Phospholipid dynamics in ex vivo lung cancer and normal lung explants Julia Lesko1, Alexander Triebl2, Elvira Stacher-Priehse3*, Nicole Fink-Neuböck4, Jörg Lindenmann4, Freyja-Maria Smolle-Jüttner4, Harald C. Köfeler2, Andelko Hrzenjak1,5, Horst Olschewski1,5, Katharina Leithner1,6 1Division of Pulmonology, Department of Internal Medicine, Medical University of Graz, Graz, Austria; 2Core Facility Mass Spectrometry and Lipidomics, ZMF, Medical University of Graz, Graz, Austria; 3Institute of Pathology, Medical University of Graz, Graz, Austria; 4Division of Thoracic and Hyperbaric Surgery, Medical University of Graz, Graz, Austria; 5Ludwig Boltzmann Institute for Lung Vascular Research, Graz, Austria; 6BioTechMed Graz, Graz, Austria In cancer cells, metabolic pathways are reprogrammed to promote cell proliferation and growth. While the rewiring of central biosynthetic pathways is being extensively studied, the dynamics of phospholipids in cancer cells are still poorly understood. In our study, we sought to determine de novo biosynthesis of glycerophospholipids (GPL) in lung cancer ex vivo explants and corresponding normal lung tissue from altogether six patients by utilizing a stable isotopic labelling approach. Incorporation of fully 13C-labelled glucose into the backbone of phosphatidylethanolamine (PE), phosphatidylcholine (PC) and phosphatidylinositol (PI) was analyzed by liquid chromatography/mass spectrometry. Lung cancer tissue showed significantly elevated isotopic enrichment within the glycerol backbone of PE, normalized to the incorporation into PI, when compared to normal lung tissue, however, the pool size of PE normalized to PI was smaller in tumor tissue. These findings indicate an enhanced PE turnover in lung cancer tissue. Elevated biosynthesis of PE in lung cancer tissue is supported by enhanced expression of the PE biosynthesis genes ETNK2 and EPT1 and lower levels of the PC and PI biosynthesis genes CHPT1 and CDS2 in different subtypes of lung cancer in publicly available datasets. Our study demonstrates that incorporation of glucose-derived carbons into the glycerol backbone of GPL can be monitored to study phospholipid dynamics in tumor explants and shows that PE turnover is elevated in lung cancer compared to normal lung tissue.