LP07 and LLC preclinical models of lung cancer induce divergent anabolic deficits and expression of pro-inflammatory effectors of muscle wasting

Anabolic deficits and divergent unfolded protein response underlie skeletal and cardiac muscle growth impairments in the Yoshida hepatoma tumor model of cancer cachexia

Cancer cachexia manifests as whole body wasting, however, the precise mechanisms governing the alterations in skeletal muscle and cardiac anabolism have yet to be fully elucidated. In this study, we explored changes in anabolic processes in both skeletal and cardiac muscles in the Yoshida AH-130 ascites hepatoma model of cancer cachexia. AH-130 tumor-bearing rats experienced significant losses in body weight, skeletal muscle, and heart mass. Skeletal and cardiac muscle loss was associated with decreased ribosomal (r)RNA, and hypophosphorylation of the eukaryotic factor 4E binding protein 1. Endoplasmic reticulum stress was evident by higher activating transcription factor mRNA in skeletal muscle and growth arrest and DNA damage-inducible protein (GADD)34 mRNA in both skeletal and cardiac muscles. Tumors provoked an increase in tissue expression of interferon-γ in the heart, while an increase in interleukin-1β mRNA was apparent in both skeletal and cardiac muscles. We conclude that compromised skeletal muscle and heart mass in the Yoshida AH-130 ascites hepatoma model involves a marked reduction translational capacity and efficiency. Furthermore, our observations suggest that endoplasmic reticulum stress and tissue production of pro-inflammatory factors may play a role in the development of skeletal and cardiac muscle wasting.

Exploring heterogeneity: a dive into preclinical models of cancer cachexia

Cancer cachexia (CC) is a multifactorial and complex syndrome experienced by up to 80% of patients with cancer and implicated in ∼40% of cancer-related deaths. Given its significant impact on patients' quality of life and prognosis, there has been a growing emphasis on elucidating the underlying mechanisms of CC using preclinical models. However, the mechanisms of cachexia appear to differ across several variables including tumor type and model and biologic variables such as sex. These differences may be exacerbated by variance in experimental approaches and data reporting. This review examines literature spanning from 2011 to March 2024, focusing on common preclinical models of CC, including Lewis Lung Carcinoma, pancreatic KPC, and colorectal colon-26 and Apcmin/+ models. Our analysis reveals considerable heterogeneity in phenotypic outcomes, and investigated mechanisms within each model, with particular attention to sex differences that may be exacerbated through methodological differences. Although searching for unified mechanisms is critical, we posit that effective treatment approaches are likely to leverage the heterogeneity presented by the tumor and pertinent biological variables to direct specific interventions. In exploring this heterogeneity, it becomes critical to consider methodological and data reporting approaches to best inform further research.

The Impact of Non-bone Metastatic Cancer on Musculoskeletal Health

PURPOSE OF REVIEW

The purpose of this review is to discuss the musculoskeletal consequences of cancer, including those that occur in the absence of bone metastases.

RECENT FINDINGS

Cancer patients frequently develop cachexia, a debilitating condition reflected by weight loss and skeletal muscle wasting. The negative effects that tumors exert on bone health represents a growing interest amongst cachexia researchers. Recent clinical and pre-clinical evidence demonstrates cancer-induced bone loss, even in the absence of skeletal metastases. Together with muscle wasting, losses in bone demonstrates the impact of cancer on the musculoskeletal system. Identifying therapeutic targets that comprehensively protect musculoskeletal health is essential to improve the quality of life in cancer patients and survivors. IL-6, RANKL, PTHrP, sclerostin, and TGF-β superfamily members represent potential targets to counteract cachexia. However, more research is needed to determine the efficacy of these targets in protecting both skeletal muscle and bone.

Cancer-associated muscle weakness - From triggers to molecular mechanisms

Skeletal muscle weakness is a debilitating consequence of many malignancies. Muscle weakness has a negative impact on both patient wellbeing and outcome in a range of cancer types and can be the result of loss of muscle mass (i.e. muscle atrophy, cachexia) and occur independently of muscle atrophy or cachexia. There are multiple cancer specific triggers that can initiate the progression of muscle weakness, including the malignancy itself and the tumour environment, as well as chemotherapy, radiotherapy and malnutrition. This can induce weakness via different routes: 1) impaired intrinsic capacity (i.e., contractile dysfunction and intramuscular impairments in excitation-contraction coupling or crossbridge cycling), 2) neuromuscular disconnection and/or 3) muscle atrophy. The mechanisms that underlie these pathways are a complex interplay of inflammation, autophagy, disrupted protein synthesis/degradation, and mitochondrial dysfunction. The current lack of therapies to treat cancer-associated muscle weakness highlight the critical need for novel interventions (both pharmacological and non-pharmacological) and mechanistic insight. Moreover, most research in the field has placed emphasis on directly improving muscle mass to improve muscle strength. However, accumulating evidence suggests that loss of muscle function precedes atrophy. This review primarily focuses on cancer-associated muscle weakness, independent of cachexia, and provides a solid background on the underlying mechanisms, methodology, current interventions, gaps in knowledge, and limitations of research in the field. Moreover, we have performed a mini-systematic review of recent research into the mechanisms behind muscle weakness in specific cancer types, along with the main pathways implicated.

Molecular Mechanisms of Cachexia: A Review

Cachexia is a condition characterized by substantial loss of body weight resulting from the depletion of skeletal muscle and adipose tissue. A considerable fraction of patients with advanced cancer, particularly those who have been diagnosed with pancreatic or gastric cancer, lung cancer, prostate cancer, colon cancer, breast cancer, or leukemias, are impacted by this condition. This syndrome manifests at all stages of cancer and is associated with an unfavorable prognosis. It heightens the susceptibility to surgical complications, chemotherapy toxicity, functional impairments, breathing difficulties, and fatigue. The early detection of patients with cancer cachexia has the potential to enhance both their quality of life and overall survival rates. Regarding this matter, blood biomarkers, although helpful, possess certain limitations and do not exhibit universal application. Additionally, the available treatment options for cachexia are currently limited, and there is a lack of comprehensive understanding of the underlying molecular pathways associated with this condition. Thus, this review aims to provide an overview of molecular mechanisms associated with cachexia and potential therapeutic targets for the development of effective treatments for this devastating condition.

Does the blunted stimulation of skeletal muscle protein synthesis by aging in response to mechanical load result from impaired ribosome biogenesis?

Age-related loss of skeletal muscle mass leads to a reduction of strength. It is likely due to an inadequate stimulation of muscle protein synthesis (MPS) in response to anabolic stimuli, such as mechanical load. Ribosome biogenesis is a major determinant of translational capacity and is essential for the control of muscle mass. This mini-review aims to put forth the hypothesis that ribosome biogenesis is impaired by aging in response to mechanical load, which could contribute to the age-related anabolic resistance and progressive muscle atrophy. Recent animal studies indicate that aging impedes muscle hypertrophic response to mechanical overload. This is associated with an impaired transcription of ribosomal DNA (rDNA) by RNA polymerase I (Pol I), a limited increase in total RNA concentration, a blunted activation of AKT/mTOR pathway, and an increased phosphorylation of AMPK. In contrast, an age-mediated impairment of ribosome biogenesis is unlikely in response to electrical stimulations. In human, the hypertrophic response to resistance exercise training is diminished with age. This is accompanied by a deficit in long-term MPS and an absence of increased total RNA concentration. The results addressing the acute response to resistance exercise suggest an impaired Pol I-mediated rDNA transcription and attenuated activation/expression of several upstream regulators of ribosome biogenesis in muscles from aged individuals. Altogether, emerging evidence indicates that impaired ribosome biogenesis could partly explain age-related anabolic resistance to mechanical load, which may ultimately contribute to progressive muscle atrophy. Future research should develop more advanced molecular tools to provide in-depth analysis of muscle ribosome biogenesis.

Metastatic or xenograft colorectal cancer models induce divergent anabolic deficits and expression of pro-inflammatory effectors of muscle wasting in a tumor-type-dependent manner

We investigated the impact of tumor burden on muscle wasting in metastatic (m) and xenograft (x) models of colorectal cancer (CRC). Male Nod SCID γ and CD2F1 mice were injected subcutaneously or intrasplenically with HCT116 or C26 tumor cells, respectively. CRC tumors resulted in significant muscle wasting regardless of tumor type or model, although muscle loss was exacerbated in mHCT116 hosts. The mHCT116 model decreased ribosomal (r)RNA content and rDNA transcription, whereas the mC26 model showed no loss of rRNA and the upregulation of rDNA transcription. The xHCT116 model reduced mTOR, RPS6, and 4E-BP1 phosphorylation, whereas the mHCT116 model had a similar effect on RPS6 and 4E-BP1 without altering mTOR phosphorylation. The C26 models caused a reduction in 4E-BP1 phosphorylation independent of mTOR. Muscle interleukin (IL)-6 mRNA was elevated in all models except xHCT116, and the NOD-, LRR-, and pyrin domain-containing protein 3 (NLRP3) mRNA was induced only in the mC26 model. IL-1β mRNA increased in all groups with greater expression in metastatic relative to the xenograft model regardless of tumor types. Our findings indicate that HCT116 tumor burden results in more drastic muscle wasting and anabolic deficits, whereas C26 tumor burden causes similar muscle wasting but exhibits a divergent proinflammatory phenotype. These results highlight potentially important divergence in the pathogenesis of muscle wasting among preclinical models of CRC and demonstrate that tumor burden plays a role in determining anabolic deficits and the expression of proinflammatory effectors of muscle wasting in a tumor-type-dependent manner.NEW & NOTEWORTHY We provide evidence demonstrating that colorectal tumor burden plays a role in determining anabolic deficits and the expression of proinflammatory effectors of muscle wasting in a tumor-type-dependent manner.