title: Histone deacetylase 8 is deregulated in urothelial cancer but not a target for efficient treatment.
abstract: BACKGROUND
  Previous studies have shown that class-I histone deacetylase (HDAC) 8 mRNA is upregulated in urothelial cancer tissues and urothelial cancer cell lines compared to benign controls. Using urothelial cancer cell lines we evaluated whether specific targeting of HDAC8 might be a therapeutic option in bladder cancer treatment.
  
  
  METHODS
  We conducted siRNA-mediated knockdown and specific pharmacological inhibition of HDAC8 with the three different inhibitors compound 2, compound 5, and compound 6 in several urothelial carcinoma cell lines with distinct HDAC8 expression profiles. Levels of HDAC and marker proteins were determined by western blot analysis and mRNA levels were measured by quantitative real-time PCR. Cellular effects of HDAC8 suppression were analyzed by ATP assay, flow cytometry, colony forming assay and migration assay.
  
  
  RESULTS
  Efficient siRNA-mediated knockdown of HDAC8 reduced proliferation up to 45%. The HDAC8 specific inhibitors compound 5 and compound 6 significantly reduced viability of all urothelial cancer cell lines (IC₅₀ 9 - 21 μM). Flow cytometry revealed only a slight increase in the sub-G1 fraction indicating a limited induction of apoptosis. Expression of thymidylate synthase was partly reduced; PARP-cleavage was not detected. The influence of the pharmacological inhibition on clonogenic growth and migration show a cell line- and inhibitor-dependent reduction with the strongest effects after treatment with compound 5 and compound 6.
  
  
  CONCLUSIONS
  Deregulation of HDAC8 is frequent in urothelial cancer, but neither specific pharmacological inhibition nor siRNA-mediated knockdown of HDAC8 impaired viability of urothelial cancer cell lines in a therapeutic useful manner. Accordingly, HDAC8 on its own is not a promising drug target in bladder cancer.
authors.forename: Maria
authors.initials: M
authors.lastname: Lehmann
authors.forename: Michèle J
authors.initials: MJ
authors.lastname: Hoffmann
authors.forename: Annemarie
authors.initials: A
authors.lastname: Koch
authors.forename: Scott M
authors.initials: SM
authors.lastname: Ulrich
authors.forename: Wolfgang A
authors.initials: WA
authors.lastname: Schulz
authors.forename: Günter
authors.initials: G
authors.lastname: Niegisch
mesh_terms: D045744:Cell Line, Tumor; D055785:Gene Knockdown Techniques; D056572:Histone Deacetylase Inhibitors / Q000494:pharmacology; D006655:Histone Deacetylases / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology; D058990:Molecular Targeted Therapy; D034741:RNA, Small Interfering / Q000008:administration & dosage / Q000235:genetics; D012097:Repressor Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics* / Q000378:metabolism; D001749:Urinary Bladder Neoplasms / Q000188:drug therapy / Q000201:enzymology* / Q000235:genetics / Q000628:therapy*
chemical_list: D056572:Histone Deacetylase Inhibitors; D006877:Hydroxamic Acids; D034741:RNA, Small Interfering; D012097:Repressor Proteins; C409470:HDAC8 protein, human; D006655:Histone Deacetylases