HMGB1 and neoplasm: Administration of LLC‐ or C26‐CM to C2C12 myotubes recapitulated the muscle protein catabolism seen in tumour‐bearing mice through UPS activation via p38 MAPK.35 C2C12 myotubes treated with LLC‐ or C26‐CM showed rapid up‐regulation of Ager (Figure6A) and S100b with unaffected levels of Hmgb1 (FigureS9A).