THU507 Tumor Activin A Mediates Cachexia Primarily Through White Adipose Tissue Hydrolysis In Pancreatic Ductal Adenocarcinoma

Abstract

Abstract Disclosure: S. Yu: None. Y. Luan: None. R. Dong: None. A. Abazarikia: None. S. Kim: None. Pancreatic ductal adenocarcinoma (PDAC) commonly harbors mutations in KRAS and TP53 genes and its overall 5-year survival rate is only 10% in the US. Among risk factors associated with the dismal PDAC prognosis, cachexia accounts for about 30% of PDAC-related death and is present in nearly 80% of PDAC patients. Significant adipose tissue loss followed by skeletal muscle loss characterizes PDAC-related cachexia in humans and mice. Accumulated evidence indicates that activin A, a homodimer of inhibin βA that is encoded by the INHBA gene, is a recognized key cachexia mediator as supported by mitigation of weight loss by activin A antagonists in PDAC-bearing mice. However, much remains unclear regarding the primary source cells of activin A and the mechanisms by which activin A mediates cachexia in PDAC. To address the unknowns, we employed CRISPR/Cas9 system for Inhba gene knock-down (KD) in mouse KPC (KrasG12D and Trp53R172H) PDAC cells and generated orthotopic mice using Inhba KD or control KPC cells. Sham group which received the same operation except for cell injection was included. Body weight was measured on a daily basis, and blood and white adipose tissues (WATs) and skeletal muscle tissues were harvested on post-surgery day 12. We found that, when compared to the Sham group, injection of control KPC cells significantly elevated serum activin A levels up to 6 ng/mL and temporally decreased the average body weight in the orthotopic mice (Ctrl group), whereas Inhba gene KD significantly reduced serum activin A levels by ∼ 2 ng/mL and prevented weight loss in the orthotopic mice (KD group). When compared to the Sham and KD groups, notable reductions in organ weights of epididymal, mesenteric or subcutaneous WATs were found in the Ctrl group, however, weights for gastrocnemius and plantaris or soleus muscle tissues were statistically similar between the Ctrl and KD groups at post-surgery day 12. Correspondingly, the average serum free fatty acids levels were higher in the Ctrl group than the KD group. Histological observations support that dramatic adipocyte size reductions in WATs were prevented by serum activin A suppression. Immunofluorescence analysis showed that WATs from the Ctrl group had considerably higher protein expression of hormone-sensitive or adipose triglyceride lipase than the KD and Sham groups. Furthermore, phosphorylation of SMAD3 and phosphorylated PKA substrate which regulate adipocyte lipolysis were intensely stained in WATs from the Ctrl group when compared to the KD and Sham groups. Collectively, our findings identify PDAC cancer cells as the major source of activin A in PDAC and suggest systemic activin A as a potential mediator of PDAC-related adipose tissue loss. The current findings warrant further investigation to address clinical relevance. Presentation: Thursday, June 15, 2023