Gastrointestinal stromal tumor (GIST)is a serious and predominantly sporadic tumor of the gastrointestinal tract (GIT). We attempted to review clinicopathological and molecular findings of GIST. GIST recently has been suggested to originate from the multipotential mesenchymal stem cells. Histologically, GIST is classified into spindle, epithelioid and mixed types. Tumor size, mitotic index, anatomic location and tumor rupture are the characteristics used to predict the clinical prognosis of patients. Expressions of c-kit/PDGFRA are essential for diagnosing GISTs. Activated mutant c-kit or platelet-derived growth factor receptor alpha (PDGFRA), which are potential therapeutic targets for imatinib, are constitutively expressed in most GIST. Imatinib selectively inhibits several protein tyrosine kinases and is an effective drug in malignant GISTs. More recently, sunitinib, a new KIT/PDGFRA kinase inhibitor, has been tested in patients with GIST resistant to imatinib with promising results.

To realize regenerative medicine, it is very important to eliminate the transformed stem cells selectively included in iPS cells, ES cells and adult stem cells derived from organs, because the transformed stem cells have a risk of tumorigenesis after the cell transplantation. Ueoka et al., have developed hybrid liposomes (HL) which selectively accumulated to membranes of tumor cells and have high inhibitory effects on the growth of tumor cells along with the induction of apoptosis. Therefore, we have investigated the application of HL23 (DMPC/10 mol%C(12)(EO)(23)) to the selective elimination of transformed stem cells using hepatoblast, which we could induce from human fetal hepatocytes by the treatment of 1 mM sodium butyrate for 8 days. During the induction process, the transformed cells appeared and produced abnormal prothrombin (PIVKA-II), which is a clinical marker for hepatoma, and also formed colonies in soft agar plate, which is a criteria for neoplastic cell transformation. On the other hand, by the treatment with 0.33 mM HL23 for 96 h during the induction process, PIVKA-II production rate of the cells and colonies formed in the soft agar plate also remarkably decreased less than those of the normal cells. Furthermore, the population of hepatoblasts in the remaining cells increased about four times. These results suggest that the transformed hepatic stem cells could be selectively eliminated by the treatment of HL23, and HL treatment of the stem cells would be a useful culture method for quality control of the stem cells to reduce a risk of tumorigenesis after the cell transplantation.

Adipocytes, osteoblasts and chondrocytes derive from common mesenchymal stem cells. A number of factors were reported to regulate differentiation of multiple cell types among adipocytes, osteoblasts and chondrocytes. Thiazolidinediones are prescribed to treat diabetes in obese subjects, but recent clinical data suggested that it increases a risk of bone fracture especially in postmenopausal women. Here, we will review recent advances in the researches of mutual connection between adipocytes and bone metabolism.

Intravascular large B-cell lymphoma (IVLBCL) is an important cause of fever of unknown origin (FUO) and multiple organ failure (MOF). Earlier, most IVLBCL cases were diagnosed only postmortem; however, now, it is possible to diagnose and treat these cases antemortem. Although hematogeneous dissemination of malignant tumor cells except lymphoma is beyond the scope of present treatment regimens, IVLBCL (hematogeneous dissemination of lymphoma) can be treated by chemotherapy so correct diagnosis is important. The onset and clinical course of IVLBCL is heterogeneous. Many IVLBCL cases show rapid deterioration, but some have a relatively indolent early period that transforms to rapid progression later. Leukemic appearance is not uncommon. It is difficult to distinguish between IVLBCL and lymphomas originating from extra-nodular organs with systemic dissemination into extra-nodular organs. Minimally invasive and highly sensitive procedures are required for its accurate diagnosis: bone marrow aspiration and biopsy, and random skin biopsy are recommended. If IVLBCL is suspected, to achieve the correct diagnosis, we should avoid glucocorticoid therapy before a biopsy is obtained, even in serious cases. IVLBCL shows remarkable response to treatment with rituximab-containing chemotherapy (R-CHOP). Delayed administration of rituximab and reduced dose of chemotherapy on the first course may be initially indicated in elderly, poor performance status or cases with high tumor burden. High-dose chemotherapy with autologous hematopoietic stem cell rescue should be considered, if possible. Aggressive combination therapy with high dose methotrexate is a recent idea because of central nervous system involvement, or relapse is common and there is poor prognosis.

Age-related EBV-associated B-cell lymphoproliferative disorder is a highly aggressive lymphoma, and a standard therapy for this disease has not yet been established. A 58-year-old male was admitted to our hospital because of fever and lymphadenopathy across the whole body. Neck lymph node biopsy showed hemorrhagic and geographic necrosis with Hodgkin-like large cells against a background of small lymphocytes. The large cells were positive for CD30 and EBER. The patient was diagnosed as having age-related EBV-associated B-cell lymphoproliferative disorder. Although there was no response to CHOP therapy, he obtained partial response after 3 courses of DeVIC therapy. Because his lymphoma was highly aggressive and chemotherapy-resistant, he underwent autologous stem cell transplantation with a conditioning regimen including ranimustine, etoposide, cytarabine, and melphalan. After stem cell transplantation and subsequent radiotherapy to the residual lesion, the patient achieved complete remission. This is the first report of successful autologous stem cell transplantation for a patient with age-related EBV-associated B-cell lymphoproliferative disorder.

We developed a voluntarily climbing animal model to investigate the effect of skeletal loading on bone tissue. At the cross section of the mid-femur, climbing exercise increases outer diameter and area of cortical bone. The mechanical strength of the femur is increased. This change of cortical volume and structure is more marked in anti-gravity exercise, such as climbing and jumping, than aerobic exercise. At the bone marrow area, climbing exercise increases trabecular bone volume and osteoblast number, while it decreases fat volume and adipocyte number. Skeletal loading promotes differentiation from mesenchymal stem cells to osteoblasts and suppresses that to adipocytes by facilitating the signal through PTH÷PTHrP receptor.

Recent development and success in the field of new antiepileptic drug treatment, has resulted in the commercialization of many new drugs. The efficacy of these drugs has been assessed in many countries. Despite the progress in USA and European countries, a time lag of approximately 10 years concerning these new drugs exists in Japan. Since 2000, the above mentioned new drugs have been commercially available and are used to treat many patients with refractory epileptic seizures and verify their efficacy as well in Japan. Induced pluripotent stem (iPS) cells, which were invented in Japan are expected to accelerate the invention of more effective antiepileptic drugs in the near future.

Polymerase chain reaction analysis of short-tandem repeat (STR) markers (STR-PCR) has been used for chimerism testing to assess engraftment following hematopoietic stem cell transplantation (HSCT). We investigated the informativity of 7 STR loci (FGA, D5S818, SE33, TH01, VWF, PentaE, and D18S51) in 82 pre-HSCT DNA samples from 41 donor/recipient pairs and developed 2 multiplex STR-PCRs using VWF, SE33, and D18S51, D5S818 and FGA, respectively. The multiplex STR-PCRs could distinguish the recipients and donors in 92.7% of the cases. Dilution experiments using mixed DNA showed that the sensitivity of the multiplex STR-PCRs for detecting the minor population was 1-5%. To compare chimerism in different samples such as peripheral blood, mononuclear cells (MNC), and CD3-positive cells (CD3+), we investigated the relationship between the chimerisms at approximately day 30 post-HSCT and the interval from the day of HSCT to achievement of complete chimerism (CC) in 70 patients undergoing HSCT. CC was found in all samples of 54 patients at day 30 post-HSCT, and these samples showed CC thereafter. Eleven patients with mixed chimerism (MC) in all samples or in MNC and CD3+ showed CC at day 60-270 post-HSCT or persistent MC. The remaining 5 patients with MC in only CD3+ showed CC at day 30-60 post-HSCT. Taken together, MNC which can be separated easily may be a useful source for detecting patients who require longer time to achieve CC and those with high risk of graft failure.

Cancer stem cells (CSCs) , which are subset of tumor cells resistant to radiation and chemotherapy, are associated with malignant characteristics of tumor and possess both self-renewal ability and pluripotency for tumor formation. In the process of generating non-CSCs from CSCs, gene mutations and epigenetic changes are induced in those cells, resulting in composition of tumor tissue with heterogeneous cell population. CSCs have been recognized as the source of metastatic foci. Epithelial-mesenchymal transition (EMT) is a change in cellular phenotype characterized by the loss of cell-to-cell adhesions and the gain of migratory behaviors,which has been shown to be a critical factor for initiating cancer invasion and metastasis. However, some recent studies suggest that EMT is not essential requirement for tumor invasion and metastasis. Herein, we discuss the biological significance of CSCs and EMT in tumor invasion and metastasis.

Bone is one of the most preferential metastatic target sites for cancers. However, based on the anatomical structure of the vascular system, bone is not recognized as a preferential metastatic target. Therefore, the biological crosstalk between metastatic cancer cells and bone is critical to the development and progression of bone metastases. Bone microenvironments possess unique biological features characterized by abundant growth factors and diverse cellular network including osteoblasts, osteoclasts and hematopietic cells. Cancers develop bone metastases by utilizing these unique bone environments for colonization and bone destruction. Better understandings of precise molecular mechanisms underlying cancer and bone crosstalk would contribute to the development of new therapeutic approaches for the treatment of bone metastasis at molecular levels.

A 64-year-old man was diagnosed as having acute myeloid leukemia. We performed sequential treatment with chemotherapy and reduced-intensity stem cell transplantation from an unrelated donor while the patient was in partial remission. After engraftment, he developed acute graft-versus-host disease of the gut on day 42 and steroid therapy was started. Despite transient aggravation of diarrhea, his symptoms slowly improved and the dose of steroid was tapered. On day 159, he complained of acute left lower abdominal pain. A CT scan showed perforation of the digestive tract and ileectomy was performed. At surgery, multiple ulcers of the intestine were found and one of the ulcers was perforated. Pathologically, transmural and diffuse proliferation of atypical cells in the ulcer were confirmed. Since these cells were positive for CD20 and Epstein-Barr-virus (EBV) encoded RNA, we made a diagnosis of EBV-associated post-transplant lymphoproliferative disorder (PTLD). Reduction in the dose of immunosuppressive agents and rituximab led to complete remission of PTLD. PTLD after allogeneic hematopoietic stem cell transplantation (allo-HSCT) is relatively rare, and the development of gastrointestinal perforation after allo-HSCT is very rare.

Tissue-resident mast cells are derived from circulating committed progenitors, which are originated from pluripotential hematopoietic stem cells in bone marrow. These progenitors migrate into extravascular tissues, where they undergo differentiation and maturation into tissue-specific mature phenotypes. When activated by IgE/antigen, stem cell factor, neuropeptides, or other stimuli, mature mast cells release three classes of biologically active products, including pre-formed mediators stored in secretory granules, newly transcribed cytokines and chemokines, and de novo synthesized lipid mediators. Therefore, these cells have been implicated as major effector cells in acute and chronic inflammatory diseases. In recent years, it has become clear that lipid mediators including arachidonic acid metabolites (prostaglandins and leukotrienes) and lysophospholipid-derived products play crucial roles in mast cell-associated pathology. In this article, we will provide an overview of the roles of various lipid mediators in allergic diseases fueled by studies of their biosynthetic enzymes or receptors. In the latter part, we will make a particular focus on phospholipase A(2) enzymes, which are placed at the bottleneck (rate-limiting) step of the lipid mediator-biosynthetic pathways.

Mast cells originate from hematopoietic stem cells and undergo terminal differentiation in the tissues, in which they are ultimately resident. Heterogeneity of tissue mast cells is, therefore, one of the key concepts for a better understanding of immune modulation by mast cells. Since no appropriate culture model has been developed for tissue mature mast cells, it was difficult to investigate the tissue-specific functions of mast cells. We established a novel cutaneous mast cell model by modifying the previously reported co-culture system with fibroblastic cell line. This model shares many characteristics with cutaneous mast cells, such as staining properties, sensitivity to cationic secretagogues, and higher levels of granule histamine and proteases. We extracted the candidate genes that should regulate differentiation and functions of mast cells by analyses of the gene expression profiles during the co-culture period. We further investigated the functions of cluster of differentiation 44 (CD44), which is the primary receptor of hyaluronan in mast cells, since CD44 was up-regulated during the co-culture period. Fluorescence study revealed that mast cells expressing CD44 were bound to the extracellular matrix containing hyaluronan and lack of CD44 impaired proliferation of the co-cultured mast cells. In the CD44(-/-) mice, the number of cutaneous mast cells was significantly decreased. Reconstitution analyses with the mast cell deficient strain revealed that CD44 expressed in mast cells should be required in the proliferation in the cutaneous tissues. In the next phase of mast cell research, it might become increasingly important to focus on the heterogeneity of tissue mast cells.

Primary immunodeficiency diseases (PID) represents a group of inherited diseases where mutations in certain gene lead to certain levels of defects in patient immune systems. Among them, several types of PID, including severe combined immunodeficiecny (SCID), warrented development of new types of curative treatment other than allogeneic hematopoietic stem cell transplantation, eventually culiminating in successful stem cell gene therapy tials such as the cases for adenosine deaminase (ADA)-deficiency SCID patients. In this article, I will summarize the current status of stem cell gene therapy for PID, and discuss the problems such clinical trials have in the present forms of treatment, e.g., possible risks of leukemogenesis due to insertional mutagenesis by the use of therapeutic viral vectors. I also try to discuss the future of this type of experimental medicine aiming for the permanent cure of PID, including the one utilizing innovative technologies such as induced pluripotent stem cells.

To translate research findings into medicine and drug development, we have been performing in vivo research using primary human samples. Development of mouse models with reconstituted human immunity would be critical to overcome technical and ethical constraints associated with in vivo human research. To this end, we have created humanized mice by intravenously injecting purified human hematopoietic stem cells (HSCs) into immune-compromised NOD/SCID/IL2rgKO newborns. This xenogeneic transplantation system allows long-term engraftment and multi-lineage differentiation of human HSCs. The humanized mouse fully reconstituted with human myeloid and lymphoid subsets is expected to serve as an in vivo platform for the investigation of human immune function. In addition to understanding normal human hematopoiesis and immunity, the use of humanized mice is expected to allow investigators to translate their research findings into therapeutic and pharmaceutical development. As a possibility for such translation, we developed an in vivo model of human acute myeloid leukemia (AML), a disease in which the majority of patients succumb to relapse. Using the model, we examined the pathogenesis of AML and tried to clarify the role of AML stem cells in chemotherapy resistance and relapse. Humanized mouse model for both normal and diseased immuno-hematopoietic system is opening a new era in translational medicine.

Microchimeric fetal cells are present in the maternal body over a long period and thought to have the ability to colonize multiple tissues and organs. They are found in a wide range of maternal tissues affected with variety of diseases, thus, there is a possibility that they may contribute tissue repair and regeneration. To assess their possibility of use in regenerative medicine, we investigated whether fetal cells regenerate infracted maternal organs. We crossbred wild female mice with male transgenic mice, expressing enhanced green fluorescent protein (EGFP), and total hysterectomies were performed at the day 6 of pregnancies. On day 60 after the operations, the mice were injected with streptozotocin (STZ) to induce multiple organs injuries. We also created the ischemic organ injury model ; myocardial infarction model and cerebral infarction model. Detection and quantification of fetal cells were then attempted in a variety of maternal organs via a fluorescent microscope and quantitative PCR amplification of the gfp transgene. Fetal cells were detected only in maternal bone marrow before maternal organs injuries were induced, however, they were detected not only in bone marrow but also in the maternal injured organs. Histological analysis showed that differentiated fetal cells were observed and their morphological appearance was indistinguishable from their maternal counterparts. These results indicate that fetal cells sustained their population in the maternal bone marrow, may have contributed to the maternal tissue regeneration.