Prostate cancer (PCa) is the most common cancer in men, and the global burden of the disease is rising. The majority of PCa deaths are due to metastasis that are highly resistant to current hormonal treatments; this state is called castration-resistant prostate cancer (CRPC). In this study, we focused on the role of the lipid catabolism enzyme CPT1A in supporting CRPC growth in an androgen-dependent manner. We found that androgen withdrawal promoted the growth of CPT1A over-expressing (OE) tumors while it decreased the growth of CPT1A under-expressing (KD) tumors, increasing their sensitivity to enzalutamide. Mechanistically, we found that CPT1A-OE cells burned more lipid and showed increased histone acetylation changes that were partially reversed with a p300 specific inhibitor. Conversely, CPT1A-KD cells showed less histone acetylation when grown in androgen-deprived conditions. Our results suggest that CPT1A supports CRPC by supplying acetyl groups for histone acetylation, promoting growth and antiandrogen resistance.

E16551 Background: 2-deoxy-2-[18F]fluoro-D-glucose positron emission tomography (FDG-PET) is a widely-used imaging modality for many cancers; however, its utility in prostate cancer is limited. Fatty acid oxidation (FAO) is a primary source of energy for early prostate cancer. We previously demonstrated that FAO inhibition in prostate cancer mouse models resulted in increased glucose metabolism and enhanced tumor FDG uptake, with peak uptake at 24 hours. To validate these preclinical findings, we conducted a pilot study to evaluate whether a partial FAO inhibitor, ranolazine, increases tumor FDG uptake on PET imaging for prostate cancer. Methods: Prostate cancer patients with untreated localized cancer (arm 1) and with metastatic disease on hormonal or other therapy (arm 2) were enrolled and underwent baseline and post-treatment FDG-PET/CT scans (standard dose of 10 mCi FDG). Ranolazine 1000mg PO BID x 2 doses was given within 24-48 hours of the second scan. The primary objective was to evaluate the rate of successful enhancement of FDG uptake on PET imaging, based on one or more of the following criteria: 30% increase in maximum SUV with an absolute change of 2 units; 30% increase in mean SUV with an absolute change of 0.75 units; or 20% increase in mean SUV with an absolute change of 1 unit. Results: Eleven patients (four in arm 1, seven in arm 2) were enrolled. Ranolazine was well tolerated by all participants, with no adverse effects observed. Both increases and decreases in SUV uptake were observed on the post-ranolazine scans. No patient met the predefined criteria for successful enhancement of FDG uptake. There was an incidental finding of thyroid cancer seen in one patient that was discovered on PET imaging. The study was closed early due to the emerging clinical availability of alternative and effective PET imaging modalities such as [¹¹C] choline, [¹⁸F] fluciclovine, [⁶⁸Ga] PSMA, and [¹⁸F] sodium fluoride. Conclusions: Given the small sample size, we were not able to make any firm conclusions. In this limited study, ranolazine treatment did not result in enhanced FDG-PET-tumor detection. ClinicalTrials.gov identifier: NCT01992016. Supported by the William Meyn Foundation; NIH/NCI P30CA46934, 5K12CA086913, CA168934; ACS RSG-16-256-01-TBE; Colorado Translational Research Imaging Center Pilot Award; Paul Sandoval Cancer Research Summer Fellowship. Clinical trial information: NCT01992016.