ATM germline pathogenic variants affect outcomes in children with ataxia-telangiectasia and hematological malignancies.

Ataxia-telangiectasia (A-T) is an autosomal-recessive disorder caused by pathogenic variants (PVs) of the ATM gene. Children with A-T are predisposed to hematological malignancies. We aimed to investigate their characteristics and outcomes in order to generate data-based treatment recommendations. In this multinational, observational study we report 202 patients aged ≤25 years with A-T and hematological malignancies from 25 countries. Ninety-one patients (45%) presented with mature B-cell lymphomas, 82 (41%) with acute lymphoblastic leukemia/lymphoma, 21(10%) with Hodgkin lymphoma and eight (4%) with other hematological malignancies. Four-year overall survival and event-free survival (EFS) were 50.8% (95% CI 43.6-59.1) and 47.9% (95% CI 40.8-56.2), respectively. Cure rates have not significantly improved over the last four decades (p=.76). The major cause of treatment failure was treatment-related mortality (TRM) with a four-year cumulative incidence of 25.9% (95% CI 19.5-32.4). Germline ATM PVs were categorized as null or hypomorphic and patients with available genetic data (n=110) were classified as having absent (n=81) or residual (n=29) ATM kinase activity. Four-year EFS was 39.4% (95% CI 29-53.3) vs 78.7% (95% CI 63.7-97.2), (p<.001), and TRM rates were 37.6% (95% CI 26.4-48.7) vs 4.0% (95% CI 0-11.8), (p=.017), for those with absent and residual ATM kinase activity, respectively. Absence of ATM kinase activity was independently associated with decreased EFS (HR=0.362, 95% CI 0.16-0.82; p=.009) and increased TRM (HR=14.11, 95% CI 1.36-146.31; p=.029). Patients with A-T and leukemia/lymphoma may benefit from de-escalated therapy for patients with absent ATM kinase activity and near-standard therapy regimens for those with residual kinase activity.

Genome-scale clustered regularly interspaced short palindromic repeats screen identifies nucleotide metabolism as an actionable therapeutic vulnerability in diffuse large B-cell lymphoma.

Diffuse large B-cell lymphoma (DLBCL) is the most common malignancy that develops in patients with ataxia-telangiectasia, a cancer-predisposing inherited syndrome characterized by inactivating germline ATM mutations. ATM is also frequently mutated in sporadic DLBCL. To investigate lymphomagenic mechanisms and lymphoma-specific dependencies underlying defective ATM, we applied ribonucleic acid (RNA)-seq and genome-scale loss-offunction clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 screens to systematically interrogate B-cell lymphomas arising in a novel murine model (Atm-/-nu-/-) with constitutional Atm loss, thymic aplasia but residual T-cell populations. Atm-/-nu-/-lymphomas, which phenotypically resemble either activated B-cell-like or germinal center Bcell-like DLBCL, harbor a complex karyotype, and are characterized by MYC pathway activation. In Atm-/-nu-/-lymphomas, we discovered nucleotide biosynthesis as a MYCdependent cellular vulnerability that can be targeted through the synergistic nucleotidedepleting actions of mycophenolate mofetil (MMF) and the WEE1 inhibitor, adavosertib (AZD1775). The latter is mediated through a synthetically lethal interaction between RRM2 suppression and MYC dysregulation that results in replication stress overload in Atm-/-nu-/-lymphoma cells. Validation in cell line models of human DLBCL confirmed the broad applicability of nucleotide depletion as a therapeutic strategy for MYC-driven DLBCL independent of ATM mutation status. Our findings extend current understanding of lymphomagenic mechanisms underpinning ATM loss and highlight nucleotide metabolism as a targetable therapeutic vulnerability in MYC-driven DLBCL.

Growth retardation and growth hormone deficiency in patients with Ataxia telangiectasia.

BACKGROUND: Ataxia telangiectasia (A-T) is a devastating human recessive disorder characterised by progressive cerebellar ataxia, immunodeficiency, genetic instability, and cancer susceptibility. In addition, many patients suffer from growth failure. METHODS: We analyzed growth and IGF-1/BP3 levels of 24 A-T-patients compared with an age-matched group of healthy controls (n = 36). RESULTS: Ten (41.7%) A-T patients and none of healthy controls had an IGF-1 level below the 3rd percentile for age. The growth hormone (GH) stimulation tests revealed a severe GH deficiency with no increase of >5 ng/ml in six of the ten A-T patients. The IGF-1 generation tests revealed normal increases in IGF-1 values in all patients. CONCLUSION: Our results show that a disturbance in the GH/IGF-1 axis was present in 58.3% of A-T patients. Low levels of GH were the result of reduced central GH secretion. GH treatment may be a therapeutic option for A-T patients with severe growth failure.

Childhood-Onset Movement Disorders Can Mask a Primary Immunodeficiency: 6 Cases of Classical Ataxia-Telangiectasia and Variant Forms.

Ataxia-telangiectasia (A-T) is a neurodegenerative and primary immunodeficiency disorder (PID) characterized by cerebellar ataxia, oculocutaneous telangiectasia, immunodeficiency, progressive respiratory failure, and an increased risk of malignancies. It demands specialized care tailored to the individual patient's needs. Besides the classical ataxia-telangiectasia (classical A-T) phenotype, a variant phenotype (variant A-T) exists with partly overlapping but some distinctive disease characteristics. Here we present a case series of 6 patients with classical A-T and variant A-T, which illustrates the phenotypic variability of A-T that can present in childhood with prominent extrapyramidal features, with or without cerebellar ataxia. We report the clinical data, together with a detailed genotype description, immunological analyses, and related expression of the ATM protein. We show that the presence of some residual ATM kinase activity leads to the clinical phenotype variant A-T that differs from the classical A-T. Our data illustrate that the diagnosis of the variant form of A-T can be delayed and difficult, while early recognition of the variant form as well as the classical A-T is a prerequisite for providing a correct prognosis and appropriate rehabilitation and support, including the avoidance of diagnostic X-ray procedures, given the increased risk of malignancies and the higher risk for side effects of subsequent cancer treatment.

Pre-emptive Allogeneic Hematopoietic Stem Cell Transplantation in Ataxia Telangiectasia.

Ataxia telangiectasia (A-T) is a primary immunodeficiency with mutations in the gene encoding the A-T mutated (ATM) protein that interacts with immune, hematopoietic, and endocrine targets resulting in broad multi-systemic clinical manifestations with a devastating outcome. Apart from a progressive neurodegenerative disorder, A-T leads to significantly increased susceptibility to malignancies. It is a matter of discussion whether pre-emptive allogeneic hematopoietic stem cell transplantation (alloHSCT) using a reduced intensity conditioning regimen would be an option to restore immune-competence and prevent malignancy, as shown in animal models, because conventional treatment protocols of malignant diseases using radio- and/or chemotherapy have a high rate of therapy-related morbidity and mortality in these patients. We present the course of the disease, including immune reconstitution and neurological outcome following pre-emptive alloHSCT in a 4-year-old boy with A-T on a 6 year follow-up. Our manuscript provides a proof-of-concept of alloHSCT as an individual pre-emptive treatment strategy from which some A-T patients might benefit.

Dynamic changes in clonal cytogenetic architecture during progression of chronic lymphocytic leukemia in patients and patient-derived murine xenografts.

Subclonal heterogeneity and clonal selection influences disease progression in chronic lymphocytic leukemia (CLL). It is therefore important that therapeutic decisions are made based on an understanding of the CLL clonal architecture and its dynamics in individual patients. Identification of cytogenetic abnormalities by FISH remains the cornerstone of contemporary clinical practice and provides a simple means for prognostic stratification. Here, we demonstrate that multiplexed-FISH can enhance recognition of CLL subclonal repertoire and its dynamics during disease progression, both in patients and CLL patient-derived xenografts (PDX). We applied a combination of patient-specific FISH probes to 24 CLL cases before treatment and at relapse, and determined putative ancestral relationships between subpopulations with different cytogenetic features. We subsequently established 7 CLL PDX models in NOD/Shi-SCID/IL-2Rγctm1sug/Jic (NOG) mice. Application of multiplexed-FISH to these models demonstrated that all of the identified cytogenetic subpopulations had leukemia propagating activity and that changes in their representation during disease progression could be spontaneous, accelerated by treatment or treatment-induced. We conclude that multiplexed-FISH in combination with PDX models have the potential to distinguish between spontaneous and treatment-induced clonal selection, and therefore provide a valuable tool for the pre-clinical evaluation of novel therapies.