title: Restoration of epigenetically silenced SULF1 expression by 5-aza-2-deoxycytidine sensitizes hepatocellular carcinoma cells to chemotherapy-induced apoptosis.
abstract: BACKGROUND
  Hepatocellular carcinoma (HCC) is the second most frequent cause of cancer death worldwide. Sulfatase 1 (SULF1) functions as a tumor suppressor in HCC cell linesin vitro, but also has an oncogenic effect in some HCCsin vivo.
  
  
  OBJECTIVE
  To examine the mechanisms regulating SULF1 and its function in HCC.
  
  
  METHODS
  First, SULF1 mRNA and protein expression were examined. Second, we examined SULF1 gene copy number in HCC cells. Third, we assessed whether DNA methylation or methylation and/or acetylation of histone marks on the promoter regulate SULF1 expression. Finally, we examined the effect of 5-Aza-dC on sulfatase activity and drug-induced apoptosis.
  
  
  RESULTS
  SULF1 mRNA was down-regulated in 9/11 HCC cell lines but only 6/10 primary tumors. SULF1 mRNA correlated with protein expression. Gene copy number assessment by fluorescencein situhybridization showed intact SULF1 alleles in low SULF1 expressing cell lines. CpG island methylation in the SULF1 promoter and two downstream CpG islands did not show an inverse correlation between DNA methylation and SULF1 expression. However, chromatin immunoprecipitation showed that the SULF1 promoter acquires a silenced chromatin state in low SULF1-expressing cells through an increase in di/trimethyl-K9H3 and trimethyl-K27H3 and a concomitant loss of activating acetyl K9, K14H3 marks. 5-Aza-dC restored SULF1 mRNA expression in SULF1-negative cell lines, with an associated increase in sulfatase activity and sensitization of HCC cells to cisplatin-induced apoptosis.
  
  
  CONCLUSIONS
  SULF1 gene silencing in HCC occurs through histone modifications on theSULF1promoter. Restoration of SULF1 mRNA expression by 5-Aza-dC sensitized HCC cells to drug-induced apoptosis.
authors.affiliation: Division of Gastroenterology and Hepatology, College of Medicine, Mayo Clinic and Mayo Clinic Cancer Center, Rochester, MN, 55905 USA.
authors.forename: Abdirashid
authors.initials: A
authors.lastname: Shire
authors.affiliation: Division of Gastroenterology and Hepatology, College of Medicine, Mayo Clinic and Mayo Clinic Cancer Center, Rochester, MN, 55905 USA.
authors.forename: Gwen
authors.initials: G
authors.lastname: Lomberk
authors.affiliation: Division of Gastroenterology and Hepatology, College of Medicine, Mayo Clinic and Mayo Clinic Cancer Center, Rochester, MN, 55905 USA.
authors.forename: Jin-Ping
authors.initials: JP
authors.lastname: Lai
authors.affiliation: Division of Experimental Pathology and Laboratory Medicine, Mayo Clinic, Rochester, MN 55905 USA.
authors.forename: Hongzhi
authors.initials: H
authors.lastname: Zou
authors.affiliation: Department of Urology, Akita University School of Medicine, Akita 010-8543 Japan.
authors.forename: Norihiko
authors.initials: N
authors.lastname: Tsuchiya
authors.affiliation: Division of Gastroenterology and Hepatology, College of Medicine, Mayo Clinic and Mayo Clinic Cancer Center, Rochester, MN, 55905 USA.
authors.forename: Ileana
authors.initials: I
authors.lastname: Aderca
authors.affiliation: Division of Gastroenterology and Hepatology, College of Medicine, Mayo Clinic and Mayo Clinic Cancer Center, Rochester, MN, 55905 USA.
authors.forename: Catherine D
authors.initials: CD
authors.lastname: Moser
authors.affiliation: Division of Gastroenterology and Hepatology, College of Medicine, Mayo Clinic and Mayo Clinic Cancer Center, Rochester, MN, 55905 USA.
authors.forename: Kadra H
authors.initials: KH
authors.lastname: Gulaid
authors.affiliation: Division of Gastroenterology and Hepatology, College of Medicine, Mayo Clinic and Mayo Clinic Cancer Center, Rochester, MN, 55905 USA.
authors.forename: Abdul
authors.initials: A
authors.lastname: Oseini
authors.affiliation: Division of Gastroenterology and Hepatology, College of Medicine, Mayo Clinic and Mayo Clinic Cancer Center, Rochester, MN, 55905 USA.
authors.forename: Chunling
authors.initials: C
authors.lastname: Hu
authors.affiliation: Division of Gastroenterology and Hepatology, College of Medicine, Mayo Clinic and Mayo Clinic Cancer Center, Rochester, MN, 55905 USA.
authors.forename: Omar
authors.initials: O
authors.lastname: Warsame
authors.affiliation: Division of Laboratory Genetics, Department of Laboratory Medicine and Pathology College of Medicine, Mayo Clinic, Rochester, MN 55905 USA.
authors.forename: Robert B
authors.initials: RB
authors.lastname: Jenkins
authors.affiliation: Division of Gastroenterology and Hepatology, College of Medicine, Mayo Clinic and Mayo Clinic Cancer Center, Rochester, MN, 55905 USA.
authors.forename: Lewis R
authors.initials: LR
authors.lastname: Roberts
keywords: HCC; SULF1; epigenetic; genetic