Abstract 5157: Prolactin plays a role in regulating fatty acid synthesis and metabolism in the prostate cancer cell line PC-3

Abstract

Abstract Introduction: Prostate cancer (PCa) metabolism is unique from other cancers due to a high reliance on fatty acid (FA) break down for energy. This phenomenon of FA dependence is exemplified clinically by poor tumor detection by PET scanning, which makes proteins involved in FA synthesis and metabolism interesting therapeutic targets in PCa. Two important proteins for fat metabolism are fatty acid synthase (FASN) and carnitine palmitoyl-transferase I (CPT1). FASN is responsible for de novo synthesis of long-chain (LC) FA and its activation is tightly regulated. CPT1 is a rate-limiting enzyme, which shuttles LC-FA into the mitochondria for beta-oxidation. The hormone prolactin (PRL) plays a role in the normal prostate by increasing energy metabolism and citrate production. The receptor for PRL (PRLR) has 5 isoforms, which are speculated to have different signaling capabilities. Our lab has shown the ability of PRL to increase CPT1A, but not FASN, mRNA and protein levels in human breast cancer cells. We hypothesized that PRL plays a similar role in PCa FA synthesis and metabolism due to the known presence of PRLR in these cells. The objectives of this study were to 1) identify which PRLR isoforms are expressed 2) determine if mRNA or protein levels of FASN and CPT1A change in response to PRL dosing and 3) establish if PRLR isoform expression plays a role in the results obtained in objective #2. Methods: PNT1A (normal prostate epithelial) and PC-3 (PCa) cells were dosed with 0, 50 or 100 ng/ml PRL. The mRNA levels for CPT1A and FASN were measured with RT-qPCR. For protein expression of FASN and CPT1A 30 ug of protein was loaded onto SDS-PAGE gels, followed by transfer to PVDF membranes, incubated in primary and then secondary antibodies and finally ECL reagent was added to the membranes for band detection. Over-expression studies were performed using lipofectamine 2000 to transiently over-express the long form or a shorter truncated version of the PRLR that were cloned into an expression vector. Over-expression studies were analyzed using Western blotting for FASN and CPT1A as mentioned above. Results: Both PNT1A and PC-3 cell lines express various PRLR isoforms. PRL did not have a significant effect on FASN or CPT1A mRNA levels in either cell type. Western blotting revealed significant changes for FASN and CPT1A protein levels in PC-3 cells at the 100 ng/ml dose. PRLR isoform over-expression studies indicated that isoform expression does appear to be an important variable in how PRL affects FASN and CPT1A protein levels. Conclusion: This project indicates a role for PRL in regulating FA synthesis and metabolism in the PCa cell line PC-3. Regulation at the protein level appears to be influenced by the PRLR isoform that is predominately expressed. These results suggest that PRL and/or its receptors could be a therapeutic target in treating prostate cancer. This project was supported by funding provided from CIHR to GS. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5157. doi:1538-7445.AM2012-5157