EVI1 is an aggressive nuclear oncoprotein deregulated by recurring chromosomal abnormalities in myelodysplastic syndrome (MDS). The expression of the corresponding gene is a very poor prognostic marker for MDS patients and is associated with severe defects of the erythroid lineage. We have recently shown that the constitutive expression of EVI1 in murine bone marrow results in a fatal disease with features characteristic of MDS, including anemia, dyserythropoiesis, and dysmegakaryopoiesis. These lineages are regulated by the DNA-binding transcription factor GATA1. EVI1 has two zinc finger domains containing seven motifs at the N terminus and three motifs at the C terminus. Supported by results of assays utilizing synthetic DNA promoters, it was earlier proposed that erythroid-lineage repression by EVI1 is based on the ability of this protein to compete with GATA1 for DNA-binding sites, resulting in repression of gene activation by GATA1. Here, however, we show that EVI1 is unable to bind to classic GATA1 sites. To understand the mechanism utilized by EVI1 to repress erythropoiesis, we used a combination of biochemical assays, mutation analyses, and in vitro bone marrow differentiation. The results indicate that EVI1 interacts directly with the GATA1 protein rather than the DNA sequence. We further show that this protein-protein interaction blocks efficient recognition or binding to DNA by GATA1. Point mutations that disrupt the geometry of two zinc fingers of EVI1 abolish the protein-protein interaction, leading to normal erythroid differentiation of normal murine bone marrow in vitro.
SummaryThe randomized, double‐blind, double‐dummy, phase 3b RELIEF trial evaluated polycythaemia vera (PV)‐related symptoms in patients who were well controlled with a stable dose of hydroxycarbamide (also termed hydroxyurea) but reported PV‐related symptoms. Patients were randomized 1:1 to ruxolitinib 10 mg BID (n = 54) or hydroxycarbamide (prerandomization dose/schedule; n = 56); crossover to ruxolitinib was permitted after Week 16. The primary endpoint, ≥50% improvement from baseline in myeloproliferative neoplasm ‐symptom assessment form total symptom score cytokine symptom cluster (TSS‐C; sum of tiredness, itching, muscle aches, night sweats, and sweats while awake) at Week 16, was achieved by 43·4% vs. 29·6% of ruxolitinib‐ and hydroxycarbamide‐treated patients, respectively (odds ratio, 1·82; 95% confidence interval, 0·82–4·04; P = 0·139). The primary endpoint was achieved by 34% of a subgroup who maintained their hydroxycarbamide dose from baseline to Weeks 13–16. In a post hoc analysis, the primary endpoint was achieved by more patients with stable screening‐to‐baseline TSS‐C scores (ratio ≤ 2) receiving ruxolitinib than hydroxycarbamide (47·4% vs. 25·0%; P = 0·0346). Ruxolitinib treatment after unblinding was associated with continued symptom score improvements. Adverse events were primarily grades 1/2 with no unexpected safety signals. Ruxolitinib was associated with a nonsignificant trend towards improved PV‐related symptoms versus hydroxycarbamide, although an unexpectedly large proportion of patients who maintained their hydroxycarbamide dose reported symptom improvement.
We conclude that CD4+ cell count at day +30 is a predictive factor for EBV DNAemia and may help identify patients requiring closer monitoring. Although only 3% of patients progressed to PTLD and were all successfully managed, EBV reactivation was associated with higher TRM, mainly because of infections.
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