Abnormalities of 3q21 and 3q26 in myeloid malignancy: a United Kingdom Cancer Cytogenetic Group study

Acute myeloid leukemia with rare recurring translocations-an overview of the entities included in the international consensus classification

Two different systems exist for subclassification of acute myeloid leukemia (AML); the World Health Organization (WHO) Classification and the International Consensus Classification (ICC) of myeloid malignancies. The two systems differ in their classification of AML defined by recurrent chromosomal abnormalities. One difference is that the ICC classification defines an AML subset that includes 12 different genetic abnormalities that occur in less than 4% of AML patients. These subtypes exhibit distinct clinical traits and are associated with treatment outcomes, but detailed description of these entities is not easily available and is not described in detail even in the ICC. We searched in the PubMed database to identify scientific publications describing AML patients with the recurrent chromosomal abnormalities/translocations included in this ICC defined patient subset. This patient subset includes AML with t(1;3)(p36.3;q21.3), t(3;5)(q25.3;q35.1), t(8;16)(p11.2;p13.3), t(1;22)(p13.3;q13.1), t(5;11)(q35.2;p15.4), t(11;12)(p15.4;p13.3) (involving NUP98), translocation involving NUP98 and other partner, t(7;12)(q36.3;p13.2), t(10;11)(p12.3;q14.2), t(16;21)(p11.2;q22.2), inv(16)(p13.3q24.3) and t(16;21)(q24.3;q22.1). In this updated review we describe the available information with regard to frequency, biological functions of the involved genes and the fusion proteins, morphology/immunophenotype, required diagnostic procedures, clinical characteristics (including age distribution) and prognostic impact for each of these 12 genetic abnormalities.

Diagnostic challenge in mixed phenotype acute leukemia with T/megakaryocyte or T/myeloid lineages accompanied by t(3;3)

Background

The diagnosis of mixed phenotype acute leukemia (MPAL) with T/megakaryocyte or T/myeloid lineages accompanied by t(3;3) is always a challenge. Therefore, multiple experimental methods are usually required to avoid misdiagnosis. In this report, we presented a rare case of MPAL with T/myeloid lineages accompanied by t(3;3) and discussed the experience of differential diagnosis and our appreciation of the MPAL with T/megakaryocyte and T/myeloid lineages accompanied by t(3;3).

Case presentation:

A 31-year-old woman was admitted to our hospital due to recurrent fever for 20 days. Two distinct blast populations were detected by flow cytometry analysis: one population fulfills the immunophenotypic criteria for T-lymphoblastic leukemia, while the other population is highly suggestive of megakaryoblasts. These immunophenotypic features support the diagnosis of MPAL (T/megakaryocyte), which is rarely reported​. Interestingly, a complex karyotype was detected afterward by cytogenetics with t(3;3)(q21;q26.2), indicating a diagnosis of AML with t(3;3), a subset of which is also characterized by megakaryocytic markers such as CD41 and CD61. It seems that the second blast population detected by flow cytometry could not be classified into either diagnosis based on the morphology, immunophenotyping, and even cytogenetic findings, posing a real diagnostic problem because of the lack of clear-cut cytogenetic morphological defined criteria to distinguish between acute megakaryocytic leukemia and AML with t(3;3). Combining all of the examination data, this case was ultimately diagnosed as MPAL (T + My)-NOS with t(3;3) through differential diagnosis. Before the cytogenetic results were available, the patient received an acute lymphoblastic leukemia (ALL) regimen for MPAL treatment, but the effect was unsatisfactory. After the diagnosis was clear, she received an AML-like regimen with azacitidine for 7 days and venetoclax for 14 days, and achieved complete morphological remission.

Conclusion

MPAL with either T/megakaryocyte or T/myeloid lineages accompanied by t(3;3) is rare, and it is difficult to make a clear diagnosis. Thus, comprehensive examinations, including bone marrow cell morphology, flow cytometry analysis, cytogenetics, and molecular analysis are recommended to avoid misdiagnosis. AML-like regimen including azacitidine and venetoclax may be effective for treating MPAL (T + My)-NOS with t(3;3).

PRDM16, LRP1 and TRPM8 genetic polymorphisms are risk factor for Pakistani migraine patients

BACKGROUND

Migraine is a chronic neurovascular condition characterized by recurring attacks of pulsating headaches. Genome-wide association studies (GWAS) identified many potential loci associated with migraine. To check the association of polymorphisms of PRDM16 (rs2651899), LRP1 (rs11172113), and TRPM8 (rs10166942) with migraine, the first time a case-control study was conducted in understudied Pakistani population.

METHODS

The study included 127 migraine patients (21 in migraine with aura and 106 with migraine without aura group) and 120 healthy control subjects from different areas of Punjab, Pakistan. Blood samples were collected from all the participants, and DNA was isolated from the lymphocytes by the modified organic method. Sanger's sequencing was done for PRDM16 (rs2651899), LRP1 (rs11172113), and TRPM8 (rs10166942) in all the samples to check the genotype. Logistic regression analysis was done using SPSS 20.0 to check the association of these SNPs with migraine susceptibility.

RESULTS

We found statistically significant differences between case and control group for PRDM16 (rs2651899) at genotypic level (p < 0.001), allelic level (p < 0.001; OR 3.088; 95% CI 2.082-4.579) and for dominant model (p < 0.001; OR 5.437; 95% CI 3.112-9.498). The major findings of this study suggested that PRDM16 rs2651899 is strongly associated with migraine in overall and subgroup analysis of genotypes. LRP1 (rs11172113) showed significant association with migraine except in subgroup comparison. A similar trend of association was found for TRPM8 (rs10166942) however, significant association was found only at the allelic level but no significant difference was seen at the genotypic level between case and control. One novel mutation c.67 + 4436_67 + 4438delA was also identified in the current study near LRP1 (rs11172113) polymorphic site.

CONCLUSION

In this first-ever replication report from Pakistan, PRDM16 (rs2651899) was found as a potential genetic marker in migraine susceptibility while LRP1 (rs11172113) and TRPM8 (rs10166942) showed partial association in subgroup analysis.

EVI1 and GATA2 misexpression induced by inv(3)(q21q26) contribute to megakaryocyte-lineage skewing and leukemogenesis

Chromosomal rearrangements between 3q21 and 3q26 elicit high-risk acute myeloid leukemia (AML), which is often associated with elevated platelet and megakaryocyte (Mk) numbers. The 3q rearrangements reposition a GATA2 enhancer near the EVI1 (or MECOM) locus, which results in both EVI1 overexpression and GATA2 haploinsufficiency. However, the mechanisms explaining how the misexpression of these 2 genes individually contribute to leukemogenesis are unknown. To clarify the characteristics of differentiation defects caused by EVI1 and GATA2 misexpression and to identify the cellular origin of leukemic cells, we generated a system to monitor both inv(3) allele-driven EVI1 and Gata2 expression in 3q-rearranged AML model mice. A cell population in which both EVI1 and Gata2 were highly induced appeared in the bone marrows before the onset of frank leukemia. This population had acquired serial colony-forming potential. Because hematopoietic stem/progenitor cells (HSPCs) and Mks were enriched in this peculiar population, we analyzed the independent EVI1 and GATA2 contributions to HSPC and Mk. We found that inv(3)-driven EVI1 promotes accumulation of Mk-biased and myeloid-biased progenitors, Mks, and platelets, and that Gata2 heterozygous deletion enhanced Mk-lineage skewing of EVI1-expressing progenitors. Notably, inv(3)-directed EVI1 expression and Gata2 haploinsufficient expression cooperatively provoke a leukemia characterized by abundant Mks and platelets. These hematological features of the mouse model phenocopy those observed in human 3q AML. On the basis of these results, we conclude that inv(3)-driven EVI1 expression in HSPCs and Mks collaborates with Gata2 haploinsufficiency to provoke Mk-lineage skewing and leukemogenesis with excessive platelets, thus mimicking an important feature of human AML.

Diagnosis of rare subtypes of acute myeloid leukaemia and related neoplasms

The diagnosis of acute myeloid leukaemia and related neoplasms in adults is challenging as this requires the integration of clinical findings, morphology, immunophenotype, cytogenetics, and molecular genetic findings. Lack of familiarity with rare subtypes of acute leukaemia hinders the diagnosis. In this review, we will describe diagnostic findings of several rare acute myeloid leukaemias and related neoplasms that primarily occur in adults including information on presentation, morphology, immunophenotype, genetics, differential diagnosis, and prognosis. Leukaemias discussed include blastic plasmacytoid dendritic cell neoplasm, acute myeloid leukaemia with t(6;9) (p23;q34.1); DEK-NUP214, acute myeloid leukaemia with inv(3)(q21.3q26.2) or t(3;3)(q21.3;q26.2); GATA2, MECOM, acute myeloid leukaemia with BCR-ABL1, acute leukaemias of ambiguous lineage, acute myeloid leukaemia with mutated RUNX1, pure erythroid leukaemia, acute panmyelosis with myelofibrosis, and acute basophilic leukaemia. Case studies with morphological features of the nine subtypes of acute myeloid leukaemia and related neoplasms have been included, and additional evidence available since publication of the 2016 World Health Organization Classification has been added to each subtype.

Myeloid neoplasms associated with t(3;12)(q26.2;p13) are clinically aggressive, show myelodysplasia, and frequently harbor chromosome 7 abnormalities

Sporadic reports of t(3;12)(q26.2;p13) indicate that this abnormality is associated with myeloid neoplasms, myelodysplasia, and a poor prognosis. To better characterize neoplasms with this abnormality, we assessed 20 patients utilizing clinicopathological data, cytogenetic, and targeted next-generation sequencing analysis. We also performed literature review of 58 prior reported cases. Patients included ten men and ten women with median age 55.8 years (range, 27.8-78.8). Diagnoses included 11 acute myeloid leukemia (AML, 5 de novo and 6 secondary), 5 myelodysplastic syndromes (MDS, 3 de novo excess blasts-2 and 2 therapy-related), 2 chronic myeloid leukemia BCR-ABL1-positive blast phase (1 de novo and 1 secondary), 1 primary myelofibrosis (secondary), and 1 mixed-phenotype acute leukemia T/myeloid (MPAL, secondary). Morphologic dysplasia was identified in all AML cases (5/5), MDS cases (4/4), therapy-related cases (3/3), half of myeloproliferative neoplasm cases (1/2), and one MPAL case assessed. The t(3;12) was detected de novo and in subsequent workups in 9 and 11 patients, respectively. Seven patients had t(3;12) only and eight patients had additional chromosome 7 abnormalities. Fluorescence in-situ hybridization detected MECOM (n = 11) and ETV6 (n = 7) rearrangements in all cases assessed. FLT3 internal tandem duplication was identified in five (25%) patients. We identified 13 genetic abnormalities in the de novo group (n = 9), and 25 in the secondary disease group (n = 11). All patients received chemotherapy, with seven allogeneic and two autologous stem cell transplantations. At last follow-up, 14 (70%) patients died with median survival of 6.3 months (range, 0.1-17.3) after detection of t(3;12). In summary, t(3;12)(q26.2;p13) is a rare cytogenetic abnormality in myeloid neoplasms. Myelodysplasia, chromosome 7 abnormalities, and high blast counts are common, and the prognosis is poor. Given the close relationship between the presence of this cytogenetic abnormality and the MDS-related changes, we recommend adding t(3;12)(q26.2;p13) to the list of AML with myelodysplasia-related changes defining abnormalities of the World Health Organization 2017 classification of myeloid neoplasms.

Two effects of GATA2 enhancer repositioning by 3q chromosomal rearrangements

Chromosomal inversion and translocation between 3q21 and 3q26 [inv (3)(q21.3q26.2) and t(3;3)(q21.3;q26.2), respectively] give rise to acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS), which have poor prognoses. The chromosomal rearrangements reposition a GATA2 distal hematopoietic enhancer from the original 3q21 locus to the EVI1 (also known as MECOM) locus on 3q26. Therefore, the GATA2 enhancer from one of two GATA2 alleles drives EVI1 gene expression in hematopoietic stem and progenitor cells, which promotes the accumulation of abnormal progenitors and induces leukemogenesis. On the other hand, one allele of the GATA2 gene loses its enhancer, which results in reduced GATA2 expression. The GATA2 gene encodes a transcription factor critical for the generation and maintenance of hematopoietic stem and progenitor cells. GATA2 haploinsufficiency has been known to cause immunodeficiency and myeloid leukemia. Notably, reduced GATA2 expression suppresses the differentiation but promotes the proliferation of EVI1-expressing leukemic cells, which accelerates EVI1-driven leukemogenesis. A series of studies have shown that the GATA2 enhancer repositioning caused by the chromosomal rearrangements between 3q21 and 3q26 provokes misexpression of both the EVI1 and GATA2 genes and that these two effects coordinately elicit high-risk leukemia.

Molecular and pathologic characterization of AML with double Inv(3)(q21q26.2)

The inv(3)(q21q26.2) altering a single chromosome 3 homolog is an established myeloid malignancy-associated entity. Comparatively, double inv(3) cases involving both homologs are exceedingly rare with 13 reports across AML, CML and MDS. This scarcity was confirmed by finding only 2 new cases out of 34,898 bone marrows collected during a 55 year period at a large medical center (0.0005%). The double inv(3) was detected by karyotype and confirmed by FISH on both homologs in a 41 year old female and a 72 year old male with AML. In the latter case, a 2.26-fold increase in MECOM RNA level was found using an NGS myeloid gene panel. Chromosomal microarray analysis identified segmental copy-neutral loss-of-heterozygosity (CN-LOH) at 3q21 extending to near the q-arm terminus. This is the third report of distal 3q CN-LOH, substantiating that the double inv(3) arises through somatic repair of acquired segmental LOH. Long term clinical and genetic evaluation revealed no discernible morphologic difference between single and double inv(3) cases, conventional chemotherapy resistance and rapid dominance of the double inv(3) clone. The two new cases are consistent with relatively longer survival of double inv(3) patients in the absence of concurrent chromosome 7 loss compared to those with both abnormalities. Importantly, the first known outcome data of bone marrow transplantation in double inv(3) AML is also presented.

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.

Imbalanced expression of polycistronic miRNA in acute myeloid leukemia

miR-1 and miR-133 are clustered on the same chromosomal loci and are transcribed together as a single transcript that is positively regulated by ecotropic virus integration site-1 (EVI1). Previously, we described how miR-133 has anti-tumorigenic potential through repression of EVI1 expression. It has also been reported that miR-1 is oncogenic in the case of acute myeloid leukemia (AML). Here, we show that expression of miR-1 and miR-133, which have distinct functions, is differentially regulated between AML cell lines. Interestingly, the expression of miR-1 and EVI1, which binds to the promoter of the miR-1/miR-133 cluster, is correlative. The expression levels of TDP-43, an RNA-binding protein that has been reported to increase the expression, but inhibits the activity, of miR-1, were not correlated with expression levels of miR-1 in AML cells. Taken together, our observations raise the possibility that the balance of polycistronic miRNAs is regulated post-transcriptionally in a hierarchical manner possibly involving EVI1, suggesting that the deregulation of this balance may play some role in AML cells with high EVI1 expression.

Fusion genes in malignant neoplastic disorders of haematopoietic system

OBJECTIVES

The new World Health Organization's (WHO) classification of haematopoietic and lymphoid tissue neoplasms incorporating the recurrent fusion genes as the defining criteria for different haematopoietic malignant phenotypes is reviewed. The recurrent fusion genes incorporated in the new WHO's classification and other chromosomal rearrangements of haematopoietic and lymphoid tissue neoplasms are reviewed.

METHODOLOGY

Cytokines and transcription factors in haematopoiesis and leukaemic mechanisms are described. Genetic features and clinical implications due to the encoded chimeric neoproteins causing malignant haematopoietic disorders are reviewed.

RESULTS AND DISCUSSION

Multiple translocation partner genes are well known for leukaemia such as MYC, MLL, RARA, ALK, and RUNX1. With the advent of more sophisticated diagnostic tools and bioinformatics algorithms, an exponential growth in fusion genes discoveries is likely to increase.

CONCLUSION

Demonstration of fusion genes and their specific translocation breakpoints in malignant haematological disorders are crucial for understanding the molecular pathogenesis and clinical phenotype of cancer, determining prognostic indexes and therapeutic responses, and monitoring residual disease and relapse status.

Complex chromosomal rearrangements leading to MECOM overexpression are recurrent in myeloid malignancies with various 3q abnormalities

Chromosomal rearrangements involving 3q26 are recurrent findings in myeloid malignancies leading to MECOM overexpression, which has been associated with a very poor prognosis. Other 3q abnormalities have been reported and cryptic MECOM rearrangements have been identified in some cases. By fluorescence in situ hybridization (FISH) analysis, we investigated 97 acute myeloid leukemia/myelodysplastic syndrome patients with various 3q abnormalities to determine the role and the frequency of the involvement of MECOM. We identified MECOM rearrangements in 51 patients, most of them showed 3q26 involvement by chromosome banding analysis (CBA): inv(3)/t(3;3) (n = 26) and other balanced 3q26 translocations (t(3q26)) (n = 15); the remaining cases (n = 10) showed various 3q abnormalities: five with balanced translocations involving 3q21 or 3q25; two with homogenously staining region (hsr) on 3q; and three with other various 3q abnormalities. Complex rearrangements with multiple breakpoints on 3q, masking 3q26 involvement, were identified in cases with 3q21/3q25 translocations. Furthermore, multiple breaks were observed in two cases with t(3q26), suggesting that complex rearrangement may also occur in apparently simple t(3q26). Intrachromosomal gene amplification was another mechanism leading to MECOM overexpression in two cases with hsr on 3q. In the last three cases, FISH analysis revealed 3q26 involvement that was missed by CBA because of metaphases' suboptimal quality. All cases with MECOM rearrangements showed overexpression by real-time quantitative PCR. Finally, MECOM rearrangements can occur in patients with 3q abnormalities even in the absence of specific 3q26 involvement, underlining that their frequency is underestimated. As MECOM rearrangement has been associated with very poor prognosis, its screening should be performed in patients with any 3q abnormalities.

Double inv(3)(q21q26.2) in acute myeloid leukemia is resulted from an acquired copy neutral loss of heterozygosity of chromosome 3q and associated with disease progression

Background

Acute myeloid leukemia (AML) with inv(3)(q21q26.2)/t(3;3)(q21;q26.2) is a distinct clinicopathologic entity with a poor prognosis. However, double inv(3)(q21q26.2) is extremely rare in AML. We report here 3 cases analyzed by oligonucleotide microarray comparative genomic hybridization (aCGH) and single nucleotide polymorphism (SNP). Clinicopathologic, cytogenetic and molecular findings were correlated with clinical outcome to better understand the entity.

Results

The study group included one man and two women at 56–74 years of age. The AML arose from myelodysplastic syndrome in one patient and from chronic myelomonocytic leukemia in another patient. Monosomy 7 was found as additional cytogenetic finding in one patient. One patient had a single inv(3) in the initial clone and acquired double inv(3) as part of clonal evolution. EVI1 (MECOM) rearrangement was confirmed using metaphase/interphase fluorescence in situ hybridization (FISH). Microarray (aCGH + SNP) data analysis revealed that the double inv(3) was a result of acquiring copy neutral loss of heterozygosity of chromosome 3q: arr[hg19] 3q13.21q29(10,344,387–197,802,470)x2 hmz, spanning ~ 94.3 Mb in size. Mutational profiling showed a PTPN11 mutation at a low level (~10 %) in one patient and wild type FLT3 and RAS in all patients. No patients achieved cytogenetic remission and all died with an overall survival (OS) of 23, 12 and 5 months, respectively.

Conclusions

Double inv(3) is a result of acquired copy neutral loss of heterozygosity, a somatic repair event occurring as a part of mitotic recombination of the partial chromosome 3q. The double inv(3) in AML patients is highly associated with a rapid disease progression.

Successful treatment of both double minute of C-MYC and BCL-2 rearrangement containing large B-cell lymphoma with subsequent unfortunate development of therapy-related acute myeloid leukemia with t(3;3)(q26.2;q21)

Double minute chromosomes (DMs), although relatively frequently encountered in solid tumors, are rare in hematologic neoplasms such as acute myeloid leukemia (AML), and even rarer in lymphoid neoplasms. t(3;3)(q26.2;q21) is a very rare genetic alteration observed in myeloid neoplasm. Herein we report an interesting and unique case of concomitant C-MYC DMs and t(14;18)-containing large B-cell lymphoma, which was successfully treated with R-hyper-CVAD; unfortunately, the patient has developed a therapy-related AML (t-AML) 2 years since the start of his lymphoma treatment. His t-AML contains both t(3;3)(q26.2;q21) and monosomy 7, and the patient died of AML 10 months after the initial diagnosis of t-AML despite clinical remission. To the best of our knowledge, this is the first reported case of C-MYC DM-containing de novo large B-cell lymphoma, which was successfully treated with complete remission, but unfortunately died of t-AML harboring t(3;3)(q21;q26).

Genetic variation at MECOM, TERT, JAK2 and HBS1L-MYB predisposes to myeloproliferative neoplasms

Clonal proliferation in myeloproliferative neoplasms (MPN) is driven by somatic mutations in JAK2, CALR or MPL, but the contribution of inherited factors is poorly characterized. Using a three-stage genome-wide association study of 3,437 MPN cases and 10,083 controls, we identify two SNPs with genome-wide significance in JAK2(V617F)-negative MPN: rs12339666 (JAK2; meta-analysis P=1.27 × 10(-10)) and rs2201862 (MECOM; meta-analysis P=1.96 × 10(-9)). Two additional SNPs, rs2736100 (TERT) and rs9376092 (HBS1L/MYB), achieve genome-wide significance when including JAK2(V617F)-positive cases. rs9376092 has a stronger effect in JAK2(V617F)-negative cases with CALR and/or MPL mutations (Breslow-Day P=4.5 × 10(-7)), whereas in JAK2(V617F)-positive cases rs9376092 associates with essential thrombocythemia (ET) rather than polycythemia vera (allelic χ(2) P=7.3 × 10(-7)). Reduced MYB expression, previously linked to development of an ET-like disease in model systems, associates with rs9376092 in normal myeloid cells. These findings demonstrate that multiple germline variants predispose to MPN and link constitutional differences in MYB expression to disease phenotype.

Potential relationship between inadequate response to DNA damage and development of myelodysplastic syndrome

Hematopoietic stem cells (HSCs) are responsible for the continuous regeneration of all types of blood cells, including themselves. To ensure the functional and genomic integrity of blood tissue, a network of regulatory pathways tightly controls the proliferative status of HSCs. Nevertheless, normal HSC aging is associated with a noticeable decline in regenerative potential and possible changes in other functions. Myelodysplastic syndrome (MDS) is an age-associated hematopoietic malignancy, characterized by abnormal blood cell maturation and a high propensity for leukemic transformation. It is furthermore thought to originate in a HSC and to be associated with the accrual of multiple genetic and epigenetic aberrations. This raises the question whether MDS is, in part, related to an inability to adequately cope with DNA damage. Here we discuss the various components of the cellular response to DNA damage. For each component, we evaluate related studies that may shed light on a potential relationship between MDS development and aberrant DNA damage response/repair.

The prognostic significance of an inv(3)(q21q26.2) in addition to a t(9;22)(q34;q11.2) in patients treated with tyrosine kinase inhibitors

In chronic myelogenous leukemia, BCR-ABL1 positive detection of cytogenetic abnormalities in addition to the t(9;22) is thought to portend a poor prognosis; however, not all abnormalities associated with the t(9;22) have the same impact. Inv(3) defines a group of aggressive neoplasms with poor response to conventional treatment options. In this study, four cases with the t(9;22) and inv(3) treated with tyrosine kinase inhibitors (TKI) were investigated. In three cases, the inv(3) was not detected at the initial diagnosis and the patients initially responded to TKI therapy; the inv(3) was detected at blast crisis in all three cases, and one case had both abnormalities at the initial presentation, but this case presented as acute myeloid leukemia. In all cases, detection of an inv(3) was associated with a high blast count and a lack of response to treatment regimens including TKI. All patients died within months from the detection of inv(3). This indicates that cases with the t(9;22) and inv(3) have a clinical course similar to that of cases with an inv(3) and no other therapeutically targetable abnormality.

Myeloid Neoplasms with inv(3)(q21q26.2) or t(3;3)(q21;q26.2)

Acute myeloid leukemia (AML) with inv(3)(q21q26.2)/t(3;3)(q21;q26.2) [inv3/t(3;3)] is a distinct entity under the subgroup of AMLs with recurrent genetic abnormalities in the 2008 World Health Organization classification. Myelodysplastic syndrome (MDS) with inv3/t(3;3) has a high risk of progression to AML. AML and MDS with inv3/t(3;3) have a similarly aggressive clinical course with short overall survival (OS) and are commonly refractory to therapy. In this article, clinical and pathologic features and prognosis in AML and MDS with inv3/t(3;3) are reviewed, and other myeloid neoplasms with similar dysplastic features to be differentiated from AML and MDS with inv3/t(3;3) are discussed.

A novel t(3;12)(q21;p13) translocation in a patient with accelerated chronic myeloid leukemia after imatinib and nilotinib therapy

The acquisition of secondary chromosomal aberrations in chronic myeloid leukemia (CML) patients with Philadelphia chromosome-positive (Ph+) karyotype signifies clonal evolution associated with the progression of the disease to its accelerated or blastic phase. Therefore, these aberrations have clinical and biological significance. T(3;12)(q26;p13), which is a recurrent chromosomal aberration observed in myeloid malignancies, is typically associated with dysplasia of megakaryocytes, multilineage involvement, short duration of any blastic phase, and extremely poor prognosis. We have identified a recurrent reciprocal translocation between chromosomes 3 and 12 with different breakpoint at bands 3q21 in the malignant cells from a 28-year-old man. The patient was initially diagnosed as having Ph+ CML in the chronic phase. The t(3;12)(q21;p13) translocation occurred 4 years after the patient was first diagnosed with CML while undergoing tyrosine kinase inhibitor therapy. We confirmed the t(3;12)(q21;p13) translocation via fluorescence in situ hybridization assay by using whole-chromosome paint probes for chromosomes 3 and 12. Our findings demonstrate that, similar to other recurrent translocations involving 3q26 such as t(3;3) and t(3;21), the t(3;12)(q21;p13) translocation is implicated not only in myelodysplastic syndrome and acute myeloid leukemia but also in the progression of CML. These findings extend the disease spectrum of this cytogenetic aberration.

Overexpression of EVI1 interferes with cytokinesis and leads to accumulation of cells with supernumerary centrosomes in G0/1 phase

Ectopic viral integration site 1 (EVI1), a transcription factor frequently overexpressed in myeloid neoplasias, has been implicated in the generation of malignancy-associated centrosomal aberrations and chromosomal instability. Here, we sought to investigate the underlying cause of centrosome amplification in EVI1-overexpressing cells. We found that overexpression of EVI1-HA in U2OS cells induced supernumerary centrosomes, which were consistently associated with enlarged nuclei or binuclear cells. Live cell imaging experiments identified cytokinesis failure as the underlying cause of this phenotype. In accordance with previous reports, EVI1 overexpression induced a partial cell cycle arrest in G0/1 phase, accompanied by elevated cyclin D1 and p21 levels, reduced Cdk2 activity and activation of the p53 pathway. Supernumerary centrosomes predominantly occurred in resting cells, as identified by low levels of the proliferation marker Ki-67, leading to the conclusion that they result from tetraploidization after cytokinesis failure and are confined to G0/1-arrested tetraploid cells. Depletion of p53 using siRNA revealed that further polyploidization of these cells was inhibited by the p53-dependent tetraploidy checkpoint.

Diagnostic and prognostic value of cytogenetics in acute myeloid leukemia

The last 4 decades have seen major advances in understanding the genetic basis of acute myeloid leukemia (AML), and substantial improvements in survival of children and young adults with the disease. A key step forward was the discovery that AML cells harbor recurring cytogenetic abnormalities. The identification of the genes involved in chromosomal rearrangements has provided insights into the regulation of normal hematopoiesis and how disruption of key transcription factors and epigenetic modulators promote leukemic transformation. Cytogenetics has been widely adopted to provide the framework for development of risk-stratified treatment approaches to patient management.

Genetics of migraine in the age of genome-wide association studies

Genetic factors importantly contribute to migraine. However, unlike for rare monogenic forms of migraine, approaches to identify genes for common forms of migraine have been of limited success. Candidate gene association studies were often negative and positive results were often not replicated or replication failed. Further, the significance of positive results from linkage studies remains unclear owing to the inability to pinpoint the genes under the peaks that may be involved in migraine. Problems hampering these studies include limited sample sizes, methods of migraine ascertainment, and the heterogeneous clinical phenotype. Three genome-wide association studies are available now and have successfully identified four new genetic variants associated with migraine. One new variant (rs1835740) modulates glutamate homeostasis, thus integrates well with current concepts of neurotransmitter disturbances. This variant may be more specific for severe forms of migraine such as migraine with aura than migraine without aura. Another variant (rs11172113) implicates the lipoprotein receptor LRP1, which may interact with neuronal glutamate receptors, thus also providing a link to the glutamate pathway. In contrast, rs10166942 is in close proximity to TRPM8, which codes for a cold and pain sensor. For the first time this links a gene explicitly implicated in pain related pathways to migraine. The potential function of the fourth variant rs2651899 (PRDM16) in migraine is unclear. All these variants only confer a small to moderate change in risk for migraine, which concurs with migraine being a heterogeneous disorder. Ongoing large international collaborations will likely identify additional gene variants for migraine.

Myelodysplastic syndrome with inv(3)(q21q26.2) or t(3;3)(q21;q26.2) has a high risk for progression to acute myeloid leukemia

Acute myeloid leukemia (AML) with inv(3) (q21q26.2) or t(3;3)(q21;q26.2) is a distinct subtype in the World Health Organization classification. The natural history of myelodysplastic syndrome (MDS) associated with these cytogenetic aberrations is poorly understood. We studied 17 MDS (11 de novo and 6 therapy related) and 3 chronic myelomonocytic leukemia (CMML) cases associated with inv(3) (q21q26.2) or t(3;3)(q21;q26.2). The de novo cases were further classified as refractory cytopenia with multilineage dysplasia (n = 8) and refractory anemia with excess blasts (n = 3). Isolated inv(3)/t(3;3) was identified in 4 cases, whereas -7/7q (n = 13) and -5/5q (n = 6) were common additional aberrations. Nineteen patients died, including 13 in whom the disease progressed to AML after a median of 7 months. Median survival for patients with de novo disease was similar to that for patients with therapy-related MDS (13 vs 17.5 months). MDS or CMML with inv(3)/t(3;3) are aggressive diseases with a high risk of progression to AML.

Genome-wide association study reveals three susceptibility loci for common migraine in the general population

Migraine is a common, heterogeneous and heritable neurological disorder. Its pathophysiology is incompletely understood, and its genetic influences at the population level are unknown. In a population-based genome-wide analysis including 5,122 migraineurs and 18,108 non-migraineurs, rs2651899 (1p36.32, PRDM16), rs10166942 (2q37.1, TRPM8) and rs11172113 (12q13.3, LRP1) were among the top seven associations (P < 5 × 10(-6)) with migraine. These SNPs were significant in a meta-analysis among three replication cohorts and met genome-wide significance in a meta-analysis combining the discovery and replication cohorts (rs2651899, odds ratio (OR) = 1.11, P = 3.8 × 10(-9); rs10166942, OR = 0.85, P = 5.5 × 10(-12); and rs11172113, OR = 0.90, P = 4.3 × 10(-9)). The associations at rs2651899 and rs10166942 were specific for migraine compared with non-migraine headache. None of the three SNP associations was preferential for migraine with aura or without aura, nor were any associations specific for migraine features. TRPM8 has been the focus of neuropathic pain models, whereas LRP1 modulates neuronal glutamate signaling, plausibly linking both genes to migraine pathophysiology.

[A case of t(3;3)(q21;q26.2) associated with severe multilineage dysplasia and multi-drug resistance in blastic crisis of chronic myelogenous leukemia]

The t(3;3)(q21;q26.2) is known to be mainly observed in hematologic myeloid malignancies, as a form of 3q21q26 syndrome. Cytogenetic abnormalities of 3q21q26 syndrome result in RPN1-EVI1 fusion transcripts involving ecotropic viral integration site-1 (EVI1) at 3q26.2 and ribophorin I (RPN1) at 3q21, and the fusion transcripts play an important role in leukemogenesis and disease progression. They are usually associated with dysplasia, especially of megakaryocytes. Patients with these cytogenetic abnormalities show extremely poor prognosis even with aggressive anti-leukemic therapy. We report a case of blastic crisis of CML with both t(3;3)(q21;q26.2) and t(9;22)(q34;q11.2) and associated severe multilineage dysplasia. The patient showed a poor response to imatinib, dasatinib and aggressive induction therapy. When both t(3;3)(q21;q26.2) and t(9;22)(q34;q11.2) are observed in cases of leukemia with increased blasts, they are best considered as aggressive phases of CML with t(3;3)(q21;q26.2), rather than AML with t(9;22)(q34;q11.2) by 2008 WHO classification.

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

Approximately 2-3% of adult patients with acute myeloid leukemia harbor a rearrangement of RPN1 (at 3q21) and EVI1 (at 3q26.2) as inv(3)(q21q26.2), t(3;3)(q21;q26.2), or ins(3;3)(q26.2;q21q26.2). The most recent World Health Organization (WHO) classification has designated AML with inv(3) or t(3;3) and associated RPN1/EVI1 fusion, as a distinct AML subgroup associated with an unfavorable prognosis. We have created a dual color, double fusion fluorescence in situ hybridization (D-FISH) assay to detect fusion of the RPN1 and EVI1 genes. A blinded investigation was performed using 30 normal bone marrow samples and 51 bone marrow samples from 17 patients with inv(3)(q21q26.2), 11 patients with t(3;3)(q21;q26.2), and one patient with ins(3;3)(q26.2;q21q26.2) previously defined by chromosome analysis. The unblinded results indicated abnormal RPN1/EVI1 fusion results in 30 (97%) of 31 samples from the inv(3)(q21q26.2) group including seven bone marrow samples for which chromosome analysis was unsuccessful or failed to detect an inv(3)(q21q26.2). Abnormal FISH results were detected in 14 (88%) of 16 samples with t(3;3)(q21;q26.2) and in the sole sample with an ins(3;3)(q26.2;q21q26.2). All 30 negative controls were normal and were used to establish a normal cutoff of 0.6% for the typical abnormal D-FISH signal pattern. Overall, this D-FISH assay was more accurate than chromosome analysis and based on the normal cutoff of 0.6%, this assay can be used for minimal residual disease detection and disease monitoring in patients with RPN1/EVI1 fusion.

Clinical, molecular, and prognostic significance of WHO type inv(3)(q21q26.2)/t(3;3)(q21;q26.2) and various other 3q abnormalities in acute myeloid leukemia

PURPOSE

Acute myeloid leukemia (AML) with inv(3)(q21q26.2)/t(3;3)(q21;q26.2) [inv(3)/t(3;3)] is recognized as a distinctive entity in the WHO classification. Risk assignment and clinical and genetic characterization of AML with chromosome 3q abnormalities other than inv(3)/t(3;3) remain largely unresolved.

PATIENTS AND METHODS

Cytogenetics, molecular genetics, therapy response, and outcome analysis were performed in 6,515 newly diagnosed adult AML patients. Patients were treated on Dutch-Belgian Hemato-Oncology Cooperative Group/Swiss Group for Clinical Cancer Research (HOVON/SAKK; n = 3,501) and German-Austrian Acute Myeloid Leukemia Study Group (AMLSG; n = 3,014) protocols. EVI1 and MDS1/EVI1 expression was determined by real-time quantitative polymerase chain reaction.

RESULTS

3q abnormalities were detected in 4.4% of AML patients (288 of 6,515). Four distinct groups were defined: A: inv(3)/t(3;3), 32%; B: balanced t(3q26), 18%; C: balanced t(3q21), 7%; and D: other 3q abnormalities, 43%. Monosomy 7 was the most common additional aberration in groups (A), 66%; (B), 31%; and (D), 37%. N-RAS mutations and dissociate EVI1 versus MDS1/EVI1 overexpression were associated with inv(3)/t(3;3). Patients with inv(3)/t(3;3) and balanced t(3q21) at diagnosis presented with higher WBC and platelet counts. In multivariable analysis, only inv(3)/t(3;3), but not t(3q26) and t(3q21), predicted reduced relapse-free survival (hazard ratio [HR], 1.99; P < .001) and overall survival (HR, 1.4; P = .006). This adverse prognostic impact of inv(3)/t(3;3) was enhanced by additional monosomy 7. Group D 3q aberrant AML also had a poor outcome related to the coexistence of complex and/or monosomal karyotypes and cryptic inv(3)/t(3;3).

CONCLUSION

Various categories of 3q abnormalities in AML can be distinguished according to their clinical, hematologic, and genetic features. AML with inv(3)/t(3;3) represents a distinctive subgroup with unfavorable prognosis.

Immunophenotypic features of acute myeloid leukemia with inv(3)(q21q26.2)/t(3;3)(q21;q26.2)

Immunophenotypic identification of myeloid specific antigens is an important diagnostic tool in the management of patients with acute myeloid leukemia (AML). These antigens allow determination of cell of origin and degree of differentiation of leukemia blasts. AML with inv(3)(q21q26.2)/t(3;3)(q21;q26.2) is a relatively rare subtype of AML. The immunophenotypic characteristics of inv(3) AML patients are somewhat limited. We identified 14 new cases of hematological disorders with increased myeloid blasts carrying inv(3)(q21q26.2)/t(3;3)(q21;q26.2). Also, we identified another 13 cases previously published in the literature, where the immunophenotype of inv(3)(q21q26.2) was documented. As a group, patients with AML with inv(3)(q21q26.2) had high levels of early myeloid (CD13, CD33, CD117 and MPO) and uncommitted markers (CD34, HLA-DR and CD56) and a high rate of monosomy 7 in addition to the inv(3)(q21q26.2). Differential karyotype and expression of certain antigens were noted in patients with de novo AML with inv(3)(q21q26.2) vs. those with inv(3)(q21q26.2)-containing blasts.

The 2008 revision of the World Health Organization (WHO) classification of myeloid neoplasms and acute leukemia: rationale and important changes

Recently the World Health Organization (WHO), in collaboration with the European Association for Haematopathology and the Society for Hematopathology, published a revised and updated edition of the WHO Classification of Tumors of the Hematopoietic and Lymphoid Tissues. The 4th edition of the WHO classification incorporates new information that has emerged from scientific and clinical studies in the interval since the publication of the 3rd edition in 2001, and includes new criteria for the recognition of some previously described neoplasms as well as clarification and refinement of the defining criteria for others. It also adds entities-some defined principally by genetic features-that have only recently been characterized. In this paper, the classification of myeloid neoplasms and acute leukemia is highlighted with the aim of familiarizing hematologists, clinical scientists, and hematopathologists not only with the major changes in the classification but also with the rationale for those changes.

Expression and prognostic significance of different mRNA 5'-end variants of the oncogene EVI1 in 266 patients with de novo AML: EVI1 and MDS1/EVI1 overexpression both predict short remission duration

Rearrangements of chromosome band 3q26.2 lead to overexpression of the EVI1 gene and are associated with a poor prognosis in myeloid malignancies. EVI1 is also overexpressed in some cases without 3q26 rearrangements. To uncover its prognostic significance in this patient group, however, it may be necessary to distinguish among several known 5'-end variants of its mRNA. According to a recent report, overexpression of the transcript variant EVI1_1d was associated with shortened survival in acute myeloid leukemia (AML), but overexpression of MDS1/EVI1, whose protein product differs structurally and functionally from that of all other known EVI1 5'-end variants, was not. The aim of the present study was to determine, for the first time, the expression and prognostic significance of all known EVI1 5'-end variants in AML. Quantitative RT-PCR was used to measure the expression of EVI1_1a, EVI1_1b, EVI1_1d, EVI1_3L, and MDS1/EVI1 in 266 samples from patients with de novo AML. To correlate expression of the EVI1 5'-end variants with survival parameters, regression analyses were performed. 41/266 patients (15.4%) overexpressed at least one, but more often several or all, EVI1 transcript type(s). High expression of each of the EVI1 mRNA variants, including MDS1/EVI1, was significantly associated with shortened continuous complete remission in the total patient population as well as in the subgroups of patients with intermediate risk or normal cytogenetics. The present study therefore shows that high levels of each of the known EVI1 mRNA 5'-end variants represents an adverse prognostic factor in de novo AML without 3q26 rearrangements. This article contains Supplementary Material available at http://www.interscience.wiley.com/jpages/1045-2257/suppmat.

The MDS1-EVI1 gene complex as a retrovirus integration site: impact on behavior of hematopoietic cells and implications for gene therapy

Gene therapy trials have been performed with virus-based vectors that have the ability to integrate permanently into genomic DNA and thus allow prolonged expression of corrective genes after transduction of hematopoietic stem and progenitor cells. Adverse events observed during the X-linked severe combined immunodeficiency gene therapy trial revealed a significant risk of genotoxicity related to retrovirus vector integration and activation of adjacent proto-oncogenes, with several cases of T-cell leukemia linked to vector activation of the LMO2 gene. In patients with chronic granulomatous disease (CGD), rhesus macaques, and mice receiving hematopoietic stem and progenitor cells transduced with retrovirus vectors, a highly non-random pattern of vector integration has been reported. The most striking finding has been overrepresentation of integrations in one specific genomic locus, a complex containing the MDS1 and the EVI1 genes. Most evidence suggests that this overrepresentation is primarily due to a modification of primitive myeloid cell behavior by overexpression of EVI1 or MDS1-EVI1, as opposed to a specific predilection for integration at this site. Three different proteins can be produced from this complex locus: MDS1, MDS1-EVI1, and EVI1. This review will summarize current knowledge regarding this locus and its gene products, with specific focus on issues with relevance to gene therapy, leukemogenesis, and hematopoiesis. Insights into the mechanisms that result in altered hematopoiesis and leukemogenesis when this locus is dysregulated could improve the safety of gene therapy in the future.

[Hematologic and clinical features of 3q21q26 syndrome: extremely poor prognosis and association with central diabetes insipidus]

BACKGROUND

3q21q26 syndrome includes chromosomal abnormalities of inv(3)(q21q26), t(3;3) (q21;q26), and ins(3;3)(q26;q21q26). It causes hematological diseases by the leukemogenic mechanism that the enhancer of ribophorin I gene in 3q21 induces the transcription of ecotropic viral integration site-1 gene in 3q26. Recently, it has been proposed that the 3q21q26 syndrome may be preceded by diabetes insipidus (DI), particularly when combined with monosomy 7, and is a unique disease entity.

METHODS

From May 2001 to June 2006, a total of 5 patients with hematologic malignancy were found to have 3q21q26 syndrome and monosomy 7. Laboratory findings, clinical data, and association with DI were investigated.

RESULTS

The rearrangement type of 3q21q26 was inv(3)(q21q26) in four patients and t(3;3)(q21; q26) in one. These patients' French American British types were AML M1, M2, M4 and M7, showing evident dysmegakaryopoiesis. Aberrant antigenic expressions of CD7 and CD56 were observed. The platelet count was relatively high as AML. All the five patients were refractory or in early relapse. Patient 5 was diagnosed with AML M7 20 days after being diagnosed with DI. While DI was well controlled with oral desmopressin, leukemia was refractory to chemotherapy.

CONCLUSIONS

This study supports the recent opinion that 3q21q26 syndrome with monosomy 7 combined with DI is a disease of unique characteristics. In the relation between DI and monosomy 7 or 3q21q26 syndrome, there has been no explanation about how acquired abnormality of hematopoietic cells affects production of DDAVP by neurohormonal cells in hypothalamus. The mechanism needs further study, and this research should contribute to the understanding of genetic roles in leukemia appearing in different forms.

Leukemogenesis of the EVI1/MEL1 gene family

Leukemia is a group of monoclonal diseases that arise from hematopoietic stem and progenitor cells in the bone marrow or other hematopoietic organs. Retroviral infections are one of the major events leading to leukemogenesis in mice, because retroviruses can induce hematopoietic disease via the insertional mutagenesis of oncogenes; therefore, the cloning of viral-integration sites in murine leukemia has provided valuable molecular tags for oncogene discovery. Transcription of the murine gene ecotropic viral-integration site 1 (Evi1) is activated by nearby viral integration. In humans, the Evi1 homologue EVI1 is activated by chromosomal translocations. This review discusses the roles of the overexpression of EVI1/MEL1 gene family members in leukemogenesis, the relationships of various translocations in EVI1 overexpression, and the importance of PR domains in tumor suppression and oncogenesis. The functions of EVI1/MEL1 members as transcription factors and the concept of EVI1-positive leukemia as a stem cell disease are also reviewed.

The oncogene and developmental regulator EVI1: expression, biochemical properties, and biological functions

The EVI1 gene codes for a zinc finger transcription factor with important roles both in normal development and in leukemogenesis. Transcriptional activation of this gene through chromosome rearrangements or other, yet to be identified mechanisms leads to particularly aggressive forms of human myeloid leukemia. In vitro as well as in animal model systems, EVI1 affected cellular proliferation, differentiation, and apoptosis in cell type specific ways. Retroviral integrations into the EVI1 locus provided cells with increased abilities to engraft, survive, and proliferate in bone marrow transplantation experiments. Experimental overexpression of EVI1 by itself was insufficient to cause leukemia in animal model systems, but it cooperated with other genes in this process. This review summarizes the currently available experimental evidence for the proposed biochemical and biological functions of this important oncogene.

Monosomy 7 and deletion 7q in children and adolescents with acute myeloid leukemia: an international retrospective study

Monosomy 7 (-7) and deletion 7q \del(7q)] are rare in childhood acute myeloid leukemia (AML). We retrospectively collected data on 258 children with AML or refractory anemia with excess blasts in transformation (RAEB-T) and -7 or del(7q) with or without other cytogenetic aberrations \+/- other]. Karyotypes included -7 (n = 90), -7 other (n = 82), del(7q) (n = 21), and del(7q) other (n = 65). Complete remission (CR) was achieved in fewer patients with -7 +/- other compared with del(7q) +/- other (61% versus 89%, P < .001). Overall, the 5-year survival rate was 39% (SE, 3%). Survival was superior in del(7q) +/- other compared with -7 +/- other (51% versus 30%, P < .01). Cytogenetic aberrations considered favorable in AML \t(8;21)(q22;q22), inv(16)(p13q22), t(15;17)(q22;q21), t(9;11)(p22;q23)] (n = 24) were strongly associated with del(7q) and a higher 5-year survival rate compared with del(7q) without favorable cytogenetics (75% versus 46%, P = .03). Patients with -7 and inv(3),-5/del(5q), or + 21 had a 5-year survival rate of 5%. Stem cell transplantation analyzed as a time-dependent variable had no impact on overall survival. However, patients not achieving CR had a 31% survival rate after stem cell transplantation. Childhood AML with chromosome 7 aberrations represents a heterogeneous group of disorders with additional cytogenetic aberrations having a major prognostic impact which should be reflected in future risk-group stratification.

Fluorescence in situ hybridization studies using BAC clones of the EVI1 locus in hematological malignancies with 3q rearrangements

Chromosomal rearrangements involving 3q26 are a recurrent aberration in malignant myeloid disorders. Several of these rearrangements involve the EVI1 oncogene or its surrounding sequences and are associated with a poor prognosis. Fluorescence in situ hybridization (FISH) studies using bacterial artificial chromosome (BAC) clones were conducted to determine whether the EVI1 locus was rearranged in nine patients with hematological malignancies carrying 3q abnormalities. A dual-color probe was constructed with nine BACs; centromeric clones covering 1 Mb and including the EVI1 gene were labeled with a red fluorescent dye and telomeric clones covering 1 Mb were labeled with a green fluorescent dye. Two patients showed normal copies of the EVI1 locus, four patients showed one EVI1 locus rearranged (in all of them the breakpoint on 3q26 was telomeric to EVI1), one patient showed one copy of the EVI1 locus translocated to another chromosome, one patient showed one copy of the EVI1 locus rearranged and the other copy translocated, and one patient showed one extra copy of the EVI1 locus. In four cases, FISH studies using the EVI1 clones detected different 3q abnormalities not previously found by conventional cytogenetics. FISH analysis with BAC clones was a useful tool for identifying the chromosome breakpoints affecting the EVI1 locus in patients with 3q26 rearrangements.