Research On Prognosis Of Acute Myeloid Leukemia With AML1-ETO Gene Positive

Objective:Acute myeloid leukemia（AML） is a type of aggressive hematopoietic stem cell disorders with short onset time, rapid progression and poor prognosis and AML1-ETO fusion positive, in which, is a type of AML that is generally considered to have a good prognosis and longer survival time. However, outcomes of evaluation of survival of this type of AML varies greatly among patients and this has been reported number of times from different clinical studies, which suggests that there must be other factors also affect the survival of patients. Currently, AML patients with only AML1-ETO fusion positive （no other genetic mutations） usually lacks effective ways to evaluate their prognosis, however, the link with the AML-M2b subtype in FAB classification is close. Morever, DNA methylation of tumor suppressor genes has the potential to become an evaluation marker for prognosis. Among varies methylation detection techniques, methylation mass spectrometry analysis is an accurate, quantitative, high-throughput method with short turn around time. In this research, we aimed to investigate the clinical biological characteristics of Chinese AML patients with AML1-ETO fusion positive and analyze factors affecting prognosis. We have also measured methylation levels of 7 tumor suppressor gene in AML patients with AML1-ETO fusion positive by mass spectrometry, in an attempt to clarify prognostic differences and improve the accuracy of clinical outcome evaluation.Methods:The characteristics of morphology, immunology, cytogenetics, molecular biology, treatment and prognosis of 73 cases of AML1-ETO-positive-AML patients from January in 2006 to January in 2012 in our hospital were retrospectively analyzed, and prognostic factors were comprehensively evaluated by univariate and multivariate analysis. Then, prognostic factors and special bone marrow morphology are analyzed on AML patients with only AML1-ETO fusion positive. The methylation status of seven tumor suppressor genes, CDKN2B, GSTM1, PLK2, PRDX2, SFRP2, CDH1 and E YA4 were examined using mass spectrometry.22 cases of bone marrow samples of AML patients with AML1-ETO gene positive are retrospectively selected, and 10 normal donor bone marrow samples as a control.Results:Median survival time of 73 follow-up patients was 57 months.3-year expected overall survival（OS） rate was 60.3%,3-year expected relapse-free survival（RFS） rate was 52.0%. Univariate and multivariate analysis showed that within AML1-ETO-positive-AML patients, factors that affecting 3-year OS rate are: only t（8;21）（q22;q22）, only AML1-ETO positive, AML1-ETO continued negative, no more than 2 courses of getting remission and transplantation, whereas for 3-year RFS rate, AML1-ETO continued negative, no more than 2 courses of getting remission and transplantation are more important. However, in AML patients with only AMLl-ETO fusion positive, the statistically significant independent factors are only after treatment factors. Methylation mass spectrometry analysis of 7 tumor suppressor genes have showed that, the average methylation level of CDKN2B and EYA4 of AML1-ETO-positive-AML patients was significantly higher than these of the normal control, however the AML patients with only AML1-ETO gene positive did no have significant difference with these of patients with other genetic abnormalities. Poor prognostic patients with only AML1-ETO gene positive （no more than 36 months of survival time） are having significantly higher average methylation level on CDKN2B gene and SFRP2_CpG₁.2 site than that of good prognosis group and normal controls.Conclusion:Our study has shown that c-kit gene expression, other cytogenetic abnormalities, persistently positive detection of AML1-ETO gene, no more than 2 courses of getting remission or hematopoietic stem cell transplantation are the important independent factors of survival time for Chinese AML1-ETO-positive-AML patients. There is a certain correlation between patients with only AML1-ETO gene positive and abnormal myelocytes morphology in M2b subtype. However, only no more than 2 courses of getting remission and hematopoietic stem cell transplantation are the independent factors affecting survival time for AML patients with only AML1-ETO fusion positive, but neither can be used as the tool for prognosis evaluation before treatment. In contrast, our methylation mass spectrometry analysis has shown that the methylation level of CDKN2B gene and SFRP2_CpG₁.2 site may serve as a new maker to predict the prognosis of AML patients with only AML1-ETO fusion positive.