t(6;9)(p22.3;q34) in a patient with refractory anemia with excess of blasts in transformation

Myelodysplastic syndrome with t(6;9)(p22;q34.1)/DEK-NUP214 better classified as acute myeloid leukemia? A multicenter study of 107 cases

t(6;9)(p22;q34.1)/DEK-NUP214 is a recurrent genetic abnormality that occurs in 1-2% of patients with acute myeloid leukemia (AML), and rarely in myelodysplastic syndrome (MDS). It has been suggested by others that all myeloid neoplasms with t(6;9)/DEK-NUP214 may be considered as AML, even when blast count is <20%. In this study, we compared the clinicopathologic features of 107 patients with myeloid neoplasms harboring t(6;9)/DEK-NUP214: 33 MDS and 74 AML. Compared with patients with AML, patients with MDS were older (p = 0.10), had a lower white blood cell count (p = 0.0017), a lower blast count in the peripheral blood (p < 0.0001) and bone marrow (p < 0.0001), a higher platelet count (p = 0.022), and a lower frequency of FLT3-ITD mutation (p = 0.01). In addition, basophilia was not a common feature in the patients of this cohort. Although there was no difference in overall survival between MDS and AML patients (p = 0.18) in the entire cohort, the survival curves did show a trend toward favorable survival in MDS patients. Multivariate analyses showed that initial diagnosis of MDS vs. AML and allogeneic hematopoietic stem cell transplantation were prognostic factors for survival of patients with t(6;9)/DEK-NUP214 (p = 0.008 and p < 0.0001, respectively). Our data suggest that MDS with t(6;9)/DEK-NUP214 is prognostically not equivalent to AML with t(6;9)/DEK-NUP214. These data also show that stem cell transplantation greatly improves the survival of MDS and AML patients with myeloid neoplasms associated with t(6;9)/DEK-NUP214.

Clinicopathologic and molecular characterization of myeloid neoplasms with isolated t(6;9)(p23;q34)

INTRODUCTION

The t(6;9)(p23;q34);DEK-NUP214 [t(6;9)] abnormality is found in 0.7-1.8% of patients with acute myeloid leukemia (AML) or myelodysplastic syndromes (MDS). FLT3-ITD mutations are detected in t(6;9) patients. The t(6;9) abnormality is associated with poor outcomes. We studied the clinicopathologic and molecular profiles of patients with AML/MDS carrying t(6;9).

METHODS

We collected clinical data of nine patients with AML/MDS with isolated t(6;9) (median age = 41 years; male/female = 4/5) and genotyped DNAs using whole exome, Sanger, and targeted sequencing.

RESULTS

Our cohort was characterized by frequent multilineage dysplasia (56%), absence of phospho-STAT3/STAT5 expression, presence of myeloid markers (CD13, CD33, CD34, CD117, HLA-DR) with an aberrant expression of CD7, and poor outcome (median survival of 20 months). Although basophilia has been described in association with t(6;9), we observed lack of marrow basophilia in our cohort. Molecularly, 83% (5/6) of patients with AML/MDS with t(6;9) were characterized by at least one somatic mutation. Among them, four patients showed multiple mutations. FLT3-ITD mutations were detected in 33% of patients (2/6); 80% (4/5) of mutant patients died even after hematopoietic stem cell transplantation.

CONCLUSION

Our data demonstrated that AML/MDS patients with t(6;9) have diverse molecular mutations regardless of the presence of FLT3 mutations, which may contribute to their poor survival outcomes.

6;9 translocation in myelodysplastic syndrome

The 6;9 chromosomal translocation [t(6;9)] is usually associated with acute nonlymphocytic leukemia, and carries a poor prognosis. We present a case of refractory anemia with excess of blasts (RAEB) accompanied by t(6;9). Review of the literature revealed an additional ten patients in which myelodysplastic syndrome (MDS) was associated with the chromosomal translocation 6;9. The patients tend to be younger then the average MDS patient and, unlike leukemia, in which this translocation is associated with a poor prognosis, these patients tend to have the same overall RAEB and refractory anemia with excess of blasts in transformation (RAEBt) prognosis. It is therefore possible that this chromosomal aberration should not be considered as an unfavorable prognostic factor in MDS.

Establishment of a novel human myeloid leukaemia cell line (FKH-1) with t(6;9)(p23;q34) and the expression of dek-can chimaeric transcript

Translocation t(6:9)(p23;q34), resulting in a dek-can gene fusion, is a recurrent chromosomal abnormality mainly associated with specific subtypes of acute myeloid leukaemia (AML) and myelodysplastic syndrome (MDS). Patients with this type of chromosomal change are usually young and their prognosis is poor. The role of fusion protein generated from dek-can chimaeric transcript on the leukaemogenesis oft(6;9) AML or MDS is as yet unknown. We have established the first permanent cell line (FKH-1) with t(6;9). derived from the peripheral blood of a patient with t(6:9) AML transformed from Philadelphia chromosome (Ph1)-negative chronic myelocytic leukaemia (CML). The FKH-1 expressed myelomonocytic markers and dek-can chimaeric transcript. In the presence of 10 ng/ml recombinant human granulocyte colony-stimulating factor (G-CSF), the cells doubled every 54 h and showed multilineage myeloid differentiation, resulting in heterogenous morphologies such as macrophages, basophils, eosinophils and neutrophils. Thus, this cell line may be derived from a pluripotent myeloid stem cell and should be a useful tool for biomolecular studies on the pathogenesis of t(6;9) myeloid malignancies which have rarely been investigated because of the lack of continuously proliferating cells.