Poster Presentation The Annual Scientific Meeting of the Endocrine Society of Australia and the Society for Reproductive Biology 2014

Targeting DOHH and eIF5A to inhibit prostate cancer cell growth (#219)

Michael R Epis 1 , Keith M Giles 1 , Michael B Mathews 2 , Hartmut M Hanauske-Abel 2 , Peter J Leedman 1 3 4
  1. Laboratory for Cancer Medicine, Harry Perkins Institute of Medical Research, Nedlands, Western Australia, Australia
  2. Department of Biochemistry and Molecular Biology , New Jersey Medical School, Rutgers University, Newark, New Jersey, USA
  3. School of Medicine and Pharmacology, University of Western Australia, Perth, WA, Australia
  4. Centre for Medical Research, University of Western Australia, Nedlands, Western Australia, Australia

Understanding the molecular mechanisms producing androgen-independent castrate-resistant prostate cancer (CRPC) is an important objective in prostate cancer (PCa). We have substantial evidence for specific tumor suppressor miRNAs (miR-331-3p and miRNA-642-5p, hereafter referred to as miR-331 and miR-642, respectively) in PCa. Both miR-331 and miR-642 function, in part, in PCa via inhibition of expression of Deoxyhypusine Hydroxylase (DOHH), the enzyme that catalyzes the activation of eukaryotic translation initiation factor 5A (eIF5A), a protein essential for cell growth1. An inverse relationship exists between expression of miR-331/miR-642 and DOHH in PCa tissues1. There is increasing interest in identifying eIF5A inhibitors for cancer. Ciclopirox olamine (CPX) is an established topical antifungal drug that is being evaluated in clinical trials as a repositioned anti-cancer agent. Interestingly, CPX inhibits DOHH, and as a consequence hypusination of eIF5A. CPX has significant anti-tumor activity in breast cancer (MDA-231) and in a Phase I trial in AML patients, CPX was well tolerated. We aimed to investigate CPX on DOHH and eIF5A in PCa cells and its on PCa cell growth. We found that siRNA to DOHH mimicked the effects of each of miR-331/642 on DU-145 PCa cell growth, and inhibited production of hypusinated eIF5A. CPX effectively abrogated DOHH expression and eIF5A activation in DU-145 PCa cells. Further, CPX inhibited DU-145 and PC3 cell proliferation with an IC50 ~20 fold lower than for “normal” RWPE-1 prostate cells. Taken together these data suggest that CPX has significant activity to inhibit DOHH, and as a consequence activated eIF5A in PCa, which results in growth inhibition. Further, as the effects of CPX appear greater in cancer versus normal cells, this agent may have therapeutic potential in PCa treatment.

  1. Epis MR, et al. J Biol Chem, 2012: 287, 35251-35259.