Epigenetic silencing of the interferon regulatory factor ICSBP/IRF8 in human multiple myeloma

Exp Hematol. 2008 Dec;36(12):1673-1681. doi: 10.1016/j.exphem.2008.08.001. Epub 2008 Oct 15.


Objective: Multiple myeloma (MM) is presently an incurable malignant plasma cell tumor. The objective of this study was to investigate expression of the interferon regulatory factor family (IRF1-9) and the potential role of DNA methylation in silencing IRF genes in MM cell lines and purified MM cells from patients.

Materials and methods: Using a panel of 13 human MM cell lines and purified CD138+ cells from nine MM patients, expression of IRF genes was investigated by quantitative reverse transcriptase polymerase chain reaction and Western blot. DNA methylation of the interferon consensus sequence-binding protein (ICSBP/IRF8) gene was measured using pyrosequencing, and the effect of promoter methylation on expression was analyzed by in vitro methylation of a cloned ICSBP/IRF8 promoter, and treatment of MM cells with 5-aza-2'-deoxycytidine (DAC).

Results: Eight of thirteen of the MM cell lines were found to lack ICSBP/IRF8 expression, associated with hypermethylation of the CpG island in the ICSBP/IRF8 promoter. We also found that ICSBP/IRF8 was significantly underexpressed in primary MM cells, whereas the ICSBP/IRF8 promoter was methylated in only one of nine of primary purified CD138+ MM samples. DAC-mediated demethylation restored endogenous ICSBP/IRF8 expression, whereas in vitro methylation silenced the promoter.

Conclusion: Expression of the ICSBP/IRF8 gene is silenced in a majority of MM cell lines and primary CD138+ MM cells. DNA methylation of the ICSBP/IRF8 gene is a frequent event in MM cell lines, but silencing is also observed in the absence of methylation. These results suggest that silencing of ICSBP/IRF8 expression, by DNA methylation or other epigenetic mechanisms, may be associated with the malignant phenotype of MM.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antimetabolites, Antineoplastic
  • Azacitidine / analogs & derivatives
  • Cell Line, Tumor
  • DNA Methylation* / drug effects
  • DNA Methylation* / genetics
  • Decitabine
  • Gene Expression Regulation, Neoplastic* / drug effects
  • Gene Expression Regulation, Neoplastic* / genetics
  • Gene Silencing* / drug effects
  • Humans
  • Interferon Regulatory Factors / biosynthesis*
  • Interferon Regulatory Factors / genetics
  • Multiple Myeloma / metabolism*
  • Neoplasm Proteins / biosynthesis*
  • Neoplasm Proteins / genetics
  • Promoter Regions, Genetic


  • Antimetabolites, Antineoplastic
  • Interferon Regulatory Factors
  • Neoplasm Proteins
  • interferon regulatory factor-8
  • Decitabine
  • Azacitidine