ALBERT

Description: The control of tunnel contact resistance is of primary importance for semiconductor-based spintronic devices. This control is hardly achieved with conventional oxide-based tunnel barriers due to deposition-induced interface states. Manipulation of single 2D atomic crystals (such as graphene sheets) weakly interacting with their substrate might represent an alternative and efficient way to design new heterostructures for a variety of different purposes including spin injection into semiconductors. In the present paper, we study by x-ray photoemission spectroscopy the band alignments and interface chemistry of iron–graphene-hydrogenated passivated silicon (001) surfaces for a low and a high n-doping concentration. We find that the hydrogen passivation of the Si(001) surface remains efficient even with a graphene sheet on the Si(001) surface. For both doping concentrations, the semiconductor is close to flat-band conditions which indicates that the Fermi level is unpinned on the semiconductor side of the Graphene/Si(001):H interface. When iron is deposited on the graphene/Si(001):H structures, the Schottky barrier height remains mainly unaffected by the metallic overlayer with a very low barrier height for electrons, a sought-after property in semiconductor based spintronic devices. Finally, we demonstrate that the graphene layer intercalated between the metal and semiconductor also serves as a protection against iron-silicide formation even at elevated temperatures preventing from the formation of a Si-based magnetic dead layer.

Description: A graft-versus-leukemia (GVL) effect has been considered a major factor responsible for cures in patients with hematologic malignancies undergoing allogeneic bone marrow transplantation; however, associated graft-versus-host disease (GVHD) results in significant morbidity and mortality. T-cell depletion reduces the incidence and severity of GVHD but eliminates, at least partially, the GVL effect. Reinfusion of donor T lymphocytes at relapse posttransplantation can induce a potent antitumor response, but GVHD still occurs in the majority of patients. Prior transduction of T lymphocytes with the suicide gene, the viral thymidine kinase (TK), permits specific cell kill on administration of ganciclovir (GCV). Therefore, infusion of TK-transduced T lymphocytes may induce GVL effect and allow for their subsequent selective elimination in case GVHD develops. To evaluate the efficacy and feasibility of this promising approach, anti-CD3–stimulated primary human lymphocytes cultured in interleukin-2 were TK-transduced by a retroviral vector carrying both TK and neomycin-resistance genes. After selection in G418, more than 90% of the cells contained the TK gene as shown by a semiquantitative polymerase chain reaction. In addition, 1 to 5 days of GCV exposure, at clinically achievable concentrations of 20 to 50 μmol/L, induced ≥90% killing of G418-selected cells without affecting nontransduced cells. Correlation of the extent of T-cell kill and the proportion of TK-gene–transduced cells is consistent with the absence of a bystander effect. Transduced cells were CD3+ and either CD8+ or CD4+ and retained functional properties of untransduced cells. In vivo administration of GCV prevented tumor development after subcutaneous injection of TK-transduced murine myeloma cells (MOPC-11), whereas such an effect was not observed on injection of untransduced cells into the opposite flank. Our studies provide critical information that (1) adequate numbers of TK-transduced lymphocytes can be selected efficiently with ≥90% purity, (2) selected cells remain functional, (3) 24 hours of exposure to GCV at clinically achievable concentration effects ≥90% killing of selected cells, and (4) GCV is effective in vivo in killing TK-transduced cells. Based on these data, a clinical study has been initiated in patients with multiple myeloma with persistent or relapsing disease after T-cell–depleted allogeneic transplants.

Description: The number of CD34+ cells in the peripheral blood of cancer patients is known to be increased following the administration of high dose chemotherapy and hematopoietic growth factors. These so-called peripheral blood stem cell grafts are now frequently used for autologous transplantation of patients with malignancies. In this report, we address the question of whether true long-term repopulating pluripotent hematopoietic stem cells (PHSC) are mobilized into peripheral blood following chemotherapy plus granulocyte/macrophage colony-stimulating factor (GM-CSF) or granulocyte colony-stimulating factor (G-CSF) mobilization. We have examined the presence of stem cells in mobilized peripheral blood (MPB) by using an antibody to the human Thy-1 molecule to stain the CD34+Lineage- (Lin-) population. The kinetics of mobilization of CD34+Thy-1+ Lin- cells into peripheral blood were studied, and the percentage of cells with this phenotype was found to vary widely depending on the day of leukapheresis. A CD34+Thy- 1+Lin- cell population, potentially containing PHSCs, was isolated by fluorescence activated cell sorting (FACS) and analyzed for activity. The multilineage differentiative capacity of this candidate stem cell- containing population in MPB was determined using an in vitro long-term culture system, in which cobblestone area formation was used as a means of detecting PHSCs. We also measured repopulating capacity by using two in vivo models in which severe combined immunodeficiency (SCID)-hu mice were implanted with human fetal bone or thymus grafts. Using these assays, we show that the highest frequency of cobblestone area-forming cells (CAFC) after 7 weeks of culture was observed in a subpopulation of CD34+Lin- cells, which expressed low levels of Thy-1. This cell population was capable of producing both B and myeloid cells, and maintaining CD34+Lin- cells in these long term cultures. Moreover, the CD34+Thy-1+Lin- cell subset possessed a higher ability to engraft and to demonstrate multilineage differentiative potential at 8 weeks in the SCID-hu bone assay. However, in the SCID-hu thymus model, both Thy-1+ and Thy-1- subpopulations were capable of donor T-cell engraftment at 6 weeks, suggesting the presence of cells capable of initiating T lymphopoiesis in both populations.(ABSTRACT TRUNCATED AT 400 WORDS)

Description: Chronic myeloid leukemia (CML) is a malignant disorder of the hematopoietic stem cell. It has been shown that normal stem cells coexist with malignant stem cells in the bone marrow of patients with chronic-phase CML. To characterize the primitive hematopoietic progenitor cells within CML marrow, CD34+DR- and CD34+DR+ cells were isolated using centrifugal elutriation, monoclonal antibody labeling, and flow cytometric cell sorting. Polymerase chain reaction analysis of RNA samples from these CD34+ subpopulations was used to detect the presence of the BCR/ABL translocation characteristic of CML. The CD34+DR+ subpopulation contained BCR/ABL(+) cells in 11 of 12 marrow samples studied, whereas the CD34+DR- subpopulation contained BCR/ABL(+) cells in 6 of 9 CML marrow specimens. These cell populations were assayed for hematopoietic progenitor cells, and individual hematopoietic colonies were analyzed by PCR for their BCR/ABL status. Results from six patients showed that nearly half of the myeloid colonies cloned from CD34+DR- cells were BCR/ABL(+), although the CD34+DR- subpopulation contained significantly fewer BCR/ABL(+) progenitor cells than either low-density bone marrow (LDBM) or the CD34+DR+ fraction. These CD34+ cells were also used to establish stromal cell-free long-term bone marrow cultures to assess the BCR/ABL status of hematopoietic stem cells within these CML marrow populations. After 28 days in culture, three of five cultures initiated with CD34+DR- cells produced BCR/ABL(-) cells. By contrast, only one of eight cultures initiated with CD34+DR+ cells were BCR/ABL(-) after 28 days. These results indicate that the CD34+DR- subpopulation of CML marrow still contains leukemic progenitor cells, although to a lesser extent than either LDBM or CD34+DR+ cells.

Description: Between August 1990 and August 1995, 231 patients (median age 51, 53% Durie-Salmon stage III, median serum β-2-microglobulin 3.1 g/L, median C-reactive protein 4 g/L) with symptomatic multiple myeloma were enrolled in a program that used a series of induction regimens and two cycles of high-dose therapy (“Total Therapy”). Remission induction utilized non–cross-resistant regimens (vincristine-doxorubicin-dexamethasone [VAD], high-dose cyclophosphamide and granulocyte-macrophage colony-stimulating factor with peripheral blood stem cell collection, and etoposide-dexamethasone-cytarabine-cisplatin). The first high-dose treatment comprised melphalan 200 mg/m2 and was repeated if complete (CR) or partial (PR) remission was maintained after the first transplant; in case of less than PR, total body irradiation or cyclophosphamide was added. Interferon--2b maintenance was used after the second autotransplant. Fourteen patients with HLA-compatible donors underwent an allograft as their second high-dose therapy cycle. Eighty-eight percent completed induction therapy whereas first and second transplants were performed in 84% and 71% (the majority within 8 and 15 months, respectively). Eight patients (3%) died of toxicity during induction, and 2 (1%) and 6 (4%) during the two transplants. True CR and at least a PR (PR plus CR) were obtained in 5% (34%) after VAD, 15% (65%) at the end of induction, and 26% (75%) after the first and 41% (83%) after the second transplants (intent-to-treat). Median overall (OS) and event-free (EFS) survival durations were 68 and 43 months, respectively. Actuarial 5-year OS and EFS rates were 58% and 42%, respectively. The median time to disease progression or relapse was 52 months. Among the 94 patients achieving CR, the median CR duration was 50 months. On multivariate analysis, superior EFS and OS were observed in the absence of unfavorable karyotypes (11q breakpoint abnormalities, -13 or 13-q) and with low β-2-microglobulin at diagnosis. CR duration was significantly longer with early onset of CR and favorable karyotypes. Time-dependent covariate analysis suggested that timely application of a second transplant extended both EFS and OS significantly, independent of cytogenetics and β-2-microglobulin. Total Therapy represents a comprehensive treatment approach for newly diagnosed myeloma patients, using multi-regimen induction and tandem transplantation followed by interferon maintenance. As a result, the proportion of patients attaining CR increased progressively with continuing therapy. This observation is particularly important because CR is a sine qua non for long-term disease control and, eventually, cure.

Description: One hundred and thirty-five patients with advanced and refractory myeloma received one of three high-dose therapy regimens: melphalan at doses of 90 to 100 mg/m2 (MEL 100; 47 patients) without autotransplant; total body irradiation (TBI; 850 cGy) with either melphalan 140 mg/m2 or thiotepa 750 mg/m2 and autologous bone marrow transplant (ABMT) (〈 or = 30% plasma cells; 21 patients); melphalan 200 mg/m2 (MEL 200) supported by both peripheral blood stem cells (PBSC) and ABMT plus GM- CSF intended as a double-transplant program (67 patients; 42 have completed and 3 are still awaiting a second autotransplant; 5 additional patients received an allograft for their second transplant). Mortality within 2 months of therapy was 20% to 25% with MEL 100 and TBI regimens, but less than 1% with MEL 200, mainly because severe neutropenia (〈 500/microL) was shortened to less than 1 week due to infusion of PBSC and use of growth factor therapy. Low beta 2- microglobulin (beta 2M) levels 〈 or = 2.5 mg/L and MEL 200 therapy were identified as the two most important independent favorable variables associated with prolonged event-free survival (EFS) and overall survival (OS). On the basis of these two parameters, three risk groups were defined: 29 good-risk patients with low beta 2M receiving MEL 200 had the best outcome, with median durations of EFS of 37 months and projected OS of 〉 or = 43 months; 54 intermediate-risk patients displaying one of the two favorable parameters had EFS and OS durations of 16 and 36 months, respectively; and 52 poor-risk patients with high beta 2M not receiving MEL 200 had a dismal prognosis, with EFS of 3 months and OS of 5 months (all P 〉 .0001). Further analysis that excluded treatment as a variable identified high beta 2M and resistant relapse as the two major adverse prognostic factors, one of which was present in 80% of the 135 patients. Among these 108 high-risk patients, prognosis was improved markedly with MEL 200 because of both better supportive care (PBSC and hematopoietic growth factors) and more intensive therapy using the double-transplant approach. This study supports the concept that safer and potentially more-effective therapies can be developed in the setting of advanced and resistant disease.

Description: Unfractionated peripheral blood stem cell (PBSC) grafts contain measurable quantities of myeloma cells and are therefore a potential source of relapse posttransplantation. In contrast, fluorescence-activated cell sorting (FACS)-sorted CD34+Thy1+ Lin− peripheral blood cells are substantially enriched for stem cell activity, yet contain virtually no clonal myeloma cells. A study was performed in patients with symptomatic myeloma, who had received 12 months or less of preceding standard chemotherapy, to evaluate the feasibility of large scale purification of primitive hematopoietic stem cells in order to study engraftment kinetics posttransplantation and the degree of tumor cell contamination of this cell population, based on polymerase chain reaction (PCR) analysis for the patient-specific complementarity-determining region III (CDR III). PBSC were mobilized with high dose cyclophosphamide and granulocyte-macrophage colony-stimulating factor (GM-CSF). A combination of elutriation and chemical lysis was used to deplete PBSC collections of monocytes, granulocytes, erythrocytes, and platelets. Subsequently, CD34+ Thy1+ Lin−progenitor cells were purified with high speed cell sorting. Of the 10 evaluable patients, nine met the required minimum criteria of ≥7.2 × 105 cells/kg to support tandem transplants. After high dose melphalan (200 mg/m2) eight engrafted successfully, although granulocyte (absolute neutrophil count [ANC] 〉0.5 × 109/L, 16 days) and platelet recovery (platelets 〉 50 × 109/L, 39 days) was substantially delayed when compared with unmanipulated PBSC grafts; one patient required infusion of a reserve graft because of lack of evidence of engraftment by day +28. Three patients proceeded to a second graft with high dose melphalan and total body irradiation; two required infusion of a reserve graft and both died of infectious complications; one showed delayed, but complete, engraftment after this myeloablative regimen. Two of the nine evaluable patients attained a clinical complete remission (CR). The grafts from three patients were tested for tumor contamination and contained no detectable clonal myeloma cells. Larger quantities of purified cells may be required to resolve the problem of delayed engraftment.

Description: High-dose therapy with autologous marrow or peripheral blood stem cell (PBSC) rescue has been extensively applied in the treatment of multiple myeloma (MM) patients during the past 10 years resulting in improved event-free and overall survival when compared with standard chemotherapy. However, relapses are common and cure is unlikely in the majority of patients. Because both bone marrow and PBSCs are contaminated with myeloma cells it is conceivable that relapse after autotransplantation originates at least in part from autografted tumor cells. In this study, mobilized PBSCs were examined for the presence of myeloma cells based on immunophenotyping and sensitive polymerase chain reaction (PCR)-based techniques. In addition, CD34+ Lin- Thy+ stem cells were purified from mobilized PBSC harvests of 10 MM patients by sequentially using counterflow elutriation centrifugation, treatment with phenylalanine methylester, and flow sorting, using 5-parameter gating (propidium iodide, forward scatter, side scatter, CD34+ v Lin- and CD34+ v Thy+). Virtually all mobilized unsorted PBSC preparations contained myeloma cells in sufficient quantities (range, 〈 0.01 to 〉 10%) potentially causing a disease relapse. Stem cell purification led to an overall enrichment by about 50-fold in all 10 patients; approximately 90% of the final cell population expressed CD34+ Lin- Thy+ with no evidence of myeloma cell contamination based on flow cytometric analysis of CD38bright cells (〈 0.1%). Quantitative PCR amplification of patient-specific complementarity determining region III (CDRIII) DNA sequences showed depletion of clonal B cells by 2.7 to 7.3 logs, with the highest log reduction noted in the samples initially containing the most tumor cells. Our results show that purification of CD34+ Lin- Thy+ cells depletes myeloma cells to undetectable levels from up to 10% present in unsorted PBSCs, thus offering a tool to investigate whether MM relapse after autotransplantation can be reduced markedly.

Description: The number of CD34+ cells in the peripheral blood of cancer patients is known to be increased following the administration of high dose chemotherapy and hematopoietic growth factors. These so-called peripheral blood stem cell grafts are now frequently used for autologous transplantation of patients with malignancies. In this report, we address the question of whether true long-term repopulating pluripotent hematopoietic stem cells (PHSC) are mobilized into peripheral blood following chemotherapy plus granulocyte/macrophage colony-stimulating factor (GM-CSF) or granulocyte colony-stimulating factor (G-CSF) mobilization. We have examined the presence of stem cells in mobilized peripheral blood (MPB) by using an antibody to the human Thy-1 molecule to stain the CD34+Lineage- (Lin-) population. The kinetics of mobilization of CD34+Thy-1+ Lin- cells into peripheral blood were studied, and the percentage of cells with this phenotype was found to vary widely depending on the day of leukapheresis. A CD34+Thy- 1+Lin- cell population, potentially containing PHSCs, was isolated by fluorescence activated cell sorting (FACS) and analyzed for activity. The multilineage differentiative capacity of this candidate stem cell- containing population in MPB was determined using an in vitro long-term culture system, in which cobblestone area formation was used as a means of detecting PHSCs. We also measured repopulating capacity by using two in vivo models in which severe combined immunodeficiency (SCID)-hu mice were implanted with human fetal bone or thymus grafts. Using these assays, we show that the highest frequency of cobblestone area-forming cells (CAFC) after 7 weeks of culture was observed in a subpopulation of CD34+Lin- cells, which expressed low levels of Thy-1. This cell population was capable of producing both B and myeloid cells, and maintaining CD34+Lin- cells in these long term cultures. Moreover, the CD34+Thy-1+Lin- cell subset possessed a higher ability to engraft and to demonstrate multilineage differentiative potential at 8 weeks in the SCID-hu bone assay. However, in the SCID-hu thymus model, both Thy-1+ and Thy-1- subpopulations were capable of donor T-cell engraftment at 6 weeks, suggesting the presence of cells capable of initiating T lymphopoiesis in both populations.(ABSTRACT TRUNCATED AT 400 WORDS)

Description: We present four patients with acute nonlymphocytic leukemia, one M2 and three M4 French-American-British (FAB) types and one patient with refractory anemia with excess of blasts in transformation who at diagnosis had trisomy of chromosome 4 as the primary karyotypic anomaly. This chromosome anomaly probably defines a previously undescribed subset of acute nonlymphoid leukemias. Hematologic characteristics commonly found in these patients were dysplastic features of all bone marrow lineages, suggesting that trisomy 4- associated disorders involve the early myeloid hematopoietic stem cell.