Synthesis of [1‐<sup>13</sup>C‐5‐<sup>12</sup>C]‐alpha‐ketoglutarate enables noninvasive detection of 2‐hydroxyglutarate
Natsuko Miura, Chandrasekhar Mushti, Deepak Sail, Jenna E. AbuSalim, Kazutoshi Yamamoto, Jeffrey Brender, Tomohiro Seki, Deyaa I. AbuSalim, Shingo Matsumoto, Kevin Camphausen, Murali C. Krishna, Rolf E. Swenson, Aparna H. Kesarwala
Abstract
Isocitrate dehydrogenase 1 (IDH1) mutations that generate the oncometabolite 2‐hydroxyglutarate (2‐HG) from α‐ketoglutarate (α‐KG) have been identified in many types of tumors and are an important prognostic factor in gliomas. 2‐HG production can be determined by hyperpolarized carbon‐13 magnetic resonance spectroscopy (HP‐ 13 C‐MRS) using [1‐ 13 C]‐α‐KG as a probe, but peak contamination from naturally occurring [5‐ 13 C]‐α‐KG overlaps with the [1‐ 13 C]‐2‐HG peak. Via a newly developed oxidative‐Stetter reaction, [1‐ 13 C‐5‐ 12 C]‐α‐KG was synthesized. α‐KG metabolism was measured via HP‐ 13 C‐MRS using [1‐ 13 C‐5‐ 12 C]‐α‐KG as a probe. [1‐ 13 C‐5‐ 12 C]‐α‐KG was synthesized in high yields, and successfully eliminated the signal from C5 of α‐KG in the HP‐ 13 C‐MRS spectra. In HCT116 IDH1 R132H cells, [1‐ 13 C‐5‐ 12 C]‐α‐KG allowed for unimpeded detection of [1‐ 13 C]‐2‐HG. 12 C‐enrichment represents a novel method to circumvent spectral overlap, and [1‐ 13 C‐5‐ 12 C]‐α‐KG shows promise as a probe to study IDH1 mutant tumors and α‐KG metabolism.