嶋田 明

Of 11 children with juvenile myelomonocytic leukemia (JMML) carrying RAS mutations (8 with NRAS mutations, 3 with KRAS2 mutations), 5 had a profound elevation in either or both the white blood cells and spleen size at diagnosis. Three patients had no or modest hepatosplenomegaly and mild leukocytosis at presentation but subsequently showed a marked increase in spleen size with or without hematologic exacerbation, for which nonintensive chemotherapy was initiated. The other three patients with NRAS or KRAS2 glycine to serine substitution received no chemotherapy, but hematologic improvement has been observed during a 2- to 4-year follow up. In the third group, all hematopoietic cell lineages analyzed had the RAS mutations at the time of hematologic improvement, whereas DNA obtained from the nails had the wild type. Additionally, numbers of circulating granulocyte-macrophage progenitors were significantly reduced during the clinical course. Thus, some patients with JMML with specific RAS mutations may have spontaneously improving disease.

Omenn syndrome (OS) is a form of severe combined immunodeficiency (SCID) characterized by erythrodermia, hepatosplenomegaly, lymphadenopathy, and alopecia. In patients with OS, B cells are mostly absent, T-cell counts are normal to elevated, and T cells are frequently activated and express a restricted T-cell receptor (TCR) repertoire. Thus far, inherited hypomorphic mutations of the recombination activating genes either 1 or 2 (RAG1/2) have been detected in most OS patients. We have recently experienced a rare case of OS showing the revertant mosaicism due to multiple second-site mutations leading to typical OS clinical features with RAG1-deficient SCID. In this review, we will focus on the variation of several phenotypes of OS.

PTPN11 has been identified as a causative gene in Noonan syndrome (NS), responsible for about 50% of cases of NS. Given the association between NS and an increased risk of some malignancies, notably leukemia and probably some solid tumors including neuroblastoma (NB) and rhabdomyosarcoma (RMS), recent studies have reported that gain-of-function somatic mutations in PTPN11 occur in some hematological malignancies, especially de novo juvenile myelomonocytic leukemia (JMML) and in some solid tumors such as NB, although at a low frequency. In a screen for mutations of PTPN11 in 7 cell lines and 30 fresh tumors of RMS and in 25 cell lines and 40 fresh tumors of NB, we identified a missense mutation (A72T) in an embryonal RMS patient. In the RMS samples, we also detected mutations of NRAS in 1 cell line and 1 patient; both mutations were in embryonal RMSs and had no PTPN11 mutations. No mutations of PTPN11 were detected in NB. In 95 leukemia cell lines and 261 fresh leukemia samples including 22 JMMLs, 9 kinds of missense mutations were detected in 17 leukemia samples, which included 11 (50.0%) mutations in JMML samples and lower frequencies in other hematological malignancies. Furthermore, we identified 4 (18.2%) NRAS mutations and 1 (4.5%) KRAS mutation in 5 JMML samples, 1 of which had a concomitant PTPN11 mutation. Our data suggest that mutations of PTPN11 as well as RAS play a role in the pathogenesis of not only myeloid hematological malignancies but also a subset of RMS malignancies.

Patients with t(8;21) acute myeloid leukemia (AML) are considered to have a good prognosis; however, approximately 50% of them relapse. The genetic alterations associated with a poor outcome in t(8;21) AML remain unknown. Recently, aberrations of receptor tyrosine kinases (RTKs) were frequently found in patients with AML. However, the prevalence and prognostic impact of RTK aberrations in pediatric t(8;21) AML remains undetermined. Here, we found the kinase domain mutations of the KIT gene in 8 (17.4%) of 46 patients with t(8;21) AML among newly diagnosed pediatric patients with AML treated on the AML99 protocol in Japan. Significant differences between patients with or without KIT mutations were observed in the 4-year overall survival (50.0% versus 97.4%, P = .001), disease-free survival (37.5% versus 94.7%, P < .001) and relapse rate (47.0% versus 2.7%, P < .001). Furthermore, FLT3 internal tandem duplication was found in only 2 (4.3%) patients. These results suggested that KIT mutations are strongly associated with a poor prognosis in pediatric t(8;21) AML.

Irinotecan is expected to become a new drug for childhood solid tumors. Sixteen children with relapsed solid tumors received irinotecan 180 mg/m2/day for 3 consecutive days, repeated once after 25 days off. Their original tumors were neuroblastoma in 7, rhabdomyosarcoma in 3, nephroblastoma and undifferentiated sarcoma in 2 each, and primitive neuroectodermal tumor and leiomyosarcoma in 1 each. The average age at trials was 6 years. Partial response was achieved in 5 (31.3%) (neuro-blastoma, rhabdomyosarcoma, nephroblastoma, undifferentiated sarcoma, and leiomyosarcoma), and decrease in tumor marker in the other 2. Irinotecan appears promising, and could become included in the first-line treatment.

A 12-year-old girl presented with a large abdominal tumor. At surgery, a huge pedunculated extraluminal tumor was found arising from the greater curvature of the stomach and invading the surrounding structures, and there were also a submucosal tumor measuring 5 x 4 x 4 cm and multiple intramural nodules beside the main tumor. These lesions, which were removed with 1.0-cm surgical margins, were immunohistochemically positive for c-kit (CD117) and CD34. A diagnosis of gastrointestinal stromal tumor (GIST) was made. The huge size of the tumor (3.6 kg in weight and 36 x 25 x 25 cm in diameter), the invasion of the surrounding structures, and the increased mitotic figures indicated the GIST had malignant potential. Sequence analysis of the polymerase chain reaction product of RNAs from the tumor cells revealed a novel platelet-derived growth factor receptor alpha (PDGFRA) mutation, which would exhibit biologic consequences similar to those of the c-kit mutation. The patient underwent a 3-month course of imatinib mesylate as adjuvant chemotherapy because of the possible risk for tumor recurrence. She is now doing well without any evidence of recurrence or metastasis 25 months after the surgery. Only 9 cases of GIST have been reported in children, and a review of those cases revealed GISTs in children would be associated with a better prognosis than in adults and that one third of pediatric GISTs presented with intestinal obstruction in the newborn period.

Omenn syndrome (OS) is a rare primary immunodeficiency characterized by the presence of activated/oligoclonal T cells, eosinophilia, and the absence of circulating B cells. OS patients carry leaky mutations of recombination activating genes (RAG1 or RAG2) resulting in partial V(D)J recombination activity, whereas null mutations cause severe combined immunodeficiency with absence of mature T and B cells (T-B- SCID). Here we describe somatic mosaicism due to multiple second-site mutations in a patient with RAG1 deficiency. We found that he is homozygous for a single base deletion in the RAG1 gene, which results in frameshift and likely abrogates the protein function. However, the patient showed typical OS features. Molecular analysis revealed that several second-site mutations, all of which restored the RAG1 reading frame and resulted in missense mutations, were demonstrated in his T cells. These findings suggest that his revertant T-cell mosaicism is responsible for OS phenotype switched from T-B- SCID.

The prognosis for children with Wilms' tumor is reported to be excellent in those who are less than 2 years of age at diagnosis and who have a stage I/favorable-histology tumor with specimen weight less than 550 g. We report on a patient with Wilms' tumor who belonged to this group but who developed pulmonary metastases, and we discuss the diagnostic and therapeutic problems in such patients. The importance of careful evaluation of the renal sinus should be emphasized.

A transient myeloproliferative disorder (TMD) occurs in 10% of the infants with Down syndrome. While most cases resolve within a few months, in 20% of them TMDs are life-threatening or fatal. We encountered 4 patients with TMD, including 1 patient who died of liver failure and disseminated intravascular coagulation. Suspecting involvement of proinflammatory cytokines, we serially assayed them in patients' sera. Cytokines were significantly more abundant in patients than in controls. Interleukins 1 and 2, tumor necrosis factor alpha, interferon gamma, and granulocyte-macrophage colony-stimulating factor were greatly increased, especially in the infant who died. Sustained cytokinemia is likely to participate in TMD pathophysiology, and very high serum concentrations might predict a poor outcome.

The aim of this paper is to clear characteristics of the obsever based robot motion controller, which observer estimates disturbance torque and velocity.<BR>Generally, because of perturbation for moment of inertia, gravity, friction, and low-stiffness by its kinematic structures, robot motion becomes worse. It is well-known that the disturbance observer based controller is robust for not only actually disturbance but unknown perturbation. But we have never full knowledge of that observer, today.<BR>This paper describes the phisical means of the disturbance torque and velocity estimated observer, at first. Next, it shows how the observer which is used as way of attenuation for additional disturbance, gives influence to not-nominal model. And, I will show the influence of observer and phase-shift for chaging moment of inertia. And for low stiffness manipulators, I will clear that the observer having not-optimal poles gives worse result for motion.