Molecular imaging of tumor metabolism: Insight from pyruvate- and glucose-based deuterium MRI studies

Cancer diagnosis by metabolic MRI proposes to follow the fate of glycolytic precursors such as pyruvate or glucose, and their in vivo conversion into lactate. This study compares the ²H MRI outlooks afforded by these metabolites when targeting a pancreatic cancer model. Exogenously injected [3,3',3″-²H₃]-pyruvate was visible only briefly; it generated a deuterated lactate signal throughout the body that faded after ~5 min, showing a minor concentration bias at the rims of the tumors. [6,6'-²H₂]-glucose by contrast originated a lactate signal that localized clearly within the tumors, persisting for over an hour. Investigations alternating deuterated and nondeuterated glucose injections revealed correlations between the lactate generation and the glucose available at the tumor, evidencing a continuous and avid glucose consumption generating well-localized lactate signatures as driven by the Warburg effect. This is by contrast to the transient and more promiscuous pyruvate-to-lactate transformation, which seemed subject to transporter and kinetics effects. The consequences of these observations within metabolic MRI are briefly discussed.