MS-1805

A 70-year-old man with advanced metastatic prostate cancer is being visited at home by his GP due to his weakened state and cachexia. He is now bedridden and has ceased eating solid foods. The GP informs him that his body is breaking down protein at a faster rate than it can synthesize due to the increased metabolic demands of his tumors and reduced food intake.

Which molecule plays a crucial role in the biological process described above?