Lenalidomide modulates gene expression in human ABC-DLBCL cells by regulating IKAROS interaction with an intronic control region of SPIB

Exp Hematol. 2017 Dec:56:46-57.e1. doi: 10.1016/j.exphem.2017.09.002. Epub 2017 Sep 8.

Abstract

Activated B-cell diffuse large B-cell lymphoma (ABC-DLBCL) is associated with a poor prognosis compared with other DLBCL types and therefore represents a top priority for developing novel therapies. Lenalidomide, an immunomodulatory drug in trials for treatment of ABC-DLBCL, targets the transcription factor IKAROS for degradation by the cereblon E3 ubiquitin ligase complex. In this study, we investigated whether the gene encoding the transcription factor SPI-B is a target of IKAROS. Using cultured ABC-DLBCL cell lines, we found that high levels of SPI-B expression conferred resistance to lenalidomide. Lenalidomide treatment of ABC-DLBCL cells resulted in downregulation of SPIB at the level of transcription. SPIB was regulated directly by IKAROS through a binding site located in the first intron of the gene. Inhibition of IKAROS binding using CRISPR/Cas9-mediated transcriptional repression downregulated endogenous SPIB transcription. Finally, ectopic expression of IKAROS protected SPIB from downregulation. These results show that the mechanism of action of lenalidomide in ABC-DLBCL cells involves downregulation of SPIB transcription by cereblon-induced degradation of IKAROS. These results have implications for the design of synthetic lethal therapy for the treatment of ABC-DLBCL.

MeSH terms

  • Adaptor Proteins, Signal Transducing
  • Animals
  • Cell Line, Tumor
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism*
  • Down-Regulation / drug effects
  • Gene Expression Regulation, Neoplastic / drug effects*
  • Humans
  • Ikaros Transcription Factor / genetics
  • Ikaros Transcription Factor / metabolism*
  • Lenalidomide
  • Lymphoma, Large B-Cell, Diffuse / drug therapy
  • Lymphoma, Large B-Cell, Diffuse / genetics
  • Lymphoma, Large B-Cell, Diffuse / metabolism*
  • Mice
  • NIH 3T3 Cells
  • Neoplasm Proteins / genetics
  • Neoplasm Proteins / metabolism*
  • Peptide Hydrolases / genetics
  • Peptide Hydrolases / metabolism
  • Proteolysis / drug effects*
  • Thalidomide / analogs & derivatives*
  • Thalidomide / pharmacology
  • Transcription Factors / genetics
  • Transcription Factors / metabolism*
  • Ubiquitin-Protein Ligases

Substances

  • Adaptor Proteins, Signal Transducing
  • CRBN protein, human
  • DNA-Binding Proteins
  • Neoplasm Proteins
  • Transcription Factors
  • SPIB protein, human
  • Ikaros Transcription Factor
  • Thalidomide
  • Ubiquitin-Protein Ligases
  • Peptide Hydrolases
  • Lenalidomide