title: Hyperpolarized (13)C-lactate to (13)C-bicarbonate ratio as a biomarker for monitoring the acute response of anti-vascular endothelial growth factor (anti-VEGF) treatment.
abstract: Hyperpolarized [1-(13)C]pyruvate MRS provides a unique imaging opportunity to study the reaction kinetics and enzyme activities of in vivo metabolism because of its favorable imaging characteristics and critical position in the cellular metabolic pathway, where it can either be reduced to lactate (reflecting glycolysis) or converted to acetyl-coenzyme A and bicarbonate (reflecting oxidative phosphorylation). Cancer tissue metabolism is altered in such a way as to result in a relative preponderance of glycolysis relative to oxidative phosphorylation (i.e. Warburg effect). Although there is a strong theoretical basis for presuming that readjustment of the metabolic balance towards normal could alter tumor growth, a robust noninvasive in vivo tool with which to measure the balance between these two metabolic processes has yet to be developed. Until recently, hyperpolarized (13)C-pyruvate imaging studies had focused solely on [1-(13)C]lactate production because of its strong signal. However, without a concomitant measure of pyruvate entry into the mitochondria, the lactate signal provides no information on the balance between the glycolytic and oxidative metabolic pathways. Consistent measurement of (13)C-bicarbonate in cancer tissue, which does provide such information, has proven difficult, however. In this study, we report the reliable measurement of (13)C-bicarbonate production in both the healthy brain and a highly glycolytic experimental glioblastoma model using an optimized (13)C MRS imaging protocol. With the capacity to obtain signal in all tumors, we also confirm for the first time that the ratio of (13)C-lactate to (13)C-bicarbonate provides a more robust metric relative to (13)C-lactate for the assessment of the metabolic effects of anti-angiogenic therapy. Our data suggest a potential application of this ratio as an early biomarker to assess therapeutic effectiveness. Furthermore, although further study is needed, the results suggest that anti-angiogenic treatment results in a rapid normalization in the relative tissue utilization of glycolytic and oxidative phosphorylation by tumor tissue.
authors.affiliation: Department of Radiology, Stanford University, Stanford, CA, USA.
authors.forename: Jae Mo
authors.initials: JM
authors.lastname: Park
authors.affiliation: Department of Radiology, Stanford University, Stanford, CA, USA.
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Spielman
authors.affiliation: Department of Radiology, Stanford University, Stanford, CA, USA.|Biosciences Division, SRI International, Menlo Park, CA, USA.
authors.forename: Sonal
authors.initials: S
authors.lastname: Josan
authors.affiliation: Department of Neurology and Neurological Sciences, Stanford University, Palo Alto, CA, USA.
authors.forename: Taichang
authors.initials: T
authors.lastname: Jang
authors.affiliation: Department of Neurology and Neurological Sciences, Stanford University, Palo Alto, CA, USA.
authors.forename: Milton
authors.initials: M
authors.lastname: Merchant
authors.affiliation: Applied Science Laboratory West, GE Healthcare, Menlo Park, CA, USA.
authors.forename: Ralph E
authors.initials: RE
authors.lastname: Hurd
authors.affiliation: Biosciences Division, SRI International, Menlo Park, CA, USA.|Department of Diagnostic Radiology and Nuclear Medicine, University of Maryland, Baltimore, MD, USA.
authors.forename: Dirk
authors.initials: D
authors.lastname: Mayer
authors.affiliation: Department of Neurology and Neurological Sciences, Stanford University, Palo Alto, CA, USA.
authors.forename: Lawrence D
authors.initials: LD
authors.lastname: Recht
mesh_terms: D000818:Animals; D001639:Bicarbonates / Q000378:metabolism*; D014408:Biomarkers, Tumor / Q000378:metabolism*; D001932:Brain Neoplasms / Q000378:metabolism / Q000473:pathology; D002247:Carbon Isotopes; D002452:Cell Count; D049109:Cell Proliferation; D004734:Energy Metabolism; D005910:Glioma / Q000378:metabolism / Q000473:pathology; D019344:Lactic Acid / Q000378:metabolism*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D055442:Metabolome; D017208:Rats, Wistar; D047368:Tumor Burden; D042461:Vascular Endothelial Growth Factor A / Q000037:antagonists & inhibitors* / Q000378:metabolism
chemical_list: D001639:Bicarbonates; D014408:Biomarkers, Tumor; D002247:Carbon Isotopes; D042461:Vascular Endothelial Growth Factor A; D019344:Lactic Acid
keywords: angiogenesis; bevacizumab; cancer therapy responses; glioma; hyperpolarized 13C