High TOP2B/TOP2A expression ratio at diagnosis correlates with favourable outcome for standard chemotherapy in acute myeloid leukaemia

Background: Cytosine arabinoside-based chemotherapy coupled with anthracycline is currently the first-line treatment for acute myeloid leukaemia (AML), but diverse responses to the regimen constitute obstacles to successful treatment. Therefore, outcome prediction to chemotherapy at diagnosis is believed to be a critical consideration. Methods: The mRNA expression of 12 genes closely involved in the actions of cytosine arabinoside and anthracycline was evaluated by real-time reverse transcriptase PCR (RT-PCR), in 54 diagnostic bone marrow specimens of M2-subtype AML. Results: Low expression levels of ribonucleotide reductase M2 (RRM2) and high expression levels of topoisomerase 2 beta (TOP2B) were correlated with longer survival in a univariate analysis. Another interesting finding is that high ratios of TOP2B/RRM2 and TOP2B/TOP2 alpha (TOP2A) in a combined analysis were also shown to have a prognostic impact for longer survival with improved accuracy. Among the four markers, when adjusted for the influence of other clinical factors in multivariate analysis, the TOP2B/TOP2A ratio was significantly correlated with treatment outcomes; patients with high ratios trended toward longer disease-free survival (HR, 0.24; P=0.002) and overall survival (HR, 0.29; P=0.005). Conclusion: Genes with distinct expression profiles such as TOP2B/TOP2A expression ratio at diagnosis can be employed for outcome prediction after the treatment with standard regimens in AML patients with M2 subtype.