2603

LOW-DOSE METHOTREXATE COMBINED WITH GM-CSF INDUCE DIFFERENTIATION OF MONOCYTIC LEUKEMIC CELL LINE (U937) IN VITRO

Chen J, Gu LJ, Ying DM

Dept. of Hematology/Oncology, Xinhua Hospital, Shanghai

Children’s Medical Center, and Shanghai Second Medical University, Shanghai, China

Objective: To study the potential role of low-dose methotrexate in the treatment of monoblastic leukemia and to explore its usage in this area.

Methods: Using U937 cell line as a model. CD14 was tested by flow cytometry. NBT was used to examine the degree of the differentiation. Telomerase PCR ELISA kit was used to tested the telemerase activity.

Results: After incubation with 20nM Methotrexate for 24,48,72 96hours, the size of the U937 cells increased, the ratio of the muclear/plasma gradually decreased, NBT reductive test became positive, and CD14 positive cells increased from 3% to 20% by flow cytometry analysis after 72 hours incubation. Treatment with 100u/ml GM-CSF alone failed to induce differentiation but together with lowdose methotrexated, resulted in 63% percent of differentiated cells after 72 hours incubation. During treated with methotrexated plus GM-CSF, using Telomerase PCR ELISA kit as a method, telomerase activity of U937 cells was showed from 2.11 (without any treatment) to 1.48, 0.77, 0.24 (after treatment for 24,48,72 respectively). The range of the decrease of telomerase activity was in proportion with the degree of differentiation, the cells differentiated completely without any telomerase activity after 72 hours incubation.

Conclusion: Monoblastic leukemia could be treated with low-dose methotrexate plus GM-CSF as the differentiation induction regimen.