Haematopoietic stem cell transplantation after reduced intensity conditioning in children and adolescents with chronic myeloid leukaemia: A prospective multicentre trial of the I-BFM Study Group.

This prospective multicentre trial evaluated the safety and the efficacy of a thiotepa/melphalan-based reduced intensity conditioning (RIC) haematopoietic stem cell transplantation (HSCT) in children and adolescents with chronic myeloid leukaemia (CML) in chronic phase (CP). Thirty-two patients were transplanted from matched siblings or matched unrelated donors. In 22 patients, HSCT was performed due to insufficient molecular response or loss of response to first- or second-generation tyrosine kinase inhibitor (TKI), with pretransplant BCR::ABL1 transcripts ranging between 0.001% and 33%. The protocol included a BCR::ABL1-guided intervention with TKI retreatment in the first year and donor lymphocyte infusions (DLI) in the second-year post-transplant. All patients engrafted. The 1-year transplant-related mortality was 3% (confidence interval [CI]: 0%-6%). After a median follow-up of 6.3 years, 5-year overall survival and event-free survival are 97% (CI: 93%-100%) and 91% (CI: 79%-100%) respectively. The current 5-year leukaemia-free survival with BCR::ABL1 <0.01% is 97% (CI: 88%-100%) and the current TKI- and DLI-free survival is 95% (CI: 85%-100%). The incidence of chronic graft-versus-host disease (GvHD) was 32%, being severe in four patients (13%). At last follow-up, 31 patients are GvHD-free and have stopped immunosuppression. RIC HSCT following pretreatment with TKI is feasible and effective in children and adolescents with CP-CML with an excellent disease-free and TKI-free survival.

A Need for a Novel Survival Risk Scoring System for Intensive Care Admissions Due to Sepsis in Pediatric Hematology/Oncology Patients.

Background: Children with hemato-oncological diseases or following stem cell transplantation (SCT) are at high risk for life-threatening infections; sepsis in this population constitutes a substantial proportion of pediatric intensive care unit (PICU) admissions. The current pediatric prognostic scoring tools to evaluate illness severity and mortality risk are designed for the general pediatric population and may not be adequate for this vulnerable subpopulation. Methods: Retrospective analysis was performed on all PICU admissions for sepsis in children with hemato-oncological diseases or post-SCT, in a single tertiary pediatric hospital between 2008 and 2021 (n = 233). We collected and analyzed demographic, clinical, and laboratory data and outcomes for all patients, and evaluated the accuracy of two major prognostic scoring tools, the Pediatric Logistic Organ Dysfunction-2 (PELOD-2) and the Pediatric Risk of Mortality III (PRISM III). Furthermore, we created a new risk-assessment model that contains additional parameters uniquely relevant to this population. Results: The survival rate for the cohort was 83%. The predictive accuracies of PELOD-2 and PRISM III, as determined by the area under the curve (AUC), were 83% and 78%, respectively. Nine new parameters were identified as clinically significant: age, SCT, viral infection, fungal infection, central venous line removal, vasoactive inotropic score, bilirubin level, C-reactive protein level, and prolonged neutropenia. Unique scoring systems were established by the integration of these new parameters into the algorithm; the new systems significantly improved their predictive accuracy to 91% (p = 0.01) and 89% (p < 0.001), respectively. Conclusions: The predictive accuracies (AUC) of the PELOD-2 and PRISM III scores are limited in children with hemato-oncological diseases admitted to PICU with sepsis. These results highlight the need to develop a risk-assessment tool adjusted to this special population. Such new scoring should represent their unique characteristics including their degree of immunosuppression and be validated in a large multi-center prospective study.

Therapeutic plasma exchange for neonatal hepatic failure.

We report a case of therapeutic plasma exchange in a neonate with fulminant liver failure. A six-day old, 2800-gram baby was referred to our medical center for evaluation and treatment of fulminant hepatic failure. The working diagnosis at admission was gestational alloimmune liver disease, and therapeutic plasma exchange was proposed. A double volume plasma exchange was successfully performed, using the Spectra Optia apheresis system, primed with packed red blood cells. Access was obtained via a radial artery catheter and a peripheral intravenous line. On hospital D-14 a diagnosis of E3 deficiency was confirmed, and disease-specific therapy was started. Automated TPE using peripheral arterial and venous catheters may be safely performed in neonates, and should be considered in the treatment of a variety of disorders including neonatal fulminant hepatic failure.

A multicenter report on the safety and efficacy of plerixafor based stem cell mobilization in children with malignant disorders.

BACKGROUND: Pleraxifor for peripheral blood stem cell (PBSC) mobilization in children with malignancies is often given following failure of standard mobilization (SM) rather than as a primary mobilizing agent. STUDY DESIGN AND METHODS: In this retrospective multicenter study, we report the safety of plerixafor-based PBSC mobilization in children with malignancies and compare outcomes between patients who received plerixafor upfront with SM (Group A) with those who received plerixafor following failure of SM (Group B). In the latter pleraxifor was given either following a low peripheral blood (PB) CD34 (<20 cells/cu.mm) (Group B1) or as a second collection process due to an unsuccessful yield (CD34 + < 2 × 106 /kg) (Group B2) following failed SM and first apheresis attempts. RESULTS: The study cohort (n = 47) with a median age of 8 (range 0.6-21) year, comprised 19 (40%) Group A and 28 (60%) Group B patients (B1 = 12 and B2 = 16). Pleraxifor mobilization was successful in 87.2% of patients, similar between Groups A and B (84.2% vs 89.2%) and resulted in a median 4-fold increase in PB CD34. Median number of apheresis attempts was 2 in Groups A and B1 but 4 in Group B2. In Group B2, median total CD34+ yield post-plerixafor was 9-fold higher than after SM (P = .0013). Mild to moderate transient adverse events affected 8.5% of patients. Among patients who proceeded to autologous transplant (n = 39), all but one engrafted. CONCLUSION: Plerixafor-based PBSC collection was safe and effective in our cohort and supports consideration as a primary mobilizing agent in children with malignancies.

Pediatric myelodysplastic syndrome with inflammatory manifestations: Diagnosis, genetics, treatment, and outcome.

BACKGROUND: Inflammatory manifestations (IM) are well described in adult patients with myelodysplastic syndrome (MDS), but the presentation is highly variable and no standardized treatment exists. This phenomenon is rarely reported in children. As more pediatric patients are hematopoietic stem cell transplantation (HSCT) candidates, the role of anti-inflammatory treatment in relation to HSCT should be defined. PROCEDURE: Here, we report a series of five children from a tertiary center. We describe the clinical presentation, molecular findings, and treatment options. RESULTS: All patients presented with advanced MDS with blast percentages ranging 10-30%, all had severe IM. One patient had MDS secondary to severe congenital neutropenia, the other four patients had presumably primary MDS. All four were found to harbor a PTPN11 gene driver mutation, which is found in 35% of cases of juvenile myelomonocytic leukemia (JMML). The mutation was present in the myeloid lineage but not in T lymphocytes. Three had symptoms of Behcet's-like disease with trisomy 8 in their bone marrow. All patients were treated with anti-inflammatory medications (mainly systemic steroids) in an attempt to bring them to allogeneic HSCT in a better clinical condition. All demonstrated clinical improvement as well as regression in their MDS status post anti-inflammatory treatment. All have recovered from both MDS and their inflammatory symptoms post HSCT. CONCLUSION: Primary pediatric MDS with IM is driven in some cases by PTPN11 mutations, and might be on the clinical spectrum of JMML. Anti-inflammatory treatment may reverse MDS progression and improve the outcome of subsequent HSCT.

Relapse of Aplastic Anemia with Majority Donor Chimerism (Donor-Type Aplasia) Occurring Late after Bone Marrow Transplantation.

There have been sporadic reports of the development of delayed disease recurrence after bone marrow transplantation for severe aplastic anemia despite sustained majority or full donor chimerism. This is termed "donor-type aplasia" (DTA). We describe the management and outcome of 11 pediatric patients from 8 institutions in Europe, the United States, and the Middle East who developed DTA at a mean of 35 months post-transplant. These patients were initially transplanted at a mean age of 10.0 years (range, 5.8 to 16.0 years), 9 from matched sibling donors and 2 from matched unrelated donors. Attempts to treat DTA with varying combinations of additional immunosuppression (including intravenous immunoglobulin, donor lymphocyte infusions, stem cell boosts, and other therapies) failed. Ten patients have received a conditioned second transplant, 9 from the same donor and 1 from a new matched unrelated donor. Aplasia has resolved in the remaining patient in response to ongoing eltrombopag therapy. All patients were alive at a mean of 92 months (range, 26 to 195) after a second transplant; 6 are in complete remission, but 4 suffered from second/recurrent DTA at 16 to 129 months after retransplant and required further transplant therapy.

Outcome of children relapsing after first allogeneic haematopoietic stem cell transplantation for acute myeloid leukaemia: a retrospective I-BFM analysis of 333 children.

Outcome of 333 children with acute myeloid leukaemia relapsing after a first allogeneic haematopoietic stem cell transplantation was analyzed. Four-year probability of overall survival (4y-pOS) was 14%. 4y-pOS for 122 children receiving a second haematopoietic stem cell transplantation was 31% and 3% for those that did not (P = <0·0001). Achievement of a subsequent remission impacted survival (P = <0·0001). For patients receiving a second transplant survival with or without achieving a subsequent remission was comparable. Graft source (bone marrow vs. peripheral blood stem cells, P = 0·046) and donor choice (matched family vs. matched unrelated donor, P = 0·029) positively impacted survival after relapse. Disease recurrence and non-relapse mortality at four years reached 45% and 22%.

Bone marrow failure unresponsive to bone marrow transplant is caused by mutations in thrombopoietin.

We report 5 individuals in 3 unrelated families with severe thrombocytopenia progressing to trilineage bone marrow failure (BMF). Four of the children received hematopoietic stem cell transplants and all showed poor graft function with persistent severe cytopenias even after repeated transplants with different donors. Exome and targeted sequencing identified mutations in the gene encoding thrombopoietin (THPO): THPO R99W, homozygous in affected children in 2 families, and THPO R157X, homozygous in the affected child in the third family. Both mutations result in a lack of THPO in the patients' serum. For the 2 surviving patients, improvement in trilineage hematopoiesis was achieved following treatment with a THPO receptor agonist. These studies demonstrate that biallelic loss-of-function mutations in THPO cause BMF, which is unresponsive to transplant due to a hematopoietic cell-extrinsic mechanism. These studies provide further support for the critical role of the MPL-THPO pathway in hematopoiesis and highlight the importance of accurate genetic diagnosis to inform treatment decisions for BMF.

Disruption of Thrombocyte and T Lymphocyte Development by a Mutation in ARPC1B.

Regulation of the actin cytoskeleton is crucial for normal development and function of the immune system, as evidenced by the severe immune abnormalities exhibited by patients bearing inactivating mutations in the Wiskott-Aldrich syndrome protein (WASP), a key regulator of actin dynamics. WASP exerts its effects on actin dynamics through a multisubunit complex termed Arp2/3. Despite the critical role played by Arp2/3 as an effector of WASP-mediated control over actin polymerization, mutations in protein components of the Arp2/3 complex had not previously been identified as a cause of immunodeficiency. Here, we describe two brothers with hematopoietic and immunologic symptoms reminiscent of Wiskott-Aldrich syndrome (WAS). However, these patients lacked mutations in any of the genes previously associated with WAS. Whole-exome sequencing revealed a homozygous 2 bp deletion, n.c.G623DEL-TC (p.V208VfsX20), in Arp2/3 complex component ARPC1B that causes a frame shift resulting in premature termination. Modeling of the disease in zebrafish revealed that ARPC1B plays a critical role in supporting T cell and thrombocyte development. Moreover, the defects in development caused by ARPC1B loss could be rescued by the intact human ARPC1B ortholog, but not by the p.V208VfsX20 variant identified in the patients. Moreover, we found that the expression of ARPC1B is restricted to hematopoietic cells, potentially explaining why a mutation in ARPC1B has now been observed as a cause of WAS, whereas mutations in other, more widely expressed, components of the Arp2/3 complex have not been observed.

Improved Outcome in Local Ewing Sarcoma With an Intensified Pilot Treatment Protocol SCMCIE 94.

This study evaluated the effect of an intensified pilot protocol, SCMCIE 94, on the outcome of Ewing sarcoma (EWS). The cohort included 121 patients with local or metastatic EWS treated at a tertiary pediatric medical center with the SCMCIE 94 (protocol 3, 1994 to 2011) or an earlier protocol (protocol 2, 1988 to 1994; protocol 1, 1985 to 1988). All protocols included 4 to 6 courses of chemotherapy, radiation, and surgery. Clinical data were collected retrospectively by chart review. Survival rates for protocol 3 were as follows: all patients-5-year event-free survival (EFS): 52.5%±5.6%, 10-year EFS: 49.3%±5.8%, 5-year overall survival (OS): 68.8%±5.3%, and 10-year OS: 51.1%±6.3%; patients with localized disease (any site)-5-year EFS: 63.5%±6.0% and 5-year OS: 77.2%±5.3%; patients with localized extremity disease-5-year EFS: 78.95%±8.3%, 10-year EFS: 68.6%±10.0%, 5-year OS: 90.7%±6.2%, and 10-year OS: 71.1%±11.2%. Protocol 3 was associated with an increase in 10-year EFS of 16% overall and 33% in patients with localized extremity disease compared with protocols 1+2, and a significant improvement in 5-year EFS and OS in patients with any localized disease (P=0.001). No survival benefit was found for metastatic disease. On multivariate analysis, protocol and metastatic disease were significantly independent prognostic factors. The intensified SCMCIE 94 protocol seems to increase survival in patients with localized but not metastatic EWS.

East Meets West-Impact of Ethnicity on Donor Match Rates in the Ezer Mizion Bone Marrow Donor Registry.

HLA haplotype frequencies in a volunteer bone marrow donor registry should reflect the frequencies of potential transplant recipients served by that registry, a challenge in a country with diverse subethnicities of immigrants from Eastern and Western cultures, such as Israel. We evaluated the likelihood of finding suitable donors for hypothetical patients drawn from defined subethnicities in the Ezer Mizion Bone Marrow Donor Registry (EM BMDR) from donors both within and outside the registry now and during the coming decade. On average, bioinformatics modeling predicts that, given current donor recruitment trends, 6/6 high-resolution HLA match rates for Israelis, which currently stand at 40% to 55% for most subethnicities, will rise by up to 1% per year over the next decade. Subethnicities with historically lower rates of interethnic admixture are less likely to find matches outside of their designated group but will benefit from expansion of the registry, whereas ethnically directed drives will enhance matching rates for currently underrepresented subethnicities. Donor searches for the same cohort using a large extramural registry was of only slight benefit for most of the 19 EM BMDR subethnicities evaluated, confirming that local donor registries that reflect the ethnic diversity of the community being served are best equipped to serve the needs of their respective communities. Contemporary trends of an increasingly multiethnic admixture in Israel may impact the effect of ethnic profiling in assessing future match rates for EM BMDR.

Calcineurin inhibitor-free strategies for prophylaxis and treatment of GVHD in children with posterior reversible encephalopathy syndrome after stem cell transplantation.

BACKGROUND: Posterior reversible encephalopathy syndrome (PRES) is a distinct clinico-radiologic entity that can occur following allogeneic hematopoietic stem cell transplantation, often in the context of treatment with calcineurin inhibitors (CNIs). PROCEDURE: We describe the results of CNI-free management of 14 children with PRES and review the clinical and radiologic manifestations of their presentation. RESULTS: Discontinuation of CNIs usually resulted in remission of PRES, but patients with established graft versus host disease (GVHD) at the time when treatment was changed often experienced progressive GVHD despite administration of immune suppressive and modulating treatments. All but three patients experienced full neurologic recovery. Nine children died as a result of either GVHD, disease relapse, or severe infection. CONCLUSIONS: Discontinuation of CNIs results in neurologic improvement in most cases, but superior alternative immune modulatory treatment is needed to prevent progression of established GVHD.

[EOSINOPHILIC FASCIITIS (EF)].

INTRODUCTION: Eosinophilic fasciitis (EF) is a rare connective tissue disease characterized by erythema, edema and myalgia with induration and thickening of the skin and soft tissue, especially subcutaneous fascia. Laboratory findings usually show peripheral eosinophilia, and full-thickness wedge biopsy is essential to establish the diagnosis. Corticosteroids are effective and remain the standard therapy for EF, although some patients may improve spontaneously. In this article we report a case of a 17 years old male who has been diagnosed with EF 2 years after bone marrow transplantation and review the clinical manifestations, pathology, diagnosis, differential diagnosis, and treatment of EF.

Outcomes after Unrelated Umbilical Cord Blood Transplantation for Children with Osteopetrosis.

Hematopoietic stem cell transplantation (HSCT) is the only curative treatment for most children with osteopetrosis (OP). Timing of HSCT is critical; therefore, umbilical cord blood transplantation (UCBT) is an attractive option. We analyzed outcomes after UCBT in 51 OP children. Median age at UCBT was 6 months. Seventy-seven percent of the cord blood grafts had 0 or 1 HLA disparity with the recipient. Conditioning regimen was myeloablative (mostly busulfan-based in 84% and treosulfan-based in 10%). Antithymocyte globulin was given to 90% of patients. Median number of total nucleated and CD34+ cells infused was 14 × 107/kg and 3.4 × 105/kg, respectively. Median follow-up for survivors was 74 months. Cumulative incidence (CI) of neutrophil recovery was 67% with a median time to recovery of 23 days; 33% of patients had graft failure, 81% of engrafted patients had full donor engraftment, and 19% had mixed donor chimerism. Day 100 CI of acute graft-versus-host disease (grades II to IV) was 31% and 6-year CI of chronic graft-versus-host disease was 21%. Mechanical ventilation was required in 28%, and veno-occlusive disease was diagnosed in 16% of cases. Six-year overall survival rate was 46%. Comparative studies with other alternative donors should be performed to evaluate whether UCBT remains a valid alternative for children with OP without an HLA-matched donor.

Fertility After Treatment With High Dose Melphalan in Women With Acute Myelogenous Leukemia.

BACKGROUND: High-dose melphalan (HDM) is an integral component of conditioning regimens for autologous and allogeneic hematopoietic stem cell transplantation for patients with malignant and non-malignant diseases. The gonadotoxic effects of HDM are often obscured by previous or concurrent administration of alkylating agents. From April 1996 to January 2006 our acute myeloid leukemia treatment regimen included induction and consolidation therapy with cytosine arabinoside, anthracyclines and etoposide, followed by HDM and autologous stem cell infusion. We explored gonadal function in surviving female patients so treated, who represent a unique group of patients exposed to HDM as a single gonadotoxic agent. PROCEDURE: The fertility assessment included a questionnaire, blood tests for luteinizing hormone, follicle stimulating hormone and anti mullerian hormone (AMH), and a gynecological ultrasound exam for antral follicular count (AFC). RESULTS: Eight female survivors participated. Although fertility assessment showed considerable damage to ovarian reserve in all participants, four of the eight female survivors conceived and bore children without medical intervention. CONCLUSION: In this cohort, HDM treatment reduced fertility potential but did not preclude fecundity. Early referral to a fertility clinic and long term follow-up including serial measurements of AMH levels and AFC for female patients receiving HDM are recommended.

Outcome of patients with hemoglobinopathies given either cord blood or bone marrow transplantation from an HLA-identical sibling.

We analyzed the outcomes of 485 patients with thalassemia major (TM) or sickle cell disease (SCD) receiving HLA-identical sibling cord blood transplantation (CBT, n = 96) or bone marrow transplantation (BMT, n = 389). Compared with patients given BMT, CBT recipients were significantly younger (median age 6 vs 8 years, P = .02), and were treated more recently (median year 2001 vs 1999, P < .01). A higher proportion of patients with TM belonging to classes II-III of the Pesaro classification received BMT (44%) compared with CBT (39%, P < .01). In comparison with patients receiving BMT (n = 259, TM; n = 130, SCD), those given CBT (n = 66, TM; n = 30, SCD) had slower neutrophil recovery, less acute graft-versus-host disease (GVHD) and none had extensive chronic GVHD. With a median follow-up of 70 months, the 6-year overall survival was 95% and 97% after BMT and CBT, respectively (P = .92). The 6-year disease-free survival (DFS) was 86% and 80% in TM patients after BMT and CBT, respectively, whereas DFS in SCD patients was 92% and 90%, respectively. The cell dose infused did not influence outcome of patients given CBT. In multivariate analysis, DFS did not differ between CBT and BMT recipients. Patients with TM or SCD have excellent outcomes after both HLA-identical sibling CBT and BMT.

Analysis of risk factors influencing outcomes after cord blood transplantation in children with juvenile myelomonocytic leukemia: a EUROCORD, EBMT, EWOG-MDS, CIBMTR study.

We retrospectively analyzed 110 patients with juvenile myelomonocytic leukemia, given single-unit, unrelated donor umbilical cord blood transplantation. Median age at diagnosis and at transplantation was 1.4 years (age range, 0.1-6.4 years) and 2.2 years (age range, 0.5-7.4 years), respectively. Before transplantation, 88 patients received chemotherapy; splenectomy was performed in 24 patients. Monosomy of chromosome 7 was the most frequent cytogenetic abnormality, found in 24% of patients. All but 8 patients received myeloablative conditioning; cyclosporine plus steroids was the most common graft-versus-host disease prophylaxis. Sixteen percent of units were HLA-matched with the recipient, whereas 43% and 35% had either 1 or 2 to 3 HLA disparities, respectively. The median number of nucleated cells infused was 7.1 × 10(7)/kg (range, 1.7-27.6 × 10(7)/kg). With a median follow-up of 64 months (range, 14-174 months), the 5-year cumulative incidences of transplantation-related mortality and relapse were 22% and 33%, respectively. The 5-year disease-free survival rate was 44%. In multivariate analysis, factors predicting better disease-free survival were age younger than 1.4 years at diagnosis (hazard ratio [HR], 0.42; P = .005), 0 to 1 HLA disparities in the donor/recipient pair (HR, 0.4; P = .009), and karyotype other than monosomy 7 (HR, 0.5; P = .02). Umbilical cord blood transplantation may cure a relevant proportion of children with juvenile myelomonocytic leukemia. Because disease recurrence remains the major cause of treatment failure, strategies to reduce incidence of relapse are warranted.

Bone marrow transplantation for non-malignant diseases using treosulfan-based conditioning.

BACKGROUND: Treosulfan (treo) is an alkylating agent with a low acute toxicity profile that is increasingly used in hematopoietic stem cell transplantation, predominantly in non-malignant diseases. Treosulfan is usually combined with additional agents, but there is scant evidence to allow comparison between different conditioning protocols using treosulfan. We present the experience of three pediatric transplantation centers in Israel using different treosulfan-based conditioning regimens. PROCEDURE: Data were collected retrospectively on 44 children who underwent 45 hematopoietic stem cell transplantations using treosulfan in combination with either fludarabine (flu) and thiotepa (tt) (n = 20), cyclophosphamide (cy) (n = 6) or fludarabine alone (n = 19). RESULTS: Overall survival (OS) was 70.5%. Disease free survival (DFS) was 54.6%. There was no statistically significant difference between treatment groups in either OS or DFS. Overall survival in patients younger than one year was higher (88.2%). There were significantly more patients with 100% donor chimerism transplanted with flu/treo/tt compared with flu/treo or treo/cy (94.7% compared to 66.7% and 16.7%, respectively). Further prospective studies are required to determine the optimal treosulfan-based preparative regimen for children with non-malignant diseases. Pediatr Blood Cancer 2015;62:299-304. © 2014 Wiley Periodicals, Inc.

Genetic analysis and clinical picture of severe congenital neutropenia in Israel.

BACKGROUND: The relative frequency of mutated genes among patients with severe congenital neutropenia (SCN) may differ between various ethnic groups. To date, few population-based genetic studies have been reported. This study describes the genetic analysis of 32 Israeli patients with SCN. PROCEDURES: Clinical data were retrieved from the prospective Israeli Inherited Bone Marrow Failure Registry. Recruitment included living and deceased patients who were diagnosed between 1982 and 2012, for whom molecular diagnosis was performed. ELANE, HAX1 and G6PC3 genes were sequenced in all patients, and GFI-1 and WAS genes were sequenced if other genes were wildtype. RESULTS: Eleven patients (34%) had heterozygous mutations in ELANE (10 kindreds), eight (25%) had homozygous mutations in G6PC3 (5 kindreds) and 13 (41%) had no detected mutations. No patients had mutations in HAX1 or WAS. Four of the eight patients with G6PC3 mutations had congenital anomalies. The probability of survival for all patients was 50% at age of 18. Deaths were mainly due to sepsis (5 patients, 4/5 not responding to G-CSF, none with G6PC3 mutation). Two patients developed acute myelogenous leukemia (AML) and one myelodysplastic syndrome (MDS), none with G6PC3 mutation. CONCLUSIONS: We found a unique pattern of SCN mutations in Israel with homozygous G6PC3 mutations in eight (25%) patients, the highest frequency described so far. HAX1 mutations, reported mainly in Sweden and Iran, were absent. Patients with G6PC3 mutations had congenital anomalies, appeared to have a better response to G-CSF, and so far have not developed AML or MDS.

TNF-α has tropic rather than apoptotic activity in human hematopoietic progenitors: involvement of TNF receptor-1 and caspase-8.

Tumor necrosis factor-α (TNF-α) has been suggested to exert detrimental effects on hematopoietic progenitor function that might limit the success of transplants. In this study, we assessed the influences of TNF-α and its two cognate receptors on the function of fresh umbilical cord blood (UCB) and cryopreserved mobilized peripheral blood (mPB). CD34(+) progenitors from both sources are less susceptible to spontaneous apoptosis than lineage-committed cells and are not induced into apoptosis by TNF-α. Consequently, the activity of UCB-derived severe combined immune deficiency (SCID) reconstituting cells and long-term culture-initiating cells is unaffected by this cytokine. On the contrary, transient exposure of cells from both sources to TNF-α stimulates the activity of myeloid progenitors, which persists in vivo in UCB cell transplants. Progenitor stimulation is selectively mediated by TNF-R1 and involves activation of caspase-8, without redundant activity of TNF-R2. Despite significant differences between fresh UCB cells and cryopreserved mPB cells in susceptibility to apoptosis and time to activation, TNF-α is primarily involved in tropic signaling in hematopoietic progenitors from both sources. Cytokine-mediated tropism cautions against TNF-α neutralization under conditions of stress hematopoiesis and may be particularly beneficial in overcoming the limitations of UCB cell transplants.