title: Genomic screening for genes silenced by DNA methylation revealed an association between RASD1 inactivation and dexamethasone resistance in multiple myeloma.
abstract: OBJECTIVE
  Epigenetic changes such as DNA methylation play a key role in the development and progression of multiple myeloma. Our aim in the present study was to use genomic screening to identify genes targeted for epigenetic inactivation in multiple myeloma and assess their role in the development of resistance to dexamethasone.
  
  
  METHODS
  Gene expression was examined using microarray screening, reverse transcription-PCR, and real-time quantitative PCR. DNA methylation was examined using bisulfite PCR, bisulfite sequencing, and bisulfite pyrosequencing in 14 multiple myeloma cell lines, 87 multiple myeloma specimens, and 12 control bone marrow samples. WST-8 assays were used to assess cell viability after treatment with 5-aza-2'-deoxycytidine and/or dexamethasone.
  
  
  RESULTS
  Microarray analysis was done to screen for genes up-regulated by 5-aza-2'-deoxycytidine. In RPMI8226 cells, 128 genes were up-regulated, whereas 83 genes were up-regulated in KMS12PE cells. Methylation of 22 genes with CpG islands in their 5' regions, including RASD1, was confirmed. Methylation of RASD1 was associated with its inactivation, which correlated with resistance to dexamethasone. Treating multiple myeloma cells with 5-aza-2'-deoxycytidine restored sensitivity to dexamethasone. Methylation of RASD1 was also detected in a subset of primary multiple myeloma specimens, and the levels of methylation were increased after repeated antitumor treatments. Gene signature analysis revealed various genes to be synergistically induced by treatment with a combination of 5-aza-2'-deoxycytidine plus dexamethasone.
  
  
  CONCLUSIONS
  Our findings indicate that epigenetic inactivation of genes, including RASD1, plays a key role in the development of dexamethasone resistance in multiple myeloma. Moreover, they show the utility of demethylation therapy in cases of advanced multiple myeloma.
authors: Departments of Public Health, SapporoMedicalUniversity, Japan.
authors: Masanori
authors: M
authors: Nojima
authors: Reo
authors: R
authors: Maruyama
authors: Hiroshi
authors: H
authors: Yasui
authors: Hiromu
authors: H
authors: Suzuki
authors: Yumiko
authors: Y
authors: Maruyama
authors: Isao
authors: I
authors: Tarasawa
authors: Yasushi
authors: Y
authors: Sasaki
authors: Hideki
authors: H
authors: Asaoku
authors: Hajime
authors: H
authors: Sakai
authors: Toshiaki
authors: T
authors: Hayashi
authors: Mitsuru
authors: M
authors: Mori
authors: Kohzoh
authors: K
authors: Imai
authors: Takashi
authors: T
authors: Tokino
authors: Tadao
authors: T
authors: Ishida
authors: Minoru
authors: M
authors: Toyota
authors: Yasuhisa
authors: Y
authors: Shinomura
mesh_terms: D000970:Antineoplastic Agents / Q000627:therapeutic use; D001374:Azacitidine / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000494:pharmacology; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects / Q000235:genetics; D019175:DNA Methylation / Q000502:physiology*; D000077209:Decitabine; D003907:Dexamethasone / Q000627:therapeutic use*; D004353:Drug Evaluation, Preclinical; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D004357:Drug Synergism; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic; D020868:Gene Silencing / Q000502:physiology; D005820:Genetic Testing; D006801:Humans; D008954:Models, Biological; D009101:Multiple Myeloma / Q000188:drug therapy* / Q000235:genetics*; D020411:Oligonucleotide Array Sequence Analysis; D018631:ras Proteins / Q000235:genetics* / Q000502:physiology
chemical_list: D000970:Antineoplastic Agents; C400132:RASD1 protein, human; D000077209:Decitabine; D003907:Dexamethasone; D018631:ras Proteins; D001374:Azacitidine