Semiquantitative RT-PCR evaluation of the MDR1 gene expression in patients with acute myeloid leukemia

Resistance to chemotherapy is one of the major obstacles to effective treatment in acute myeloid leukemia (AML). The most extensively studied protein involved in multidrug resistance (MDR) is the transmembrane glycoprotein P (P-gp), the product of the multidrug resistance gene 1 (MDR1). MDR1/P-gp overexpression is frequently observed in hematological malignancies, especially in acute leukemia, and has been reported to correlate with poor prognosis in acute myeloid leukemia (AML). The aim of this study was to evaluate the level of MDR1 gene expression in bone marrow and/or peripheral blood samples in 92 AML patients in relation to their prognosis. The analyzed group was stratified according to presence or absence of prognostically favorable aberrations (PFAs), such as t(15;17) with PML/RARalpha fusion gene, t(8;21) with AML1/ETO fusion gene or inv(16)/ t(16;16) with CBFbeta/MYH11 fusion gene. These prognostically favorable aberrations were detected by RT-PCR and/or standard cytogenetic techniques. MDR1 expression was detected by semiquantitative comparative RT-PCR using software-based evaluation. The levels of MDR1 expression in the bone marrow predicted induction of complete remission in the whole group of analyzed patients (P = 0.032). They were significantly lower in PFA negative patients who achieved complete remission compared to those who failed to achieve complete remission (P = 0.008). In PFA negative patients, MDR1 expression was higher when compared to PFA positive patients (P = 0.055). No such difference was found when analyzing peripheral blood samples. Our experiments showed no impact of MDR1 expression in bone marrow or peripheral blood cells on overall survival (P = 1.000 and P = 0.903 respectively). In summary, the present study shows the prognostic impact of MDR1 expression on induction of complete remission in AML patients. We confirmed that MDR1 overexpression is an unfavorable prognostic factor in AML, which may help to stratify the risk rate of PFA negative patients. In future studies, quantitative detection of MDR1 expression might be a valuable tool to predict prognosis in this patient subset.

Type J CBFbeta/MYH11 transcript in the M4Eo subtype of acute myeloid leukemia

Acute myeloid leukemia (AML) carrying inversion or translocation of chromosome 16 is usually associated with the FAB M4Eo morphological subtype and belongs to AMLs with a relatively favorable prognosis. At the molecular level, it is associated with a disease-specific fusion gene, CBFbeta/MYH11. Previously, 10 different types of CBFbeta/MYH11 fusion transcripts have been described in the literature, 7 of them are still known as unique cases. In the current study, peripheral blood and/or bone marrow samples from 265 AML patients were tested for the presence of the CBFbeta/MYH11 fusion using RT-PCR and 12 (4.5%) positive cases were identified. The most common type A CBFbeta/MYH11 transcript was confirmed in 11 patients. The transcript in the remaining one (a 71-year-old female) was different and sequence analysis allowed us to classify it as CBFbeta/MYH11 type J. In contrast to the first type J case previously reported from Australia, this patient exhibited a typical FAB M4Eo morphology. The evidence of the second case indicates that the type J breakage might be a non-random event within the MYH11 gene.

Aleukemic granulocytic sarcoma with AML1/ETO fusion gene expression and clonal T cell populations

We report a unique case of aleukemic granulocytic sarcoma of the neck, originally misdiagnosed as non-Hodgkin's lymphoma (NHL), though chloroma was also suspected due to a greenish macroscopic appearance and the presence of myeloid chloroacetate esterase (CAE)+ cells. The proof of clonal T cell receptor gamma chain (TcRgamma) gene rearrangements in the recurring tumor was deemed to confirm the initial diagnosis of T cell NHL. Altogether five distinct types of clonal TcRgamma gene rearrangements were found in the tumor, bone marrow and peripheral blood. Only retrospectively, using RT-PCR, did we detect the acute myeloid leukemia subset-specific fusion gene AML1/ETO in the frozen samples of the relapsed tumor, as well as in the otherwise unaffected bone marrow and peripheral blood (representing 'minimal initial disease' in the latter two samples). Simultaneous staining verified that the neoplastic CAE+ cells and CD45RO+ T cells were different populations.