Translocation (3;21) characterizes crises in myeloid stem cell disorders

Myelodysplastic syndrome/acute myeloid leukemia with t(3;21)(q26.2;q22) is commonly a therapy-related disease associated with poor outcome

The t(3;21)(q26.2;q22) translocation is rare in cases of myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML). We studied 17 patients with MDS/AML associated with t(3;21) and compared them with 17 patients with MDS associated with inv(3) (q21q26.2)/t(3;3)(q21;q26.2), because these entities share 3q26 locus abnormalities. The t(3;21) group included 9 men and 8 women, with a median age of 62 years (range, 13-81 years). One case was de novo AML and 16 cases were therapy-related, including 12 MDS (blasts, <15%) and 4 AML (blasts, 33%-50%). All patients had multilineage dysplasia, whereas none had thrombocytosis. Additional cytogenetic aberrations were identified in 12 cases, including -7/7q (n = 9) and a complex karyotype (n = 7). All patients died, with 1- and 2-year survival rates of 35% and 6%, respectively. Although multilineage dysplasia and frequent association with -7/7q were similar in both groups, MDS/AML cases associated with t(3;21) have a higher frequency of therapy-related disease and shorter survival times, suggesting that they are distinct from MDS/AML cases associated with inv(3)/t(3;3).

Role of the RUNX1-EVI1 fusion gene in leukemogenesis

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. RUNX1-EVI1 has oncogenic potentials through dominant-negative effect over wild-type RUNX1, inhibition of Jun kinase (JNK) pathway, stimulation of cell growth via AP-1, suppression of TGF-beta-mediated growth inhibition and repression of C/EBPalpha. Runx1-EVI1 heterozygous knock-in mice die in uteri due to central nervous system (CNS) hemorrhage and severe defects in definitive hematopoiesis as Runx1-/- mice do, indicating that RUNX1-EVI1 dominantly suppresses functions of wild-type RUNX1 in vivo. Acute myelogenous leukemia is induced in mice transplanted with bone marrow cells expressing RUNX1-EVI1, and a Runx1-EVI1 knock-in chimera mouse developed acute megakaryoblastic leukemia. These results suggest that RUNX1-EVI1 plays indispensable roles in leukemogenesis of t(3;21)-positive leukemia. Major leukemogenic effect of RUNX1-EVI1 is mainly through histone deacetyltransferase recruitment via C-terminal binding protein. Histone deacetyltransferase could be a target in molecular therapy of RUNX1-EVI1-expressing leukemia.

Acquired Robertsonian translocations are not rare events in acute leukemia and lymphoma

Robertsonian translocations are the most common constitutional structural abnormalities but are rarely reported as acquired aberrations in hematologic malignancies. The nonhomologous acrocentric rearrangements are designated as Robertsonian translocations, whereas the homologous acrocentric rearrangements are referred to as isochromosomes. Robertsonian rearrangements have the highest mutation rates of structural chromosome rearrangements based on surveys of newborns and spontaneous abortions. It would be expected that Robertsonian recombinations would be more common than suggested by the literature. A survey of the cytogenetics database from a single institution found 17 patients with acquired Robertsonian rearrangement and hematologic malignancies. This is combined with data from the literature for a total of 237 patients. All of the possible types of Robertsonian rearrangements have been reported in hematologic malignancies, with the i(13q), i(14q), and i(21q) accounting for nearly 60%. Complex karyotypic changes are seen in the majority of cases, corresponding with disease evolution. These karyotypes consistently show loss of chromosomes 5 and/or 7 in the myelocytic disorders, nonacrocentric isochromosomes, and centromeric breakage and reunion. However, nearly 25% of the acquired rearrangements were found as the sole abnormality or in addition to an established cytogenetic aberration. Most of these were the i(14q) with the myelodysplasia subtypes refractory anemia and chronic myelomonocytic leukemia.

21q22 balanced chromosome aberrations in therapy-related hematopoietic disorders: report from an international workshop

The International Workshop on the relationship between prior therapy and balanced chromosome aberrations in therapy-related myelodysplastic syndromes (t-MDS) and therapy-related acute leukemia (t-AL) identified 79 of 511 (15.5%) patients with balanced 21q22 translocations. Patients were treated for their primary disease, including solid tumors (56%), hematologic malignancy (43%), and juvenile rheumatoid arthritis (single case), by radiation therapy (5 patients), chemotherapy (36 patients), or combined-modality therapy (38 patients). 21q translocations involved common partner chromosomes in 81% of cases: t(8;21) (n = 44; 56%), t(3;21) (n = 16; 20%), and t(16;21) (n = 4; 5%). Translocations involving 15 other partner chromosomes were also documented with involvement of AML1(CBFA2/RUNX1), identifying a total of 23 different 21q22/AML1 translocations. The data analysis was carried out on the basis of five subsets of 21q22 cases, that is, t(8;21) with and without additional aberrations, t(3;21), t(16;21), and other 21q22 translocations. Dysplastic features were present in all 21q22 cases. Therapy-related acute myeloid leukemia (t-AML) at presentation was highest in t(8;21) (82%) and lowest in t(3;21) (37.5%) patients. Cumulative drug dose exposure scores for alkylating agents (AAs) and topoisomerase II inhibitors indicated that t(3;21) patients received the most intensive therapy among the five 21q22 subsets, and the median AA score for patients with secondary chromosome 7 aberrations was double the AA score for the entire 21q22 group. All five patients who received only radiation therapy had t(8;21) t-AML. The median latency and overall survival (OS) for 21q22 patients were 39 and 14 months (mo), compared to 26 and 8 mo for 11q23 patients, 22 and 28 mo for inv(16), 69 and 7 mo for Rare recurring aberrations, and 59 and 7 mo for Unique (nonrecurring) balanced aberration (latency P < or = 0.016 for all pairwise comparisons; OS, P < or = 0.018 for all pairwise comparisons). The percentages of 21q22 patients surviving 1 year, 2 years, and 5 years were 58%, 33%, and 18%, respectively. Noticeable differences were observed in median OS between 21q22 patients (n = 7) receiving transplant (BMT) (31 mo) compared to 21q22 patients who received intensive non-BMT therapy (n = 46) (17 mo); however, this was nonsignificant because of the small sample size (log-rank, P = 0.33). t-MDS/t-AML with balanced 21q22 aberrations was associated with prior exposure to radiation, epipodophyllotoxins, and anthracyclines, dysplastic morphologic features, multiple partner chromosomes, and longer latency periods when compared to 11q23 and inv(16) t-MDS/AML Workshop subgroups. In general, patients could be divided into two prognostic risk groups, those with t(8;21) (median OS, 19 mo) and those without t(8;21) (median OS, 7 mo) leukemia (log-rank, P = 0.0007).

A group of previously not recognized cytogenetic abnormalities in myeloid hematological malignancies

We have identified a group of previously not reported chromosome abnormalities related to myeloid hematological malignancies. Cases 1 and 2 were observed to have an additional i(4)(p10) as the sole anomaly with similar clinical features of myeloid disorders; that is, acute nonlymphocytic leukemia (ANLL-M2) and myelodysplastic syndrome (MDS)-refractory anemia with an excess of blasts in transformation, respectively. Fluorescence in situ hybridization studies with the use of a 4p-specific microdissection probe further confirmed the presence of an i(4)(p10) in these patients. Case 3 was diagnosed with ANLL-M1 and had an additional i(8)(p10) as the only change, also confirmed by a whole-chromosome painting procedure. In cases 4-6, deletions of 18q at breakpoints q12, q23, and q21 were identified as the sole anomaly in a myeloproliferative disorder (MPD), MPD, and MDS, respectively. X-autosome translocations other than t(X;10)(p11;p11) and t(X;11)(q13;q23) have not been reported as recurrent or primary changes in hematological disorders. In the present study, a t(X;9)(q26;q22) and t(X;5)(q13;q33) as the sole anomaly were found in cases 7 and 8, respectively. Both cases had the same diagnosis of MDS. Considering that trisomies 4 (+4) and 8 (+8) are common anomalies in MDS and ANLL, our findings strongly indicate that amplification of genes on 4p and 8p, but not on 4q and 8q, may play a crucial role in the pathogenesis of MDS and ANLL. In addition, genes on 18q12-23 and on Xq13-26 may be involved in the pathogenesis of myeloid disorders.

Gain of 9p in the pathogenesis of polycythemia vera

Polycythemia vera (PV) is a clonal stem cell disorder characterized by excessive erythrocyte production, resulting in absolute erythrocytosis. No specific structural chromosomal abnormalities have been reported in PV to date. We have observed two cases of PV with an extra i(9)(p10) as the sole anomaly, and FISH analysis using a 9p-specific chromosome microdissection probe showed that two other PV patients previously identified as having an add(18p) and an add(1p) as the primary changes actually carried a der(18)t(9;18)(p12;p11.2) and a der(1)t(1;9)(p12;p12), respectively. The same FISH assay was employed to evaluate domain signals on interphase cells of 15 more cases of PV with normal karyotypes and five normal controls. Two patients were observed with a significant increase in the percentage of cells with three domain signals. Our results strongly indicate that an additional i(9)(p10) is a new and recurrent primary chromosome anomaly in PV, and, in consideration of trisomy 9 being one of the most common anomalies in PV, amplification of a gene or genes on 9p, but not on 9q, may play a crucial role in the pathogenesis of PV.

Maternal balanced translocation leading to partial duplication of 4q and partial deletion of 1p in a son: cytogenetic and FISH studies using band-specific painting probes generated by chromosome microdissection

A 9-month-old boy with pre- and post-natal growth retardation, microcephaly, plagiocephaly, and several minor anomalies had the initial karyotype: 46,XY,der(1)t(1;?) (p36.1;?). Further analysis showed that the der(1) was derived from an unfavorable segregation of a maternal complex chromosome rearrangement, i.e., 46,XX,der(1)t(1;?) (p36.1;?), der(4)t(4;?)(q?;?). Whole chromosome fluorescence in situ hybridization (FISH) and chromosome microdissection were used to clarify the maternal karyotype as: 46,XX,der(1)t(1;4)(4qter-->4q33::1p36.13-->1qter),der( 4)t(1;4)inv(4)(4pter-->4q31.3::1p36.33-->1p36.13::4q33 -->4q31.3::1p36.33-->1pter). Therefore, the karyotype of the boy actually was 46,XY,der(1)t(1;4) (p36.13;q33). Clinical comparison of the patient's clinical findings showed similarities to individuals with partial del(1p) and dup(4q). To our knowledge the above cytogenetic abnormalities have not been described previously. This case further demonstrates the advantages of chromosome microdissection and FISH in the identification of anomalous chromosome regions and breakpoints.

Translocation (3;21)(q26;q22) in therapy-related myelodysplasia following drugs targeting DNA-topoisomerase II combined with alkylating agents, and in myeloproliferative disorders undergoing spontaneous leukemic transformation

Translocation (3;21)(q26;q22) has been observed only rarely in de novo myelodysplasia (MDS) and de novo acute myeloid leukemia (AML), but, including the two new cases in the present study, the aberration has now been identified in at least 10 cases of t-MDS or t-AML. All these 10 patients had previously received alkylating agents, in nine patients combined with a drug targeting at DNA-topoisomerase II (doxorubicin in eight cases). Eight of the ten patients presented with t-MDS. A further 20 patients with various myeloproliferative disorders and an identical t(3;21) have been reported. In these cases, t(3;21) was not related to any specific type of previous therapy but was associated with transformation from chronic stage disease to overt AML.