Mitsunobu Sato

Bio: Mitsunobu Sato is an academic researcher from University of Tokushima. The author has contributed to research in topics: Salivary gland & Cell culture. The author has an hindex of 24, co-authored 138 publications receiving 1945 citations.

Epithelial-mesenchymal transition induced by the stromal cell-derived factor-1/CXCR4 system in oral squamous cell carcinoma cells

Abstract: Epithelial-mesenchymal transition (EMT) refers to critical events occasionally observed during tumor progression, including invasion and metastasis, by which cancer cells acquire a fibroblast-like phenotype. Since the stromal cell-derived factor-1 (SDF-1)/CXCR4 system can facilitate lymph node metastasis in oral squamous cell carcinoma (SCC), we have explored the possibility that this system might be involved in EMT. Oral SCC cells, B88 and HNt, which have functional CXCR4 and lymph node metastatic potential, were found to lose their epithelial cell morphology due to SDF-1. In this context, the downregulation of epithelial markers, cytokeratin, E-cadherin and beta-catenin, and the upregulation of mesenchymal marker, vimentin and snail were detected. Furthermore, upregulation of vimentin by treatment with SDF-1 was impaired by phosphatidylinositol 3 kinase (PI3K) inhibitor Wortmannin, but not by mitogen-activated protein kinase/extracellular signal-regulated kinase inhibitor U0126. In the type I collagen embedding culture, SDF-1-treated B88 cells formed protruding extensions, but the effect was impaired by treatment with Wortmannin. These results suggested that EMT induced by the SDF-1/CXCR4 system might be involved in the lymph node metastasis of oral SCCs via activation of PI3K-Akt/PKB pathway.

Search for specific markers of neoplastic epithelial duct and myoepithelial cell lines established from human salivary gland and characterization of their growth in vitro

Abstract: The neoplastic epithelial duct cells human salivary gland (HSG) and myoepithelial cells human pleomorphic adenoma (HPA) established from human salivary gland were examined by the immunoperoxidase method for the presence of specific antigens such as carcinoembryonic antigen (CEA), S-100 protein, secretory component (SC), lactoferrin (LF), and myosin. Isolation of the cells and their morphologic features were reported previously. Consequently, the presence of CEA, SC, and LF in the HSG cells was demonstrated. The HPA cells were identified to express the specific antigens reactive to anti-S-100 protein, anti-myosin and anti-CEA sera in addition to the presence of oxytocin receptor. When the two cell lines were co-cultured in monolayer culture or within the sponge matrix, a large number of ductlike or tubular structures were formed in an optimal ratio of 1:2 in HSG and HPA cells, whereas the cultures of HSG cells only grew with occasional formation of ductlike structure. In addition, in HSG and HPA cells in an area with their contact in the mixed cultures, CEA staining was intensified as compared with the culture of HSG or HPA cells only and further S-100 protein was detected in HSG cells, whereas S-100 protein was not detected in the culture of HSG cells only. These findings strongly suggest that the intercalated duct and myoepithelial cells from human salivary gland propagate with their interaction together in the expression of specific antigens such as CEA and S-100 protein or in the morphogenesis of salivary gland epithelial cells.

Down-regulation of TSC-22 (Transforming Growth Factor β-stimulated Clone 22) Markedly Enhances the Growth of a Human Salivary Gland Cancer Cell Line in Vitro and in Vivo

Abstract: We have recently isolated TSC-22 ( transforming growth factor β-stimulated clone 22 ) cDNA as a new anticancer drug (Vesnarinone)-inducible gene in a human salivary gland cancer cell line, TYS. We conducted the present study to examine whether up-regulation or down-regulation of TSC-22 can affect the growth of TYS cells in vitro and in vivo . We constructed an expression vector containing sense- or antisense-oriented human TSC-22 cDNA under the transcriptional control of the SRα promoter. We cotransfected TYS cells with the sense or antisense expression vector and pSV2neo and obtained more than 200 G418-resistant colonies in each sense or antisense transfectant. Approximately 80% of representative G418-resistant clones expressed the transcripts from transfected sense or antisense TSC-22 cDNA. To avoid the clonal heterogeneity of the cells, we mixed all of the G418-resistant colonies together in each sense or antisense transfectant and examined the expression of TSC-22 protein, in vitro growth, and the tumorigenicity in nude mice. The expression of TSC-22 protein was examined by solid-phase ELISA using a specific antibody against recombinant TSC-22 protein. The expression of TSC-22 protein was up-regulated in the sense transfectants and down-regulated in the antisense transfectants. Contrary to our expectation, up-regulation of TSC-22 protein did not affect both in vitro and in vivo growth of TYS cells. However, down-regulation of TSC-22 markedly enhanced the growth of TYS cells in vitro and in vivo . Furthermore, we examined the expression of TSC-22 mRNA in several human salivary gland tumors. The mRNA expression of TSC-22 in benign and malignant salivary gland tumors was significantly decreased when compared to that in tumor-free salivary glands ( P < 0.05; one-way ANOVA), and in some salivary gland tumors, the expression of TSC-22 mRNA was not detectable by reverse transcription-PCR. These results suggest that down-regulation of TSC-22 may play a major role on salivary gland tumorigenesis.

Mechanism of anticancer host response induced by OK-432, a streptococcal preparation, mediated by phagocytosis and Toll-like receptor 4 signaling.

Abstract: It has previously been reported by our group that Toll-like receptor (TLR) 4 is involved in anticancer immunity induced by OK-432, a Streptococcus-derived immunotherapeutic agent. However the detailed mechanism of the OK-432-induced immune response via TLR4 remained uncertain, because it may not be possible for OK-432, which consists of whole bacterial bodies, to bind directly to TLR4. In the current study, we conducted in vitro and in vivo experiments to investigate the hypothesis that OK-432 may first be captured and dissolved by phagocytes and that the active components released by the cells may then induce host responses via TLR4. TS-2 monoclonal antibody, which recognizes an active component of OK-432 designated OK-PSA was used in the current study. First, it was observed that OK-432-induced cytokine production by dendritic cells (DCs) and macrophages was significantly inhibited in vitro by cytochalasin B, a phagocytosis inhibitor. Immunofluorescence staining using TS-2 demonstrated that OK-432 was captured and dissolved by phagocytes. OK-PSA was detected in the supernatants derived from OK-432-treated DC culture by enzyme-linked immunosorbent assay using TS-2. Supernatants from OK-432-treated DC culture increased nuclear factor (NF)-kappaB activity in TLR4-expressing cells, and the increased activity was inhibited by TS-2 antibody. OK-432 itself did not activate NF-kappaB in these cells. In in vivo experiments, the anticancer effect of OK-432 was significantly inhibited by suppression of phagocytosis activity by cytochalasin B. In this case, the amount of OK-PSA, an active component of OK-432, in the sera was also reduced by cytochalasin B. These findings elucidated the mechanism mediated by phagocytosis and TLR4 signaling in the immune effect of OK-432.

The Effects of Plant Flavonoids on Mammalian Cells:Implications for Inflammation, Heart Disease, and Cancer

Abstract: Flavonoids are nearly ubiquitous in plants and are recognized as the pigments responsible for the colors of leaves, especially in autumn. They are rich in seeds, citrus fruits, olive oil, tea, and red wine. They are low molecular weight compounds composed of a three-ring structure with various substitutions. This basic structure is shared by tocopherols (vitamin E). Flavonoids can be subdivided according to the presence of an oxy group at position 4, a double bond between carbon atoms 2 and 3, or a hydroxyl group in position 3 of the C (middle) ring. These characteristics appear to also be required for best activity, especially antioxidant and antiproliferative, in the systems studied. The particular hydroxylation pattern of the B ring of the flavonoles increases their activities, especially in inhibition of mast cell secretion. Certain plants and spices containing flavonoids have been used for thousands of years in traditional Eastern medicine. In spite of the voluminous literature available, however, Western medicine has not yet used flavonoids therapeutically, even though their safety record is exceptional. Suggestions are made where such possibilities may be worth pursuing.

Epigenetics: Regulation Through Repression

Abstract: Epigenetics is the study of heritable changes in gene expression that occur without a change in DNA sequence. Epigenetic phenomena have major economic and medical relevance, and several, such as imprinting and paramutation, violate Mendelian principles. Recent discoveries link the recognition of nucleic acid sequence homology to the targeting of DNA methylation, chromosome remodeling, and RNA turnover. Although epigenetic mechanisms help to protect cells from parasitic elements, this defense can complicate the genetic manipulation of plants and animals. Essential for normal development, epigenetic controls become misdirected in cancer cells and other human disease syndromes.

Transforming Growth Factor-β1 Mediates Epithelial to Mesenchymal Transdifferentiation through a RhoA-dependent Mechanism

Abstract: Transforming growth factor-beta1 (TGF-beta) can be tumor suppressive, but it can also enhance tumor progression by stimulating the complex process of epithelial-to-mesenchymal transdifferentiaion (EMT). The signaling pathway(s) that regulate EMT in response to TGF-beta are not well understood. We demonstrate the acquisition of a fibroblastoid morphology, increased N-cadherin expression, loss of junctional E-cadherin localization, and increased cellular motility as markers for TGF-beta-induced EMT. The expression of a dominant-negative Smad3 or the expression of Smad7 to levels that block growth inhibition and transcriptional responses to TGF-beta do not inhibit mesenchymal differentiation of mammary epithelial cells. In contrast, we show that TGF-beta rapidly activates RhoA in epithelial cells, and that blocking RhoA or its downstream target p160(ROCK), by the expression of dominant-negative mutants, inhibited TGF-beta-mediated EMT. The data suggest that TGF-beta rapidly activates RhoA-dependent signaling pathways to induce stress fiber formation and mesenchymal characteristics.

Biochemistry and Molecular Biology of Gelatinase B or Matrix Metalloproteinase-9 (MMP-9)

Abstract: The matrix metalloproteinases (MMPs) form an enzyme family of which gelatinase B (MMP-9) represents the largest and most complex member. We focus here on the biochemical properties, regulation, and functions of gelatinase B. The tight regulation of gelatinase B activity is highly complex and is established at five different levels. The transcription of the gelatinase B-gene depends on various cis-elements in its gene promotor and is induced or repressed by a large variety of soluble factors, including cytokines, growth factors, and hormones and by cellular contacts acting through specific signaling pathways. The specific regulation of its secretion occurs in cells storing gelatinase B in granules. After secretion, progelatinase B must be activated through an activation network. The enzyme activity is further regulated by inhibition and by other mechanisms, such as fine-tuning and stabilization by glycosylation. The ability of gelatinase B to degrade components of the extracellular matrix and to regulate the activity of a number of soluble proteins confers an important role in various physiological and pathological processes. These include reproduction, growth, development, inflammation, and vascular and proliferative diseases.

Toll-like receptors and cancer.

Abstract: Toll-like receptors (TLRs) are a family of pattern recognition receptors that are best-known for their role in host defence from infection. Emerging evidence also suggests that TLRs have an important role in maintaining tissue homeostasis by regulating the inflammatory and tissue repair responses to injury. The development of cancer has been associated with microbial infection, injury, inflammation and tissue repair. Here we discuss how the function of TLRs may relate to these processes in the context of carcinogenesis.