Abstract B023: Identification and biochemical validation of piperlongumine as a potent therapeutic against neuroendocrine prostate cancer

Abstract

Abstract Introduction and Objectives: Recent studies have highlighted the existence of a highly lethal and drug-resistant variant of prostate cancer (PCa) termed neuroendocrine prostate cancer (NEPC). We have used a genomics-based drug-repositioning approach to identify piperlongumine, a natural product constituent of the fruit of the long pepper (Piper longum), as a potential therapeutic against NEPC. The efficacy of this drug was tested in the NEPC cell line model NCI-H660 and compared to several other PCa cell lines in a modified WST-1 assay. Preclinical testing in mouse xenograft models of NEPC was also undertaken. Finally, the ability of piperlongumine to inhibit p-STAT3 signaling and promote apoptosis in cell lines and extracted tumors were measured by Western blot analyses. Methods: PCa cell lines (LNCaP, 22Rv1, Du145, PC3, H660, and RWPE) were grown in complete media (RPM1 10% FBS, Advanced DMEM 5% FBS, or Keratinocyte-SFM) and treated with piperlongumine for 3 or 7 days. IC50 values were generated from WST assay data using Prism6. Nude mice (n=5) were injected with 1.5x106 H660 cells on each flank, and intraperitoneally administered with either 2.5mg/kg piperlongumine (n=3) or DMSO (n=2) daily for 3 weeks after tumors formed 200mm3 in volume. Tumor volume was measured daily with calipers. Western blot analyses were performed on protein lysates extracted from tumors and PCa cells treated with 0-10 μM of drug. Results: Piperlongumine was highly effective in inhibiting the growth of H660 cells (IC50 = 0.4 μM) compared to LNCaP, 22Rv1, Du145, PC3, and RWPE cells. On average, the growth rate of untreated tumors was 2.7 times greater than those treated was piperlongumine. Treated H660 cells exhibited significant inhibition of p-STAT3 and increases in cPARP1 levels while other cell lines displayed little to no fluctuation. Conclusions: Using drug-repositioning approaches we have identified a lead compound that inhibits the growth of the highly drug-resistant NEPC cell line NCI-H660. Remarkably, piperlongumine happens to be a water-soluble plant product with no known side effects. Citation Format: Kamlesh K. Yadav, Khader Shameer, Jennifer A. Stockert, Cordelia Elaiho, Ben Readhead, Shalini S. Yadav, Joel Dudley, Ashutosh K. Tewari. Identification and biochemical validation of piperlongumine as a potent therapeutic against neuroendocrine prostate cancer [abstract]. In: Proceedings of the AACR Special Conference: Prostate Cancer: Advances in Basic, Translational, and Clinical Research; 2017 Dec 2-5; Orlando, Florida. Philadelphia (PA): AACR; Cancer Res 2018;78(16 Suppl):Abstract nr B023.