Thrombopoietin (TPO), the ligand for c-mpl receptor, has been purified by investigators in a number of laboratories using different strategies. TPO supports the proliferation, differentiation and maturation of megakaryocytes and their precursors, and results in their terminal fragmentation into platelets. TPO appeared initially to act as a lineage-specific late-acting hematopoietic growth factor, like the effects of erythropoietin and granulocyte colony-stimulating factor on erythropoiesis and myelopoiesis, respectively. However, several groups have now shown that myelopoiesis and erythropoiesis are also affected by TPO. TPO acted in synergy with EPO to increase the growth of erythroid porliferation from bone marrow cells. Furthermore, TPO interacted with the steel factor, the ligand for flk2/flt3, and/or interleukin-3 to support the formation of multiple types of hematopoietic colonies from a highly purified population of hematopoietic progenitors. Mice lacking c-mpl revealed a reduced number of hematopoietic progenitors including multipotential, blast cell and committed progenitors as well as a deficiency of megakaryocytic progenitors in the culture. The administration of TPO ameliorated the depth and duration of thrombocytopenia, and the severity of leukopenia and anemia in mice treated with a combination of carboplatin and irradiation. These observations indicate that the effects of TPO on hematopoiesis are greater than initially anticipated. TPO may be an important cytokine for the manipulation of human hematopoietic stem cells in synergy with other early-acting factors.

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In a study by the Children's Cancer and Leukemia Study Group (CCLSG), it was observed that event free survival (EFS) improved steadily through the CCLSG-811 to 911 protocols for children with standard-risk (SR) acute lymphoblastic leukemia (ALL). The stratification of prognostic groups according to age and leuko-cyte count at diagnosis is the same in all CCLSG studies of ALL. The EFS rate at 14 years was 65.4% for the intermittent cyclic regimen of an intermediate-dose of methotrexate (MTX) plus 6-mercaptopurine (6MP). This regimen has become a standard for maintenance chemotherapy since the 841 protocol of CCLSG. In the 841 protocol, L-asparaginase (L-asp) containing induction therapy improved the EFS rate. In the 874 protocol, there was no significant difference between the two regimens, with and without cranial irradiation, in preventing central nervous system leukemia. The objectives of CCLSG studies are to obtain meaningful and reasonable results, introduce new concepts and prove them to all investigators based on previous studies. The usefulness of the dose escalation of 6MP, 24-hour infusion of MTX without CF rescue and the phamacokinetic variation of 6MP, as well as the usefulness of an intermittent and cyclic regimen of L-asp, will be clarified in ongoing prospective studies.

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In patients who developed graft-vs-host disease following allogeneic bone marrow transplantation, the incidence of leukemia relapse is decreased as a result of the graft-vs-leukemia (GVL) effect. In cord blood stem cell transplantation, it is not known if the GVL effect exists. We have investigated the possibility of generating cytotoxic T lymphocytes (CTL) in a mixed lymphocyte culture (MLC). The MLC was set up using cord blood mononuclear cells as responders and the irradiated mononuclear cells of a healthy adult as stimulators. After seven days, the CTL activity was measured. In 17 out of 20 cord blood samples, alloreactive CTL was generated. A simultaneous flow cytometric analysis revealed that CD8+CD45RO+ cells markedly increased following MLC. These in vitro results suggest that the GVL effect may operate in vivo in cord blood stem cell transplantation

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We administered a combination of chemotherapy, autologous bone marrow purged with magnet immunobeads and total body irradiation (TBI) for advanced neuroblastoma (NB). The effect of TBI was retrospectively studied with regard to hematological recovery and complications after autologous bone marrow transplantation (A-BMT). The bone marrow was engrafted in all patients, both recipients and non-recipients of TBI. In patients receiving TBI, the average number of days after A-BMT required for the white blood cell count to exceed 1, 000/μl, the neutrophile count to exceed 500/μl and the platelet count to exceed 5.0×10⁴/μl was 15.0±6.5, 16.0±6.4 and 59.7±24.4, respectively. In patients not receiving TBI, the corresponding figures were 12.2±6.2, 12.9±6.9 and 43.2±17.8 days, respectively. During hematological recovery after A-BMT, there was no statistical difference between patients having received TBI and those who did not receive TBI. Hemolytic uremic syndrome (HUS) was observed in four patients while receiving TBI, but no HUS developed after shielding the kidney from TBI. In terms of engraftment and complications, A-BMT can be performed on patients receiving TBI as safely as on those patients not receiving TBI.

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We performed bone marrow transplantation (BMT) on a male patient with severe aplastic anemia (SAA) who had received blood and/or platelet transfusions many times because of a resistance to all treatments. The total volume of transfusions was 34, 600ml. As the conditioning for BMT, CY, TLI and TBI were used. About 10 months was required for the reproliferation of bone marrow (BM) cells, including red cells, leukocytes and platelets. To confirm whether the condition of his BM cells was chimeric or had transferred to the donor type completely, we conducted a polymorphic examination using genomic DNA extracted from the peripheral leukocytes of his family and from his hair root cells. The results indicated that his BM cells had changed to donor-type cells completely. The possibilities of his prolonged hematopoietic recovery were as follows : (1) a long period of time is required to improve the microenvironment surrounding the BM; (2) the chimeric condition of donor-type cells and recipient cells continues after BMT, and requires a long period of time to change to donor-type cells; and (3) both (1) and (2).

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A 5-year-old boy was admitted to our hospital with a high fever and purpura. His peripheral blood presented pancytopenia ; WBC 2, 300/μl (12.5% of blast), Hb 6.4g/dl and platelets 63, 000/μl. LDH and ferritin were elevated to 3552IU/l and 9046ng/ml, respectively. Pancytopenia progressed rapidly, and improved only when supportive therapy was performed. The serum levels of LDH and ferritin also decreased. A relation to hypercytokinemia was suspected. We diagnosed him as having MDS accompanied by myelofibrosis following a bone marrow biopsy. A chromosomal analysis showed monosomy 7. Reports of pediatric MDS accompanied by myelofibrosis are rare. This report describes a case of pediatric MDS accompanied by myelofibrosis.

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We report a case of atypical Philadelphia chromosome (ph¹) -positive acute lymphoblastic leukemia (ALL) accompanied by the development of hemolytic uremic syndrome (HUS) five months after a bone marrow transplant (BMT). The patient, a 2-year-9-month old girl, was diagnosed as having ALL at the age of 1-year and 9-months. She received bone marrow from an HLA identical, MLC-negative 5-year-old sister during her second complete remission. At 142 days post-transplant, she had a loss of appetite, pyrexia, whitish aqueous stools, blepharedema and hematuria. Her laboratory tests revealed RBC 346 × 10⁴/μl, Hb 9.5 g/dl, reticulocytes 18% with fragmented red blood cells, LDH 513 IU/l, BUN 28.1 mg/dl and haptoglobin 10 mg/dl. A urinalysis revealed protein and occult blood. Based on the data, HUS was diagnosed. A stool sample tested positive for rotavirus antigen. E. coli was not cultured in the stool however, VT antibody was detected in the serum. We strongly believe the cause of HUS in this case was infection with a mixture of rotavirus and E. coll.

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We report here a case of recurrent metastatic medulloblastoma following treatment with peripheral blood-stem cell transplantation (PBSCT). A 16-year-old boy who had undergone surgery, radiation therapy and chemotherapy for cerebellar medulloblastoma at the age of 8 yr achieved complete remission. However, six years after the first treatment, he developed multiple bone metastases. Moreover two years after the first relapse, a bone marrow relapse occurred, followed by brain metastases two years later. The patient was treated with vincristine, cyclophosphamide, pirarubicin, etoposide (VP-16), etc., but he failed to achieve complete remission. High-dose chemotherapy with carboplatin+ melphalan+ VP-16 and PBSCT (1.25×10⁸ mononuclear cells/kg and 0.99×10⁵ CFU-GM/kg) were performed. From day 1 to day 15, he received granulocyte colony-stimulating factor. The absolute neutrophil count reached 500/μl on day 10, platelet count reached 50, 000/μl on day 16 and the reticulocyte count reached 1% on day 14. A bone scan and brain MRI survey for metastatic lesions on day 25 gave no evidence of residual tumors. But seven months after the PBSCT, he complained of bone pain. An additional bone scan and brain MRI revealed new metastatic sites. He was then treated using radiation and chemotherapies. The use of PBSCT for recurrent metastatic medulloblastoma may be of value but transiently. Further discussion about the timing and selection of anti-cancer drugs for PBSCT is required.

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We report on a one-year-old girl with infantile acute lymphocytic leukemia (ALL) who received a transplant with CD34+ marrow cells from her HLA two-loci mismatched father. The CD34+ marrow cells were selected using an Isolex 50 Cell Separation System^TM. A total of 7.25 × 10⁶/kg CD34+ cells were infused to the patient with 1.57 × 10⁴/kg of CD5 + cells. The conditioning regimen consisted of total body irradiation, busulfan, cyclophosphamide and anti-thymocyte globulin. Cyclosporin A (3 mg/kg) and prednisolone (1 mg/ kg) were administered for the prophylaxis of graft-versus-host disease (GVHD). White blood cell counts and reticulocyte counts increased promptly, but recovery of the platelet count was delayed. No clinical symptoms of acute GVHD were noted. A chromosomal analysis of the bone marrow cells for sex mismatch revealed complete chimerism on day + 14, but mixed chimerism on day +28. For the treatment of mixed chimerism, 1 × 10⁶-10⁷/ kg of the donor's lymphocytes were infused to the patient, inducing GVHD. The GVHD became uncontrollable after immunosuppressive therapies, and the patient died. Selective CD34+ marrow cell transplantation from HLA-mismatched donors may be one of the curable methods for poor-prognosis patients without available donors, however, further evaluation for mixed chimerism or relapse is needed.

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A 31-day-old Japanese female was admitted to our hospital because of fever and leukocytosis. The peripheral white blood cell count was 63, 400/μl and a bone marrow examination showed 91.2% lymphoblasts of FAB L1 and karyotype of 46, XX, t (4 ; 11) (q21 ; q23). The immunophenotypes of the leukemic cells were HLA-DR (+), CD10 (-), CD19 (+) and CD20 (-). Early pre-B cell congenital acute lymphoblastic leukemia with CNS infiltration was diagnosed. Remission induction therapy for ALL protocol, CNS leukemia therapy with irradiation and reinforcement therapy for ANLL protocol were performed. Complete continuous remission was maintained for three years and she was removed from therapy. Today, the girl, who is now nine years and one month old, shows no psychomotor complications and seems to be enjoying life fully. Among the 22 reported cases of congenital ALL with t (4 ; 11), our patient is the longest surviving case.

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A one year-old boy with non-Hodgkin's lymphoma (abdominal primary, Stage IV) showed dissemination of the testes, bone marrow and central nervous system (CNS) at the time of diagnosis. During systemic induction chemotherapy, the patient manifested hypopyon in the left eye. An aspiration smear of the hypopyon confirmed the infiltration of lymphoma cells. For this eye lesion, we applied chemotherapy combined with high doses of methotrexate (MTX), which was effective to induce remission. Subsequent relapses in the bone marrow and CNS have been conquered, and the patient is in remission 12 months after the onset of NHL (10 months from the onset of hypopyon). High doses of MTX are believed to be useful for treatment of lymphomatous lesions in the anterior chamber of the eye, which is considered to be one of the pharmacological sanctuaries.

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