Epigenetic down-regulation of the tumor suppressor gene PRDM1/Blimp-1 in diffuse large B cell lymphomas: A potential role of the microRNA let-7 Academic Article uri icon


MeSH Major

  • Down-Regulation
  • Epigenesis, Genetic
  • Lymphoma, Large B-Cell, Diffuse
  • MicroRNAs
  • Repressor Proteins


  • PRDM1/Blimp-1, a master regulator for B cell terminal differentiation, is a putative tumor suppressor in diffuse large B cell lymphomas (DLBCL). Inactivating mutations of PRDM1 have been previously identified in a subset of nongerminal center B cell-like (GCB) DLBCL. We investigated the presence of alternative mechanisms of down-regulating PRDM1 in a cohort of 25 primary DLBCL and six DLBCL cell lines. While some DLBCL, predominantly the GCB-type, showed low levels of both PRDM1alpha mRNA and protein, presumably as a result of direct transcription repression, discordant expressions between the two were identified in a subset of DLBCL without PRDM1 mutations, the primarily non-GCB type, consistent with translational down-regulation. This subset of DLBCL exhibits relatively high PRDM1alpha mRNA levels but low levels of PRDM1. Data obtained from expression analysis, luciferase reporter assays, and transfection experiments support a role of targeting of PRDM1 by microRNA let-7 family in mediating this down-regulation. Let-7, in particular let-7b, is overexpressed in DLBCL relative to normal GCB cells, suggesting that it is deregulated. Thus, abnormal epigenetic down-regulation of PRDM1 by let-7 and other microRNAs may represent an alternative mechanism of reducing normal PRDM1 function in a subset of DLBCL with relatively high PRDM1alpha mRNA expression and unmutated PRDM1. These findings provide further evidence for an important role of impairment of terminal B cell differentiation in DLBCL pathogenesis.

publication date

  • September 2010



  • Academic Article



  • eng

PubMed Central ID

  • PMC2928978

Digital Object Identifier (DOI)

  • 10.2353/ajpath.2010.091291

PubMed ID

  • 20651244

Additional Document Info

start page

  • 1470

end page

  • 9


  • 177


  • 3