The t(8;21) AML1-ETO Fusion Gene Transcript Determination in Acute Myloid Leukemia

Recent studies of acute myeloid leukemia (AML) have demonstrated that several chromosomal rearrangements, and the molecular abnormalities they produce, identify patient subgroups with predictable clinical features and therapeutic responses. The translocation (8;21) (q22;q22) is one of the most frequently occurring translocations in AML. Conventional cytogentic analysis may be sometimes of limited usefulness, since it needs dividing cells in culture. Therefore, we identified the t(8;21) AML/ETO fusion gene transcript by reverse transcriptase polymerase chain reaction (RT-PCR) in AML patients. The resultant amplicon of the positive cases were further sequenced in order to confirm specificity of the seminested product. This was in a trial to determine the efficacy of this rearrangement as a predictor of treatment outcome and prognosis. They were 20 patients (10 males and 10 females) attending the Pediatricand Internal Medicine Oncology Units of Ain Shams University Hospitals. Their ages ranged from 18 months-56 years with a median value of 41 years. They were 12 newly diagnosed, 5 relapsed and 3 in remission. They were diagnosed morphologically as AML by examination of peripheral blood (PB) and bone marrow (BM) blasts, based on the standard FAB-morphologic and immunophenotypic criteria. Accordingly they were 6 cases (30%) Ml, 6 (30%) M2, 1 (5%) M3, 1 (5%) M4 and 1 (5%) M5. The incidence of the AML1 ETO hybrid gene in our studied group of patents was found to be 25% and within the M2 cases it was 36.4%. Among M2 positive cases, 2/4 had higher level of CD34 and CD19 expression and 3/4 had higher level of CD33 and HLA-DR. The study revealed that the age of the AML1/ETO hybrid gene positive cases was significantly lower compared to the negative (P 0.05), with a peak incidence less than 16 years. Also those positive cases were negative for risk factors and had a significantly lower TLC,PB and BM blast cell counts compared to the negative cases (P 0.05). Also patients harboring this hybrid gene showed good response to therapy and achieved complete remission. In conclusion, the quantitative RT-PCR ofAMLl -ETO mRNA and its semi-nested product DNA sequencing can provide a valuable tool to detect minimal residual disease, predict prognosis and treatment outcome.