Hyperpolarized 13C imaging of mitochondrial metabolism for improved characterization of prostate cancer

University Of Maryland Baltimore, Baltimore MD

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Abstract

In keeping with the mission of the NIH to support research ?with respect to the cause, diagnosis, prevention, and treatment of cancer? (NCI) and ?of new biomedical imaging and bioengineering techniques and devices to fundamentally improve the detection, treatment, and prevention of disease? (NIBIB), the overarching goal of this proposal is to leverage metabolic alterations in cancer cells for the noninvasive diagnosis and characterization of prostate cancer (PCa), the second leading cause of cancer death in men. Simultaneously, almost 90% of men with PCa will die of other causes while upwards of 40% of men with PCa are under-staged on initial diagnosis. Therefore, the ability to stratify the risk of PCa aggressiveness early and accurately represents one of the main unmet clinical needs in the management of PCa patients. Targeted magnetic resonance (MR)/ultrasound fusion-guided biopsy has highlighted the clinical benefits of PCa imaging advances as it improves diagnostic accuracy. However, further improvement is needed, as the sensitivity for identification of intermediate to high-risk PCa is still only 77%. With a growing interest into cancer metabolic reprogramming, new research targets local metabolic activity to improve our ability to characterize the disease. The recent development of hyperpolarized (HP) 13C MR spectroscopy (MRS) enables for the first time the real-time noninvasive measurement of critical dynamic metabolic processes in vivo. So far the most widely used substrate is [1-13C]pyruvate (Pyr) and it has been shown in both preclinical and clinical studies that its conversion to lactate (Lac) is sensitive to the high glycolytic rates in tumors (Warburg effect). Another hallmark of cancer is so-called glutaminolysis, where glutamine/glutamate (Glu) is used in energy metabolism, and, specifically for PCa, derangements surrounding citrate (Cit) metabolism. However, both these alterations of mitochondrial metabolism are not detectable with [1-13C]Pyr as the HP label is released as 13CO2 in the conversion to acetyl coenzyme A. Our preliminary findings of using HP [2-13C]Pyr in a glioma rat model demonstrate that imaging Pyr products beyond Lac can provide valuable information on the complex interplay between glycolytic and oxidative metabolism. Therefore, we propose to develop a HP 13C MRS-based approach for noninvasive assessment of PCa by exploiting the metabolic reprogramming of tumor cells with respect to multiple bioenergetics pathways. Specifically, we will develop optimized MR acquisition and quantification techniques for improved metabolic imaging of HP [2-13C]Pyr and its metabolic products [2-13C]Lac, [2-13C]Cit, and [5-13C]Glu enabling the simultaneous measurement of both glycolytic and mitochondrial metabolism (Aim 1). Secondly, we will evaluate these techniques in murine models of PCa to noninvasively assess tumor aggressiveness and response to metformin treatment (Aim 2). Considering the successful completion of the first Phase 1 clinical trial of HP [1-13C]Pyr, there is a clear translational path of this methodology for the improved diagnosis, monitoring, and therapeutic evaluation of PCa patients.