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Biomedical subjects

W Yasui

Publications and source records attributed to W Yasui.

At least 55 records · Page 3Linked to original sources
PubMed2000

Helicobacter pylori infection and carcinogenesis of the stomach.

INTRODUCTION: Human stomach carcinogenesis occurs after a multi-step process of genetic and epigenetic alterations in oncogenes, tumor-suppressor genes, cell-adhesion molecules, telomere and telomerase activity as well as genetic instability at several microsatellite loci. RESULTS AND DISCUSSION: These sequential alterations found in gastric cancer differ between the two histological types, indicating that different genetic pathways exist for well-differentiated or intestinal-type and poorly differentiated or diffuse-type gastric cancers, even though both types of gastric cancer may arise from epithelial "stem cells", which express human telomerase reverse transcriptase (hTERT) protein and telomerase activity. Infection with Helicobacter pylori, which evidently causes the release of reactive oxygen species (ROMs) and reactive nitrogen species (NO), may be a strong trigger for "stem cell" hyperplasia in intestinal metaplasia, followed by telomere reduction and increased telomerase activity as well as hTERT overexpression. They may precede DNA replication error, DNA hypermethylation, CD44 abnormal transcript, and p53 mutations, all of which occur in at least 30% of intestinal metaplasias as early events of multi-step pathogenesis of well-differentiated type gastric cancer. Here, we propose a new concept for gastric preneoplasic lesion, "metaplastic dysplasia", based on our molecular observations.

Cell Transformation, Neoplastic↗
PubMed2000

Induction of angiogenesis by hyperplastic colonic mucosa adjacent to colon cancer.

We determined whether hyperplastic mucosa adjacent to colon cancer contributes to neoplastic angiogenesis. Surgical specimens of human colon cancer (40 Dukes' stage B and 34 Dukes' stage C) were analyzed by immunohistochemistry for expression of proliferative and angiogenic molecules. The mucosa adjacent to Dukes' stage C tumors (but not Dukes' stage B tumors) had a higher Ki-67 labeling index and a higher expression of epidermal growth factor receptor and transforming growth factor-alpha than distant mucosa. The expression levels of vascular endothelial growth factor, basic fibroblast growth factor, interleukin-8, and the vascular density in the adjacent mucosa were similar to those in the tumor lesions and significantly higher than those in the distant mucosa. The expression of interferon-beta inversely correlated with the level of pro-angiogenic molecules and the vascular density. The injection of metastatic human colon cancer cells and murine colon cancer cells into the cecal wall of mice induced hyperplastic changes in the adjacent mucosa which expressed higher levels of epidermal growth factor receptor, basic fibroblast growth factor, and vascular endothelial growth factor, and lower levels of interferon-beta than did the control mucosa, which directly correlated with the degree of hyperplasia. These data suggest that metastatic human colon cancer cells can induce hyperplasia in the adjacent mucosa, which in turn produces angiogenic molecules that contribute to neoplastic angiogenesis.

Animals↗
PubMed2000

Clinicopathological implication of cripto expression in early stage invasive cervical carcinomas.

This study evaluates the expression of cripto (CR-1) protein in matched sets of non-neoplastic cervical epithelium, primary cervical carcinoma and metastatic tumours in the lymph nodes to investigate its role in uterine cervical cancer development and progression. Ninety-four primary cervical carcinomas in an early clinical stage and having the same surgical treatment modality were analysed. Immunoreactivity in the primary tumour was compared with that of non-neoplastic cervical epithelium and metastatic lymph nodes. The conventional clinicopathological prognostic variables for cervical carcinomas such as grade, tumour size, depth of invasion, parametrial and endometrial extension, lymphovascular space involvement and lymph node metastasis status were also compared with CR-1 expression of the primary tumour. Strong CR-1 immunopositivity was significantly correlated with tumour size and lymphovascular space involvement (P < 0.05). Furthermore, a significant relationship was found between CR-1 immunoreactivity and endometrial extension as well as parametrial involvement (P < 0.05). Interestingly, the CR-1 expression level was increased in metastatic lymph nodes compared with their primary tumours. These results suggest that CR-1 may contribute to disease progression in cervical carcinomas.

Epidermal Growth Factor↗
PubMed2000

Expression of cell cycle regulators and growth factor/receptor systems in gastric carcinoma in young adults: association with Helicobacter pylori infection.

We studied the expression of cell cycle regulators and growth factor-receptor systems in gastric carcinoma in young adults and tried to clarify the specific alterations associated with H. pylori. We studied 33 young patients (18-29 years old, mean age 26.4) with gastric carcinoma. The patients were classified into two groups according to the degree of atrophic gastritis. Then we examined the expression of p53, cripto, cyclin-E, c-met, c-erbB2 and TGF-alpha immunohistochemically and compared the results between the two groups. The results were compared with 66 sex-, tumor histology-, and depth-matched elder controls (36-86 years old, mean age 64.0). H. pylori was judged by Giemsa staining. Seventeen patients had atrophic changes in the corpus (Group A), while 16 showed superficial gastritis or normal mucosa (Group S). All 17 patients of Group A showed H. pylori infection, while the 3 of the 16 members of Group S did not have H. pylori. p53 overexpression was observed more frequently in Group S (88%) than in Group A (41%, p<0.05). In the 3 patients without H. pylori infection, all carcinoma specimens showed p53 overexpression. Overexpression of cyclin-E was detected in 4 patients from Group S. On the other hand, cripto was observed more frequently in Group A than in Group S. No obvious differences were observed in c-erbB2, TGF-alpha and c-met expression. Overall, p53 overexpression was detected more frequently in younger than in older patients, whereas cripto expression was less detected. These results suggest that p53 and cyclin-E may act in an H. pylori-independent or -adjunctive manner for gastric carcinogenesis. Cripto expression might be correlated tightly with H. pylori infection.

Adolescent↗
PubMed2000

Genetic and epigenetic alterations in multistep carcinogenesis of the stomach.

An accumulation of multiple genetic and epigenetic alterations of oncogenes, tumor suppressor genes, DNA repair genes, cell cycle regulators, cell adhesion molecules, and the growth factor/receptor system is involved in the course of multistep conversion of normal epithelial cells to clinical gastric cancer. Some of them differ depending on the histological type, well-differentiated (intestinal) and poorly differentiated (diffuse) types, suggesting the presence of two distinct genetic pathways. Genetic instability, chromosomal instability (telomere reduction), and immortality (activation of telomerase and expression of telomerase reverse transcriptase: TERT) participate in the initial step of stomach carcinogenesis. Because TERT protein expression precedes the telomerase activities in precancerous lesions, TERT expression may be a prerequisite for telomerase activation. The cyclin E gene is amplified in 15%-20% of gastric cancer. Reduced expression of a cyclin-dependent kinase (CDK) inhibitor, p27Kip1, is frequently found in gastric cancer associated with high grade malignancy. E2F-1, an important downstream target of cyclins/CDKs, is overexpressed in about 40% of gastric carcinomas, whereas gene amplification of E2F-1 rarely occurs. Loss of heterozygosity (LOH) of p73, the p53-related new tumor suppressor gene, preferentially occurs in well-differentiated adenocarcinomas of foveolar type expressing pS2, a gastric-specific trefoil factor, indicating the importance of p73 LOH in the genesis.

Adenocarcinoma↗
PubMed2000

Regulation of disease-progression genes in human gastric carcinoma cells by interleukin 8.

The expression of interleukin 8 (IL-8) by human gastric carcinomas directly correlates with tumor vascularity and disease progression. To determine whether IL-8 can act in an autocrine manner to regulate the expression of other disease-progression genes, we examined the expression of IL-8 receptors IL-8RA (CXCR1) and IL-8RB (CXCR2) in six different human gastric carcinoma cell lines and 38 surgical specimens of human gastric carcinomas. All of the gastric carcinoma cell lines expressed mRNA and protein for IL-8RA and IL-8RB protein. In all surgical specimens, the majority of the tumor cells and small vessel endothelial cells stained positive for IL-8RA and IL-8RB protein. In vitro treatment of human gastric cancer MKN-1 cells with exogenous IL-8 enhanced the expression of epidermal growth factor receptor, type IV collagenase (metalloproteinase-9), vascular endothelial growth factor, and IL-8 mRNA. In contrast, treatment with exogenous IL-8 decreased expression of E-cadherin mRNA. IL-8 treatment increased invasive capacity of MKN-1 cells, which was associated with activity of metalloproteinase-9. Collectively, these results demonstrate that human gastric carcinoma cells express receptors for IL-8 and that IL-8 may play a role in the progressive growth of human gastric carcinoma by autocrine/paracrine mechanisms.

Cell Membrane↗
PubMed1999

Alterations of p73 preferentially occur in gastric adenocarcinomas with foveolar epithelial phenotype.

To establish the possible involvement of p73, a newly discovered p53-related candidate as a tumor-suppressor gene in human stomach carcinogenesis, the allelic status, allele-specific expression and mutations of the gene were investigated using PCR-restriction fragment length polymorphism (PCR-RFLP) analysis, RT-PCR SSCP analysis and direct DNA sequencing in 95 gastric adenocarcinomas. Of these, 32 exhibited the heterozygous p73 allele for the StyI restriction site in exon 2. Among these, the cancer DNA of 12 revealed loss of heterozygosity (LOH) of p73. All of the cancers with p73 LOH exhibited phenotypes of foveolar epithelium of the stomach. RT-PCR SSCP analysis of p73 heterozygous cases demonstrated not only bi-allelic expression of the gene but also relatively reduced expression of the affected allele in 6 of 8 tumors with p73 LOH. No gene mutation was detected in the remaining allele of LOH-positive cancers. Our results suggest that alterations of p73, including LOH and abnormal expression, may play roles in the genesis of foveolar-type gastric adenocarcinomas, though this is not in line with a classical Knudson's "2-hit" model.

Adenocarcinoma↗
PubMed1999

Expression of the E2F family in human gastrointestinal carcinomas.

The E2F family of transcription factors plays a key role in the control of cell-cycle progression. Some family members may act as oncogenes, others as tumor-suppressor genes. The genetic changes and the expression of E2F-1 and -3 were examined in human gastric and colorectal carcinomas by Southern, Northern and Western blots. Gene amplification of E2F-1 was detected in 4% (1/23) of gastric carcinomas and 25% (3/12) of the colorectal carcinomas. Increased expression of E2F-1 mRNA was observed in 40% (12/30) of the gastric carcinomas and in 60% (3/5) of the colorectal carcinomas in comparison with the corresponding non-neoplastic mucosa. Over-expression of E2F-1 protein was confirmed in many of the gastric carcinomas. In contrast, expression levels of E2F-3 mRNA were lower in 70% (21/30) of the gastric carcinomas and in 20% (1/5) of the colorectal carcinomas than in their corresponding normal counterparts, while gross alteration of the E2F-3 gene was not detected. These results suggest that gene amplification and anomalous expression of the E2F gene may permit development of gastrointestinal carcinomas.

Adult↗
PubMed1999

Immuno-histochemical detection of human telomerase catalytic component, hTERT, in human colorectal tumor and non-tumor tissue sections.

Human telomerase is expressed in germ tissues and in the majority of primary tumors. Cell renewal tissues and some pre-cancerous tissues also have weak telomerase activity. Yet, neither the exact location and frequency of telomerase-positive cells nor the changes in telomerase expression during differentiation or carcinogenesis of individual cells are known. This paper reports on the expression of hTERT (telomerase reverse transcriptase) protein in tumor and non-tumor colorectal tissues by Western blotting and tissue sections by immunohistochemistry using antibodies raised against partial peptides of hTERT. Though telomerase activity and hTERT expression at both mRNA and protein levels were generally higher in tumor part than in non-tumor part, these two were not always correlated: expression of hTERT did not always give rise to high telomerase activity. Colonic carcinoma cell nuclei were stained with anti-hTERT antibodies but not with antigen-preabsorbed antibodies. In normal mucosa, hTERT protein was expressed, though weaker than in carcinoma, in all colonic crypt epithelial cells except those at the tip; the expressing-cell distribution was much wider than that of Ki-67 positive cells which were located at the bottom of the crypt. Isolated crypt contained a significant level of hTERT protein revealed by Western blotting, while having very weak telomerase activity. Telomerase activity was detected in epithelial cells only at the bottom half of the crypt. Specific hTERT-staining was positive in tissue lymphocytes but negative in almost all other stromal cells. It is of interest to see whether a significant level of hTERT expression with low telomerase activity is characteristic of physiologically regenerating tissues containing stem cells. In situ detection of the hTERT protein will permit further analysis of cancer diagnosis and stem cell differentiation.

Blotting, Western↗
PubMed1999

Effect of antisense human telomerase RNA transfection on the growth of human gastric cancer cell lines.

The majority of gastric cancers express high levels of human telomerase template RNA (hTR) that is essential for cellular survival. In this study, we examined whether antisense hTR (ahTR) had a growth inhibitory effect on three gastric cancer cell lines, MKN-1, MKN-28, and TMK-1, through transfection via an ahTR expression vector. Both the ahTR transfected MKN-1 and TMK-1 cells changed morphologically into multinucleate giant cells, and subsequently underwent cell death. Conversely, the ahTR transfected MKN-28 cells survived over 50 PDs in spite of telomere shortening. Surprisingly, high levels of telomerase activity were observed in the telomere-reduced cells. Furthermore, the expression of mRNAs for p21/Waf1/Cip1/Sdi1, IRF-1 and IFN inducible 6-16 was higher in the telomere-reduced cells than in the parental cells. These results suggest overall that the ahTR expression may bring about telomere shorting, leading to cell death or cellular senescence in gastric cancer cells.

Cell Cycle↗
PubMed1999

Overexpression of human telomerase RNA is an early event in oesophageal carcinogenesis.

Telomerase, the ribonucleoprotein enzyme that elongates telomeres, is repressed in normal human somatic cells but is reactivated during tumour progression. The purpose of this study was to investigate the localization of human telomerase RNA (hTR) expression in human oesophageal dysplasia and cancer by using in situ mRNA hybridization (ISH) with avidin-biotin staining. Ki-67 immunoreactivity was also examined. We analysed 51 squamous cell carcinomas, 9 dysplasias and 60 normal mucosae. The integrity of the mRNA in each sample was verified by using a poly d(T)20 probe. Seventy-six samples (63%) showed no mRNA degradation; these included 30 carcinomas, 7 dysplasias and 39 normal mucosae. At the single-cell level, high levels of hTR expression were found in the cytoplasm and especially in the nucleus. Most (>90%) cancer cells demonstrated high levels of hTR expression in 29 (97%) of the 30 tumours. Most dysplastic cells also showed high levels of hTR in all 7 dysplastic cases. In all 39 normal mucosae, most basal cells indicated high levels of hTR expression, which were also seen in infiltrating lymphocytes. The distribution of hTR-expressing cells was similar to that of Ki-67-positive cells. These data suggest that overexpression of hTR may be correlated with the proliferative activity that defined by Ki-67 immunoreactivity and is an early event in carcinogenesis of the oesophagus.

Esophageal Neoplasms↗
PubMed1999

Transfection of interleukin-8 increases angiogenesis and tumorigenesis of human gastric carcinoma cells in nude mice.

The growth and spread of tumour cells depends on adequate vasculature. We have previously reported that the expression of interleukin-8 (IL-8) directly correlates with the vascularity of human gastric carcinomas. To provide evidence for a causal role of IL-8 in angiogenesis and tumorigenicity of human gastric cancer, we used the lipofectin method to stably transfect the human TMK-1 gastric carcinoma cells (low endogenous IL-8) with an IL-8 expression vector or control vector. Transfection with IL-8 did not affect the proliferation of cultured cells, yet the culture supernatants of the transfected (but not control) cells stimulated proliferation of human umbilical vein endothelial cells. The IL-8-transfected and control cells were injected into the gastric wall of nude mice. IL-8-transfected cells produced rapidly growing, highly vascular neoplasms as compared to control cells. These results provide direct evidence for the role of IL-8 in the angiogenesis and tumorigenicity of human gastric carcinomas.

Animals↗
PubMed1999

Molecular-pathological diagnosis of gastrointestinal tissues and its contribution to cancer histopathology.

Multiple genetic and epigenetic alterations of cancer-related genes and molecules are involved in the course of the development and progression of gastrointestinal cancers. These include telomerase activation, genetic instability, and abnormalities of oncogenes, tumor suppressor genes, cell cycle regulators, cell adhesion molecules and DNA repair genes. By analyzing these alterations in pathology specimens, we can improve differential diagnosis of cancer, obtain information of grade of malignancy, and identify patients at high risk for developing multiple primary cancers. Since 1993, a system of molecular-pathological diagnosis was established, and has been performed as a routine service in collaboration with Hiroshima City Medical Association Clinical Laboratory. More than 10 000 cases of gastrointestinal biopsy and surgery have been analyzed, and additional information of differential diagnosis, biological malignancy and tumor multiplicity could be obtained. Molecular-pathological diagnosis may provide a new approach to cancer diagnosis and novel therapeutics for the 21st century. Furthermore, the analysis of the genetic and epigenetic abnormalities in clinical materials may clarify the molecular mechanism of carcinogenesis and comparative morphological changes. From the analyses of p27KIP1 and telomerase in gastrointestinal adenomas, we have learned that morphological abnormality of the nucleus is an indicator for cells with immortality and malignant potential that must participate in super-early diagnosis (detection of true precancerous lesions) of gastrointestinal cancer. Molecular-pathological diagnosis thus contributes to detailed understanding of cancer histopathology and improves the histopathological diagnosis.

Adenocarcinoma↗
PubMed1999

No mutations of the Smad2 gene in human sporadic gastric carcinomas.

BACKGROUND: The majority of cancer cells escape from TGF-beta-mediated growth control. However, the mechanism of resistance to the growth inhibitory effects by TGF-beta is not clear. TGF-beta signaling is initiated when the type I receptor phosphorylates the SMAD proteins, Smad2 and Smad3. Recently, mutations of Smad2 have been detected in human colon and lung cancers. Mutation of coding sequences of Smad2 in gastric carcinomas has not yet been elucidated adequately. METHODS: PCR-SSCP analysis of the entire coding region of Smad2 in 35 human sporadic gastric cancers and eight gastric cancer cell lines was performed using 11 sets of intron-based primers. RESULTS: No mutations of Smad2 were detected in any tumor or cell line. CONCLUSIONS: The results suggest that mutation of Smad2 does not play a key role in human stomach carcinogenesis.

DNA-Binding Proteins↗
PubMed1999

Silencing of the CD44 gene by CpG methylation in a human gastric carcinoma cell line.

We analyzed 8 human gastric carcinoma cell lines for the expression of CD44 by northern blot analysis and reverse transcription-polymerase chain reaction (RT-PCR), and identified 1 cell line MKN-28 that did not express CD44. In an attempt to clarify the mechanism responsible for the inactivation of CD44 gene expression in this cell line, we investigated the methylation status around the promoter region of CD44 gene by digestion of the DNA with the methylation-sensitive restriction enzyme HpaII. The promoter region of CD44 in MKN-28 revealed hypermethylation, whereas other CD44-positive cell lines did not. Furthermore, treatment of MKN-28 with the demethylating agent 5-azacytidine restored the expression of the gene. These results suggest that CD44 expression is controlled by a DNA hypermethylation mechanism in MKN-28.

DNA Methylation↗
PubMed1999

Immunohistochemical detection of human telomerase reverse transcriptase in normal mucosa and precancerous lesions of the stomach.

Telomerase activity confers cell immortality through stabilization of the chromosome, participating in the development of a majority of human cancers. Human telomerase reverse transcriptase (TERT) has been identified as a catalytic subunit of telomerase, and is overexpressed in most gastric carcinomas. We immunohistochemically examined the expression of TERT in normal gastric mucosa and candidate precancerous lesions such as intestinal metaplasia and adenoma. In non-neoplastic gastric mucosa including intestinal metaplasia and normal fundic mucosa, weak but significant expression of TERT was detected in nuclei of epithelial cells located in the lower two-thirds of the glands (wider than the proliferative zone). The telomerase activity was found in a half of gastric adenomas, whose levels of the activity were about 10% of those in gastric carcinomas. TERT protein was expressed in the nuclei of the adenoma cells at moderate levels, that were not necessarily comparable with the telomerase activities. These findings overall suggest that TERT expression may be one of the prerequisites for telomerase activation in an early stage of stomach carcinogenesis.

Adenoma↗