De novo acute myeloid leukemia subtype-M4 with initial trisomy 8 and later acquired t(3;12)(q26;p12) leading to ETV6/MDS1/EVI1 fusion transcript expression: A case report

The t(3;12)(q26;p13) translocation is a recurrent chromosomal aberration observed in myeloid malignancies. The translocation results in the generation of the ETV6/myelodysplastic syndrome 1 (MDS1)/ectopic viral integration site 1 (EVI1) fusion gene. However, the present case report is the first to present this rearrangement in acute myelogeneous leukemia (AML)-M4. Notably, this case is the first report of AML-M4 with an initial trisomy 8 and secondary acquired t(3;12)(q26;p13). Cells harboring the t(3;12) translocation were found to exhibit a higher proliferative capacity than cells with pure trisomy 8, which is consistent with the role of the ETV6/MDS1/EVI1 fusion transcript in the development and progression of malignancy.


Introduction
Chromosomal abnormalities are extremely common in malignancy, including leukemia. Acute myelogeneous leukemia (AML) has a wide variety of chromosomal rearrangements that involve specific regions (1)(2)(3). The 3q26 region encodes two proteins involved in AML, ectopic viral integration site 1 (EVI1) and myelodysplastic syndrome 1 (MDS1). Expression of the EVI1 gene has been found to correlate with accelerated cell growth of murine embryonic stem cells. By contrast, the combined effect of these two genes has been observed to play a transcriptional transactivator role, resulting in reduced cell growth (4).
At present, mutual translocation of MDS1/EVI1 and ETV6 has been observed in only two AML-M4 cases; secondary to myelodysplastic syndrome (MDS) and in CML in blast crisis (9,10). In the current case report, we describe the molecular and cytogenetic characterization of a de novo AML-M4 case with t(3;12)(q26;p13) and trisomy 8. Written informed consent was obtained from the patient.

Case report
Patient characteristics. A 63-year old female was diagnosed with AML-M4 in October 2011 due to loss of weight and fever. Hematological parameters were as follows: White blood cell count, 5.43x10 9 cells/l; composed of 32.4% neutrophils, 24.4% lymphocytes, 38.5% monocytes, 0.61% eosinophils and 4.1% basophils. The platelet count was 1.32x10 9 cells/l and hemoglobin levels were 9.61 g/dl. Serum LDH levels were 1,121 U/l (normal, ≤480 U/l). No treatment had been administered prior to the test. In December 2011, the patient succumbed to unknown causes whilst under treatment with 100 mg Cytosar.

Methods
Chromosome analysis. Chromosome analysis using GTG-banding was performed according to standard procedures prior to chemotherapeutic treatment (11). A total of 20 metaphase cells derived from unstimulated bone marrow culture were analyzed. Karyotypes were described according to the International System for Human Cytogenetic Nomenclature (12).
Molecular cytogenetics. Fluorescence in situ hybridization (FISH), using the LSI BCR/ABL dual color dual fusion translocation and chromosome enumeration probes (CEPs) for chromosomes 3 and 12 (both Abbott Laboratories, Des Plaines, IL, USA), were applied according to the manufacturer's instructions, together with the TEL/AML1 translocation dual fusion probe (Qbiogene, MP Biomedicales, Santa Ana, CA, USA) (11). A total of 20 metaphase spreads were analyzed, each using a fluorescence microscope (Axio Imager Z1; Zeiss, Oberkochen, Germany) equipped with appropriate filter sets to discriminate between a maximum of five fluorochromes and the counterstain DAPI. Image capturing and processing were performed using an ISIS imaging system (MetaSystems, Altlußheim, Germany).

Discussion
The t(3;12)(q26;p13) translocation is a rare cytogenetic abnormality and has been previously reported in 45 cases of myeloid malignancies, including MDS, AML and CML (6). Two cases were described as AML-M4; one of them was initially a CML case with an additional trisomy 8 (6). To the best of our knowledge, the present case report is the first to observe a case of a AML-M4 with initial trisomy 8 and secondary developed t(3;12)(q26;p13).
The prognosis of AML with the t(3;12)(q26;p13) translocation has been reported to be poor, with a survival of only a few months. This is associated with treatment refractoriness and may reflect the fact that this AML is secondary to MDS with the presence of chromosome 7 abnormalities (4). This has a poor prognosis in general and is observed in the majority of t(3;12)(q26;p13) cases with chromosome 7 rearrangements. In three cases, resistance to therapy included treatment with allogeneic bone marrow transplantation (6,7,17). Notably, all three patients had an early relapse within a few months from transplantation (4).
The MDS1/EVI1 fusion generates a protein domain with homology to the positive regulatory domain of PRDI-BF1/Blimp-l, a transcriptional repressor of the interferon β gene and an inducer of genes that play a role in B-lymphocyte maturation (21).
In conclusion, the current case report presents a novel cytogenetic case of AML-M4 with initial trisomy 8 and a secondary t(3;12)(q26;p13), the latter having more proliferative capacity than cells with pure trisomy 8. The patient succumbed to unknown causes whilst under treatment. Therefore, we conclude that trisomy 8 with t(3;12)(q26;p13) has a negative prognosis.