and treated as chronic, rather than terminal, diseases. Although the side effects of targeted therapies like TKIs are considered mild compared to traditional chemotherapeutics, patients CAL-101 PI3K inhibitor may now be exposed to these drugs for years rather than months. However, the long term physiological consequences of suppressed EGFR activity are unknown. A wealth of evidence has established that all four ERBB family members are essential to normal cardiovascular development. A role for ERBB signaling in adult cardiac homeostasis is also emerging. Three of the four receptors, EGFR, ERBB2, and ERBB4, are detected in the adult human and mouse heart, among these ERBB4 appears to be the most abundant. The expression and activity of ERBB2 and ERBB4 receptors are depressed in clinical and experimentally induced heart failure and signaling via NRG1 to ERBB2/ ERBB4 heterodimers is critical for adult cardiomyocyte survival.
The importance of this signaling pathway in normal cardiac physiology was not fully recognized until the unexpected and lethal cardiomyopathy CT99021 252917-06-9 reported in breast cancer clinical trials using trastuzmab, a humanized monoclonal antibody targeting ERBB2. Subsequently, mouse models with ventricular specific deletion of ERBB2 or ERBB4 were found to recapitulate the cardiac phenotype observed in clinical trials. More recently, signaling through EGFR was shown to provide cardioprotection against stress induced injury, and reduction in EGFR activity impacts cardiomyocyte hypertrophy and survival.
To date, no in vivo studies have specifically assessed the effects of chronically reduced EGFR activity on adult cardiac function, as might be expected with continuous drug exposure to TKIs, despite the fact that mutant mouse models have shown considerable similarities to drug induced toxicities in the oncology clinic. To address this question, we used EKB 569 an EGFR selective irreversible TKI, and AG 1478 a reversible TKI also selective for EGFR, to assess the effects of chronic oral exposure to these drugs on cardiac function and pathology in wild type mice. Materials and methods 1 Animals and pharmacologic treatment All mice were bred in house or obtained from The Jackson Laboratory. Male and female wildtype C57BL/6J mice were randomly assigned to either AIN 93G control chow or AIN 93G chow containing the EGFR small molecule inhibitors EKB 569 or AG 1478 equivalent to 20 or 19.
2 mg/ kg body weight/day, respectively. Mice were weighed and provided diet ad libitum for 90 days. Body weights were measured at baseline and 15, 30, 60 and 90 days of treatment. Due to limited availability of EKB 569, studies were only performed in female mice to verify that results obtained with AG 1478 were not specific to one class of inhibitor. Similarly, practical issues imposed by a chronic dietary exposure regimen and the limited supply or high cost prohibited studies employing a range of doses via oral delivery. The dose chosen for the present studies was based on those commonly used for cancer inhibitory studies and that required to achieve a 50% reduction in the mean number of polyps using the ApcMin model, a common measure for EGFR inhibitors. In a separate experiment to evaluate efficacy of AG 1478 oral delivery, B6 ApcMin/ weanlings of both sexes were randomly assigned to either AIN 93G control chow or AIN 93G chow containing the EGFR small molecule inhibitor AG 147