Cytogenetic Effects Of Methotrexate And Cytarabine Alone And In Combination On G1 And G2 Cell Cycle Stages Of Leukemic MOLT-4 Cell Line In Vitro

Introduction: This study was performed to analyze chromosomal aletrations in G1 and G2 immortalizedMOLT-4 cell line following treatment with methotrexate (MTX) and cytarabine (ara-C) alone or incombination.
Material and Methods: MOLT-4 cells were cultured and manitained in RPMI-1640 supplementedwith fetal calf serum, antibiotics and L-gluthamine. Cells were treated with ara-C and MTX with aconcentration of 100ãmol/L at G1 and 50ãmol/L at G2. One and half hour prior to harvesting, cell wereexposed to colcemid. (0.1ãg/ml find concentration). Microscopic slides were prepared using standard1000).‚procedure. After staining with 5% Giemsa, metaphase was evaluated using light microscope(X 1000).
Results: Results indicate that ara-C and MTX, at a 100ãmol/L concentration, used for treatment of G1cells, increase the frequency of chromosomal type aberrations; although ara-C was more potent in aberrationinduction. The effect of combined treatment with ara-C and MTX on G1 cells was more than effect of eachdrug when used alone. The effect of these drugs on G2 cells with a concentration of 50ãmol/L was found to besignificantly different with that of controls (P<0.05). The frequency of chromatid type breaks induced by ara-Cwas considerably higher than MTX. When these drugs were used in combination, the frequency of aberrationsincreased dramatically.
Conclusion: Results indicate that both ara-C and MTX produce clastogenic effects on MOLT-4 cells.Combination treatment with ara-C and MTX has an additive effect on G1-cells. But a synergistic effect wasfound when they were used for treatment of G2-cells. The reason for hypersensitivity of G2-cells to chemicalsmight be due to shorter repair time of lesions induced in DNA, which are experessed as chromatid typeaberrations in the first mitosis.