Implementing Reverse Phase Protein Array profiling as a sensitive method for the early pre-clinical detection of off-target toxicities associated with Sunitinib Malate.

The tyrosine kinase inhibitor (TKI) sunitinib is a multi-targeted agent approved across multiple cancer indications. Nevertheless, since approval, data has emerged to describe a worrisome side effect profile including hypertension, hand-foot syndrome, fatigue, diarrhoea, mucositis, proteinuria and (rarely) congestive heart failure. It has been hypothesised that the observed multi-parameter toxicity profile is related to 'on-target' kinase inhibition in 'off-target' tissues. Herein, to interrogate off-target effects in pre-clinical studies, a reverse phase protein array (RPPA) approach was employed. Mice were treated with sunitinib (40 mg/kg) for 4 weeks, following which critical organs were removed. The Zeptosens RPPA platform was employed for protein expression analysis. Differentially expressed proteins associated with damage and/or stress were found in the majority of organs from treated animals. Proteins differentially expressed in the heart were associated with myocardial hypertrophy, ischaemia/reperfusion and hypoxia. However, hypertrophy was not evidenced on histology. Mild proteinuria was observed, however no changes in renal glomerular structure were visible via electron microscopy. In skin, proteins associated with cutaneous inflammation, keratinocyte hyper-proliferation, and increased inflammatory response were differentially expressed. We posit that pre-clinical implementation of a combined histopathological/RPPA approach provides a sensitive method to mechanistically elucidate the early manifestation of TKI on-target / organ off-target toxicities. This article is protected by copyright. All rights reserved.