in control animals, with the exception of a significant ( P < 0.05) reduction in heart weight. Conclusions Simvastatin administration, although capable of negatively modulating the inflammatory response, did not prevent muscle wasting in this experimental model of cancer cachexia. Moreover, the further muscle loss observed in simvastatin-treated tumor-bearing animals suggests that a note of caution should be introduced in treating cancer patients with statins in view of the possible occurrence of harmful side effects.

DNA Fragmentation Occurs in Skeletal Muscle during Tumor Growth: A Link with Cancer Cachexia?

In two different experimental models of cancer cachexia, the rat Yoshida AH-130 ascites hepatoma and the mouse Lewis lung carcinoma, the implantation of the tumor caused a loss of body weight which was associated with a reduction in the weight of different skeletal muscles, as well as with their protein content. The decrease in protein content was accompanied by a reduction in DNA content. Interestingly, the protein/DNA ratio was unchanged in the skeletal muscle of the tumor-bearing animals as compared with the non-tumor-bearing controls. Analysis of DNA fragmentation in skeletal muscle clearly showed enhanced laddering in the skeletal muscle of tumor-bearing animals, suggesting an apoptotic phenomenon. Interestingly, the degree of laddering (total DNA fragmented) increased with tumor burden. These results suggest that DNA fragmentation may be a primary event in cancer-associated cachexia.

Improvement by eicosanoids in cancer cachexia induced by LLC-IL6 transplantation.

Cachexia frequently occurs in the late stages of cancer, and is difficult to manage. We previously reported that interleukin-6 (IL-6) cDNA transfection into Lewis lung carcinoma (LLC-IL6) induced cachexia-like symptoms in C57BL/6 mice. This was thought to be a useful experimental model of cancer cachexia. We have examined the effects of two eicosanoids, docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), in order to evaluate whether they could relieve cachexia. LLC-IL6-bearing animals were divided into three treatment groups receiving DHA, EPA or water as the control; 80-microliter samples of these compounds (purity > 95%) were administered orally by catheter daily starting 7 days after tumor transplantation. Tumor growth curves were similar in the three groups. There were no differences in water or food intake in the three groups. However, body weight, a marker of cachexia, was significantly higher in treated mice than in the control group. Sixteen days after tumor transplantation, the mean body weight was 17.45 g (P < 0.05), 17.2 g and 16.41 g in the groups receiving DHA, EPA and water respectively. The eicosanoids did not affect serum levels of IL-6. Ubiquitination of muscle protein, a marker of proteolysis coupled to cachexia, was compared in LLC-IL6- and LLC-transplanted mice. The eicosanoids prevented the ubiquitination of approximately 180 kDa protein. These results suggest that eicosanoids may prevent the cachexia mediated by IL-6.

Cancer cachexia

Cancer cachexia has been listed as a major cause of death in cancer patients. In order to investigate the metabolic effects of the tumor on the host, we have evaluated an experimental model of cancer cachexia in the mouse (MAC16 colon adenocarcinoma), in which weight loss can reach 30-40% of initial weight with a tumor burden of only 2.5%, without a reduction in the intake of either food or water. The weight loss appears not to arise from tumor necrosis factor production, which is associated with a marked reduction in both food and water intake, but may be a result of catabolic factors produced by the tumor and present in the circulation. Both insulin and 3-hydroxybutyrate are effective inhibitors of the tumor catabolic factors in vitro and protect, to some extent, weight loss in vivo. However, whereas 3-hydroxybutyrate was associated with a reduction in tumor weight, insulin caused an enhancement, suggesting that the former may be more appropriate than the latter in the clinical treatment of cancer cachexia.

Effect of insulin on weight loss and tumour growth in a cachexia model.

A comparison has been made between the effects of daily insulin injection and a ketogenic diet on weight loss and tumour weight in an experimental model of cancer cachexia (MAC16). Weight loss associated with the MAC16 tumour was significantly reduced both by a ketogenic diet (80% MCT) and by daily insulin injections without an increase in either food or water consumption. Animals fed the 80% MCT diet had a significantly reduced tumour weight compared with controls fed a normal laboratory diet, while in animals administered 20 U insulin kg-1 day-1 the tumour weight was 50% greater than in saline infused controls. The stimulation of tumour growth by insulin was counteracted by the inclusion of 3-hydroxybutyrate in the drinking water without any alteration in the extent of weight loss. Depletion of both carcass fat and muscle dry weight in animals bearing the MAC16 tumour was reversed in animals administered either insulin or an 80% MCT diet. Animals bearing the MAC16 tumour had a reduced nitrogen balance compared with non-tumour-bearing controls, mainly due to excess urea excretion, and this was reversed towards control values in animals fed an 80% MCT diet, but not in animals administered insulin. These results suggest that a ketogenic diet is more effective than insulin administration in reversing the cachectic process and has the advantage of a concomitant reduction in tumour weight.