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Biomedical subjects

A Ochiai

Publications and source records attributed to A Ochiai.

At least 127 records · Page 7Linked to original sources
PubMed1995

c-erbB-2 gene product directly associates with beta-catenin and plakoglobin.

Association of the c-erbB-2 oncogene product with the cadherin-catenin complex has been demonstrated in human cancer cell lines. Although beta-catenin and plakoglobin have been proven to be crucial for the association, no previous study has shown whether the interactions are direct or indirect. In the present study, the c-erbB-2 gene product was shown by far-Western blotting analysis to associate directly with both beta-catenin and plakoglobin through its cytoplasmic domain core region, which showed extensive homology with epidermal growth factor receptor. These data suggest that c-erbB-2-induced signaling is also directly liked to the cadherin-mediated cell adhesion and "invasion-suppressor" system through beta-catenin and plakoglobin in cancers.

Adenocarcinoma↗
PubMed1995

Mutant K-ras in apparently normal mucosa of colorectal cancer patients. Its potential as a biomarker of colorectal tumorigenesis.

BACKGROUND: The best way to reduce the incidence of colorectal cancer mortality would be to prevent this cancer. However, none of the biomarkers proposed can accurately identify persons at increased risk of colorectal cancer or those at low risk. As a possible genetic biomarker, K-ras mutations, which are frequently found in colorectal cancers, were analyzed in apparently normal colorectal mucosa. METHODS: Nonneoplastic mucosa and tumor tissues were collected at surgery from 70 patients with colorectal cancer: one sample each from 50 patients (group A) and multiple samples from the other 20 patients (group B). Mutant K-ras codon 12 was analyzed by the enriched polymerase chain reaction (EPCR), by which one mutant can be detected among 10(3) to 10(4) normal alleles. RESULTS: Only with the aid of EPCR was mutant K-ras detected in nonneoplastic mucosa of nine patients (18%) in Group A and five patients (25%) in Group B. This increased incidence could be attributed to the multiple tissue sampling. The presence of mutant K-ras in nonneoplastic mucosae was not consistently correlated with that in the tumors. These findings suggest that the mutant K-ras identified in nonneoplastic mucosa actually represents de novo mutations, which may be initiated by different etiologic factors and at different times. CONCLUSION: Mutant K-ras detected in apparently normal mucosa should be a useful biomarker for identifying persons at higher risk of colorectal cancer. Our study also emphasizes the need for improving the method for sample collection to achieve true representation of the colorectal mucosa.

Adenocarcinoma↗
PubMed1995

Frequent and characteristic K-ras activation in aberrant crypt foci of colon. Is there preference among K-ras mutants for malignant progression?

BACKGROUND: To investigate very early lesion of colorectal cancer, K-ras activation and nuclear p53 accumulation were studied in aberrant crypt focus (ACF). METHODS: ACF were microscopically identified in grossly normal mucosa of patients with colorectal cancer who underwent surgery. Each ACF was microdissected from the surgical specimen and divided into two pieces, one for histologic and immunohistochemical examinations and the other for K-ras activation. K-ras mutations in codons 12 and 13 were sequenced after being screened by polymerase chain reaction amplification followed by restriction fragment length polymorphism analysis. Intranuclear accumulation of p53 protein was immunostained with the avidin-biotin complex method. RESULTS: ACF was predominantly distributed in the sigmoid colon and rectum, and its incidence was increased with age. Unexpectedly, ACF was very rare in colons of three patients with hereditary nonpolyposis colorectal carcinoma. K-ras mutations were detected in 58% (33 of 57) of ACF cases and in 44% (11 of 25) of adenocarcinoma cases. Although GTT mutation in codon 12 was predominantly observed in adenocarcinoma (10 of 11), GAT mutation (12 of 33) was as frequent as GTT mutation (11 of 33) in ACF together with mutation at codon 13 (7 of 33). No accumulation of p53 protein was found in any ACF. CONCLUSION: ACF were not diagnosed as neoplasms histologically, but they were considered to be neoplastic lesions, and K-ras activation is one of the key events to form ACF. The G-T substitution in K-ras codon 12 may undergo malignant growth easily compared with G-A substitution in colorectal carcinogenesis.

Adenocarcinoma↗
PubMed1995

Comparison of the molecular genetics of c-erb-B2 and p53 expression in stomach cancer in Britain and Japan.

BACKGROUND: Differences in the epidemiology and treatment outcome of stomach cancer have led to the suggestion that in Japan, this disease may be biologically less aggressive than that found in the West. The authors compared p53b and c-erb-B2 expression, trying to identify genetic differences in Japanese compared with Western stomach cancers. METHODS: Paraffin embedded formalin fixed tissues from 89 British and 89 matched Japanese patients were examined by immunohistochemistry after microwave treatment. Cases were matched for T-stage, year of surgery, and histopathologic grade. RESULTS: Tumors from 48 British and 46 Japanese patients expressed p53, whereas those of 27 British and 28 Japanese patients expressed c-erb-B2. No significant difference in the density or distribution of protein expression was found between the two populations. The distribution of expression between diffuse and intestinal types and the proportion of cases expressing both antigens were similar in the two groups. CONCLUSIONS: p53 and c-erb-B2 are expressed in the same way in stomach carcinomas from Japanese and British patients. This study found no evidence of genetic differences in the cancers from the two countries.

Gene Expression↗
PubMed1995

Frequent and characteristic K-ras activation and absence of p53 protein accumulation in aberrant crypt foci of the colon.

BACKGROUND/AIMS: The relationship of aberrant crypt foci (ACF) to colorectal carcinogenesis is still controversial. Histological examination and analyses of K-ras mutations and p53 gene expression were performed to characterize ACF. METHODS: ACF were identified microscopically in grossly normal colorectal mucosa. The ACF were separated into two pieces, one for histological and immunohistochemical examinations and the other for molecular analysis. K-ras mutations in codons 12 and 13 were analyzed by polymerase chain reaction amplification, followed by restriction fragment length polymorphism and sequencing analyses. Intranuclear p53 protein was immunostained by the avidin-biotin complex method. RESULTS: Histologically, elongation and apical branching of the crypts in ACF were striking. K-ras mutations were detected in 58% of ACF (33 of 57; 46% [26 of 57] in codon 12, and 12% [7 of 57] in codon 13) and in 44% of adenocarcinomas (11 of 25; all in codon 12). In ACF, GAT mutations (12 of 26) were as frequent as GTT mutations (11 of 26) in codon 12, although GTT mutations in codon 12 were predominant in adenocarcinomas (10 of 11). No accumulation of p53 protein was detected in any ACF, although it was detected in 52% (13 of 25) of the colorectal carcinomas. CONCLUSIONS: ACF do not seem histologically to be neoplasms, although genetically they are monoclonal lesions. K-ras mutation is critical in the formation of ACF, but p53 alteration could play a causal role in tumor progression.

Adult↗
PubMed1995

Reevaluation of prognostic factors in gastric leiomyosarcoma.

OBJECTIVES: The aim of our study was to reevaluate the prognostic factors in gastric leiomyosarcomas, particularly those under 6 cm, which, because of improved diagnostic techniques, make up a large proportion of this series, in contrast to previously published works. METHODS: The clinicopathological features in 83 patients with gastric leiomyosarcoma were reviewed. Cox's proportional hazards regression analysis was used to determine the prognostic factors. RESULTS: Sixty of 84 leiomyosarcomas (71.4%) were less than 6 cm in diameter. In univariate analysis, the following factors were considered to be unfavorable, with statistical significances: 1) presence of distant metastasis and/or direct invasion of adjacent structures at diagnosis (hazard ratio 36.60), 2) > or = 4 mitoses per 20 high-power fields (25.39), 3) severe nuclear atypia (16.74); 4) presence of ulceration of overlying gastric mucosa (12.57), and 5) diameter > or = 6 cm (5.57). Among these factors, mucosal ulceration has been identified as a new factor associated with poor prognosis. Histologically, the tumors with ulceration showed more severe nuclear atypia (p < 0.05), necrosis (p < 0.01), and a higher incidence of mitosis (p < 0.01), compared with tumors without ulceration. In multivariate analysis, factors 1, 2, and 3 were statistically significant, although neither size nor ulceration was significant. CONCLUSIONS: The presence of distant metastasis and/or direct invasion, high mitotic rate, and severe nuclear atypia were confirmed to be unfavorable prognostic indicators. Mucosal ulceration, indicating high proliferative activity of the tumor, even if small, suggests a poor prognosis, although it was not significant in multivariate analysis.

Combined Modality Therapy↗
PubMed1994

A truncated beta-catenin disrupts the interaction between E-cadherin and alpha-catenin: a cause of loss of intercellular adhesiveness in human cancer cell lines.

Cadherin cell adhesion molecules play an essential role in creating tight intercellular association and are considered to work as an invasion suppressor system of cancer cells. They form a molecular complex with catenins, a group of cytoplasmic proteins including alpha- and beta-catenins. While alpha-catenin has been demonstrated to be crucial for cadherin function, the role of beta-catenin is not yet fully understood. In this study, we analyzed the cadherin-catenin system in two human cell lines, HSC-39 and its putative subline HSC-40A, derived from a signet ring cell carcinoma of stomach. These cells grow as loose aggregates or single cells, suggesting that their cadherin system is not functional. In these cell lines, an identical 321-base pair in-frame mRNA deletion of beta-catenin was identified; this led to a 107-amino-acid deletion in the NH2-terminal region of the protein. Southern blot analysis disclosed a homozygous deletion in part of the beta-catenin gene. On the other hand, these cells expressed E-cadherin, alpha-catenin, and plakoglobin of normal size. Immunoprecipitation analyses showed that E-cadherin was coprecipitated with the mutated beta-catenin but not with alpha-catenin, and antibodies against beta-catenin did not copurify alpha-catenin. However, the recombinant fusion protein containing wild-type beta-catenin precipitated alpha-catenin from these cells. These results suggest that the dysfunction of E-cadherin in these cell lines is due primarily to its failure to interact with alpha-catenin, and that this defect results from the mutation in beta-catenin. Thus, it is most likely that the association between E-cadherin and alpha-catenin is mediated by beta-catenin, and that this process is blocked by NH2-terminal deletion in beta-catenin. These findings indicate that genetic abnormality of beta-catenin is one of the mechanisms responsible for loosening of cell-cell contact, and may be involved in enhancement of tumor invasion in human cancers.

Animals↗
PubMed1994

c-erbB-2 gene product associates with catenins in human cancer cells.

Phosphorylation of beta-catenin, an intracytoplasmic cadherin-binding protein, causes disruption of the cadherin-mediated cell adhesion system in cancer cells. A 185-kDa phosphorylated protein, identified as the c-erbB-2 gene product, was co-immunoprecipitated with the E-cadherin-catenin complex. Association of the c-erbB-2 gene product with the cadherin-catenin complex was proven to be mediated through beta-catenin and plakoglobin using an in vitro protein-protein precipitation system. These results indicate that the c-erbB-2 gene product associates with catenins and may regulate the cell adhesion and invasive growth of cancer.

Cadherins↗
PubMed1994

Association of plakoglobin with APC, a tumor suppressor gene product, and its regulation by tyrosine phosphorylation.

Plakoglobin is a cytoplasmic protein localized in both adherens junctions and desmosomes. Little is known about its function, but it may play a role in maintaining cell junction integrity. A partly homologous protein, beta catenin, is localized mainly in adherens junctions and plays a key role in cell adhesion by associating with cadherins, a family of Ca2+ dependent cell-to-cell adhesion molecules. Recently the product of APC, a tumor suppressor gene, was found to associate with beta catenin. In this study we demonstrated that plakoglobin also associates with APC and that tyrosine phosphorylated plakoglobin associates with cadherins but not with APC. These results suggest that plakoglobin could play a role in mediating the signals of APC by mutual interaction and that this may be regulated by tyrosine phosphorylation.

Adenocarcinoma↗
PubMed1994

Esophageal carcinoma simultaneously associated with gastric carcinoma: analysis of clinicopathologic features and treatments.

Among 1,420 patients with thoracic esophageal carcinoma, 85 (6.1%) had synchronous gastric carcinoma. Seventy-two patients (84.7%) underwent esophagectomy. Their operative mortality and prognosis were similar to those without gastric carcinoma. Among them, 25 patients, of whom the majority had advanced gastric carcinoma, underwent transthoracic esophagectomy with total gastrectomy (group A); eight died of esophageal cancer and four of gastric cancer. Forty-six patients, of whom the majority had gastric carcinoma in an early stage, underwent esophagectomy and esophagogastric anastomosis following partial gastrectomy or local treatment for gastric carcinoma (group B). None of the group B patients had recurrent gastric carcinoma. The operative burden was larger in group A. The 5-year survival rate for groups A and B were 38.8% and 23.0%, respectively. Esophagectomy and esophagogastric anastomosis after limited treatment for gastric carcinoma is an adequate treatment for the majority. However, esophagectomy and total gastrectomy are recommended for patients with advanced gastric carcinoma.

Aged↗
PubMed1994

Frequent p53 mutation in mouse tumors induced by repeated beta-irradiation.

On examination of cDNA of the p53 gene in 65 murine tumors of the skin and bone produced by repeated exposure to a suprathreshold dose of 1-8 Gy of 90Sr-90Y beta-radiation per exposure, we found 20 cases of mutation: 11 minute deletions (loss of 1-24 bp), including two cases possibly due to aberrant splicing; three insertions of 4-8 bp; and six base-pair substitutions, including four at CpG sites, three being identical changes at codon 122 (a p53 hot spot). All but one of these mutations were confined to the central region of the p53 gene. From frameshifts created by deletions and insertions, the minimum size of the mutant p53 proteins found in these tumors was estimated to be 55% of the intact size. Cells of 17 of 19 tested tumors with p53 mutation were positive for immunostaining of p53 proteins accumulated in the nuclei and so were clearly different from nonneoplastic cells. Ha-ras mutation was absent in these tumors, indicating that repeated beta-irradiation created a cell-growth stimulating effect similar to that of ras mutation.

Animals↗
PubMed1994

Neuroendocrine phenotype differentiation in a hamster lung epithelial cell line under low oxygen pressure or after transformation by diethylnitrosamine.

Oxygen pressure as low as 5% in the gas phase or 87 mmHg in the liquid phase induced various neuroendocrine cell (NEC) phenotypes in more than 80% of cells of a cloned fetal Syrian hamster lung epithelial cell line (M3E3/C3). Further, cells from a number of colonies transformed in an anchorage-independent manner by diethylnitrosamine (DEN) demonstrated a NEC phenotype. Since the cell line used is of a pluripotent stem cell type, both hypoxia and DEN appear to possess a potency for NEC phenotype induction.

Animals↗
PubMed1994

Frequent loss of alpha catenin expression in scirrhous carcinomas with scattered cell growth.

To investigate the mechanisms of disruption of cell-cell contact in scirrhous carcinoma cells, the expression of both E-cadherin and alpha catenin, which is an intracellular cadherin-binding molecule, were determined in scirrhous-type adenocarcinomas of the stomach and breast using immunohistochemical and immunoblotting techniques. The losses of E-cadherin expression in gastric and breast scirrhous adenocarcinomas were 18.1% and 0%, respectively, and those of alpha catenin expression were 54.6% and 75%, respectively. Frequent loss of alpha catenin expression occurred in scirrhous carcinomas with scattered cell growth in the stomach and the breast and showed no organ specificity. In addition, all the infiltrating lobular carcinomas, which also infiltrate the stroma as single cells, showed no E-cadherin or alpha catenin expression. These findings suggest that down-regulation of either alpha catenin or E-cadherin plays a critical role in the disruption of cell adhesion in carcinomas with scattered cell growth.

Adenocarcinoma, Scirrhous↗
PubMed1994

Point mutation of the E-cadherin gene in invasive lobular carcinoma of the breast.

Reduced or heterogeneous expression of E-cadherin has been demonstrated immunohistochemically in poorly differentiated carcinoma, which frequently shows weak intercellular adhesiveness and marked invasiveness. In vitro, not only reduced expression but also structural abnormalities of E-cadherin have been observed in human carcinoma cell lines which grow in a loosely adhering manner. To clarify the participation of structural abnormalities of E-cadherin in cancer invasion in vivo, sequence abnormalities were examined in the cadherin domain (exons 5, 6, 7 and 8) including the region essential for E-cadherin specific binding, using the polymerase chain reaction-single-strand conformation polymorphism method and direct sequencing in invasive lobular carcinoma of the breast, in which cancer cells become detached from each other and invade the stroma in a particularly scattered pattern. In 2 (10%) of the 20 cases examined, an identical sequence abnormality was detected in E-cadherin exon 7, i.e. a point mutation of codon 315 (AAT to AGT) which resulted in a single amino acid substitution (asparagine to serine). This mutation may abolish the E-cadherin-mediated cell-cell adhesion and be at least partly responsible for the weak intercellular adhesiveness and scattered histological pattern of the tumor.

Base Sequence↗
PubMed1994

Lecithinized superoxide dismutase enhances its pharmacologic potency by increasing its cell membrane affinity.

We performed the present study to clarify whether lecithinized superoxide dismutase (PC-SOD) enhanced its pharmacologic potency by increasing its cell membrane affinity. PC-SOD, in which 4 molecules of a phosphatidylcholine (PC) derivative were covalently bound to each dimer of recombinant human CuZn-SOD (rhCuZn-SOD), was shown to have a high membrane affinity using a laser confocal imaging technique. PC-SOD efficiently scavenged superoxide anion (O2-) produced by phorbol myristate acetate (PMA)-stimulated human neutrophils (IC50 0.60 U/ml), and it exerted a dose-dependent scavenging effect (IC50 1.27 U/ml) even when the neutrophils were washed after incubation with PC-SOD. In contrast, neither unmodified SOD nor polyethylene glycol-bound SOD (PEG-SOD) showed a scavenging effect for washed neutrophils, even at a high concentration (100 U/ml). PC-SOD also showed a strong protective effect against human vascular endothelial cell damage caused by O2- generated by stimulated neutrophils, and PC-SOD was approximately 100-fold more potent than unmodified SOD (in vitro IC50 100 U/ml for PC-SOD and > 10,000 U/ml for unmodified SOD). Moreover, PC-SOD (50,000 U/kg) had an inhibitory effect on ischemia-reperfusion paw edema in mice, whereas neither unmodified SOD nor PEG-SOD had any effect. These results suggest that PC-SOD (designed to target for cell membranes) exerted a far higher pharmacologic activity by increasing cell membrane affinity than unmodified SOD and may be potentially useful for various clinical applications.

Animals↗
PubMed1994

"Very well differentiated tubular adenocarcinoma" of the stomach: its endoscopic and histopathological characteristics.

Between 1986 and 1991, 31 patients having tubular adenocarcinoma with low cellular and structural atypism ("very well differentiated tubular adenocarcinoma:" tub 0) underwent surgery at the National Cancer Center Hospital (NCCH). Histologically, the 31 lesions in the 31 patients were very similar to those observed in gastric adenoma (World Health Organization) with severe atypism. Their malignancy could be diagnosed only on the basis of cellular atypism, i.e., uneven distribution of chromatin in the nucleus accompanied by irregularity in the size or shape of the spindle-form nucleus, abnormal nuclear polarity and/or obvious nucleoli. Histologically, the border between the tub 0 and adenomatous areas ('front line' of carcinoma) could not be identified within the neoplastic lesion, which showed relatively regularly shaped tubuli (less structural atypism). Of the 31 cases, 30 were solitary early gastric cancer (EGC). Their clinicopathological features were compared with those of 34 cases of gastric adenoma, 237 cases of solitary well differentiated (tub 1) and 127 cases of moderately differentiated (tub 2) tubular adenocarcinoma which had been resected at the NCCH during the same period. Most (75%) of the 30 tub 0 EGCs were type IIc (depressed) macroscopically, despite their histological similarity to gastric adenoma which showed a high (90%) elevated appearance incidence. The incidence of small lesions, < 2 cm in diameter, was highest in gastric adenoma (82%), followed by tub 0 (64%), although the tub 0 lesions showed a wide range of sizes. Small lesions were less frequent in the tub 1 (43%) and tub 2 (33%) cases. The incidence of submucosal invasion was significantly lower in tub 0 cases (17%) than in tub 1 (39%) and tub 2 (46%) cases (P < 0.05). No lymph node metastasis was seen in tub 0 cases, but was seen in 6.4% and 9.4% of tub 1 and tub 2 cases, respectively. With regard to the endoscopic appearance of depressed mucosal cancer, the incidence of encroachment (moth-eaten appearance) on the tips of folds was significantly lower (10%) and the appearance of marginal elevation was significantly higher (79%) in tub 0 than in tub 1 (each P < 0.05) or tub 2 (each P < 0.01). The results suggest that 'tub 0' can be regarded as a less malignant but not benign tumor, and that its endoscopic characteristics provide valuable information which can be used to ensure that patients receive suitable treatment.

Adenocarcinoma↗