Yutaka Shimada

Bio: Yutaka Shimada is an academic researcher from University of Toyama. The author has contributed to research in topics: Cancer & Esophageal cancer. The author has an hindex of 58, co-authored 441 publications receiving 14980 citations. Previous affiliations of Yutaka Shimada include Kyoto University & Niigata University.

Widespread requirement for Hedgehog ligand stimulation in growth of digestive tract tumours

Abstract: Activation of the Hedgehog (Hh) signalling pathway by sporadic mutations or in familial conditions such as Gorlin's syndrome is associated with tumorigenesis in skin, the cerebellum and skeletal muscle. Here we show that a wide range of digestive tract tumours, including most of those originating in the oesophagus, stomach, biliary tract and pancreas, but not in the colon, display increased Hh pathway activity, which is suppressible by cyclopamine, a Hh pathway antagonist. Cyclopamine also suppresses cell growth in vitro and causes durable regression of xenograft tumours in vivo. Unlike in Gorlin's syndrome tumours, pathway activity and cell growth in these digestive tract tumours are driven by endogenous expression of Hh ligands, as indicated by the presence of Sonic hedgehog and Indian hedgehog transcripts, by the pathway- and growth-inhibitory activity of a Hh-neutralizing antibody, and by the dramatic growth-stimulatory activity of exogenously added Hh ligand. Our results identify a group of common lethal malignancies in which Hh pathway activity, essential for tumour growth, is activated not by mutation but by ligand expression.

Identification of Gastric Cancer Stem Cells Using the Cell Surface Marker CD44

Abstract: Cancer stem cells (CSCs) have been defined as a unique subpopulation in tumors that possess the ability to initiate tumor growth and sustain tumor self-renewal. Although the evidence has been provided to support the existence of CSCs in various solid tumors, the identity of gastric CSCs has not been reported. In this study, we have identified gastric cancer-initiating cells from a panel of human gastric cancer cell lines using cell surface marker CD44. Among six gastric cancer cell lines, three lines MKN-45, MKN-74, and NCI-N87 had a sizeable subpopulation of CD44(+) cells, and these cells showed spheroid colony formation in serum-free media in vitro as well as tumorigenic ability when injected into stomach and skin of severe combined immunodeficient (SCID) mice in vivo. The CD44(+) gastric cancer cells showed the stem cell properties of self-renewal and the ability to form differentiated progeny and gave rise to CD44(−) cells. CD44 knockdown by short hairpin RNA resulted in much reduced spheroid colony formation and smaller tumor production in SCID mice, and the CD44(−) populations had significantly reduced tumorigenic ability in vitro and in vivo. Other potential CSC markers, such as CD24, CD133, CD166, stage-specific embryonic antigen-1 (SSEA-1), and SSEA-4, or sorting for side population did not show any correlation with tumorigenicity in vitro or in vivo. The CD44(+) gastric cancer cells showed increased resistance for chemotherapy- or radiation-induced cell death. These results support the existence of gastric CSCs and may provide novel approaches to the diagnosis and treatment of gastric cancer.

Constitutive activation of the 41-/43-kDa mitogen-activated protein kinase signaling pathway in human tumors

Abstract: The 41-kDa and 43-kDa mitogen-activated protein (MAP) kinases play a pivotal role in the mitogenic signal transduction pathway and are essential components of the MAP kinase cascade, which includes MAP kinase kinase (MEK) and Raf-1. As aberrant activation of signal transducing molecules such as Ras and Raf-1 has been linked with cancer, we examined whether constitutive activation of the 41-/43-kDa MAP kinases is associated with the neoplastic phenotype of 138 tumor cell lines and 102 primary tumors derived from various human organs. Constitutive activation of the MAP kinases was observed in 50 tumor cell lines (36.2%) in a rather tissue-specific manner: cell lines derived from pancreas, colon, lung, ovary and kidney showed especially high frequencies with a high degree of MAP kinase activation, while those derived from brain, esophagus, stomach, liver and of hematopoietic origin showed low frequencies with a limited degree of MAP kinase activation. We also detected constitutive activation of the 41-/43-kDa MAP kinases in a relatively large number of primary human tumors derived from kidney, colon and lung tissues but not from liver tissue. Many tumor cells, in which point mutations of ras genes were detected, showed constitutive activation of MAP kinases, however, there were also many exceptions to this observation. In contrast, the activation of the 41-/43-kDa MAP kinases was accompanied by the activation of Raf-1 in the majority of tumor cells and was completely associated with the activation of MEK and p90rsk in all the tumor cells examined. These results suggest that the constitutive activation of 41-/43-kDa MAP kinases in tumor cells is not due to the disorder of MAP kinases themselves, but is due to the disorder of Raf-1, Ras, or some other signaling molecules upstream of Ras.

Surgery plus chemotherapy compared with surgery alone for localized squamous cell carcinoma of the thoracic esophagus: a Japan Clinical Oncology Group Study--JCOG9204.

Abstract: Purpose: We performed a multicenter randomized controlled trial to determine whether postoperative adjuvant chemotherapy improves outcome in patients with esophageal squamous cell carcinoma undergoing radical surgery. Patients and Methods: Patients undergoing transthoracic esophagectomy with lymphadenectomy between July 1992 and January 1997 at 17 institutions were randomly assigned to receive surgery alone or surgery plus chemotherapy including two courses of cisplatin (80 mg/m2 of body-surface area × 1 day) and fluorouracil (800 mg/m2 × 5 days) within 2 months after surgery. Adaptive stratification factors were institution and lymph node status (pN0 versus pN1). The primary end point was disease-free survival. Results: Of the 242 patients, 122 were assigned to surgery alone, and 120 to surgery plus chemotherapy. In the surgery plus chemotherapy group, 91 patients (75%) received both full courses of chemotherapy; grade 3 or 4 hematologic or nonhematologic toxicities were limited. The 5-year disease-free ...

Characterization of 21 newly established esophageal cancer cell lines

Abstract: Twenty-one esophageal cancer cell lines (KYSE series) have been established from the resected specimens of patients with esophageal cancer. Three lines, KYSE-30, KYSE-50, and KYSE-70, were derived from the implanted tumor of nude mice (initial passage); others were derived from resected specimens. Each cell line was morphologically distinct. Detailed cytogenetic analysis indicated that each cell line was karyotypically unique, and DNA fingerprint analysis showed no cross-contamination among cells. Doubling time ranged from 13.7 to 75.5 hours, and modal chromosome numbers ranged from 46 to 120. Most cell lines grew in monolayer, but two cell lines (KYSE-50 and KYSE-360) grew as floating cell aggregates. No correlation was demonstrated between the establishment of cell lines and cell differentiation. These cell lines are the first reported to be homogeneous and individually unique and may provide a useful model for the study of human esophageal cancer.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Therapeutic potential of resveratrol: the in vivo evidence.

Abstract: Resveratrol, a constituent of red wine, has long been suspected to have cardioprotective effects. Interest in this compound has been renewed in recent years, first from its identification as a chemopreventive agent for skin cancer, and subsequently from reports that it activates sirtuin deacetylases and extends the lifespans of lower organisms. Despite scepticism concerning its bioavailability, a growing body of in vivo evidence indicates that resveratrol has protective effects in rodent models of stress and disease. Here, we provide a comprehensive and critical review of the in vivo data on resveratrol, and consider its potential as a therapeutic for humans.

Tumour stem cells and drug resistance

Abstract: The contribution of tumorigenic stem cells to haematopoietic cancers has been established for some time, and cells possessing stem-cell properties have been described in several solid tumours. Although chemotherapy kills most cells in a tumour, it is believed to leave tumour stem cells behind, which might be an important mechanism of resistance. For example, the ATP-binding cassette (ABC) drug transporters have been shown to protect cancer stem cells from chemotherapeutic agents. Gaining a better insight into the mechanisms of stem-cell resistance to chemotherapy might therefore lead to new therapeutic targets and better anticancer strategies.

Vascular endothelial growth factor: basic science and clinical progress.

Abstract: Vascular endothelial growth factor (VEGF) is an endothelial cell-specific mitogen in vitro and an angiogenic inducer in a variety of in vivo models. Hypoxia has been shown to be a major inducer of VEGF gene transcription. The tyrosine kinases Flt-1 (VEGFR-1) and Flk-1/KDR (VEGFR-2) are high-affinity VEGF receptors. The role of VEGF in developmental angiogenesis is emphasized by the finding that loss of a single VEGF allele results in defective vascularization and early embryonic lethality. VEGF is critical also for reproductive and bone angiogenesis. Substantial evidence also implicates VEGF as a mediator of pathological angiogenesis. In situ hybridization studies demonstrate expression of VEGF mRNA in the majority of human tumors. Anti-VEGF monoclonal antibodies and other VEGF inhibitors block the growth of several tumor cell lines in nude mice. Clinical trials with various VEGF inhibitors in a variety of malignancies are ongoing. Very recently, an anti-VEGF monoclonal antibody (bevacizumab; Avastin) has been approved by the Food and Drug Administration as a first-line treatment for metastatic colorectal cancer in combination with chemotherapy. Furthermore, VEGF is implicated in intraocular neovascularization associated with diabetic retinopathy and age-related macular degeneration.