Abstract
Introduction: Despite progress in understanding acute myeloid leukemia (AML) biology, most patients (pts) still have a poor prognosis. MicroRNAs (miR) have emerged as important players in AML biology. High expression of miR-181a has been associated with improved outcomes in AML pts. Mature miR-181a originates from two precursor molecules pri-miR-181a-1 & pri-miR-181a-2 which have been associated with distinct biological features & are derived from chromosome 1q32.1 & 9q33.3, respectively. Allogeneic stem cell transplantation (HCT) offers a potential curative treatment option for AML pts. With the introduction of reduced intensity conditioning (RIC) regimens, this procedure also became available for older or comorbid individuals. Here, we measured pri-miR-181a-1 & pri-miR-181a-2 and analyzed their impact on survival in RIC-HCT treated AML pts.
Patients and Methods: 139 AML pts (median age 64 years [y], range 22-75y) who received RIC-HCT between 2000 and 2012 with pretreatment material available were included in our analysis. The conditioning regimens were based on Fludarabine 30mg/m2 on day -4 till -1 followed by 2 Gy total body irradiation. Disease status at RIC-HCT was first (n=79, 57%) or second complete remission (CR; n=23, 16%) or more advanced disease (n=37, 27%). Donors were human leukocyte antigen (HLA) matched related (n=22, 16%) or HLA matched (n=83, 60%) or mismatched (n=34, 24%) unrelated. The mutation status of the NPM1 & CEBPA genes & the FLT3-ITD status were assessed at diagnosis. Pts were grouped according to the European LeukemiaNet (ELN) classification in favorable (26%), intermediate-I (26%), intermediate-II (21%) or adverse (27%). Pri-miR-181a-1 & pri-miR-181a-2 expressions were measured by RT-PCR, normalized to 18S & the median normalized gene expression was used to define high & low expressers. Median follow up was 4.3y for pts alive.
Results: The expression of both precursor molecules correlated well (Pearson Correlation 0.78), but 23% had a discordant expression status. At diagnosis pts with high pri-miR-181a-1 expression were younger at time of RIC-HCT (P=.01), had higher % peripheral blood (P=.05) & bone marrow (P=.04) blasts & by trend fewer NPM1 mutations (P=.054). Pts with high pri-miR-181a-2 expression had higher white blood count (WBC, P=.04). Combining the expression status information for both precursors, pts with high pri-miR-181a-1 and/or high pri-miR-181a-2 expression were younger at time of RIC-HCT (P=.04).Pts with high pri-miR-181a-1 and/or high pri-miR-181a-2 expression had longer overall survival (OS; P=.004, Figure 1) & event-free survival (EFS; P=.002). Interestingly a strong impact on outcome was observed in the ELN favorable group (OS: P=.001 & EFS: P=.008, Figure 1) and in the ELN intermediate II group (OS: P<.001 & EFS: P<.001, Figure 1), while no significant impact of high pri-miR-181a-1 and/or high pri-miR-181a-2 expression on outcome was observed in the intermediate I & adverse ELN groups.In multivariate analyses pri-miR-181a-1 and/or high pri-miR-181a-2 expression status remained a strong prognostic factor for OS (hazard ratio [HR] 0.53; 95% confidence interval [CI] 0.36-0.79; P=.002) and EFS (HR 0.52 CI 0.36-0.75; P<.001) in the entire group of pts.
Conclusion: In conclusion, pri-miR-181a-1 & pri-miR-181a-2 expression correlated well, but were not fully concordant & associated with distinct clinical characteristics. The expression status of pri-miR-181a-1 & pri-miR-181a-2 at diagnosis is a strong independent prognostic factor for AML pts undergoing RIC-HCT. The prognostic impact was strongest in the ELN favorable and intermediate II groups. Pri-miR-181a-1 & pri-miR-181a-2 expression levels may contribute to improved risk stratification for AML pts undergoing RIC-HCT, refining the ELN favorable and intermediate II group. Furthermore, pretherapeutic miR elevation either pharmacologically or by miR-replacement therapies may improve outcomes in AML pts undergoing RIC-HCT.
Lange:Novartis: Consultancy, Honoraria, Research Funding.
