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To assess COVID-19-pandemic related anxiety and emotional-behavioral difficulties among oncologic children and their caregivers.Prospective cohort study conducted from March to November 2020.76 pediatric oncological and 28 nonmalignant hematological patients aged 1.6-23.4 years and their caregivers.A total of 104 families completed an age-specific self-report psychological assessment; of these, 20 oncologic families completed the assessment at two time points.Ten percent of the caregivers and 13.9% of the patients reported anxiety disorder. Additionally, 3.1% of the caregivers reported behavioral difficulties. No significant differences emerged between patients' self-reports and caregivers' reports. No differences emerged between oncological and nonmalignant hematological participants.The prevalence of anxiety associated with the COVID-19 pandemic was similar to the reported prevalence of anxiety following a diagnosis of pediatric malignancy.Real-time assessment of psychological effects revealed no COVID-19-associated anxiety. Nonetheless, late effects will need to be monitored.

To determine the incidence, clinical presentation, and outcome of methotrexate (MTX) associated neurotoxicity in pediatric patients treated for osteosarcoma, with the aim of identifying possible risk factors and suggesting recommended treatment for these sequelae.All medical files of patients treated for osteosarcoma in a single pediatric haemato-oncology center between November 2011 and August 2021 were retrospectively reviewed. All patients were treated according to the EURAMOS AOST0331 protocol, using cisplatin, doxorubicin, and high-dose MTX at a dose of 12 g/mSeventy-eight patients with osteosarcoma were identified (age range 5 to 23 years, 42 males). Seven patients (9%) sustained neurotoxicity following treatment with high-dose MTX. Manifestations of neurotoxicity included among others, generalized seizures, confusion, encephalopathy, dysarthria, and choreiform movements. All but one episode occurred following two sequential cycles of high-dose MTX. All 7 had subacute toxicity, 5-10 days following MTX administration, and 1 had both acute and subacute toxicity. Brain MRI was performed for all patients and demonstrated typical MRI changes attributed to MTX neurotoxicity in 4 of them. Two patients received aminophylline; one patient received dextromethorphan. Patients with normal MRI imaging resumed MTX therapy without any sequels. No risk factors were found for high-dose MTX-related toxicity occurrence.The time of risk of neurotoxicity due to high-dose MTX treatment for osteosarcoma is days 5-10 following two sequential treatment cycles. These findings together with treatment options for these adverse effects should be detailed in the therapeutic protocol of MTX use among pediatric patients with osteosarcoma.

Intramedullary spinal cord high-grade gliomas are rare and almost always fatal pediatric tumors. The current treatment paradigms are surgery, and radiotherapy. This is the first description of a toddler with an intramedullary cervical high-grade glioma harboring an anaplastic lymphoma kinase (ALK) fusion (KIF5B) whose treatment with the ALK inhibitor, alectinib, achieved clinical and radiological evidence of complete remission after six months of treatment. Our findings suggest that ALK inhibitors may emerge as an effective therapy in malignant spinal tumors with a dismal prognosis.

Neutrophils are central players in the innate immune system. To protect against invading pathogens, neutrophils can externalize chromatin to create neutrophil extracellular traps (NETs). While NETs are critical to host defense, they also have deleterious effects, and dysregulation of NETs formation has been implicated in autoimmune diseases, atherosclerosis and thrombotic conditions, cancer progression and dissemination, and acute respiratory distress syndrome. Here, we report that selinexor, a first-in-class selective inhibitor of nuclear export approved for the treatment of multiple myeloma and diffuse large B-cell lymphoma, markedly suppressed the release of NETs in vitro. Furthermore, we demonstrate a significant inhibitory effect of selinexor on NETs formation, but not on oxidative burst or enzymatic activities central to NETs release such as neutrophil elastase, myeloperoxidase or peptidyl arginine deiminase type IV. The inhibitory effect of selinexor was demonstrated in neutrophils activated by a variety of NETs-inducers, including PMA, TGF-β, TNF-α and IL-8. Maximal inhibition of NETs formation was observed using TGF-β, for which selinexor inhibited NETs release by 61.6%. These findings pave the way to the potential use of selinexor in an effort to reduce disease burden by inhibition of NETs.

Invasive Fusarium species infections in immunocompromised patients occur predominantly in those with hematological malignancies. Survival rates of 20–40% were reported in adults, but data in children are limited. Our retrospective, nationwide multicenter study of invasive fusariosis in pediatric hematology/oncology and stem cell transplant (SCT) patients identified twenty-two cases. Underlying conditions included hematological malignancies (n = 16; 73%), solid tumors (n = 2), and non-malignant hematological conditions (n = 4). Nineteen patients (86%) were neutropenic, nine (41%) were SCT recipients, and seven (32%) received corticosteroids. Sixteen patients (73%) had disseminated fusariosis, five had local infection, and one had isolated fungemia. Fifteen patients (68%) had skin involvement and eight (36%) had a bloodstream infection. Four patients (18%) presented with osteoarticular involvement and four with pulmonary involvement. Nineteen patients (86%) received combination antifungal therapy upfront and three (14%) received single-agent treatment. Ninety-day probability of survival was 77%: four of the five deaths were attributed to fusariosis, all in patients with relapsed/refractory acute leukemias. Ninety-day probability of survival for patients with relapsed/refractory underlying malignancy was 33% vs. 94% in others (p < 0.001). Survival rates in this largest pediatric population-based study were strikingly higher than those reported in adults, demonstrating that invasive fusariosis is a life-threatening but salvageable condition in immunosuppressed children.

Relapse of B-cell precursor acute lymphoblastic leukemia (BCP-ALL) may occur in the central nervous system (CNS). Most clinical trials of CAR T-cell therapy excluded patients with active CNS leukemia, partially for concerns of neurotoxicity. Here, we report an international study of fifty-five children and adolescents who received CAR T-cell therapy for relapsed BCP-ALL with CNS involvement at the time of referral. All patients received bridging therapy, 16 still having active CNS disease at the time of lymphodepletion. Twelve patients received CD28-based CAR T-cells, 9 being subsequently treated with allogeneic hematopoietic stem-cell transplantation (allo-HSCT). Forty-three patients received 4-1BB-based CAR T-cells. Cytokine-release syndrome (CRS) and neurotoxicity occurred in 65% and 38% of patients, respectively, more frequently following treatment with CD28-based CARs. Fifty-one of 54 evaluable patients (94%) achieved complete response following this therapy. Relapse occurred in 22 patients: 19/43 following 4-1BB-based CARs (12 CNS relapses), and 3/12 after CD28-based CARs with subsequent HSCT (no CNS relapse). Patients treated with tisagenlecleucel for an isolated CNS relapse had a high incidence of a subsequent CNS relapse (6 of 8). CAR T-cells were found to be effective in this cohort, though the risk of CNS relapse was not completely mitigated by this approach.

Neutrophils and their granular enzymes such as neutrophil elastase (NE) and myeloperoxidase (MPO) play important roles in inflammatory diseases, and might be utilized as biomarkers for disease severity and progression. The aim of this study was to determine reference intervals for NE and MPO activity in healthy volunteers comparing two methods of neutrophil isolation.Neutrophils were isolated using ficoll density gradient centrifugation or immunomagnetic negative selection in two separate volunteers' cohorts. Subsequently, cells were lysed and incubated with chromogens for NE and MPO activity measurements, then measured with a microplate reader at 415 or 450 nm respectively.The enzymatic activity of NE and MPO depended on the neutrophil isolation technique. Both enzymatic activities were significantly higher (P 0.001) after isolating neutrophils with ficoll density gradient centrifugation than using the immunomagnetic negative selection.We demonstrated that neutrophil isolation is an important factor that influences the outcome of enzymatic activity measurements. Techniques based on immunomagnetic negative selection are favorable, specifically for investigations related to NE and MPO activity. When using NE and MPO activity measurements in clinical practice, care must be taken to interpret the data depending on the applied cell isolation technique.

Prolonged cytopenias are a non-specific sign with a wide differential diagnosis. Among inherited disorders, cytopenias predisposing to leukemia require a timely and accurate diagnosis to ensure appropriate medical management, including adequate monitoring and stem cell transplantation prior to the development of leukemia. We aimed to define the types and prevalences of the genetic causes leading to persistent cytopenias in children. The study comprises children with persistent cytopenias, myelodysplastic syndrome, aplastic anemia, or suspected inherited bone marrow failure syndromes, who were referred for genetic evaluation from all pediatric hematology centers in Israel during 2016-2019. For variant detection, we used Sanger sequencing of commonly mutated genes and a custom-made targeted next-generation sequencing panel covering 226 genes known to be mutated in inherited cytopenias; the minority subsequently underwent whole exome sequencing. In total, 189 children with persistent cytopenias underwent a genetic evaluation. Pathogenic and likely pathogenic variants were identified in 59 patients (31.2%), including 47 with leukemia predisposing syndromes. Most of the latter (32, 68.1%) had inherited bone marrow failure syndromes, nine (19.1%) had inherited thrombocytopenia predisposing to leukemia, and three each (6.4%) had predisposition to myelodysplastic syndrome or congenital neutropenia. Twelve patients had cytopenias with no known leukemia predisposition, including nine children with inherited thrombocytopenia and three with congenital neutropenia. In summary, almost one third of 189 children referred with persistent cytopenias had an underlying inherited disorder; 79.7% of whom had a germline predisposition to leukemia. Precise diagnosis of children with cytopenias should direct follow-up and management programs and may positively impact disease outcome.

Mucormycosis has emerged as an increasingly important cause of morbidity and mortality in immunocompromised patients, but contemporary data in children are lacking. We conducted a nationwide multicentre study to investigate the characteristics of mucormycosis in children with haematological malignancies. The cohort included 39 children with mucormycosis: 25 of 1136 children (incidence 2·2%) with acute leukaemias prospectively enrolled in a centralized clinical registry in 2004-2017, and an additional 14 children with haematological malignancies identified by retrospective search of the databases of seven paediatric haematology centres. Ninety-two percent of mucormycosis cases occurred in patients with acute leukaemias. Mucormycosis was significantly associated with high-risk acute lymphoblastic leukaemia (OR 3·75; 95% CI 1·51-9·37; P = 0·004) and with increasing age (OR 3·58; 95% CI 1·24-9·77; P = 0·01). Fifteen patients (38%) died of mucormycosis. Rhinocerebral pattern was independently associated with improved 12-week survival (OR 9·43; 95% CI 1·47-60·66; P = 0·02) and relapsed underlying malignancy was associated with increased 12-week mortality (OR 6·42; 95% CI, 1·01-40·94; P = 0·05). In patients receiving frontline therapy for their malignancy (n = 24), one-year cumulative mucormycosis-related mortality was 21 ± 8% and five-year overall survival was 70 ± 8%. This largest paediatric population-based study of mucormycosis demonstrates that children receiving frontline therapy for their haematological malignancy are often salvageable.

Impaired neutrophil extracellular trap (NET) formation compromises the host defense after engraftment following hematopoietic stem cell transplantation (HSCT) despite adequate neutrophil counts. The aims of the present study were to determine reference ranges for the activity of key enzymes of NET formation—neutrophil elastase (NE) and myeloperoxidase (MPO)—in a healthy population and to unravel the recovery dynamics of NET formation over time following HSCT, along with NE and MPO enzymatic activities. Reference ranges of NE and MPO activity were derived from 50 healthy volunteers. During 2017 to 2018, 11 consecutive pediatric patients undergoing allogeneic or autologous HSCT were recruited at a single referral center for pediatric hemato-oncology. Patients were followed for up to 1 year following engraftment. The mean reference value was 7.5 ± .4 mU for NE activity and 2.17 ± .4 U for MPO activity in the healthy population, and enzymatic activity of MPO was significantly higher in males. At 3 weeks following neutrophil engraftment, all study participants demonstrated extremely low enzymatic NE activity, whereas MPO activity was above the lower normal reference range at all time points. Reduced NE activity corresponded to the inability to form NETs. Neutrophil function improved over time, but partial impairment persisted for 7 months following transplantation. The ability of neutrophils to form NETs was significantly impaired for 3 weeks after engraftment in the setting of HSCT, exposing patients to bacterial infections. NE activity might serve as a surrogate marker for the capacity of neutrophils to form NETs.

Background Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is a progressive autosomal recessive disorder characterized by cachexia, gastrointestinal (GI) dysmotility, ptosis, peripheral neuropathy, and brain magnetic resonance imaging (MRI) white matter changes. Bi-allelic TYMP mutations lead to deficient thymidine phosphorylase (TP) activity, toxic accumulation of plasma nucleosides (thymidine and deoxyuridine), nucleotide pool imbalances, and mitochondrial DNA (mtDNA) instability. Death is mainly due to GI complications: intestinal perforation, peritonitis, and/or liver failure. Based on our previous observations in three patients with MNGIE that platelet infusions resulted in a transient 40% reduction of plasma nucleoside levels, in 2005 we performed the first hematopoietic stem cell transplantation (HSCT) worldwide as a life-long source of TP in a patient with MNGIE. Procedure HSCT was performed in a total of six patients with MNGIE. The multiple factors involved in the prognosis of this cohort were analyzed and compared to the literature experience. Results Cell source was bone marrow in five patients and peripheral stem cells in one, all from fully human leukocyte antigen (HLA)-matched related donors, including four who were TYMP mutation carriers. Four of six (66%) survived compared to the 37% survival rate in the literature. Reduced intensity conditioning regimen contributed to secondary graft failure in two patients. Fifteen years post HSCT, the first transplanted patient is seemingly cured. Severe GI symptoms before transplantation were mostly irreversible and were poor prognostic factors. Conclusions Allogenic HSCT could constitute a curative therapeutic option for carefully selected, young, presymptomatic, or mildly affected patients. Timing, donor selection, and optimal conditioning protocol are major determinants of outcome. HSCT is inadvisable in patients with advanced MNGIE disease.

Background: Mucormycosis is a life-threatening infection with a tendency for angioinvasion that may lead to progressive dissemination. Disseminated mucormycosis, defined as the involvement of two or more non-contiguous sites, is rare in children, and data concerning its management and outcome are scarce. The aim of this study was to assess the contemporary management strategies and outcomes of disseminated mucormycosis in the pediatric population. Methods: We conducted a retrospective search in six large tertiary medical centers for all cases of disseminated mucormycosis that occurred between 2009–2020 in patients aged 1–20 years. Results: Twelve cases were identified. Underlying conditions included hematological malignancies (n = 10), solid tumor (post-autologous hematopoietic stem cell transplantations, n = 1), and solid organ (liver) transplantation (n = 1). In all cases, amphotericin B formulations were administered as first-line therapy, in eight cases, they were also administered in combination with an echinocandin or triazole. Seven patients underwent surgical debridement procedures. The six-week mortality was 58%. Among the patients diagnosed between 2009–2015, one of the six survived, and of those diagnosed between 2016–2020, four of the six were salvaged. Conclusions: Disseminated mucormycosis is a life-threatening and often fatal disease, and improved diagnostic and therapeutic strategies are needed. Nevertheless, in this population-based study, five patients (42%) were salvaged through combined liposomal amphotericin/triazole treatment and extensive surgical interventions.

INTRODUCTION: Intramedullary spinal cord high grade gliomas are rare pediatric tumors , with a grim prognosis. Current therapeutical strategies include a surgical resection if feasible, and radiotherapy. Additional treatments with various chemotherapy agents have had a minor effect and did not change the course of the disease. New molecular targets are a source of hope. Recent molecular evidence regarding high grade infantile hemispheric gliomas describe specific tyrosine kinase receptor fusions or mutations in ALK, ROS, NTRK and MET domains which may lead to therapeutical targets. There is no data regarding these molecular changes in infantile intramedullary high grade gliomas. We present a two year old girl with a cervical high grade glioma with an ALK mutation which received targeted therapy. CASE REPORT: A two year old girl presented with progressive torticollis and hemiparesis. An intramedullary cervical tumor with ill -defined borders was diagnosed. A limited partial excision was performed and the pathological diagnosis was high grade glioma. Within weeks she developed progressive clinical and radiological deterioration. Molecular studies (Oncomine) revealed an ALK fusion (KIF5B) which was confirmed by immunohistochemistry. Treatment with ALK inhibitor alectinib at 150mg daily was initiated. Torticollis resolved within a week, and MRI after 3 months showed outstanding tumor shrinkage with a small residual mass. There were no adverse events to treatment. DISCUSSION: ALK fusion positive high grade glioma has recently been recognized in infants with hemispheric tumors, and a preliminary recent case report demonstrated excellent response to ALK inhibitors. Intramedullary spinal cord high grade gliomas are rare and harbor poor prognosis. This is the first case of ALK fusion glioma of the spine with excellent preliminary response to alectinib. The duration of treatment and long term prognosis is unknown. Molecular investigations can change the approach to pediatric rare CNS tumors.

INTRODUCTION: Current chemotherapy protocols for treatment of embryonal brain tumors in infants recommend administration of intrathecal chemotherapy either by a lumbar tap or via an Ommaya reservoir. Children with concurrent hydrocephalus and shunts may have sub-therapeutic levels of chemotherapy in the CSF due to constant CSF drainage to extra-CNS compartments. We present our experience in delivery of chemotherapy to young children via programmable valves. RESULTS: A retrospective analysis of infants with CNS malignancies and hydrocephalus treated with a shunt and a programmable valve (CERTAS™ Plus Programmable Valves - Integra Life Sciences) was conducted. Five infants 1.1-3 years of age (mean 2) were included. Pathologies included atypical teratoid rhabdoid tumor (ATRT N=2), medulloblastoma (N=2), and metastatic rhabdomyosarcoma(N=1). Intrathecal injections were conducted in an outpatient setting unless hospitalization was required for other reasons. Only one child required sedation due to noncompliance. A total of 61 chemotherapeutic administrations were performed directly through the valve while set on an extremely high opening pressure for several hours( 35 with hydrocortisone and cytarabine, 26 with topotecan). There were no infections, leaks or major complications. One child required a wound revision due to exposure of the proximal catheter related to extremely thin skin, one child developed somnolence and fever which were not related to a shunt malfunction or infection, and one child had clinical and radiological shunt over-drainage solved by increasing of valve settings. CONCLUSIONS: Programmable ventriculoperitoneal valves appear to a safe method for delivery of chemotherapy in infants with malignant CNS tumors .This technique may potentially have an added value for children with concurrent shunts, and may also obviate the need for an additional ventricular access device .

Mucositis, a painful and debilitating condition, is a common side effect of chemotherapy. The role of tramadol in the treatment of mucositis in pediatric patients has not yet been determined. In this retrospective study, we evaluate whether tramadol as single agent achieved a reduction of pain intensity among oncologic children admitted for mucositis. In total, 34 of 54 (63%) episodes were treated with tramadol alone and achieved adequate pain relief. Tramadol's side effects were mild and manageable.

Venous thromboembolism (VTE) is a serious complication of acute lymphoblastic leukemia (ALL) therapy. The aim of this population-based study was to evaluate the rate, risk factors, and long-term sequelae of VTE in children treated for ALL. The cohort included 1191 children aged 1&ndash, 19 years diagnosed with ALL between 2003&ndash, 2018, prospectively enrolled in two consecutive protocols: ALL-IC BFM 2002 and AIEOP-BFM ALL 2009. VTEs occurred in 89 patients (7.5%). Long-term sequelae were uncommon. By univariate analysis, we identified four significant risk factors for VTEs: Severe hypertriglyceridemia (p = 0.005), inherited thrombophilia (p &lt, 0.001), age &gt, 10 years (p = 0.015), and high-risk ALL group (p = 0.039). In addition, the incidence of VTE was significantly higher in patients enrolled in AIEOP-BFM ALL 2009 than in those enrolled in ALL-IC BFM 2002 (p = 0.001). Severe VTE occurred in 24 children (2%), all of whom had at least one risk factor. Elevated triglyceride levels at diagnosis did not predict hypertriglyceridemia during therapy. In a multivariate analysis of 388 children, severe hypertriglyceridemia and inherited thrombophilia were independent risk factors for VTE. Routine evaluation for these risk factors in children treated for ALL may help identify candidates for intervention.

Background Infantile myofibromatosis (IM) is a rare benign fibrous tumor with diverse clinical presentations and treatments, such as watchful waiting, surgical excision, and low-dose chemotherapy. Procedure Clinical presentation and tailored treatment of five infants with solitary and generalized IM are described, together with a review of the literature. Results Three patients underwent total-body magnetic resonance imaging (MRI) at diagnosis and during follow up, which revealed disease extension that aided in designing treatment. Visceral involvement included central nervous system, cardiac, gastrointestinal, muscle, bone, and subcutaneous tissue lesions. The patient with the solitary form of IM was followed up without treatment and had spontaneous improvement. Patients with the multicentric form received intravenous low-dose methotrexate and vinblastine chemotherapy. One patient who received oral methotrexate due to cardiac involvement and unfeasible central line access had excellent results. Recurrence was successfully treated by the same methotrexate and vinblastine regimen as that administered at diagnosis. Conclusions We suggest screening all patients with one or more IM lesions by means of total body MRI due to its inherent superior soft tissue resolution. Total-body MRI may also be used for routine follow up. Oral methotrexate can be administered successfully in patients that lack central line access, and recurrent lesions can be treated with the same chemotherapeutic combination as that given at diagnosis. Long-term follow up is needed, since recurrence could appear years after initial presentation of the disease.

Neutrophil extracellular traps (NETs) are fibers composed of chromatin and neutrophil proteins released by activated neutrophils. NETs trap and kill microbes, activate dendritic and T cells, and are implicated in autoimmune and vascular diseases. The pathogenesis of inflammatory bowel disease (IBD) is multifactorial and characterized by chronic active mucosal inflammation with controversial contribution of neutrophils. Our aim is to describe the involvement of NETs in pediatric IBD. We retrospectively examined biopsies from the small bowel and colon of children at diagnosis of Crohn's disease (CD) or ulcerative colitis (UC). The biopsies were labeled for neutrophil elastase, myeloperoxidase, DNA, chromatin and histones in order to identify NETs. Samples of two children with normal colonoscopy served as controls. Twelve patients (5 boys) were included, 6 with CD and 6 with UC. Their average age was 12.2 years (range 5-16). NETs were found in all samples from patients and not in the samples from the two controls. This is the first demonstration of the presence of NETs in biopsies taken from the small bowel and colon of pediatric patients with IBD. More studies are needed in order to identify the role of NETs in CD/UC pathogenesis.

Immunocompromised patients exposed to varicella may experience significant morbidity and a 7% mortality rate. Management and outcome of an outbreak of varicella infection among hospitalized pediatric hemato-oncology patients using the guidelines of the American Academy of Pediatrics Committee on Infectious Diseases are presented.This retrospective study describes an outbreak of varicella infection between February 2011 and June 2011. Data were retrieved from the patients' files. Positive polymerase chain reaction results for varicella zoster virus from vesicular skin lesions were used for the diagnosis of varicella infection.Twelve pediatric hemato-oncology patients experienced 13 episodes of varicella infection, 11 underwent 1 episode each and 1 patient had 2 episodes. All exposed patients without immunity received varicella zoster immune globulins or intravenous immunoglobulin and were isolated as recommended by the guidelines. Infected patients received intravenous acyclovir. One patient with acute lymphoblastic leukemia at induction chemotherapy died. All the other patients survived.Our experience in the management of hospitalized immunocompromised patients exposed to varicella was that a positive IgG serology did not confer protection after exposure to varicella infection and thus can not serve as a marker for immunity. Unlike the isolation period sufficient for immunocompetent patients, crusted lesions can be contagious and thus require extended isolation for immunocompromised patients. Patients receiving rituximab are at greater risk of having persistent or recurrent disease. Studies with a larger sample size should be performed to better assess the management of immunocompromized patients exposed to varicella.

Data on the production of neutrophil extracellular traps (NETs) in leukemia patients are scant. Phagocytosis, hydrogen peroxide, neutrophil elastase and myeloperoxidase enzymatic activity as well as NETs formation were studied in 10 pediatric acute lymphoblastic leukemia and 7 pediatric acute myeloid leukemia (AML) patients after induction chemotherapy. Median neutrophil elastase activity and NETs formation were lower in AML versus acute lymphoblastic leukemia (41% vs. 90%, P=0.005 and 51% vs. 94%, P=0.008, respectively). AML patients had more episodes of febrile neutropenia during the first 2 blocks of treatment (100% vs. 40%, P=0.011) and a trend for more invasive bacterial and fungal infections.

BACKGROUND Therapy outcomes for childhood acute lymphoblastic leukemia (ALL) had substantially improved in the last decades, but variability across racial and ethnic groups was identified in some clinical studies. In this study, we aimed to investigate whether such a difference in outcome is found in the diverse ethnicities in Israel as well. METHODS A retrospective study was conducted among 1154 patients (855 Jews, 195 Muslims, 52 Bedouins, 26 Druze, and 26 others) aged 1 to 21 years, who were diagnosed with ALL between 1989 and 2011 and were treated according to the same Berlin-Frankfurt-Muenster-based Israel National Study protocols. RESULTS Bedouins had a higher incidence of t(1;19) (16% vs 3% for non-Bedouins) and a lower incidence of high-hyperdiploidy (10% vs 25% for non-Bedouins) (P = 0.01). Five-year event-free survival (EFS) and overall survival (OS) were poorer for the Bedouins (60.3% ± 7.2% and 63.1% ± 7.2%, respectively) compared with the Jews, Muslims, and Druze (80.4% ± 1.4%, 77.3% ± 3.2%, and 84% ± 7.3%, respectively, for EFS [P = 0.02], and 86.3% ± 1.2%, 82.3% ± 2.9%, and 88.3% ± 6.4%, respectively, for OS [P = 0.002]). Adherence to intensive chemotherapy was similar between the Muslims and the Bedouins. CONCLUSIONS Our findings suggest that the Bedouins, a highly inbred ethnic Arab people, may be considered a higher risk group that may need more intensive chemotherapy and/or supportive care in order to improve their outcome.

Purpose Recurrent glioblastoma multiforme (GBM) is incurable with current therapies. Biallelic mismatch repair deficiency (bMMRD) is a highly penetrant childhood cancer syndrome often resulting in GBM characterized by a high mutational burden. Evidence suggests that high mutation and neoantigen loads are associated with response to immune checkpoint inhibition. Patients and Methods We performed exome sequencing and neoantigen prediction on 37 bMMRD cancers and compared them with childhood and adult brain neoplasms. Neoantigen prediction bMMRD GBM was compared with responsive adult cancers from multiple tissues. Two siblings with recurrent multifocal bMMRD GBM were treated with the immune checkpoint inhibitor nivolumab. Results All malignant tumors (n = 32) were hypermutant. Although bMMRD brain tumors had the highest mutational load because of secondary polymerase mutations (mean, 17,740 ± standard deviation, 7,703), all other high-grade tumors were hypermutant (mean, 1,589 ± standard deviation, 1,043), similar to other cancers that responded favorably to immune checkpoint inhibitors. bMMRD GBM had a significantly higher mutational load than sporadic pediatric and adult gliomas and all other brain tumors (P < .001). bMMRD GBM harbored mean neoantigen loads seven to 16 times higher than those in immunoresponsive melanomas, lung cancers, or microsatellite-unstable GI cancers (P < .001). On the basis of these preclinical data, we treated two bMMRD siblings with recurrent multifocal GBM with the anti–programmed death-1 inhibitor nivolumab, which resulted in clinically significant responses and a profound radiologic response. Conclusion This report of initial and durable responses of recurrent GBM to immune checkpoint inhibition may have implications for GBM in general and other hypermutant cancers arising from primary (genetic predisposition) or secondary MMRD.

PB is a source of HSC, especially for autologous HCT in solid tumors. However, there is a risk of failing to achieve the target number of SC after mobilization with growth factors alone in patients who were heavily pretreated with chemotherapy or those in need for tandem transplants. SC were harvested from seven pediatric patients with solid tumors who were in need of autologous HCT following combination GCSF and plerixafor. Six of them received plerixafor after failing to achieve enough SC with GCSF only, while the seventh patient received the combined protocol upfront. All seven patients achieved the target number of SC according to their treatment protocol. There were no adverse events. All patients underwent autologous HCT using the harvested HSC and achieved full engraftment. A protocol for harvesting autologous HCT using GCSF and plerixafor is feasible and safe in children with solid tumors who had been heavily pretreated with chemotherapy or needed tandem transplants.

Hereditary biallelic mismatch repair deficiency (BMMRD) is caused by biallelic mutations in the mismatch repair (MMR) genes and manifests features of neurofibromatosis type 1, gastrointestinal (GI) polyposis, and GI, brain, and hematological cancers. This is the first study to characterize the GI phenotype in BMMRD using both retrospective and prospective surveillance data.The International BMMRD Consortium was created to collect information on BMMRD families referred from around the world. All patients had germline biallelic MMR mutations or lack of MMR protein staining in normal and tumor tissue. GI screening data were obtained through medical records with annual updates.Thirty-five individuals from seven countries were identified with BMMRD. GI data were available on 24 of 33 individuals (73%) of screening age, totaling 53 person-years. The youngest age of colonic adenomas was 7, and small bowel adenoma was 11. Eight patients had 19 colorectal adenocarcinomas (CRC; median age 16.7 years, range 8-25), and 11 of 18 (61%) CRC were distal to the splenic flexure. Eleven patients had 15 colorectal surgeries (median 14 years, range 9-25). Four patients had five small bowel adenocarcinomas (SBC; median 18 years, range 11-33). Two CRC and two SBC were detected during surveillance within 6-11 months and 9-16 months, respectively, of last consecutive endoscopy. No patient undergoing surveillance died of a GI malignancy. Familial clustering of GI cancer was observed.The prevalence and penetrance of GI neoplasia in children with BMMRD is high, with rapid development of carcinoma. Colorectal and small bowel surveillance should commence at ages 3-5 and 8 years, respectively.

The urea cycle (UC) is the main pathway by which mammals dispose of waste nitrogen. We find that specific alterations in the expression of most UC enzymes occur in many tumors, leading to a general metabolic hallmark termed "UC dysregulation" (UCD). UCD elicits nitrogen diversion toward carbamoyl-phosphate synthetase2, aspartate transcarbamylase, and dihydrooratase (CAD) activation and enhances pyrimidine synthesis, resulting in detectable changes in nitrogen metabolites in both patient tumors and their bio-fluids. The accompanying excess of pyrimidine versus purine nucleotides results in a genomic signature consisting of transversion mutations at the DNA, RNA, and protein levels. This mutational bias is associated with increased numbers of hydrophobic tumor antigens and a better response to immune checkpoint inhibitors independent of mutational load. Taken together, our findings demonstrate that UCD is a common feature of tumors that profoundly affects carcinogenesis, mutagenesis, and immunotherapy response.

This study investigated the prevalence of inherited thrombophilia, risk of venous thromboembolism (VTE) and benefit of low molecular weight heparin prophylaxis in 476 Israeli children with acute lymphoblastic leukaemia (ALL) treated between 2004 and 2016. Thrombophilia was found in 15·5%. Arab children had a higher prevalence of F5 R506Q (factor V Leiden) than Jewish children (19·4% vs. 2·9%, P < 0·01). Patients with thrombophilia had higher VTE rates VTE (26·5% vs. 5·6%, P < 0·001). None of the thrombophilic children given prophylaxis had severe VTE. Routine evaluation for inherited thrombophilia followed by thromboprophylaxis when findings are positive may benefit at-risk patients with ALL.

Neutrophil extracellular traps (NETs) are fibers composed of chromatin and neutrophil proteins released by activated neutrophils. NETs trap and kill microbes, activate dendritic and T cells, and are implicated in autoimmune and vascular diseases. The pathogenesis of inflammatory bowel disease (IBD) is multifactorial and characterized by chronic active mucosal inflammation with controversial contribution of neutrophils. Our aim is to describe the involvement of NETs in pediatric IBD. We retrospectively examined biopsies from the small bowel and colon of children at diagnosis of Crohn's disease (CD) or ulcerative colitis (UC). The biopsies were labeled for neutrophil elastase, myeloperoxidase, DNA, chromatin and histones in order to identify NETs. Samples of two children with normal colonoscopy served as controls. Twelve patients (5 boys) were included, 6 with CD and 6 with UC. Their average age was 12.2 years (range 5-16). NETs were found in all samples from patients and not in the samples from the two controls. This is the first demonstration of the presence of NETs in biopsies taken from the small bowel and colon of pediatric patients with IBD. More studies are needed in order to identify the role of NETs in CD/UC pathogenesis.

Germline biallelic mismatch repair deficiency (bMMRD) results in a unique cancer predisposition syndrome in which the affected children are susceptible to the development of malignancies, especially brain, gastrointestinal, and lymphoid cancers. Acute myeloblastic leukemia is rarely reported in this syndrome. Here we report the decision-making challenges in a bMMRD child with acute myeloblastic leukemia. Our experience should alert physicians to include bMMRD in the differential diagnosis of a child with hyper/hypopigmented spots and leukemia. Furthermore, the presence of the above and consanguinity emphasizes the need to rule out bMMRD when an allogeneic bone marrow transplant is considered and to enable the surveillance of other family members for earlier detection of cancers in these children.

DNA replication-associated mutations are repaired by two components: polymerase proofreading and mismatch repair. The mutation consequences of disruption to both repair components in humans are not well studied. We sequenced cancer genomes from children with inherited biallelic mismatch repair deficiency (bMMRD). High-grade bMMRD brain tumors exhibited massive numbers of substitution mutations (>250/Mb), which was greater than all childhood and most cancers (>7,000 analyzed). All ultra-hypermutated bMMRD cancers acquired early somatic driver mutations in DNA polymerase ɛ or δ. The ensuing mutation signatures and numbers are unique and diagnostic of childhood germ-line bMMRD (P < 10(-13)). Sequential tumor biopsy analysis revealed that bMMRD/polymerase-mutant cancers rapidly amass an excess of simultaneous mutations (∼600 mutations/cell division), reaching but not exceeding ∼20,000 exonic mutations in

Numerous adults' studies demonstrated that preaphaeresis CD34+ cells significantly correlate with the number of CD34+ cells collected by the aphaeresis procedure. Equivalent studies in children are scarce. We studied retrospectively 92 aphaeresis procedures performed following chemotherapy (44) or in steady state (48) in 60 pediatric patients (40 males, 20 females), median age of 7.5 years. Aphaeresis procedures were performed using a SPECTRA Optica (TERUMOBCT) continuous flow cell separator. CD34+ cell concentrations were assessed using flow cytometry. A highly significant correlation between peripheral CD34 cell count on the day of aphaeresis and CD34 cell yield per kg (R2 = .824, P

BACKGROUND Chronic disseminated candidiasis (CDC) is a severe invasive fungal infection principally observed during neutrophil recovery in patients with acute leukemia treated with intensive chemotherapy. Its pathophysiology remains unclear. We describe the management of 6 children with symptomatic CDC who did not respond to antifungal therapy. METHODS The databases of the hematology-oncology departments of 2 tertiary pediatric medical centers were searched for all patients diagnosed with CDC from 2003 to 2015, who responded to corticosteroids after failing antifungal therapy. Clinical, laboratory and radiologic data were collected. RESULTS Six patients (3 women, 3 men; 9-18 years of age) met the study criteria. Underlying diseases were acute lymphoblastic leukemia (n = 3) and large B-cell lymphoma, acute myeloid leukemia and severe aplastic anemia (n = 1 each). Presenting symptoms/signs of CDC were fever in all cases, with abdominal or chest pain, and/or mucositis. Candida infection was identified in blood cultures in 4 patients and in bronchoalveolar lavage fluid in one. In the absence of response to antifungal agents (4-50 days from CDC diagnosis), prednisone 2 mg/kg/day or equivalent was administered. CDC-attributable clinical symptoms resolved in 4 patients within 6-19 days; one patient required an additional nonsteroidal anti-inflammatory agent. Abnormalities on imaging decreased or disappeared within 5 months to 2 years in 4 patients. CONCLUSIONS In children with persistent symptomatic CDC, despite adequate antifungal therapy, administration of corticosteroids may yield rapid resolution of symptoms and decreased inflammatory markers. In patients who do not respond to steroids, the addition of a nonsteroidal anti-inflammatory drug should be considered.

Background. Hematopoietic stem cell transplantation (HSCT) remains the only curative treatment for many nonmalignant disorders, such as autoimmune disorders, inborn metabolic disorders, hemoglobinopathies, and immunodeficiency disorders. Autoimmune complications (AICs) after HSCT, such as autoimmune cytopenias, autoimmune hepatitis, primary biliary cirrhosis, and autoimmune cutaneous manifestations, are still neither well defined nor characterized.Patients. Between 2000 and 2012, 92 patients (47 males, 45 females) were treated with HSCT in our hospital, 51 with congenital hemoglobinopathies, 19 with primary immunodeficiency disease, 10 with metabolic disorders, five with Fanconi anemia, three with aplastic anemia, and four with familial hemophagocytic lymphohistiocytosis.Results. Mean age at HSCT was 6.4 years (range, 0.2–32 years) and mean duration of followup after HSCT was 6.81 years (range, 1–11 years). Sixteen (17.4%) patients developed chronic GVHD and five (5.4%) showed sclerodermatous features. Five (5.4%) patients were diagnosed with scleroderma manifestations, six (6.5%) with vitiligo, six (6.5%) with autoimmune hemolytic anemia (AIHA), six (6.5%) with idiopathic thrombocytopenia, three (3.3%) with mild leucopenia, two (2.2%) with aplastic anemia, two (2.2%) (one boy, one girl) with autoimmune thyroid disease, and one (1.1%) with autoimmune hepatitis.Conclusions. It was concluded that AICs are clinically significant complications after HSCT that contribute to morbidity but not to mortality. AICs are more frequent after HSCT for metabolic disorders, and sclerodermatous GVHD is more significant in children who underwent allogeneic HSCT for hemoglobinopathies. The potential to identify risk factors for AICs could lead to less morbidity and mortality and to maintain the patient’s quality of life.

Background As cord blood (CB) is being used frequently as a source for heamtopoetic stem cell transplantation defining risk factors for transplantation outcome is an important issue. Procedure The data of all single unit CB transplantation preformed in Israel from 1992 to 2011 were collected. The risk factors for myeloid engraftment, event free survival (EFS) and overall survival (OS) were studied in 87 children. Results There were 49 children with hematological malignancies and 38 with non-malignant diseases. Cumulative rate of neutrophil recovery was 78.3%, while median time to myeloid recovery was 26 days. The incidence of platelet engraftment at 150 days was 53%, and the median time to platelet recovery was 36 days. ABO blood group matching between CB unit and recipient was associated with superior myeloid engraftment. Acute graft versus host disease of grades II–IV occurred in 33% of the patients. Chronic graft versus host disease occurred in 16% of patients. Probabilities of EFS and OS at 1 year were 45% and 57%, respectively. Factors associated with inferior OS were Rh major mismatch versus matched Rh and transplantation from unrelated donor versus related donor. Conclusions These results indicate that matching of ABO blood groups is an important factor that affects engraftment, and also that Rh matching seem to have an impact on OS, which was not previously described in the setting of CB transplantation. Pediatr Blood Cancer 2013;60:2007–2011. © 2013 Wiley Periodicals, Inc.

Background Many survivors of pediatric brain tumors (SPBTs) suffer from long-term late effects (LEs). Our aim was to create a practical screening tool for detecting LEs in this population. Such a screening tool will improve our ability to identify those patients who may benefit from treatment in LE clinics while focusing on individual relevant issues. Procedure We developed the Treatment-Oriented Screening Questionnaire (TOSQ); a self-reported, risk-based questionnaire that addresses all LEs SPBTs can potentially suffer. As a basis for the TOSQ design we used the Long-Term Follow-Up Guidelines published by the Children's Oncology Group. Output includes individual recommendations for further treatment. We prospectively assessed whether the TOSQ can accurately detect treatment targets in SPBTs by comparing patient and caregiver questionnaire scores with physician evaluations. Data are presented from 41 SPBTs. Results The TOSQ is a precise screening tool for identifying LEs in SPBTs based on the significant correlation (P

Spontaneous remission in 2 children with myelofibrosis, one with megakaryocytic acute myeloblastic leukemia and t(1;22) (with recurrence later) and one with Down syndrome and GATA1 mutation (permanent), are described. One had sepsis and was treated with antibiotics and blood products, whereas the other received only blood products. Remission was spontaneous, without chemotherapy treatment. Possible explanations for these outcomes include immunologic response to sepsis by a leukemia-specific T-cell response or the release of various cytokines, such as tumor necrosis factor and interleukin-2, during infections. Natural killer and cytotoxic T cells transfused with blood products might have also triggered an immune response.

Hematopoietic stem cell transplantation (HSCT) remains the only potentially curative treatment for severe hemoglobinopathy (HGP). Late complications (LCs) are all events occurring beyond two years post-HSCT. We retrospectively analyzed prevalence, factors influencing occurrence, and prognosis of LCs post-HSCT for HGP.Between 2000 and 2011, 47 patients (21 males, 26 females; 43 with beta thalassemia major, four with sickle cell disease) who had survived more than two years post-HSCT for HGP were retrospectively reviewed. Mean age at HSCT was 7.7 years (1.1-32 years); mean follow-up was 7.1 years (2-11.6 years); 11 patients were splenectomized; mean ferritin level was 3022 ng/mL (350-10900); and seven patients underwent a second HSCT.Endocrinological complications were observed with primary gonadal failure in 16/20 mature females and 4/11 mature males, in five patients with primary hypothyroidism and in four with insulin-dependent diabetes mellitus (DM). Skeletal complications were observed in 10 with secondary osteoporosis; 22 patients had elevated transaminase levels; two had hepatitis B reactivation. Neurological, cardiac and ocular manifestations were relatively rare. A higher incidence of LCs was observed in splenectomized than in nonsplenectomized patients: cGVHD -64% versus 13% (P = .003); endocrine abnormalities -91% versus 30.5%, (P = .001); elevated transaminase levels -73% versus 33% (P = .043); mortality -18% versus 2.7% (NS).LCs post-HSCT for HGP are common and heterogeneous. Etiology is multifactorial with iron overload (IO), class, splenectomy, age, chronic GVHD, and corticosteroid (CS) treatment. Our data may help build follow-up guidelines to limit, detect, and treat any LCs and improve quality of life.

In this issue of Blood , [Gluckman et al][1] confirm the role of HLA identical sibling transplantation in sickle cell disease (SCD) with a 5-year overall survival of 95% when performed at an early age (

Apoptosis related protein in TGF-β signaling pathway (ARTS/septin 4 isoform 2) hereforth referred to as ARTS, was originally found to promote apoptosis induced by TGF-β, but later was shown to promote apoptosis induced by a wide variety of apoptotic stimuli. In vivo and in vitro studies revealed that ARTS-induced apoptosis is mainly executed through direct binding and antagonizing XIAP. High levels of XIAP are found in many types of cancers and often correlate with poor prognosis. ARTS was shown to function as a tumor-suppressor protein in human patients and mouse-tumor models. In particular, Septin 4/ARTS-deficient mice have increased tumor susceptibility and contain increased numbers of stem cells (SCs) and progenitor cells, apparently owing to their resistance towards apoptosis. Based on these results we propose that loss of proapoptotic ARTS may act as the ‘first hit’ initiating tumorigenesis in two distinct ways. First, loss of ARTS-mediated apoptosis leads to increased numbers of normal SCs. Elevated numbers of normal SCs may lead to increased cancer risk due to higher numbers of cellular targets available for transforming mutations. Second, after these SCs acquire additional transforming mutations and become cancer SC (CSCs), they are more likely to survive in the absence of ARTS owing to increased resistance toward apoptosis. A combination of these two mechanisms, over time, is expected to significantly increase tumor risk. Because CSCs appear to share phenotypic markers with normal SCs, targeting the signaling pathways that affect normal SC development and maintenance can serve as a useful approach towards true eradication of cancer. In this article we describe the role of ARTS in apoptosis and cancer, with focus on its potential role as a CSC marker and as a potential target for anticancer and anti-CSC therapy.

We retrospectively evaluated neutrophil engraftment kinetics in 29 single versus nine double unit cord blood transplants (CBTs). All single CBTs were performed in pediatric patients (non-malignant/malignant diseases, 19/10), while all double CBTs were performed in adults (n = 8) and an adolescent (n = 1) with hematological malignancies. Median follow-up time was 2.3 years (range, 0.1-13.5 years). Engraftment was achieved in 69% and 89% of the single and double cord blood (CB) groups, respectively. Similarly, median day of engraftment was not different for the single versus the double CBTs, at 19 and 23 days, respectively, and the neutrophil engraftment kinetics was similar in the two groups. Our data indicate that adults without sufficient nucleated cell doses in a single CB unit may receive two units with similar engraftment kinetics to those of children receiving only a single unit.

Heparanase is an endo-beta D-glucuronidase capable of cleaving heparan sulfate side chains, yielding heparan sulfate fragments. Heparanase activity has been correlated with the metastatic potential of tumor-derived cells, angiogenesis, autoimmunity and inflammation. We performed a study of heparanase expression in specimens obtained from patients with Langerhans cell histiocytosis (LCH). Paraffin embedded slides from 25 patients were studied by immunohistochemistry for heparanase. Most patients had positive staining for heparanase (21/25). There was no positive association with severity of disease and other clinical characteristics. Further studies are required to clarify the role of heparanase in the pathogenesis of LCH. Pediatr Blood Cancer 2014; 61:1883–1885. © 2014 Wiley Periodicals, Inc.

Mucormycosis has emerged as an increasingly important infection in patients with hematological malignancies, and is associated with considerable morbidity and mortality. However, contemporary data concerning epidemiology and outcome in children is lacking. Here we report a nationwide multicenter study of mucormycosis among children with hematological malignancies. Between the years 2004-2017, 1136 Israeli children aged ≤18 years with acute leukemias (acute lymphoblastic leukemia (ALL)-941; acute myeloid leukemia (AML)-195) were prospectively enrolled on a centralized clinical registry. Fungal infections, including mucormycosis, were prospectively and retrospectively captured. In addition, all 7 pediatric hematology centers were required to search hospital medical records, microbiology databases, and pathology information systems for cases of mucormycosis. Following central revision, 39 cases of mucormycosis were identified. Patient characteristics: Median age at mucor diagnosis: 13.5 years. Underlying diseases: ALL-27, AML-9, other-3. In 24 patients mucormycosis occurred during frontline therapy of their disease, and in 15 patients at relapse. Known risk factors included stem cell transplantation (SCT)-13 (33%), severe neutropenia-33 (85%) and corticosteroids-26 (67%). Among 20 patients on frontline ALL therapy, mucormycosis was diagnosed during induction in 13 cases, reinduction-6 cases, consolidation-1 case. Twenty-five patients with mucormycosis were enrolled on the national acute leukemia registry (not included: other malignancies, non-Israeli patients, relapsed leukemia with primary diagnosis preceding registry initiation, secondary AML). An analysis of registry cases demonstrated that the incidence of mucormycosis did not significantly increase during the study period. There was no seasonal clustering. Mucormycosis was significantly more common among patients ≥10 years old (4% vs 1%, p=0.004). Among patients on frontline treatment, mucormycosis was significantly more common in high-risk (HR) ALL patients (6%) than in non-HR (1%) or AML (1%) patients (p=0.001). Mucormycosis: Patterns of infection included sinusitis/sino-orbital-16 (41%), rhinocerebral-8 (21%), pulmonary-3 (8%), mandibular -4 (10%), gastrointestinal-1, cutaneous-1, otomastoiditis-1, disseminated-6 (15%). The majority (46%) were caused by Rhizopus spp. EORTC criteria: proven-30, probable-7, possible-2 (pathognomonic radiological findings and molecular diagnosis). Treatment: Nineteen patients were treated with amphotericin B formulations only and 19 received combined antifungal treatment. Nine patients received step-down treatment with posaconazole/ isavuconazole. In addition, 33 patients underwent surgical interventions, 26 underwent 2 procedures or more (range 2-14). Median time from presentation to antifungal treatment-3 days. Outcome: Twenty-one patients died, 15 of mucormycosis, 3 of other toxicities, 3 of leukemia. Factors significantly associated with mortality from mucormycosis were preceding SCT (p=0.01), less than 2 surgical interventions (p=0.0003) and relapsed disease (p=0.006). Eight-year OS of the whole cohort, those on frontline therapy and relapsed patients was 42% (±21%), 70%(±13%), 13%(±66%), respectively. Eight-year cumulative incidence of death from mucormycosis (CIDM) in those subgroups was 40%(±8), 21%(±8), 67% (±13), respectively. To our knowledge, this is the largest population-based study of mucormycosis in children with hematological malignancies. Our study demonstrates that mucormycosis is an age-dependent toxicity, significantly more common in patients ≥10 years of age. A striking finding was the high incidence of mucormycosis among patients on frontline high-risk ALL therapy, a fact which may reflect the increasing intensity of childhood ALL treatment. In a cohort of 24 patients who developed mucormycosis on frontline therapy, including 2 patients with AML and 13 with HR-ALL, 8y-OS was 70% and 8y-CIDM was 21%.The majority of patients in this cohort were salvageable through control of underlying disease, rapid instigation of antifungal treatment, and surgical debridement procedures, albeit in some cases at a price of mutilation and long-term sequelae. Future research should focus on the complex interactions between fungi and host, and on developing novel therapeutic strategies. Figure. Figure. Disclosures No relevant conflicts of interest to declare.

Immune checkpoint therapy leads to durable clinical responses in many cancer patients, but fails in others. To improve the clinical response to immunotherapy, it is highly important to identify predictive biomarkers. While checkpoint genes’ expression levels, tumor neo-antigen load and microsatellite instability (MSI) have been associated with enhanced response to checkpoint immunotherapies, they yet provide only a modest predictive signal and hence there is a need to identify additional predictive factors. Specifically, while there is growing evidence that metabolic alterations can affect the tumor and modulate the immune response, the potential effects of altered cancer metabolism on tumor mutagenesis and immunotherapy remain unexplored. The urea cycle (UC) converts excess nitrogen derived from the breakdown of nitrogen-containing molecules (e.g., ammonia) to urea, a relatively non-toxic and disposable nitrogenous compound. We and others have shown that silencing of the UC enzyme ASS1 promotes cancer proliferation by diverting its substrate aspartate toward CAD enzyme, which mediates the first three reactions in the pyrimidine synthesis pathway. We now demonstrate, by analysis of the TCGA data, tumor samples and cancer cell line experiments, that UC dysregulation (UCD) is a much wider common metabolic phenomenon that maximizes nitrogen utilization in cancer, favoring pyrimidine synthesis over urea disposal. Of note, while UCD is significantly associated with decreased cancer patient survival, the overall mutational load is not. Remarkably, we find that the UCD changes the 1:1 purine (R)-to-pyrimidine (Y) ratio in favor of pyrimidine in cancer cells. Moreover, in analysis of both TCGA data and UC perturbed cancer cells we find that: (a) UCD is significantly associated with a novel and unique pattern of purine-to-pyrimidine transversion mutational bias across many cancer types at the DNA coding (sense) strand, and (b) this trend becomes stronger and more significant at both the mRNA and protein levels, testifying to its functional implications. Notably, the overall mutational load in cancer is negatively correlated with UCD, testifying to their independence. To test whether the mutational bias is associated with better immunotherapy response, we analyze published data of three large melanoma cohorts. We find that responders of both anti-PD1 and anti-CTLA4 therapy exhibit significantly higher UCD and R->Y mutational bias than non-responders. We further observe that the peptides carrying transverse R->Y mutations are preferentially presented as neoantigens in responders independent of mutational load, and this trend becomes significant for more clonal neoantigens, promoting UCD as a potential biomarker for the success of immunotherapy. Finally, as nitrogen metabolites are excreted in the urine, we hypothesize that these changes may be detectable in urine of UCD-cancers. We observe increased levels of pyrimidine derived metabolites in the urine of mice bearing colon tumors associated with UCD in the tumors compared to normal intestine. In an analogous manner, we find significantly higher levels pyrimidine derived metabolites in the urine of human patients with prostate cancer compared to controls. Collectively, these results support our hypothesis that UCD is a prevalent metabolic phenomenon in cancer, generating mutational biased neo-peptides, worsening patients’ prognosis and yet enhancing the response to immune therapy independent of mutational load and MSI. Taken together, our findings point to the important role of UCD in a broad spectrum of cancers, to the potential use of UCD related metabolites as cancer biomarkers, and last but not least, to the role of UCD in predicting response to immune check point therapy. Broadly, our results suggest future therapeutic interventions aiming to increase UCD levels to enhance the coverage and efficiency of cancer immunotherapy. Citation Format: Joo Sang Lee, Narin Carmel, Hiren Karathia, Noam Auslander, Shiran Rabinovich, Rom Keshet, Noa Stettner, Alon Silberman, Lilach Agemy, Daniel Helbling, Raya Eilam, Qin Sun, Alexander Brandis, Hila Weiss, David Dimmock, Noam Stern-Ginossar, Avigdor Scherz, Igor Ulitsky, Sandesh CS Nagamani, Ronit Elhasid, Sridhar Hannenhalli, Eytan Ruppin, Ayelet Erez. Mutagenicity of urea cycle dysregulation and its implications for cancer immunotherapy [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2017 Oct 1-4; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2018;6(9 Suppl):Abstract nr A69.