GATA2 May Contribute with EVI1 to the Leukemogenic Mechanism in Patients with 3q21q26 Rearrangements.

Abstract

Patients with 3q21q26 rearrangements seem to share similar clinicopathologic features and a common molecular mechanism, leading to MDS or AML. The overexpression of EVI1 (3q26) has been implicated in the dysplasia that characterizes this subset of myeloid neoplasias with poor prognosis. However, EVI1 overexpression had been detected in 9% of AML cases without 3q26 abnormalities; and several 3q21q26 cases with no EVI1 overexpression had been reported. Our aim was to characterize different subgroups in 3q rearrangements, and to define the gene expression profile of these groups, specially in the group with 3q21q26 rearrangements. We analyzed 44 samples (6 cell lines and 38 samples of patients) with 3q rearrangements at G-band level, 36 had AML and 8 MDS. As a control, we analyzed 6 samples of patients with 3q rearrangements and lymphoid neoplasias, a cDNA panel of normal human tissues (Clontech), and 10 normal bone marrow samples. FISH analysis was performed using six BACs: PR11-390G14, RP11-475N22 (GATA2), RP11-689D3 (RPN1) on 3q21; RP11-82C9 (EVI1), RP11-115B16 (MDS1) and RP11-196F13 (TRAIL) on 3q26; and a centromere probe. Expression of GATA2, MDS1-EVI1, and EVI1 was measured by a quantitative real-time RT-PCR (Taqman) assay (Applied Biosystems). Samples were first classified attending at the G-banding. FISH analysis showed the heterogeneity of breakpoints in these cases, and the samples were grouped as 3q21 (5 cases), 3q26 (11 cases), 3q21q26 (16 cases) and other 3q rearrangements (12 cases). Real time RT-PCR showed overexpression (OE) of EVI1 and/or GATA2 in 75% of all the cases (33/44), suggesting the important role of these genes in patients with 3q rearrangements and myeloid neoplasias. In patients with lymphoid neoplasias and 3q rearrangements no genes were found to be OE. A different expression profile was found in the groups analyzed (Table 1). In the 3q21 group, 40% of the patients had GATA2 OE, but no EVI1 or MDS1-EVI1 OE was found. Our data show that EVI1 OE could be specific of the groups 3q26 (64%) and 3q21q26 (69%). The number of cases with EVI1 OE was significantly higher in patients with 3q rearrangements than in those with complex karyotype (data not show). In the group with 3q21q26, EVI1 and/or GATA2 were overexpressed in 87.5% of the cases (14/16). In conclusion, we have detected a different expression profile of the genes analyzed among samples with different 3q rearrangements. Our results suggest a more complex mechanism in patients with 3q21q26 rearrangements, in which GATA2 overexpression may contribute with EVI1 to the leukemogenic progress. Further molecular studies are in progress to analyze the different EVI1 transcripts.Table 1:Incidence of the overexpression of EVI1, GATA2 and MDS1-EVI1 in 32 patients with 3q21 and/or 3q26 rearrangements.Frequency & PercentageEVI1GATA2MDS1-EVI13q210% (0/5)40% (2/5)0% (0/5)3q2664% (7/11)73% (8/11)36% (4/11)3q21q2675% (12/16)69% (11/16)13% (2/16)