Abstract 371: Utilizing metabolic pathways to improve diagnosis and risk stratification of prostate cancer

Abstract

Prostate cancer has well-characterized changes that take place metabolically in the citric acid cycle (CAC) such as increased lactate formation, reversal of physiologic buildup of citrate and breakdown into downstream CAC products. Metabolic MR spectroscopy utilizing 13C-labeled pyruvate now allows for clinical characterization of metabolic pathways in tissue. However, the traditionally utilized substrate of [1-13C]pyruvate has limitations because as the pyruvate is broken down, the labeled carbon does not enter the CAC and instead is lost as CO2. We propose that [2-13C]pyruvate, is better to characterize changes in the CAC. Specifically, [2-13]C-pyruvate can be converted to 13C-labeled acetyl CoA and subsequently metabolized in the CAC as 13C-labeled intermediate compounds (such as glutamate which rapidly pools alpha-ketogluterate). Alternatively in altered bioenergetic states, [2-13C]pyruvate is reduced to 13C-labeled lactate (Warburg effect) or transaminated to 13C-labeled alanine. By exposing prostate cancer cells to [2-13C]pyruvate and determining the relative labeling of lactate, glutamate, and alanine, we can elucidate which metabolic pathways (CAC, Warburg, transamination) are utilized in prostate cancer metabolism. The aim of this study was to determine how the metabolism of [2-13C]pyruvate via the CAC, reduction to lactate, and transamination differed in high and low malignancy prostate cancer cells.Methods: Tumorigenic prostate cells LNCaP and PC3 were exposed a medium containing [2-13C]pyruvate for 4 hours. PCA extraction was then performed to obtain the metabolites. 13C labeled compounds formed intracellularly and those released into the medium were analyzed using NMR chemical shifts with focus on peaks associated with pyruvate, lactate, alanine, glutamate, and other compounds related to the CAC. Dioxane was used as an internal standard for NMR characterization. Results: The labeled carbon from the [2-13C]pyruvate can be identified in the downstream metabolites of the citric acid cycle, after reduction to lactate, and/or transamination by determining labeled metabolites by 13C-NMR analysis. This allows for the ability to calculate the relative metabolism of pyruvate via the three pathways; transamination (74%), lactate formation (16%), and CAC (10%). Conclusions: [2-13C]pyruvate can be successfully utilized as a tool to explore the alterations in pathways of metabolism, including the citric acid cycle, in prostate cancer cells. Citation Format: Aymen Alqazzaz, Dexue Fu, Arman Karimi, Gustavo Ferreira, Mary McKenna, Mohummad M. Siddiqui. Utilizing metabolic pathways to improve diagnosis and risk stratification of prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 371.