Complement pathway activation mediates pancreatic cancer–induced muscle wasting and pathological remodeling

Cancer cachexia is a multifactorial condition characterized by skeletal muscle wasting that impairs quality of life and longevity for many cancer patients. A greater understanding of the molecular etiology of this condition is needed for effective therapies to be developed. We performed a quantitative proteomic analysis of skeletal muscle from cachectic pancreatic ductal adenocarcinoma (PDAC) patients and non-cancer controls, followed by immunohistochemical analyses of muscle cross sections. These data provide evidence of a local inflammatory response in muscles of cachectic PDAC patients, including an accumulation of plasma proteins and recruitment of immune cells into muscle that may promote the pathological remodeling of muscle. Our data further support the complement system as a potential mediator of these processes, which we tested by injecting murine pancreatic cancer cells into wild-type mice and mice with genetic deletion of the central complement component 3 (C3–/– mice). Compared with wild-type mice, C3–/– mice showed attenuated tumor-induced muscle wasting and dysfunction and reduced immune cell recruitment and fibrotic remodeling of muscle. These studies demonstrate that complement activation contributes to the skeletal muscle pathology and dysfunction in PDAC, suggesting that the complement system may possess therapeutic potential in preserving skeletal muscle mass and function.