Beta-Catenin Nuclear Translocation In Colorectal Cancer Cells Is Suppressed By Pde10a Inhibition, Cgmp Elevation, And Activation Of Pkg

Phosphodiesterase 10A (PDE10A) is a cGMP and cAMP degrading PDE isozyme that is highly expressed in the brain striatum where it appears to play an important role in cognition and psychomotor activity. PDE10 inhibitors are being developed for the treatment of schizophrenia and Huntington9s disease and are generally well tolerated, possibly because of low expression levels in most peripheral tissues. We recently reported high levels of PDE10 in colon tumors and that genetic silencing of PDE10 by siRNA or inhibition with small molecule inhibitors can suppress colon tumor cell growth with a high degree of selectivity over normal colonocytes (Li et al., Oncogene 2015). These observations suggest PDE10 may have an unrecognized role in tumorigenesis. Here we report that the concentration range by which the highly specific PDE10 inhibitor, Pf-2545920 (MP-10), inhibited colon tumor cell growth parallels the concentration range required to increase cGMP and cAMP levels, and activate PKG and PKA, respectively. Moreover, PDE10 knockdown by shRNA reduced the sensitivity of colon tumor cells to the growth inhibitory activity of Pf-2545920. Pf-2545920 also inhibited the translocation of β-catenin to the nucleus, thereby reducing β-catenin mediated transcription of survivin, which resulted in caspase activation and apoptosis. This was determined to be through a PKG mediated pathway through the use of small molecule inhibitors of PKG and PKA. PDE10 mRNA was also found to be elevated in colon tumors compared with normal tissues in a cDNA array. We also report the increase in PDE10 mRNA in 50% of a small collection of human clinical specimens collected at the Mitchell Cancer Institute (n = 13). In addition, novel PDE10 inhibitor, MCI-030, reduced tumor size and activated PDE10 signaling mechanisms in vivo. These findings suggest that PDE10 can be targeted for cancer therapy or prevention whereby inhibition results in cGMP elevation and PKG activation to reduce β-catenin-mediated transcription of survival proteins leading to the selective apoptosis of cancer cells. Citation Format: Kevin J. Lee, Ashley S. Lindsey, Luciana Madeira da Silva, Alisa Trinh, Bernard Gary, Joel Andrews, Veronica Ramirez-Alcantara, Adam B. Keeton, Wen-Chi Chang, Margie Clapper, Gary A. Piazza. Beta-catenin nuclear translocation in colorectal cancer cells is suppressed by PDE10A inhibition, cGMP elevation, and activation of PKG. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 331.