Gain-of-function mutations in RPA1 cause a syndrome with short telomeres and somatic genetic rescue.

Human telomere biology disorders (TBD)/short telomere syndromes (STS) are heterogeneous disorders caused by inherited loss-of-function mutations in telomere-associated genes. Here, we identify 3 germline heterozygous missense variants in the RPA1 gene in 4 unrelated probands presenting with short telomeres and varying clinical features of TBD/STS, including bone marrow failure, myelodysplastic syndrome, T- and B-cell lymphopenia, pulmonary fibrosis, or skin manifestations. All variants cluster to DNA-binding domain A of RPA1 protein. RPA1 is a single-strand DNA-binding protein required for DNA replication and repair and involved in telomere maintenance. We showed that RPA1E240K and RPA1V227A proteins exhibit increased binding to single-strand and telomeric DNA, implying a gain in DNA-binding function, whereas RPA1T270A has binding properties similar to wild-type protein. To study the mutational effect in a cellular system, CRISPR/Cas9 was used to knock-in the RPA1E240K mutation into healthy inducible pluripotent stem cells. This resulted in severe telomere shortening and impaired hematopoietic differentiation. Furthermore, in patients with RPA1E240K, we discovered somatic genetic rescue in hematopoietic cells due to an acquired truncating cis RPA1 mutation or a uniparental isodisomy 17p with loss of mutant allele, coinciding with stabilized blood counts. Using single-cell sequencing, the 2 somatic genetic rescue events were proven to be independently acquired in hematopoietic stem cells. In summary, we describe the first human disease caused by germline RPA1 variants in individuals with TBD/STS.

Additive value of transarterial embolization to systemic sirolimus treatment in kaposiform hemangioendothelioma.

Kaposiform hemangioendothelioma (KHE) is a rare vascular tumor in children, which can be accompanied by life-threatening thrombocytopenia, referred to as Kasabach-Merritt phenomenon (KMP). The mTOR inhibitor sirolimus is emerging as targeted therapy in KHE. As the sirolimus effect on KHE occurs only after several weeks, we aimed to evaluate whether additional transarterial embolization is of benefit for children with KHE and KMP. Seventeen patients with KHE and KMP acquired from 11 hospitals in Germany were retrospectively divided into two cohorts. Children being treated with adjunct transarterial embolization and systemic sirolimus, and those being treated with sirolimus without additional embolization. Bleeding grade as defined by WHO was determined for all patients. Response of the primary tumor at 6 and 12 months assessed by magnetic resonance imaging (MRI), time to response of KMP defined as thrombocyte increase >150 × 103 /µL, as well as rebound rates of both after cessation of sirolimus were compared. N = 8 patients had undergone additive embolization to systemic sirolimus therapy, sirolimus in this group was started after a mean of 6.5 ± 3 days following embolization. N = 9 patients were identified who had received sirolimus without additional embolization. Adjunct embolization induced a more rapid resolution of KMP within a median of 7 days vs 3 months; however, tumor response as well as rebound rates were similar between both groups. Additive embolization may be of value for a more rapid rescue of consumptive coagulopathy in children with KHE and KMP compared to systemic sirolimus only.

Relapses and treatment-related events contributed equally to poor prognosis in children with ABL-class fusion positive B-cell acute lymphoblastic leukemia treated according to AIEOP-BFM protocols.

ABL-class fusions other than BCR-ABL1 characterize around 2-3% of precursor B-cell acute lymphoblastic leukemia. Case series indicated that patients suffering from these subtypes have a dismal outcome and may benefit from the introduction of tyrosine kinase inhibitors. We analyzed clinical characteristics and outcome of 46 ABL-class fusion positive cases other than BCR-ABL1 treated according to AIEOP-BFM (Associazione Italiana di Ematologia-Oncologia Pediatrica-Berlin-Frankfurt-Münster) ALL 2000 and 2009 protocols; 13 of them received a tyrosine kinase inhibitor (TKI) during different phases of treatment. ABL-class fusion positive cases had a poor early treatment response: minimal residual disease levels of ≥5×10-4 were observed in 71.4% of patients after induction treatment and in 51.2% after consolidation phase. For the entire cohort of 46 cases, the 5-year probability of event-free survival was 49.1+8.9% and that of overall survival 69.6+7.8%; the cumulative incidence of relapse was 25.6+8.2% and treatment-related mortality (TRM) 20.8+6.8%. One out of 13 cases with TKI added to chemotherapy relapsed while eight of 33 cases without TKI treatment suffered from relapse, including six in 17 patients who had not received hematopoietic stem cell transplantation. Stem cell transplantation seems to be effective in preventing relapses (only three relapses in 25 patients), but was associated with a very high TRM (6 patients). These data indicate a major need for an early identification of ABL-class fusion positive acute lymphoblastic leukemia cases and to establish a properly designed, controlled study aimed at investigating the use of TKI, the appropriate chemotherapy backbone and the role of hematopoietic stem cell transplantation. (Registered at: clinicaltrials.gov identifier: NTC00430118, NCT00613457, NCT01117441).

Interventional radiotherapy (brachytherapy) achieves very good long-term quality of life in children and adolescents with soft-tissue sarcoma.

BACKGROUND: Effective local therapy (surgery, radiation) and systemic multidrug chemotherapy are mandatory for curing childhood sarcoma. The standard radiation therapy for pediatric patients with soft-tissue sarcoma (STS) is external beam radiotherapy (EBRT). Because EBRT may cause long-term side effects with adverse effects on the patients' health and quality of life (QoL), alternative strategies are required. Interventional radiotherapy (IRT; brachytherapy) is established as a standard treatment for several tumors in adulthood. Single-center series have reported low levels of late effects and improved QoL in survivors treated with IRT in childhood. However, IRT is still applied infrequently in pediatric patients. METHODS: Thirty patients with STS were treated with IRT between 1992 and 2012 at the University Hospital Schleswig Holstein, Germany. Five patients were lost to follow-up, and 25 patients (mean age at time of data collection 24.8 years [range, 10.7-36.1]) could be analyzed focusing on overall survival and QoL (EORTC-C30 questionnaire). For more detailed information regarding general and health-specific questions, a separate questionnaire was developed. RESULTS: Nineteen of 25 patients were alive 13.4 [1.6-25.2] years after first cancer disease, and the three-year overall survival was 76% (SE, 0.09). The score of QoL/global health status (76.2 [16.6-100]) in our patients outvalues the European (66.1) and equals the German (75.9) reference value. CONCLUSION: IRT is an effective treatment option for pediatric patients with localized STS. Its role among other radiation dose-sparing techniques such as proton beam therapy has to be defined in prospective studies.

[DKG certification of paediatric cancer centres - a wide field ]. / DKG-Zertifizierung kinderonkologischer Zentren ­ ein weites Feld .

The German Society of Paediatric Oncology and Haematology (GPOH) and the German Cancer Society (DKG) have defined criteria for DKG certification of paediatric oncology departments. Since 2017, several paediatric oncology departments have already been certified according to these criteria. DKG certification aims for the harmonized and transparent presentation of the quality of care of paediatric oncology patients, as described by Mensah et al. The definition of certification criteria led to controversies within the GPOH about how far the criteria themselves would withstand scientific verifiability.We critically reviewed the paper by Mensah et al. asking whether valid conclusions for the German health system could be drawn from it. We found that currently defined criteria for DKG certification of paediatric oncology departments lack scientific evidence for German paediatric cancer centres in critical aspects.This article challenges case numbers as a parameter for the measurement of quality of care in German paediatric oncology. We try to contribute to an open discussion about alternative criteria for ensuring quality of care in German paediatric oncology departments.

THROMBOTECT - a randomized study comparing low molecular weight heparin, antithrombin and unfractionated heparin for thromboprophylaxis during induction therapy of acute lymphoblastic leukemia in children and adolescents.

Thromboembolism is a serious complication of induction therapy for childhood acute lymphoblastic leukemia. We prospectively compared the efficacy and safety of antithrombotic interventions in the consecutive leukemia trials ALL-BFM 2000 and AIEOP-BFM ALL 2009. Patients with newly diagnosed acute lymphoblastic leukemia (n=949, age 1 to 18 years) were randomized to receive low-dose unfractionated heparin, prophylactic low molecular weight heparin (enoxaparin) or activity-adapted antithrombin throughout induction therapy. The primary objective of the study was to determine whether enoxaparin or antithrombin reduces the incidence of thromboembolism as compared to unfractionated heparin. The principal safety outcome was hemorrhage; leukemia outcome was a secondary endpoint. Thromboembolism occurred in 42 patients (4.4%). Patients assigned to unfractionated heparin had a higher risk of thromboembolism (8.0%) compared with those randomized to enoxaparin (3.5%; P=0.011) or antithrombin (1.9%; P<0.001). The proportion of patients who refused antithrombotic treatment as allocated was 3% in the unfractionated heparin or antithrombin arms, and 33% in the enoxaparin arm. Major hemorrhage occurred in eight patients (no differences between the groups). The 5-year event-free survival was 80.9±2.2% among patients assigned to antithrombin compared to 85.9±2.0% in the unfractionated heparin group (P=0.06), and 86.2±2.0% in the enoxaparin group (P=0.10). In conclusion, prophylactic use of antithrombin or enoxaparin significantly reduced thromboembolism. Despite the considerable number of patients rejecting the assigned treatment with subcutaneous injections, the result remains unambiguous. Thromboprophylaxis - for the present time primarily with enoxaparin - can be recommended for children and adolescents with acute lymphoblastic leukemia during induction therapy. Whether and how antithrombin may affect leukemia outcome remains to be determined.

Invasive mold disease of the central nervous system in children and adolescents with cancer or undergoing hematopoietic stem cell transplantation: Analysis of 29 contemporary patients.

BACKGROUND: Invasive mold disease (IMD) is a severe infectious complication in immunocompromised patients. The outcome of central nervous system (CNS) IMD is poor, but contemporary data, in particular in the pediatric setting, are lacking. PROCEDURE: For this retrospective multicenter analysis, pediatric patients < 18 years with proven or probable CNS IMD receiving chemotherapy or undergoing allogeneic HSCT were reported by the local investigator. CNS IMD had to be diagnosed between 2007 and 2016. Proven CNS IMD was defined as compatible CNS imaging or macroscopic autopsy findings in conjunction with a positive microscopic or microbiological result in the brain tissue or cerebrospinal fluid. Probable CNS IMD was defined as compatible CNS imaging findings in combination with proven or probable IMD at a site outside the CNS. RESULTS AND CONCLUSIONS: A total of 29 patients (median age, 14 years; 14 allogeneic HSCT recipients) were diagnosed with proven (n = 12) or probable (n = 17) CNS IMD. Aspergillus spp. was the most common fungal pathogen. All but one patient had IMD sites outside the CNS and eight patients (27.6%) were neurologically asymptomatic at diagnosis of CNS IMD. Forty-nine percent of the patients survived CNS IMD; however, 46.7% of the survivors suffered from severe long-term neurological sequelae. Our data suggest that (1) outcome of CNS IMD has improved in children as compared with previous series, (2) half of surviving patients suffer from severe neurological sequelae, and (3) imaging of the CNS should be performed in all children with IMD irrespective of neurological symptoms.

Therapy with low-dose azacitidine for MDS in children and young adults: a retrospective analysis of the EWOG-MDS study group.

Low-dose azacitidine is efficient and safe in the therapy of malignant myeloid disorders in adults but data in children are lacking. We present a retrospective analysis of 24 children and young adults with myelodysplastic syndrome (MDS) who received azacitidine at the time of first diagnosis or relapse after allotransplant (2 children were treated with azacitidine both initially and for relapse). Diagnoses were refractory cytopenia of childhood (N = 4), advanced primary MDS (N = 9) and secondary MDS (N = 11). The median duration of treatment was four cycles. Azacitidine was well tolerated, but cytopenias led to dose reduction in five cases. Treatment was discontinued in one child because of impaired renal function. Sixteen MDS patients were treated with azacitidine at first diagnosis. One complete clinical remission was observed and one child showed complete marrow remission; six children experienced stable disease with haematological improvement. Ten children received azacitidine for relapsed MDS after transplant: of these, seven experienced stable disease for 2-30 cycles (median 3), including one patient with haematological improvement for seven cycles. In summary, azacitidine is effective in some children with MDS and appears to be a non-toxic option in palliative situations to prolong survival.

Impact of high risk thrombophilia status on recurrence among children and adults with VTE: An observational multicenter cohort study.

BACKGROUND: Antithrombin [AT]-, protein C [PC]- or protein S [PS]-deficiency [D] constitutes a major risk factor for venous thromboembolism [VTE]. Primary study objective was to evaluate if the clinical presentation at first VTE onset differs between children and adults and to compare the individual recurrence risk among patients with respect to age at onset and their thrombophilia status ATD, PCD or PSD. METHODS/PATIENTS/RESULTS: In 137 of 688 consecutively enrolled pediatric and adult VTE patients we calculated the absolute risk of VTE recurrence and event-free-survival adjusted for thrombophilia and positive family VTE history. At first VTE children manifested i) with a lower rate of pulmonary embolism, ii) a higher rate of cerebral vascular events or multiple VTEs, and iii) showed a higher proportion of unprovoked VTE compared to adolescents and adults. Adult patients reported more often a positive VTE history compared to younger study participants. The adjusted odds of recurrence in adults was 2.05 compared to children. CONCLUSION: At disease manifestation children and adults differ with respect to i) thrombotic locations, ii) percentage of unprovoked versus provoked VTE, and iii) different rates of positive VTE family histories. Furthermore, adults showed a two-fold increase risk of VTE recurrence compared to children.

Sustained complete molecular remission after imatinib discontinuation in children with chronic myeloid leukemia.

Approximately 40% of adults with chronic myeloid leukemia (CML) in prolonged complete molecular response (CMR) remain in CMR after imatinib discontinuation. Corresponding information in children is lacking. Two children with CML in CMR for 48 and 19 months after imatinib discontinuation showed low-level fluctuating disease at RNA transcript and genomic DNA levels. Both patients were low risk according to adult criteria. Since adults with molecular relapse responded to re-introduction of imatinib, we postulated that treatment discontinuation in low risk children might be justified within clinical trials with close monitoring. This may help to minimize exposure to imatinib and its potential side effects.

Frequency and clinical impact of viraemia in paediatric patients undergoing therapy for cancer.

In contrast to transplant recipients, there is a paucity of data regarding frequency and clinical significance of viraemia in children receiving conventional chemotherapy. In a prospective observational study, we assessed the frequency of and clinical impact of viraemia with cytomegalovirus (CMV), Epstein-Barr virus (EBV), adenovirus, human herpesvirus-6 (HHV6) and herpes-simplex virus 1/2 (HSV1/2) in paediatric cancer patients at diagnosis, at a routine examination during intensive chemotherapy, and during febrile neutropenia (FN). Seventy-nine patients (median age 6 years; 66 children with haematological malignancies) were included in the study. Overall, 362 blood samples were analysed, 72 from the time at diagnosis (11.1% with positive PCR result), 118 during a regular control after chemotherapy (11.0% positive), and 159 during FN (8.8% positive). The overall positivity rate was 9.6% (CMV 3.3%, HHV6 2.7%, HSV 2.2%, EBV 0.8% and adenovirus 0.3%). There were no significant differences between FN episodes with and without viraemia in terms of duration of fever or neutropenia/lymphopenia, severity of mucositis (> II0), incidence of diarrhea and ICU admission. Our results indicate that viraemia in paediatric cancer patients generally does not have a major clinical impact, and may help in the decision regarding the indication of routine evaluation for viraemia in febrile neutropenic, but otherwise asymptomatic children.

Coping in long-term survivors of childhood cancer: relations to psychological distress.

OBJECTIVE: The goal of this study was to describe coping strategies and their associations with psychological distress in young adult survivors of childhood cancer. METHODS: One hundred and sixty-four childhood cancer survivors, at least 7 years after diagnosis, completed questionnaires assessing demographics, health information, psychological distress, and different ways of coping (return rate: 61%). The Brief Symptom Inventory-18 (BSI-18) and the Post-traumatic Diagnostic Scale's (PDS) eight-item short form were used to measure psychological distress. Coping was assessed with the Cognitive Control Strategies Scale (CCSS), the Illness Perception Questionnaire-Revised (IPQ-R), and the White Bear Suppression Inventory (WBSI). RESULTS: Higher levels of distress were associated with the female sex, not being in a relationship, and with the presence of medical late effects. These predictors explained 12% of the variance in psychological distress. When coping variables were also entered into the equation, the amount of explained variance increased to 50%. The most important determinants of psychological distress in our sample were a tendency to suppress negative thoughts and a low level of optimism. CONCLUSION: These results contribute to a better understanding of the correlates of difficulties in long-term psychological adjustment after childhood cancer. Cognitive strategies, which are associated with or may increase the risk for concurrent psychological distress, in specific, avoidance of negative thoughts and a lack of positive future expectations, should be addressed in psychological counseling with survivors suffering from symptoms of distress.

Pilot study shows suppression of mineralocorticoid precursors under high-dose glucocorticoid therapy in pediatric acute lymphoblastic leukemia.

Glucocorticoids represent a key element in the treatment of pediatric acute lymphoblastic leukemia (ALL) and lead to adrenal suppression. We aimed to assess the differential response profile of adrenal steroids in children with ALL during BFM (Berlin-Frankfurt-Münster) induction treatment. Therefore, we performed liquid chromatography tandem-mass spectrometry (LC-MS/MS)-based steroid profiling of up to seven consecutive leftover morning serum samples derived from 11 patients (pts) with ALL before (day 0) and during induction therapy at days 1-5, 6-12, 13-26, 27-29, 30-35 and 36-40. 17-hydroxyprogesterone (17OHP), 11-deoxycortisol (11S), cortisol, 11-deoxycorticosterone (DOC), corticosterone and aldosterone were determined in parallel. Subsequently, steroid concentrations were normalized by multiples of median (MOM) to adequately consider pediatric age- and sex-specific reference ranges. MOM-cortisol and its precursors MOM-11S and MOM-17OHP were significantly suppressed by glucocorticoid treatment until day 29 (P < 8.06 × 10-10, P < 5.102 × 10-5, P < 0.0076, respectively). Cortisol recovered in one of four pts at days 27-29 and in two of five pts at days 36-40. Among the mineralocorticoids, corticosterone was significantly suppressed (P < 3.115 × 10-6). Aldosterone and DOC showed no significant changes when comparing day 0 to the treatment time points. However, two ALL patients with ICU treatment due to the sepsis showed significantly lower MOM-DOC (P = 0.006436) during that time and almost always the lowest aldosterone compared to all other time points. Suppression of mineralocorticoid precursors under high-dose glucocorticoid therapy suggests a functional cross talk of central glucocorticoid regulation and adrenal mineralocorticoid synthesis. Our data should stimulate prospective investigation to assess potential clinical relevance.

MicroRNA-profiling of miR-371~373- and miR-302/367-clusters in serum and cerebrospinal fluid identify patients with intracranial germ cell tumors.

PURPOSE: Intracranial germ cell tumors (iGCT) comprise germinoma and non-germinoma. Their diagnosis predominantly relies on biopsy as only one-fifth of patients present with elevated biomarkers (AFP/ß-HCG) in serum or cerebrospinal fluid (CSF). MicroRNAs (miR/miRNA) have emerged as non-invasive biomarkers in extracranial GCT and may potentially facilitate non-invasive diagnosis in iGCT. METHODS: We analyzed eight miRNAs in serum and CSF from the miR-371~373- and miR-302/367-clusters and four miRNAs differentially expressed in iGCT tissue (miR-142-5p/miR-146a-5p/miR-335-5p/miR-654-3p) from eight iGCT patients (age 10-33 years) and 12 control subjects by pre-amplified RT-qPCR. MiR-30b-5p (serum) and miR-204-5p (CSF) acted as reference genes. ΔCt-values were expressed as [Formula: see text] after standardization against controls. RESULTS: Between iGCT and control patients' serum ΔCt-values of miR-371a-3p (p = 0.0159), miR-372-3p (p= 0.0095, miR-367 (p = 0.0190), miR-302a (p = 0.0381) and miR-302d-3p (p = 0.0159) differed significantly. Discriminatory pattern in CSF was similar to serum as miR-371a (p = 0.0286), miR-372-3p (p = 0.0028), miR-367-3p (p = 0.0167) and miR-302d-3p (p = 0.0061) distinguished between patients and controls. Abundant [Formula: see text] levels of each of these miRNAs were found across all serum and CSF samples including biomarker-negative patients. CONCLUSION: With the largest data set so far, we underline the suitability of miR-371a, miR-372, miR-367 and miR-302d in serum and CSF for diagnosis of iGCT, particularly in biomarker-negative germinoma. Diagnosis of iGCT by miRNA analysis is a feasible and valid approach, particularly as serum can be readily obtained by a less invasive procedure. MiRNA analysis may discriminate iGCT from other tumors with similar radiological findings and may allow to monitor response to therapy as well as early relapse during follow-up.

Prediction of outcome by early bone marrow response in childhood acute lymphoblastic leukemia treated in the ALL-BFM 95 trial: differential effects in precursor B-cell and T-cell leukemia.

BACKGROUND: In the ALL-BFM 95 trial for treatment of acute lymphoblastic leukemia, response to a prednisone pre-phase (prednisone response) was used for risk stratification in combination with age and white blood cell count at diagnosis, response to induction therapy and specific genetic high-risk features. DESIGN AND METHODS: Cytomorphological marrow response was prospectively assessed on Day 15 during induction, and its prognostic value was analyzed in 1,431 patients treated on ALL-BFM 95. RESULTS: The 8-year probabilities of event-free survival were 86.1%, 74.5%, and 46.4% for patients with M1, M2, and M3 Day 15 marrows, respectively. Compared to prednisone response, Day 15 marrow response was superior in outcome prediction in precursor B-cell and T-cell leukemia with, however, a differential effect depending on blast lineage. Outcome was poor in T-cell leukemia patients with prednisone poor-response independent of Day 15 marrow response, whereas among patients with prednisone good-response different risk groups could be identified by Day 15 marrow response. In contrast, prednisone response lost prognostic significance in precursor B-cell leukemia when stratified by Day 15 marrow response. Age and white blood cell count retained their independent prognostic effect. CONCLUSIONS: Selective addition of Day 15 marrow response to conventional stratification criteria applied on ALL-BFM 95 (currently in use in several countries as regular chemotherapy protocol for childhood acute lymphoblastic leukemia) may significantly improve risk-adapted treatment delivery. Even though cutting-edge trial risk stratification is meanwhile dominated by minimal residual disease evaluation, an improved conventional risk assessment, as presented here, could be of great importance to countries that lack the technical and/or financial resources associated with the application of minimal residual disease analysis.

Are radiation-induced cavernomas clinically relevant findings? Results from long-term follow-up with brain magnetic resonance imaging of childhood cancer survivors.

INTRODUCTION: Radiation-induced cavernomas (RIC) after cranial radiotherapy have an unknown risk of hemorrhage. Zabramski magnetic resonance imaging (MRI) classification is touted as being able to indicate non-radiation-induced cavernomas hemorrhage risk. The aim of our study was to assess the hemorrhage risk of RIC during long-term follow-up of childhood cancer survivors based on brain MRI examinations. PATIENTS AND METHODS: We analyzed retrospectively long-term follow-up data of 36 childhood cancer survivors after initial diagnosis with acute leukemia (n = 18) or brain tumor (n = 18), all treated with cranial radiotherapy. Detected RIC in long-term follow-up brain MRI (1.5 or 3 Tesla) were classified following the Zabramski MRI classification and were categorized into "high" (Zabramski type I, II or V) or "low" (type III or IV) risk of hemorrhage. RESULTS: 18 patients (50%) showed RIC with a significant relation to the original tumor entity (p = 0.023) and the cumulative radiation dose to the brain (p = 0.016): all 9 childhood cancer survivors diagnosed with medulloblastoma developed RIC. We classified RIC in only 3/36 childhood cancer survivors (8%) (1 patient with acute lymphoblastic leukemia [Zabramski type II] and 2 patients with medulloblastoma [type I and type II]) as high risk for hemorrhage, the remaining RIC were classified as Zabramski type IV with low risk for hemorrhage. None of the childhood cancer survivors with RIC showed symptomatic hemorrhages. CONCLUSIONS: RIC are common late effects in childhood cancer survivors treated with cranial radiotherapy affecting half of these patients. However, only a few RIC (occurring in 8% of all reviewed childhood cancer survivors) were classified as high risk for hemorrhage and none of the childhood cancer survivors with RIC developed symptomatic hemorrhages. Thus, we conclude that RIC are low-risk findings in brain MRI and the course is mainly benign.

CD73-mediated adenosine production by CD8 T cell-derived extracellular vesicles constitutes an intrinsic mechanism of immune suppression.

Immune cells at sites of inflammation are continuously activated by local antigens and cytokines, and regulatory mechanisms must be enacted to control inflammation. The stepwise hydrolysis of extracellular ATP by ectonucleotidases CD39 and CD73 generates adenosine, a potent immune suppressor. Here we report that human effector CD8 T cells contribute to adenosine production by releasing CD73-containing extracellular vesicles upon activation. These extracellular vesicles have AMPase activity, and the resulting adenosine mediates immune suppression independently of regulatory T cells. In addition, we show that extracellular vesicles isolated from the synovial fluid of patients with juvenile idiopathic arthritis contribute to T cell suppression in a CD73-dependent manner. Our results suggest that the generation of adenosine upon T cell activation is an intrinsic mechanism of human effector T cells that complements regulatory T cell-mediated suppression in the inflamed tissue. Finally, our data underscore the role of immune cell-derived extracellular vesicles in the control of immune responses.

Hepatic sinusoidal obstruction syndrome and short-term application of 6-thioguanine in pediatric acute lymphoblastic leukemia.

Long-term treatment with 6-thioguanine (6-TG) for pediatric acute lymphoblastic leukemia (ALL) is associated with high rates of hepatic sinusoidal obstruction syndrome (SOS). Nevertheless, current treatment continues to use short-term applications of 6-TG with only sparse information on toxicity. 6-TG is metabolized by thiopurine methyltransferase (TPMT) which underlies clinically relevant genetic polymorphism. We analyzed the association between hepatic SOS reported as a serious adverse event (SAE) and short-term 6-TG application in 3983 pediatric ALL patients treated on trial AIEOP-BFM ALL 2000 (derivation cohort) and defined the role of TPMT genotype in this relationship. We identified 17 patients (0.43%) with hepatic SOS, 13 of which with short-term exposure to 6-TG (P < 0.0001). Eight of the 13 patients were heterozygous for low-activity TPMT variants, resulting in a 22.4-fold (95% confidence interval 7.1-70.7; P ≤ 0.0001) increased risk of hepatic SOS for heterozygotes in comparison to TPMT wild-type patients. Results were supported by independent replication analysis. All patients with hepatic SOS after short-term 6-TG recovered and did not demonstrate residual symptoms. Thus, hepatic SOS is associated with short-term exposure to 6-TG during treatment of pediatric ALL and SOS risk is increased for patients with low-activity TPMT genotypes.