Escape mechanisms from antibody therapy to lymphoma cells: downregulation of CD20 mRNA by recruitment of the HDAC complex and not by DNA methylation

Biochem Biophys Res Commun. 2009 Dec 4;390(1):48-53. doi: 10.1016/j.bbrc.2009.09.059. Epub 2009 Sep 19.


Although rituximab is a critical monoclonal antibody therapy for CD20-positive B-cell lymphomas, rituximab resistance showing a CD20-negative phenotypic change has been a considerable clinical problem. Here we demonstrate that CD20 mRNA and protein expression is repressed by recruitment of a histone deacetylase protein complex to the MS4A1 (CD20) gene promoter in CD20-negative transformed cells after treatment with rituximab. CD20 mRNA and protein expression were stimulated by decitabine (5-Aza-dC) in CD20-negative transformed cells, and was enhanced by trichostation A (TSA). Immunoblotting indicated that DNMT1 expression was first downregulated 1 day after treatment with 5-Aza-dC, but IRF4 and Pu.1, the transcriptional regulators of MS4A1, were still expressed with or without 5-Aza-dC. Interestingly, CpG methylation of the MS4A1 promoter was not observed in CD20-negative transformed cells without 5-Aza-dC. A chromatin immunoprecipitation (ChIP) assay indicated that the Sin3A-HDAC1 co-repressor complex was recruited to the promoter and dissociated from the promoter with 5-Aza-dC and TSA, resulting in histone acetylation. Under these conditions, IRF4 and Pu.1 were continually recruited to the promoter with or without 5-Aza-dC and TSA. These results suggest that recruitment of the Sin3A-HDAC1 complex is related to downregulation of CD20 expression in CD20-negative B-cells after treatment with rituximab.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antibodies, Monoclonal / therapeutic use*
  • Antibodies, Monoclonal, Murine-Derived
  • Antigens, CD20 / genetics*
  • Azacitidine / analogs & derivatives
  • Azacitidine / pharmacology
  • Cell Line, Tumor
  • Cytidine Triphosphate / analogs & derivatives
  • Cytidine Triphosphate / pharmacology
  • DNA Methylation
  • Down-Regulation
  • Drug Resistance, Neoplasm / genetics*
  • Epigenesis, Genetic
  • Gene Expression Regulation, Leukemic*
  • Histone Deacetylase 1 / metabolism*
  • Humans
  • Lymphoma, B-Cell / therapy*
  • Promoter Regions, Genetic
  • Repressor Proteins / metabolism
  • Rituximab


  • Antibodies, Monoclonal
  • Antibodies, Monoclonal, Murine-Derived
  • Antigens, CD20
  • Repressor Proteins
  • SIN3A transcription factor
  • Rituximab
  • Cytidine Triphosphate
  • 5-aza-2'-deoxycytidine-5'-triphosphate
  • HDAC1 protein, human
  • Histone Deacetylase 1
  • Azacitidine