Formation of Liver Metastases Is Accompanied by Accelerated Musculoskeletal Deficits in LLC Tumor Hosts

Lung cancer is a leading cause of death worldwide and is often accompanied by declines in musculoskeletal health (i.e., cachexia). Despite affecting a majority of lung cancer patients, cachexia remains understudied and currently has no cure. We have previously demonstrated that liver metastases (LMs) exacerbate cachexia in murine models of colorectal cancer, and, while the liver represents a common site of metastases and is associated with poor prognosis in patients with lung cancer, whether LMs heighten musculoskeletal wasting in mice bearing lung cancer is unknown. Here, we aimed to characterize the impact of LMs on musculoskeletal health in a mouse model of lung cancer cachexia. C57BL/6J male mice were injected with LLC tumor cells either subcutaneously or intrasplenically (LMs) to mimic hepatic metastases (n = 6-9/group). Upon sacrifice, skeletal muscle, bone, and plasma were collected for morphological and molecular analyses. Consistently, compared to healthy controls, metastatic tumor hosts displayed greater reductions in muscle weights (~17%), in line with decreased muscle torque (~23%) and reduced muscle cross-sectional area (~10%). On a molecular level, skeletal muscle from mice bearing LMs had elevated levels of pStat3, Murf1, and Atrogin-1, suggesting enhanced protein catabolism. Similar to skeletal muscle, metastatic tumor hosts displayed greater losses in trabecular bone and increased skeletal fragility. Plasma proteomics identified 211 and 131 differentially expressed proteins in metastatic hosts compared to control animals and subcutaneous LLC hosts, respectively. Top regulated pathways in mice bearing LMs included neutrophil degranulation, BAG2 signaling, and cachexia signaling. Overall, our findings demonstrate that LMs are accompanied by accelerated musculoskeletal wasting and weakness in a mouse model of lung cancer cachexia. This work highlights the need for animal models that mimic advanced cancer, thus providing a better understanding of the mechanisms that mediate cachexia.