Tumor Progression Reverses Cardiac Hypertrophy and Fibrosis in a Tetracycline-Regulated ATF3 Transgenic Mouse Model

Cardiovascular diseases (CVD) and cancer are the top deadly diseases in the world. Both CVD and cancer have common risk factors; therefore, with the advances in treatment and life span, both diseases may occur simultaneously in patients. It is becoming evident that CVD and cancer are highly connected, establishing a novel discipline known as cardio-oncology. This includes the cardiomyocyte death following any anti-tumor therapy known as cardiotoxicity as well the intricate interplay between heart failure and cancer. Recent studies, using various mouse models, showed that heart failure promotes tumor growth and metastasis spread. Indeed, patients with heart failure were found to be at higher risk of developing malignant diseases. While the effect of heart failure on cancer is well established, little is known regarding the effect of tumors on heart failure. A recent study from our lab has demonstrated that tumor growth and metastasis ameliorate cardiac remodeling in a pressure-overload mouse model. Nevertheless, this study was inconclusive regarding whether tumor growth solely suppresses cardiac remodeling or is able to reverse existing heart failure outcomes as well. Here, we used a regulable transgenic mouse model for cardiac hypertrophy and fibrosis. Cancer cell implantation suppressed cardiac dysfunction and fibrosis as shown using echocardiography, qRT-PCR and fibrosis staining. In addition, tumor growth resulted in an M1 to M2 macrophage switch, which is correlated with cardiac repair. Macrophage depletion using clodronate liposomes completely abrogated the tumors' beneficial effect. This study highly suggests that harnessing tumor paradigms may lead to the development of novel therapeutic strategies for CVDs and fibrosis.