Abstract
We showed that in childhood common acute lymphoblastic leukemia (c-ALL), 51 nucleotidase (5′NT) positive cases have a poorer prognosis than 5′NT negative cases. This might be due to the breakdown of the cytotoxic nucleotides of 6-mercaptopurine (6-MP) by high cytoplasmic 5′NT activities. Alternatively, ccto 5′NT can provide purine requirements of the purine salvage pathway and therefore rescue cells from a blockage of purine de novo synthesis by 6-MP and/or methotrexate. To test these hypotheses we need to determine the relation between these enzymes and drug sensitivity. We have adapted the MTT assay, which has only been reported on in studies dealing with established cell lines, to assess the chemosensitivity of cells obtained directly from patients. The assay is based on the reduction of MTT to formazan by living but not by dead cells. Formazan production is quantitated automatically with a microplate spectrophotometer. Incubation of ALL cells with 6-MP (4-125 μg/ml) and 6-thioguanine (1.6-50 μg/ml) for 2-4 days resulted in dose-response curves covering the range from 0% to 100%; cell survival. Comparison of the MTT assay with a dye exclusion assay in 10 patients with ALL demonstrated an identical success rate and comparable dose-response curves for both assays. Because automated quantitation of the chemosensitivity of leukemic cell samples involving about 80 drug concentrations takes only a few minutes with the MTT assay, this assay is a rapid, efficient, and objective method of measuring sensitivity to purine antagonists in ALL patients.
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Pieters, R., Huismans, D., Leyva, A. et al. 116 SENSITIVITY TO PURINE ANTAGONISTS IN CHILDHOOD LEUKEMIA ASSESSED BY THE AUTOMATED MTT-ASSAY. Pediatr Res 24, 130 (1988). https://doi.org/10.1203/00006450-198807000-00140
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DOI: https://doi.org/10.1203/00006450-198807000-00140