No abstract

Most cases of adult myeloid neoplasms are routinely assumed to be sporadic. Here, we describe an adult familial acute myeloid leukemia (AML) syndrome caused by germline mutations in the DEAD/H-box helicase gene DDX41. DDX41 was also found to be affected by somatic mutations in sporadic cases of myeloid neoplasms as well as in a biallelic fashion in 50% of patients with germline DDX41 mutations. Moreover, corresponding deletions on 5q35.3 present in 6% of cases led to haploinsufficient DDX41 expression. DDX41 lesions caused altered pre-mRNA splicing and RNA processing. DDX41 is exemplary of other RNA helicase genes also affected by somatic mutations, suggesting that they constitute a family of tumor suppressor genes.

To elucidate differential roles of mutations in myelodysplastic syndromes (MDS), we investigated clonal dynamics using whole-exome and/or targeted sequencing of 699 patients, of whom 122 were analyzed longitudinally. Including the results from previous reports, we assessed a total of 2,250 patients for mutational enrichment patterns. During progression, the number of mutations, their diversity and clone sizes increased, with alterations frequently present in dominant clones with or without their sweeping previous clones. Enriched in secondary acute myeloid leukemia (sAML; in comparison to high-risk MDS), FLT3, PTPN11, WT1, IDH1, NPM1, IDH2 and NRAS mutations (type 1) tended to be newly acquired, and were associated with faster sAML progression and a shorter overall survival time. Significantly enriched in high-risk MDS (in comparison to low-risk MDS), TP53, GATA2, KRAS, RUNX1, STAG2, ASXL1, ZRSR2 and TET2 mutations (type 2) had a weaker impact on sAML progression and overall survival than type-1 mutations. The distinct roles of type-1 and type-2 mutations suggest their potential utility in disease monitoring.

Polycomb repressive complex 2 (PRC2) is involved in trimethylation of histone H3 lysine 27 (H3K27), chromatin condensation and transcriptional repression. The silencing function of PRC2 complex is mostly attributed to its intrinsic activity for methylating H3K27. Unlike in B-cell lymphomas, enhancer of zeste homolog 2 (EZH2) mutations in myeloid malignancies are inactivating/hypomorphic. When we assessed the mutational status in myeloid malignancies (N=469 cases examined), we found EZH2 and EED/SUZ12 mutations in 8% and 3.3% of cases, respectively. In addition to mutant cases, reduced EZH2 expression was also found in 78% cases with hemizygous deletion (-7/del7q cases involving EZH2 locus) and 41% of cases with diploid chromosome 7, most interestingly cases with spliceosomal mutations (U2AF1/SRSF2 mutations; 63% of cases). EZH2 mutations were characterized by decreased H3K27 trimethylation and increased chromatin relaxation at specific gene loci accompanied by higher transcriptional activity. One of the major downstream target is HOX gene family, involved in the regulation of stem cell self-renewal. HOXA9 was found to be overexpressed in cases with decreased EZH2 expression either by EZH2/spliceosomal mutations or because of -7/del7q. In summary, our results suggest that loss of gene repression through a variety of mutations resulting in reduced H3K27 trimethylation may contribute to leukemogenesis.

Paroxysmal nocturnal hemoglobinuria (PNH) is a nonmalignant clonal disease of hematopoietic stem cells that is associated with hemolysis, marrow failure, and thrombophilia. PNH has been considered a monogenic disease that results from somatic mutations in the gene encoding PIGA, which is required for biosynthesis of glycosylphosphatidylinisotol-anchored (GPI-anchored) proteins. The loss of certain GPI-anchored proteins is hypothesized to provide the mutant clone with an extrinsic growth advantage, but some features of PNH argue that there are intrinsic drivers of clonal expansion. Here, we performed whole-exome sequencing of paired PNH+ and PNH- fractions on samples taken from 12 patients as well as targeted deep sequencing of an additional 36 PNH patients. We identified additional somatic mutations that resulted in a complex hierarchical clonal architecture, similar to that observed in myeloid neoplasms. In addition to mutations in PIGA, mutations were found in genes known to be involved in myeloid neoplasm pathogenesis, including TET2, SUZ12, U2AF1, and JAK2. Clonal analysis indicated that these additional mutations arose either as a subclone within the PIGA-mutant population, or prior to PIGA mutation. Together, our data indicate that in addition to PIGA mutations, accessory genetic events are frequent in PNH, suggesting a stepwise clonal evolution derived from a singular stem cell clone.

Key Points STAT3+ T cells are found not only in detected concomitant LGL-BMFs, but in cases in which an LGL expansion was not suspected. Transformation via acquisition of a somatic mutation in T cells may be a mechanism of immune, mainly hypoplastic, bone marrow failure.

No abstract

The phase 3 ADMIRAL trial demonstrated superior overall survival (OS) in relapsed/refractory FLT3-mutation-positive acute myeloid leukemia patients randomized 2:1 to the oral FLT3 inhibitor, gilteritinib, versus those randomized to salvage chemotherapy (SC). Here we provide a follow-up of the ADMIRAL trial 2 years after the primary analysis to clarify the long-term treatment effects and safety of gilteritinib. At the time of this analysis, the median survival follow-up was 37.1 months, with deaths in 203/247 and 97/124 patients in the gilteritinib and SC arms, respectively; 16 gilteritinib-arm patients remained on treatment. The median OS for gilteritinib and SC arms was 9.3 and 5.6 months, respectively (HR=0.665; 95% CI: 0.518, 0.853; two-sided P=0.0013); 2-year estimated survival rates were 20.6% (95% CI: 15.8, 26.0) and 14.2% (95% CI: 8.3, 21.6), respectively. The gilteritinib-arm 2-year cumulative incidence of relapse after composite complete remission was 75.7%, with few relapses occurring after 18 months. Overall, 49/247 patients in the gilteritinib arm and 14/124 patients in the SC arm were alive for ≥2 years. Twenty-six gilteritinib-arm patients remained alive for ≥2 years without relapse; 18 of these patients underwent transplantation (HSCT) and 16 restarted gilteritinib as post-HSCT maintenance therapy. Most common adverse events (AEs) of interest during Years 1 and 2 of gilteritinib therapy were increased liver transaminases; AE incidence decreased in Year 2. Thus, continued and post-HSCT gilteritinib maintenance treatment sustained remission with a stable safety profile. These findings confirm that prolonged gilteritinib therapy is safe and is associated with superior survival versus SC. www.clinicaltrials.gov NCT02997202