Blockade of the erbB2 Receptor Induces Cardiomyocyte Death through Mitochondrial and Reactive Oxygen Species-dependent Pathways

Leo I Gordon,Michael A Burke,Amareshwar T.K Singh,Sheila Prachand,Elliot D Lieberman,Lin Sun,Tejaswitha Jairaj Naik,Sathyamangla V Naga Prasad,Hossein Ardehali

doi:10.1074/jbc.m804570200

Leo I Gordon, Michael A Burke + Show 7 more

Open Access

https://doi.org/10.1074/jbc.m804570200

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Abstract

Overexpression of the receptor tyrosine kinase erbB2 (Her2 in humans) is correlated with a poor prognosis in breast and ovarian cancers. Treatment with trastuzumab (a monoclonal antibody against erbB2) improves survival; however, it also causes cardiomyopathy. We hypothesized that blockade of the erbB2 receptor induces cardiomyocyte death through a mitochondrial pathway that is dependent on the production of reactive oxygen species (ROS). We first showed that levels of erbB2 receptor are significantly decreased in an animal model of ischemic heart disease and in human ischemic cardiomyopathy. We treated neonatal rat cardiomyocytes with an inhibitory erbB2 antibody to study the mechanism behind the deleterious effects of erbB2 blockade. These cells displayed a dose-dependent increase in ROS production and cell death compared with control IgG-treated cells; these processes were reversed by the antioxidant, N-acetylcysteine. The effects of erbB2 antibody on both cell death and ROS production were also reversed by cyclosporine A and diazoxide, chemicals that regulate the pro- and anti-apoptotic channels in the mitochondria, respectively. Furthermore, mouse embryonic fibroblasts lacking Bax and Bak (proteins that mediate cell death through a mitochondrial pathway) were resistant to the deleterious effects of erbB2 antibody. These effects of erbB2 blockade appear to occur through a pathway involving AKT and PKC-alpha. Our results suggest that erbB2 plays a role in cardiomyocyte survival, and that the deleterious effects of trastuzumab on the heart occur through a mitochondrial pathway and is mediated by ROS production. Manipulation of redox signaling may be beneficial in cancer patients receiving trastuzumab.

Highlights

The Her-2/neu oncogene, known as erbB2 in nonhuman organisms, is a transmembrane receptor tyrosine kinase that belongs to the epidermal growth factor receptor family [1, 2]
Our results suggest that erbB2 plays a role in cardiomyocyte survival, and that the deleterious effects of trastuzumab on the heart occur through a mitochondrial pathway and is mediated by reactive oxygen species (ROS) production
Effects of erbB2-Ab on Cardiomyocytes Occur through an The cell surface tyrosine kinase receptor erbB2 plays an AKT- and PKCa-dependent Pathway—We studied the important role in a variety of cellular functions; it can signaling mechanisms that lead to the deleterious effects of function as an oncogene in several malignancies, including erbB2-Ab on cardiomyocytes

Summary

The abbreviations used are

Antibody; ROS, reactive oxygen species; CM, cardiomyopathy; NAC, N-acetylcysteine; NRCM, neonatal rat cardiomyocytes; TMRE, tetramethylrhodamine ethyl ester; PBS, phosphate-buffered saline; DCF and H2DCFDA, 5-(and-6)-carboxy-2Ј,7Ј-dichlorodihydrofluorescein diacetate; LCx, left circumflex coronary artery; LAD, left anterior descending coronary artery; CsA, cyclosporine A; mPTP, mitochondrial permeability transition pore; mitoKATP, mitochondrial ATP-sensitive potassium channel; MEF, mouse embryonic fibroblasts; DKO, double knockout; WT, wild type; TUNEL, terminal deoxynucleotidyltransferase-mediated dUTP nick end-labeling. Our results suggest that erbB2 blockade increases ROS through a mitochondrial pathway

EXPERIMENTAL PROCEDURES

Findings

DISCUSSION