Abstract 3046: Phosphodiesterase 4D (PDE4D) as a new drug target for prostate cancer

Abstract

Abstract Our laboratory used an insertional somatic mutagenesis screen in mice to identify novel genes that may drive prostate cancer initiation and progression. Using this screen, we have identified candidate prostate cancer genes including the candidate oncogene phosphodiesterase 4D (PDE4D). Investigation of PDE4D showed that it was over-expressed in human prostate cancer cell lines and in human prostate cancers. Stable knockdown of PDE4D by shRNA reduced the growth and migration of prostate cancer cells in vitro and in vivo. PDE4D has been implicated in the pathogenesis of chronic obstructive pulmonary disease (COPD). Several small molecule PDE4D selective inhibitors have been developed and tested in clinical trials for COPD. Although these studies showed that the inhibitors had modest efficacy as a therapy for COPD, they confirmed that the inhibitors were safe for use in humans at doses that inhibited PDE4D in vivo. Based on our previous studies with PDE4D, we postulated that PDE4D small molecule inhibitors would be candidate anti-prostate cancer drugs. Daily oral administration of PDE4D inhibitors, NVP-ABE171 or cilomilast, for 6 weeks significantly reduced the growth of LNCaP-C4 prostate cancer xenografts in immune-compromised mice. Under in vitro conditions in which prostate cancer cell growth was inhibited by either NVP-ABE171 or cilomilast, we also observed changes in the activation of potential downstream molecular targets of PDE4D inhibition. Affected pathways included the sonic hedgehog and mitogen-activated protein kinase pathways. We also tested the potential role of the PDE4D pathway in prostate cancer stromal-epithelial interactions by modeling these interactions using novel microchannel co-culture devices. In this context, PDE4D inhibitors reduced the activation of Shh pathway target genes in mesenchymal cells and reduced the proliferation of epithelial cancer cell lines, supporting the potential importance of the PDE4D pathway for prostate cancer stromal-epithelial interactions. We are continuing in vitro and in vivo studies with these candidate drugs to further support the use of NVP-ABE171 and cilomilast as anti-prostate cancer drugs and to understand their mechanism of action. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3046. doi:10.1158/1538-7445.AM2011-3046