Myelodysplastic syndrome with translocation (8;21): a distinct myelodysplastic syndrome entity or M2-acute myeloid leukemia with extensive myeloid maturation?

Accelerated Phase of Atypical Chronic Myeloid Leukemia with Severe Disseminated Intravascular Coagulation at Initial Presentation

Patients with myelodysplastic syndrome/myeloproliferative neoplasm (MDS/MPN) are often asymptomatic and thus can remain undiagnosed until they become symptomatic due to progression to the accelerated phase (AP) or transformation to acute leukemia (leukemic transformation; LT). We herein report the case of a previously healthy 38-year-old man who had hyperleukocytosis with dysplastic myeloid precursor cells and severe disseminated intravascular coagulation. Hematopoietic recovery with features of atypical chronic myeloid leukemia (aCML) after induction chemotherapy was a diagnostic clue. Although rare, this case highlights the limitation of the diagnostic approach for aCML with AP or LT at the initial presentation.

VENTX induces expansion of primitive erythroid cells and contributes to the development of acute myeloid leukemia in mice

Homeobox genes are key regulators in normal and malignant hematopoiesis. The human Vent-like homeobox gene VENTX, a putative homolog of the Xenopus laevis Xvent-2 gene, was shown to be highly expressed in normal myeloid cells and in patients with acute myeloid leukemia. We now demonstrate that constitutive expression of VENTX suppresses expression of genes responsible for terminal erythroid differentiation in normal CD34⁺ stem and progenitor cells. Transplantation of bone marrow progenitor cells retrovirally engineered to express VENTX caused massive expansion of primitive erythroid cells and partly acute erythroleukemia in transplanted mice. The leukemogenic potential of VENTX was confirmed in the AML1-ETO transplantation model, as in contrast to AML1-ETO alone co-expression of AML1-ETO and VENTX induced acute myeloid leukemia, partly expressing erythroid markers, in all transplanted mice. VENTX was highly expressed in patients with primary human erythroleukemias and knockdown of VENTX in the erythroleukemic HEL cell line significantly blocked cell growth. In summary, these data indicate that VENTX is able to perturb erythroid differentiation and to contribute to myeloid leukemogenesis when co-expressed with appropriate AML oncogenes and point to its potential significance as a novel therapeutic target in AML.

Oncogenic pathways of AML1-ETO in acute myeloid leukemia: multifaceted manipulation of marrow maturation

The leukemic fusion protein AML1-ETO occurs frequently in human acute myeloid leukemia (AML) and has received much attention over the past decade. An initial model for its pathogenetic effects emphasized the conversion of a hematopoietic transcriptional activator, RUNX1 (or AML1), into a leukemogenic repressor which blocked myeloid differentiation at the level of target gene regulation. This view has been absorbed into a larger picture of AML1-ETO pathogenesis, encompassing dysregulation of hematopoietic stem cell homeostasis at several mechanistic levels. Recent reports have highlighted a multifaceted capacity of AML1-ETO directly to inhibit key hematopoietic transcription factors that function as tumor suppressors at several nodal points during hematopoietic differentiation. A new model is presented in which AML1-ETO coordinates expansion of the stem cell compartment with diminished lineage commitment and with genome instability.

Erythroid inhibition by the leukemic fusion AML1-ETO is associated with impaired acetylation of the major erythroid transcription factor GATA-1

Human acute myeloid leukemias with the t(8;21) translocation express the AML1-ETO fusion protein in the hematopoietic stem cell compartment and show impairment in erythroid differentiation. This clinical finding is reproduced in multiple murine and cell culture model systems in which AML1-ETO specifically interferes with erythroid maturation. Using purified normal human early hematopoietic progenitor cells, we find that AML1-ETO impedes the earliest discernable steps of erythroid lineage commitment. Correspondingly, GATA-1, a central transcriptional regulator of erythroid differentiation, undergoes repression by AML1-ETO in a nonconventional histone deacetylase-independent manner. In particular, GATA-1 acetylation by its transcriptional coactivator, p300/CBP, a critical regulatory step in programming erythroid development, is efficiently blocked by AML1-ETO. Fusion of a heterologous E1A coactivator recruitment module to GATA-1 overrides the inhibitory effects of AML1-ETO on GATA-1 acetylation and transactivation. Furthermore, the E1A-GATA-1 fusion, but not wild-type GATA-1, rescues erythroid lineage commitment in primary human progenitors expressing AML1-ETO. These results ascribe a novel repressive mechanism to AML1-ETO, blockade of GATA-1 acetylation, which correlates with its inhibitory effects on primary erythroid lineage commitment.

Clinical and cytogenetic features of 508 Chinese patients with myelodysplastic syndrome and comparison with those in Western countries

Myelodysplastic syndrome (MDS) is a clonal hematopoietic stem cell disorder characterized by ineffective hematopoiesis and leukemia progression. Racial differences may exist on clinical pictures and the molecular events leading to MDS, which are heterogeneous. To better define the clinical and cytogenetic features in Chinese patients, a retrospective multicentric study was performed in 508 MDS cases. Compared with Western countries, Chinese patients showed younger age (median: 49 vs 65-73 years), lower percentages of RARS (2.8 vs 6.6-15.3%), and CMML (5.2 vs 11.7-30.6%). Cytogenetically, among 367 cases with evaluable data, abnormal karyotypes were found in 136 cases, including 56 numerical and 80 structural changes. Incidences of single chromosome 5 and 7 abnormalities were lower than those in Western countries (2.2 vs 17.8-42.5%). However, complex cytogenetic aberrations and chromosome translocations were frequently observed and related to poor prognosis. Both multiple chromosome deletions and translocations were detected in advanced subtypes (RAEB and RAEB-T). Analysis of 200 cases revealed a higher incidence of hepatitis-B-virus infection than that in non-MDS population (21.00 vs 9.75%). This study further confirmed: (1) different genetic/environmental backgrounds between Asian and Western MDS populations; (2) a strong predictive value of cytogenetic abnormalities on disease outcome and involvement of genomic instability in leukemia clone development.

Classical and molecular cytogenetic abnormalities and outcome of childhood acute myeloid leukaemia: report from a referral centre in Israel

The incidence of cytogenetic abnormalities in childhood de novo acute myeloid leukaemia (AML) and its prognostic significance was assessed in an Israeli paediatric referral centre. Cytogenetic analysis was successful in 86 of 97 children (< 20 years of age) diagnosed between 1988 and 2002 with de novo AML. Fluorescence in situ hybridization analysis detected new information in 11 of them, leading to reassignment in cytogenetic group classification. The incidence of the various cytogenetic subgroups was as follows: normal - 9%; t(11q23) - 22%; t(8;21) - 13%; t(15;17) - 8%; inv(16) - 3.4%; abn(3q) - 4.6%; 7/7q-(sole or main) - 5.8%; del(9q)(sole) and +21(sole) - 4.6% each; t(8;16) - 2.3%; t(6;9), t(1;22), +8(sole) - 1.1% each; and miscellaneous - 18%. The overall survival (OS) and event-free survival (EFS) (4 years) for 94 patients treated with the modified Berlin-Frankfürt-Münster (BFM) AML protocols (non-irradiated) were 59.9% (SE = 5%) and 55.7% (SE = 5%), respectively, and for the favourable t(8;21), t(15;17) and inv(16), OS was 60% (SE = 15%), 83% (SE = 15%) and 100% respectively. For the normal group it was 62% (SE = 17%), miscellaneous 64% (SE = 12%), t(11q23) 44.6% (SE = 11%) and of the -7/7q-, del(9q)(sole) or t(6;9), none had survived at 4 years. The incidence of cytogenetic subgroups in the Israeli childhood AML population and their outcome were similar to other recently reported paediatric series. Cytogenetic abnormalities still carry clinical relevance for treatment stratification in the context of modern chemotherapy.

Philadelphia chromosome positive myelodysplastic syndrome and acute myeloid leukemia—retrospective study and review of literature

We conducted a retrospective study to define the significance of Philadelphia chromosome (Ph) in myelodysplastic syndrome and acute leukemia in the adults at this institution and the literature was reviewed. One hundred forty-eight cases of t(9;22)(q34;q11) were identified for the period September 1993 through August 2001. The presentation of 124 cases (84%) was that of typical CML in chronic phase. Nineteen cases (13%) presented as de novo ALL, two cases (1%) presented as de novo AML and three cases (2%) presented as myelodysplastic syndrome (MDS). The estimated incidences of t(9;22)(q34;q11) in ALL and AML are 21 and 0.6%, respectively. Ph+ AMLs are increasingly being reported with either M-BCR or m-BCR gene rearrangements, similar to those found with Ph+ ALL lending support to the notion that Ph+ AMLs are distinct entities and not merely blastic phases of undiagnosed CML. This is further supported by the existence of Ph+ MDS cases.

An activated receptor tyrosine kinase, TEL/PDGFbetaR, cooperates with AML1/ETO to induce acute myeloid leukemia in mice

The t(8;21)(q22;q22) translocation, occurring in 40% of patients with acute myeloid leukemia (AML) of the FAB-M2 subtype (AML with maturation), results in expression of the RUNX1-CBF2T1 [AML1-ETO (AE)] fusion oncogene. AML/ETO may contribute to leukemogenesis by interacting with nuclear corepressor complexes that include histone deacetylases, which mediate the repression of target genes. However, expression of AE is not sufficient to transform primary hematopoietic cells or cause disease in animals, suggesting that additional mutations are required. Activating mutations in receptor tyrosine kinases (RTK) are present in at least 30% of patients with AML. To test the hypothesis that activating RTK mutations cooperate with AE to cause leukemia, we transplanted retrovirally transduced murine bone marrow coexpressing TEL-PDGFRB and AE into lethally irradiated syngeneic mice. These mice (19/19, 100%) developed AML resembling M2-AML that was transplantable in secondary recipients. In contrast, control mice coexpressing with TEL-PDGFRB and a DNA-binding-mutant of AE developed a nontransplantable myeloproliferative disease identical to that induced by TEL-PDGFRB alone. We used this unique model of AML to test the efficacy of pharmacological inhibition of histone deacetylase activity by using trichostatin A and suberoylanilide hydroxamic acid alone or in combination with the tyrosine kinase inhibitor, imatinib mesylate. We found that although imatinib prolonged the survival of treated mice, histone deacetylase inhibitors provided no additional survival benefit. These data demonstrate that an activated RTK can cooperate with AE to cause AML in mice, and that this system can be used to evaluate novel therapeutic strategies.

Using fluorescence-activated cell sorting followed by fluorescence in situ hybridization to study lineage relationships: the 8;21 translocation is present in neutrophils but not monocytes in a patient with severe congenital neutropenia and a granulocyte colony-stimulating factor-responsive clonal abnormality

Severe congenital neutropenia (Kostmann syndrome) is a disorder that presents in the neonatal period, but predisposes to leukemia later in life. This report describes a 4-y-old female with a history of severe congenital neutropenia, who developed a clonal abnormality associated with the translocation (7;21;8) (q32;q22;q22) (AML-1/ETO). She had circulating peripheral blasts and bone marrow blast counts as high as 64% when she received recombinant granulocyte colony-stimulating factor (rG-CSF). Her marrow blasts decreased to 4-20% when rG-CSF was discontinued. Fluorescence in situ hybridization analysis was performed on bone marrow cell populations sorted by flow cytometry to determine which cell populations had the AML-1/ETO translocation. The translocation was found in mature neutrophils and blasts, but not in monocytes, lymphocytes or stem cells.

CONCLUSION

These findings suggest that the translocation occurred in a neutrophil progenitor, past the point in ontogeny where monocytes and neutrophils separate. The techniques described may be useful in understanding lineage relationships and leukemogenesis in other clonal abnormalities associated with myelodysplasia and leukemia.

Successful treatment with cyclosporin A of myelodysplastic syndrome with erythroid hypoplasia associated with t(6;8)(q15;q22)

We report a t(6;8)(q15;q22) in a patient with myelodysplastic syndrome (MDS) with erythroid hypoplasia. The patient was successfully treated with an immunosuppressive treatment with cyclosporin A, while the translocation was repeatedly detected as the sole anomaly with the percentages of positive cells ranging from 5% to 70%. To our knowledge, the t(6:8) has never been described in MDS.

Can t(8;21) oligoblastic leukemia be called a myelodysplastic syndrome?

The new World Health Organization (WHO) classification of hematologic malignancies has incorporated t(8;21) myelodysplastic syndromes (MDS) according to the French-American-British classification into the category of acute myeloid leukemia (AML) with t(8;21)(q22;q22), while our knowledge about clinicopathological features of t(8;21) oligoblastic leukemia is still limited. We present our experience with 12 patients meeting the FAB diagnostic criteria of MDS and having t(8;21), who were compared to 43 t(8;21) AML patients. The MDS and AML patients shared most hematomorphologic, immunophenotypic, and clinical features, whereas the differences lay along myeloid maturation. The MDS patients had higher percentages of circulating neutrophils and marrow myeloid cells beyond promyelocytes than the AML patients. The incidence of Auer rods in mature neutrophils in MDS was significantly higher than that in AML, and furthermore, the neutrophils in MDS more commonly contain t(8;21) than in AML. Our findings support the rationale for the WHO classification, and future studies on large patient populations should help clarify whether the spontaneous differentiation potential could be actively associated with a hematological manifestation of t(8;21) leukemias.