Gallagher F.A.,University of Cambridge |
Kettunen M.I.,University of Cambridge |
Day S.E.,University of Cambridge |
Hu D.-E.,University of Cambridge |
And 5 more authors.
Magnetic Resonance in Medicine | Year: 2011
Dynamic nuclear polarization can be used to increase the sensitivity of solution state 13C magnetic resonance spectroscopy by four orders of magnitude. We show here that [1- 13C]glutamate can be polarized to 28%, representing a 35,000-fold increase in its sensitivity to detection at 9.4 T and 37°C. The metabolism of hyperpolarized glutamate to α-ketoglutarate, catalyzed by the enzyme alanine transaminase, was detected in vitro in human hepatoma cells (HepG2). Incubation of the cells with sodium pyruvate increased the level of the hyperpolarized label in the α-ketoglutarate pool, with an associated increase in the apparent rate constant describing flux of hyperpolarized 13C label between glutamate and α-ketoglutarate. The metabolism of hyperpolarized glutamate was observed in vivo following coadministration of pyruvate in a murine lymphoma model. This represents a new method to probe glutamate metabolism and citric acid cycle activity in vivo; as glutamate is an endogenous molecule, it has the potential to be used in the clinic. Magn Reson Med, 2011. © 2011 Wiley-Liss, Inc. Copyright © 2011 Wiley-Liss, Inc. Source
Karlsson M.,Imagnia AB |
Jensen P.R.,Imagnia AB |
In't Zandt R.,Imagnia AB |
Gisselsson A.,Imagnia AB |
And 4 more authors.
International Journal of Cancer | Year: 2010
Powerful analytical tools are vital for characterizing the complex molecular changes underlying oncogenesis and cancer treatment. This is particularly true, if information is to be collected in vivo by noninvasive approaches. In the recent past, hyperpolarized 13C magnetic resonance (MR) spectroscopy has been employed to quickly collect detailed spectral information on the chemical fate of tracer molecules in different tissues at high sensitivity. Here, we report a preclinical study showing that α-ketoisocaproic acid (KIC) can be used to assess molecular signatures of tumors with hyperpolarized MR spectroscopy. KIC is metabolized to leucine by the enzyme branched chain amino acid transferase (BCAT), which is found upregulated in some tumors. BCAT is a putative marker for metastasis and a target of the proto-oncogene c-myc. Very different fluxes through the BCAT-catalyzed reaction can be detected for murine lymphoma (EL4) and rat mammary adenocarcinoma (R3230AC) tumors in vivo. EL4 tumors show a more than 7-fold higher hyperpolarized 13C leucine signal relative to the surrounding healthy tissue. In R3230AC tumor on the other hand branched chain amino acid metabolism is not enhanced relative to surrounding tissues. The distinct molecular signatures of branched chain amino acid metabolism in EL4 and R3230AC tumors correlate well with ex vivo assays of BCAT activity. © 2009 UICC. Source