Biomedical subjects

Tsuneo Ikenoue

Publications and source records attributed to Tsuneo Ikenoue.

24 records · Page 2Linked to original sources

PubMed2004

Rapid detection of mutations in the BRAF gene using real-time polymerase chain reaction and melting curve analysis.

The BRAF gene is mutated in 66% of melanomas and less frequently in various human cancers. More than 80% of these mutations are T to A transversions at nucleotide 1796 (T1796A), leading to a substitution of glutamic acid for valine at amino acid 599 (V599E). We established a new method for rapidly detecting V599E mutations using real-time polymerase chain reaction and melting curve analysis. Furthermore, we examined mutations in gastrointestinal cancer cell lines using this method. We found a mutation in 1 of 12 (8%) colorectal cancer cell lines, but no mutation was detected in 9 gastric cancer cell lines. These results suggest that the BRAF mutation is unlikely to be involved in gastric carcinogenesis.

Amino Acid Substitution↗

PubMed2003

Functional analysis of mutations within the kinase activation segment of B-Raf in human colorectal tumors.

Mutations in the B-Raf gene have been reported in a number of human cancers, including colorectal carcinoma. More than 80% of the B-Raf mutations were V599E. Although other mutations have been reported, their functional consequences were unclear. Here, we examined the effect of colon tumor-associated B-Raf mutations within the kinase activation segment, including V599E, on extracellular signal-regulated kinase (Erk) and nuclear factor kappaB (NFkappaB) signaling, and on the transformation of NIH3T3 fibroblasts. Among the six mutations examined, only the B-Raf V599E and K600E mutations greatly increased Erk and NFkappaB signaling, and the transformation of NIH3T3 cells. The B-Raf F594L mutation moderately elevated Erk signaling and NIH3T3 transformation, but did not significantly increase NFkappaB signaling. Although the basal kinase activity of the B-Raf T598I mutant was comparable with that of wild-type, its oncogenic Ras-induced kinase activity was decreased to 60% of wild-type activity. The B-Raf D593V and G595R mutants showed severely reduced kinase activity and affected neither NFkappaB signaling nor NIH3T3 transforming activity. These results suggest that the B-Raf activation segment mutations other than V599E reported in colorectal tumors do not necessarily contribute to carcinogenesis by increasing kinase and transforming activities.

14-3-3 Proteins↗

PubMed2002

The evaluation of putative virulence factors of Helicobacter pylori for gastroduodenal disease by use of a short-term Mongolian gerbil infection model.

Few virulence determinants of Helicobacter pylori have been tested in vivo. We conducted this study to establish an animal model for their screening. Six-week-old male Mongolian gerbils were inoculated with wild-type H. pylori (TN2) or its isogenic mutant with deletion of cagE (TN2DeltacagE), total cag pathogenicity island (TN2DeltacagPAI), HP0499 (TN2DeltaHP499), or HP0638 (TN2DeltaHP638) (n=5 each). The animals were killed 3 weeks later, and the density of bacteria and the degree of inflammation in the stomach were compared. Infection was established in all animals except those inoculated with TN2DeltaHP638. TN2 and TN2DeltaHP499, but not TN2DeltacagE and TN2Deltacag PAI, induced intense inflammation, although the densities of bacteria were similar. The Mongolian gerbil model was useful for the screening of virulence determinants in vivo, which confirmed the importance of cag PAI while questioning that of HP0499.

Animals↗

PubMed2002

Relationship between nuclear factor-kappaB activation and virulence factors of Helicobacter pylori in Japanese clinical isolates.

BACKGROUND: Several factors have been proposed as a possible virulence determinant of Helicobacter pylori infection. The aim of the present study was to evaluate these candidates in nuclear factor (NF)-kappaBeta activation, which is a critical regulator of genes involved in inflammatory reactions. METHODS: We determined the status of cagE, iceA, HP0441 (a virB4 homolog), the s1 signal sequence of vacA and babA2 by polymerase chain reaction, all of which are candidate virulence determinants, in 107 H. pylori strains isolated from Japanese patients. Nuclear factor-kappaBeta activation was evaluated by the luciferase reporter assay. The gastric mucosa of the hosts was examined histologically. RESULTS: The cagE gene was positive in 102 (95.3%) strains, iceA1 was positive in 71 (66.4%) strains, HP0441 was positive in 68 (63.6%) strains, vacA s1 was positive in 105 (98.1%) strains and babA2 was positive in 103 (96.3%) strains. Nuclear factor-kappaBeta was activated by all cagE-positive strains, but was not activated by any of the cagE-negative strains. The status of iceA or HP0441 was not associated with NF-kappaBeta activation. Neutrophil infiltration in gastric mucosa was significantly more severe in patients infected with cagE-positive strains than in patients infected with negative strains. No association was found between the degree of neutrophil infiltration and the status of HP0441 or iceA. Due to very high positivity of vacA s1 and babA2 in Japanese strains, their roles remain to be investigated. CONCLUSIONS: The cag pathogenicity island (PAI) status, as determined by cagE polymerase chain reaction, but not the status of iceA or HP0441, is closely associated with NF-kappaBeta activation and the degree of gastric mucosal inflammation in the hosts.

Adult↗

PubMed2002

Relationship between age and site of colorectal cancer based on colonoscopy findings.

BACKGROUND: Colorectal cancer occurs more frequently in older people. Because the population of aged persons is increasing, a better understanding of the characteristics of colorectal cancer with respect to age would be useful. The purpose of this study was to determine whether there is any relationship between the site of colorectal adenoma and adenocarcinoma in the colon and age. METHODS: Colonoscopy was performed (September 1995 to December 1998) on 2942 consecutive patients (1907 men, 1035 women; mean age 61 years, range 11 to 95 years) with no history of colorectal adenoma, adenocarcinoma, or inflammatory bowel disease. The occurrence of colorectal neoplasia, histologically proven as adenoma or adenocarcinoma, was analyzed for a possible association between site in the colon and patient age. RESULTS: Adenocarcinoma was found in 191 patients (196 lesions). The proportion of patients with right-sided colonic adenocarcinoma increased with patient age: < 50 years, 15% (2/13); 50 to 59 years, 21% (8/39); 60 to 69 years, 32% (18/57); 70 to 79 years, 42% (25/49); > or =80 years, 57% (16/28). The proportion of patients with right-sided adenoma did not significantly differ among age groups: < 50 years, 40% (98/246); 50 to 59 years, 41% (280/678); 60 to 69 years, 46% (459/1001); 70 to 79 years, 53% (270/508); and > or =80 years, 57% (87/152). CONCLUSION: The frequency of right-sided colon cancer increases with patient age. Hence, colonoscopy may be indicated in the elderly for colorectal cancer screening. Over half of colon carcinomas may be missed if sigmoidoscopy alone is used for screening.

Adenocarcinoma↗

PubMed2002

Analysis of the beta-catenin/T cell factor signaling pathway in 36 gastrointestinal and liver cancer cells.

We investigated the frequency and mechanism of beta-catenin/T cell factor (Tcf) signaling activation in a panel of 36 human gastrointestinal and liver cancer cell lines. Reporter assay and electrophoretic mobility shift assay revealed that the beta-catenin/Tcf signaling was upregulated in 12 of 12 (100%) colorectal, 5 of 8 (68%) gastric, 2 of 7 (29%) hepatic, and none of 9 pancreatic cancer cell lines. The activation of the pathway was mainly due to the mutation of adenomatous polyposis coli (APC) or beta-catenin, and Tcf-4 was highly expressed in these cell lines with upregulated signaling. Nuclear beta-catenin was observed not only in the signaling-activated cell lines, but also in 14 of 25 (56%) primary gastric cancers, 15 of 20 (75%) colon cancers, 5 of 19 (26%) hepatocellular carcinomas, and none of 13 pancreatic cancers. The presence of signaling-upregulated gastric cancer cell lines with intact APC and beta-catenin suggests the involvement of other mechanisms than mutations of APC or beta-catenin.

Carcinoma, Hepatocellular↗