sCD25 as an independent adverse prognostic factor in adult patients with HLH: results of a multicenter retrospective study.

Hemophagocytic lymphohistiocytosis (HLH) is a rare but often fatal hyperinflammatory syndrome caused by an inborn or acquired error of immunity. In adults, the underlying immunodeficiency generally arises alongside severe infections, malignancies, autoimmune diseases, and immunosuppressive treatment. To analyze risk factors and outcome in adults, we conducted a multicenter retrospective study. A total of 62 adult (age ≥18 years) patients met at least one of the following inclusion criteria: (1) ≥5 of 8 HLH-2004 criteria, (2) HScore ≥ 200 plus 4 HLH-2004 criteria, or (3) mutation compatible with an HLH diagnosis. Most patients (65%) were male, and the median age at diagnosis was 53.5 years (range, 19-81 years). All patients were assigned to 4 etiologic subgroups based on their most likely HLH trigger. The survival probability of the 4 etiologic subgroups differed significantly (P = .004, log-rank test), with patients with an underlying malignancy having the worst clinical outcome (1-year survival probability of 21%). The parameters older age, malignant trigger, elevated serum levels of aspartate transferase, creatinine, international normalized ratio, lactate dehydrogenase, sCD25, and a low albumin level and platelet count at treatment initiation were significantly (P < .1) associated with worse overall survival in the univariate Cox regression model. In multivariate analysis, sCD25 remained the only significant prognostic factor (P = .005). Our results suggest that sCD25 could be a useful marker for the prognosis of patients with HLH that might help to stratify therapeutic interventions.

Loss-of-function mutations in the histone methyltransferase EZH2 promote chemotherapy resistance in AML.

Chemotherapy resistance is the main impediment in the treatment of acute myeloid leukaemia (AML). Despite rapid advances, the various mechanisms inducing resistance development remain to be defined in detail. Here we report that loss-of-function mutations (LOF) in the histone methyltransferase EZH2 have the potential to confer resistance against the chemotherapeutic agent cytarabine. We identify seven distinct EZH2 mutations leading to loss of H3K27 trimethylation via multiple mechanisms. Analysis of matched diagnosis and relapse samples reveal a heterogenous regulation of EZH2 and a loss of EZH2 in 50% of patients. We confirm that loss of EZH2 induces resistance against cytarabine in the cell lines HEK293T and K562 as well as in a patient-derived xenograft model. Proteomics and transcriptomics analysis reveal that resistance is conferred by upregulation of multiple direct and indirect EZH2 target genes that are involved in apoptosis evasion, augmentation of proliferation and alteration of transmembrane transporter function. Our data indicate that loss of EZH2 results in upregulation of its target genes, providing the cell with a selective growth advantage, which mediates chemotherapy resistance.

Loss of KDM6A confers drug resistance in acute myeloid leukemia.

Acute myeloid leukemia (AML) is an aggressive hematologic neoplasm resulting from the malignant transformation of myeloid progenitors. Despite intensive chemotherapy leading to initial treatment responses, relapse caused by intrinsic or acquired drug resistance represents a major challenge. Here, we report that histone 3 lysine 27 demethylase KDM6A (UTX) is targeted by inactivating mutations and mutation-independent regulation in relapsed AML. Analyses of matched diagnosis and relapse specimens from individuals with KDM6A mutations showed an outgrowth of the KDM6A mutated tumor population at relapse. KDM6A expression is heterogeneously regulated and relapse-specific loss of KDM6A was observed in 45.7% of CN-AML patients. KDM6A-null myeloid leukemia cells were more resistant to treatment with the chemotherapeutic agents cytarabine (AraC) and daunorubicin. Inducible re-expression of KDM6A in KDM6A-null cell lines suppressed proliferation and sensitized cells again to AraC treatment. RNA expression analysis and functional studies revealed that resistance to AraC was conferred by downregulation of the nucleoside membrane transporter ENT1 (SLC29A1) by reduced H3K27 acetylation at the ENT1 locus. Our results show that loss of KDM6A provides cells with a selective advantage during chemotherapy, which ultimately leads to the observed outgrowth of clones with KDM6A mutations or reduced KDM6A expression at relapse.

Evolution of Cytogenetically Normal Acute Myeloid Leukemia During Therapy and Relapse: An Exome Sequencing Study of 50 Patients.

Purpose: To study mechanisms of therapy resistance and disease progression, we analyzed the evolution of cytogenetically normal acute myeloid leukemia (CN-AML) based on somatic alterations.Experimental Design: We performed exome sequencing of matched diagnosis, remission, and relapse samples from 50 CN-AML patients treated with intensive chemotherapy. Mutation patterns were correlated with clinical parameters.Results: Evolutionary patterns correlated with clinical outcome. Gain of mutations was associated with late relapse. Alterations of epigenetic regulators were frequently gained at relapse with recurring alterations of KDM6A constituting a mechanism of cytarabine resistance. Low KDM6A expression correlated with adverse clinical outcome, particularly in male patients. At complete remission, persistent mutations representing preleukemic lesions were observed in 48% of patients. The persistence of DNMT3A mutations correlated with shorter time to relapse.Conclusions: Chemotherapy resistance might be acquired through gain of mutations. Insights into the evolution during therapy and disease progression lay the foundation for tailored approaches to treat or prevent relapse of CN-AML. Clin Cancer Res; 24(7); 1716-26. ©2018 AACR.