Preclinical Models for Studying the Impact of Macrophages on Cancer Cachexia

Abstract

Cancer‐associated cachexia is defined by loss of weight and muscle mass, and by the potential loss of adipose tissue accompanied by insulin resistance and increased resting energy expenditure. Cachexia is most prevalent in pancreatic cancer, the third leading cause of cancer‐related deaths. While various factors interact to induce cachexia, the precise mechanisms underlying this clinical condition are not fully understood. Clinically relevant animal models of cachexia are needed given the lack of standard diagnostic methods or treatments for this condition. Described in this article are in vitro and in vivo models used to study the role of macrophages in the induction of cachexia in pancreatic cancer. Included are procedures for isolating and culturing bone marrow−derived macrophages, harvesting tumor‐ and macrophage‐derived conditioned medium, and studying the effect of conditioned medium on C2C12 myotubes. Also described are procedures involving the use of an orthotopic model of pancreatic cancer, including a method for examining skeletal muscle atrophy in this model. © 2020 Wiley Periodicals LLC. Basic Protocol 1: In vitro model of pancreatic tumor‐induced cachexia using C2C12 cell lines (myotube model) Support Protocol 1: Molecular evaluation of cachectic markers in C2C12 myotubes using real‐time PCR and immunoblotting Basic Protocol 2: In vivo model to study cachectic phenotype in pancreatic tumor‐bearing mice Support Protocol 2: Evaluation of cachectic markers in the skeletal muscle of tumor‐bearing mice

HDAC4 Knockdown Alleviates Denervation-Induced Muscle Atrophy by Inhibiting Myogenin-Dependent Atrogene Activation

“…Nixon et al suggested that SIK1 promotes insulin resistance on a high fat diet in skeletal muscle (Nixon et al, 2016 ). Insulin resistance plays an important role in many processes of muscular atrophy (Brener et al, 2020 ; Markov et al, 2020 ; Pár et al, 2021 ). Our study found that SIK1 expression was upregulated during denervation-induced muscle atrophy.…”

In Vitro Models for Cancer-Associated Cachexia: The Complex Modelling of a Multiorgan Syndrome

“…During differentiation, upon serum withdrawal from the culture medium and low concentration of horse serum cells can fuse forming multinucleated structures turning into elongated fibre-shaped myotubes [40]. As such, the cell line can be induced to undergo stepwise differentiation since a muscle precursor (satellite cells) to a myoblast, followed by a myocyte, and ultimately a multinucleated myotube [41]. These features enable the characterisation of the mechanisms that regulate each step of muscle development and functioning [41,42].…”

“…As such, the cell line can be induced to undergo stepwise differentiation since a muscle precursor (satellite cells) to a myoblast, followed by a myocyte, and ultimately a multinucleated myotube [41]. These features enable the characterisation of the mechanisms that regulate each step of muscle development and functioning [41,42].…”

Review of the endocrine organ–like tumor hypothesis of cancer cachexia in pancreatic ductal adenocarcinoma

“…The orthotopic animal model is histologically similar to PDAC patients, mimicking the TME associated with intact tumors, suggesting that the TME may be involved in cachexia induction. Studies in PDAC animal models have demonstrated that tumor-associated macrophages mediate muscle wasting via the activation of signal transducer and activator of transcription (STAT)3 signaling ( 134 , 141 ).…”