Eishi Ashihara

Clonally amplified cardiac stem cells are regulated by Sca-1 signaling for efficient cardiovascular regeneration.

Recent studies have shown that cardiac stem cells (CSCs) from the adult mammalian heart can give rise to functional cardiomyocytes; however, the definite surface markers to identify a definitive single entity of CSCs and the molecular mechanisms regulating their growth are so far unknown. Here, we demonstrate a single-cell deposition analysis to isolate individually selected CSCs from adult murine hearts and investigate the signals required for their proliferation and survival. Clonally proliferated CSCs express stem cell antigen-1 (Sca-1) with embryonic stem (ES) cell-like and mesenchymal cell-like characteristics and are associated with telomerase reverse transcriptase (TERT). Using a transgene that expresses a GFP reporter under the control of the TERT promoter, we demonstrated that TERTGFP-positive fractions from the heart were enriched for cells expressing Sca-1. Knockdown of Sca-1 transcripts in CSCs led to retarded ex vivo expansion and apoptosis through Akt inactivation. We also show that ongoing CSC proliferation and survival after direct cell-grafting into ischemic myocardium require Sca-1 to upregulate the secreted paracrine effectors that augment neoangiogenesis and limit cardiac apoptosis. Thus, Sca-1 might be an essential component to promote CSC proliferation and survival to directly facilitate early engraftment, and might indirectly exert the effects on late cardiovascular differentiation after CSC transplantation.

Targeting the Wnt/β-catenin signaling pathway in human cancers

Introduction: The Wnt/β-catenin signaling pathway plays a pivotal role in the regulation of cell growth, cell development and the differentiation of normal stem cells. Constitutive activation of the Wnt/β-catenin signaling pathway is found in many human cancers, and is thus an attractive target for anti-cancer therapy. Specific inhibitors of this pathway have been keenly researched and developed. Areas covered: This review discusses the potential of inhibiting the Wnt/β-catenin signaling pathway, as a therapeutic approach for cancer, along with an overview of the development of specific inhibitors. Expert opinion: Cancer stem cells (CSCs) play a significant role in the development and recurrence of several cancers, and Wnt/β-catenin signaling is important for the proliferation of CSCs. Inhibition of Wnt/β-catenin signaling is therefore a promising treatment approach. Progress has been made in the development of screening methods to identify Wnt/β-catenin signaling inhibitors. Biomarker-based screening is an effective and promising method for the identification of compounds of interest.

Rituximab is effective for steroid-refractory sclerodermatous chronic graft-versus-host disease.

Chronic graft-versus-host disease (GVHD) is the most common late complication following allogeneic stem cell transplantation, occurring in 25–80% of transplant recipients.1 It is becoming a more frequent problem due to the increasing recipient age at transplantation as well as the increasing use of alternative donors, peripheral blood stem cells, and donor lymphocyte infusions. The most widely employed first line therapy for chronic GVHD is a combination of cyclosporine (CSA) and prednisolone, but patients who failed to respond to the initial steroid-based therapy have a poor outcome.1 Therefore, various agents have been investigated as salvage therapy for chronic GVHD, but there is no standard approach that is uniformly accepted.

Myeloid-Derived Suppressor Cells Play Crucial Roles in the Regulation of Mouse Collagen-Induced Arthritis

Myeloid-derived suppressor cells (MDSCs) are of myeloid origin and are able to suppress T cell responses. The role of MDSCs in autoimmune diseases remains controversial, and little is known about the function of MDSCs in autoimmune arthritis. In this study, we clarify that MDSCs play crucial roles in the regulation of proinflammatory immune response in a collagen-induced arthritis (CIA) mouse model. MDSCs accumulated in the spleens of mice with CIA when arthritis severity peaked. These MDSCs inhibited the proliferation of CD4+ T cells and their differentiation into Th17 cells in vitro. Moreover, MDSCs inhibited the production of IFN-γ, IL-2, TNF-α, and IL-6 by CD4+ T cells in vitro, whereas they promoted the production of IL-10. Adoptive transfer of MDSCs reduced the severity of CIA in vivo, which was accompanied by a decrease in the number of CD4+ T cells and Th17 cells in the draining lymph nodes. However, depletion of MDSCs abrogated the spontaneous improvement of CIA. In conclusion, MDSCs in CIA suppress the progression of CIA by inhibiting the proinflammatory immune response of CD4+ T cells. These observations suggest that MDSCs play crucial roles in the regulation of autoimmune arthritis, which could be exploited in new cell-based therapies for human rheumatoid arthritis.

ABT-737 is a useful component of combinatory chemotherapies for chronic myeloid leukaemias with diverse drug-resistance mechanisms

The effect of ABT‐737, a BH3‐mimicking inhibitor for anti‐apoptotic Bcl‐2 and Bcl‐XL, but not Mcl‐1, against Bcr‐Abl‐positive (Bcr‐Abl+) leukaemic cells was examined. ABT‐737 potently induced apoptosis in Bcr‐Abl+ chronic myeloid leukaemia (CML) cell lines and primary CML samples in vitro and prolonged the survival of mice xenografted with BV173 cells, a CML cell line. Higher expression of anti‐apoptotic Bcl‐2 proteins reduced cell killing by ABT‐737 in each cell line, but there was no correlation between the sensitivities to ABT‐737 and the specific expression patterns of Bcl‐2 family proteins among cell lines. Thus, the cell killing effect of ABT‐737 must be determined not only by the expression patterns of Bcl‐2 family proteins but also by other mechanisms, such as high expression of Bcr‐Abl, or a drug‐efflux pump, in CML cells. ABT‐737 augmented the cell killing effect of imatinib in Bcr‐Abl+ cells with diverse drug‐resistance mechanisms unless leukaemic cells harboured imatinib‐insensitive Abl kinase domain mutations, such as T315I. The combination of homoharringtonine that reduces Mcl‐1 enhanced the killing by ABT‐737 strongly in Bcr‐Abl+ cells even with T315I mutation. These results suggest that ABT‐737 is a useful component of chemotherapies for CML with diverse drug‐resistance mechanisms.

B‐cell lymphoma associated with haemophagocytic syndrome: a clinical, immunological and cytogenetic study

B‐cell lymphoma associated with haemophagocytic syndrome (HPS) is extremely rare in Western countries but has recently been increasingly reported in Asian countries. We describe seven patients with B‐cell lymphoma associated with HPS, six males and one female, age range 41–82 years (median 63 years). All patients had fever and splenomegaly, and six of the seven patients had hepatomegaly with no associated lymphadenopathy. The bone marrow showed haemophagocytosis and an infiltration of lymphoma cells. All patients showed increased levels of lactate dehydrogenase, C‐reactive protein, ferritin and soluble interleukin‐2 receptor. Lymphoma cells were positive for CD19, CD20 and surface immunoglobulin in all patients examined, and positive for CD5 in four of seven patients. Cytogenetic analyses of bone marrow cells showed a complex structural abnormality including chromosome 14q32 in two patients, 19q13 in three patients and deletion of the terminal part of 8p21 in six patients. The prognosis was poor; only two of the seven patients have survived in complete remission with a median survival of 11 months. These data suggested that B‐cell lymphoma associated with HPS might constitute a distinct biological and clinical disease entity. Abnormality of chromosome 19q13 and loss of 8p21 might be involved in the pathogenesis of this disease.

Significance of C4d staining in ABO-identical/ compatible liver transplantation

Complement degradation product C4d has become an important marker of humoral or antibody-mediated rejection in renal and heart allograft biopsies. Although there have been several reports on the detection of C4d in liver allografts, the significance of C4d in liver transplantation and its relationship with humoral rejection are still not clear. We investigated the frequency and pattern of C4d staining in liver allograft biopsies with reference to preoperative lymphocyte crossmatch tests, which detect donor-reactive lymphocyte antibody. Survival rates at 5 years were 77% for crossmatch-negative patients and 53% for crossmatch-positive patients (P=0.009). In crossmatch-negative patients, reproducible positive staining was obtained in 28 of 86 (33%) biopsies taken within 90 days after transplantation and 33 of 96 (34%) biopsies 90 days or after transplantation. Most C4d staining was observed in the portal areas, and no clear correlation was observed between C4d positivity and histological diagnosis. In crossmatch-positive patients, 9 of 11 (82%) biopsies showed positivity for C4d. C4d stained perivenular areas as well as portal areas. Histology of crossmatch-positive patients included acute rejection and cholangitis, but did not include periportal changes that were seen in humoral rejection in ABO-incompatible liver transplantation. In summary, focal C4d deposition was seen in various types of liver allograft injury and had little clinical impact on crossmatch-negative patients, but extensive C4d staining in crossmatch-positive patients may be associated with humoral rejection and poor graft survival.

Zoledronic acid - a multiplicity of anti-cancer action.

Bisphosphonates (BPs) are inhibitors of bone-resorption and have become the current standard of care for preventing skeletal complications associated with bone metastases. Among BPs, zoledronic acid (ZOL) has the strongest activity of anti-bone resorption and shows diverse direct anti-cancer effects in vitro. Some chemical and biological characteristics of ZOL indicate the potential for in vivo growth inhibition and the mechanisms responsible for the observed anti-cancer effects are beginning to be elucidated. ZOL inhibits farnesyl pyrophosphate synthase, a key enzyme in the mevalonate pathway. Consequently, it inhibits the prenylation of small G-proteins such as Ras, Rap1, Rho and Rab, reduces the signals they mediate, and thereby prevents the growth, adhesion/spreading, and invasion of cancer cells. ZOL, which has a high affinity for mineralized bone, rapidly localizes to bone, resulting in therapeutically effective local concentrations for the cancer cells in bone. ZOL also blocks osteolysis and osteoclastgenesis, thus preventing the release of various growth factors which are abundantly stored in bone. Moreover, ZOL stimulates gammadelta T cells, which play important roles in innate immunity against cancer. In addition, ZOL is also a potent inhibitor of angiogenesis, probably due to the modification of various angiogenic properties of endothelial cells. Furthermore, ZOL synergizes with a variety of anticancer agents including chemotherapeutic drugs, molecular targeted agents, and other biological agents. Based on these potential anti-cancer properties, several clinical trials have been initiated to test the combination of ZOL and other agents. The accumulated encouraging evidence to date indicate that ZOL is an attractive anti-cancer agent which promises to be the next exciting therapy for patients with various cancers.

Comparison of imatinib, dasatinib, nilotinib and INNO-406 in imatinib-resistant cell lines

We compared the growth-inhibitory effects and inhibition profile of the SRC family kinases (SFKs) of imatinib, dasatinib, nilotinib and INNO-406. Dasatinib exhibited the strongest potency against BCR-ABL with little selectivity over SFKs. Nilotinib exhibited a weaker affinity than the other inhibitors, but was highly specific for ABL and may be useful for the treatment of P-glycoprotein overexpressing leukemic cells. INNO-406 had an intermediate affinity for BCR-ABL between that of dasatinib and nilotinib, and inhibited only SFKs LCK and LYN among SFKs. Both nilotinib and INNO-406 were potent inhibitors of the dasatinib-resistant T315A, F317L and F317V BCR-ABL mutations.

Galectin-3 (Gal-3) induced by leukemia microenvironment promotes drug resistance and bone marrow lodgment in chronic myelogenous leukemia

Bone marrow (BM) microenvironment (BMME) constitutes the sanctuary for leukemic cells. In this study, we investigated the molecular mechanisms for BMME-mediated drug resistance and BM lodgment in chronic myelogenous leukemia (CML). Gene-expression profile as well as signal pathway and protein analyses revealed that galectin-3 (Gal-3), a member of the β-gal–binding galectin family of proteins, was specifically induced by coculture with HS-5 cells, a BM stroma cell-derived cell line, in all five CML cell lines examined. It was also found that primary CML cells expressed high levels of Gal-3 in BM. Enforced expression of Gal-3 activated Akt and Erk, induced accumulation of Mcl-1, and promoted in vitro cell proliferation, multidrug resistance to tyrosine kinase inhibitors for Bcr-Abl and genotoxic agents as a result of impaired apoptosis induction, and chemotactic cell migration to HS-5–derived soluble factors in CML cell lines independently of Bcr-Abl tyrosine kinase. The conditioned medium from Gal-3–overexpressing CML cells promoted in vitro cell proliferation of CML cells and HS-5 cells more than did the conditioned medium from parental cells. Moreover, the in vivo study in a mice transplantation model showed that Gal-3 overexpression promoted the long-term BM lodgment of CML cells. These results demonstrate that leukemia microenvironment-specific Gal-3 expression supports molecular signaling pathways for disease maintenance in BM and resistance to therapy in CML. They also suggest that Gal-3 may be a candidate therapeutic target to help overcome BMME-mediated therapeutic resistance.