Muscle Wasting In Cancer Cachexia Research Articles

Mitochondrial fusion and altered beta-oxidation drive muscle wasting in a Drosophila cachexia model

Cancer cachexia is a tumour-induced wasting syndrome, characterised by extreme loss of skeletal muscle. Defective mitochondria can contribute to muscle wasting; however, the underlying mechanisms remain unclear. Using a Drosophila larval model of cancer cachexia, we observed enlarged and dysfunctional muscle mitochondria. Morphological changes were accompanied by upregulation of beta-oxidation proteins and depletion of muscle glycogen and lipid stores. Muscle lipid stores were also decreased in Colon-26 adenocarcinoma mouse muscle samples, and expression of the beta-oxidation gene CPT1A was negatively associated with muscle quality in cachectic patients. Mechanistically, mitochondrial defects result from reduced muscle insulin signalling, downstream of tumour-secreted insulin growth factor binding protein (IGFBP) homologue ImpL2. Strikingly, muscle-specific inhibition of Forkhead box O (FOXO), mitochondrial fusion, or beta-oxidation in tumour-bearing animals preserved muscle integrity. Finally, dietary supplementation with nicotinamide or lipids, improved muscle health in tumour-bearing animals. Overall, our work demonstrates that muscle FOXO, mitochondria dynamics/beta-oxidation and lipid utilisation are key regulators of muscle wasting in cancer cachexia.

Erratum for the Research Article "Perturbed BMP signaling and denervation promote muscle wasting in cancer cachexia" by R. Sartori et al.

Erratum for the Research Article "Perturbed BMP signaling and denervation promote muscle wasting in cancer cachexia" by R. Sartori et al.

Mitophagy-mediated inflammation and oxidative stress contribute to muscle wasting in cancer cachexia

Mitophagy-mediated inflammation and oxidative stress contribute to muscle wasting in cancer cachexia

β‑carotene attenuates muscle wasting in cancer cachexia by regulating myogenesis and muscle atrophy.

Cancer cachexia is a metabolic disease involving multiple organs, which is accompanied by the depletion of muscle tissue and is associated with ~20% of cancer‑related deaths. Muscle wasting is a critical factor in cancer cachexia. β‑carotene (BC) has been shown to increase muscle mass and hypertrophy in healthy mice. However, its effects on muscle tissue dysregulation in cancer cachexia have yet to be studied. In the present study, 5‑week‑old male C57BL/6J mice were injected with 1x106 Lewis lung carcinoma (LLC) cells to induce cancer cachexia; then the mice were administered BC (4or8mg/kg) for 22days to assess its effects on muscle atrophy in the gastrocnemius muscles. The effects of BC on inflammatory cytokines, myogenesis and muscle atrophy were evaluated using C2C12 myotubes treated with LLC‑conditioned media. BC supplementation significantly suppressed tumor growth, inflammatory cytokines, and hepatic gluconeogenesis in the LLC‑induced cancer cachexia mouse model, while also improving muscle weight and grip strength. These effects are considered to be mediated by the PI3K/Akt pathway and through regulation of muscle atrophy. Moreover, BC treatment was associated with the recovery of LLC‑conditioned media‑induced muscle differentiation deficits and muscle atrophy in C2C12 myotubes. These findings indicate BC as a potential novel therapeutic agent for cancer cachexia.

Exploring the Therapeutic Potential of Ethyl 3-Hydroxybutyrate in Alleviating Skeletal Muscle Wasting in Cancer Cachexia.

Cachexia (CAC) is a debilitating metabolic syndrome. Although dietary interventions are attractive, long-term adherence to specific diets is difficult to maintain and can lead to systemic side effects. Ethyl 3-hydroxybutyrate (EHB) is a commonly used food additive found in wine and Tribolium castaneum. In this study, we investigated the effects of EHB administration in cachectic mice. After a single intraperitoneal injection of EHB into mice, 3-hydroxybutyrate (3-HB) levels were significantly increased in the serum and gastrocnemius of mice. The administration of EHB alleviated cachexia-related symptoms, ameliorated skeletal muscle atrophy, and improved survival in cachectic mice. In addition, the supplementation of cachectic mice with 3-HB by EHB administration significantly reduced tumor weights, indicating the anti-tumor effects of 3-HB. Remarkably, the addition of 3-HB to the culture medium significantly attenuated the C2C12 myotube atrophy induced by the culture supernatant of CT26 cell lines, highlighting its potential to counteract the destructive effects of tumor-derived elements on muscle tissue. NMR-based metabolomics analysis provided insights into the underlying mechanisms and revealed that the anti-cachexia effects of 3-HB treatment can be attributed to three key mechanisms: the promotion of the TCA cycle and the attenuation of proteolysis, the promotion of protein synthesis and the improvement of metabolic homeostasis, and a reduction in inflammation and an enhancement of the antioxidant capacity. This study provided compelling evidence for the protective effects of 3-HB treatment on the cachectic gastrocnemius and highlighted the efficacy of EHB administration as a ketone supplementation approach to achieve nutritional ketosis without the need for dietary restriction.

Cucurbitacin IIb attenuates cancer cachexia induced skeletal muscle atrophy by regulating the IL-6/STAT3/FoxO signaling pathway.

The main features of cancer cachexia include skeletal muscle atrophy, which can significantly reduce the quality of life of patients. Clinical treatment of cancer cachexia is mainly based on nutritional therapy and physical exercise; medication only improves appetite but does not reverse the symptoms of skeletal muscle wasting. In this work, we systematically studied the underlying molecular mechanisms by which cucurbitacin IIb (CuIIb) ameliorates muscle wasting in cancer cachexia both in vitro and in vivo. CuIIb significantly ameliorated the chief features of cancer cachexia in vivo, alleviating weight loss, food intake, muscle wasting, adipose tissue depletion, and organ weight reductions. In vitro, CuIIb (10 and 20 μM) dose-dependently attenuated conditioned medium (CM)-induced C2C12 myotube atrophy. Collectively, our findings demonstrated that CuIIb prevented the upregulation of the E3 ubiquitin ligase muscle atrophy Fbox protein (MAFbx), myosin heavy chain (MyHC), and myogenin (MyoG) and impacted protein synthesis and degradation. In addition, CuIIb decreased the phosphorylation of Tyr705 in STAT3 by regulating the IL-6/STAT3/FoxO pathway to reduce skeletal muscle atrophy in cancer cachexia.

3D bioprinted functional skeletal muscle models have potential applications for studies of muscle wasting in cancer cachexia

Acquired muscle diseases such as cancer cachexia are responsible for the poor prognosis of many patients suffering from cancer. In vitro models are needed to study the underlying mechanisms of those pathologies. Extrusion bioprinting is an emerging tool to emulate the aligned architecture of fibers while implementing additive manufacturing techniques in tissue engineering. However, designing bioinks that reconcile the rheological needs of bioprinting and the biological requirements of muscle tissue is a challenging matter. Here we formulate a biomaterial with dual crosslinking to modulate the physical properties of bioprinted models. We design 3D bioprinted muscle models that resemble the mechanical properties of native tissue and show improved proliferation and high maturation of differentiated myotubes suggesting that the GelMA-AlgMA-Fibrin biomaterial possesses myogenic properties. The electrical stimulation of the 3D model confirmed the contractile capability of the tissue and enhanced the formation of sarcomeres. Regarding the functionality of the models, they served as platforms to recapitulate skeletal muscle diseases such as muscle wasting produced by cancer cachexia. The genetic expression of 3D models demonstrated a better resemblance to the muscular biopsies of cachectic mouse models. Altogether, this biomaterial is aimed to fabricate manipulable skeletal muscle in vitro models in a non-costly, fast and feasible manner.

Abstract 369: Gemcitabine nab-paclitaxel combination with DMAPT in PDAC cachexia

Abstract Background: Cachexia is the progressive, unintentional wasting of muscle and adipose tissue caused by tumors. Cancer cachexia affects >80% of patients with pancreatic ductal adenocarcinoma (PDAC). Certain chemotherapy regimens cause debilitation in patients and muscle and fat wasting in mouse models. Gemcitabine with nab-paclitaxel (GemNP) is a first line treatment for PDAC. Whether GemNP promotes cachexia is unknown. Muscle wasting in cancer cachexia has been functionally linked to NF-κB, which can be induced by chemotherapies and is active in PDAC tumors. Among other functions, NF-κB induces expression of Interleukin-6 (IL-6), a major mediator of cancer cachexia. DMAPT is a small molecule NF-κB inhibitor. In prior work, DMAPT plus Gem reduced tumor burden in a genetic model of pancreatic cancer and separately, prevented muscle wasting in a genetic model of mammary cancer. Therefore, the purpose of our study was to determine whether GemNP promotes cachexia and whether DMAPT could reduce tumor burden and/or cachexia in PDAC, potentially through reducing IL-6 expression. Methods: In our in vitro model, conditioned media (CM) from KPC pancreatic cancer cells derived from the KrasG12D;Trp53R172H;Pdx1-Cre mouse, induces wasting of C2C12 myotubes. Thus, myotubes were treated with 50% KPC-CM or control CM and supplemented with 0, 5, or 10uM DMAPT for 48hrs. For in vivo modeling of PDAC cachexia, 12-week-old male C57BL/6J mice were orthotopically implanted with 5x104 KPC cells or KPC cells deleted for IL6 (KPC-IL6KO) cells; controls underwent sham surgery. Starting on day 4, every 6 days tumor-bearing mice were given 120 mg/kg gemcitabine and 10 mg/kg nab-paclitaxel (GemNP) for four rounds, then gemcitabine only for subsequent rounds, with or without 100mg/kg DMAPT (by gavage 5 days/week). Controls received vehicle only. Results: DMAPT prevented atrophy in KPC-CM treated myotubes. In vivo, GemNP increased median survival, to 23.5d in KPC + GemNP mice versus 17d in untreated KPC mice (P<0.001). GemNP + DMAPT increased survival (25d) compared to untreated KPC (P<0.001), but was similar to KPC + GemNP alone (P=0.693). There were no differences in tumor mass at euthanasia. All KPC groups lost significant body weight and fat mass compared to sham controls. In mice with KPC IL-6KO tumors, GemNP increased survival, with median survival of 39d in KPC-IL6KO + GemNP mice compared with 30d in untreated KPC-IL6KO (P<0.001). GemNP + DMAPT increased survival (35 d in KPC IL-6KO) compared to untreated KPC-IL6KO (P<0.001), but was similar to KPC IL-6KO + GemNP (P=0.276). There was a trend for GemNP + DMAPT to have smaller KPC-IL6KO tumors compared to GemNP (p=0.055). Conclusion: Regardless of IL-6 expression from tumor cells, treatment with GemNP improved survival in orthotopic PDAC without exacerbating cachexia. DMAPT did not extend survival above GemNP alone. Despite promising in vitro data and prior published work, DMAPT was not efficacious in reducing tumor growth or treating PDAC cachexia in this model. Citation Format: Brittany Counts, Sephora Jean, Reggie Wang, Teresa Zimmers. Gemcitabine nab-paclitaxel combination with DMAPT in PDAC cachexia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 369.

Mitophagy-mediated inflammation and oxidative stress contribute to muscle wasting in cancer cachexia.

Cancer cachexia is commonly seen in patients with malignant tumors, which usually leads to poor life quality and negatively affects long-term prognosis and survival. Mitochondria dysfunction and enhanced autophagy are well-established to play an important role in skeletal muscle wasting. However, whether mitophagy is engaged in the pathogenesis of cancer cachexia requires further investigation. This study comprised a clinical study and animal experimentation. Clinical data such as CT images and laboratory results were obtained and analyzed. Then mice model of cancer cachexia and mitophagy inhibition were established. Data including skeletal muscle mass and function, mitochondria structure and function, inflammatory factors as well as ROS concentration. Mitophagy was enhanced in cancer cachexia patients with increased inflammatory factors. Greater disruption of skeletal muscle fiber and mitochondria structure were seen in cancer cachexia, with a higher level of inflammatory factors and ROS expression in skeletal muscle. Meanwhile, ATP production was undermined, indicating a close relationship with mitophagy, inflammation, and oxidative stress in the skeletal muscle of cancer cachexia mice models. In conclusion, mitophagy is activated in cancer cachexia and may play a role in skeletal muscle atrophy, and inflammation and oxidative stress might participate in mitophagy-related skeletal muscle injury.

Role of the Gut Microbiome in Skeletal Muscle Physiology and Pathophysiology.

This review aims to summarize the recent findings about the contribution of the gut microbiome to muscle pathophysiology and discuss molecular pathways that may be involved in such process. Related findings in the context of cancer cachexia are outlined. Many bacterial metabolites have been reported to exert a beneficial or detrimental impact on muscle physiology. Most of the evidence concentrates on short-chain fatty acids (SCFAs), with an emerging role for bile acids, bacterial amino acid metabolites (bAAms), and bacterial polyphenol metabolites. Other molecular players worth considering include cytokines, hormones, lipopolysaccharides, and quorum sensing molecules. The current literature clearly establishes the ability for the gut microbiome to modulate muscle function and mass. The understanding of the mechanisms underlying this gut-muscle axis may lead to the delivery of novel therapeutic tools to tackle muscle wasting in cancer cachexia, chronic kidney disease, liver fibrosis, and age-related sarcopenia.

Combination therapy with anamorelin and a myostatin inhibitor is advantageous for cancer cachexia in a mouse model.

Cancer cachexia is a multifactorial disease that causes continuous skeletal muscle wasting. Thereby, it seems to be a key determinant of cancer‐related death. Although anamorelin, a ghrelin receptor agonist, has been approved in Japan for the treatment of cachexia, few medical treatments for cancer cachexia are currently available. Myostatin (MSTN)/growth differentiation factor 8, which belongs to the transforming growth factor‐β family, is a negative regulator of skeletal muscle mass, and inhibition of MSTN signaling is expected to be a therapeutic target for muscle‐wasting diseases. Indeed, we have reported that peptide‐2, an MSTN‐inhibiting peptide from the MSTN prodomain, alleviates muscle wasting due to cancer cachexia. Herein, we evaluated the therapeutic benefit of myostatin inhibitory D‐peptide‐35 (MID‐35), whose stability and activity were more improved than those of peptide‐2 in cancer cachexia model mice. The biologic effects of MID‐35 were better than those of peptide‐2. Intramuscular administration of MID‐35 effectively alleviated skeletal muscle atrophy in cachexia model mice, and the combination therapy of MID‐35 with anamorelin increased food intake and maximized grip strength, resulting in longer survival. Our results suggest that this combination might be a novel therapeutic tool to suppress muscle wasting in cancer cachexia.

Perturbed BMP signaling and denervation promote muscle wasting in cancer cachexia

Most patients with advanced solid cancers exhibit features of cachexia, a debilitating syndrome characterized by progressive loss of skeletal muscle mass and strength. Because the underlying mechanisms of this multifactorial syndrome are incompletely defined, effective therapeutics have yet to be developed. Here, we show that diminished bone morphogenetic protein (BMP) signaling is observed early in the onset of skeletal muscle wasting associated with cancer cachexia in mouse models and in patients with cancer. Cancer-mediated factors including Activin A and IL-6 trigger the expression of the BMP inhibitor Noggin in muscle, which blocks the actions of BMPs on muscle fibers and motor nerves, subsequently causing disruption of the neuromuscular junction (NMJ), denervation, and muscle wasting. Increasing BMP signaling in the muscles of tumor-bearing mice by gene delivery or pharmacological means can prevent muscle wasting and preserve measures of NMJ function. The data identify perturbed BMP signaling and denervation of muscle fibers as important pathogenic mechanisms of muscle wasting associated with tumor growth. Collectively, these findings present interventions that promote BMP-mediated signaling as an attractive strategy to counteract the loss of functional musculature in patients with cancer.

Amiloride ameliorates muscle wasting in cancer cachexia through inhibiting tumor-derived exosome release

BackgroundCancer cachexia (CAC) reduces patient survival and quality of life. Developments of efficient therapeutic strategies are required for the CAC treatments. This long-term process could be shortened by the drug-repositioning approach which exploits old drugs approved for non-cachexia disease. Amiloride, a diuretic drug, is clinically used for treatments of hypertension and edema due to heart failure. Here, we explored the effects of the amiloride treatment for ameliorating muscle wasting in murine models of cancer cachexia.MethodsThe CT26 and LLC tumor cells were subcutaneously injected into mice to induce colon cancer cachexia and lung cancer cachexia, respectively. Amiloride was intraperitoneally injected daily once tumors were formed. Cachexia features of the CT26 model and the LLC model were separately characterized by phenotypic, histopathologic and biochemical analyses. Plasma exosomes and muscle atrophy-related proteins were quantitatively analyzed. Integrative NMR-based metabolomic and transcriptomic analyses were conducted to identify significantly altered metabolic pathways and distinctly changed metabolism-related biological processes in gastrocnemius.ResultsThe CT26 and LLC cachexia models displayed prominent cachexia features including decreases in body weight, skeletal muscle, adipose tissue, and muscle strength. The amiloride treatment in tumor-bearing mice distinctly alleviated muscle atrophy and relieved cachexia-related features without affecting tumor growth. Both the CT26 and LLC cachexia mice showed increased plasma exosome densities which were largely derived from tumors. Significantly, the amiloride treatment inhibited tumor-derived exosome release, which did not obviously affect exosome secretion from non-neoplastic tissues or induce observable systemic toxicities in normal healthy mice. Integrative-omics revealed significant metabolic impairments in cachectic gastrocnemius, including promoted muscular catabolism, inhibited muscular protein synthesis, blocked glycolysis, and impeded ketone body oxidation. The amiloride treatment evidently improved the metabolic impairments in cachectic gastrocnemius.ConclusionsAmiloride ameliorates cachectic muscle wasting and alleviates cancer cachexia progression through inhibiting tumor-derived exosome release. Our results are beneficial to understanding the underlying molecular mechanisms, shedding light on the potentials of amiloride in cachexia therapy.

The mechanism by which noncoding RNAs regulate muscle wasting in cancer cachexia.

Cancer cachexia (CC) is a complex metabolic syndrome that accelerates muscle wasting and affects up to 80% of patients with cancer; however, timely diagnostic methods and effective cures are lacking. Although a considerable number of studies have focused on the mechanism of CC-induced muscle atrophy, few novel therapies have been applied in the last decade. In recent years, noncoding RNAs (ncRNAs) have attracted great attention as many differentially expressed ncRNAs in cancer cachectic muscles have been reported to participate in the inhibition of myogenesis and activation of proteolysis. In addition, extracellular vesicles (EVs), which function as ncRNA carriers in intercellular communication, are closely involved in changing ncRNA expression profiles in muscle and promoting the development of muscle wasting; thus, EV-related ncRNAs may represent potential therapeutic targets. This review comprehensively describes the process of ncRNA transmission through EVs and summarizes the pathways and targets of ncRNAs that lead to CC-induced muscle atrophy.

Reduced rDNA transcription diminishes skeletal muscle ribosomal capacity and protein synthesis in cancer cachexia.

Muscle wasting in cancer is associated with deficits in protein synthesis, yet, the mechanisms underlying this anabolic impairment remain poorly understood. The capacity for protein synthesis is mainly determined by the abundance of muscle ribosomes, which is in turn regulated by transcription of the ribosomal (r)RNA genes (rDNA). In this study, we investigated whether muscle loss in a preclinical model of ovarian cancer is associated with a reduction in ribosomal capacity and was a consequence of impaired rDNA transcription. Tumor bearing resulted in a significant loss in gastrocnemius muscle weight and protein synthesis capacity, and was consistent with a significant reduction in rDNA transcription and ribosomal capacity. Despite the induction of the ribophagy receptor NUFIP1 mRNA and the loss of NUFIP1 protein, in vitro studies revealed that while inhibition of autophagy rescued NUFIP1, it did not prevent the loss of rRNA. Electrophoretic analysis of rRNA fragmentation from both in vivo and in vitro models showed no evidence of endonucleolytic cleavage, suggesting that rRNA degradation may not play a major role in modulating muscle ribosome abundance. Our results indicate that in this model of ovarian cancer-induced cachexia, the ability of skeletal muscle to synthesize protein is compromised by a reduction in rDNA transcription and consequently a lower ribosomal capacity. Thus, impaired ribosomal production appears to play a key role in the anabolic deficits associated with muscle wasting in cancer cachexia.

Quercetin supplementation attenuates muscle wasting in cancer-associated cachexia in mice

BACKGROUND: Quercetin is a flavonoid with reported antioxidant, anti-inflammatory and anti-aging effects, and may limit muscle wasting in cancer cachexia. OBJECTIVE: To investigate the effect of quercetin on muscle wasting in the murine C26 cancer-cachexia model and assess the feasibility of non-invasive micro-CT analysis of skeletal muscle. MATERIALS AND METHODS: Custom CRM(P) diets supplemented with 250 mg/kg quercetin (Q) were obtained. Thirty CD2F1 mice were equally randomized to non-tumor-bearing (NTB), C26 tumor-bearing (TB), TB + Q. All groups started their allocated diet and underwent hindlimb micro-CT. Bodyweight, food intake, and grip-strength were recorded periodically. After 21 days, repeat micro-CT was performed. Gastrocnemius (GCM) and tibialis anterior (TA) muscles were resected. mRNA expression of MuRF1, Atrogin-1, myogenin, and MyoD was determined. RESULTS: NTB and TB + Q gained 9.4% and 5.3% bodyweight respectively, TB lost 3.9%. Hind limb skeletal muscle volume remained stable for NTB and TB + Q, whereas TB decreased from 242.0 mm3 to 212.8 mm3. Mean GCM muscle weight was 175.2 mg (NTB), 171.3 mg (TB + Q) versus 125.5 mg (TB). A tendency towards decreased expression of atrogin-1 and MuRF1 was observed in TB + Q. CONCLUSION: Dietary quercetin supplementation limits bodyweight loss and muscle wasting in the C26-cancer-associated cachexia model.

MicroRNAs in Skeletal Muscle and Hints on Their Potential Role in Muscle Wasting During Cancer Cachexia.

Cancer-associated cachexia is a heterogeneous, multifactorial syndrome characterized by systemic inflammation, unintentional weight loss, and profound alteration in body composition. The main feature of cancer cachexia is represented by the loss of skeletal muscle tissue, which may or may not be accompanied by significant adipose tissue wasting. Such phenotypic alteration occurs as the result of concomitant increased myofibril breakdown and reduced muscle protein synthesis, actively contributing to fatigue, worsening of quality of life, and refractoriness to chemotherapy. According to the classical view, this condition is primarily triggered by interactions between specific tumor-induced pro-inflammatory cytokines and their cognate receptors expressed on the myocyte membrane. This causes a shift in gene expression of muscle cells, eventually leading to a pronounced catabolic condition and cell death. More recent studies, however, have shown the involvement of regulatory non-coding RNAs in the outbreak of cancer cachexia. In particular, the role exerted by microRNAs is being widely addressed, and several mechanistic studies are in progress. In this review, we discuss the most recent findings concerning the role of microRNAs in triggering or exacerbating muscle wasting in cancer cachexia, while mentioning about possible roles played by long non-coding RNAs and ADAR-mediated miRNA modifications.

Abstract IA-17: Mechanisms of pancreatic cancer-induced cachexia

Abstract Cachexia is a debilitating syndrome that results in severe, involuntary weight loss due to the depletion of skeletal muscle mass. Currently, no effective therapy exists to combat this malignant disorder. For pancreatic cancer, 85% of patients lose on average 14% of their pre-illness weight, and cachexia dramatically limits their ability to tolerate surgery, chemo- or radiotherapy. New therapies will likely evolve from an enhanced understanding of the mechanisms leading to muscle wasting and tumor development. Our laboratory has been examining the role of the NF-κB signaling pathway in tumorigenesis for several decades and that interest led us to discover the connection between NF-κB and muscle wasting in cancer cachexia and more recently in pancreatic cancer. We view the pathway as playing two separate functions in pancreatic cancer-induced cachexia. The first occurs at the level of skeletal muscle, or more preciously in skeletal muscle stem cells. We have found that during cancer progression, skeletal muscle undergoes a type of injury response leading to the activation of resident stem cells to engage in a regeneration program. NF-κB is activated in these stem cells and functions to inhibit regeneration, which contributes to the overall wasting process in cachexia. New data reveal that NF-κB activity in progenitor cells also regulates a local muscle inflammatory environment that might also contribute to skeletal muscle catabolism. The mechanism of this regulation will be discussed in more details. The second function of NF-κB signaling that we are pursuing focuses in the tumor microenvironment of pancreatic cancer. Using orthotopic mouse models of pancreatic cancer, we showed that NF-κB plays a critical role in protecting tumor cells from the surveillance property of anti-tumor macrophages. This occurs through the direct transcriptional regulation of the immunosuppressive cytokine, GDF15. Interestingly, circulating levels of GDF15 are elevated in cachectic patients and recent studies indicate that this cytokine might be an attractive therapeutic target in cancer cachexia. Together, we speculate that NF-κB functions in cancer cachexia by acting in muscle stem cells to block muscle repair, as well as promoting pancreatic cancer through the production of immunosuppressive genes such as GDF15. Citation Format: Benjamin Pryce, Nivedita Ratnam, Erin E. Talbert, Mary Dilhoff, Carl R. Schmidt, David J. Wang, Denis C. Guttridge. Mechanisms of pancreatic cancer-induced cachexia [abstract]. In: Proceedings of the AACR Virtual Special Conference on Pancreatic Cancer; 2020 Sep 29-30. Philadelphia (PA): AACR; Cancer Res 2020;80(22 Suppl):Abstract nr IA-17.

Generation of reporter cell lines for factors inducing muscle wasting in cancer cachexia

Rapidly identifying cachexia-inducing factors that directly induce muscle wasting is an existing challenge. We developed two reporter cell lines that allow swift detection of such factors in blood from patients. C2C12 myoblasts were used for the establishment of reporter cells. A luciferase reporter gene, driven by promoters of wasting genes, Muscle RING-finger protein-1 (MuRF1) and Muscle Atrophy F-Box Protein (MAFbx/Atrogin-1) were used for the construction of reporter constructs. Increased expression of these genes in muscle tissue under wasting conditions was shown in vivo and in vitro. We found these reporter cell lines could detect factors associated with cancer cachexia, such as myostatin (Mstn), activin A, and TNF-α. We further investigated the capacity to directly detect a cachectic state using plasma samples from cachectic mice and cancer patients. Activation of the reporter cell lines was observed by the addition of plasma from mice with cancer cachexia and serum samples from patients with pancreatic or colorectal cancer. These results indicate that the reporter cell lines are competent as a tool for screening cachexia-inducing factors and potentially distinguishing a cachectic state induced by cancer.

JNK signaling contributes to skeletal muscle wasting and protein turnover in pancreatic cancer cachexia.

Cancer cachexia patients experience significant muscle wasting, which impairs the quality of life and treatment efficacy for patients. Skeletal muscle protein turnover is imparted by increased expression of ubiquitin-proteasome pathway components. Mitogen-activated protein kinases p38 and ERK have been shown to augment E3 ubiquitin ligase expression. Utilizing reverse-phase protein arrays, we identified pancreatic cancer cell-conditioned media-induced activation of JNK signaling in myotubes differentiated from C2C12 myoblasts. Inhibition of JNK signaling with SP600125 reduced cancer cell-conditioned media-induced myotube atrophy, myosin heavy chain protein turnover, and mRNA expression of cachexia-specific ubiquitin ligases Trim63 and Fbxo32. Furthermore, utilizing an orthotopic pancreatic cancer cachexia mouse model, we demonstrated that treatment of tumor-bearing mice with SP600125 improved longitudinal measurements of forelimb grip strength. Post-necropsy measurements demonstrated that SP600125 treatment rescued body weight, carcass weight, and gastrocnemius muscle weight loss without impacting tumor growth. JNK inhibitor treatment also rescued myofiber degeneration and reduced the muscle expression of Trim63 and Fbxo32. These data demonstrate that JNK signaling contributes to muscle wasting in cancer cachexia, and its inhibition has the potential to be utilized as an anti-cachectic therapy.