MP45-20 PDK4 – A POSSIBLE THERAPEUTIC TARGET FOR HIGH GRADE BLADDER CANCER

Abstract

You have accessJournal of UrologyBladder Cancer: Basic Research II1 Apr 2015MP45-20 PDK4 – A POSSIBLE THERAPEUTIC TARGET FOR HIGH GRADE BLADDER CANCER Andrew Mikhalyuk, Dharamainder Choudhary, Carol Pilbeam, and John Taylor Andrew MikhalyukAndrew Mikhalyuk More articles by this author , Dharamainder ChoudharyDharamainder Choudhary More articles by this author , Carol PilbeamCarol Pilbeam More articles by this author , and John TaylorJohn Taylor More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2015.02.1518AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES The activity of pyruvate dehydrogenase complex (PDC) is regulated by phosphorylation and dephophorylation via pyruvate dehydrogenase kinase (PDK) and pyruvate dehydrogenase phosphatase (PDP), respectively. Inactivation of PDC by PDK promotes the flux of pyruvate into lactate formation. Some cancer cells overexpress PDK and this shift in metabolism may help sustain cell growth in the acidic and hypoxic tumor microenvironment. In a laser capture microdissection-coupled microarray gene expression analysis of low grade bladder cancer (LGBC) vs high grade muscle invasive (MIBC) samples, we found a 33-fold (p<0.05) higher PDK4 expression in MIBCs. The goal of this study was to explore the role of PDK4 in bladder cancer cell lines to ascertain its potential as a novel therapeutic target. METHODS Bladder cancer cell lines (HTB4, HTB5, HTB9, HT1376) were cultured in defined media as specified by ATCC. Total RNA was extracted and quantitative PCR was performed. Cell numbers were counted using an automated cell counter. Cell cycle and apoptosis analyses were performed by fluorescence-activated cell sorting. Transient transfections with PDK4 gene specific siRNAs were performed. RESULTS PDK4 expression was elevated in all bladder cancer cell lines (20-100 fold; p<0.02-0.003) as compared to benign UROtsa cells. On the other hand, lower overexpression of both PDP1 and PDP2 was observed in all the cancer cell lines (0.3- 2.2 fold; not significant). To determine the functional significance of PDK4 expression, we treated cells with dichloroacetate (DCA), a PDK inhibitor, for 0-72 h. A significant decrease in cell number was detected in a dose dependent manner (10-50 mM). HTB2, a low grade cell line, showed a significant decrease in cell number (70%) when incubated with 50 mM DCA for 72 h (p< 0.001). The high grade cell line, HTB5, showed a higher decrease (92%) with the same treatment (p< 0.001). These results suggest that bladder cancer cells are utilizing an aerobic glycolytic pathway, also known as The Warburg effect. Our preliminary data on cell cycle analysis with 50 mM DCA treatment at 72 h showed an increased number of cells arrested at the G1 phase (from 53% to 72%) and a decrease in number in S-phase (from 39% to 20%). In addition, preliminary data suggested that inhibiting PDK4 expression with siRNA resulted in growth inhibition. CONCLUSIONS These findings suggest a novel role of PDK4 in bladder cancer and provide the first evidence that inhibiting PDK activity may be a viable antitumor therapy in MIBC. © 2015 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 193Issue 4SApril 2015Page: e543 Advertisement Copyright & Permissions© 2015 by American Urological Association Education and Research, Inc.MetricsAuthor Information Andrew Mikhalyuk More articles by this author Dharamainder Choudhary More articles by this author Carol Pilbeam More articles by this author John Taylor More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...