Proliferation of cancer cells requires activation of signals that response to nutrients. One of the major coordinators of nutrient signals is mammalian/mechanistic target of rapamycin (mTOR). mTOR complex 1 (mTORC1) controls multiple cellular processes, including protein synthesis, glucose metabolism, fatty acid and sterol synthesis, mitochondrial biogenesis, and autophagy. Although inhibitors of mTORC1 have been developed, effectiveness of the inhibitors for cancer eradication appears to be limited, because of presence of several feed-back signals. In addition, leukemia stem cells might survive against mTOR inactivation through common mechanisms by which normal hematopoietic stem cells are maintained in the niche. Advances in understanding of how mTOR signaling is involved in mechanisms of stem cells may lead to novel therapeutic approaches that can successfully eradicate cancer.

Embryonic stem (ES) and induced pluripotent stem (iPS) cells are pluripotent and can give rise to all cell types. ES/iPS cells have a unique transcriptional circuit that sustains the pluripotent state. These cells also possess a characteristically high rate of proliferation as well as an abbreviated G1 phase. These unique molecular properties distinguish ES and iPS cells from somatic cells. Mouse ES/iPS cells are in a high-flux metabolic state, with a high dependence on threonine catabolism. However, little is known about amino acid metabolism in human ES/iPS cells. Recently, we reported that human ES/iPS cells require high amounts of methionine (Met) and express high levels of Met metabolism enzymes (Shriaki N, et al: Cell Metabolism, 2014). Met deprivation results in a rapid decrease in intracellular S-adenosyl-methionine (SAM), triggering the activation of p53 signaling, reducing pluripotent marker gene NANOG expression, and poising human ES/iPS cells for differentiation, follow by potentiated differentiation into all three germ layers. However, when exposed to prolonged Met deprivation, the cells went to apoptosis. In this review, we explain the importance of SAM in Met metabolism and its relationship with pluripotency, cell survival, and differentiation of human ES/iPS cells.

Immunodeficient mice are widely used to reconstitute human hematopoiesis by xenotransplantation of hematopoietic stem cells(HSCs). This humanized mouse model provides a powerful tool to evaluate biological properties of human HSCs in vivo. This systems have been used also to study human cancer stem cells. Currently, NOD -background immunodeficient strains are the most efficient to reconstitute human hematopoiesis in the mice, but even they are not enough for cancer stem cell assay. NOD strain has multiple immune deficiencies. For this reason, to improve and establish a new xenotransplantation model, lymphoid-depleted strains have been backcrossed into the NOD-inbred strain to introduce such numerous NOD-specific abnormalities. Our positional genetic study has located the NOD-specific polymorphic Sirpa as a molecular responsible for its high xenograft efficiency. We established B6-based immunodeficient strains harboring NOD-Sirpa (BRGS) which showed efficient human cell engraftment comparable to that of NOD -background strains. Consequently, BRGS mice are free from NOD-related abnormalities. This simplified strain should be useful in future xenotransplant study of cancer stem cells.

Cancer is generally developed through accumulation of multiple genetic mutations. Epigenetic abnormalities of DNA methylation and histone modification patterns were also found in most cancer cells. Although induced pluripotent stem cells (iPSCs) can be generated through epigenetic reorganization without affecting the underlying genomic sequencing, they have some shared characteristics with cancer cells, which include unlimited growth potential. Taking advantages of such properties of iPSC derivation, the reprogramming technology is applicable not only for regenerative medicine but also for cancer research. Here, we introduce the potential application of iPSC technology for better understandings of cancer biology. Especially, we would like to propose the role of cellular identity in cancer development.

Cancer stem cells are known to influence survival, chemoresistance, relapse and metastasis. Pyruvate kinase M2 (PKM2) maintains aerobic glycolysis in cancer cells and stimulates cell proliferation by controlling Warburg effect. In addition, PKM2 translocates to nucleus and up-regulates PDK1 expression by controlling its transcription. PKM2 confers malignant potential by controlling both metabolism and transcriptional regulation. Tumor invasion is initiated with the change of epithelial-mesenchymal transition (EMT) in cancer cell. After EMT induction, in parallel with E-cadherin down-regulation and vimentin up-regulation, the expression of PKM2 was increased both in transcriptional and translational level and PKM2 translocated into nucleus. TGIF2 was identified which interacted with PKM2 in nucleus in response to EMT induction, which was considered to have a key role in controlling EMT induction. We performed immunohistochemical staining with specific antibody to PKM2 using clinical samples of colorectal cancers. Clinicopathological analysis showed that PKM2 positivity significantly correlated with lymph node metastasis and distant organ metastasis. In conclusion, our data suggested that PKM2 nuclear function had a crucial role in controlling invasion and metastasis.

The fate of stem cells is tightly controlled by specialized microenvironments (niches). Cell cycle quiescence is a key behavior of stem cells, which protects them from being exhausted by exogenous insults. Since the discovery of cancer stem cells, which are quiescent and thus resistant to anti-cancer therapy, there has been considerable interest regarding whether or not there are distinct niches for quiescent and expanding cancer cells, respectively. In our recent study using whole-mount immunofluorescence imaging techniques, we found that arteriolar niches promote hematopoietic stem cell (HSC) dormancy and that the NG2+ peri-arteriolar niche cells themselves are quiescent, suggesting that bone marrow arterioles comprise a specialized microenvironment that promotes quiescence of both HSCs and niche cells. In this review, we will argue about the advance of our knowledge on normal stem cell niches and the roles of microenvironments in cancer.

Technological advances such as the high-throughput sequencing are providing us novel aspects and perspectives of cancer stem cells (CSCs). Current evidences support a model where multiple subclones persist, rather than a simple hierarchical model with CSCs. The presence of multiple subclones contributes to increase in fitness and robustness of a cancer, which is reminiscent of the stability in ecosystems. The latest report describing the sequencing of peripheral-blood cells from unselected persons revealed that clonal hematopoiesis with somatic mutations already exists in a fair percentage of elderly persons. The analysis also shed light on some epigenetic modifiers as the driver genes of clonal hematopoiesis. In this article, we review the recent evolution of CSC model in hematology.

The capacity of cancer stem cells, or cancer-initiating cells, to both provide mature tumor cells and perpetuate themselves through self-renewal is crucial to initiate and maintain tumorigenesis, and has become the focus of intense research interest as a promising source of new therapeutic strategies. However, many scientific challenges and technical barriers remain to be solved before recent findings can be translated into effective therapeutics. Here we highlight the latest advances in our knowledge of cancer stem cells, and provide a critical perspective on the clinical benefits promised by this developing area of research.

Stem cell is defined as the cell having the ability of self-renew and differentiation. Due to the development of flow cytometric analysis and immunodeficient mouse model, stem cell research had dramatically progressed. Based on the knowledge of normal stem cell, concept of cancer stem cell, which have self-renewal ability and tumorigenic potential in immunodeficient mouse, have been established. Cancer stem cell population in various cancers has been identified using cell surface markers, such as CD44, and therapeutic strategies have been developing. Moreover, as accumulating the knowledge of cancer stem cell, it has revealed that cancer stem cell has high plasticity. We introduce here the evolving cancer stem cell concept.

A 14-year-old male with multiple myeloma (IgG-λ, ISS stage 3) received myeloablative matched unrelated bone marrow transplantation, and achieved a complete response. At 16 months after the transplantation, he relapsed. The relapse was resistant to bortezomib and thalidomide. Peripheral blood showed mixed chimerism with 10% recipient cells. Peripheral blood stem cells (PBSC) were collected and pseudo-autologous PBSC transplantation (PASCT) was performed following high-dose melphalan without graft-versus-host disease prophylaxis. Hematopoietic recovery was prompt and a partial response was obtained without graft-versus-host disease exacerbation. We have presented a rare case of adolescent-onset multiple myeloma, obtaining a transient response with PASCT following post-allogeneic transplant relapse.

Myelodysplastic syndrome (MDS) is known to often be complicated by a range of autoimmune diseases. We herein present a case with MDS complicated by cold autoimmune hemolytic anemia (cold AIHA). The patient was a 51-year-old woman. She was diagnosed with MDS (refractory cytopenia with multilineage dysplasia) in May 2009. In January 2010, she underwent unrelated allogeneic bone marrow transplantation but was re-admitted in October 2010 for treatment of relapsed MDS. Despite daily transfusions of red blood cells, her anemia failed to improve. Her laboratory examinations showed a low haptoglobin level and elevation of indirect bilirubin and LDH. The direct Coombs test was positive at a low and at room temperature and cold agglutinin was negative. After confirming the diagnosis of cold AIHA, all transfusion fluids were warmed but her anemia still failed to improve. In addition to the warmed transfusion fluids, we administered corticosteroids, immunosuppressive agents and high-dose intravenous immunoglobulin infusions. This management strategy ameliorated the patient's hemolytic anemia. To our knowledge, MDS cases complicated by cold AIHA are rare. Our patient thus provides a valuable contribution to medical knowledge.

Acute myeloid leukemia (AML) is a hematologic malignancy which originates from leukemia initiating cells (LICs). Since LICs are considered to be resistant to standard chemotherapy, the identification of common mechanisms involved in LIC maintenance and progression is crucial to establishing broadly effective therapeutic agents for AML. The NF-κB pathway is one of the most promising targets, considering that its constitutive activation has been reported in different types of AML. In myeloid leukemia mouse models, we found that NF-κB activity is maintained specifically in LICs through autocrine TNF-α secretion, forming an NF-κB/TNF-α positive feedback loop. LICs had increased levels of active proteasome machinery, which promoted the degradation of IκBα and further supported NF-κB activity. Genetic ablation of TNF-α or NF-κB markedly suppressed leukemia progression in vivo. These findings demonstrate that NF-κB/TNF-α signaling in LICs contributes to leukemia progression and provide a widely applicable approach for targeting LICs.

Acute myeloid leukemia (AML) with high ecotropic viral integration site-1 (EVI1) expression (EVI1high AML) is classified as a refractory leukemia with a poor prognosis. We identified G protein-coupled receptor 56 (GPR56) as a novel marker for EVI1high AML, which is an orphan adhesion G protein-coupled receptor (GPCR). GPR56 was found to be associated with high cell adhesion and anti-apoptotic activities in EVI1high AML through activation of RhoA signaling. Moreover, in Gpr56-/- mice, the number of hematopoietic stem cells (HSCs) in bone marrow was significantly decreased with proportional increases in the spleen and peripheral blood, reflecting extramedullary hematopoiesis. The number of Gpr56-/- HSC progenitor cells in the G0 phase was significantly reduced with impaired adhesion and the loss of GPR56 function, which diminished the in vivo repopulating ability of HSCs. In conclusion, GPR56 may represent an important GPCR for the maintenance of quiescence and cellular adhesion of EVI1high AML and HSCs in the bone marrow niche. Moreover, given that GPR56 expression in leukemia stem cells is much higher than that in HSCs, GPR56 is a candidate therapeutic target for leukemia stem cells in EVI1high AML.

Constitutive activation of mTOR is associated with acceleration of leukemia development. However, mTORC1 functions in established leukemia are unclear. We evaluated the role of mTORC1 in mouse acute myeloid leukemia (AML) cells using a murine model of conditional deletion of Raptor, an essential component of mTORC1, and an MLL-AF9-driven leukemia model. mTORC1 is essential for leukemia initiation, but a subset of AML cells with undifferentiated phenotypes survived long-term in the absence of mTORC1 activity. Our study demonstrated AML cells lacking mTORC1 activity to be capable of self-renewal as AML stem cells. This review will summarize our study on the roles of mTORC1 in AML, and discuss potential benefits and risks of mTORC2 inhibition and the potential use of mTOR inhibitors as AML therapy.

A 51-year-old man was admitted to our hospital complaining of right upper quadrant abdominal and back pain. Severe hepatomegaly (six fingerbreadths) was detected by liver palpation. Blood test results showed cholestatic liver disease. He was diagnosed with amyloidosis by liver biopsy. Bone marrow aspiration revealed 15% of contents to be plasma cells. BJPκ was detected by urine electrophoresis. Therefore, he was diagnosed with the BJPκ type of multiple myeloma with systemic amyloidosis. The patient was treated with bortezomib, dexamethasone and high-dose melphalan with autologous peripheral blood stem cell transplantation. He achieved VGPR (very good partial response) after transplantation. Hepatomegaly improved but swelling persisted, and he was therefore treated with 1.3 mg/m(2)/day of bortezomib and 20 mg/day of dexamethasone on day 1 and day 15 in 28-day cycles. Upon finishing 22 cycles in June 2014, his liver had returned to normal size. Restoration of normal liver size after treatment is rare in cases with severe hepatomegaly due to systemic amyloidosis. We thus report our case with a review of the relevant literature.

Chronic lymphocytic leukemia (CLL) is a mature lymphoid malignancy that has a variable clinical course. Recent genomic studies using next-generation sequencers have revealed recurrent genetic alterations implicated in CLL pathogenesis. Clonal evolution by stepwise acquisition of genetic mutations may result in CLL progression. Among these abnormalities, alteration of B cell receptor (BCR) signaling is critical during CLL development. In addition, signals from the microenvironment support the proliferation and survival of CLL cells. Novel molecular targeted drugs that influence these signals are now becoming clinically available.

In a preceding paper, we showed that aroma candy containing oligonol, capric acid, and cinnamon (cassia) powder had potent inhibitory activity against mycelial growth of Candida albicans in vitro and protective activity against murine oral candidiasis. In order to assess the effects of this candy (the test candy) on oral C. albicans colony-forming units (CFU) and oral hygiene states, a placebo-controlled double-blind crossover comparative study was performed. Twenty subjects were divided into two groups. One group ingested the test candy in the first 7 days followed by 2 weeks washing-off period, then ingested the placebo candy (control candy) for 7 days. The other group was vice versa. C. albicans CFU in all oral rinse samples from the subjects before and after 7 days ingestion of candy was measured. The degree of oral malodor in all subjects was monitored using a portable measuring instrument. The results showed no statistically significant difference between test-candy group and placebo group for C. albicans CFU. However, C. albicans CFU in test-candy group with>4,000 CFUs was significantly decreased after 7 days ingestion of test-candy (p<0.05). Scores of oral malodor in the test-candy group was significantly decreased after 7 days ingestion of test-candy (p<0.05). A questionnaire survey of oral hygiene states indicated that in the test-candy group, oral malodor, glutinous feeling, and refreshing feeling significantly improved in comparison with control-candy group (p<0.05). Our study suggests that the aroma candy is effective in oral health care of elderly carrying C. albicans.

I. A new therapeutic target for diabetic retinopathy. Recent reports state that succinate may be an independent retinal angiogenic factor. We evaluated concentrations in vitreous from proliferative diabetic retinopathy (PDR), and found that succinate increased significantly in PDR. Interestingly, levels of succinate from bevacizumab-pre-injected PDR were normal, suggesting that vascular endothelial growth factor (VEGF) had a positive feedback mechanism for succinate since succinate was previously reported to induce VEGF. II. A new understanding of central retinal vein occlusion (CRVO). We evaluated retinal blood flow velocity with laser speckle flowgraphy (LSFG) made in Japan, and found that cases in which both macular edema and retinal blood flow velocity improved after anti-VEGF therapy had better prognosis. In ischemic CRVO at final visit, mean retinal blood velocity was less than 50% of fellow eyes after 1st anti-VEGF therapy, suggesting that those cases might have poor prognosis. LSFG is useful for evaluation and decision in CRVO treatment. III. From exploration for mechanism in retinal vascular diseases to re-vascularization therapy. The standard treatment for retinal non-perfusion area is scatter laser photocoagulation, which is both invasive of the peripheral retina and may prove destructive. Re-vascularization is an ideal strategy for treatment of retinal non-perfusion area. To develop a new methods for re-vascularization in retinal non-perfusion area, we have designed experiments using a retina without vasculature differentiated from induced pluripotent stem(iPS) cells.