3q26.2/EVI1 rearrangement is associated with poor prognosis in classical Philadelphia chromosome-negative myeloproliferative neoplasms

Newly designed breakapart FISH probe helps to identify cases with true MECOM rearrangement in myeloid malignancies

A home-brew, tri-color MECOM breakapart FISH probe with a full MECOM coverage labeled with a separate dye is compared in parallel with a 2-color commercial MECOM breakapart probe in 17 cases of hematologic malignancies. Cases with a typical positive signal pattern (or "balanced" signal pattern) (n = 2) and a negative result (n = 3) using the commercial probe achieved the same results using the new probe (100% concordance), whereas 9 of 12 (75%) remaining cases with an atypical signal pattern (or "unbalanced" signal pattern) using the commercial probe showed a "balanced" signal pattern using the new probe. Three cases with undetermined MECOM rearrangement status by the commercial probe were further clarified with no MECOM rearrangement in 2 cases and presence of a subclone with simultaneous gain and rearrangement of MECOM in 1 case. More importantly, the new probe is capable of determining the presence, location and integrity of MECOM after rearrangement. In conclusion, atypical signal patterns obtained using a commercial FISH probe for MECOM can be solved through re-design and optimization of a new BAP probe, especially in those cases with a true MECOM rearrangement. The potential of the new probe for use in the clinical laboratory will be further investigated. (Word count: 196).

EVI1 overexpression reprograms hematopoiesis via upregulation of Spi1 transcription

Inv(3q26) and t(3:3)(q21;q26) are specific to poor-prognosis myeloid malignancies, and result in marked overexpression of EVI1, a zinc-finger transcription factor and myeloid-specific oncoprotein. Despite extensive study, the mechanism by which EVI1 contributes to myeloid malignancy remains unclear. Here we describe a new mouse model that mimics the transcriptional effects of 3q26 rearrangement. We show that EVI1 overexpression causes global distortion of hematopoiesis, with suppression of erythropoiesis and lymphopoiesis, and marked premalignant expansion of myelopoiesis that eventually results in leukemic transformation. We show that myeloid skewing is dependent on DNA binding by EVI1, which upregulates Spi1, encoding master myeloid regulator PU.1. We show that EVI1 binds to the -14 kb upstream regulatory element (-14kbURE) at Spi1; knockdown of Spi1 dampens the myeloid skewing. Furthermore, deletion of the -14kbURE at Spi1 abrogates the effects of EVI1 on hematopoietic stem cells. These findings support a novel mechanism of leukemogenesis through EVI1 overexpression.

3q26/EVI1 rearrangement in myelodysplastic/myeloproliferative neoplasms: An early event associated with a poor prognosis

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. In this study, we aim to explore the clinicopathological features of myelodysplastic/myeloproliferative (MDS/MPN) neoplasms with 3q26.2/EVI1 rearrangements and determine the potential impact of these cytogenetic abnormalities on treatment response and survival. The study group included 12 cases of MDS/MPN with 3q26.2 rearrangements detected by conventional karyotyping. There were 7 men and 5 women with a median age of 67 years (range, 51-79 years) at time of initial MDS/MPN diagnosis. Ten cases were classified as chronic myelomonocytic leukemia (CMML) and 2 were MDS/MPN, unclassifiable. Among CMML cases, 5 (50%) were proliferative type and 5 (50%) were dysplastic type. Based on blast counts, these 10 CMML were: CMML-0 (n = 2), CMML-1 (n = 3), and CMML-2 (n = 5). Eleven (92%) patients had 3q26 rearrangements at the initial diagnosis. Inv(3)(q21q26.2) was most common, identified in 7(58%) patients, followed by t(3;21)(q26.2;q22) in 2 patients and 1 patient each with t(3;3)(q21;q26.2), t(2;3)(p21;q26-27), and t(3;6)(q26.2;q26). Six (50%) patients had 3q26.2 rearrangements as a sole cytogenetic abnormality and 6 (50%) patients had additional cytogenetic abnormalities. Molecular studies revealed DNMT3A mutations in all 3 patients assessed and RAS mutations in 2 of 8 (25%) patients. No mutations in ASXL1 (n = 3), TET2 (n = 3), FLT3 ITD/D835 (n = 10), and CEBPA (n = 7) were detected. Most patients received hypomethylating agent based chemotherapy. The median follow-up was 11.5 months (range, 1.5-24 months) and at time of last follow-up, 11 (92%) died with a median survival of 13.4 months (range, 1.5-24 months). The only patient alive had a relatively short follow-up of 2.4 months and showed disease progression at the last visit. In conclusion, 3q26.2/EVI1 rearrangements are a rare event and usually present at time of initial diagnosis in MDS/MPN. The presence of 3q26.2/EVI1 rearrangements in MDS/MPN is associated with rapid disease progression, poor response to treatment, and a poor prognosis.