Escape mechanisms from antibody therapy to lymphoma cells: downregulation of CD20 mRNA by recruitment of the HDAC complex and not by DNA methylation.
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.
Sugimoto
Takumi
T
Department of Hematology and Oncology, Nagoya University Graduate School of Medicine, Nagoya, Japan.
Tomita
Akihiro
A
Hiraga
Junji
J
Shimada
Kazuyuki
K
Kiyoi
Hitoshi
H
Kinoshita
Tomohiro
T
Naoe
Tomoki
T
D000911:Antibodies, Monoclonal / Q000627:therapeutic use*; D058846:Antibodies, Monoclonal, Murine-Derived; D018951:Antigens, CD20 / Q000235:genetics*; D001374:Azacitidine / Q000031:analogs & derivatives / Q000494:pharmacology; D045744:Cell Line, Tumor; D003570:Cytidine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D019175:DNA Methylation; D015536:Down-Regulation; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D044127:Epigenesis, Genetic; D015973:Gene Expression Regulation, Leukemic; D056284:Histone Deacetylase 1 / Q000378:metabolism*; D006801:Humans; D016393:Lymphoma, B-Cell / Q000628:therapy*; D011401:Promoter Regions, Genetic; D012097:Repressor Proteins / Q000378:metabolism; D000069283:Rituximab; D056264:Sin3 Histone Deacetylase and Corepressor Complex
D000911:Antibodies, Monoclonal; D058846:Antibodies, Monoclonal, Murine-Derived; D018951:Antigens, CD20; D012097:Repressor Proteins; C099683:SIN3A transcription factor; D000069283:Rituximab; D003570:Cytidine Triphosphate; C038673:5-aza-2'-deoxycytidine-5'-triphosphate; C110550:HDAC1 protein, human; D056284:Histone Deacetylase 1; D056264:Sin3 Histone Deacetylase and Corepressor Complex; D001374:Azacitidine