Germ line DDX41 mutations define a unique subtype of myeloid neoplasms.

Germ line DDX41 variants have been implicated in late-onset myeloid neoplasms (MNs). Despite an increasing number of publications, many important features of DDX41-mutated MNs remain to be elucidated. Here we performed a comprehensive characterization of DDX41-mutated MNs, enrolling a total of 346 patients with DDX41 pathogenic/likely-pathogenic (P/LP) germ line variants and/or somatic mutations from 9082 MN patients, together with 525 first-degree relatives of DDX41-mutated and wild-type (WT) patients. P/LP DDX41 germ line variants explained ∼80% of known germ line predisposition to MNs in adults. These risk variants were 10-fold more enriched in Japanese MN cases (n = 4461) compared with the general population of Japan (n = 20 238). This enrichment of DDX41 risk alleles was much more prominent in male than female (20.7 vs 5.0). P/LP DDX41 variants conferred a large risk of developing MNs, which was negligible until 40 years of age but rapidly increased to 49% by 90 years of age. Patients with myelodysplastic syndromes (MDS) along with a DDX41-mutation rapidly progressed to acute myeloid leukemia (AML), which was however, confined to those having truncating variants. Comutation patterns at diagnosis and at progression to AML were substantially different between DDX41-mutated and WT cases, in which none of the comutations affected clinical outcomes. Even TP53 mutations made no exceptions and their dismal effect, including multihit allelic status, on survival was almost completely mitigated by the presence of DDX41 mutations. Finally, outcomes were not affected by the conventional risk stratifications including the revised/molecular International Prognostic Scoring System. Our findings establish that MDS with DDX41-mutation defines a unique subtype of MNs that is distinct from other MNs.

Epitope Mismatch at HLA-DRB1 Associates with Reduced Relapse Risk in Cord Blood Transplantation for Standard-Risk Hematologic Malignancy.

Cord blood transplantation (CBT) is an attractive therapeutic option for patients with hematologic malignancies. CBT tolerates HLA mismatches between donors and recipients, but the HLA mismatches that generate graft-versus-tumor (GVT) effects remain unknown. Given that HLA molecules contain epitopes comprising polymorphic amino acids that determine their immunogenicity, we investigated associations between epitope-level HLA mismatches and relapse following single-unit CBT. A total of 492 patients with hematologic malignancies who underwent single-unit, T cell-replete CBT were included in this multicenter retrospective study. HLA epitope mismatches (EMs) were quantified using HLA matchmaker software from donor and recipient HLA-A, -B, -C, and -DRB1 allele data. Patients were dichotomized by median EM value and divided into 2 groups: patients who underwent transplantation in complete/partial remission (standard stage: 62.4%) and others (advanced stage: 37.6%). The median number of EMs in the graft-versus-host direction (GVH-EM) was 3 (range, 0 to 16) at HLA class I and 1 (range, 0 to 7) at HLA-DRB1. Higher HLA class I GVH-EM was associated with increased nonrelapse mortality (NRM) in the advanced stage group (adjusted hazard ratio [HR], 2.12; P = .021), with no significant advantage for relapse in either stage. In contrast, higher HLA-DRB1 GVH-EM was associated with better disease-free survival in the standard stage group (adjusted HR, .63; P = .020), which was attributed to lower relapse risk (adjusted HR, .46; P = .014). These associations also were observed even within HLA-DRB1 allele-mismatched transplantations in the standard stage group, indicating that EM might have an impact on relapse risk independent of allele mismatch. High HLA-DRB1 GVH-EM did not increase NRM in either stage. High HLA-DRB1 GVH-EM may lead to potent GVT effects and a favorable prognosis following CBT, especially in patients who underwent transplantation at the standard stage. This approach may facilitate appropriate unit selection and improve the overall prognosis of patients with hematologic malignancies who undergo CBT.

Coexistence of HLA and KIR ligand mismatches as a risk factor for viral infection early after cord blood transplantation.

Viral infection is one of the lethal adverse events after cord blood transplantation (CBT). Human leukocyte antigen (HLA) and killer immunoglobulin-like receptor (KIR) ligand divergences can increase the risk of viral infection due to conflicting interactions between virus-infected cells and immune cells. However, the relationship between these disparities and the frequency of viral infection after CBT remains to be evaluated. Herein, we have conducted a retrospective multicenter study to assess the effect of HLA and KIR ligand mismatches on viral infections after CBT. The study included 429 patients, among which 126 viral infections occurred before day 100. Viral infection was significantly associated with poorer overall survival (OS; hazard ratio [HR] 1.74, p < 0.01). Patients harboring ≥3 mismatches in the HLA allele and inhibitory KIR ligand mismatches (HLA & KIR mismatches) had a significantly greater prevalence of viral infection (HR 1.66, p = 0.04). Thus, patients with HLA & KIR mismatches had poorer outcomes in terms of non-relapse mortality (HR 1.61, p = 0.05). Our study demonstrates the unfavorable impacts of HLA & KIR mismatches on viral infections and non-relapse mortality after CBT. Evaluating the viral infection risk and performance of an appropriate and early intervention in high-risk patients and optimizing the graft selection algorithm could improve the outcome of CBTs.

Amplified EPOR/JAK2 Genes Define a Unique Subtype of Acute Erythroid Leukemia.

Acute erythroid leukemia (AEL) is a unique subtype of acute myeloid leukemia characterized by prominent erythroid proliferation whose molecular basis is poorly understood. To elucidate the underlying mechanism of erythroid proliferation, we analyzed 121 AEL using whole-genome, whole-exome, and/or targeted-capture sequencing, together with transcriptome analysis of 21 AEL samples. Combining publicly available sequencing data, we found a high frequency of gains and amplifications involving EPOR/JAK2 in TP53-mutated cases, particularly those having >80% erythroblasts designated as pure erythroid leukemia (10/13). These cases were frequently accompanied by gains and amplifications of ERG/ETS2 and associated with a very poor prognosis, even compared with other TP53-mutated AEL. In addition to activation of the STAT5 pathway, a common feature across all AEL cases, these AEL cases exhibited enhanced cell proliferation and heme metabolism and often showed high sensitivity to ruxolitinib in vitro and in xenograft models, highlighting a potential role of JAK2 inhibition in therapeutics of AEL. SIGNIFICANCE: This study reveals the major role of gains, amplifications, and mutations of EPOR and JAK2 in the pathogenesis of pure erythroleukemia. Their frequent response to ruxolitinib in patient-derived xenograft and cell culture models highlights a possible therapeutic role of JAK2 inhibition for erythroleukemia with EPOR/JAK2-involving lesions. This article is highlighted in the In This Issue feature, p. 369.