Effects of Novel Anticancer Therapies on Cardiac Calcium Homeostasis

Abstract

Background: Tyrosine-kinase inhibitors (TKIs) are widely used in cancer treatment. Despite being more targeted than conventional chemotherapy, TKIs may exhibit substantial cardiotoxicity. Here, we aim to characterise underlying alterations of cardiomyocyte calcium homeostasis caused by the TKI sorafenib in order to identify potential protective co-treatments. Methods: Intracellular calcium transients (CaTs) were assessed at room temperature using laser scanning microscopy in electrically stimulated (0.5Hz), isolated murine C57BL/6 cardiomyocytes loaded with the calcium-sensitive fluorescent dye Fluo-4/AM (1.5μM). Myocytes were superfused with sorafenib (10μM) or vehicle control (n=21 and 20 cells, respectively, 7 hearts). Isoproterenol- (10nM) and caffeine-induced (30mM) responses were measured to assess beta-adrenergic reserve and sarcoplasmic reticulum (SR) calcium content, respectively. Western blots were performed for calcium-handling proteins phospholamban (PLB) and Ca2+/calmodulin-dependent protein kinase II (CaMKII), including their phosphorylated forms pPLB S16, pPLB T17, and pCaMKII T286. Custom-made R scripts were used for CaTs and Western blot analyses, and statistical testing. Results: Sorafenib-superfused cardiomyocytes showed a progressive decrease in systolic calcium transient amplitude reaching 52±8.1% of the baseline amplitude at the maximum drug effect (p

Date of Award	2017
Original language	English
Awarding Institution	Medical University Graz
Supervisor	Peter Rainer (Supervisor) & Simon Sedej (Co-supervisor)