Original Research In Vivo 31 P Magnetic Resonance Spectroscopic Imaging (MRSI) for Metabolic Profiling of Human Breast Cancer Xenografts Morteza Esmaeili, MSc, 1 * Siver A. Moestue, PhD, 1,2 Bob C. Hamans, MSc, 3 Andor Veltien, BS, 3 Alexandr Kristian, MSc, 4,5 Olav Engebra ˚ten, PhD, 5,6 Gunhild M. Mælandsmo, PhD, 4 Ingrid S. Gribbestad, PhD, 1 Tone F. Bathen, PhD, 1 and Arend Heerschap, PhD 1,3 Purpose: To study cancer associated with abnormal metabolism of phospholipids, of which several have been proposed as biomarkers for malignancy or to monitor response to anticancer therapy. We explored 3D 31 P mag- netic resonance spectroscopic imaging (MRSI) at high magnetic field for in vivo assessment of individual phos- pholipids in two patient-derived breast cancer xenografts representing good and poor prognosis (luminal- and basal-like tumors). Materials and Methods: Metabolic profiles from luminal-like and basal-like xenograft tumors were obtained in vivo using 3D 31 P MRSI at 11.7T and from tis- sue extracts in vitro at 14.1T. Gene expression analysis was performed in order to support metabolic differences between the two xenografts. Results: In vivo 31 P MR spectra were obtained in which the prominent resonances from phospholipid metabolites were detected at a high signal-to-noise ratio (SNR >7.5). Metabolic profiles obtained in vivo were in agreement with those obtained in vitro and could be used to discriminate between the two xenograft models, based on the levels of phosphocholine, phosphoethanolamine, glycerophospho- choline, and glycerophosphoethanolamine. The differen- ces in phospholipid metabolite concentration could partly be explained by gene expression profiles. Conclusion: Noninvasive metabolic profiling by 3D 31 P MRSI can discriminate between subtypes of breast cancer based on different concentrations of choline- and ethanolamine-containing phospholipids. Key Words: phospholipid; choline metabolism; phospho- rus MR spectroscopic imaging; high field; ethanolamine kinase; basal-like J. Magn. Reson. Imaging 2014;00:000–000. V C 2014 Wiley Periodicals, Inc. ADVANCES IN MOLECULAR TECHNOLOGIES have contributed to a substantial increase of our know- ledge of tumor growth. However, translating this knowledge to clinical practice is challenging. A nonin- vasive, reliable, and sensitive tool for the detection of biomarkers, such as certain metabolites relevant in the disease process, could improve this translation (1,2). In oncology, choline- and ethanolamine- containing phospholipids have attracted attention as potential metabolic biomarkers (3). They are major precursor molecules of cell membranes and play both structural and regulatory roles in cell metabolism and oncogenic signaling (3). To facilitate their use as bio- markers, a deeper understanding of their biology as well as noninvasive methods for their detection is needed. Changes in the tissue levels of these metabolites can be recorded in vivo by magnetic resonance spectroscopy (MRS) (3). Proton ( 1 H) MRS has been widely used to study the increased total choline levels (tCho) in brain 1 Department of Circulation and Medical Imaging, Norwegian Univer- sity of Science and Technology (NTNU), Trondheim, Norway. 2 St. Olavs University Hospital, P.O. Box 3250 Sluppen, N-7006, Trondheim, Norway. 3 Department of Radiology, Radboud University Nijmegen Medical Center, Nijmegen, The Netherlands. 4 Department of Tumor Biology, Institute for Cancer Research, Oslo University Hospital, Montebello, Oslo, Norway. 5 Institute for Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway. 6 Department of Oncology, Oslo University Hospital, Oslo, Norway. Contract grant sponsor: Norwegian University of Science and Tech- nology (NTNU); Contract grant sponsor: Norwegian Cancer Society and the Norwegian Breast Cancer Society; Contract grant number: 2209215-2011; Contract grant sponsor: Norwegian Research Coun- cil; Contract grant number: 175459/V50, 186479/V50, 183379/ S10, and 183621/S10; Contract grant sponsor: Liaison Committee between the Central Norway Regional Health Authority (RHA) and the Norwegian University of Science and Technology; Contract grant number: 46056655; Contract grant sponsor: Norwegian Research School in Medical Imaging (Travel grants M.E. and S.A.M.). Present affiliation for Bob C. Hamans: Jeroen Bosch Hospital, Den Bosch, the Netherlands (BCH). *Address reprint requests to: M.E., Department of Circulation and Medical Imaging, Norwegian University of Science and Technology (NTNU), P.O. Box 8905, N-7491 Trondheim, Norway. E-mail: m.esmaeili@ntnu.no Received October 1, 2013; Accepted January 20, 2014. DOI 10.1002/jmri.24588 View this article online at wileyonlinelibrary.com. JOURNAL OF MAGNETIC RESONANCE IMAGING 00:000–000 (2014) CME V C 2014 Wiley Periodicals, Inc. 1