Abstract 1601: The role of complement in pancreatic cancer cachexia

Abstract Cancer cachexia is a multifactorial condition characterized by skeletal muscle atrophy and dysfunction that impairs longevity and quality of life for the vast majority of cancer patients. Recently, we discovered through unbiased proteomic analyses that the complement system is activated in the skeletal muscle of cachectic pancreatic cancer patients. Therefore, the purpose of this study was to investigate the role of complement in pancreatic cancer cachexia. To accomplish this, we obtained genetically modified, C57Bl6/J congenic mice lacking the central regulator of complement, C3 (C3−/− mice). Wild-type (C57Bl6/J, WT, n=12) and C3−/− mice (n=11) (male, 12 weeks old) received orthotopic injections of mouse pancreatic cancer cells (KPC) into the pancreas, and as non-cancer controls, WT (n=8) and C3−/− (n=4) mice received injections of PBS into the pancreas. Mice were monitored daily and euthanized at IACUC-mandated tumor endpoint (body condition score ≤ 2; range: 14-15 days). In-vivo diaphragm function was assessed immediately prior to euthanasia via M-mode ultrasound. Skeletal muscles (soleus, SOL; tibialis anterior, TA; diaphragm, DIA) were harvested and ex-vivo contractile function was assessed on strips of costal diaphragm. Diaphragmatic excursion and respiratory rate were reduced with KPC tumor burden in WT mice, but preserved in C3−/− mice. Deletion of C3 did not influence the KPC-induced reduction of body mass or KPC tumor growth. Atrophy of limb muscle mass (SOL, TA) and fiber size (TA) during KPC tumor burden was attenuated in C3−/− mice. Maximal specific force of DIA was greater in C3−/− versus WT KPC-bearing mice. KPC tumor burden increased collagen content in the DIA of WT mice, but not C3−/− mice. Diaphragm fiber size was reduced in WT KPC-bearing mice, but preserved in C3−/− mice. KPC tumor burden induced significant increases in immune cell (CD45+) infiltration and fibroadipogenic progenitor cell (PDGFRa+) abundance in the DIA of WT tumor-bearing mice, but to a lesser extent in C3−/− mice. These findings suggest complement activation is causative in pancreatic cancer-induced skeletal muscle wasting and dysfunction. Inhibition of complement during cancer cachexia may possess therapeutic potential for the preservation of skeletal muscle mass and function. Citation Format: Andrew C. D'Lugos, Chandler Callaway, Sarah M. Judge, Andrew R. Judge. The role of complement in pancreatic cancer cachexia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1601.