Animal models of the cancer anorexia–cachexia syndrome

Cell-death induced immune response and coagulopathy promote cachexia in Drosophila

Tumors can exert a far-reaching influence on the body, triggering systemic responses that contribute to debilitating conditions like cancer cachexia. To characterize the mechanisms underlying tumor-host interactions, we utilized a BioID-based proximity labeling method to identify proteins secreted by Ykiact adult Drosophila gut tumors into the bloodstream/hemolymph. Among the major proteins identified are coagulation and immune-responsive factors that contribute to the systemic wasting phenotypes associated with Ykiact tumors. The effect of innate immunity factors is mediated by NFκB transcription factors Relish, dorsal, and Dif, which in turn upregulate the expression of the cachectic factors Pvf1, Impl2, and Upd3. In addition, Ykiact tumors secrete Eiger, a TNF-alpha homolog, which activates the JNK signaling pathway in neighboring non-tumor cells, leading to cell death. The release of damage-associated molecular patterns (DAMPs) from these dying cells presumably amplifies the inflammatory response, exacerbating systemic wasting. Targeting the inflammatory response, the JNK pathway, or the production of cachectic factors could potentially alleviate the debilitating effects of cancer cachexia.

Cancer cachexia: multilevel metabolic dysfunction

Cancer cachexia is a complex metabolic disorder marked by unintentional body weight loss or 'wasting' of body mass, driven by multiple aetiological factors operating at various levels. It is associated with many malignancies and significantly contributes to cancer-related morbidity and mortality. With emerging recognition of cancer as a systemic disease, there is increasing awareness that understanding and treatment of cancer cachexia may represent a crucial cornerstone for improved management of cancer. Here, we describe the metabolic changes contributing to body wasting in cachexia and explain how the entangled action of both tumour-derived and host-amplified processes induces these metabolic changes. We discuss energy homeostasis and possible ways that the presence of a tumour interferes with or hijacks physiological energy conservation pathways. In that context, we highlight the role played by metabolic cross-talk mechanisms in cachexia pathogenesis. Lastly, we elaborate on the challenges and opportunities in the treatment of this devastating paraneoplastic phenomenon that arise from the complex and multifaceted metabolic cross-talk mechanisms and provide a status on current and emerging therapeutic approaches.

Early adipose tissue wasting in a novel preclinical model of human lung cancer cachexia

Cancer cachexia (CC), a syndrome of skeletal muscle and adipose tissue wasting, reduces responsiveness to therapies and increases mortality. There are no approved treatments for CC, which may relate to discordance between pre-clinical models and human CC. To address the need for clinically relevant models, we generated tamoxifen-inducible, epithelial cell specific Kras G12D/+ ( G12D ) mice. G12D mice develop CC over a protracted time course and phenocopy tissue, cellular, mutational, transcriptomic, and metabolic characteristics of human lung CC. CC in G12D mice is characterized by early loss of adipose tissue, a phenotype confirmed in a large cohort of patients with lung cancer. Tumor-released factors promote adipocyte lipolysis, a driver of adipose wasting in human CC, and adipose tissue wasting was inversely related to tumor burden. Thus, G12D mice model key features of human lung CC and suggest a novel role for early adipose tissue wasting in CC.

A comprehensive review of animal models for cancer cachexia: Implications for translational research

Cancer cachexia is a multifactorial syndrome characterized by progressive weight loss and a disease process that nutritional support cannot reverse. Although progress has been made in preclinical research, there is still a long way to go in translating research findings into clinical practice. One of the main reasons for this is that existing preclinical models do not fully replicate the conditions seen in clinical patients. Therefore, it is important to understand the characteristics of existing preclinical models of cancer cachexia and pay close attention to the latest developments in preclinical models. The main models of cancer cachexia used in current research are allogeneic and xenograft models, genetically engineered mouse models, chemotherapy drug-induced models, Chinese medicine spleen deficiency models, zebrafish and Drosophila models, and cellular models. This review aims to revisit and summarize the commonly used animal models of cancer cachexia by evaluating existing preclinical models, to provide tools and support for translational medicine research.

OBSERVE: guidelines for the refinement of rodent cancer models

Existing guidelines on the preparation (Planning Research and Experimental Procedures on Animals: Recommendations for Excellence (PREPARE)) and reporting (Animal Research: Reporting of In Vivo Experiments (ARRIVE)) of animal experiments do not provide a clear and standardized approach for refinement during in vivo cancer studies, resulting in the publication of generic methodological sections that poorly reflect the attempts made at accurately monitoring different pathologies. Compliance with the 3Rs guidelines has mainly focused on reduction and replacement; however, refinement has been harder to implement. The Oncology Best-practices: Signs, Endpoints and Refinements for in Vivo Experiments (OBSERVE) guidelines are the result of a European initiative supported by EurOPDX and INFRAFRONTIER, and aim to facilitate the refinement of studies using in vivo cancer models by offering robust and practical recommendations on approaches to research scientists and animal care staff. We listed cancer-specific clinical signs as a reference point and from there developed sets of guidelines for a wide variety of rodent models, including genetically engineered models and patient derived xenografts. In this Consensus Statement, we systematically and comprehensively address refinement and monitoring approaches during the design and execution of murine cancer studies. We elaborate on the appropriate preparation of tumor-initiating biologicals and the refinement of tumor-implantation methods. We describe the clinical signs to monitor associated with tumor growth, the appropriate follow-up of animals tailored to varying clinical signs and humane endpoints, and an overview of severity assessment in relation to clinical signs, implantation method and tumor characteristics. The guidelines provide oncology researchers clear and robust guidance for the refinement of in vivo cancer models.

AMPK as a mediator of tissue preservation: time for a shift in dogma?

Ground-breaking discoveries have established 5'-AMP-activated protein kinase (AMPK) as a central sensor of metabolic stress in cells and tissues. AMPK is activated through cellular starvation, exercise and drugs by either directly or indirectly affecting the intracellular AMP (or ADP) to ATP ratio. In turn, AMPK regulates multiple processes of cell metabolism, such as the maintenance of cellular ATP levels, via the regulation of fatty acid oxidation, glucose uptake, glycolysis, autophagy, mitochondrial biogenesis and degradation, and insulin sensitivity. Moreover, AMPK inhibits anabolic processes, such as lipogenesis and protein synthesis. These findings support the notion that AMPK is a crucial regulator of cell catabolism. However, studies have revealed that AMPK's role in cell homeostasis might not be as unidirectional as originally thought. This Review explores emerging evidence for AMPK as a promoter of cell survival and an enhancer of anabolic capacity in skeletal muscle and adipose tissue during catabolic crises. We discuss AMPK-activating interventions for tissue preservation during tissue wasting in cancer-associated cachexia and explore the clinical potential of AMPK activation in wasting conditions. Overall, we provide arguments that call for a shift in the current dogma of AMPK as a mere regulator of cell catabolism, concluding that AMPK has an unexpected role in tissue preservation.

Platelet status in cancer cachexia progression in ApcMin/+ mice

Cachexia, a complex wasting syndrome, significantly affects the quality of life and treatment options for cancer patients. Studies have reported a strong correlation between high platelet count and decreased survival in cachectic individuals. Therefore, this study aimed to investigate the immunopathogenesis of cancer cachexia using the ApcMin/+ mouse model of spontaneous colorectal cancer. The research focused on identifying cellular elements in the blood at different stages of cancer cachexia, assessing inflammatory markers and fibrogenic factors in the skeletal muscle, and studying the behavioral and metabolic phenotype of ApcMin/+ mice at the pre-cachectic and severely cachectic stages. Platelet measurements were also obtained from other animal models of cancer cachexia - Lewis Lung Carcinoma and Colon 26 adenocarcinoma. Our study revealed that platelet number is elevated prior to cachexia development in ApcMin/+ mice and can become activated during its progression. We also observed increased expression of TGFβ2, TGFβ3, and SMAD3 in the skeletal muscle of pre-cachectic ApcMin/+ mice. In severely cachectic mice, we observed an increase in Ly6g, CD206, and IL-10 mRNA. Meanwhile, IL-1β gene expression was elevated in the pre-cachectic stage. Our behavioral and metabolic phenotyping results indicate that pre-cachectic ApcMin/+ mice exhibit decreased physical activity. Additionally, we found an increase in anemia at pre-cachectic and severely cachectic stages. These findings highlight the altered platelet status during early and late stages of cachexia and provide a basis for further investigation of platelets in the field of cancer cachexia.

Dynamics of cachexia-associated inflammatory changes in the brain accompanying intra-abdominal fibrosarcoma growth in Wistar rats

Accumulated data indicate that inflammation affecting brain structures participates in the development of cancer-related cachexia. However, the mechanisms responsible for the induction and progression of cancer-related neuroinflammation are still not fully understood. Therefore, we studied the time-course of neuroinflammation in selected brain structures and cachexia development in tumor-bearing rats. After tumor cells inoculation, specifically on the 7th, 14th, 21st, and 28th day of tumor growth, we assessed the presence of cancer-associated cachexia in rats. Changes in gene expression of inflammatory factors were studied in selected regions of the hypothalamus, brain stem, and circumventricular organs. We showed that the initial stages of cancer growth (7th and 14th day after tumor cells inoculation), are not associated with cachexia, or increased expression of inflammatory molecules in the brain. Even when we did not detect cachexia in tumor-bearing rats by the 21st day of the experiment, the inflammatory brain reaction had already started, as we found elevated levels of interleukin 1 beta, interleukin 6, tumor necrosis factor alpha, and glial fibrillary acidic protein mRNA levels in the nucleus of the solitary tract. Furthermore, we found increased interleukin 1 beta expression in the locus coeruleus and higher allograft inflammatory factor 1 expression in the vascular organ of lamina terminalis. Ultimately, the most pronounced manifestations of tumor growth were present on the 28th day post-inoculation of tumor cells. In these animals, we detected cancer-related cachexia and significant increases in interleukin 1 beta expression in all brain areas studied. We also observed significantly decreased expression of the glial cell activation markers allograft inflammatory factor 1 and glial fibrillary acidic protein in most brain areas of cachectic rats. In addition, we showed increased expression of cluster of differentiation 163 and cyclooxygenase 2 mRNA in the hypothalamic paraventricular nucleus, A1/C1 neurons, and area postrema of cachectic rats. Our data indicate that cancer-related cachexia is associated with complex neuroinflammatory changes in the brain. These changes can be found in both hypothalamic as well as extrahypothalamic structures, while their extent and character depend on the stage of tumor growth.

The protective effect of cannabinoids against colorectal cancer cachexia through modulation of inflammation and immune responses

Cancer cachexia is a multifactorial disorder characterized by weight loss and muscle wasting, and there are currently no FDA-approved medications. In the present study, upregulation of six cytokines was observed in serum samples from patients with colorectal cancer (CRC) and in mouse models. A negative correlation between the levels of the six cytokines and body mass index in CRC patients was seen. Gene Ontology analysis revealed that these cytokines were involved in regulating T cell proliferation. The infiltration of CD8⁺ T cells was found to be associated with muscle atrophy in mice with CRC. Adoptive transfer of CD8⁺ T cells isolated from CRC mice resulted in muscle wasting in recipients. The Genotype-Tissue Expression database showed that negative correlations between the expression of cachexia markers and cannabinoid receptor 2 (CB2) in human skeletal muscle tissues. Pharmacological treatment with Δ⁹-tetrahydrocannabinol (Δ⁹-THC), a selective CB2 agonist or overexpression of CB2 attenuated CRC-associated muscle atrophy. In contrast, knockout of CB2 with a CRISPR/Cas9-based strategy or depletion of CD8⁺ T cells in CRC mice abolished the Δ⁹-THC-mediated effects. This study demonstrates that cannabinoids ameliorate CD8⁺ T cell infiltration in CRC-associated skeletal muscle atrophy via a CB2-mediated pathway. Serum levels of the six-cytokine signature might serve as a potential biomarker to detect the therapeutic effects of cannabinoids in CRC-associated cachexia.

Mycobiota and C-Type Lectin Receptors in Cancers: Know thy Neighbors

Numerous studies have demonstrated the importance of gut bacteria in the development of malignancy, while relatively little research has been done on gut mycobiota. As a part of the gut microbiome, the percentage of gut mycobiota is negligible compared to gut bacteria. However, the effect of gut fungi on human health and disease is significant. This review systematically summarizes the research progress on mycobiota, especially gut fungi, in patients with head and neck cancer (HNC), esophageal cancer (EC), gastric cancer (GC), colorectal cancer (CRC), hepatocellular carcinoma (HCC), pancreatic cancer, melanoma, breast cancer, and lung carcinoma-induced cachexia. Moreover, we also describe, for the first time in detail, the role of the fungal recognition receptors, C-type lectin receptors (CLRs) (Dectin-1, Dectin-2, Dectin-3, and Mincle) and their downstream effector caspase recruitment domain-containing protein 9 (CARD9), in tumors to provide a reference for further research on intestinal fungi in the diagnosis and treatment of malignant tumors.

Leucine Supplementation in Cancer Cachexia: Mechanisms and a Review of the Pre-Clinical Literature

Cancer cachexia (CC) is a complex syndrome of bodily wasting and progressive functional decline. Unlike starvation, cachexia cannot be reversed by increased energy intake alone. Nonetheless, targeted nutritional support is a necessary component in multimodal syndrome management. Due to the highly catabolic nature of cancer cachexia, amino acid supplementation has been proposed. Interestingly, leucine has been found to increase protein synthesis and decrease protein degradation via mTORC1 pathway activation. Multiple pre-clinical studies have explored the impact of leucine supplementation in cachectic tumor-bearing hosts. Here, we provide an overview of leucine’s proposed modes of action to preserve lean mass in cachexia and review the current pre-clinical literature related to leucine supplementation during CC. Current research indicates that a leucine-rich diet may attenuate CC symptomology; however, these works are difficult to compare due to methodological differences. There is need for further pre-clinical work exploring leucine’s potential ability to modulate protein turnover and immune response during CC, as well as the impact of additive leucine on tumor growth.

Cannabinoids orchestrate cross-talk between cancer cells and endothelial cells in colorectal cancer

Medical marijuana has been approved by the FDA for treating chemotherapy-induced nausea and vomiting. However, less is known about its direct effects on tumor cells and the tumor microenvironment. In this study, RNA-sequencing datasets in the NCBI GEO repository were first analyzed; upregulation of cannabinoid receptors was observed in both primary and metastatic colorectal cancer (CRC) tumor tissues. An increase of cannabinoid receptors was also found in patients with CRC, azoxymethane/dextran sulfate sodium-induced CRC and CRC metastatic mouse models. Δ⁹-Tetrahydrocannabinol (Δ⁹-THC)-induced tumor progression in both primary and metastatic mouse models and also increased angiogenesis. A human growth factor antibody array indicated that Δ⁹-THC promoted the secretion of angiogenic growth factors in CRC, leading to the induction of tube formation and migration in human-induced pluripotent stem cell-derived vascular endothelial cells. The nuclear translocation of STAT1 played important roles in Δ⁹-THC-induced angiogenesis and tumor progression. Pharmacological treatment with STAT1 antagonist or abrogation of STAT1 with CRISPR/Cas9-based strategy rescued those effects of Δ⁹-THC in CRC. This study demonstrates that marijuana might increase the risk of CRC progression and that inhibition of STAT1 is a potential strategy for attenuating these side effects.

An Oatp transporter-mediated steroid sink promotes tumor-induced cachexia in Drosophila

Cancer cachexia is associated with many types of tumors and is characterized by a combination of anorexia, loss of body weight, catabolic alterations, and systemic inflammation. We developed a tumor model in Drosophila larvae that causies cachexia-like syndrome, and we found that cachectic larvae show reduced levels of the circulating steroid ecdysone (Ec). Artificially importing Ec in the tumor through the use of the EcI/Oatp74D importer aggravated cachexia, whereas feeding animals with Ec rescued cachectic defects. This suggests that a steroid sink induced by the tumor promotes catabolic alterations in healthy tissues. We found that Oatp33Eb, a member of the Oatp transporter family, is specifically induced in tumors promoting cachexia. The overexpression of Oatp33Eb in noncachectic tumors induced cachexia, whereas its inhibition in cachectic tumors restored circulating Ec and reversed cachectic alterations. Oatp transporters are induced in several types of hormone-dependent tumors, and this result suggests that a similar sink effect could modify hormonal balance in cachectic cancer patients.

Physiologic and molecular characterization of a novel murine model of metastatic head and neck cancer cachexia

BACKGROUND

Cancer cachexia is a metabolic disorder characterized by the progressive loss of fat and lean mass that results in significant wasting, ultimately leading to reduced quality of life and increased mortality. Effective therapies for cachexia are lacking, potentially owing to the mismatch in clinically relevant models of cachexia. Specifically, cachexia observed in a clinical setting is commonly associated with advanced or late-stage cancers that are metastatic, yet pre-clinical metastatic models of cachexia are limited. Furthermore, the prevalence of cachexia in head and neck cancer patients is high, yet few pre-clinical models of head and neck cancer cachexia exist. In addition to these shortcomings, cachexia is also heterogeneous among any given cancer, whereas patients with similar disease burden may experience significantly different degrees of cachexia symptoms. In order to address these issues, we characterize a metastatic model of human papilloma virus (HPV) positive head and neck squamous cell carcinoma that recapitulates the cardinal clinical and molecular features of cancer cachexia.

METHODS

Male and female C57BL/6 mice were implanted subcutaneously with oropharyngeal squamous cell carcinoma cells stably transformed with HPV16 E6 and E7 together with hRas and luciferase (mEERL) that metastasizes to the lungs (MLM). We then robustly characterize the physiologic, behavioural, and molecular signatures during tumour development in two MLM subclones.

RESULTS

Mice injected with MLM tumour cells rapidly developed primary tumours and eventual metastatic lesions to the lungs. MLM3, but not MLM5, engrafted mice progressively lost fat and lean mass during tumour development despite the absence of anorexia (P < 0.05). Behaviourally, MLM3-implanted mice displayed decreased locomotor behaviours and impaired nest building (P < 0.05). Muscle catabolism programmes associated with cachexia, including E3 ubiquitin ligase and autophagy up-regulation, along with progressive adipose wasting and accompanying browning gene signatures, were observed. Tumour progression also corresponded with hypothalamic and peripheral organ inflammation, as well as an elevation in neutrophil-to-lymphocyte ratio (P < 0.05). Finally, we characterize the fat and lean mass sparing effects of voluntary wheel running on MLM3 cachexia (P < 0.05).

CONCLUSIONS

This syngeneic MLM3 allograft model of metastatic cancer cachexia is reliable, consistent, and readily recapitulates key clinical and molecular features and heterogeneity of cancer cachexia. Because few metastatic models of cachexia exist-even though cachexia often accompanies metastatic progression-we believe this model more accurately captures cancer cachexia observed in a clinical setting and thus is well suited for future mechanistic studies and pre-clinical therapy development for this crippling metabolic disorder.

Tumor-derived MMPs regulate cachexia in a Drosophila cancer model

Cachexia, the wasting syndrome commonly observed in advanced cancer patients, accounts for up to one-third of cancer-related mortalities. We have established a Drosophila larval model of organ wasting whereby epithelial overgrowth in eye-antennal discs leads to wasting of the adipose tissue and muscles. The wasting is associated with fat-body remodeling and muscle detachment and is dependent on tumor-secreted matrix metalloproteinase 1 (Mmp1). Mmp1 can both modulate TGFβ signaling in the fat body and disrupt basement membrane (BM)/extracellular matrix (ECM) protein localization in both the fat body and the muscle. Inhibition of TGFβ signaling or Mmps in the fat body/muscle using a QF2-QUAS binary expression system rescues muscle wasting in the presence of tumor. Altogether, our study proposes that tumor-derived Mmps are central mediators of organ wasting in cancer cachexia.

Revisiting Cancer Cachexia: Pathogenesis, Diagnosis, and Current Treatment Approaches

The objective of this article is to group together various management strategies and to highlight the recent treatment modifications that attempt to target the multimodal etiological factors involved in cancer cachexia. The contemporary role of nursing fraternity in psychosocial and nutritional assessment of cancer patients is briefly discussed. Cachexia is a syndrome of metabolic disturbance, characterized by the inflammation and loss of muscle with or without loss of adipose tissue. In cancer cachexia, a multifaceted condition, patients suffer from loss of body weight that leads to a negative impact on the quality of life and survival of the patients. The main cancers associated with cachexia are that of pancreas, stomach, lung, esophagus, liver, and that of bowel. The changes include increased proteolysis, lipolysis, insulin resistance, high energy expenditure, and reduced intake of food, all leading to impaired response to different treatments. There is no standardized treatment for cancer cachexia that can stabilize or reverse this complex metabolic disorder at present. The mainstay of cancer cachexia therapy remains to be sufficient nutritional supplements with on-going efforts to explore the drugs that target heightened catabolic processes and complex inflammation. There is a need to develop a multimodal treatment approach combining pharmacology, exercise program, and nutritional support to target anorexia and the severe metabolic changes encountered in cancer cachexia.

Drosophila Larval Models of Invasive Tumorigenesis for In Vivo Studies on Tumour/Peripheral Host Tissue Interactions during Cancer Cachexia

Cancer cachexia is a common deleterious paraneoplastic syndrome that represents an area of unmet clinical need, partly due to its poorly understood aetiology and complex multifactorial nature. We have interrogated multiple genetically defined larval Drosophila models of tumourigenesis against key features of human cancer cachexia. Our results indicate that cachectic tissue wasting is dependent on the genetic characteristics of the tumour and demonstrate that host malnutrition or tumour burden are not sufficient to drive wasting. We show that JAK/STAT and TNF-α/Egr signalling are elevated in cachectic muscle and promote tissue wasting. Furthermore, we introduce a dual driver system that allows independent genetic manipulation of tumour and host skeletal muscle. Overall, we present a novel Drosophila larval paradigm to study tumour/host tissue crosstalk in vivo, which may contribute to future research in cancer cachexia and impact the design of therapeutic approaches for this pathology.

A standardized herbal combination of Astragalus membranaceus and Paeonia japonica, protects against muscle atrophy in a C26 colon cancer cachexia mouse model

ETHNOPHARMACOLOGICAL RELEVANCE

Astragalus membranaceus (Fisch.) and Bunge and Paeonia japonica (Makino)Miyabe & H.Takeda have been traditionally used to improve the poor quality of life such as weakness, lack of appetite, fatigue, and malaise which is considered with cachexia condition.

AIM OF THE STUDY

We investigated anti-cachectic effects of a herbal formula composed of Astragalus membranaceus and Paeonia japonica (APX) and the molecular mechanisms of APX in C26 cancer-induced cachexia mice and TNF-a-treated C2C12 myotubes. Additionally synergistic anti-cachectic effects of APX were compared to those of individual herbal extracts and megestrol acetate.

METHODS AND MATERIALS

The forty-two BALB/c mice were randomly divided into 6 groups: normal (nontreatment), control (C26 injection), AM (C26 injection with Astragalus membranaceus), PJ (C26 injection with Paeonia japonica), APX (C26 injection with combination of Astragalus membranaceus and Paeonia japonica and MA (C26 injection with megestrol acetate). All mice were orally administered DW (normal and control groups) or 100 mg/kg AM, PJ, APX or MA for 10 days. In the animal model, several tissues were weighed, and muscle tissue and blood were used to measure pro-inflammatory cytokines. C2C12 myotubes were exposed to 100 ng/mL TNF- α with or without 10 μg/mL of AM, PJ, APX or MA for 48 h. The cells were used to immunofluorescence staining and western blot analyses.

RESULTS

C26 injection induced notable body and muscle weight loss while APX administration significantly attenuated these alterations and the decrease of muscle weights and strength. APX also significantly attenuated the abnormal elevations in the concentration of three muscle atrophy-inducible cytokines; serum and muscle TNF-α,muscle TWEAK and IL-6 in C26 tumor-bearing mice. In the TNF-α-treated C2C12 myotube model, TNF-α treatment notably decreased MyH but activated atrophic proteins (MuRF and Fbx32) along with p38 and NFκB while these molecular alterations were significantly ameliorated by APX treatment. These pharmacological actions of APX were supported by the results of immunofluorescence staining to MyH expression and the translocation of NFκB into the nucleus in C2C12 myotubes.

CONCLUSIONS

Our data indicate the potential of an herbal formula, APX as an anti-cachexia agent; the effect of APX was superior to that of megestrol acetate overall especially for muscle atrophy. The underlying mechanisms of this herbal formula may involve the modulation of muscle atrophy-promoting molecules including p38, NFκB, TNF-α and TWEAK.

Fungal Dysbiosis Correlates with the Development of Tumor-Induced Cachexia in Mice

Cachexia (CC) is a devastating metabolic syndrome associated with a series of underlying diseases that greatly affects life quality and expectancy among cancer patients. Studies involving mouse models, in which CC was induced through inoculation with tumor cells, originally suggested the existence of a direct correlation between the development of this syndrome and changes in the relative proportions of several bacterial groups present in the digestive tract. However, these analyses have focus solely on the characterization of bacterial dysbiosis, ignoring the possible existence of changes in the relative populations of fungi, during the development of CC. Thus, the present study sought to expand such analyses, by characterizing changes that occur in the gut fungal population (mycobiota) of mice, during the development of cancer-induced cachexia. Our results confirm that cachectic animals, submitted to Lewis lung carcinoma (LLC) transplantation, display significant differences in their gut mycobiota, when compared to healthy controls. Moreover, identification of dysbiotic fungi showed remarkable consistency across successive levels of taxonomic hierarchy. Many of these fungi have also been associated with dysbioses observed in a series of gut inflammatory diseases, such as obesity, colorectal cancer (CRC), myalgic encephalomyelitis (ME) and inflammatory bowel disease (IBD). Nonetheless, the dysbiosis verified in the LLC model of cancer cachexia seems to be unique, presenting features observed in both obesity (reduced proportion of Mucoromycota) and CRC/ME/IBD (increased proportions of Sordariomycetes, Saccharomycetaceae and Malassezia). One species of Mucoromycota (Rhyzopus oryzae) stands out as a promising probiotic candidate in adjuvant therapies, aimed at treating and/or preventing the development of CC.

Characterization of cachexia in the human fibrosarcoma HT-1080 mouse tumour model

BACKGROUND

Cancer cachexia is a complex metabolic disease with unmet medical need. Although many rodent models are available, none are identical to the human disease. Therefore, the development of new preclinical models that simulate some of the physiological, biochemical, and clinical characteristics of the human disease is valuable. The HT-1080 human fibrosarcoma tumour cell line was reported to induce cachexia in mice. Therefore, the purpose of this work was to determine how well the HT-1080 tumour model could recapitulate human cachexia and to examine its technical performance. Furthermore, the efficacy of ghrelin receptor activation via anamorelin treatment was evaluated, because it is one of few clinically validated mechanisms.

METHODS

Female severe combined immunodeficient mice were implanted subcutaneously or heterotopically (renal capsule) with HT-1080 tumour cells. The cachectic phenotype was evaluated during tumour development, including body weight, body composition, food intake, muscle function (force and fatigue), grip strength, and physical activity measurements. Heterotopic and subcutaneous tumour histology was also compared. Energy balance was evaluated at standard and thermoneutral housing temperatures in the subcutaneous model. The effect of anamorelin (ghrelin analogue) treatment was also examined.

RESULTS

The HT-1080 tumour model had excellent technical performance and was reproducible across multiple experimental conditions. Heterotopic and subcutaneous tumour cell implantation resulted in similar cachexia phenotypes independent of housing temperature. Tumour weight and histology was comparable between both routes of administration with minimal inflammation. Subcutaneous HT-1080 tumour-bearing mice presented with weight loss (decreased fat mass and skeletal muscle mass/fibre cross-sectional area), reduced food intake, impaired muscle function (reduced force and grip strength), and decreased spontaneous activity and voluntary wheel running. Key circulating inflammatory biomarkers were produced by the tumour, including growth differentiation factor 15, Activin A, interleukin 6, and TNF alpha. Anamorelin prevented but did not reverse anorexia and weight loss in the subcutaneous model.

CONCLUSIONS

The subcutaneous HT-1080 tumour model displays many of the perturbations of energy balance and physical performance described in human cachexia, consistent with the production of key inflammatory factors. Anamorelin was most effective when administered early in disease progression. The HT-1080 tumour model is valuable for studying potential therapeutic targets for the treatment of cachexia.

[Cardio-oncology - elucidation of the mechanism of cardiac dysfunction caused by cancer therapy and cancer cachexia]

Cardiovascular disorders in cancer patients with cachexia have recently become a great concern. However, the relationship between cancer cachexia and cardiac dysfunction remains unclear, due to lack of suitable models. We established a novel murine model of cancer cachexia by implantation of 85As2 cells, a cell line derived from human gastric cancer cells, presenting anorexia, weight loss and low fat-free mass similar to those observed in patients. Moreover, cardiac dysfunction is expected in this model, which has not been yet examined. In the present study, we firstly evaluated cardiac functions with the model. Secondly, we investigated effects of voluntary wheel running (VWR) on cachexia-induced cardiac dysfunction using this model, as the exercise is considered to be one of therapies for chronic heart failure. 85As2 cells were transplanted subcutaneously into mice, which observed a symptomatic cachexia; decrease in body, skeletal muscle weight, and food intake. In addition, this cachexia mouse developed severe cardiac atrophy and left ventricular ejection fraction (LVEF) also markedly reduced with cachexia progression. Moreover, VWR suppressed the decrease in food intake and skeletal muscle weight loss in this model, and improved LVEF with suppression of heart weight loss. These results imply that our 85As2-cachexia mice models show cardiac dysfunction and VWR may improve not only cachexia symptoms but also cardiac dysfunction. As exercise therapy is generally introduced for the purpose of improving heart failure symptoms, this study suggests a possible therapeutic effect of exercise on cardiac dysfunction induced by cancer cachexia.

Mitochondrial Metabolism in Cancer Cachexia: Novel Drug Target

BACKGROUND

Cancer cachexia is a metabolic syndrome prevalent in the majority of the advanced cancers and is associated with complications such as anorexia, early satiety, weakness, anaemia, and edema, thereby reducing performance and impairing quality of life. Skeletal muscle wasting is a characteristic feature of cancer-cachexia and mitochondria is responsible for regulating total protein turnover in skeletal muscle tissue.

METHODS

We carried out exhaustive search for cancer cachexia and role of mitochondria in the same in various databases. All the relevant articles were gathered and the pertinent information was extracted out and compiled which was further structured into different sub-sections.

RESULTS

Various findings on the mitochondrial alterations in connection to its disturbed normal physiology in various models of cancer-cachexia have been recently reported, suggesting a significant role of the organelle in the pathogenesis of the complications involved in the disorder. It has also been reported that reduced mitochondrial oxidative capacity is due to reduced mitochondrial biogenesis as well as altered balance between fusion and fission protein activities. Moreover, autophagy in mitochondria (termed as mitophagy) is reported to play an important role in cancer cachexia.

CONCLUSION

The present review aims to put forth the changes occurring in mitochondria and hence explore possible targets which can be exploited in cancer-induced cachexia for treatment of such a debilitating condition.

Cancer cachexia: a multifactoral disease that needs a multimodal approach

PURPOSE OF REVIEW

Cancer cachexia is a complex condition that occurs in approximately 50% of cancer patients and in 80% of those with advanced cancer. It is characterized by lean body mass loss, adipose tissue loss, altered metabolism, increased inflammation, and a decrease in quality of life. Cancer cachexia is a frustrating condition to manage and treatment requires an innovative approach. The purpose of this article is to review the current treatments for cancer cachexia and how they could be used in a multimodal approach.

RECENT FINDINGS

Cancer cachexia has many causes, but is primarily a result of reduced energy-protein intake and altered metabolism augmented by a proinflammatory state. There is not a formal consensus on diagnosing cancer cachexia, but proactive screening and assessments for malnutrition are an effective first step toward identifying high-risk patients. Treatment of cancer cachexia includes optimizing nutrition care, using appropriate pharmacological agents, preserving lean body mass, and the cooperation of the healthcare team.

SUMMARY

Cancer cachexia is a complex multifactorial condition that can only be successfully managed and treated with a multimodal approach that involves a multidisciplinary team that includes an oncology registered dietitian nutritionist and exercise physiologist that target early detection and management of cancer cachexia.

Promising models for cancer-induced cachexia drug discovery

Introduction: Cachexia is a frequent, multifactorial syndrome associated with cancer afflicting patients' quality of life, their ability to tolerate anti-neoplastic therapies and the therapies efficacy, as well as survival. Currently, there are no approved cancer cachexia treatments other than those for the treatment of the underlying cancer. Cancer cachexia (CC) is poorly understood and hence makes clinical trial design difficult at best. This underlines the importance of well-characterized animal models to further elucidate the pathophysiology of CC and drug discovery/development.Areas covered: This review gives an overview of the available animal models and their value and limitations in translational studies.Expert opinion: Using more than one CC model to test research questions or novel compounds/treatment strategies is strongly advisable. The main reason is that models have unique signaling modalities driving cachexia that may only relate to subgroups of cancer patients. Human xenograph CC models require the use of mice with a compromised immune system, limiting their value for translational experiments. It may prove beneficial to include standard care chemotherapy in the experimental design, as many chemotherapeutic agents can induce cachexia themselves and alter the metabolic and signaling derangements of CC and thus the response to new therapeutic strategies.

Paeonia lactiflora root extract suppresses cancer cachexia by down-regulating muscular NF-κB signalling and muscle-specific E3 ubiquitin ligases in cancer-bearing mice

ETHNOPHARMACOLOGICAL RELEVANCE

The dried root of Paeonia lactiflora Pall. (Radix Paeoniae) has been traditionally used to treat various inflammatory diseases in many Asian countries.

AIM OF THE STUDY

Cancer cachexia is a catabolic syndrome driven by inflammation and characterised by a loss of skeletal muscle. This study aimed to assess the effects of an ethanolic extract of Radix Paeoniae (RP) on cancer cachexia and elucidate its mechanism of action.

MATERIAL AND METHODS

The anti-cachexic effect and mechanism of RP were examined in mouse models of cancer cachexia established in C57BL/6 mice by subcutaneously injecting Lewis lung carcinoma or MC38 colon carcinoma cells. Skeletal muscle tissues were analysed by RNAseq, real-time quantitative reverse transcription PCR, western blotting, and immunofluorescence microscopy. Megestrol acetate, which is recommended for the treatment of cachexia in cancer patients, was used as the comparator treatment in this study.

RESULTS

In lung and colon cancer-bearing mice, RP significantly restored food intake and muscle mass, along with muscle function measured by grip strength and treadmill running time. In the skeletal muscle tissue of the cancer-bearing mice, RP suppressed NF-κB signalling and reduced inflammatory cytokines, including TNF-α, IL-6, and IL-1β; it also down-regulated the muscle-specific E3 ubiquitin ligases MuRF1 and MAFbx.

CONCLUSION

RP restored skeletal muscle function and mass in cancer-bearing mice by down-regulating the muscular NF-κB signalling pathway and muscle-specific E3 ubiquitin ligases. Our study indicates that RP is a potential candidate for development as a therapeutic agent against cancer cachexia.

Effects of conditioned media from murine lung cancer cells and human tumor cells on cultured myotubes

Factors secreted from tumors/tumor cells are hypothesized to cause skeletal muscle wasting in cancer patients. We examined whether cancer cells secrete factors to promote atrophy by evaluating the effects of conditioned media (CM) from murine lung cancer cells and primary cultures of human lung tumor cells on cultured myotubes. We evaluated murine Lewis lung carcinoma (LLC) and KRAS^G12D cells, and primary cell lines derived from tumor biopsies from patients with lung cancer (hTCM; n = 6). In all experiments, serum content was matched across treatment groups. We hypothesized that CM from murine and human tumor cells would reduce myotube myosin content, decrease mitochondrial content, and increase mitochondrial reactive oxygen species (ROS) production. Treatment of myotubes differentiated for 7 days with CM from LLC and KRAS^G12D cells did not alter any of these variables. Effects of murine tumor cell CM were observed when myotubes differentiated for 4 days were treated with tumor cell CM and compared with undiluted differentiation media. However, these effects were not apparent if tumor cell CM treatments were compared with control cell CM or dilution controls. Finally, CM from human lung tumor primary cell lines did not modify myosin content or mitochondrial content or ROS production compared with either undiluted differentiated media, control cell CM, or dilution controls. Our results do not support the hypothesis that factors released from cultured lung cancer/tumor cells promote myotube wasting or mitochondrial abnormalities, but we cannot dismiss the possibility that these cells could secrete such factors in vivo within the native tumor microenvironment.

Metastasis and cachexia: alongside in clinics, but not so in animal models

Cancer cachexia is a paraneoplastic syndrome characterized by lean mass wasting (with or without fat mass decrease), culminating in involuntary weight loss, which is the key clinical observation nowadays. There is a notable lack of studies involving animal models to mimic the clinical reality, which are mostly patients with cachexia and metastatic disease. This mismatch between the clinical reality and animal models could at least partly contribute to the poor translation observed in the field. In this paper, we retrieved and compared animal models used for cachexia research from 2017 and 10 years earlier (2007) and observed that very little has changed. Especially, clinically relevant models where cachexia is studied in an orthotopic or metastatic context were and still are very scarce. Finally, we described and supported the biological rationale behind why, despite technical challenges, these two phenomena-metastasis and cachexia-should be modelled in parallel, highlighting the overlapping pathways between them. To sum up, this review aims to contribute to rethinking and possibly switching the models currently used for cachexia research, to hopefully obtain better and more translational outcomes.

Macrophages protect against loss of adipose tissue during cancer cachexia

BACKGROUND

Cancer cachexia represents a central obstacle in medical oncology as it is associated with poor therapy response and reduced overall survival. Systemic inflammation is considered to be a key driver of cancer cachexia; however, clinical studies with anti-inflammatory drugs failed to show distinct cachexia-inhibiting effects. To address this contradiction, we investigated the functional importance of innate immune cells for hepatocellular carcinoma (HCC)-associated cachexia.

METHODS

A transgenic HCC mouse model was intercrossed with mice harbouring a defect in myeloid cell-mediated inflammation. Body composition of mice was analysed via nuclear magnetic resonance spectroscopy and microcomputed tomography. Quantitative PCR was used to determine adipose tissue browning and polarization of adipose tissue macrophages. The activation state of distinct areas of the hypothalamus was analysed via immunofluorescence. Multispectral immunofluorescence imaging and immunoblot were applied to characterize sympathetic neurons and macrophages in visceral adipose tissue. Quantification of pro-inflammatory cytokines in mouse serum was performed with a multiplex immunoassay. Visceral adipose tissue of HCC patients was quantified via the L3 index of computed tomography scans obtained during routine clinical care.

RESULTS

We identified robust cachexia in the HCC mouse model as evidenced by a marked loss of visceral fat and lean mass. Computed tomography-based analyses demonstrated that a subgroup of human HCC patients displays reduced visceral fat mass, complementing the murine data. While the myeloid cell-mediated inflammation defect resulted in reduced expression of pro-inflammatory cytokines in the serum of HCC-bearing mice, this unexpectedly did not translate into diminished but rather enhanced cachexia-associated fat loss. Defective myeloid cell-mediated inflammation was associated with decreased macrophage abundance in visceral adipose tissue, suggesting a role for local macrophages in the regulation of cancer-induced fat loss.

CONCLUSIONS

Myeloid cell-mediated inflammation displays a rather unexpected beneficial function in a murine HCC model. These results demonstrate that immune cells are capable of protecting the host against cancer-induced tissue wasting, adding a further layer of complexity to the pathogenesis of cachexia and providing a potential explanation for the contradictory results of clinical studies with anti-inflammatory drugs.

Cachexia induced by Yoshida ascites hepatoma in Wistar rats is not associated with inflammatory response in the spleen or brain

Recent data indicate that peripheral, as well as hypothalamic pro-inflammatory cytokines play an important role in the development of cancer cachexia. However, there are only a few studies simultaneously investigating the expression of inflammatory molecules in both the periphery and hypothalamic structures in animal models of cancer cachexia. Therefore, using the Yoshida ascites hepatoma rat's model of cancer cachexia we investigated the gene expression of inflammatory markers in the spleen along with the paraventricular and arcuate nuclei, two hypothalamic structures that are involved in regulating energy balance. In addition, we investigated the effect of intracerebroventricular administration of PS-1145 dihydrochloride (an Ikβ inhibitor) on the expression of selected inflammatory molecules in these hypothalamic nuclei and spleen. We observed significantly reduced food intake in tumor-bearing rats. Moreover, we found significantly decreased expression of IL-6 in the spleen as well as decreased NF-κB in the paraventricular nucleus of rats with Yoshida ascites hepatoma. Similarly, expression of TNF-α, IL-1β, NF-κB, and COX-2 in the arcuate nucleus was significantly reduced in tumor-bearing rats. Administration of PS-1145 dihydrochloride reduced only the gene expression of COX-2 in the hypothalamus. Based on our findings, we suggest that the growing Yoshida ascites hepatoma decreased food intake by mechanical compression of the gut and therefore this model is not suitable for investigation of the inflammation-related mechanisms of cancer cachexia development.

Chemotherapy-induced cachexia dysregulates hypothalamic and systemic lipoamines and is attenuated by cannabigerol

BACKGROUND

Muscle wasting, anorexia, and metabolic dysregulation are common side-effects of cytotoxic chemotherapy, having a dose-limiting effect on treatment efficacy, and compromising quality of life and mortality. Extracts of Cannabis sativa, and analogues of the major phytocannabinoid Δ9-tetrahydrocannabinol, have been used to ameliorate chemotherapy-induced appetite loss and nausea for decades. However, psychoactive side-effects limit their clinical utility, and they have little efficacy against weight loss. We recently established that the non-psychoactive phytocannabinoid cannabigerol (CBG) stimulates appetite in healthy rats, without neuromotor side-effects. The present study assessed whether CBG attenuates anorexia and/or other cachectic effects induced by the broad-spectrum chemotherapy agent cisplatin.

METHODS

An acute cachectic phenotype was induced in adult male Lister-hooded rats by 6 mg/kg (i.p.) cisplatin. In total 66 rats were randomly allocated to groups receiving vehicle only, cisplatin only, or cisplatin and 60 or 120 mg/kg CBG (po, b.i.d.). Feeding behavior, bodyweight and locomotor activity were recorded for 72 hours, at which point rats were sacrificed for post-mortem analyses. Myofibre atrophy, protein synthesis and autophagy dysregulation were assessed in skeletal muscle, plasma metabolic profiles were obtained by untargeted 1H-NMR metabonomics, and levels of endocannabinoid-like lipoamines quantified in plasma and hypothalami by targeted HPLC-MS/MS lipidomics.

RESULTS

CBG (120 mg/kg) modestly increased food intake, predominantly at 36-60hrs (p<0.05), and robustly attenuated cisplatin-induced weight loss from 6.3% to 2.6% at 72hrs (p<0.01). Cisplatin-induced skeletal muscle atrophy was associated with elevated plasma corticosterone (3.7 vs 13.1ng/ml, p<0.01), observed selectively in MHC type IIx (p<0.05) and IIb (p<0.0005) fibres, and was reversed by pharmacological rescue of dysregulated Akt/S6-mediated protein synthesis and autophagy processes. Plasma metabonomic analysis revealed cisplatin administration produced a wide-ranging aberrant metabolic phenotype (Q2Ŷ=0.5380, p=0.001), involving alterations to glucose, amino acid, choline and lipid metabolism, citrate cycle, gut microbiome function, and nephrotoxicity, which were partially normalized by CBG treatment (Q2Ŷ=0.2345, p=0.01). Lipidomic analysis of hypothalami and plasma revealed extensive cisplatin-induced dysregulation of central and peripheral lipoamines (29/79 and 11/26 screened, respectively), including reversible elevations in systemic N-acyl glycine concentrations which were negatively associated with the anti-cachectic effects of CBG treatment.

CONCLUSIONS

Endocannabinoid-like lipoamines may have hitherto unrecognized roles in the metabolic side-effects associated with chemotherapy, with the N-acyl glycine subfamily in particular identified as a potential therapeutic target and/or biomarker of anabolic interventions. CBG-based treatments may represent a novel therapeutic option for chemotherapy-induced cachexia, warranting investigation in tumour-bearing cachexia models.

Moderate exercise training since adolescence reduces Walker 256 tumour growth in adult rats

KEY POINTS

Cancer growth, cell proliferation and cachexia index can be attenuated by the beneficial programming effect of moderate exercise training, especially if it begins in adolescence. Walker 256 tumour-bearing rats who started exercise training during adolescence did not revert the basal low glycaemia and insulinaemia observed before tumour cell inoculation. The moderate exercise training improved glucose tolerance and peripheral insulin sensitivity only in rats exercised early in adolescence. The chronic effects of our exercise protocol are be beneficial to prevent cancer cachexia and hold clear potential as a nonpharmacological therapy of insulin sensitization.

ABSTRACT

We tested the hypothesis that moderate exercise training, performed early, starting during adolescence or later in life during adulthood, can inhibit tumour cell growth as a result of changes in biometric and metabolic markers. Male rats that were 30 and 70 days old performed a treadmill running protocol over 8 weeks for 3 days week^-1 , 44 min day^-1 and at 55-65% V ̇ O 2 max . After the end of training, a batch of rats was inoculated with Walker 256 carcinoma cells. At 15 days after carcinoma cell inoculation, the tumour was weighed and certain metabolic parameters were evaluated. The data demonstrated that physical performance was better in rats that started exercise training during adolescence according to the final workload and V ̇ O 2 max . Early or later moderate exercise training decreased the cachexia index, cell proliferation and tumour growth; however, the effects were more pronounced in rats that exercised during adolescence. Low glycaemia, insulinaemia and tissue insulin sensitivity was not reverted in Walker 256 tumour-bearing rats who trained during adolescence. Cancer growth can be attenuated by the beneficial programming effect of moderate exercise training, especially if it begins during adolescence. In addition, improvement in glucose-insulin homeostasis might be involved in this process.

Development and characterization of a cancer cachexia model employing a rare human duodenal neuroendocrine carcinoma-originating cell line

Cancer cachexia interferes with therapy and worsens patients' quality of life. Therefore, for a better understanding of cachexia, we aimed to establish a reliable cell line to develop a cachexia model. We recently established and characterized the TCC-NECT-2 cell line, derived from a Japanese patient with poorly differentiated neuroendocrine carcinoma of the duodenum (D-NEC). Subcutaneous xenograft of TCC-NECT-2 cells in mice resulted in tumor formation, angiogenesis, and 20% incidence of body weight (BW)-loss. Subsequently, we isolated a potent cachexia-inducing subline using stepwise selection and designated as AkuNEC. Orthotopic and s.c. implantation of AkuNEC cells into mice led to diminished BW, anorexia, skeletal muscle atrophy, adipose tissue loss, and decreased locomotor activity at 100% incidence. Additionally, orthotopic implantation of AkuNEC cells resulted in metastasis and angiogenesis. Serum IL-8 overproduction was observed, and levels were positively correlated with BW-loss and reduced adipose tissue and muscle volumes in tumor-bearing mice. However, shRNA knockdown of the IL-8 gene did not suppress tumor growth and cachexia in the AkuNEC model, indicating that IL-8 is not directly involved in cachexia induction. In conclusion, AkuNEC cells may serve as a useful model to study cachexia and D-NEC.

Metabolic Profiling of Tumors, Sera, and Skeletal Muscles from an Orthotopic Murine Model of Gastric Cancer Associated-Cachexia

Cachexia is a complex metabolic derangement syndrome that affects approximately 50-80% of cancer patients. So far, few works have been reported to provide a global overview of gastric cancer cachexia (GCC)-related metabolic changes. We established a GCC murine model by orthotopicly implanting BGC823 cell line and conducted NMR-based metabolomic analysis of gastric tissues, sera, and gastrocnemius. The model with typical cachexia symptoms, confirmed by significant weight loss and muscle atrophy, showed distinctly distinguished metabolic profiles of tumors, sera, and gastrocnemius from sham mice. We identified 20 differential metabolites in tumors, 13 in sera, and 14 in gastrocnemius. Tumor extracts displayed increased pyruvate and lactate, and decreased hypoxanthine, inosine, and inosinate, indicating significantly altered glucose and nucleic acid metabolisms. Cachectic mice exhibited up-regulated serum lactate and glycerol, and down-regulated glucose, which were closely related to hyperlipidemia and hypoglycemia. Furthermore, gastrocnemius transcriptomic and metabolomic data revealed that GCC induced perturbed pathways mainly concentrated on carbohydrate and amino acid metabolism. Specifically, cachectic gastrocnemius exhibited increased α-ketoglutarate and decreased glucose. In vitro study indicated that α-ketoglutarate could prompt myoblasts proliferation and reduce glucose deficiency-induced myotubes atrophy. Overall, this work provides a global metabolic overview to understand the metabolic alterations associated with GCC-induced muscle atrophy.

Drosophila as a Model for Tumor-Induced Organ Wasting

In humans, cancer-associated cachexia is a complex syndrome that reduces the overall quality of life and survival of cancer patients, particularly for those undergoing chemotherapy. The most easily observable sign of cachexia is organ wasting, the dramatic loss of skeletal muscle and adipose tissue mass. Estimates suggest that 80% of patients in advanced stages of cancer show signs of the syndrome and about 20% of cancer patients die directly of cachexia. Because there is no treatment or drug available to ameliorate organ wasting induced by cancer, cachexia is a relevant clinical problem. However, it is unclear how cachexia is mediated, what factors drive interactions between tumors and host tissues, and which markers of cachexia might be used to allow early detection before the observable signs of organ wasting. In this chapter, we review the current mammalian models of cachexia and the need to use new models of study. We also explain recent developments in Drosophila as a model for studying organ wasting induced by tumors and how fly studies can help unravel important mechanisms that drive cachexia. In particular, we discuss what lessons have been learned from tumor models recently reported to induce systemic organ wasting in Drosophila.

Mouse models of cancer-induced cachexia: Hind limb muscle mass and evoked force as readouts

The majority of patients with advanced cancer suffer from cachexia, a systemic wasting syndrome, which subsequently impacts the tolerance to anti-cancer treatments, response to therapy, quality of life, and eventually, survival. Despite a high unmet medical need, there is currently no specific remedy available for an effective treatment of cachexia and its sequelae. A key feature of cachexia is the inexorable loss of skeletal muscle mass, which constitutes a main contributor to body weight loss and progressive functional impairments. Therefore, it's crucial to identify early readouts to detect and monitor the loss of muscle mass and function to initiate appropriate treatments timely. Here, we describe experimental cancer models using mouse (syngeneic) or human (xenograft) cancer cell lines with a rapid onset of tumor growth and cachexia. These models are easier to establish, monitor and reproduce compared to the genetically engineered mouse models currently available. Moreover, we establish readouts such as hind limb muscle mass and volume, as well as evoked force and food intake measurements, to allow the evaluation of potential therapeutic agents for the early treatment of cachexia and associated impairments.

Walker-256 tumor alters morphology of intestinal myenteric plexus in rats

BACKGROUND

Gastrointestinal (GI) dysmotility is common in patients with cancer. There are a few studies about the myenteric plexus in the presence of anatomically remote tumors.

METHODS

Forty-eight male Wistar rats were divided into a control (CT) or Walker-256 (TW) group. Tumor cells were subcutaneously injected and saline was injected in the CT group. After 14 days, the small and large intestines were removed for histochemical analysis. The macroscopic morphology of the intestines and the fecal excretion were also observed.

KEY RESULTS

The upper GI transit and weight of fecal pellets were reduced and the walls of the large intestine in tumor-bearing rats showed multiple constrictions. In the capsules' constitution of the myenteric plexus of the TW group, there were type III collagen fibers in addition to type I fibers, and the thin septa inside the capsule were absent. The large intestine in the TW group exhibited smaller neurons and the number of nitrergic-positive neurons was also reduced in the myenteric plexus, compared to the CT group. In the TW group, the neuronal numbers and the staining intensity of acetylcholinesterase (AChE) were reduced in the large intestine. Staining was not different in the small intestine.

CONCLUSIONS AND INFERENCES

This study showed that the Walker-256 tumor induced alterations in the morphology of nitrergic and cholinergic neurons in the myenteric plexus and decreased the upper GI transit with the presence of multiple constrictions in the colon. Therefore, these alterations can interfere on neurotransmission and can be related to the intestinal motility alterations observed in tumor-bearing rats.

Animal models for cancer cachexia

PURPOSE OF REVIEW

Cancer cachexia is a frequent syndrome that affects patient quality of life, anticancer treatment effectiveness, and overall survival. The lack of anticancer cachexia therapies likely relies on the complexity of the syndrome that renders difficult to design appropriate clinical trials and, conversely, on the insufficient knowledge of the underlying pathogenetic mechanisms. The aim of this review is to collect the most relevant latest information regarding cancer cachexia with a special focus on the experimental systems adopted for modeling the disease in translational studies.

RECENT FINDINGS

The scenario of preclinical models for the study of cancer cachexia is not static and is rapidly evolving in parallel with new prospective treatment options. The well established syngeneic models using rodent cancer cells injected ectopically are now used alongside new ones featuring orthotopic injection, human cancer cell or patient-derived xenograft, or spontaneous tumors in genetically engineered mice.

SUMMARY

The use of more complex animal models that better resemble cancer cachexia, ideally including also the administration of chemotherapy, will expand the understanding of the underlying mechanisms and will allow a more reliable evaluation of prospective drugs for translational purposes.

Growth hormone secretagogues prevent dysregulation of skeletal muscle calcium homeostasis in a rat model of cisplatin-induced cachexia

BACKGROUND

Cachexia is a wasting condition associated with cancer types and, at the same time, is a serious and dose-limiting side effect of cancer chemotherapy. Skeletal muscle loss is one of the main characteristics of cachexia that significantly contributes to the functional muscle impairment. Calcium-dependent signaling pathways are believed to play an important role in skeletal muscle decline observed in cachexia, but whether intracellular calcium homeostasis is affected in this situation remains uncertain. Growth hormone secretagogues (GHS), a family of synthetic agonists of ghrelin receptor (GHS-R1a), are being developed as a therapeutic option for cancer cachexia syndrome; however, the exact mechanism by which GHS interfere with skeletal muscle is not fully understood.

METHODS

By a multidisciplinary approach ranging from cytofluorometry and electrophysiology to gene expression and histology, we characterized the calcium homeostasis in fast-twitch extensor digitorum longus (EDL) muscle of adult rats with cisplatin-induced cachexia and established the potential beneficial effects of two GHS (hexarelin and JMV2894) at this level. Additionally, in vivo measures of grip strength and of ultrasonography recordings allowed us to evaluate the functional impact of GHS therapeutic intervention.

RESULTS

Cisplatin-treated EDL muscle fibres were characterized by a ~18% significant reduction of the muscle weight and fibre diameter together with an up-regulation of atrogin1/Murf-1 genes and a down-regulation of Pgc1-a gene, all indexes of muscle atrophy, and by a two-fold increase in resting intracellular calcium, [Ca2+ ]i , compared with control rats. Moreover, the amplitude of the calcium transient induced by caffeine or depolarizing high potassium solution as well as the store-operated calcium entry were ~50% significantly reduced in cisplatin-treated rats. Calcium homeostasis dysregulation parallels with changes of functional ex vivo (excitability and resting macroscopic conductance) and in vivo (forelimb force and muscle volume) outcomes in cachectic animals. Administration of hexarelin or JMV2894 markedly reduced the cisplatin-induced alteration of calcium homeostasis by both common as well as drug-specific mechanisms of action. This effect correlated with muscle function preservation as well as amelioration of various atrophic indexes, thus supporting the functional impact of GHS activity on calcium homeostasis.

CONCLUSIONS

Our findings provide a direct evidence that a dysregulation of calcium homeostasis plays a key role in cisplatin-induced model of cachexia gaining insight into the etiopathogenesis of this form of muscle wasting. Furthermore, our demonstration that GHS administration efficaciously prevents cisplatin-induced calcium homeostasis alteration contributes to elucidate the mechanism of action through which GHS could potentially ameliorate chemotherapy-associated cachexia.

Anorexia-cachexia syndrome in hepatoma tumour-bearing rats requires the area postrema but not vagal afferents and is paralleled by increased MIC-1/GDF15

BACKGROUND

The cancer-anorexia-cachexia syndrome (CACS) negatively affects survival and therapy success in cancer patients. Inflammatory mediators and tumour-derived factors are thought to play an important role in the aetiology of CACS. However, the central and peripheral mechanisms contributing to CACS are insufficiently understood. The area postrema (AP) and the nucleus tractus solitarii are two important brainstem centres for the control of eating during acute sickness conditions. Recently, the tumour-derived macrophage inhibitory cytokine-1 (MIC-1) emerged as a possible mediator of cancer anorexia because lesions of these brainstem areas attenuated the anorectic effect of exogenous MIC-1 in mice.

METHODS

Using a rat hepatoma tumour model, we examined the roles of the AP and of vagal afferents in the mediation of CACS. Specifically, we investigated whether a lesion of the AP (APX) or subdiaphragmatic vagal deafferentation (SDA) attenuate anorexia, body weight, muscle, and fat loss. Moreover, we analysed MIC-1 levels in this tumour model and their correlation with tumour size and the severity of the anorectic response.

RESULTS

In tumour-bearing sham-operated animals mean daily food intake significantly decreased. The anorectic response was paralleled by a significant loss of body weight and muscle mass. APX rats were protected against anorexia, body weight loss, and muscle atrophy after tumour induction. In contrast, subdiaphragmatic vagal deafferentation did not attenuate cancer-induced anorexia or body weight loss. Tumour-bearing rats had substantially increased MIC-1 levels, which positively correlated with tumour size and cancer progression and negatively correlated with food intake.

CONCLUSIONS

These findings demonstrate the importance of the AP in the mediation of cancer-dependent anorexia and body weight loss and support a pathological role of MIC-1 as a tumour-derived factor mediating CACS, possibly via an AP-dependent action.

The MEK-Inhibitor Selumetinib Attenuates Tumor Growth and Reduces IL-6 Expression but Does Not Protect against Muscle Wasting in Lewis Lung Cancer Cachexia

Cachexia, or wasting of skeletal muscle and fat, afflicts many patients with chronic diseases including cancer, organ failure, and AIDS. Muscle wasting reduces quality of life and decreases response to therapy. Cachexia is caused partly by elevated inflammatory cytokines, including interleukin-6 (IL-6). Others and we have shown that IL-6 alone is sufficient to induce cachexia both in vitro and in vivo. The mitogen-activated protein/extracellular signal-regulated kinase kinase (MEK) inhibitor Selumetinib has been tested in clinical trials for various cancers. Moreover, Selumetinib has also been shown to inhibit the production of IL-6. In a retrospective analysis of a phase II clinical trial in advanced cholangiocarcinoma, patients treated with Selumetinib experienced significant gains in skeletal muscle vs. patients receiving standard therapy. However, the use of Selumetinib as a treatment for cachexia has yet to be investigated mechanistically. We sought to determine whether MEK inhibition could protect against cancer-induced cachexia in mice. In vitro, Selumetinib induced C2C12 myotube hypertrophy and nuclear accretion. Next we tested Selumetinib in the Lewis lung carcinoma (LLC) model of cancer cachexia. Treatment with Selumetinib reduced tumor mass and reduced circulating and tumor IL-6; however MEK inhibition did not preserve muscle mass. Similar wasting was seen in limb muscles of Selumetinib and vehicle-treated LLC mice, while greater fat and carcass weight loss was observed with Selumetinib treatment. As well, Selumetinib did not block wasting in C2C12 myotubes treated with LLC serum. Taken together, out results suggest that this MEK inhibitor is not protective in LLC cancer cachexia despite lowering IL-6 levels, and further that it might exacerbate tumor-induced weight loss. Differences from other studies might be disease, species or model-specific.

Metabolic Changes During Cancer Cachexia Pathogenesis

Wasting of adipose tissue and skeletal muscle is a hallmark of metastatic cancer and a major cause of death. Like patients with cachexia caused by other chronic infections or inflammatory diseases, the cancer subject manifests both malnutrition and metabolic stress. Both carbohydrate utilization and amino acid incorporation are decreased in the muscles of cancer cachexia patients. Cancer cells affect host metabolism in two ways: (a) their own metabolism of nutrients into other metabolites and (b) circulating factors they secrete or induce the host to secrete. Accelerated glycolysis and lactate production, i.e., the Warburg effect and the resultant increase in Cori cycle activity, are the most widely discussed metabolic effects. Meanwhile, although a large number of pro-cachexia circulating factors have been found, such as TNFa, IL-6, myostatin, and PTHrp, none have been shown to be a dominant factor that can be targeted singly to treat cancer cachexia in humans. It is possible that given the complex multifactorial nature of the cachexia secretome, and the personalized differences between cancer patients, targeting any single circulating factor would always be insufficient to treat cachexia for all patients. Here we review the metabolic changes that occur in response to tumor growth and tumor-secreted factors during cachexia.

Diet composition as a source of variation in experimental animal models of cancer cachexia

BACKGROUND

A variety of experimental animal models are used extensively to study mechanisms underlying cancer cachexia, and to identify potential treatments. The important potential confounding effect of dietary composition and intake used in many preclinical studies of cancer cachexia is frequently overlooked. Dietary designs applied in experimental studies should maximize the applicability to human cancer cachexia, meeting the essential requirements of the species used in the study, matched between treatment and control groups as well as also being generally similar to human consumption.

METHODS

A literature review of scientific studies using animal models of cancer and cancer cachexia with dietary interventions was performed. Studies that investigated interventions using lipid sources were selected as the focus of discussion.

RESULTS

The search revealed a number of nutrient intervention studies (n = 44), with the majority including n-3 fatty acids (n = 16), mainly eicosapentaenoic acid and/or docosahexaenoic acid. A review of the literature revealed that the majority of studies do not provide information about dietary design; food intake or pair-feeding is rarely reported. Further, there is a lack of standardization in dietary design, content, source, and overall composition in animal models of cancer cachexia. A model is proposed with the intent of guiding dietary design in preclinical studies to enable comparisons of dietary treatments within the same study, translation across different study designs, as well as application to human nutrient intakes.

CONCLUSION

The potential for experimental endpoints to be affected by variations in food intake, macronutrient content, and diet composition is likely. Diet content and composition should be reported, and food intake assessed. Minimum standards for diet definition in cachexia studies would improve reproducibility of pre-clinical studies and aid the interpretation and translation of results to humans with cancer.

Evaluation of role of telmisartan in combination with 5-fluorouracil in gastric cancer cachexia

BACKGROUND

The objective of the present study was to evaluate the effect of combination of telmisartan with 5-flourouracil (5-FU) in gastric cancer cachexia induced by administering N-methyl-N'-methyl-N-nitrosoguanidine (MNNG).

METHOD

MNND was administered once daily by oral gavage for two weeks, and saturated NaCl (1ml per rat) was then given once every 3days for 4weeks. 5-FU (75mg/kg, i.v.) was administered once three weeks from 7th to 22nd week. From 7th to 22nd week, telmisartan (5mg/kg, p.o.) was also administered along with 5-FU.

RESULT

MNNG produced significant decrease in food intake, body weight, caused hyperglycemia, dyslipidemia, hypertension worsened hemodyanamics, increased cachexia markers and increased tumor markers like lactate dehydrogenase and γ-glutamyltransferase. MNNG also produced oxidative stress in the stomach tissue. Treatment with combination of telmisartan with 5-FU produced significant increase in food intake and body weight, controlled hyperglycemia and dyslipidemia, preserved hemodynamic function, and decreased the cachexia markers while 5-FU alone did not produce any such effects. Further, the combination of telmisartan with 5-FU significantly reduced tumor marker levels, oxidative stress and also significantly decreased the cell proliferation, apoptosis, hyperkeratosis, keratohyaline granules and invasive carcinoma of forestomach and reduced muscle atrophy in tibilias anterior skeletal muscle.

CONCLUSION

Our data suggests that combination of telmisartan with 5-FU treatment is beneficial in controlling cancer cachexia. Telmisartan can be used as an add-on therapy with 5-FU or other traditional chemotherapeutic agents.

CCAAT/enhancer binding protein beta protects muscle satellite cells from apoptosis after injury and in cancer cachexia

CCAAT/enhancer binding protein beta (C/EBPβ), a transcription factor expressed in muscle satellite cells (SCs), inhibits the myogenic program and is downregulated early in differentiation. In a conditional null model in which C/EBPβ expression is knocked down in paired box protein 7+ (Pax7+) SCs, cardiotoxin (CTX) injury is poorly repaired, although muscle regeneration is efficient in control littermates. While myoblasts lacking C/EBPβ can differentiate efficiently in culture, after CTX injury poor regeneration was attributed to a smaller than normal Pax7+ population, which was not due to a failure of SCs to proliferate. Rather, the percentage of apoptotic SCs was increased in muscle lacking C/EBPβ. Given that an injury induced by BaCl₂ is repaired with greater efficiency than controls in the absence of C/EBPβ, we investigated the inflammatory response following BaCl₂ and CTX injury and found that the levels of interleukin-1β (IL-1β), a proinflammatory cytokine, were robustly elevated following CTX injury and could induce C/EBPβ expression in myoblasts. High levels of C/EBPβ expression in myoblasts correlated with resistance to apoptotic stimuli, while its loss increased sensitivity to thapsigargin-induced cell death. Using cancer cachexia as a model for chronic inflammation, we found that C/EBPβ expression was increased in SCs and myoblasts of tumor-bearing cachectic animals. Further, in cachectic conditional knockout animals lacking C/EBPβ in Pax7+ cells, the SC compartment was reduced because of increased apoptosis, and regeneration was impaired. Our findings indicate that the stimulation of C/EBPβ expression by IL-1β following muscle injury and in cancer cachexia acts to promote SC survival, and is therefore a protective mechanism for SCs and myoblasts in the face of inflammation.

Molecular pathways leading to loss of skeletal muscle mass in cancer cachexia--can findings from animal models be translated to humans?

Background

Cachexia is a multi-factorial, systemic syndrome that especially affects patients with cancer of the gastrointestinal tract, and leads to reduced treatment response, survival and quality of life. The most important clinical feature of cachexia is the excessive wasting of skeletal muscle mass. Currently, an effective treatment is still lacking and the search for therapeutic targets continues. Even though a substantial number of animal studies have contributed to a better understanding of the underlying mechanisms of the loss of skeletal muscle mass, subsequent clinical trials of potential new drugs have not yet yielded any effective treatment for cancer cachexia. Therefore, we questioned to which degree findings from animal studies can be translated to humans in clinical practice and research.

Discussion

A substantial amount of animal studies on the molecular mechanisms of muscle wasting in cancer cachexia has been conducted in recent years. This extensive review of the literature showed that most of their observations could not be consistently reproduced in studies on human skeletal muscle samples. However, studies on human material are scarce and limited in patient numbers and homogeneity. Therefore, their results have to be interpreted critically.

Summary

More research is needed on human tissue samples to clarify the signaling pathways that lead to skeletal muscle loss, and to confirm pre-selected drug targets from animal models in clinical trials. In addition, improved diagnostic tools and standardized clinical criteria for cancer cachexia are needed to conduct standardized, randomized controlled trials of potential drug candidates in the future.

Dietary leucine supplementation minimises tumour-induced damage in placental tissues of pregnant, tumour-bearing rats

Background

The occurrence of cancer during pregnancy merges two complex, poorly understood metabolic and hormonal conditions. This association can exacerbate the conditions of both the mother and the foetus. The branched-chain amino acid leucine enhances cellular activity, particularly by increasing protein synthesis. This study aimed to analyse the modulatory effect of a leucine-rich diet on direct and indirect tumour-induced placental damage. This was accomplished by evaluating the expression of genes involved in protein synthesis and degradation and assessing anti-oxidant enzyme activity in placental tissues collected from pregnant, tumour-bearing rats.

Results

Pregnant rats were either implanted with Walker 256 tumour cells or injected with ascitic fluid (to study the indirect effects of tumour growth) and then fed a leucine-rich diet. Animals in a control group underwent the same procedures but were fed a normal diet. On the 20^th day of pregnancy, tumour growth was observed. Dams fed a normoprotein diet showed the greatest tumour growth. Injection with ascitic fluid mimicked the effects of tumour growth. Decreased placental protein synthesis and increased protein degradation were observed in both the tumour-bearing and the ascitic fluid-injected groups that were fed a normoprotein diet. These effects resulted in low placental DNA and protein content and high lipid peroxidation (measured by malondialdehyde content). Decreased placental protein synthesis-related gene expression was observed in the tumour group concomitant with increased expression of genes encoding protein degradation-associated proteins and proteolytic subunits.

Conclusions

Consumption of a leucine-rich diet counteracted the effects produced by tumour growth and injection with ascitic fluid. The diet enhanced cell signalling, ameliorated deficiencies in DNA and protein content, and balanced protein synthesis and degradation processes in the placenta. The improvements in cell signalling included changes in the mTOR/eIF pathway. In conclusion, consumption of a leucine-rich diet improved placental metabolism and cell signalling in tumour-bearing rats, and these changes reduced the deleterious effects caused by tumour growth.