Abstract 1839: Lipid metabolism as target and modulator of KP1339 anticancer activity
Authors: Baier Dina Salome , Schoenhacker-Alte Beatrix , Pirker Christine , Englinger Bernhard , Mohr Thomas , Meier-Menches Samuel , Roehrl Clemens , Moser Patrick , Laemmerer Anna , Neuditschko Benjamin , Niederstaetter Laura , Brunmair Julia , Schaier Martin , Regner Benedikt , Nowikovsky Karin , Gerner Christopher , Koellensperger Gunda , Heffeter Petra , Keppler Bernhard Klaus , Berger Walter 
Published: September 2020

Abstract
Acquired therapy resistance of diverse cancer types frequently involves changed metabolic processes linked to altered cellular lipid uptake or de novo synthesis. In this study, colon and pancreatic cancer cells were selected for resistance to the lead ruthenium-anticancer complex sodium trans-[tetrachloridobis(1H-indazole)ruthenate(III)] (KP1339), currently in clinical development. KP1339 binds serum proteins and selectively accumulates in malignant tissue. This is reflected by mild adverse effects and a promising therapeutic window. However, potential resistance mechanisms against KP1339 are enigmatic so far.
HCT116 and Capan-1 cell models with acquired KP1339 resistance were established and investigated for altered gene expression profiles. mRNA data were confirmed on the protein level using immunoblotting. Lipid storage compartments (lipid droplets) were visualized fluorescently with Bodipy 493/503. The role of altered lipid metabolism components in KP1339 resistance was dissected utilizing specific pharmacological inhibitors. Mitochondrial oxygen consumption rate (OCR) and extracellular acidification rate (ECAR) were assessed by Seahorse XF analyses. Lipidomics and consecutive proteomics analysis were used to further characterize the resistance phenotype.
Resistance in both cell models was not based on a drug accumulation defect. In-depth bioinformatic analyses revealed major changes in the lipid metabolism associated with KP1339 resistance. Consistently, KP1339-resistant cells contained elevated lipid droplet levels. Hence, resistant cell models were hypersensitive towards the lipid-modulating agents triacsin C, statins, and orlistat. Unexpectedly, most of these inhibitors exerted even antagonistic activity when combined with KP1339 in parental and resistant cell models. In contrast, the ß-oxidation inhibitor etomoxir massively synergized with KP1339 and completely reverted acquired resistance. In the Seahorse Mito Stress Test, KP1339 severely reduced ECAR in sensitive HCT116 cells suggesting interference with glycolysis. Accordingly, KP1339-resistant cells exhibited clearly reduced spontaneous ECAR levels which, in contrast to the parental line, did not increase upon respiration inhibition by oligomycin. Upon KP1339 treatment, OCR was reduced in parental but stayed unchanged in resistant cells. Lipidomics confirmed distinctly enhanced lipid droplet component levels (e.g. triglycerides) associated with KP1339 resistance while proteomics indicated degradation of monocarboxylate transporters MCT-1/MCT-4.
In this study, we uncover an impact on lipid metabolism as vital player in response to and acquired resistance against the anticancer ruthenium compound KP1339. We suggest the development of rational combination schemes between lipid metabolism modulators, like etomoxir, and KP1339 for enhanced activity and resistance prevention. The respective preclinical in vivo experiments are currently initiated.
Citation Format: Dina Salome Baier, Beatrix Schoenhacker-Alte, Christine Pirker, Bernhard Englinger, Thomas Mohr, Samuel Meier-Menches, Clemens Roehrl, Patrick Moser, Anna Laemmerer, Benjamin Neuditschko, Laura Niederstaetter, Julia Brunmair, Martin Schaier, Benedikt Regner, Karin Nowikovsky, Christopher Gerner, Gunda Koellensperger, Petra Heffeter, Bernhard Klaus Keppler, Walter Berger. Lipid metabolism as target and modulator of KP1339 anticancer activity [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1839.