Topological quantum computing with only one mobile quasiparticle

In a topological quantum computer, universal quantum computation is performed by dragging quasiparticle excitations of certain two dimensional systems around each other to form braids of their world lines in 2 + 1 dimensional space-time. In this Letter we show that any such quantum computation that can be done by braiding n identical quasiparticles can also be done by moving a single quasiparticle around n - 1 other identical quasiparticles whose positions remain fixed.

Adenovirus-mediated p53 gene therapy in osteosarcoma cell lines: sensitization to cisplatin and doxorubicin

The poor prognosis for patients with metastatic osteosarcoma (OS) indicates that new therapeutic options should be explored. Studies with adenoviral-mediated p53 gene transfer have been conducted in many cancer types including cervical, ovarian, prostatic and head and neck tumors. However, limited work has been carried out with pediatric cancers, including OS. Using three viral constructs containing cDNA for wild-type p53, mutant p53 (Cys135Ser) and lacZ, we studied the effect of adenoviral-mediated gene therapy in four OS cell lines: Saos-2 (p53-/-), HOS (R156P), KHOS/NP (R156P) and MNNG (R156P, F270L). We demonstrated that the virus efficiently enters the cells using the beta-galactosidase assay. Using the MTT assay, we have shown a dose-dependent decrease in cell viability 72 h post-treatment that occurs with Ad-wtp53 but not with Ad-mutp53. We have also shown that treatment with Ad-wtp53 significantly increases sensitivity of the cell lines to cisplatin and doxorubicin, chemotherapeutic agents commonly used in the treatment of OS. Our results indicate that restoration of wt p53 function in OS cells provides a basis for novel approaches to treatment of this disease.

In vitro cytoprotective activity of squalene on a bone marrow versus neuroblastoma model of cisplatin-induced toxicity. implications in cancer chemotherapy

The development of a non-toxic selective cytoprotective agent that preferentially protects normal tissues from chemotherapy toxicity, without protecting malignant tissues, is a major challenge in cancer chemotherapy research. The available cytoprotective agents are either toxic or lack selective cytoprotective activity. Here, we report the in vitro selective cytoprotective activity of squalene, an isoprenoid molecule with antioxidant properties. Normal human bone marrow (BM) derived colony-forming unit (CFU) growth was increased by squalene in a dose-dependent manner. Squalene (12.5-25 microM) treatment significantly protected the CFUs from cisplatin-induced toxicity; the protective effect was equivalent to reduced glutathione (GSH), a known cytoprotective agent. Squalene also increased the long-term survival of cisplatin-treated 4-week-old CFUs. Cisplatin-induced apoptosis of CFUs as measured by the TUNEL assay was reduced by squalene. To examine the squalene-induced protection of tumours, several neuroblastoma cell lines, including five MYCN-amplified cell lines, were grown in monolayers, as well as in anchorage-independent cultures, in the presence of squalene and cisplatin. Squalene did not protect the neuroblastoma (NBL) cell lines from cisplatin-induced toxicity. In addition, squalene did not protect the NBL cells from carboplatin, cyclophosphamide, etoposide and doxorubicin-induced toxicity. In conclusion, our results suggest that squalene has a selective in vitro cytoprotective effect on BM-derived haematopoietic stem cells that is equipotent to GSH.

Allogeneic bone marrow transplantation vs chemotherapy for children with Philadelphia chromosome-positive acute lymphoblastic leukemia

Allogeneic bone marrow transplant (BMT) with an MRD in complete remission (CR)1 is the preferred treatment for children with Philadelphia-positive (Ph(+)) ALL. The role of MUD BMT in CR1 is still controversial. We compared the outcomes of two treatment strategies: BMT using an MRD or MUD vs chemotherapy in children with Ph(+) ALL in CR1. In total, 21 children were treated from 1985 to 2001. In all, 10 received chemotherapy and 11 received allogeneic BMT: four MRD, seven MUD. In the MRD group, one relapsed 12 months after BMT and died; the remaining three are long-term event-free survivors (median follow-up, 6.1 years). In the MUD group four died; the remaining three are long-term event-free survivors (median follow-up, 7.2 years). The 4-year event-free survival (EFS) for the BMT group was 53+/-15%. In the chemotherapy group, seven relapsed after a median period of 12.5 months and three remain in continuous CR (median follow-up, 2.4 years). Four chemotherapy patients received CR2 transplants; all died. The 4-year EFS for the chemotherapy and MUD groups was 33+/-17 and 35.7+/-20%, respectively. This difference was not statistically significant. We continue to support treating children with Ph(+) ALL with MRD BMT in CR1. The effectiveness of MUD BMT vs chemotherapy merits further study.

Low-intensity hematopoietic stem-cell transplantation across human leucocyte antigen barriers in dyskeratosis congenita

Since the results of conventional hematopoietic stem-cell transplantation (HSCT) for patients with dyskeratosis congenita (DC) are poor owing to the high incidence of transplant-related complications, we explored the use of a low-intensity HSCT regimen. We report two children with DC with severe cytopenia, who underwent successful HSCT from a matched unrelated donor after conditioning with fludarabine, cyclophosphamide, and antithymocyte globulin. Graft-versus-host-disease (GVHD) prophylaxis consisted of corticosteroids and cyclosporin A. The regimen was well tolerated, no significant transplant-related complications were observed, and engraftment was rapid and complete. At 15 and 16 months after HSCT, the children were fully engrafted, in excellent clinical condition, full-donor chimerism, and no signs of GVHD. We conclude that a low-intensity regimen is sufficient to induce durable engraftment using matched unrelated donor HSCT in DC patients, with minimal 1-year transplant-related toxicity. Longer follow-up will determine whether this regimen also reduces long-term toxicity.

Single-centre experience with allogeneic bone marrow transplantation for acute lymphoblastic leukaemia in childhood: similar survival after matched-related and matched-unrelated donor transplants

Seventy percent of children with acute lymphoblastic leukaemia (ALL) who may benefit from bone marrow transplant (BMT) lack a human leucocyte antigen (HLA)-matched related donor (MRD). For these children, BMT from a matched unrelated donor (MUD) represents a therapeutic option. We reviewed the course of 62 children with ALL who received fully matched marrow allografts at our institution between 1990 and 1998: 36 with MRDs and 26 with MUDs. Clinical characteristics were similar in the two groups. The interval from attainment of pre-BMT complete remission to transplant was significantly longer in the MUD group. Conditioning (etoposide/total body irradiation) and graft-versus-host disease (GVHD) prophylaxis regimens were the same for all patients, and all received T cell-replete bone marrow. There was no significant difference in probability of engraftment, or time to engraftment, in the two groups. MUD BMT recipients had a significantly greater incidence of grade II-IV acute GVHD (58% versus 24% in the MRD group; P = 0.02), and demonstrated a trend towards more chronic GVHD (39% versus 15%; P = 0.06). Three years post BMT, the probabilities of transplant-related mortality were 33 +/- 11% and 20 +/- 8% in MUD and MRD groups respectively (P = 0.38); the probabilities of relapse were 28 +/- 12% and 41 +/- 9% respectively (P = 0.19). Lansky or Karnofsky performance scores in event-free survivors were 90-100 in 87% of the MUD group and 83% of the MRD group. With a median follow up of 38 months (range, 3-97), 3-year event-free survival was 49 +/- 11% and 47 +/- 9% in the MUD and MRD BMT groups respectively (P = 0.71). These results suggest that MUD BMT is a valuable therapy for children with ALL in whom BMT is indicated, and underscore the importance of efforts aimed at expediting unrelated donor searches for patients lacking a MRD.

Immune function in patients with Shwachman-Diamond syndrome

Shwachman-Diamond syndrome (SDS) is an inherited multisystem disorder characterized by exocrine pancreatic dysfunction and varying degrees of cytopenia. In addition, various immunological abnormalities have been noted. To clarify the issue of immunological competence or incompetence in SDS, we prospectively studied immune function in 11 patients with SDS. Seven suffered from recurrent bacterial infections and six from recurrent viral infections. Varying degrees of impairment were readily identified. All patients had neutropenia; total lymphocyte counts, however, were normal in all except one patient. Nine patients had B-cell defects comprising one or more of the following abnormalities: low IgG or IgG subclasses, low percentage of circulating B lymphocytes, decreased in vitro B-lymphocyte proliferation and a lack of specific antibody production. Seven out of nine patients studied had at least one T-cell abnormality comprising a low percentage of total circulating T lymphocytes or CD3+/CD4+ cell subpopulations or decreased in vitro T-lymphocyte proliferation. Five out of six patients studied had decreased percentages of circulating natural killer cells. Moreover, neutrophil chemotaxis was significantly low in all the patients studied. These data point to a major immunodeficiency component in SDS that places patients at heightened risk of infections, even if neutrophil numbers are protective. This finding broadens the definition of the syndrome substantially: it suggests that the SDS marrow defect occurs at the level of an early haematological-lymphocytic stem cell or that a combined marrow and thymic stromal defect accounts for the aberrant function of haematopoietic and lymphopoietic lineages.

Shwachman-Diamond syndrome marrow cells show abnormally increased apoptosis mediated through the Fas pathway

Shwachman-Diamond syndrome (SDS) is an inherited bone marrow disorder with varying cytopenias and a strong predilection to myelodysplastic syndrome (MDS) and acute myeloid leukemia. Previously, it was found that the percentage of CD34(+) cells in bone marrow and the in vitro colony formation from CD34(+) cells of patients with SDS were markedly reduced. For these reasons, and because apoptosis is central in the pathogenesis of bone marrow dysfunction in MDS, this study was initiated to delineate the role of apoptosis in the pathogenesis of the marrow failure. Eleven children with SDS were studied. Compared to normal controls, patients' marrow mononuclear cells plated in clonogenic cultures showed a significantly higher tendency to undergo apoptosis. The defect in SDS was found in patients with and without MDS. Patients showed a more prominent decrease in colony formation and increased apoptosis after preincubation with activating anti-Fas antibody. Fas expression on marrow cells from patients was significantly higher than from normal controls. The difference between patients and controls for Fas expression was also significant for the following cell fraction subpopulations: CD34(-)/CD38(-), CD34(-)/CD38(+), and CD34(+). In conclusion, SDS hematopoietic progenitors are intrinsically flawed and have faulty proliferative properties and increased apoptosis. Bone marrow failure in SDS appears mediated by increased apoptosis as the central pathogenetic mechanism. This increased propensity for apoptosis is linked to increased expression of the Fas antigen and to hyperactivation of the Fas signaling pathway.

Differences in cell cycle kinetics of candidate engrafting cells in human bone marrow and mobilized peripheral blood

Patients undergoing hematopoietic stem cell transplantation (HSCT) with mobilized peripheral blood (MPB) engraft quicker than those receiving bone marrow (BM). Our objective was to determine whether candidate engrafting cells--primitive hematopoietic progenitors (PHPs)--from MPB and BM exhibit different responses to cytokines that could explain this observation. We compared the cell cycle kinetics and ex vivo expansion of PHP-enriched cells obtained from MPB (n = 12) and BM (n = 10) by fluorescence-activated sorting of CD90+, AC133+ or CD38(dull) subsets of pre-selected CD34(+) cells. Cell cycle status, before and after 40 hours of serum-free culture with a cytokine cocktail, was assessed by multiparameter flow cytometry following incubation with Hoechst 33342 and pyronin Y. We found that 0.2% +/- 0.3% of MPB CD34(+)CD90(+) cells were in S/G(2)/M phases at hour 0, compared with 5% +/- 2.5% of those from BM (p = 0.0001), and 86.3% +/- 9.7% were in G(0), compared with 65.3% +/- 10% of those in BM (p = 0.0001). After 40 hours of culture, CD34(+)CD90(+) cells from MPB were more mitotically active than those from BM, with 29% +/- 4.9% in S/G(2)/M and 20% +/- 11.4% in G(0), compared to 19% +/- 6.5% (p = 0.001) and 39.2% +/- 22% (p = 0.027) of cells from BM. There was greater expansion of both total CD34(+) cells and the CD90(+) subset from MPB samples (p = 0.001 and 0.0001, respectively). Results from PHPs defined on the basis of AC133 expression correlated well with results obtained in CD90(+) subsets (r(2) = 0.81; p = 0.014).MPB PHPs appear to be primed for a greater acceleration in mitotic activity upon cytokine exposure. This qualitative difference may contribute to the earlier engraftment seen after HSCT using MPB grafts.

Replicative stress after allogeneic bone marrow transplantation: changes in cycling of CD34+CD90+ and CD34+CD90- hematopoietic progenitors

To further characterize hematopoietic "replicative stress" induced by bone marrow transplantation (BMT), the cell-cycle status of CD90+/- subsets of marrow CD34+ cells obtained 2 to 6 months after transplantation from 11 fully chimeric recipients was examined. Cycling profiles, derived by flow cytometry after staining with Hoechst 33342 and pyronin Y, were compared with those of 14 healthy marrow donors. Primitive CD34+CD90+ cells represented a smaller proportion of CD34+ cells in recipients (10% +/- 4% versus 19.6% +/- 5.3% in donors; P <.0001) and were more mitotically active, with the proportion of cells in S/G2/M nearly 4-fold higher than in donors (15.6% +/- 3% and 4.4% +/- 1.6%, respectively; P <.0001). By comparison, there was a modest increase in the proportion of CD34+CD90- progenitors in S/G2/M after BMT (10.9% +/- 1% vs 9.6% +/- 2% in donors; P =.04). Replicative stress after BMT is borne predominantly by cells in a diminished CD34+CD90+ population.

Differential sensitivity of various pediatric cancers and squamous cell carcinomas to lovastatin-induced apoptosis: therapeutic implications

3-Hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase is the rate-limiting enzyme of the mevalonate pathway, the diverse array of end products of which are vital for a variety of cellular functions, including cholesterol synthesis and cell cycle progression. We showed previously that this enzyme holds a critical role in regulating tumor cell fate, including cell death, as its expression is down-regulated in response to retinoic acid, a potent anticancer therapeutic. Indeed, direct inhibition of HMG-CoA reductase with lovastatin, a competitive inhibitor of this enzyme, induced a pronounced apoptotic response in neuroblastoma and acute myeloid leukemic cells. We have now extended this work and evaluated a wide variety and large number of tumor-derived cell lines for their sensitivity to lovastatin-induced apoptosis. These cell lines were exposed to a wide range (0-100 microM) of lovastatin for 2 days and assayed for cell viability using the 3,4,5-dimethyl thiazlyl-2,2,5-diphenyltetrazolium bromide assay and the induction of apoptosis by flow cytometric and ultrastructural analyses. Lovastatin induced a pronounced apoptotic response in cells derived from juvenile monomyelocytic leukemia, pediatric solid malignancies (rhabdomyosarcoma and medulloblastoma), and squamous cell carcinoma of the cervix and of the head and neck. Interestingly, the subset of malignancies that are particularly sensitive to lovastatin-induced apoptosis correspond to those tumor subtypes that are sensitive to the biological and antiproliferative effects of retinoids in vitro. The nature of the biologically active form of lovastatin has been challenged recently as the growth-inhibitory effects of this drug were attributed to its prodrug lactone form that does not inhibit HMG-CoA reductase function. In this report, we demonstrate that the apoptotic properties of lovastatin are triggered by the open ring acid form that is a potent inhibitor of HMG-CoA reductase activity. Thus, we have identified a subset of tumors that are sensitive to lovastatin-induced apoptosis and show HMG-CoA reductase as a potential therapeutic target of these cancers.

Improved survival in severe acquired aplastic anemia of childhood

Multi-agent immunosuppressive therapy has produced improved survival for severe acquired aplastic anemia in children. Recently, some investigators have suggested that immunosuppressive therapy may replace bone marrow transplantation as first-line therapy for this disorder. To assess its validity, we compared the outcomes of bone marrow transplantation vs immunosuppressive therapy in one institution from 1987 to 1997. We studied 46 consecutive patients less than 18 years of age who presented between January 1987 and April 1997. Inherited marrow failure syndromes and myelodysplastic syndromes were excluded. Patients received immunosuppressive therapy vs bone marrow transplantation based on availability of HLA-matched donors. The main outcome measures were survival, complete marrow and hematological remission, or partial remission but achieving independence from transfusional support. Twenty patients received multi-agent immunosuppressive therapy (cyclosporine, antithymocyte globulin and methylprednisolone); 11 attained complete remission and three partial remission for a transfusion-independent survival of 70%. Six patients died of infectious and hemorrhagic complications. Twenty-six patients were transplanted and 24 (93%) achieved complete remission; one achieved a PR, 25 remain transfusion independent with a median follow-up of 5.9 years or 70 months. One patient developed AML 34 months after successful transplant and one patient died due to graft failure and complications of transplant. There has been a striking improvement in survival for pediatric patients treated with multi-agent immunosuppression in the last decade. However, transplantation results have also improved and this remains the definitive first-line therapy for severe acquired aplastic anemia in this age group.

Combined corticosteroid/granulocyte colony-stimulating factor (G-CSF) therapy in the treatment of severe congenital neutropenia unresponsive to G-CSF: Activated glucocorticoid receptors synergize with G-CSF signals

More than 90% of patients with severe congenital neutropenia (SCN) respond to granulocyte colony-stimulating factor (G-CSF) therapy. The basis for the refractory state in the remaining patients is unknown. To address this issue, we studied a child with SCN who was totally unresponsive to G-CSF and had a novel point mutation in the extracellular domain of the G-CSF receptor (GCSF-R). Marrow stromal support of granulopoiesis was evaluated by plating CD34(+) cells on preformed stromal layers. Nonadherent cells were harvested and assayed in clonogenic assays for granulocytic colony production. The in vitro effect of G-CSF and corticosteroids on granulopoiesis was evaluated in clonogenic assays of marrow mononuclear cells, by proliferation studies of the murine myeloid cell line 32D expressing the patient's mutated G-CSFR, and by measuring STAT5 activation in nuclear extracts from stimulated cells.Patient's stroma supported granulopoiesis derived from control marrow CD34(+) cells in a normal manner. Normal stroma, however, failed to induce granulopoiesis from patient's CD34(+) cells. Clonogenic assays of the patient's marrow mononuclear cells incorporating either G-CSF or hydrocortisone produced little neutrophil growth. In contrast, inclusion of both G-CSF and hydrocortisone in the cytokine "cocktail" markedly increased the neutrophil numbers. Proliferation of 32D cells expressing the mutated receptor and STAT5 activation were improved by a combination of G-CSF and dexamethasone. When small daily doses of oral prednisone were then administered to the patient with conventional doses of subcutaneous G-CSF, the patient responded with increased neutrophil numbers and with a complete reversal of the infectious problems. These data provide insight into SCN unresponsive to standard G-CSF treatment and to the potential corrective action of combined treatment with G-CSF and corticosteroids through synergistic activation of STAT5.

Diamond-Blackfan anaemia

Diamond-Blackfan anaemia (DBA) has had an intellectual allure for decades for clinical and experimental haematologists. The syndrome has a haematological phenotype of early-onset red-cell aplasia but is coupled with a baffling array of pleiotropy. There is discordance with modes of inheritance, physical anomalies, erythropoietic response to corticosteroid therapy, spontaneous 'remissions', and evolution to malignant myeloid transformation and to cancer. The recent discovery of two genes associated with DBA is the entry point for explaining the diversity of the phenotype and for understanding the molecular basis of the syndrome.

Myelodysplasia syndrome and acute myeloid leukemia in patients with congenital neutropenia receiving G-CSF therapy

Granulocyte colony-stimulating factor (G-CSF) has had a major impact on management of "severe chronic neutropenia," a collective term referring to congenital, idiopathic, or cyclic neutropenia. Almost all patients respond to G-CSF with increased neutrophils, reduced infections, and improved survival. Some responders with congenital neutropenia have developed myelodysplastic syndrome and acute myeloblastic leukemia (MDS/AML), which raises the question of the role of G-CSF in pathogenesis. The Severe Chronic Neutropenia International Registry (SCNIR), Seattle, WA, has data on 696 neutropenic patients, including 352 patients with congenital neutropenia, treated with G-CSF from 1987 to present. Treatment and patient demographic data were analyzed. The 352 congenital patients were observed for a mean of 6 years (range, 0.1-11 years) while being treated. Of these patients, 31 developed MDS/AML, for a crude rate of malignant transformation of nearly 9%. None of the 344 patients with idiopathic or cyclic neutropenia developed MDS/AML. Transformation was associated with acquired marrow cytogenetic clonal changes: 18 patients developed a partial or complete loss of chromosome 7, and 9 patients manifested abnormalities of chromosome 21 (usually trisomy 21). For each yearly treatment interval, the annual rate of MDS/AML development was less than 2%. No significant relationships between age at onset of MDS/AML and patient gender, G-CSF dose, or treatment duration were found (P >.15). In addition to the 31 patients who developed MDS/AML, the SCNIR also has data on 9 additional neutropenic patients whose bone marrow studies show cytogenetic clonal changes but the patients are without transformation to MDS/AML. Although our data does not support a cause-and-effect relationship between development of MDS/AML and G-CSF therapy or other patient demographics, we cannot exclude a direct contribution of G-CSF in the pathogenesis of MDS/AML. This issue is unclear because MDS/AML was not seen in cyclic or idiopathic neutropenia. Improved survival of congenital neutropenia patients receiving G-CSF therapy may allow time for the expression of the leukemic predisposition that characterizes the natural history of these disorders. However, other factors related to G-CSF may also be operative in the setting of congenital neutropenia. (Blood. 2000;96:429-436)

Thrombocytopenia with absent radii: frequency of marrow megakaryocyte progenitors, proliferative characteristics, and megakaryocyte growth and development factor responsiveness

Congenital thrombocytopenia with absent radii (TAR syndrome) is characterized by defective thrombopoiesis and bleeding in early infancy. To determine the frequency and responsiveness to cytokines of megakaryocyte progenitors (CFU-Meg) in TAR syndrome, the authors studied marrow samples from 3 patients and 6 normal controls, using optimally standardized megakaryocyte growth media incorporating interleukin-3, interleukin-6, stem cell factor, and granulocyte-monocyte colony-stimulating factor, with and without pegylated recombinant human megakaryocyte growth and development factor (PEG-rHuMGDF). CFU-Meg was identified with a specific staining system utilizing monoclonal antibodies to glycoprotein IIb/IIIa. Growth of small CFU-Meg colonies (3-20 cells/colony) was observed in all patients in cultures without PEG-rHuMGDF, with a mean frequency of 8 (range 5-12) per 2.25 x 10(5) mononuclear cells plated (control mean 23; range 2-70). Identical cultures of marrow cells from patients and controls with added PEG-rHuMGDF produced more colonies per dish (mean 17, range 8-23; control mean 30, range 6-62). Except for 1 case, however, patients' colonies in response to PEG-rHuMGDF remained smaller than those of controls. Two patients tested had higher plasma thrombopoietin levels than 6 normal subjects. The findings demonstrate proliferative and PEG-rHuMGDF-responsive megakaryocytic progenitors in TAR syndrome. The modest reduction in frequency of megakaryocyte progenitors and the suboptimal size of colonies in response to PEG-rHuMGDF are compatible with the reported defective signal transduction in the c-mpl pathway in TAR syndrome.

Mastocytosis cells bearing a c-kit activating point mutation are characterized by hypersensitivity to stem cell factor and increased apoptosis

Mastocytosis is characterized by abnormal infiltration of mast cells into various organs. An activating mutation in c-kit, involving an A --> T substitution at nucleotide 2648 has recently been described in some patients with mastocytosis. We describe a 12-year-old girl with this mutation in her bone marrow cells at diagnosis with a myelodysplastic syndrome (MDS) without evidence of mastocytosis, and then in peripheral blood mononuclear cells 1 year later after the emergence of mastocytosis. The role of the c-Kit receptor and its ligand stem cell factor (SCF) in the pathogenesis of the disease was analysed in marrow cell clonogenic assays. We show that the genetic abnormalities in the patient resulted in factor-independent growth and hypersensitivity of primitive progenitors to SCF, with increased production of mast cells. Increased apoptosis and cluster formation, consistent with the myelodysplastic nature of the disorder, accompanied accumulation of abnormal cells with increasing concentrations of SCF.

Shwachman-Diamond syndrome: An inherited preleukemic bone marrow failure disorder with aberrant hematopoietic progenitors and faulty marrow microenvironment

Shwachman-Diamond syndrome (SD), an inherited disorder with varying cytopenias and a marked tendency for malignant myeloid transformation, is an important model for understanding genetic determinants in hematopoiesis. To define the basis for the faulty hematopoietic function, 13 patients with SD (2 of whom had myelodysplasia with a clonal cytogenetic abnormality) and 11 healthy marrow donors were studied. Patients with SD had significantly lower numbers of CD34(+) cells on bone marrow aspirates. SD CD34(+) cells plated directly in standard clonogenic assays showed markedly impaired colony production potential, underscoring an intrinsically aberrant progenitor population. To assess marrow stromal function, long-term marrow stromal cell cultures (LTCs) were established. Normal marrow CD34(+) cells were plated over either SD stroma (N/SD) or normal stroma (N/N); SD CD34(+) cells were plated over either SD stroma (SD/SD) or normal stroma (SD/N). Nonadherent cells harvested weekly from N/SD LTCs were strikingly reduced compared with N/N LTCs; numbers of granulocyte-monocyte colony-forming units (CFU-GM) derived from N/SD nonadherent cells were also lower. SD/N showed improved production of nonadherent cells and CFU-GM colonies compared with SD/SD, but much less than N/N. Stem-cell and stromal properties from the 2 patients with SD and myelodysplasia did not differ discernibly from SD patients without myelodysplasia. We conclude that in addition to a stem-cell defect, patients with SD have also a serious, generalized marrow dysfunction with an abnormal bone marrow stroma in terms of its ability to support and maintain hematopoiesis. This dual defect exists in SD with and without myelodysplasia.

Alternative donor bone marrow transplantation for children with juvenile myelomonocytic leukemia

The purpose of this study was to evaluate the outcome of children with juvenile myelomonocytic leukemia (JMML) treated with alternative donor bone marrow transplantation (BMT). Twelve consecutive patients with JMML confirmed by in vitro clonogenic assays underwent alternative donor BMT. Ten patients received pretransplant chemotherapy for one to seven cycles (cytosine arabinoside regimens). Eight underwent splenectomy before the transplant. Donors were unrelated for nine patients and partially matched related for three. Conditioning included total body irradiation for all but one patient. Graft-versus-host disease (GVHD) prophylaxis included in vitro partial T-lymphocyte depletion for five patients with cyclosporine arabinoside, and cyclosporine arabinoside and methotrexate for seven. Acute GVHD developed in all patients, and chronic GVHD developed in 7 of 11 evaluable patients. Relapses occurred in two patients, and two died of transplant-related causes. Eight patients remain in remission with a median follow-up of 31 months after the BMT. The event-free survival rate for this series is 64% (95% confidence interval, 27%-85%). The roles of pretransplant chemotherapy and splenectomy for leukemic reduction to prevent relapse, and the use of conditioning regimens with total body irradiation require study in a larger series of patients. GVHD may be beneficial in preventing relapses, which has been the major cause of treatment failure for these patients.

Juvenile myelomonocytic leukemia and Noonan syndrome

A case of juvenile myelomonocytic leukemia (JMML, previously referred to as JCML) in a neonate with Noonan syndrome (NS) is described. The boy presented with bilateral congenital hydrothoraces, nonimmune hydrops, dysmorphic facies, persistent thrombocytopenia, and leukocytosis. The diagnosis of JMML was made on bone marrow cell culture studies. Review of the literature reveals an unusual preponderance of hematologic malignancies, in particular JMML, among patients with NS. Of 40 NS patients admitted to the authors' institution during a 10-year period, there were 4 (10%) with evidence of a monocytic proliferation, which resolved spontaneously. The authors postulate that patients with NS may have an increased incidence of myeloproliferative disorders, which in most cases appears to be benign but may be preleukemic or even lethal.

p53 gene status and chemosensitivity of childhood acute lymphoblastic leukemia cells to adriamycin

The role of p53 as a determinant of sensitivity of ten childhood acute lymphoblastic leukemia (ALL) cell lines to Adriamycin (ADR) was investigated. ADR-sensitive cell lines were found to have wild-type (wt) p53, whereas resistant cell lines contained point mutations in the gene. The basal level of wt p53 protein in sensitive cells was lower than that of mutant p53 in resistant cells, however, after ADR treatment a 6- to 20-fold dose-dependent increase in wt p53 was observed, whereas mutant p53 increased only twofold. The percentage of apoptotic cells in ADR-sensitive lines with wt p53 ranged from 43 to 93% following ADR treatment, whereas that in resistant lines with mutant p53 was only 8-13%. The ratio of constitutive levels of Bax/Bcl-2 was significantly higher in cells containing wt p53 than in cells with mutant p53. These results suggest that p53 gene status and the ability of p53 to induce apoptosis may be determinants of sensitivity to ADR in childhood ALL cells.