784 OVERCOMING RAD001 TRIGGERED RESISTANCE IN PROSTATE CANCER CDK1-CYCLIN B COMPLEX

Abstract

You have accessJournal of UrologyProstate Cancer: Basic Research IV1 Apr 2012784 OVERCOMING RAD001 TRIGGERED RESISTANCE IN PROSTATE CANCER CDK1-CYCLIN B COMPLEX Igor Tsaur, Jasmina Makarevic, Michael Reiter, Martin Kurosch, Georg Bartsch, Christoph Wiesner, Steffen Wedel, Axel Haferkamp, and Roman Blaheta Igor TsaurIgor Tsaur Frankfurt, Germany More articles by this author , Jasmina MakarevicJasmina Makarevic Frankfurt, Germany More articles by this author , Michael ReiterMichael Reiter Frankfurt, Germany More articles by this author , Martin KuroschMartin Kurosch Frankfurt, Germany More articles by this author , Georg BartschGeorg Bartsch Frankfurt, Germany More articles by this author , Christoph WiesnerChristoph Wiesner Frankfurt, Germany More articles by this author , Steffen WedelSteffen Wedel Frankfurt, Germany More articles by this author , Axel HaferkampAxel Haferkamp Frankfurt, Germany More articles by this author , and Roman BlahetaRoman Blaheta Frankfurt, Germany More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2012.02.872AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES mTOR targeting is a promising strategy for cancer therapy since the phosphatidyl-inositol-3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) pathway is aberrantly activated in different tumors. It has been argued that chronic drug exposure may trigger the development of resistance, consequently limiting the efficacy of mTOR-inhibitors. As no published studies previously dealt with this issue, a prostate cancer subline resistant to the mTOR–inhibitor RAD001 (everolimus) was established and the impact of drug resistance on the proliferative potential of the tumor cells and molecular characteristics of cell growth regulation were analyzed. METHODS The growth and proliferation properties of PC3 prostate cancer cells, sensible (PC3par) or resistant (PC3res) to RAD001, were investigated using MTT and BrdU tests as well as clonogenic assay. Cell cycle and western blot analysis of regulating proteins were performed. Knock-down models were established by transfection of cells with cdk1 or cyclin B siRNA. RESULTS Cell growth and proliferation rates of PC3res and PC3par were not significantly different. Removal of RAD001 from the culture medium of PC3res cells followed by low-dosed treatment with RAD001 resulted in no growth inhibiting effect. Similar basal apoptosis rate was observed in PC3par and PC3res cells. However, late apoptosis increased in PC3par but decreased in PC3res following treatment with low-dosed RAD001. Accordingly, the number of vital cells was reduced in PC3par but augmented in PC3res cells following RAD001 treatment. PC3res accumulated in the G2/M-phase, accompanied by a significant loss of PC3res in G0/G1, compared to PC3par cells. Particularly, cdk1 and cyclin B were strongly up-regulated in PC3res. Incubation of the prostate cancer cells with siRNA against cdk1 or cyclin B distinctly diminished the protein content in both PC3par and PC3res. The specific knockdown was accompanied by a significant growth blockade of PC3par and, most importantly, of the RAD001 resistant subline PC3res. Interestingly, incubation of PC3res cells with cyclin B siRNA restored the tumor cells′ sensitivity to RAD001. Cell growth attenuation was now induced in this cell line by treatment with the drug. CONCLUSIONS The results indicate for the first time that cdk1-cyclin B overexpression is related to resistance development in PC3 cells under chronic treatment with RAD001, leading to enhanced progression towards G2/M. Down-regulation of the cdk1-cyclin B complex may prolong the efficacy of a therapeutic regimen based on mTOR-inhibition in prostate cancer. © 2012 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 187Issue 4SApril 2012Page: e320-e321 Advertisement Copyright & Permissions© 2012 by American Urological Association Education and Research, Inc.MetricsAuthor Information Igor Tsaur Frankfurt, Germany More articles by this author Jasmina Makarevic Frankfurt, Germany More articles by this author Michael Reiter Frankfurt, Germany More articles by this author Martin Kurosch Frankfurt, Germany More articles by this author Georg Bartsch Frankfurt, Germany More articles by this author Christoph Wiesner Frankfurt, Germany More articles by this author Steffen Wedel Frankfurt, Germany More articles by this author Axel Haferkamp Frankfurt, Germany More articles by this author Roman Blaheta Frankfurt, Germany More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...