Inhibition of heat shock protein (HSP) 90 reverses signal transducer and activator of transcription (STAT) 3-mediated muscle wasting in cancer cachexia mice

Chaperone Proteins: The Rising Players in Muscle Atrophy

Despite significant progress in understanding the molecular aetiology of muscle atrophy, there is still a great need for new targets and drugs capable of counteracting muscle wasting. The role of an impaired proteostasis as the underlying causal mechanism of muscle atrophy is a well-established concept. From the earliest work on muscle atrophy and the identification of the first atrogenes, the hyper-activation of the proteolytic systems, such as autophagy and the ubiquitin proteasome system, has been recognized as the major driver of atrophy. However, the role of other key regulators of proteostasis, the chaperone proteins, has been largely overlooked. Chaperone proteins play a pivotal role in protein folding and in preventing the aggregation of misfolded proteins. Indeed, some chaperones, such as αB-crystallin and Hsp25, are involved in compensatory responses aimed at counteracting protein aggregation during sarcopenia. Chaperones also regulate different intracellular signalling pathways crucial for atrogene expression and the control of protein catabolism, such as the AKT and NF-kB pathways, which are regulated by Hsp70 and Hsp90. Furthermore, the downregulation of certain chaperones causes severe muscle wasting per se and experimental strategies aimed at preventing this downregulation have shown promising results in mitigating or reversing muscle atrophy. This highlights the therapeutic potential of targeting chaperones and confirms their crucial anti-atrophic functions. In this review, we summarize the most relevant data showing the modulation and the causative role of chaperone proteins in different types of skeletal muscle atrophies.

PU-H71 (NSC 750424): a molecular masterpiece that targets HSP90 in cancer and beyond

Heat shock protein 90 (HSP90) is a pivotal molecular chaperone with multifaceted roles in cellular health and disease. Herein, we explore how HSP90 orchestrates cellular stress responses, particularly through its partnership with heat shock factor 1 (HSF-1). PU-H71, a selective inhibitor of HSP90, demonstrates significant potential in cancer therapy by targeting a wide array of oncogenic pathways. By inducing the degradation of multiple client proteins, PU-H71 disrupts critical signaling pathways such as MAPK, PI3K/Akt, JAK/STAT, EGFR, and mTOR, which are essential for cancer cell survival, proliferation, and metastasis. We examined its impact on combating triple-negative breast cancer and enhancing the effectiveness of carbon-ion beam therapy, offering new avenues for cancer treatment. Furthermore, the dual inhibition of HSP90A and HSP90B1 by PU-H71 proves highly effective in the context of myeloma, providing fresh hope for patients with this challenging malignancy. We delve into its potential to induce apoptosis in B-cell lymphomas that rely on Bcl6 for survival, highlighting its relevance in the realm of hematologic cancers. Shifting our focus to hepatocellular carcinoma, we explore innovative approaches to chemotherapy. Moreover, the current review elucidates the potential capacity of PU-H71 to suppress glial cell activation paving the way for developing novel therapeutic strategies for neuroinflammatory disorders. Additionally, the present report also suggests the promising role of PU-H71 in JAK2-dependent myeloproliferative neoplasms. Eventually, our report sheds more light on the multiple functions of HSP90 protein as well as the potential therapeutic benefit of its selective inhibitor PU-H71 in the context of an array of diseases, laying the foundations for the development of novel therapeutic approaches that could achieve better treatment outcomes.

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.

Resveratrol as a potential therapeutic agent for sarcopenic obesity: Insights from in vivoperiments

Sarcopenic obesity (SO) is a metabolic disorder with increasing prevalence. It is characterized by a reduction in skeletal muscle mass and strength. Resveratrol (RSV) is one of the most frequently used herbs in the treatment of skeletal muscle atrophy. However, the precise mechanism of the action of RSV in SO remains unclear. The objective of this study was to examine the pharmacological mechanism of RSV in the context of SO through the lens of network pharmacology, to validate these findings through in vivo experimentation. A list of potential RSV targets was compiled by retrieving the data from multiple databases. This list was then cross-referenced with a list of potential targets related to SO. The intersections of RSV- and SO-related targets were analyzed using Venn diagrams. To identify the core genes, a protein-protein interaction (PPI) network of the intersection targets was constructed and subsequently analyzed. Molecular docking was used to predict RSV binding to its core targets. A high-fat diet was used to induce SO in mice. These findings indicated that RSV may prevent SO by acting on 11 targets. Among these, interleukin-6 (IL-6), C-reactive protein (CRP), and tumor necrosis factor (TNF) are considered core targets. The Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment results indicated that the anti-SO effect of RSV was predominantly linked to metabolic disease-related pathways, including those associated with nonalcoholic fatty liver disease. The anti-inflammatory effects of RSV were confirmed in vivo in an SO mouse model. This study contributes to a more comprehensive understanding of the key mechanisms of the action of RSV against SO and provides new possibilities for drug development in the pathological process of SO.

The systematic role of pancreatic cancer exosomes: distant communication, liquid biopsy and future therapy

Pancreatic cancer remains one of the most lethal diseases worldwide. Cancer-derived exosomes, benefiting from the protective role of the lipid membrane, exhibit remarkable stability in the circulatory system. These exosomes, released by tumor microenvironment, contain various biomolecules such as proteins, RNAs, and lipids that plays a pivotal role in mediating distant communication between the local pancreatic tumor and other organs or tissues. They facilitate the transfer of oncogenic factors to distant sites, contributing to the compromised body immune system, distant metastasis, diabetes, cachexia, and promoting a microenvironment conducive to tumor growth and metastasis in pancreatic cancer patients. Beyond their intrinsic roles, circulating exosomes in peripheral blood can be detected to facilitate accurate liquid biopsy. This approach offers a novel and promising method for the diagnosis and management of pancreatic cancer. Consequently, circulating exosomes are not only crucial mediators of systemic cell-cell communication during pancreatic cancer progression but also hold great potential as precise tools for pancreatic cancer management and treatment. Exosome-based liquid biopsy and therapy represent promising advancements in the diagnosis and treatment of pancreatic cancer. Exosomes can serve as drug delivery vehicles, enhancing the targeting and efficacy of anticancer treatments, modulating the immune system, and facilitating gene editing to suppress tumor growth. Ongoing research focuses on biomarker identification, drug delivery systems, and clinical trials to validate the safety and efficacy of exosome-based therapies, offering new possibilities for early diagnosis and precision treatment in pancreatic cancer. Leveraging the therapeutic potential of exosomes, including their ability to deliver targeted drugs and modulate immune responses, opens new avenues for innovative treatment strategies.

Jianpi Decoction Combined with Medroxyprogesterone Acetate Alleviates Cancer Cachexia and Prevents Muscle Atrophy by Directly Inhibiting E3 Ubiquitin Ligase

OBJECTIVE

To provide comprehensive evidence for the anti-cancer cachexia effect of Jianpi Decoction (JP) and to explore its mechanism of anti-cancer cachexia.

METHODS

A mouse model of colon cancer (CT26)-induced cancer cachexia (CC) was used to investigate the anti-CC effect of JP combined with medroxyprogesterone acetate (MPA). Thirty-six mice were equally divided into 6 groups: normal control, CC, MPA (100 mg•kg-1•d-1), MPA + low-dose (20 mg•kg-1•d-1) JP (L-JP), MPA + medium-dose (30 mg•kg-1•d-1) JP (M-JP), and MPA + high-dose (40 mg•kg-1•d-1) JP (H-JP) groups. After successful modeling, the mice were administered by gavage for 11 d. The body weight and tumor volume were measured and recorded every 2 d starting on the 8th day after implantation. The liver, heart, spleen, lung, kidney, tumor and gastrocnemius muscle of mice were collected and weighed. The pathological changes of the tumor was observed, and the cross-sectional area of the gastrocnemius muscle was calculated. The protein expressions of STAT3 and E3 ubiquitinase in the gastrocnemius muscle were measured by Western blot. In addition, an in vitro C2C12 myotube formation model was established to investigate the role of JP in hindering dexamethasone-induced muscle atrophy. In vitro experiments were divided into control, model, and JP serum groups. After 2-d administration, microscopic photographs were taken and myotube diameters were calculated. Western blot was performed to measure the protein expressions of STAT3 and E3 ubiquitinase.

RESULTS

JP combined with MPA restored tumor-induced weight loss (P<0.05, vs. CC) and muscle fiber size (P<0.01, vs. CC). Mechanistically, JP reduced the expression of atrophy-related proteins MuRF1 and MAFbx in tumor-induced muscle atrophy in vivo (P<0.05, vs. CC). In addition, JP reduced the expression of atrophy-related proteins MuRF1 and MAFbx and p-STAT3 phosphorylation (P<0.05 or P<0.01 vs. model group) in C2C12 myotubes treated with dexamethasone in vitro.

CONCLUSIONS

Administration of JP combined with MPA restores tumor-induced cachexia conditions. In addition, the profound effect of JP combined with MPA on tumor-induced cachexia may be due to its inhibition of muscle proteolysis (E3 ubiquitinase system).

Extracellular vesicles in cancer cachexia: deciphering pathogenic roles and exploring therapeutic horizons

Cancer cachexia (CC) is a debilitating syndrome that affects 50-80% of cancer patients, varying in incidence by cancer type and significantly diminishing their quality of life. This multifactorial syndrome is characterized by muscle and fat loss, systemic inflammation, and metabolic imbalance. Extracellular vesicles (EVs), including exosomes and microvesicles, play a crucial role in the progression of CC. These vesicles, produced by cancer cells and others within the tumor environment, facilitate intercellular communication by transferring proteins, lipids, and nucleic acids. A comprehensive review of the literature from databases such as PubMed, Scopus, and Web of Science reveals insights into the formation, release, and uptake of EVs in CC, underscoring their potential as diagnostic and prognostic biomarkers. The review also explores therapeutic strategies targeting EVs, which include modifying their release and content, utilizing them for drug delivery, genetically altering their contents, and inhibiting key cachexia pathways. Understanding the role of EVs in CC opens new avenues for diagnostic and therapeutic approaches, potentially mitigating the syndrome's impact on patient survival and quality of life.

Exploring the effect and mechanism of Aloin A against cancer cachexia-induced muscle atrophy via network pharmacology, molecular docking, molecular dynamics and experimental validation

80% of advanced cancer patients suffer from cachexia, but there are no FDA-approved drugs. Therefore, it is imperative to discover potential drugs.

OBJECTIVE

This study aims at exploring the effect and targets of Aloin A against cancer cachexia (CC)-induced muscle atrophy.

METHODS

Network pharmacology, molecular docking, molecular dynamics (MD) and animal model of CC-induced muscle atrophy with a series of behavior tests, muscle quality, HE staining and RT-PCR were performed to investigate the anticachectic effects and targets of Aloin A and its molecular mechanism.

RESULTS

Based on network pharmacology, 51 potential targets of Aloin A on CC-induced muscle atrophy were found, and then 10 hub genes were predicted by the PPI network. Next, KEGG and GO enrichment analysis showed that the anticachectic effect of Aloin A is associated with PI3K-AKT, MAPK, TNF, TLR, etc., pathways, and biological processes like inflammation, apoptosis and cell proliferation. Molecular docking and MD results showed good binding ability between the Aloin A and key targets. Moreover, experiments in vivo demonstrated that Aloin A effectively rescued muscle function and wasting by improving muscle quality, mean CSA, and distribution of muscle fibers by regulating HSP90AA1/AKT signaling in tumor-bearing mice.

CONCLUSION

This study offers new insights for researchers to understand the effect and mechanism of Aloin A against CC using network pharmacology, molecular docking, MD and experimental validation, and Aloin A retards CC-induced muscle wasting through multiple targets and pathways, including HSP90AA1/AKT signaling, which provides evidence for Aloin A as a potential therapy for cancer cachexia in clinic.

Pancreatic Cancer-Derived Exosomal miR-Let-7b-5p Stimulates Insulin Resistance in Skeletal Muscle Cells Through RNF20/STAT3/FOXO1 Axis Regulation

Background

Cancers trigger systemic metabolic disorders usually associated with glucose intolerance, which is an initially apparent phenomenon. One of the features of pancreatic cancer (PC) metabolic reprogramming is the crosstalk between PC and peripheral tissues (skeletal muscle and adipose tissues), emphasized by insulin resistance (IR). Our previous study reported that mice pancreatic cancer-derived exosomes could induce skeletal muscle cells (C2C12) IR, and exosomal microRNAs (miRNAs) may exert an important effect. However, the underlying mechanism remains to be further elucidated.

Methods

qPCR was used to determine the expression of let-7b-5p in normal pancreatic islet cells and PC cells. Exosomes were purified from PC cell culture medium by ultracentrifugation. The role let-7b-5p on IR-mediated by PC cells-derived exosomes was asses by Oil Red O staining using miRNA inhibitor. Western blot assay was performed to examine the expression of IR-related genes and the activation of signaling pathways. A Luciferase experiment was applied to confirm how let-7b-5p regulated the expression of RNF20. IP/WB analysis further determined whether RNF20 promoted STAT3 ubiquitination. Rescue experiment using RNF20 overexpression plasmid was performed to confirm the role of RNF20 on IR-mediated using PC cell-derived exosomes in C2C12 myotube cells.

Results

miRNA-let-7b-5p was identified as the key exosomal miRNA, which could promote the IR in C2C12 myotube cells supported the lipid accumulation, the activation of STAT3/FOXO1 axis, and the decreased expression of IRS-1 and GLUT4. RNF20, an E3 ubiquitin ligase, was confirmed as the target gene of let-7b-5p and was found to improve IR by downregulating STAT3 protein expression via ubiquitination-mediated protein degradation. The ectopic expression of RNF20 could effectively attenuate the IR mediated by the pancreatic cancer-derived exosomes in C2C12 myotube cells.

Conclusion

Our data suggest that exosomal miRNA-let-7b-5p may promote IR in C2C12 myotube cells by targeting RNF20 to activate the STAT3/FOXO1 axis.

Potential effects of gingerol topical application on components of the innate immunity in lactating goat mammary glands

In the mammary glands, production of antimicrobial components and formation of less-permeable tight junctions (TJs) are important for safe milk production. Previously, we reported that local heat treatment of udders using disposable heating pad enhances the components of innate immunity in lactating goat mammary glands. Gingerol is a polyphenol present in ginger that can induce heat-like effects. However, oral administration of polyphenols causes a decrease in biological activity through conjugation and metabolic conversion. Here, we investigated the effects of gingerol on antimicrobial components and TJs by topically applying it to lactating goat udders. Gingerol application increased the somatic cell count, cathelicidin-2 concentration, and proportion of polymorphonuclear cells in the milk and interleukin-8 production. Moreover, gingerol treatment enhanced β-defensin-1 production in milk, cultured mammary epithelial cells, and cultured somatic cells. Contrastingly, gingerol treatment did not affect the concentrations of blood-derived components (Na+, albumin, and IgG) in the milk or the TJ barrier function of cultured mammary epithelial cells. These findings suggest that the topical application of gingerol, similar to local heat treatment, to udders enhances the components of innate immunity in mammary glands. These findings may be useful for the prevention of mastitis in milk-producing animals and, hence, safe and stable dairy production.

The Role of Extracellular Heat Shock Proteins in Cardiovascular Diseases

In the early 1960s, heat shock proteins (HSPs) were first identified as vital intracellular proteinaceous components that help in stress physiology and reprogram the cellular responses to enable the organism's survival. By the early 1990s, HSPs were detected in extracellular spaces and found to activate gamma-delta T-lymphocytes. Subsequent investigations identified their association with varied disease conditions, including autoimmune disorders, diabetes, cancer, hepatic, pancreatic, and renal disorders, and cachexia. In cardiology, extracellular HSPs play a definite, but still unclear, role in atherosclerosis, acute coronary syndromes, and heart failure. The possibility of HSP-targeted novel molecular therapeutics has generated much interest and hope in recent years. In this review, we discuss the role of Extracellular Heat Shock Proteins (Ec-HSPs) in various disease states, with a particular focus on cardiovascular diseases.

The Contribution of Tumor Derived Exosomes to Cancer Cachexia

Cancer cachexia is defined as unintentional weight loss secondary to neoplasia and is associated with poor prognosis and outcomes. Cancer cachexia associated weight loss affects both lean tissue (i.e., skeletal muscle) and adipose tissue. Exosomes are extracellular vesicles that originate from multivesicular bodies that contain intentionally loaded biomolecular cargo. Exosome cargo includes proteins, lipids, mitochondrial components, and nucleic acids. The cargo carried in exosomes is thought to alter cell signaling when it enters into recipient cells. Virtually every cell type secretes exosomes and exosomes are known to be present in nearly every biofluid. Exosomes alter muscle and adipose tissue metabolism and biological processes, including macrophage polarization and apoptosis which contribute to the development of the cachexia phenotype. This has led to an interest in the role of tumor cell derived exosomes and their potential role as biomarkers of cancer cell development as well as their contribution to cachexia and disease progression. In this review, we highlight published findings that have studied the effects of tumor derived exosomes (and extracellular vesicles) and their cargo on the progression of cancer cachexia. We will focus on the direct effects of tumor derived exosomes and their cellular cross talk on skeletal muscle and adipose tissue, the primary sites of weight loss due to cancer cachexia.

Creatine modulates cellular energy metabolism and protects against cancer cachexia-associated muscle wasting

Cancer cachexia is a multifactorial syndrome defined by progressive loss of body weight with specific depletion of skeletal muscle and adipose tissue. Since there are no FDA-approved drugs that are available, nutritional intervention is recommended as a supporting therapy. Creatine supplementation has an ergogenic effect in various types of sports training, but the regulatory effects of creatine supplementation in cancer cachexia remain unknown. In this study, we investigated the impact of creatine supplementation on cachectic weight loss and muscle loss protection in a tumor-bearing cachectic mouse model, and the underlying molecular mechanism of body weight protection was further assessed. We observed decreased serum creatine levels in patients with cancer cachexia, and the creatine content in skeletal muscle was also significantly decreased in cachectic skeletal muscle in the C26 tumor-bearing mouse model. Creatine supplementation protected against cancer cachexia-associated body weight loss and muscle wasting and induced greater improvements in grip strength. Mechanistically, creatine treatment altered the dysfunction and morphological abnormalities of mitochondria, thus protecting against cachectic muscle wasting by inhibiting the abnormal overactivation of the ubiquitin proteasome system (UPS) and autophagic lysosomal system (ALS). In addition, electron microscopy revealed that creatine supplementation alleviated the observed increase in the percentage of damaged mitochondria in C26 mice, indicating that nutritional intervention with creatine supplementation effectively counteracts mitochondrial dysfunction to mitigate muscle loss in cancer cachexia. These results uncover a previously uncharacterized role for creatine in cachectic muscle wasting by modulating cellular energy metabolism to reduce the level of muscle cell atrophy.

Ginsenoside Rd ameliorates muscle wasting by suppressing the signal transducer and activator of transcription 3 pathway

BACKGROUND

The effects of some drugs, aging, cancers, and other diseases can cause muscle wasting. Currently, there are no effective drugs for treating muscle wasting. In this study, the effects of ginsenoside Rd (GRd) on muscle wasting were studied.

METHODS

Tumour necrosis factor-alpha (TNF-α)/interferon-gamma (IFN-γ)-induced myotube atrophy in mouse C2C12 and human skeletal myoblasts (HSkM) was evaluated based on cell thickness. Atrophy-related signalling, reactive oxygen species (ROS) level, mitochondrial membrane potential, and mitochondrial number were assessed. GRd (10 mg/kg body weight) was orally administered to aged mice (23-24 months old) and tumour-bearing (Lewis lung carcinoma [LLC1] or CT26) mice for 5 weeks and 16 days, respectively. Body weight, grip strength, inverted hanging time, and muscle weight were assessed. Histological analysis was also performed to assess the effects of GRd. The evolutionary chemical binding similarity (ECBS) approach, molecular docking, Biacore assay, and signal transducer and activator of transcription (STAT) 3 reporter assay were used to identify targets of GRd.

RESULTS

GRd significantly induced hypertrophy in the C2C12 and HSkM myotubes (average diameter 50.8 ± 2.6% and 49.9% ± 3.7% higher at 100 nM, vs. control, P ≤ 0.001). GRd treatment ameliorated aging- and cancer-induced (LLC1 or CT26) muscle atrophy in mice, which was evidenced by significant increases in grip strength, hanging time, muscle mass, and muscle tissue cross-sectional area (1.3-fold to 4.6-fold, vs. vehicle, P ≤ 0.05; P ≤ 0.01; P ≤ 0.001). STAT3 was found to be a possible target of GRd by the ECBS approach and molecular docking assay. Validation of direct interaction between GRd and STAT3 was confirmed through Biacore analysis. GRd also inhibited STAT3 phosphorylation and STAT3 reporter activity, which led to the inhibition of STAT3 nuclear translocation and the suppression of downstream targets of STAT3, such as atrogin-1, muscle-specific RING finger protein (MuRF-1), and myostatin (MSTN) (29.0 ± 11.2% to 84.3 ± 30.5%, vs. vehicle, P ≤ 0.05; P ≤ 0.01; P ≤ 0.001). Additionally, GRd scavenged ROS (91.7 ± 1.4% reduction at 1 nM, vs. vehicle, P ≤ 0.001), inhibited TNF-α-induced dysregulation of ROS level, and improved mitochondrial integrity (P ≤ 0.05; P ≤ 0.01; P ≤ 0.001).

CONCLUSIONS

GRd ameliorates aging- and cancer-induced muscle wasting. Our findings suggest that GRd may be a novel therapeutic agent or adjuvant for reversing muscle wasting.

Heterocyclic Compounds as Hsp90 Inhibitors: A Perspective on Anticancer Applications

Heat shock proteins (Hsps) have garnered special attention in cancer therapy as molecular chaperones with regulatory/mediatory effects on folding, maintenance/stability, maturation, and conformation of proteins as well as their effects on prevention of protein aggregation. Hsp90 ensures the stability of various client proteins needed for the growth of cells or the survival of tumor cells; therefore, they are overexpressed in tumor cells and play key roles in carcinogenesis. Accordingly, Hsp90 inhibitors are recognized as attractive therapeutic agents for investigations pertaining to tumor suppression. Natural Hsp90 inhibitors comprising geldanamycin (GM), reclaimed analogs of GM including 17-AAG and DMAG, and radicicol, a natural macrocyclic antifungal, are among the first potent Hsp90 inhibitors. Herein, recently synthesized heterocyclic compounds recognized as potent Hsp90 inhibitors are reviewed along with the anticancer effects of heterocyclic compounds, comprising purine, pyrazole, triazine, quinolines, coumarin, and isoxazoles molecules.

Muscle and Bone Defects in Metastatic Disease

PURPOSE OF REVIEW

The present review addresses most recently identified mechanisms implicated in metastasis-induced bone resorption and muscle-wasting syndrome, known as cachexia.

RECENT FINDINGS

Metastatic disease in bone and soft tissues is often associated with skeletal muscle defects. Recent studies have identified a number of secreted molecules and extracellular vesicles that contribute to cancer cell growth and metastasis leading to bone destruction and muscle atrophy. In addition, alterations in muscle microenvironment including dysfunctions in hepatic and mitochondrial metabolism have been implicated in cancer-induced regeneration defect and muscle loss. Moreover, we review novel in vitro and animal models including promising new drug candidates for bone metastases and cancer cachexia. Preservation of bone health could be highly beneficial for maintaining muscle mass and function. Therefore, a better understanding of molecular pathways implicated in bone and muscle crosstalk in metastatic disease may provide new insights and identify new strategies to improve current anticancer therapeutics.

2-Deoxy-D-glucose Alleviates Cancer Cachexia-Induced Muscle Wasting by Enhancing Ketone Metabolism and Inhibiting the Cori Cycle

Cachexia is characterized by progressive weight loss accompanied by the loss of specific skeletal muscle and adipose tissue. Increased lactate production, either due to the Warburg effect from tumors or accelerated glycolysis effects from cachectic muscle, is the most dangerous factor for cancer cachexia. This study aimed to explore the efficiency of 2-deoxy-D-glucose (2-DG) in blocking Cori cycle activity and its therapeutic effect on cachexia-associated muscle wasting. A C26 adenocarcinoma xenograft model was used to study cancer cachectic metabolic derangements. Tumor-free lean mass, hindlimb muscle morphology, and fiber-type composition were measured after in vivo 2-DG administration. Activation of the ubiquitin-dependent proteasome pathway (UPS) and autophagic–lysosomal pathway (ALP) was further assessed. The cachectic skeletal muscles of tumor-bearing mice exhibited altered glucose and lipid metabolism, decreased carbohydrate utilization, and increased lipid β-oxidation. Significantly increased gluconeogenesis and decreased ketogenesis were observed in cachectic mouse livers. 2-DG significantly ameliorated cancer cachexia-associated muscle wasting and decreased cachectic-associated lean mass levels and fiber cross-sectional areas. 2-DG inhibited protein degradation-associated UPS and ALP, increased ketogenesis in the liver, and promoted ketone metabolism in skeletal muscle, thus enhancing mitochondrial bioenergetic capacity. 2-DG effectively prevents muscle wasting by increasing ATP synthesis efficiency via the ketone metabolic pathway and blocking the abnormal Cori cycle.

Cancer Cachexia: Signaling and Transcriptional Regulation of Muscle Catabolic Genes

Simple Summary

An uncontrollable loss in the skeletal muscle of cancer patients which leads to a significant reduction in body weight is clinically referred to as cancer cachexia (CC). While factors derived from the tumor environment which trigger various signaling pathways have been identified, not much progress has been made clinically to effectively prevent muscle loss. Deeper insights into the transcriptional and epigenetic regulation of muscle catabolic genes may shed light on key regulators which can be targeted to develop new therapeutic avenues.

Abstract

Cancer cachexia (CC) is a multifactorial syndrome characterized by a significant reduction in body weight that is predominantly caused by the loss of skeletal muscle and adipose tissue. Although the ill effects of cachexia are well known, the condition has been largely overlooked, in part due to its complex etiology, heterogeneity in mediators, and the involvement of diverse signaling pathways. For a long time, inflammatory factors have been the focus when developing therapeutics for the treatment of CC. Despite promising pre-clinical results, they have not yet advanced to the clinic. Developing new therapies requires a comprehensive understanding of how deregulated signaling leads to catabolic gene expression that underlies muscle wasting. Here, we review CC-associated signaling pathways and the transcriptional cascade triggered by inflammatory cytokines. Further, we highlight epigenetic factors involved in the transcription of catabolic genes in muscle wasting. We conclude with reflections on the directions that might pave the way for new therapeutic approaches to treat CC.

Tumor cell anabolism and host tissue catabolism-energetic inefficiency during cancer cachexia

Cancer-associated cachexia (CC) is a pathological condition characterized by sarcopenia, adipose tissue depletion, and progressive weight loss. CC is driven by multiple factors such as anorexia, excessive catabolism, elevated energy expenditure by growing tumor mass, and inflammatory mediators released by cancer cells and surrounding tissues. In addition, endocrine system, systemic metabolism, and central nervous system (CNS) perturbations in combination with cachexia mediators elicit exponential elevation in catabolism and reduced anabolism in skeletal muscle, adipose tissue, and cardiac muscle. At the molecular level, mechanisms of CC include inflammation, reduced protein synthesis, and lipogenesis, elevated proteolysis and lipolysis along with aggravated toxicity and complications of chemotherapy. Furthermore, CC is remarkably associated with intolerance to anti-neoplastic therapy, poor prognosis, and increased mortality with no established standard therapy. In this context, we discuss the spatio-temporal changes occurring in the various stages of CC and highlight the imbalance of host metabolism. We provide how multiple factors such as proteasomal pathways, inflammatory mediators, lipid and protein catabolism, glucocorticoids, and in-depth mechanisms of interplay between inflammatory molecules and CNS can trigger and amplify the cachectic processes. Finally, we highlight current diagnostic approaches and promising therapeutic interventions for CC.