As research and understanding of the cardiotoxic side-effects of anticancer therapy expands further and the affected patient population grows, notably the long-term survivors of childhood cancers, it is important to consider the full range of myocardial cell types affected. While the direct impacts of these toxins on cardiac myocytes constitute the most immediate damage, over the longer term, the myocardial ability to repair, or adapt to this damage becomes an ever greater component of the disease phenotype. One aspect is the potential for endogenous myocardial repair and renewal and how this may be limited by cardiotoxins depleting the cells that contribute to these processes. Clear evidence exists of new cardiomyocyte formation in adult human myocardium, along with the identification in the myocardium of endogenous stem/progenitor cell populations with pro-regenerative properties. Any effects of cardiotoxins on either of these processes will worsen long-term prognosis. While the role of cardiac stem/progenitor cells in cardiomyocyte renewal appears at best limited (although with stronger evidence of this process in response to diffuse cardiomyocyte loss), there are strong indications of a pro-regenerative function through the support of injured cell survival. A number of recent studies have identified detrimental impacts of anticancer therapies on cardiac stem/progenitor cells, with negative effects seen from both long-established chemotherapy agents such as, doxorubicin and from newer, less overtly cardiotoxic agents such as tyrosine kinase inhibitors. Damaging impacts are seen both directly, on cell numbers and viability, but also on these cells' ability to maintain the myocardium through generation of pro-survival secretome and differentiated cells. We here present a review of the identified impacts of cardiotoxins on cardiac stem and progenitor cells, considered in the context of the likely role played by these cells in the maintenance of myocardial tissue homeostasis.

/pdf/effects-of-cardiotoxins-on-cardiac-stem-and-progenitor-cell-35n1o0jn6i.pdf

Effects of Cardiotoxins on Cardiac Stem and Progenitor Cell Populations.

\n Aim:\n Sorafenib (Nexavar) is a multitargeted tyrosine kinase inhibitor that is used for treatment of hepatocellular carcinoma and renal cell carcinoma. Cancer treatment with sorafenib has been reported to be associated with cardiotoxic side effects such as hypertension, myocardial ischemia, thrombosis and pulmonary embolism, whereas incidence of LV dysfunction is rare. Aim of the current study was to identify the mechanism of sorafenib cardiotoxicity.\n \n \n Results:\n Healthy mice were treated with sorafenib (50 mg/kg/d) for 4 weeks. Echocardiography analysis revealed no difference in LV systolic function, but LV posterior wall thickness and relative wall thickness were significantly increased, and LV volume decreased in sorafenib treated mice. Hearts of sorafenib treated mice showed a 10-fold increase in expression of heart failure marker gene ANP and a 3-fold increase in the number of apoptotic cells. Electron microscopy analysis indicated damage to cardiac endothelial cells with no evidence of cardiomyocyte loss and co-staining of cardiac sections with endothelial marker CD31 revealed that ~80% of apoptotic cells in sorafenib treated hearts were endothelial cells (ECs). To assess for the time course for EC damage, we treated mice with sorafenib for 8h, 24h, 48h and 72h. The increase in EC death was already detected after 8h treatment and peaking at 24h-48h. RNA profiling analysis showed that expression of angiopoietin-1 (Angpt1) was reduced, whereas expression of Angpt2 was induced in hearts of mice treated with sorafenib for 4 weeks and in EC fractions from hearts of mice treated with sorafenib for 72h. Angpt-1 overexpression induced protective signaling pathways in hearts of mice treated with sorafenib for 48h, but did not rescue from acute EC injury. Treatment of Angpt1 overexpressing mice with sorafenib for 4 weeks resulted in capillary rarefaction and heart failure, evidenced by a decrease in LV systolic function and a 40-fold increase in ANP expression.\n \n \n Conclusion:\n our data shows that sorafenib cardiotoxicity is due to endothelial cell damage in the heart and results in heart failure with preserved ejection fraction. Furthermore, antagonizing the function of Angpt2 by overexpression of Angpt1 is detrimental during sorafenib treatment.\n

Olli Tehunen

Papers

Abstract 731: Sorafenib Induces Cardiotoxicity via Damage to Cardiac Endothelial Cells