775 THE MTOR PATHWAY IMPACTS PROLIFERATION AND CHEMOSENSITIVITY OF UROTHELIAL CARCINOMA CELLS IN VITRO AND IS HIGHLY EXPRESSED IN A SUBSET OF HUMAN BLADDER CANCERS

Abstract

You have accessJournal of UrologyBladder Cancer: Basic Research I1 Apr 2010775 THE MTOR PATHWAY IMPACTS PROLIFERATION AND CHEMOSENSITIVITY OF UROTHELIAL CARCINOMA CELLS IN VITRO AND IS HIGHLY EXPRESSED IN A SUBSET OF HUMAN BLADDER CANCERS Stephen Boorjian, Jiaru Zhang, Igor Makhlin, Christopher Long, Karthik Devarajan, Yan Zhou, Min Huang, and Jonathan Chernoff Stephen BoorjianStephen Boorjian Rockledge, PA More articles by this author , Jiaru ZhangJiaru Zhang Philadelphia, PA More articles by this author , Igor MakhlinIgor Makhlin Philadelphia, PA More articles by this author , Christopher LongChristopher Long Philadelphia, PA More articles by this author , Karthik DevarajanKarthik Devarajan Philadelphia, PA More articles by this author , Yan ZhouYan Zhou Philadelphia, PA More articles by this author , Min HuangMin Huang Philadelphia, PA More articles by this author , and Jonathan ChernoffJonathan Chernoff Philadelphia, PA More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2010.02.1424AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Although phosphatidylinositol 3-kinase/AKT signaling has been found to be active in urothelial carcinoma (UC), the importance of the mammalian target of rapamycin (mTOR), a downstream target of this pathway, remains to be established. Here, then, we investigated the relevance of mTOR in human bladder cancer cell lines and patient tissue specimens. METHODS The human bladder cancer cell lines UMUC-3, 253J, TCC-SUP, T24, and 1365 were evaluated for expression of mTOR and phospho-mTOR using Western blot analysis. Cells were treated with different concentrations of the mTOR inhibitor rapamycin, and viability was assessed using the Cell Titer Blue assay. Propidium idodide staining and fluorescence-activated cell sorting were used to determine the impact of treatment on the cell cycle. Apoptosis was studied by measurement of PARP cleavage. The effect of mTOR inhibition on chemosensitivity was investigated by treating cells with rapamycin (5nM), alone or together with cisplatin (5μM). In addition, expression of phospho-mTOR in human bladder tissue was assessed using a tissue microarray (TMA) constructed from 328 UC patient tissue specimens. RESULTS High levels of baseline expression of mTOR and phospho-mTOR were noted in all 5 cell lines. Treatment with rapamycin significantly decreased cell viability at 48 and 72 hours in UMUC-3 (p=0.004) and 253J (p<0.001) cells at all doses tested. Cell cycle analysis showed that rapamycin induced arrest in the G0-G1 phase in these cells. Consistent with its known mechanism of action, rapamycin decreased protein expression of phospho-mTOR and its downstream effector, p-S6K, in both cell lines. Moreover, treatment with rapamycin increased the ability of cisplatin to inhibit cell viability in UMUC-3 (p=0.002) and 253J (p=0.03) cells. No evidence for increased PARP cleavage was noted after treatment with rapamycin, alone or in combination with cisplatin. Interestingly, despite high expression in all bladder cancer cell lines tested, phospho-mTOR expression in patient UC specimens was increased compared to non-tumor bladder tissue in only 65/203 (32.0%) tumors on the TMA analysis. CONCLUSIONS Blockade of the mTOR signaling pathway inhibits bladder cancer cell proliferation and enhances the effectiveness of cisplatin in vitro, likely through cell-cycle arrest rather than direct cytotoxicity. Suppression of the mTOR pathway thus has the potential to be a therapeutic target in bladder cancer for select patients and merits further investigation. © 2010 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 183Issue 4SApril 2010Page: e303 Advertisement Copyright & Permissions© 2010 by American Urological Association Education and Research, Inc.MetricsAuthor Information Stephen Boorjian Rockledge, PA More articles by this author Jiaru Zhang Philadelphia, PA More articles by this author Igor Makhlin Philadelphia, PA More articles by this author Christopher Long Philadelphia, PA More articles by this author Karthik Devarajan Philadelphia, PA More articles by this author Yan Zhou Philadelphia, PA More articles by this author Min Huang Philadelphia, PA More articles by this author Jonathan Chernoff Philadelphia, PA More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...