PROJECT SUMMARY The central aim of this proposal is to apply a method for high resolution imaging of interstitial pH using hyperpolarized 13C magnetic resonance imaging to the detection of aggressive, potentially lethal disease in prostate cancer. We have very recently developed a method for production of a highly concentrated and polarized solution of hyperpolarized 13C bicarbonate through polarization of a precursor, glycerol carbonate, and subsequent hydrolysis. This method overcomes many of the limitations of previously described pH imaging methods and has a strong potential to allow for clinical translation. Prostate cancer presents with a heterogeneous disease course, and there is an urgent unmet clinical need for improved biomarkers for the detection or exclusion of aggressive, potentially lethal disease. One potential prognostic imaging biomarker in prostate cancer is acidic interstitial pH, which is associated with local invasion and metastases in animal models in a variety of cancers. Thus, a high resolution, clinically translatable method of imaging interstitial pH would have significant impact and could find immediate utility in initial staging of men with low or intermediate risk prostate cancer. The goal of this proposal is to test the ability of a recently developed hyperpolarized 13C magnetic resonance imaging method targeting interstitial acidity to predict high grade disease and subsequent progression in murine models of prostate cancer, and to develop suitable production and quality control methods for subsequent clinical translation. In specific aim 1, the correlation between interstitial acidity, high grade disease, and disease progression is studied in the transgenic adenocarcinoma of the prostate (TRAMP) animal model. In specific aim 2, this correlation is further validated in new, more clinically relevant models of prostate cancer, and the fundamental molecular mechanisms underpinning interstitial acidity are studied through pharmacologic modulation of various pathways. In specific aim 3, the production and imaging methods are optimized and suitable quality control measures are generated for subsequent clinical translation. If completed, the experiments outlined in this proposal would cement interstitial acidity as an imaging biomarker for aggressive, potentially lethal prostate cancer in animal models, elucidate molecular mechanisms underlying the phenomenon, and set the stage for subsequent clinical translation in men with prostate cancer.