Lung Cancer-derived Exosomes Induced Myotube Atrophy Via The Extracellular IL-6-Mediated STAT3 Pathway

Background: Cancer cachexia(CAC)is a wasting syndrome characterized by body weight loss due to extensive skeletal muscle and adipose tissue wasting and systemic inflammation.The most important feature of patients with cachexia is skeletal muscle loss.Multiple metabolic alterations are accountable for the loss of muscle mass observed in patients with cachexia,ultimately reducing the quality of life of patients.Cytokines and hormones secreted by tumor cells can promote the cachexia of cancer patients.Tumor cells derived cytokines,hormones and circulating factors may cause cachexia.Exosomes(exos)can participate in inflammatory immune response,intercellular signal communication,cell survival and apoptosis,autophagy,etc.,and play an important role in the progression of the disease.In this study,we investigated whether exosome secreted by Lewis lung cells(LLC derived exosome,LLC-exo)contains interleukin-6(IL-6)and explores the role of exosomes in myotube atrophy.Purpose: 1.To explore whether exosome secreted by Lewis lung cells(LLC derived exosome,LLC-exo)contains interleukin-6(IL-6)and explores the role of exosomes in myotube atrophy.2.Explore the mechanism of muscle atrophy in cachexia mice.Methods: 1.Using the method of ultracentrifugation to isolate exosomes from LLC cells and serum from patients with lung cancer,non-lung cancer controls,tumor-bearing mice,and non-tumor-bearing control mice;2.Using electron microscopy,particle size analysis and western blot method to identify exosomes;3.Using Western Blot to detect the expression of muscle atrophy-associated protein;4.Using immunofluorescence to detect the uptake of LLC-exosomes by C2C12;5.HE staining was used to detect the muscle fibers size of mice.Results: 1.The expression of muscle atrophy-related proteins were increased in LLCinduced cachexia mice;2.LLC derived exosomes can be taken up by C2C12 myotubes and can promote C2C12 myotube atrophy;3.LLC-derived exosomes containing IL-6,which can promote myotube atrophy by activating Signal transducing activator of transcription(STAT3)signaling pathway;4.Neutralization of extracellular IL-6 or Stat3 inhibitor S3I-201 Both can alleviate the atrophy induced by LLC exosomes.Conclusions: Our data showed that LLC cell-derived exosomes containing IL-6,which can promote myotube atrophy by activating STAT3 signaling pathway.