The Significance of Blast Multidrug Resistance Detection by Flow Cytometry in Diagnostics of Acute Leukemia

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Laboratorinė medicina. 2011,
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p. 65 -
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The Significance of Blast Multidrug Resistance Detection by Flow Cytometry in Diagnostics of Acute Leukemia

Miglė Janeliūnienė, Rėda Matuzevičienė, Zita Kučinskienė

 

Introduction. With a modern intensive chemotherapy most of the patients suf­fering from acute leukemia achieve a complete remission. However, some of them eventually relapse. One of the most significant reasons of relapse is a multi­drug resistance of leukemic cells. Trans­membrane pumps, such as p-gp and MRP1, ensuring the extrusion of cycto- toxic compounds from the cell play a very important role in the pathogenesis of the multidrug resistance. Increased expres­sion of these proteins on the blast cells influences a remission rate, its length and survival of acute leukemia patients. The main goal of this study was to evalu­ate the impact of flow cytometric assess­ment of the multidrug resistance in the diagnostic algorithm of acute leukemia. We compared p-gp and MRP1 expression and functional activity in blast and other blood cell populations. We also deter­mined the correlation between struc­tural and functional parameters of multidrug resistance. We searched for links between parameters of multidrug resisiance and the origin and immuno - phenotype of acute leukemia as well, as for their relation to the level of minimal resid­ual disease at different treatment time­points.

Material and methods. 30 paiients with acute leukemia were enrolled: 19 adults (10 females, 9 males, mean 52.2 years old) and 11 children (10 boys, 1 girl, mean 54.8 months old). For each pa­tient blast immunophenotype was estab­lished, multidrug resistance tests (p-gp ex­pression and functional test) were carried out and minimal residual disease level was evaluated at 5 treatment time-points.

Results. We found statistically reliable differences of multidrug resistance param­eters between blast, lymphocyte and mono­cyte populations (e.g., t-test result between blast and lymphocyte p-gp expression was 0.024). Although we did not find a correla­tion between p-gp and MRP1 expression and calcein assay results, correlation be­tween individual elements of structural re­sistance was rather strong (Pearson corre­lation coefficient was 0.830). Patients with acute lymphoblastic leukemia (ALL) had a lower MRP1 expression than patients with acute myeloid leukemia (AML), e.g. in case of T-ALL its mean fluorescence in­tensity was 78.667 and in case of AML with myelodysplastic features it was even 167.250. Calcein index (relation be­tween calcein value in blast and lympho­cyte populations) was also lower in ALL group, e.g. in case of B-ALL it was 0.930, and in case of AML it was 1.600. We found a statistically significant correla­tion between HLA-DR expression and calcein index and between CD7 and p-gp expression in case of AML, also between CD38 expression and calcein value in case of B-ALL. Statistically reliable links between calcein value and minimal resid­ual disease at any time-point of treat­ment were not proven. Corre i aiion was found beiween p-gp and MRP1 expres­sion and minimal residual disease at days 29-35 and 79-90.

We suggest that the determination of the multidrug resistance protein expres­sion could be introduced into routine di­agnostics of acute leukemia. The value of functional tests should be investigated further and several detection methods should be compared. As inhibitors of multidrug resistance appear in the mar­ket, laboratory tests of multidrug resis­tance inhibition would be useful.

Keywords: multidrug resistance, acute leukemia, flow cytometry, calcein, p-gp, MRP1.

 

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