Abstract P147: Antiangiogenic Effect of Doxorubicin on Human Cardiac Microvascular Endothelial Cells Does Not Result from Reduced Vascular Endothelial Growth Factor Production

Abstract

Clinical use of the potent anticancer agent doxorubicin (DOX) is limited by a dose-dependent cardiomyopathy. Although cardiac muscle has been thought to be a primary target of the cardiotoxic effect of doxorubicin, our studies indicate that adult cardiomyocytes may be resistant to the direct effects of this agent. These studies have prompted us to identify alternative targets for doxorubicin in adult heart that may contribute to the development of cardiomyopathy. Additionally, recent literature report ( Lee et al. PNAS 2009;106:2353–2358 ) indicated that DOX inhibited tumor angiogenesis due to the reduced production of vascular endothelial growth factor (VEGF) by tumor cells. We set out therefore to test the hypothesis that DOX inhibits angiogenesis by human cardiac microvascular endothelial cells (HCMVEC) via inhibition of VEGF production. We detected reduced proliferation/viability of HCMVEC cultures treated with DOX. DOX increased caspase-3-like activity and development of apoptosis in HCMVEC, and inhibited the formation of vascular tubule formation in a co-culture of HCMVEC with human cardiac fibroblasts (HCF) with an IC 50 of 8 nM. HCF cultures released 7-fold greater amounts of VEGF into the culture media as compared with HCMVEC under the normoxic conditions while 1% hypoxia and 100 μM CoCl 2 further increased the production of VEGF by HCF. DOX moderately inhibited hypoxia- and CoCl 2 -induced VEGF release by these cells at concentrations above 500 nM whereas inhibition of vascular tubule formation by DOX in a co-culture system occurred at much lower concentrations and was not associated with the reduced production of VEGF. We conclude that DOX is a very potent antiangiogenic agent in the human cardiac microvascular endothelial cell system. However, this effect of DOX is not caused by the reduced production of VEGF. Inhibition of vascular network formation in the heart is likely to contribute to the development of doxorubicin cardiomyopathy in treated patients.