Abstract 935: Lapatinib and other tyrosine kinase inhibitors greatly potentiate doxorubicin-induced damage to cardiac myocytes

Abstract

Abstract Lapatinib (Tykerb) is dual tyrosine kinase inhibitor targeting the HER2 (ERBB2) and EGFR (ERBB1, HER1) pathways. Lapatinib has been shown in a clinical trial to produce low levels of cardiotoxicity that is reversible. Using a neonatal rat cardiac myocyte model we have investigated the ability of lapatinib alone, and in combination with doxorubicin, to damage myocytes. Lapatinib alone at pharmacological concentrations only slightly induced myocyte damage. However, doxorubicin-induced myocyte damage was greatly potentiated by the addition of low nanomolar lapatinib concentrations. Because trastuzumab also targets ERBB2 receptors, the lapatinib/doxorubicin combination also provides a good model to probe the mechanism of the increased cardiotoxicity caused by the concurrent use of trastuzumab and doxorubicin. Lapatinib treatment alone had little or no effect on myocyte mitochondrial membrane potential, on oxidation of intracellular DCF (dichlorofluorescein), on intracellular ATP levels, or on caspase 3/7 induction. While the doxorubicin cardioprotective agent dexrazoxane was able to greatly reduce doxorubicin-induced myocyte damage, it could only partially reduce the increase in myocyte damage produced by the lapatinib/doxorubicin treatment. Lapatinib alone had little effect on the phosphorylation status of ACC (acetyl-coenzyme A carboxylase) and AKT. Lapatinib alone decreased phosphorylated ERK (MAPK), which may have, in part, contributed to the increased doxorubicin-mediated myocyte damage. As measured by flow cytometry lapatinib-treated myocytes demonstrated an increased accumulation of doxorubicin. As lapatinib is a strong inhibitor of several ATP-dependent ABC-type efflux transporters, this likely occurred because lapatinib blocked doxorubicin efflux, thereby increasing intracellular doxorubicin concentrations. These results suggest that the clinical use of concurrent doxorubicin and lapatinib should be approached with care due to the possibility of lapatinib increasing doxorubicin cardiotoxicity. Several other kinase inhibitors (imatinib, dasatinib, sorafenib, sunitinib, gefitinib, pazopanib, nilotinib, erlotinib, vandetanib and canertinib) were also examined for their ability to potentiate doxorubicin-induced myocyte damage and induce an increase in intracellular doxorubicin levels. Support: CIHR and a Canada Research Chair in Drug Development to BBH. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 935. doi:1538-7445.AM2012-935