Assessment of DNA Damage in Some Acute Lymphoblastic Leukemia Iraqi Patients Using the Comet Assay

Abstract

This study investigates genomic damage in peripheral lymphocytes from patients with Acute Lymphoblastic leukemia. As a measure for genomic damage, the comet assay (single-cell gel electrophoresis) was applied. The study was carried out on fifty Iraqi patients ( 34 Male, 16 Female) , aged 2-70 years with Acute Lymphoblastic Leukemia (ALL) . These samples included 20 pretreatment (aged 7-70 years) , 15 relapsed (aged 9-40 years) and 15 under treatment (aged 2-57 years) , compared with 50 apparently healthy normal individuals collected randomly from population living in Baghdad ( aged 3 - 75 years). Patients were treated with nine drugs, which included vincristine , methotrexate, cytosar-U , L-asparaginase , etoposide, , dexamethasone (decadron) , indoxan and steroids. To quantify the DNA damage, three different comet parameters were evaluated , the tail length , % DNA mean in tail and the tail moment .It was found by the comet assay that the tail length (Mean ± SE) for Acute Lymphoblastic Leukemia(ALL) patients (pre treatment, relapse and under treatment the chemotherapy) and controls were 4.77±0.95 px , 20.36±1.86 px ,7.54 ±2.74px and 2.95 ±0. 44px , respectively . There was a significant increase between Acute Lymphoblastic Leukemia patients and controls for mean tail length (P < 0.01).The average damage (percentage of DNA) in the tail region of the comet (Mean ±SE)of Acute Lymphoblastic Leukemia )pre treatment , relapse and post treatment of the chemotherapy) and controls were 0.062 ± 0.036% , 0.121+0.0122% , 0.159±0.067% and 0.017±0.0055%, respectively. There was a significant increase between ALL patients and controls for % DNA mean in tail (P < 0.01). DNA damage were statistically significantly higher (P< 0.01) in case patients (pre treatment, relapse and post treatment of chemotherapy) for tail moment (Mean ± SE)were 0.00040 ± 9.4 E-05, 0.48 ± 0.086 and 0.117 ±0.054, respectively than in control subjects 0.000142 ± 4.6E-05. In addition, the results of comet assay are affected by for gender when compared with the groups studied . Despite their limitations, present results confirm the usefulness of the comet assay as a sensitive biomarker of exposure that enables rapid and simple detection of primary DNA damage in peripheral blood leukocytes of ALL patients. The comet assay provides a powerful technique for the routine detection of critical DNA lesions produced after the administration of antineoplastic drugs in clinical settings. These results , emphasize the need to further optimize the current therapy for reducing the degree of genomic damage.