We also found mutations in genes seldom reported in inherited BMF (IBMF), such as <i>SAMD9</i> and <i>SAMD9L</i> (N = 16 of the 86 patients, 18.6%), <i>MECOM/EVI1</i> (N = 6, 7.0%), and <i>ERCC6L2</i> (N = 7, 8.1%), each of which was associated with a distinct natural history; <i>SAMD9</i> and <i>SAMD9L</i> patients often experienced transient aplasia and monosomy 7, whereas <i>MECOM</i> patients presented early-onset severe aplastic anemia, and <i>ERCC6L2</i> patients, mild pancytopenia with myelodysplasia.
Both low/high risk MDS may benefit significantly from therapy with ATO/thalidomide, and those with high pre-therapy EVI1 expression may be uniquely sensitive.
3q26.2/EVI1 rearrangements resulting in EVI1 overexpression play an important role in leukemogenesis and are associated with treatment resistance and a poorer prognosis in patients with acute myeloid leukemia, myelodysplastic syndrome, chronic myeloid leukemia and BCR-ABL negative myeloproliferative neoplasms.
Abnormal expression of the Evi-1 gene and overexpression of MDS1-Evi-1 gene may play a role in the pathogenesis or progression of MDS and post-MDS AML.
Our results suggest that the leukemogenic role of EVI1 expression may differ between post-MDS AML and leukemia, with EVI1 expression associated with a 3q26 abnormality.
We previously reported a recurrent t(3;8)(q26;q24) translocation involving EVI1 in five patients with myelodysplastic syndrome or acute myeloid leukemia.
In a mouse bone marrow transplantation model, a RUNX1 mutant, D171N, was shown to collaborate with Evi1 in the development of MDSs; however, this is rare in humans.
We further found that ATO targets AME via both myelodysplastic syndrome 1 (MDS1) and EVI1 moieties and degrades EVI1 via the ubiquitin-proteasome pathway and MDS1 in a proteasome-independent manner.
Activation of the Evi-1 gene was first described to be associated with the transformation of murine myeloid leukaemias and has previously been detected in cases of human acute myeloid leukaemia (AML) and chronic myeloid leukaemia (CML) in blast crises and in myelodysplastic syndromes.
RUNX1-EVI1 is a chimeric gene generated by t(3;21)(q26;q22) observed in patients with aggressive transformation of myelodysplastic syndrome or chronic myelogenous leukemia.
The t(3;21)(q26.2;q22) translocation is a rare chromosomal abnormality exhibited almost exclusively in therapy-related myelodysplastic syndrome/acute myeloid leukemia (t-MDS/AML) or in the blastic crisis phase of chronic myelogenous leukemia, which results in the fusion of the runt related transcription factor 1 (<i>RUNX1</i>, also called <i>AML1</i>) gene at 21q22 to the myelodysplasia syndrome 1 (<i>MDS1</i>)-ecotropic virus integration site 1 (<i>EVI1</i>) complex locus (<i>MECOM</i>) at 3q26.2, generating various fusion transcripts, including <i>AML1/MDS1/EVI1</i> (<i>AME</i>).
The EVI1 gene may be expressed through at least two pathways in hematologic malignancies; one is related to chromosomal changes at 3q26, while the other is related to myelodysplasia regardless of chromosomal changes at 3q26 region.
We previously defined the most frequent region of copy number increase at 3q26.2 to EVI1 (ecotropic viral integration site-1) and MDS1 (myelodysplastic syndrome 1) (aka MECOM), an observation recently confirmed by the cancer genome atlas (TCGA).
EVI1 RNA was expressed in 29% of 34 (95% confidence interval, 20% to 50%) patients with the MDS subtypes refractory anemia (RA), refractory anemia with excess blasts (RAEB), or refractory anemia with excess blasts in transformation (RAEB-T).
In contrast, EVI-1 is barely expressed in normal hematopoietic cells, but it is overexpressed in chronic myelocytic leukemia in blastic crisis and myelodysplastic syndrome-derived leukemia.
Development and progression of MDS to acute myeloid leukemia is suggested to be a multistep alteration to hematopoietic stem cells consisting of class I and class II alterations: the former targeting genes that are involved in signal transduction (e.g., FLT3, RAS and KIT), whereas the latter affect transcription factors (e.g., RUNX, RARA, EVI1 and WT1).
We investigated whether cytogenetically cryptic EVI1 rearrangements may cause EVI1 overexpression in myeloid malignancies without 3q26 abnormalities and investigated 983 patients with AML (n = 606) or myelodysplastic syndromes (MDS; n = 377) with normal karyotype (CN-AML/CN-MDS, n = 594) or chromosome 7 abnormalities (n = 389) for EVI1 rearrangements using interphase FISH.
Development of a dual-color, double fusion FISH assay to detect RPN1/EVI1 gene fusion associated with inv(3), t(3;3), and ins(3;3) in patients with myelodysplasia and acute myeloid leukemia.
Interestingly, among integration sites identified, Evi1 seemed to collaborate with an AML1 mutant harboring a point mutation in the Runt homology domain (D171N) to induce MDS/AML with an identical phenotype characterized by marked hepatosplenomegaly, myeloid dysplasia, leukocytosis, and biphenotypic surface markers.
The other child did not develop MDS despite expansion of a clone with a single insertion in the myelodysplasia syndrome 1 (MDS1) gene and was cured by early standard allo-HSCT.
Because of the transcriptional activation of the EVI1 family genes in both t(1;3)(p36;q21)-positive MDS/AML and 3q21q26 syndrome, it is suggested that they share a common molecular mechanism for the leukemogenic transformation of the cells.
The PRDM16 (1p36) gene is rearranged in acute myeloid leukaemia (AML) and myelodysplastic syndrome (MDS) with t(1;3)(p36;q21), sharing characteristics with AML and MDS with MECOM (3q26.2) translocations.