Abstract 11262: Effect of Active Cancer/Cachexia on the Development of Cardiac Dysfunction in Mice

Abstract

Introduction: Cancer is independently associated with the alteration of cardiac function prior to cardiotoxic chemotherapy (CCT) exposure. Similar to cancer associated cachexia (CAC), the elevation and the deleterious role of IL-6 in plasma was associated with a reduced cardiac function in heart failure (HF) patients subpopulation. Cancer cells manipulate BCL-2-associated athanogene 3 (BAG3)-HSP70-regulated pathways in tumor cells, which is a key regulator of protein turnover and contractility in cardiomyocyte. Hypothesis: Here, we aimed to characterize the progression of cardiac dysfunction and the expression of BAG3 and HSP70 in tumor-bearing mice. Methods: Colon-26 adenocarcinoma cells (C26; n=22) with/without shIL-6 (C26 shIL-6; n=22) were injected subcutaneously adult male BALB/c mice. Control mice were injected with PBS (n=13). Echocardiographic examinations and invasive hemodynamic measurements ( in vivo and ex vivo using isolated working hearts system) were performed at 10 (early) and 20 (late) days post injection, respectively. The expression of BAG3 and Hsp70 were determined by Western blot. Results: The tumor size was comparable between the cancer groups. However, only C26 group showed a significant loss of subcutaneous fat and skeletal muscle (p<0.05, respectively), confirming cachectic condition. Echocardiography results show a tendency to decline of ejection fraction at the early phase (p~0.08 vs Control), and turned significance lower at late stage (p<0.05 vs Control) in tumor-bearing mice. In line with that, invasive hemodynamic and isolated working heart measurements confirmed LV systolic and diastolic dysfunction (late stage, p<0.05 vs Control, respectively). Interestingly, heart rate and aortic flow were predominantly declined in cachectic animals (p<0.05 vs Control). Importantly, cardiac dysfunction was associated with a significant reduction in both BAG3 and Hsp70 in the myocardium independently of cachexia. Conclusions: Cancer rather than CAC is a main driver for the development of cardiac contractile dysfunction prior to CCT exposure. In addition, our data suggest that targeting BAG3-Hsp70 complex in the cardiomyocytes may provide a novel strategy to improve the cancer associated cardiac dysfunction.