Shigetaka Asano

EFFECT OF MATCHING OF CLASS I HLA ALLELES ON CLINICAL OUTCOME AFTER TRANSPLANTATION OF HEMATOPOIETIC STEM CELLS FROM AN UNRELATED DONOR

BACKGROUND The requirements with respect to HLA compatibility and the relative importance of matching for individual class I and class II HLA alleles in the transplantation of hematopoietic stem cells from unrelated donors have not yet been established. METHODS We performed retrospective DNA typing of alleles at 11 polymorphic loci of HLA genes in 440 recipients of hematopoietic stem cells from unrelated donors who were serologically identical with their respective recipients for HLA-A, B, and DR antigens. Of these recipients, 80 percent had leukemia; the rest had lymphoma, marrow failure, or a congenital disorder. RESULTS Multivariate analysis showed that incompatibility for HLA-A alleles and incompatibility for HLA-C alleles were independent risk factors for severe acute graft-versus-host disease (GVHD) (HLA-A, P=0.006; HLA-C, P=0.001). Mismatching of HLA-A, but not of HLA-C, alleles was an independent risk factor for death (P<0.001). Matching [corrected] of HLA-C alleles was a significant risk factor for relapse of leukemia (P=0.035). HLA-B disparity was a significant risk factor for both GVHD and death in the univariate analysis, but not in multivariate analysis. Disparities in class II HLA alleles of the DRB1, DQA1, DQB1, DPA1, and DPB1 loci were not identified as significant risk factors for acute GVHD or death in the multivariate analysis. CONCLUSIONS Genomic typing of class I HLA alleles adds substantially to the success of transplantation of hematopoietic stem cells from unrelated donors, even if the donors are serologically identical to their recipients with respect to HLA-A, B, and DR antigens.

The chromosomal gene structure and two mRNAs for human granulocyte colony-stimulating factor.

Two different cDNAs for human granulocyte colony‐stimulating factor (G‐CSF) were isolated from a cDNA library constructed with mRNA prepared from human squamous carcinoma cells, which produce G‐CSF constitutively. The nucleotide sequence analysis of both cDNAs indicated that two polypeptides coded by these cDNAs are different at one position where three amino acids are deleted/inserted. When the two cDNAs were introduced into monkey COS cells under the SV40 early promoter, both of them produced proteins having authentic G‐CSF activity and some difference in the specific activity was suggested. A human gene library was then screened with the G‐CSF cDNA and the DNA fragment containing the G‐CSF chromosomal gene was characterized by the nucleotide sequence analysis. The human G‐CSF gene is interrupted by four introns and a comparison of the structures of the two G‐CSF cDNAs with that of the chromosomal gene indicated that the two mRNAs are generated by alternative use of two 5′ splice donor sequences in the second intron of the G‐CSF gene. When the G‐CSF chromosomal gene was expressed in monkey COS cells by using the SV40 enhancer two mRNAs were detected by S1 mapping analysis.

Purification and characterization of human granulocyte colony-stimulating factor (G-CSF).

A colony‐stimulating factor (CSF) has been purified to homogeneity from the serum‐free medium conditioned by one of the human CSF‐producing tumor cell lines, CHU‐2. The molecule was a hydrophobic glycoprotein (mol. wt 19,000, pI = 6.1 as asialo form) with possible O‐linked glycosides. Amino acid sequence determination of the molecule gave a single NH2‐terminal sequence which had no homology to the corresponding sequence of the other CSFs previously reported. The biological activity was apparently specific for a neutrophilic granulocyte‐lineage of both human and mouse bone marrow cells with a specific activity of 2.7 X 10(8) colonies/10(5) non‐adherent human bone marrow cells/mg protein. The purified CSF can be regarded as a G‐CSF of human origin and will become a useful material for investigation of regulatory mechanisms of human granulopoiesis.

Establishment of Novel Embryonic Stem Cell Lines Derived from the Common Marmoset (Callithrix jacchus)

The successful establishment of human embryonic stem cell (hESC) lines has inaugurated a new era in regenerative medicine by facilitating the transplantation of differentiated ESCs to specific organs. However, problems with the safety and efficacy of hESC therapy in vivo remain to be resolved. Preclinical studies using animal model systems, including nonhuman primates, are essential to evaluate the safety and efficacy of hESC therapies. Previously, we demonstrated that common marmosets are suitable laboratory animal models for preclinical studies of hematopoietic stem cell therapies. As this animal model is also applicable to preclinical trials of ESC therapies, we have established novel common marmoset ESC (CMESC) lines. To obtain marmoset embryos, we developed a new embryo collection system, in which blastocysts can be obtained every 3 weeks from each marmoset pair. The inner cell mass was isolated by immunosurgery and plated on a mouse embryonic feeder layer. Some of the CMESC lines were cultured continuously for more than 1 year. These CMESC lines showed alkaline phosphatase activity and expressed stage‐specific embryonic antigen (SSEA)‐3, SSEA‐4, TRA‐1‐60, and TRA‐1‐81. On the other hand, SSEA‐1 was not detected. Furthermore, our novel CMESCs are pluripotent, as evidenced by in vivo teratoma formation in immunodeficient mice and in vitro differentiation experiments. Our established CMESC lines and the common marmoset provide an excellent experimental model system for understanding differentiation mechanisms, as well as the development of regenerative therapies using hESCs.

A novel allosterically trans-activated ribozyme, the maxizyme, with exceptional specificity in vitro and in vivo.

We have constructed an allosterically controllable novel enzyme (designated maxizyme) that can be transcribed in vivo under the control of a human tRNA(Val) promoter. The maxizyme has sensor arms that can recognize target sequences, and in the presence of such a target sequence only, it can form a cavity that can capture catalytically indispensable Mg2+ ions. As a target for a demonstration of the potential utility of the maxizyme, we chose BCR-ABL mRNA, the translated products of which cause chronic myelogenous leukemia. Only the maxizyme (but not conventional ribozymes) had extremely high specificity and high-level activity, not only in vitro but also in cultured cells including BV173 cells derived from a patient with a Philadelphia chromosome. The maxizyme induced apoptosis only in leukemic cells with this chromosome.

AML1(-/-) embryos do not express certain hematopoiesis-related gene transcripts including those of the PU.1 gene.

The AML1 and PEBP2β/CBFβ genes encode the DNA-binding and non-binding subunits, respectively, of the heterodimeric transcription factor, PEBP2/CBF. Targeting each gene results in an almost identical phenotype, namely the complete lack of definitive hematopoiesis in the fetal liver on embryonic day 11.5 (E11.5). We examined and compared the expression levels of various hematopoiesis-related genes in wild type embryos and in embryos mutated for AML1 or PEBP2β/CBFβ. The RNAs were prepared from the yolk sacs of E9.5 embryos, from the aorta-gonad- mesonephros regions of E11.5 embryos and from the livers of E11.5 embryos and RT–PCR was performed to detect various gene transcripts. Transcripts were detected for most of the hematopoiesis-related genes that encode transcription factors, cytokines and cytokine receptors, even in tissues from homozygously targeted embryos. On the other hand, PU.1 transcripts were never detected in any tissue of AML1(−/−) or PEBP2β/CBFβ(−/−) embryos. In addition, transcripts for the Vav, flk-2/flt-3, M-CSF receptor, G-CSF receptor and c-Myb genes were not detected in certain tissues of the (−/−) embryos. The results suggest that the expression of a particular set of hematopoiesis-related genes is closely correlated with the PEBP2/CBF function.

Induction of neutrophilic granulocytosis in mice by administration of purified human native granulocyte colony-stimulating factor (G-CSF)

Mice were subcutaneously (sc) injected once a day for up to 15 days with a purified human native G-CSF sample at a dose of 2.5 micrograms/injection or with control samples with or without added endotoxin. In the G-CSF-treated mice, blood neutrophil counts began to rise as early as 2 hours after the first injection, reached a level 8 times above the preinjection level after 15 days of injections with marked elevation of all progenitor cell levels in spleen, and returned to normal within 48 hours after cessation of the injections. Such neutrophilia was observed even when endotoxin-resistant C3H/HeJ mice were used, but not in control mice. It is possible that repeated G-CSF injections after administration of cyclophosphamide (CY) in mice could accelerate recovery of granulopoiesis with a rather transient rise in blood neutrophil counts.

IL-12 Responsiveness and Expression of IL-12 Receptor in Human Peripheral Blood Monocyte-Derived Dendritic Cells

We analyzed the expression of IL-12Rβ1 and IL-12Rβ2 and the role of IL-12 in the activation of monocyte-derived dendritic cells (DCs) via IL-12Rβ1-mediated signaling events. Flow cytometric analysis revealed that IL-12Rβ1 was expressed in T cells, Con A blasts, and monocyte-derived DCs, but not in monocytes, while its transcript was detected in all of these cell types. Transcriptional expression of IL-12Rβ2 was observed in T cells, Con A blasts, and monocyte-derived DCs, but not monocytes. The ligation of DCs as well as Con A blasts by IL-12 induced the production of GM-CSF, IL-1β, IL-6, TNF-α, and IFN-γ at the transcription levels. Furthermore, stimulation of DCs with IL-12 induced IL-12p40 transcript, but not IL-12p35 transcript, whereas this stimulation caused the expressions of both transcripts in Con A blasts. Stimulation of DCs with IL-12 caused a tyrosine phosphorylation of several intracellular proteins, and the pattern of these events were distinct from those of IL-12-stimulated Con A blasts. IL-12 also induced tyrosine phosphorylation of IL-12Rβ1 as well as recruitment of several tyrosine-phosphorylated proteins to IL-12Rβ1 in DCs and Con A blasts. Receptor engagement of DCs as well as Con A blasts by IL-12 resulted in activation of Janus kinase 2 and Tyk2 kinases and Stat3 and Stat4 transcription factors and the association of these proteins to IL-12Rβ1. Stimulation with IL-12 caused a tyrosine phosphorylation and enzymatic activity of a family of mitogen-activated protein kinases, p38mapk. These results suggest that IL-12 acts directly on DCs to induce their functional activation via IL-12Rβ1-mediated signaling events.

Natural killer cell depletion by anti-asialo GM1 antiserum treatment enhances human hematopoietic stem cell engraftment in NOD/Shi-scid mice

The scid mutation was backcrossed on to the NOD/Shi mouse background, resulting in the development of NOD/Shi-scid mice, which showed lack of mature lymphocytes, macrophage dysfunction and absence of circulating complement, but were not as impaired in natural killer (NK) cell activity as NOD/LtSz-scid mice. We then examined the effect of recipient NK cell depletion by anti-asialo GM1 antiserum on the repopulation of human cord blood (CB) hematopoietic stem cells (HSC) in NOD/Shi-scid mice to clarify the role of recipient NK cells in human HSC engraftment. The anti-asialo GM1 antiserum treatment significantly enhanced the engraftment of CB CD34+ cells, but did not affect the differentiation of the engrafted HSC into each hematopoietic lineage. The NK cell depletion was effective at early stages of the engraftment, but not 3 weeks after the transplantation. The anti-asialo GM1 antiserum treatment did not improve the engraftment by human HSC in scid mice which lack mature lymphocytes, but show neither macrophage dysfunction nor a reduction in circulating complement, indicating that macrophages and/or complement also have roles in HSC graft rejection. The present study indicates that the preconditioning targeting of recipient NK cells in addition to T cell suppression and myeloablation might prevent HSC graft failure, and that NOD/Shi-scidmice treated with anti-asialo GM1 antiserum could provide a useful tool for evaluating the repopulating ability of transplantable human HSC. Bone Marrow Transplantation (2000) 26, 1211–1216.

A phase II trial of recombinant human granulocyte colony-stimulating factor in the myelodysplastic syndromes

Summary. We conducted a phase II study of the intravenous administration of a glycosylated recombinant human granulocyte colony‐stimulating factor (rhG‐CSF) for 7–14 d in 41 patients with the myelodysplastic syndromes (MDS). Administration of rhG‐CSF elicited striking rises in both leucocyte and neutrophil counts in the majority of the patients irrespective of the FAB subtypes of MDS. The rises in neutrophil counts were dose dependent and 5 μg/kg/d of rhG‐CSF yielded approximately an 8‐fold increase in neutrophil counts. Leucocytes and neutrophil counts started to increase shortly after the first injection of 5 μg/kg, was maintained at significantly elevated levels during 14 d of treatment, and returned to the pretreatment levels within several days following discontinuation of rhG‐CSF. The action of rhG‐CSF was specific for neutrophils since leucocytosis was due exclusively to neutrophilic increase associated with an increased marrow myeloid maturation. There were no consistent changes in the monocyte, eosinophil, lymphocyte, platelet or reticulocyte counts. After treatment, the percentage of marrow blast cells was reduced in eight of 13 evaluable patients with refractory anaemia with an excess of blasts (RAEB) or RAEB in transformation (RAEB‐t). No patients developed acute leukaemia during the treatment or in the immediate follow‐up period. The treatment was well tolerated with only minimal toxicity. The results suggest that rhG‐CSF is a safe and effective way to promptly improve neutropenia in MDS patients.