Q. A 65-year-old man with a history of advanced pancreatic cancer presents to the clinic for a follow-up visit. Despite aggressive chemotherapy, his cancer has continued to progress. Over the past few months, the patient's family members have noted that he has lost a significant amount of weight, appears fatigued, and has diminished muscle strength. His appetite has also decreased substantially. On examination, the patient is found to be extremely thin, with visible loss of both muscle mass and subcutaneous fat. What is the predominant pathophysiological mechanism underlying this patient's muscle wasting?