Abstract 15790: Combination of Doxorubicin and Trastuzumab Induces Rapid Downregulation of Epidermal Growth Factor Receptor 2 Independent of Oxidative Stress and Apoptosis
Introduction: Combination of Doxorubicin (Dox) and monoclonal antibody trastuzumab (Trz) is effective against breast cancer but highly cardiotoxic. The mechanisms of Dox/Trz-induced cardiotoxicity are unclear. Dox has been shown to deplete the c-kit+ cardiac progenitor cells pool in rats. Trz has been associated with reduced regenerative potential of cardiospheres. Our study addresses the effect of Dox/Trz combination on human CPCs (hCPCs).
Methods: Human epidermal growth factor receptor 2 (HER2) and 4 (HER4) expression was assessed in human adult heart sections by IF. c-kit+ hCPCs were treated with Dox (1μM), Trz (20 μg/ml) or Dox/Trz for 4, 8 or 16h. Control hCPCs (CTR) were untreated. HER2 and HER4 levels were measured by WB, IF and FACS in CTR versus treated cells. ROS and apoptosis were evaluated by FACS measuring CellRox+ or AnV+/Dapi+ cells, respectively. Proliferation was measured at 48h by Cyquant assay.
Results: In heart sections HER2 was identified only in subepicardial and intramyocardial cells, whereas HER4 was also expressed in cardiomyocytes. In vivo, a subset of HER2+ cells co-expressed c-kit. In vitro, HER2 and HER4 were present in ~22% and ~76% of hCPCs, respectively. Trz gradually downregulated HER2, while Dox did not have any effect. Dox/Trz accelerated HER2 decrease, being completed at 8h with no concomitant increase of ROS and apoptosis. Dox/Trz synergic effect was also evident on Akt inactivation. HER4 was not significantly affected under the same experimental conditions. Trz reduced cell proliferation of ~ 20% versus CTR at 48h; at the same time point there was evidence of Dox and Dox/Trz-induced cell death.
Conclusion: Our results demonstrate that in hCPCs Dox/Trz combination specifically induces the rapid (8h) downregulation of HER2 independent of ROS production and apoptosis. Our findings suggest that disruption of HER2 signaling in hCPCs may play a key role in Dox/Trz-induced cardiotoxicity.
- © 2013 by American Heart Association, Inc.