Poster Presentation Epigenetics 2013

Diffuse large B-cell lymphoma with combined TP53 mutation and MIR34A methylation: Another “double hit” lymphoma with very poor outcome? (#100)

Kirsten Grønbæk 1 , Fazila Asmar 1 , Christoffer Hother 1 , Gorjan Kulosman 1 , Marianne Treppendahl 1 , Helene M Nielsen 1 , Ulrik Ralfkiaer 1 , Michael B Møller 2 , Elisabeth Ralfkiaer 1 , Peter Brown 1
  1. Rigshospitalet, Copenhagen, DK, Denmark
  2. Odense University Hospital, Odense, Denmark

Disruption of miR34a, -b and -c has been implicated in lymphomagenesis, and in CLL it has been suggested that miR34a expression is a surrogate marker for TP53 disruption associated with a poor prognosis. P53 is a transcription factor for the miR34s, and overexpression of miR34s in p53 deficient cells can reinstate p53 functions.1,2 However, in cellular senescence miR34a may be activated independently of p53.3A recent multicenter study shows that in diffuse large B-cell lymphoma (DLBCL), TP53 disruption is still a negative prognostic factor for survival after the implementation of Rituximab.4 Information on the role of the miR34s in normal CD19+ B-cells (PBL-B), activated B-cells, and de novo diffuse large B-cell lymphoma (DLBCL) is limited.

Here, we show that only miR34a-5p is expressed in PBL-B, and significantly induced in activated B-cells (P=0.017) and reactive lymph nodes (P<0.001). No significant induction of the other miR34s is observed. In PBL-B, the MIR34A and MIR34B/C promoters are unmethylated, but the latter show enrichment for the H3K4me3/H3K27me3 silencing mark.
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One hundred and twenty two (81%) of 150 de novo DLBCLs carried one or more of the following alterations: TP53 mutations: 24 (16%), MIR34A methylation: 42 (28%), and MIR34B/C methylation: 116 (77%). Nine cases (6%) carried combined TP53 mutation and methylation of MIR34A. MIR34B/C methylation, and either mutation of TP53 or methylation of MIR34A (+/- MIR34B/C methylation) did not influence survival. However, the 9 patients with concomitant mutation of TP53 and MIR34A methylation had a median survival of only 9.4 months (P<0.0001), and multivariate analysis showed that TP53/MIR34A “double-hit” is an independent negative prognostic factor for survival (P=0.0002). Interestingly, none of the Rituximab treated patients with TP53 mutation only had died after >3 years. In 2 DLBCL-cell lines with concomitant TP53 mutation and methylation of MIR34A, miR34a-5p was upregulated by 5-aza-2’deoxycytidine. Thus we believe, we have identified a novel rare, aggressive, but treatable, “double-hit” DLBCL.