The TWEAK/Fn14 signaling promotes skeletal muscle wasting during cancer cachexia

Cachexia is an involuntary loss of body weight mostly due to skeletal muscle wasting. The proinflammatory cytokine TWEAK and its receptor Fn14 constitute a major signaling system that regulates skeletal muscle mass in diverse conditions. However, the role of TWEAK/Fn14 system in the regulation of skeletal muscle mass during cancer-induced cachexia remains poorly understood. In this study, we demonstrate that the levels of Fn14, but not TWEAK, are induced in skeletal muscle of multiple mouse models of cancer cachexia. Targeted deletion of Fn14 inhibits muscle wasting and gene expression of multiple components of the ER stress-induced unfolded protein response (UPR) in the KPC mouse model of pancreatic ductal adenocarcinoma (PDAC) cancer cachexia. The TWEAK/Fn14 signaling activates PERK and IRE1α arm of the UPR and inhibits protein synthesis in cultured primary myotubes. Inhibition of PERK using pharmacological or molecular approaches improves protein synthesis and inhibits atrophy in TWEAK-treated cultured myotubes. Silencing of Fn14 in KPC cells prior to their inoculation in pancreas of mice also attenuates tumor growth without having any significant effect on muscle atrophy. The knockdown of Fn14 inhibits proliferation, migration, and invasion of cultured KPC cells. Finally, our results demonstrate that targeted ablation of Fn14 also attenuates muscle atrophy in the Lewis lung carcinoma model of cancer cachexia. Altogether, our study provides initial evidence that the inhibition of TWEAK/Fn14 signaling can prevent tumor growth and skeletal muscle wasting during cancer-induced cachexia.