Transient Decrease in Tumor PO2 by 13C-Pyruvate Injection

Keita Saito¹, Shingo Matsumoto¹, Nallathamby Devasahayam¹, Sankaran Subramanian¹, Jeeva P. Munasinghe², Jan Henrik Ardenkjaer-Larsen³, Herman Douglas Morris², Martin J. Lizak², James B. Mitchell¹, Murali C. Krishna¹

MRI using hyperpolarized [1-¹³C]pyruvate is a promising tool for cancer diagnosis, but influences of exogenously injected pyruvate on tumor physiology were not well understood. Here, effects of pyruvate injection on tumor oxygen status were investigated using pulsed electron paramagnetic resonance imaging. Tumor pO₂ was remarkably decreased 30 min after [1-¹³C]pyruvate injection. The pO₂ decrease was transient, and the pO₂ recovered to the pre-injection level 5 h after the pyruvate injection. This transient decrease in the pO₂ influenced effects of X-irradiation: tumor growth suppression by X-irradiation was weakened when [1-¹³C]pyruvate was injected to mice 30 min before X-irradiation.