Proteomic profiling of skeletal and cardiac muscle in cancer cachexia: alterations in sarcomeric and mitochondrial protein expression

// Angie M. Y. Shum 1, 2, * , Anne Poljak 3, 4, 5, * , Nicholas L. Bentley 1, 3 , Nigel Turner 3 , Timothy C. Tan 1, 2, 6 and Patsie Polly 1, 2 1 Mechanisms of Disease and Translational Research, School of Medical Sciences, Faculty of Medicine, UNSW Sydney, New South Wales, Australia 2 Department of Pathology, School of Medical Sciences, Faculty of Medicine, UNSW Sydney, New South Wales, Australia 3 Department of Pharmacology, School of Medical Sciences, Faculty of Medicine, UNSW Sydney, New South Wales, Australia 4 Bioanalytical Mass Spectrometry Facility, UNSW Sydney, New South Wales, Australia 5 Centre for Healthy Brain Ageing, School of Psychiatry, UNSW Sydney, New South Wales, Australia 6 Western Clinical School and Westmead Hospital, Westmead, New South Wales, Australia * These authors contributed equally to this work Correspondence to: Patsie Polly, email: patsie.polly@unsw.edu.au Keywords: cancer cachexia; muscle; skeletal; cardiac; proteomics Received: December 22, 2016      Accepted: March 10, 2018      Published: April 24, 2018 ABSTRACT Background: Cancer cachexia is observed in more than 50% of advanced cancer patients, and impairs quality of life and prognosis. A variety of pathways are likely to be dysregulated. Hence, a broad-spectrum understanding of the disease process is best achieved by a discovery based approach such as proteomics. Results: More than 300 proteins were identified with > 95% confidence in correct sequence identification, of which 5–10% were significantly differentially expressed in cachectic tissues ( p -value of 0.05; 27 proteins from gastrocnemius, 34 proteins from soleus and 24 proteins from heart). The two most pronounced functional groups being sarcomeric proteins (mostly upregulated across all three muscle types) and energy/metabolism proteins (mostly downregulated across all muscle types). Electron microscopy revealed disintegration of the sarcomere and morphological aberrations of mitochondria in the cardiac muscle of colon 26 (C26) carcinoma mice. Materials and Methods: The colon 26 (C26) carcinoma mouse model of cachexia was used to analyse soleus, gastrocnemius and cardiac muscles using two 8-plex iTRAQ proteomic experiments and tandem mass spectrometry (LCMSMS). Differentially expressed proteomic lists for protein clustering and enrichment of biological processes, molecular pathways, and disease related pathways were analysed using bioinformatics. Cardiac muscle ultrastructure was explored by electron microscopy. Conclusions: Morphological and proteomic analyses suggested molecular events associated with disintegrated sarcomeric structure with increased dissolution of Z-disc and M-line proteins. Altered mitochondrial morphology, in combination with the reduced expression of proteins regulating substrate and energy metabolism, suggest that muscle cells are likely to be undergoing a state of energy crisis which ultimately results in cancer-induced cachexia.