Impact of Wilms' tumor 1 expression on outcome of patients undergoing allogeneic stem cell transplantation for AML

The monitoring of the minimal residual disease by Wilms' tumor 1 expression (MRD^WT1) is a standardized test, which can be used in over 80% of patients with AML. To investigate the prognostic value of MRD^WT1 in patients undergoing allogeneic stem cell transplantation (allo-SCT) for AML, MRD^WT1 was monitored 3 months after transplantation in 139 patients. MRD^WT1 positivity did not lead to any therapeutic intervention. Median follow-up was 39.3 (6.4-99.8) months. Patients with positive MRD^WT1 at 3 months experienced more often post-transplant relapse (27/30, 90%) than those with negative MRD^WT1 (16/109, 14.7%) (P<0.0001). Similarly, a shorter 3-year event-free survival (EFS) was observed in MRD^WT1-positive patients (10% vs 72.3% in MRD^WT1-negative patients, P<0.0001). The correlation between relapse and MRD^WT1 was stronger in blood than in bone marrow samples. Multivariate analysis confirmed the detrimental role of 3-month positive MRD^WT1 for relapse (hazard ratio (HR): 15.42; 95% confidence interval (CI): 7.53-31.59; P<0.0001) and EFS (HR: 10.71; 95% CI: 5.41-21.21; P<0.0001). Interestingly, 3-month chimerism was less predictive of relapse than positive MRD^WT1. In conclusion, our results demonstrate the usefulness of peripheral blood MRD^WT1 monitoring in identifying very high-risk patients, who could benefit from an early preemptive treatment, and those who do not need such an intervention.

Copy-number analysis identified new prognostic marker in acute myeloid leukemia

Recent advances in genomic technologies have revolutionized acute myeloid leukemia (AML) understanding by identifying potential novel actionable genomic alterations. Consequently, current risk stratification at diagnosis not only relies on cytogenetics, but also on the inclusion of several of these abnormalities. Despite this progress, AML remains a heterogeneous and complex malignancy with variable response to current therapy. Although copy-number alterations (CNAs) are accepted prognostic markers in cancers, large-scale genomic studies aiming at identifying specific prognostic CNA-based markers in AML are still lacking. Using 367 AML, we identified four recurrent CNA on chromosomes 11 and 21 that predicted outcome even after adjusting for standard prognostic risk factors and potentially delineated two new subclasses of AML with poor prognosis. ERG amplification, the most frequent CNA, was related to cytarabine resistance, a cornerstone drug of AML therapy. These findings were further validated in The Cancer Genome Atlas data. Our results demonstrate that specific CNA are of independent prognostic relevance, and provide new molecular information into the genomic basis of AML and cytarabine response. Finally, these CNA identified two potential novel risk groups of AML, which when confirmed prospectively, may improve the clinical risk stratification and potentially the AML outcome.

Waved aCGH: to smooth or not to smooth

Array-based comparative genomic hybridization (aCGH) is a powerful tool to detect genomic imbalances in the human genome. The analysis of aCGH data sets has revealed the existence of a widespread technical artifact termed as ‘waves’, characterized by an undulating data profile along the chromosome. Here, we describe the development of a novel noise-reduction algorithm, waves aCGH correction algorithm (WACA), based on GC content and fragment size correction. WACA efficiently removes the wave artifact, thereby greatly improving the accuracy of aCGH data analysis. We describe the application of WACA to both real and simulated aCGH data sets, and demonstrate that our algorithm, by systematically correcting for all known sources of bias, is a significant improvement on existing aCGH noise reduction algorithms. WACA and associated files are freely available as Supplementary Data.

[Beta(o)/beta(o) thalassemia with a mild phenotype]

We report the case of a 30 years old patient of Algerian origin, presenting a beta-thalassemia major with a phenotype of intermediate severity. Its genotype is beta(o)/beta(o), leading to a complete absence of beta-globin synthesis. This genotype is usually responsible for major clinical complications and a severe anaemia requiring regular transfusions. However, the patient presents with a mild form of the disease and a moderate relatively well tolerated anaemia. This phenotype was found related to a high level of synthesis of foetal haemoglobin, dependent most probably on an homozygous state for the polymorphism (XmnI -158, C>T) in the promoter of the Ggamma gene. This observation shows that it is important to keep in mind that beta-thalassemia major may have a mild or intermediate phenotype because of polymorphisms of the beta locus.