Identification of drug-resistant myeloid leukemic cells by measurement of DNA content, nuclear area, and detection of P-glycoprotein

Abstract

BACKGROUND. This study was designed to evaluate the significance of aneuploidy in DNA ploidy, nuclear area, and expression of P-glycoprotein (P-GP) in differentiating drug-resistant myeloid leukemic cells (DRMLC) from drug-sensitive myeloid leukemic cells. METHODS. Bone marrow aspirates from 28 myeloid leukemic patients were fixed in 95% ethanol solution and stained using the Papanicolaou method. The nuclear area and DNA content were measured. An immunohistochemical study was performed using monoclonal antibody (JSB-1) directed against P-GP. RESULTS. Leukemic cell morphology changed once or twice after the diagnosis of acute myeloid leukemia (AML), blastic crisis (BC) of chronic myeloid leukemia, or chronic neutrophilic leukemia. DRMLC showed severe atypia and were morphologically distinguishable from normal myeloblasts, promyelocytes, and drug-sensitive leukemic cells at the diagnosis of AML or BC. The mean nuclear index (NI) and DNA index (DI) of DRMLC were significantly larger than those of drug-sensitive leukemic cells of AML or BC. The frequency of aneuploidy and P-GP expression was 9.1% and 4.5%, respectively, at the diagnosis of AML or BC, and 92.8% and 28.5%, respectively, for resistant disease. The incidence of heterogeneity in DNA ploidy was 86.3%. DI and NI values larger than 1.2 and the expression of P-GP are significant indications of DRMLC. Cancer 1996; 77:878-87. 0 1996 American Cancer Society. KEYWORDS Papanicolaou stain, nuclear area, DNA aneuploidy, P-glycoprotein, drug-resistant myeloid leukemic cell, malignant progression. dvances in chemotherapy and supportive care have significantly im-A proved the prognosis of patients with myeloid leukemia. The majority of patients, however, still relapse and finally succumb to resistant leukemia. Biochemical drug resistance present from the outset in leukemic cells or arising by somatic mutation is thought to be the major cause of failure of chemotherapy in these cancers. ' A variety of new drugs or novel applications and dose ranges of established agents have been explored in clinical Phase 1/11 studies. The attempt to deduce from these reports the most effective single agent or combination regimen, however, reveals uncertainty and confusion in view of the significant differences in the described response rates. These controversial results are most probably caused by the selection of patients and by different criteria rendering patients eligible for the respective It has been shown that the duration of the first remission21-26 or an unfavorable kary~type"*'~ have prognostic significance in acute myeloid leukemia. However, it is not possible to estimate the individual prognosis of every patient by these criteria. refractory anemia with excess of blasts in transformation; CMMoL chronic myelomanoqtic leukemia. CONCLUSIONS.Percentage of blast (BI) represents the ratio of leukemic cells in our papanieolaou stained preparations at the diagnosis of acute myeloid leukemia or blastic crisis or drug-resistan! myeloid leukemic cells thai proliferated in the bon...