Abstract #0673

Detection of inflammatory cell function using 13C MRS of hyperpolarized 13C-labeled arginine

Chloe Najac¹, Myriam M Chaumeil¹, Gary Kohanbash², Caroline Guglielmetti³, Jeremy Gordon¹, Hideho Okada², and Sabrina M Ronen¹

¹Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA, United States, ²Neurological Surgery, University of California San Francisco, San Francisco, CA, United States, ³Bio-Imaging Lab, University of Antwerp, Antwerpen, Belgium

Myeloid-derived suppressor cells (MDSCs) are inflammatory cells in the tumor microenvironment that inhibit T-cell-mediated immunosuppression by expressing high levels of arginase. Arginase catalyzes the breakdown of arginine into urea. To monitor the enzymatic conversion, we developed a new hyperpolarized (HP) probe, namely [guanido-¹³C]-arginine. We first characterized the probe and confirmed the production of HP ¹³C urea in solution with different arginase concentrations. Then, we demonstrated its potential to probe the increase in arginase activity in MDSCs. This new HP probe could serve as a readout of MDSC function in tumor and its inhibition following MDSC-targeted immunotherapies.

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