FLOW CYTOMETRIC ANALYSIS OF GLUTATHIONE-S-TRANSFERASE-PI IN ACUTE-LEUKEMIA

Increased expression of glutathione-S-transferase isoenzyme pi (GST-pi ) may account for drug resistance and treatment failure in hematologic malignancies when alkylating agents like cyclophosphamide, chlorambuc il, busulfan and melphalan, or doxorubicin are used. We have studied t he expression of GST-pi in peripheral blood lymphocytes of healthy blo od donors, in peripheral and bone marrow lymphocytes/blasts of patient s with other diseases than hematologic malignancies, and of patients w ith acute leukemia by using flow cytometry. We studied bone marrow cel ls of 35 patients diagnosed as having acute leukemia at initial presen tation, 16 patients in the refractory stage, 20 in morphological remis sion and 15 controls. None of the samples obtained in remission contai ned more GST-pi-positive cells than the controls, whereas 51% of the s amples obtained at diagnosis and 56% of those obtained in the refracto ry stage were GST-pi-positive. The mean proportion of GST-pi-positive cells in the lymphocyte/blast cell gate of bone marrow cells of contro ls was 2.6% and of patients with acute leukemia studied at diagnosis 1 6.6%, respectively. We analyzed the samples also for P-glycoprotein ex pression. There was a significant positive association between GST-pi and P-glycoprotein expression in acute leukemia.