AN IN-VITRO STUDY OF BLAST CELL-METABOLISM IN ACUTE MYELOID-LEUKEMIA USING THE MTT ASSAY

We have utilized the MTT assay to measure the metabolic activity of ce lls from the bone marrow of 55 patients with acute myeloid leukaemia ( AML), myelodysplastic syndrome (MDS) and non-clonal disease. Doubling dilutions of cells were exposed to MTT for 3-4 h. The mean optical den sity of the formazan produced by each cell dilution was plotted and th e gradient of the line produced was calculated, higher gradients indic ating more metabolically active cells. Results showed that the median activity of mononuclear cells from seven patients with non-clonal dise ase was 0.202 (range 0.175-0.253); blast cells from 27 patients with d e novo AML had a median activity of 0.187 (range 0.079-0.345) and 13 p atients with MDS a median of 0.155 (range 0.062-0.311). Seven assays o n mononuclear cells from five patients in remission had a median activ ity of 0.203 (range 0.190-0.248), indicating no significant difference between these and normal patients. There was no correlation between t he metabolic activity of cells when compared with their proliferative capacity, cell size and expression of P-glycoprotein. Following exposu re of the AML patients' blast cells to the anthracyclines, cytosine ar abinoside, 6-thioguanine and etoposide, cell survival was measured usi ng the MTT assay. While there was no correlation between the in vitro sensitivity of these cells to the anthracyclines or etoposide, less me tabolically active cells showed significantly greater sensitivity to 6 -thioguanine. Conversely, the more active cells appeared to be more se nsitive to cytosine arabinoside. Patients whose blasts cells showed hi gher metabolic activity appeared to achieve remission and had a longer mean survival time. Therefore, by using a simple technique we were ab le to establish that some patients were more likely to respond to cert ain cytotoxic regimes. Our preliminary study reflected the multifactor ial nature of clinical response in AML and MDS, so providing further i nformation on the relationship between cellular metabolic activity and treatment failure. Copyright (C) 1996 Elsevier Science Ltd.