Fig. 2

EZH2 mutations result in decreased EZH2 protein expression. a Representative examples of EZH2 immunolabeling of control and four patient BM biopsies. Immunolabeling of normal BM biopsies shows on average a moderate nuclear expression level score of 2 in hematopoietic cells (samples 1, 2) while a reactive nodular lymphoid infiltrate in (1) is completely negative. BM samples of two EZH2-wt patients show strong (sample 3, IHC score 3) or moderate (sample 4, score 2) EZH2 expression. In contrast, EZH2 staining intensity is negative (sample 5, score 0) or weakly positive (sample 6, score 1) in BM biopsies of two EZH2-mut patients. Samples 3 and 5 are derived from patients with intact chromosome 7, samples 4 and 6 from patients with del(7q)/-7. b Median and range of EZH2 protein expression by IHC depending on EZH2 mutation and chromosome 7 status. EZH2 expression is lower (p = 0.0002 by two-way ANOVA) in patients with an EZH2 mutation compared to patients with wild-type EZH2. The reduction is similar in patients with and without chromosome 7q losses or deletions, but patients with del(7q)/-7 tended to have lower EZH2 expression levels than patients with intact chromosome 7 (p = 0.07)