Abstract P5-18-08: Identification of ErbB2 function in the heart: implication for anti-ErbB2 therapy in breast cancer

Abstract

Abstract The ErbB2 receptor tyrosine kinase is essential for cardiac development during embryogenesis. The importance of its signaling in the adult heart was revealed by an unexpected cardiotoxic side effect of trastuzumab, a monoclonal antibody against ErbB2 used in the treatment of breast cancer. Considering that trastuzumab-associated cardiotoxicity is usually largely reversible, we hypothesized that ErbB2 signaling in the heart is important to maintain cardiac homeostasis. As genetic experiments showed that ErbB2-deficient embryos die at mid-gestation, whereas conditional inactivation of ErbB2 in the heart leads to early and severe cardiac dysfunction, the role of ErbB2 in the mature heart can not be analyzed in those animal models. Thus, we chose an ErbB2 hypomorph (HP) mouse model in which ErbB2 is expressed at only 10% of its endogenous level to study the role of ErbB2 in the adult heart. Histopathological analyses of the heart in this model revealed that at birth, the ErbB2 HP mice have similar heart mass and cardiomyocite size as the control animals. However, we found that the rapid growth of the heart during early postnatal development is impaired in ErbB2 HP mice, indicating that the heart is unable to increase cell size in order to adapt to the pressure overload that mice face following birth. This incapacity of the ErbB2 HP heart to maintain homeostasis eventually leads to the development of cardiac dysfunction in this model, as characterized by a decrease of the left ventricular function. Microarray and ChIP-seq analyses were applied to identify the ErbB2-responsive pathways which may explain the phenotype observed. Taken together, our results demonstrate that ErbB2 signaling is required for the physiological adaptive response of the mature heart to pressure burden. The results generated by this study reveal the biological function of Erbb2 in the adult heart, but also provide important information for devising strategies to prevent and mitigate the cardiotoxic effects of Trastuzumab treatment, allowing for the potential use of this drug to treat all cancer patients overexpressing ErbB2. Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P5-18-08.