Hyperpolarized [1-13C]-pyruvate magnetic resonance spectroscopic imaging of prostate cancer in vivo predicts efficacy of targeting the Warburg effect

Purpose:  To evaluate the potential of hyperpolarized [1-¹³C]-pyruvate magnetic resonance spectroscopic imaging (MRSI) of prostate cancer as a predictive biomarker for targeting the Warburg effect. Experimental Design:  Two human prostate cancer cell lines (DU145 and PC3) were grown as xenografts.  The conversion of pyruvate to lactate in xenografts was measured with hyperpolarized [1-¹³C]-pyruvate MRSI after systemic delivery of [1-¹³C] pyruvic acid.  Steady state metabolomic analysis of xenograft tumors was performed with mass spectrometry and steady state lactate concentrations were measured with proton (¹H) MRS.  Perfusion and oxygenation of xenografts was measured with electron paramagnetic resonance (EPR) imaging with OX063. Tumor growth was assessed after lactate dehydrogenase (LDH) inhibition with FX-11 (42 µg/mouse/day for 5 days x 2 weekly cycles).  Lactate production, pyruvate uptake, extracellular acidification rates and oxygen consumption of the prostate cancer cell lines was analyzed in vitro.  LDH activity was assessed in tumor homogenates.Results: DU145 tumors demonstrated an enhanced conversion of pyruvate to lactate with hyperpolarized [1-¹³C]-pyruvate MRSI compared to PC3, and a corresponding greater sensitivity to LDH inhibition.  No difference was observed between PC3 and DU145 xenografts in steady state measures of pyruvate fermentation, oxygenation, or perfusion.  The two cell lines exhibited similar sensitivity to FX-11 in vitro.  LDH activity correlated to FX-11 sensitivity. Conclusions: Hyperpolarized [1-¹³C]-pyruvate MRSI of prostate cancer predicts efficacy of targeting the Warburg effect.

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