The Co-expression Of AML1-ETO Fusion Gene And Isoform AML1-ETO9a In Patients Of Acute Myeloid Leukemia And Its Clinical Significance

Objective To quantify the expression level of AML1-ETO9a isoform(AE9a)and AML1-ETO fusion gene(AE)in patients of acute myeloid leukemia (AML) and their possible clinical significance on complete remission rate,relapse rate,survival rate and prognosis.Methods 30 bone marrow samples from newly diagnosed AML-M2 patients who co-expressed both AE9a and AE were firstly selected by using the qualitative reverse transcription-polymerase chain reaction(RQ-PCR). The real time quantitative PCR with Taqman probes was then designed to quantitatively measure the expression level of AE9a and AE in these samples,respectively. The varying levels and the relative correlation between AE9a and AE were monitored during follow-up on 19 AML patients'bone marrow samples collected before and after treatment in complete remission or in relapse. Based on the clinical data of these patients,the possible clinical significance of expression of AE9a/AE was proposed. The difference in complete remission rate,relapse rate,survival rate between the AE9a positive and negative patients were also analyzed on 92 newly diagnosed AML-M2 patients.Result 1. (1) The percentages of the expression level of AE9a and AE in the overall expression value were measured by QRT-PCR in 30 newly diagnosed patients'samples. The median percentages of AE9a and AE were18.16%and 81.84%respectively, indicating a lower expression level of AE9a than that of AE(P<0.05). (2) A positive correlation between the expression level of AE9a and AE was shown in many bone marrow samples from 19 patients during the follow-up by QRT-PCR,and the correlation coefficient is 0.900(P<0.01).2. (1) The expression level of both AE9a and AE decreased in 16 newly diagnosed patients'samples after the first course of standard conventional chemotherapy. The percentage of the expression level of AE9a out of the overall expressed species declined in 11 (68.75%) patients,and the same occurred for AE in 5 (31.25%) patients. The complete remission rate was 81.82%(9/11)in 11 patients after first therapy, and 20.00%(1/5)in 5 patients (P<0.05),suggesting a higher CR rate in the 11 patients than that of the 5 ones .(2) The median percentage of the expression level of AE9a in overall expression was 53.09% in 12 patients'bone marrow samples who arrived complete remission second times after chemotherapy,indicating a higher proportion of the expression level of AE9a in total than that of the newly diagnosed samples of the 12 patients which was 18.16% (P<0.05). (3) The percentage of the expression level of AE9a in overall expression rose in all of the 5 relapsing cases while the expression of AE9a and AE both rising (P<0.05). 3. (1) 50 of 92 (54.35%) newly diagnosed AML-M2 patients expressed AE9a. The complete remission rate in AE9a positive group and negative group were 42.00% and 54.76% respectively after one course of standard conventional chemotherapy. No evident discrepancy in the CR rate has been found between these two groups (P>0.05). (2) The relapse rates of the AE9a positive group and negative group were 36.84%(14/38)and 62.06%(18/29)respectively in 67 newly diagnosed patients after 3 months in complete remission. The AE9a positive group had a lower relapse rate than the negative one (P<0.05). (3) In 32 relapsing patients during the follow-up for more than 3 months,the interval of first remission in AE9a positive group is not statistically different from the negative one ( P>0.05). The median remission time of the both groups was 10.5 months. 4. (1) 50%(7/14) of the relapsed patients with positive AE9a could not achieve complete remission after 2 or 3 courses'standard conventional chemotherapy,while only 3 in 18 (17%) patients with negative AE9a had the similar results (P<0.05),suggesting a worse prognosis in AE9a positive patients. (2) Based on survival analysis on 63 patients,the median survival time 22.26 months in 38 AE9a positive cases was significantly shorter than 76 months in the 25 negative cases (P<0.01). Conclusion AE9a and AE co-expressed in most of the patients of AML with t(8;21) translocation. The expression level of AE9a was lower than that of AE in a single patient. Moreover,the expression level of these two isoforms in a single patient had a distinctly positive correlation. AE9a played an important role in the development and clinical outcome of AML,suggesting that AE9a positive cells were probably the sources of the persistence and relapse in AML. Although the complete remission rate and the remission period in AE9a positive and negative groups showed no statistical difference,and the relapse rate of patients with positive AE9a in this cohort was somehow lower than that of negative cases. However,the AE9a positive group could hardly achieve second complete remission once relapsed,whereas the AE9a negative group could obtain remission after relapse for many times. AE9a positive group had a distinctly lower survival rate than that of the negative group,and had a significantly shorter median survival time than that of AE9a negative group,showing a worse prognosis.