BRAF/K-ras mutation, microsatellite instability, and promoter hypermethylation of hMLH1/MGMT in human gastric carcinomas.
BACKGROUND
The BRAF and K-ras genes are the most frequently mutated oncogenes in various human malignancies. We examined BRAF and K-ras mutations in human gastric cancer, and investigated their relationship with microsatellite instability (MSI) and the hypermethylation of promoter regions in hMLH1 and O6-methylguanine DNA methyltransferase (MGMT).


METHODS
Sixteen gastric cancer cell lines and 62 gastric cancer tissue samples were screened for BRAF and K-ras mutations by direct sequencing. We also performed a microsatellite assay and investigated methylation status in the promoter regions of hMLH1 and MGMT.


RESULTS
mutation was not found in any of the cancer cell lines examined. One (1.6%) cancer tissue sample showed a point mutation in the BRAF gene (GTG --> GAG; V599E). K-ras mutation (GGT --> GAT, G12D) was detected in five (31%) gastric cancer cell lines and in 1 (1.6%) gastric cancer tissue sample. In the gastric cancer tissue samples examined, MSI was detected in 23 (37%) samples. Hypermethylated promoter regions in hMLH1 and MGMT, respectively, were detected in 6 (10%) and 13 (21%) gastric cancer tissue samples. Microsatellite stable (MSS) tumors showed frequent lymphatic invasion (P = 0.050).


CONCLUSIONS
Although BRAF mutation has been reported in a variety of other human cancers, it is a rare event in the carcinogenesis and progression/development of gastric cancer.
Wu
Ming
M
Division of Surgical Pathology, Department of Biomedical Informatics, Kobe University Graduate School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe, 650-0017, Japan.
Semba
Shuho
S
Oue
Naohide
N
Ikehara
Nobunao
N
Yasui
Wataru
W
Yokozaki
Hiroshi
H
D048868:Adaptor Proteins, Signal Transducing; D020137:Base Pair Mismatch; D002277:Carcinoma / Q000235:genetics* / Q000473:pathology; D002352:Carrier Proteins; D019175:DNA Methylation; D004252:DNA Mutational Analysis; D004260:DNA Repair; D018450:Disease Progression; D011905:Genes, ras / Q000235:genetics*; D006801:Humans; D018895:Microsatellite Repeats; D000070957:MutL Protein Homolog 1; D009363:Neoplasm Proteins / Q000235:genetics; D009687:Nuclear Proteins; D019853:O(6)-Methylguanine-DNA Methyltransferase / Q000235:genetics; D011401:Promoter Regions, Genetic; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics*; D013274:Stomach Neoplasms / Q000235:genetics* / Q000473:pathology; D014407:Tumor Cells, Cultured
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; C501486:MLH1 protein, human; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D019853:O(6)-Methylguanine-DNA Methyltransferase; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf; D000070957:MutL Protein Homolog 1