Trastuzumab, but Not Pertuzumab, Dysregulates HER2 Signaling to Mediate Inhibition of Autophagy and Increase in Reactive Oxygen Species Production in Human Cardiomyocytes

Abstract

Dysregulation of autophagy has been implicated in various cardiovascular diseases. Trastuzumab, a humanized monoclonal antibody, binds to HER2 domain IV and is approved for the treatment of HER2-positive breast cancer. Trastuzumab therapy is associated with considerable cardiotoxicity, the mechanism of which remains unclear. HER2 signaling plays a pivotal role in cardiomyocyte development and survival and is essential for the prevention of cardiomyopathy. However, a direct link has not been confirmed between trastuzumab-induced cardiomyopathy and impaired HER2 signaling. Our data reveal a novel mechanism by which trastuzumab dysregulates HER2 signaling and impairs basal autophagic process in human primary cardiomyocytes. Specifically, trastuzumab treatment leads to the phosphorylation of HER1-Y845 and HER2-Y1248 and the activation of Erk. This in turn results in upregulation of mTOR signaling pathway and subsequently inhibition of autophagy in primary cardiomyocytes and C57BL/6 mice. Trastuzumab-induced downregulation of autophagy is further supported by the fact that trastuzumab treatment reduces protein levels of autophagosome-associated signaling molecules such as Atg 5-12, Atg 7, Atg 14, and Beclin 1. We further demonstrated that trastuzumab-mediated inhibition of autophagy resulted in the increased production of reactive oxygen species (ROS) in cardiomyocytes. Pertuzumab, another anti-HER2 therapeutic mAb binding to HER2 domain II, fails to modulate HER2 signaling and is unable to inhibit autophagy and to increase ROS production in cardiomyocytes. This study provides novel mechanistic insights into trastuzumab-induced cardiotoxicity, which may assist in formulating novel approaches for clinical management of trastuzumab-induced cardiomyopathy.

Cellular and molecular mechanisms underlying alcohol-induced aggressiveness of breast cancer

“…There is considerable interaction between oxidative stress and EGFR/ErbB2. ROS may either activate EGFR/ErbB2 or directly target their down-stream signaling components [108–110]. This is supported by the evidence showing that alcohol stimulates the phosphorylation of EGFR and ErbB2 in mammary epithelial cells and breast cancer cells in a ROS-dependent manner [38, 66].…”

Trastuzumab-mediated cardiotoxicity: current understanding, challenges, and frontiers

“…Recent investigation from our lab confirmed the direct link between impaired HER2 signaling and trastuzumab-induced cardiotoxicity and showed that trastuzumab dysregulates HER2 signaling and suppresses autophagy in cardiomyocytes to trigger accumulation of toxic reactive oxygen species (ROS) in human cardiomyocytes [25]. Trastuzumab disrupts HER signaling by inducing phosphorylation of HER1 and HER2 at 845 and 1248 sites, respectively, and activates autophagy-inhibitory Erk/mTOR/Ulk 1 signaling cascade, thereby compromising cardiomyocyte’s ability to recycle toxic cellular substrates causing cardiotoxicity [25]. On the contrary, pertuzumab, another anti-HER2 monoclonal antibody with distinct epitope, did not affect HER2 signaling cascade (as evaluated by HER1 and HER2 phosphorylation), at least in cardiomyocyte in vitro model, which is consistent with results from clinical studies reporting that addition of pertuzumab to trastuzumab-based regimens did not have additive or synergistic effect on cardiotoxicity [26].…”

“…Conditional mutant mice carrying cardiac-specific deletion of HER2 showed multiple independent parameters of dilated cardiomyopathy, thus emphasizing the pivotal role of HER2 in embryonic and postnatal cardiogenesis [24]. Recent investigation from our lab confirmed the direct link between impaired HER2 signaling and trastuzumab-induced cardiotoxicity and showed that trastuzumab dysregulates HER2 signaling and suppresses autophagy in cardiomyocytes to trigger accumulation of toxic reactive oxygen species (ROS) in human cardiomyocytes [25]. Trastuzumab disrupts HER signaling by inducing phosphorylation of HER1 and HER2 at 845 and 1248 sites, respectively, and activates autophagy-inhibitory Erk/mTOR/Ulk 1 signaling cascade, thereby compromising cardiomyocyte’s ability to recycle toxic cellular substrates causing cardiotoxicity [25].…”

Pharmacogenetics of Chemotherapy-Induced Cardiotoxicity

“…The Her2 pathway is known to be involved in normal development of cardiomyocytes and conditional mutations of the HER2 receptor in cardiomyocytes lead to dilated cardiomyopathy [20]. Furthermore, trastuzumab has been shown to downregulate autophagy in primary cardiomyocytes leading to increased reactive oxygen species [21]. …”