Cancer cachexia is a multifactorial condition characterized by skeletal muscle loss that impairs longevity and quality of life of the vast majority of cancer patients. However, the ability to develop therapeutic strategies to counter cachexia is impeded by the limited understanding of the underlying mechanisms of cachexia in human cancer patients. The purpose of this study was therefore to characterize the proteomic signature of skeletal muscle obtained from cachectic pancreatic ductal adenocarcinoma (PDAC) patients, who exhibit one of the highest rates of cachexia. Muscle biopsies (rectus abdominis) were obtained from PDAC patients (n=8; 70±10yr; BMI: 26.8±5.9kg･m-2) undergoing tumor resection surgery as well as age and sex-matched non-cancer controls (n=6; 66±9yr; BMI: 30.8±5.2kg･m-2). PDAC patients were cachectic (6 month body weight loss > 5%; mean: 15.7±7.9%) and did not undergo neoadjuvant therapy.