A short-term chemosensitivity test with different labeled precursors of DNA or protein synthesis: Correlation with clinical response

Blood or bone marrow samples from 15 patients with newly diagnosed acute myeloblastic leukemia undergoing remission induction treatment with daunorubicin, cytosine-arabinoside and 6-thioguanine were tested in vitro. Leukemic cells were incubated for 24 h at 37 degrees C with or without the drugs alone or in combination. A 3-h pulse with labelled precursors of DNA synthesis (3H-thymidine) or protein synthesis (3H-leucine) was then given separately. In vitro growth, expressed as the percentage ratio between labeled precursor uptake in treated cells and in control cells, was compared with the clinical results obtained. Three patients were not considered evaluable (death occurred too early), 8 had a complete response (CR), and 4 were disease resistant to chemotherapy. Leukemic cells of resistant-disease patients showed a significantly lower growth inhibition than cells taken from CR patients, with each drug alone or in combination, when measured with thymidine. Inhibition of leucine uptake was not related to the clinical outcome.