Activin A Plays a Critical Role in Adipose Tissue Wasting in the Progression of Cancer Cachexia

Background: Nearly 50% of cancer patients suffer from cancer cachexia, a wasting syndrome with atrophy of white adipose tissue (WAT) and skeletal muscle. Cachexia leads to negative energy balance, limits cancer therapies, and reduces survival rate. It is characterized by body weight loss due to negative nutrients and energy balance from involuntary reduced food intake and abnormal metabolic conditions such as insulin resistance and hypertriglyceridemia. Cancer-driven factors such as activin A and IL-6 (interlukein-6) contribute to the occurrence of cachexia symptoms during cancer progression. While the importance of muscle atrophy has been emphasized in cachexia research, the underlying mechanism of adipose tissue wasting remains unclear. One proposed theory is that WAT switches to brown adipose tissue (BAT), characterized by the high expression level of UCP1 (uncoupling protein 1). Hypothesis: We hypothesize that activin A plays a critical role in adipose tissue wasting during cancer cachexia progression. Experiment: GDF9-iCre+; PIK3CA* female mice which shows cachexia symptoms in cancer progression were sacrificed before and after cachexia development. In addition, we injected FST288, an antagonist to activin A, for two weeks during cancer cachexia development. We harvested and analyzed multi-sites adipose tissues (gonadal, subcutaneous, interscapular and perirenal), muscle and liver. Serum activin A and IL-6 were measured using ELISA kits. DEXA and calorimetry analyses were performed, as well as immunohistochemistry, qPCR and western blotting assay. Results:GDF9-iCre+; PIK3CA* female mice started to display bilateral ovarian tumors around postnatal day (PD) 60, lose body weight around PD70 and became cachexia condition around PD80 with an increased level of serum activin A. Along with that, other body organs including liver, pancreas, muscle, and adipose tissues became dramatically small in mass. Our data proved that cachexia progression is correlated with the level of activin A rather than IL-6 in serum of GDF9-iCre+; PIK3CA* female mice. As serum activin A increased, adipocytes lost lipids and had distinct browning phenotypes in some adipocytes within WAT. Interestingly, calorimetry analysis did not display an increase in energy expenditure in cachectic mice although browning was evident in WAT. However, treatment with FST288 during cancer progression kept body weight and WAT in GDF9-iCre+; PIK3CA* female mice. Most of all, FST288 protected the size and lipid droplets of adipose tissues against WAT wasting during cachexia development. Conclusion: The progression of cancer cachexia impacts adipose tissues. Injection of FST288 supports the key role of activin A in the progress of cachexia. FST288 prevented adipose tissue wasting and cachexia development, revealing another evidence of the efficacy of activin A antagonist in preventing cancer cachexia development.