Biomedical subjects

K Shinmura

Publications and source records attributed to K Shinmura.

At least 19 recordsLinked to original sources

PubMed2001

Enhancement of OGG1 protein AP lyase activity by increase of APEX protein.

8-Hydroxyguanine (oh(8)G) is a major form of oxidative DNA damage produced by reactive oxygen species (ROS). The human OGG1 gene encodes a DNA glycosylase that excises oh(8)G from double-stranded DNA. In this study, we investigated a mode of interaction between OGG1 and APEX proteins in the repair of oh(8)G under oxidative stresses. DNA cleavage assay using oh(8)G-containing oligonucleotides showed that the phosphodiester bond on the 3'-side of oh(8)G was cleaved by the AP lyase activity of GST-OGG1 protein and the phosphodiester bond on the 5'-side of oh(8)G was cleaved by the DNA 3'-repair diesterase activity of APEX protein. Gel mobility shift assay showed that the complex of GST-OGG1 protein and oh(8)G-containing oligonucleotides mostly changed into the complex of APEX protein and oligonucleotides by addition of APEX protein into the reaction mixture. We next analyzed alterations in the amount of 8-hydroxydeoxyguanosine (oh(8)dG) in DNA and the levels of OGG1 and APEX expression in HeLa S3 cells treated with 2mM hypochlorous acid, a kind of ROS. An approximately four-fold increase in the amount of oh(8)G was detected by the HPLC-ECD method. Reverse transcriptase-polymerase chain reaction (RT-PCR) and Western blot analyses indicated that the level of APEX expression increased approximately four-fold, whereas the level of OGG1 expression was unchanged. However, in the DNA cleavage assay, the AP lyase activity of GST-OGG1 protein was significantly increased in the presence of a molar excess of APEX protein. These results indicate that, under severe oxidative stresses, OGG1 mRNA is not induced and the amount of OGG1 protein is not remarkably increased, but the activity of OGG1 protein is enhanced by the increase of APEX protein in the cells.

8-Hydroxy-2'-Deoxyguanosine↗

PubMed2001

Somatic mutations and single nucleotide polymorphisms of base excision repair genes involved in the repair of 8-hydroxyguanine in damaged DNA.

To elucidate the involvement of 8-hydroxyguanine (oh(8)G) repair genes in human lung carcinogenesis, 47 lung cancer cell lines and 55 primary lung cancers were examined for somatic mutations and genetic polymorphisms in all coding exons of the MYH and APEX genes, and exon 8 of the OGG1 gene by polymerase chain reaction-single strand conformation polymorphism analysis. In the MYH gene, one missense mutation was detected in a cell line, NCI-H157, whereas no mutations were detected in primary cancers. There were no mutations in the APEX and OGG1 genes in the cell lines or primary cancers. Ten single nucleotide polymorphisms (SNPs) were identified, and seven of them were accompanied by amino acid substitutions. Differences in the oh(8)G repair activities of MYH, APEX and OGG1 proteins due to somatic mutations and SNPs can be involved in human carcinogenesis.

Carbon-Oxygen Lyases↗

PubMed2001

The OGG1 gene encodes a repair enzyme for oxidatively damaged DNA and is involved in human carcinogenesis.

8-Hydroxyguanine (oh8G) is a major base lesion produced by reactive oxygen species. oh8G in DNA causes G:C to T:A transversions and, thus, could be responsible for mutations that lead to carcinogenesis. A human DNA glycosylase/AP lyase encoded by the OGG1 gene has an activity to remove directly oh8G from DNA, and suppresses the mutagenic effect of oh8G. OGG1 protein has a helix-hairpin-helix-GPD motif as a domain for both DNA binding and catalysis, a nuclear localization signal, and a mitochondria targeting signal. Among multiple OGG1 isoforms, OGG1-type la is expressed predominantly in human cells and repairs chromosomal DNA in the nucleus. Inactivation of the OGG1 gene in yeast and mice leads to elevated spontaneous mutation frequency in the cells. The human OGG1 gene maps to chromosome 3p26.2, and allelic deletions of this region occur frequently in a variety of human cancers. Moreover, the OGG1 gene is somatically mutated in some cancer cells and is highly polymorphic among human populations. Repair activities of some mutated and polymorphic OGG1 proteins are lower than those of wild-type OGG1-type la-Ser326 protein and, thus, could be involved in human carcinogenesis.

Amino Acid Sequence↗

PubMed2001

OGG1 protein suppresses G:C-->T:A mutation in a shuttle vector containing 8-hydroxyguanine in human cells.

8-Hydroxyguanine (8-OHG) is an oxidatively damaged mutagenic base which causes G:C-->T:A transversions in DNA. OGG1 was cloned as a human gene encoding a DNA glycosylase that specifically excises 8-OHG from DNA in vitro. However, it was not clear whether OGG1 protein suppresses G:C-->T:A transversions caused by 8-OHG in human cells in vivo. In the present study we have examined the ability of OGG1 protein to suppress G:C-->T:A transversions caused by 8-OHG in human cells by bacterial suppressor tRNA (supF) forward mutation assay using a shuttle vector DNA, pMY189. Introduction of a single 8-OHG residue at position 159 of the supF gene in plasmid pMY189 resulted in a 130-fold increase in mutation frequency compared with untreated plasmid pMY189 after replication in the NCI-H1299 human lung cancer cell line. G:C-->T:A transversions at position 159 were detected in >90% of the supF mutants from the 8-OHG-containing plasmid. The mutation frequency of the 8-OHG-containing plasmid was significantly reduced by overexpression of OGG1 protein in NCI-H1299 cells and, in particular, the occurrence of G:C-->T:A transversion at position 159 in the supF gene was suppressed. Furthermore, frequencies and spectra of mutations of the untreated pMY189 plasmid did not differ significantly with overexpression of OGG1 protein. These results indicate that OGG1 protein has the ability to suppress G:C-->T:A transversions caused by 8-OHG in human cells in vivo.

Base Sequence↗

PubMed2001

Germline p53 mutation in a patient with multiple primary cancers.

We report a case of multiple primary cancers having a germline missense mutation of the p53 gene. The patient was a Japanese female and had a history of five different types of cancers. PCR/direct sequencing analysis revealed the presence of a nucleotide substitution, AGC (Ser) to AGG (Arg), at codon 106 of the p53 gene in DNA from non-cancerous breast tissue. This is the first case of germline p53 mutation at codon 106, and could contribute to establishing correlations between the types and locations of germline p53 mutations and their phenotypical consequences.

Adenocarcinoma↗

PubMed2001

Cyclooxygenase-2 does not mediate late preconditioning induced by activation of adenosine A1 or A3 receptors.

Recent studies have demonstrated that the adenosine A1 receptor agonist 2-chloro-N6-cyclopentyladenosine (CCPA) and the adenosine A3 receptor agonist N6-(3-iodobenzyl)adenosine-5'-N-methyluronamide (IB-MECA) produce a delayed phase of protection against infarction similar to the late phase of ischemic preconditioning (PC). However, the mechanism for adenosine A1 or A3 receptor-induced late PC remains unknown. The goal of this study was to determine whether the delayed cardioprotective effects of adenosine A1 or A3 receptors are mediated by cyclooxygenase-2 (COX-2), which is an obligatory mediator of ischemic PC. We found that COX-2 protein expression (Western blotting) did not increase 24 h after the administration of either CCPA (100 microg/kg iv) or IB-MECA (300 microg/kg iv) compared with controls. To probe the role of constitutive COX-2 expression, conscious rabbits were subjected to 30-min coronary occlusion followed by 72-h reperfusion. Twenty-four hours before the occlusion, the rabbits were pretreated with CCPA (100 microg/kg iv) or IB-MECA (300 microg/kg iv). Both CCPA and IB-MECA resulted in a marked (approximately 47%) reduction in infarct size vs. controls [36.2 +/- 4.0% of the risk region (n = 9), 31.2 +/- 4.7% (n = 9), and 59.5 +/- 3.8% (n = 9), respectively; P < 0.05], similar to that induced by the late phase of ischemic PC [31.8 +/- 3.2% (n = 9)]. The selective COX-2 inhibitor N-(2-[cyclohexyloxy]4-nitrophenyl)methanesulfonamide (NS-398, 5 mg/kg), which abolished the protective effect of ischemic late PC, failed to block the protection of either CCPA or IB-MECA, indicating that COX-2 does not mediate the delayed protection of either CCPA or IB-MECA [CCPA + NS-398, 29.1 +/- 3.4% (n = 7); IB-MECA + NS-398, 34.9 +/- 2.9% (n = 8)]. NS-398 in itself did not affect infarct size [54.9 +/- 3.7% (n = 9)]. Taken together, these results demonstrate that, in contrast to ischemia-induced late PC, the mechanisms of adenosine A1 or A3 receptor-induced late PC is independent of COX-2.

Animals↗

PubMed2000

Adenine excisional repair function of MYH protein on the adenine:8-hydroxyguanine base pair in double-stranded DNA.

Adenine paired with 8-hydroxyguanine (oh(8)G), a major component of oxidative DNA damage, is excised by MYH base excision repair protein in human cells. Since repair activity of MYH protein on an A:G mismatch has also been reported, we compared the repair activity of His(6)-tagged MYH proteins, expressed in Spodoptera frugiperda Sf21 cells, on A:oh(8)G and A:G mismatches by DNA cleavage assay and gel mobility shift assay. We also compared the repair ability of type 1 mitochondrial protein with type 2 nuclear protein, as well as of polymorphic type 1-Q(324) and 2-Q(310) proteins with type 1-H(324) and 2-H(310) proteins by DNA cleavage assay and complementation assay of an Escherichia coli mutM mutY strain. In a reaction buffer with a low salt (0-50 mM) concentration, adenine DNA glycosylase activity of type 2 protein was detected on both A:oh(8)G and A:G substrates. However, in a reaction buffer with a 150 mM salt concentration, similar to physiological conditions, the glycosylase activity on A:G, but not on A:oh(8)G, was extremely reduced and the binding activity of type 2 protein for A:G, but not for A:oh(8)G, was proportionally reduced. The glycosylase activity on A:oh(8)G and the ability to suppress spontaneous mutagenesis were greater for type 2 than type 1 enzyme. There was apparently no difference in the repair activities between the two types of polymorphic MYH proteins. These results indicate that human MYH protein specifically catalyzes the glycosylase reaction on A:oh(8)G under physiological salt concentrations.

Adenine↗

PubMed2000

Cyclooxygenase-2 mediates the cardioprotective effects of the late phase of ischemic preconditioning in conscious rabbits.

We examined the role of cyclooxygenase-2 (COX-2) in the late phase of ischemic preconditioning (PC). A total of 176 conscious rabbits were used. Ischemic PC (six cycles of 4-min coronary occlusions/4-min reperfusions) resulted in a rapid increase in myocardial COX-2 mRNA levels (+231 +/- 64% at 1 h; RNase protection assay) followed 24 h later by an increase in COX-2 protein expression (+216 +/- 79%; Western blotting) and in the myocardial content of prostaglandin (PG)E(2) and 6-keto-PGF(1alpha) (+250 +/- 85% and +259 +/- 107%, respectively; enzyme immunoassay). Administration of two unrelated COX-2 selective inhibitors (NS-398 and celecoxib) 24 h after ischemic PC abolished the ischemic PC-induced increase in tissue levels of PGE(2) and 6-keto-PGF(1alpha). The same doses of NS-398 and celecoxib, given 24 h after ischemic PC, completely blocked the cardioprotective effects of late PC against both myocardial stunning and myocardial infarction, indicating that COX-2 activity is necessary for this phenomenon to occur. Neither NS-398 nor celecoxib lowered PGE(2) or 6-keto-PGF(1alpha) levels in the nonischemic region of preconditioned rabbits, indicating that constitutive COX-1 activity was unaffected. Taken together, these results demonstrate that, in conscious rabbits, up-regulation of COX-2 plays an essential role in the cardioprotection afforded by the late phase of ischemic PC. Therefore, this study identifies COX-2 as a cardioprotective protein. The analysis of arachidonic acid metabolites strongly points to PGE(2) and/or PGI(2) as the likely effectors of COX-2-dependent protection. The recognition that COX-2 mediates the antistunning and antiinfarct effects of late PC impels a reassessment of current views regarding this enzyme, which is generally regarded as detrimental.

6-Ketoprostaglandin F1 alpha↗

PubMed2000

Evidence for an essential role of cyclooxygenase-2 as a mediator of the late phase of ischemic preconditioning in mice.

Recent studies have demonstrated that cyclooxygenase-2 (COX-2) is an essential mediator of the cardioprotective effects of the late phase of ischemic preconditioning (PC) in rabbits. The goal of this study was to determine whether COX-2 also plays an essential role in late PC in the mouse. B6129F2/J mice underwent a 30-min coronary occlusion followed by 24 h of reperfusion. Administration of the COX-2 selective inhibitor, NS-398, 30 min prior to the 30-min occlusion (5 mg/kg i.p.) had no appreciable effect on infarct size compared with untreated controls (58.8 +/- 2.1%, vs. 58.8 +/- 4.3% of the risk region, respectively). When mice were preconditioned with six cycles of 4-min coronary occlusion/4-min reperfusion 24 h prior to the 30-min occlusion, infarct size was markedly reduced (19.3 +/- 3.4%), indicating a late PC effect. The protective effect of late PC was completely abrogated by administration of NS-398 30 min before the 30-min coronary occlusion (67.7 +/- 3.0%), but not by administration of vehicle alone (23.6 +/- 3.7%). These results indicate that COX-2 mediates the late phase of ischemic PC in the mouse and imply that the role of this enzyme in cardioprotection is not species-specific.

Animals↗

PubMed2000

Expression of IFN-gamma in cerebrovascular endothelial cells from aged mice.

Recently, it has become clear that interferon-gamma (IFN-gamma) plays a role in the central nervous system (CNS) as well as in the immune system. However, the reason for the alteration in IFN-gamma production in the brain with aging remains unknown. In this study, we investigated the expression of IFN-gamma in the brain in terms of both mRNA and protein and compared the expression in young adult brain with that in aged mice. The cerebrum and cerebellum were collected from young adult (8-10 weeks old) and aged (24-26 months old) BALB/c mice, and the expressions of IFN-gamma and IFN-gamma receptor-1 (IFNGR-1) mRNA were examined by RT-PCR. Expression of IFN-gamma mRNA was detected in the brains from aged mice but not in those from young adult mice. However, IFNGR-1 mRNA was expressed in the brains from both young adult and aged mice. Moreover, IFN-gamma levels in the cerebrum and cerebellum from aged mice were detectable by ELISA, but IFN-gamma was undetectable in these tissues from young adult mice. To identify the cellular source of IFN-gamma in the brain of aged mice, immunostaining using antimouse IFN-gamma monoclonal antibody (mAb) was done. Immunoreactivity of IFN-gamma appeared to be located in cerebrovascular endothelial cells, including the choroid plexus of the cerebellum from aged mice. Expression of IFN-gamma and IFNGR-1 was also identified in isolated microvessels from brains. These results suggest that IFN-gamma plays a role in age-associated changes.

Aging↗

PubMed2000

Absence of germline CHK2 mutations in familial gastric cancer.

Recently, the CHK2 gene was identified as being a candidate gene responsible for Li-Fraumeni syndrome (LFS). Gastric cancer is often clustered in families with LFS, so it is possible that germline CHK2 mutation is also present in familial gastric cancer (FGC). We therefore defined the genomic structure of the CHK2 gene, designed intronic primers, and searched for germline CHK2 mutations in 25 FGC cases by polymerase chain reaction-single strand conformational polymorphism analysis of the entire coding region. In all of the 25 cases, at least two siblings had histories of gastric cancer. There were no FGC cases that showed germline CHK2 mutations. Thus, it was indicated that germline CHK2 mutations do not contribute to the familial clustering of gastric cancer.

Aged↗

PubMed2000

Catheter-delivered in vivo gene transfer into rat myocardium using the fusigenic liposomal mediated method.

We compared the efficacy of four different in vivo hemagglutinating virus of Japan (HVJ)-liposome gene transfer methods, i.e., direct myocardial injection (i.m.), injection into the left ventricular cavity (LV), infusion at the level of the coronary cusps (CI), or injection into the left ventricular cavity with a balloon catheter blocking aortic flow (LV+B) to transfer beta-galactosidase, FlTC-labeled oligodeoxynucleotide (ODN), and/or luciferase genes into the rat heart. I.m. caused highly efficient gene transfer in the limited area around the injection site, which suggests that i.m. may be a suitable method for targeted treatment of focal lesion. In the LV+B group, all rats had myocardial beta-galactosidase staining and fluorescence of FITC-labeled ODN in the nuclei of cardiac myocytes around the coronary arteries and the vasa vasorum, and some transfected myocytes were observed in the middle of the myocardium without any evidence of injury. In contrast, in the CI group, only half of the animals had myocardial expression of beta-galactosidase. In contrast, fluorescence or luciferase activity was present throughout the left ventricle in the LV+B group. However, the percentage of myocytes that exhibited fluorescence was less than 1% of the total ventricular myocyte population and luciferase activity in the LV+B group was 1.6% of that in the i.m. group. No evidence of luciferase expression was observed in brain, lung, liver, kidney, or testis in either the i.m. or LV+B group. These results suggest that HVJ-liposome gene transfer into the myocardium through the coronary arteries using a balloon-catheter technique is safe and has the potential for causing widespread transgene expression with organ-specificity, although the efficiency of gene transfer should be improved.

Animals↗

PubMed2000

Expression of the OGG1-type 1a (nuclear form) protein in cancerous and non-cancerous human cells.

The human OGG1 gene encodes 8-hydroxyguanine DNA glycosylase. By RT-PCR analysis, five novel type 1 transcripts, in addition to eight known types (OGG1-types 1a to 1c and 2a to 2e), were identified. Among them, only the type 1a isoform contains both a nuclear localization signal and the entire DNA binding motif, suggesting the involvement of type 1a in chromosomal DNA repair. By Western blot analysis using a monoclonal antibody prepared by immunizing the whole type 1a protein, a 39 kDa type 1a protein was detected in lung cancer cell lines and peripheral lymphocytes. The type 1a protein was expressed at a similar level, irrespective of its polymorphic types characterized by distinct repair activity. By an immunocytochemical study, the majority of type 1a protein was localized in the nucleus. These results indicate that OGG1-type 1a protein is involved in the repair of 8-hydroxyguanine in chromosomal double-stranded DNA and constitutively expressed in cancerous and non-cancerous human cells.

3T3 Cells↗

PubMed2000

Clinical factors related to the aqueous levels of vascular endothelial growth factor and hepatocyte growth factor in proliferative diabetic retinopathy.

PURPOSE: To investigate clinical factors related to the aqueous humor levels of vascular endothelial growth factor (VEGF) and hepatocyte growth factor (HGF) in patients with proliferative diabetic retinopathy (PDR). METHODS: Undiluted aqueous humor was obtained during ocular surgery from 46 eyes of 46 patients and the levels of growth factors were measured using enzyme-linked immunosorbent assays. VEGF and HGF levels were compared with the number of photocoagulation. VEGF and HGF levels in patient groups stratified according to the existence of vitreous hemorrhage, retinal detachment, and fibrovascular membrane were analyzed. And clinical parameters associated with the growth factors were determined by multiple regression analysis. RESULTS: The levels of VEGF decreased significantly as the extent of photocoagulation increased and showed significant positive correlation with the existence of vitreous hemorrhage. There was no significant correlation between VEGF levels and the existence of fibrovascular membrane and traction retinal detachment. The levels of HGF also decreased significantly as the extent of photocoagulation increased, but increased significantly when fibrovascular membrane existed. There were no significant correlations between HGF levels and the existence of vitreous hemorrhage and traction retinal detachment. Concerning systemic conditions, each growth factor has no significant correlation with duration and type of diabetes mellitus, the treatment regimen, the control of hemoglobin A1C, and the existence of hypertension or renal dysfunction. CONCLUSION: The therapeutic effect of panretinal photocoagulation on PDR might be partly exerted by reduction of the levels of VEGF and HGF in ocular fluid. Since the clinical parameters associated with VEGF were different from those associated with HGF, these growth factors might influence the progression of retinopathy in different ways.

Adult↗

PubMed1999

Loss of protection by hypoxic preconditioning in aging Fischer 344 rat hearts related to myocardial glycogen content and Na+ imbalance.

OBJECTIVES: The objective of this study was to determine whether hypoxic preconditioning (HP) could lessen the myocardial increase in [Na+]i, thus protecting the aging myocardium against ischemia. BACKGROUND: A decrease in ischemic tolerance with aging is associated with an accelerated increase in [Na+]i during ischemia. Ischemic preconditioning fails to protect the middle-aged and senescent myocardium against ischemia. METHODS: Isolated hearts of young adult (12-week-old), middle-aged (50-week-old) and senescent (100-week-old) Fischer 344 rats were subjected to 25 min of ischemia with or without HP followed by 30 min of reperfusion. Left ventricular (LV) function, myocardial energy metabolites and [Na+]i were measured. RESULTS: In the older groups, the recovery of LV function and high-energy phosphates (HEPs) was lower with an increased release of creatine kinase (CK) during reperfusion than in the young group. The increased [Na+]i at the end of ischemia was greater in the former groups than in the young group. HP decreased myocardial glycogen and lessened the increased [Na+]i in the young group, resulting in an improved recovery of LV function and HEPs, as well as decreased CK release. However, the levels of glycogen before HP in the older groups were higher than in the young group and its levels after HP were similar to that before HP in the young group. HP did not affect the [Na+]i, exacerbated CK release and inhibited the recovery of LV function and HEPs in the older groups. CONCLUSIONS: HP failed to lessen the increased [Na+]i or to protect the aging hearts, probably due to the preexistence of increased glycogen level.

Aging↗

PubMed1999

Parenchyma-preserving hepatectomy in the surgical treatment of hilar cholangiocarcinoma.

BACKGROUND: Although extended hepatic resection has been shown to improve prognosis by increasing the surgical curability rate in hilar cholangiocarcinoma, high surgical morbidity and mortality rates have been reported in patients with obstructive jaundice. Postoperative liver failure after hepatic resection in patients with obstructive jaundice has been shown to depend on the volume of the resected hepatic mass. The aim of this study was to evaluate the results of parenchyma-preserving hepatectomy in a surgical treatment for hilar cholangiocarcinoma. STUDY DESIGN: Ninety-three resected patients with hilar cholangiocarcinoma were included in this retrospective study. The resected patients were stratified into three groups: the extended hepatectomy (EXH) group (n = 66), the parenchyma-preserving hepatectomy (PPH) group (n = 14), and the local resection (LR) group (n = 13). The EXH group had undergone hepatectomy more extensive than hemihepatectomy, the PPH group had undergone hepatectomy less extensive than hemihepatectomy, and the LR group had undergone extrahepatic bile duct resection without hepatic resection. Surgical curability, defined by histologically confirmed negative surgical margins, surgical morbidity and mortality, and survival rates were compared among the three groups. The clinicopathologic factors were studied for prognostic value by univariate and multivariate analyses. RESULTS: Surgical curability of the PPH and EXH groups was better than that of the LR group. Fifty-four percent of patients in the LR group showed positive surgical margins at the hepatic stump of the bile duct, compared with 7% in the PPH group and 20% in the EXH groups (p < 0.01 for each comparison). Surgical morbidity was higher in the EXH group (48%) than in the LR group (8%) and the PPH group (14%) (p < 0.01 and p < 0.05, respectively). Postoperative hyperbilirubinemia occurred more frequently in the EXH group (29%) than in the LR and PPH groups (0% and 0%, respectively, p < 0.05 for each comparison). Survival rates after resection were significantly higher in patients who underwent hepatectomy, including PPH and EXH, than in patients who underwent LR, 29% versus 8% at 5 years, respectively (p < 0.05). But no significant difference in survival was found between the PPH and EXH groups. Univariate and multivariate analyses showed that significant prognostic factors for survival were resected margin, lymph nodal status, and vascular resection. CONCLUSIONS: In conclusion, PPH could obtain a curative resection and improve the outcomes for patients with hilar cholangiocarcinoma that is localized at the hepatic duct confluence who do not require vascular resection. PPH might bring about a beneficial effect in highly selected patients according to extent of cancer and high-risk patients with liver dysfunction.

Bile Duct Neoplasms↗

PubMed1999

Microsatellite instability and K-ras mutations in gastric adenomas, with reference to associated gastric cancers.

Gastric adenomas are often detected in the stomach resected for gastric cancer. Previous investigation have revealed that the prevalence of their malignant transformation is generally low, but the frequent coexistence with carcinoma suggests that they may share some common processes with gastric cancer in tumorigenesis. In contrast to the cumulative information about genetic alterations in gastric cancer, inquiries into the genetic changes of adenoma and coexisting carcinoma in the same individual's stomach are still few. We investigated microsatellite instability (MSI) and K-ras point mutations in codons 12 and 13 in 50 lesions of gastric adenomas in 43 cases, and 31 lesions of gastric cancers that coexisted with these adenomas. In gastric adenomas, we found seven lesions (14.0%) to have microsatellite instability (MSI) at one or more loci, and most of them (six cases) had MSI at only one locus and were not associated with alterations in presumable target molecules. MSI was detected more frequently (11/31, 35.5%) and more extensively (five lesions at multiple loci) in accompanying gastric carcinomas. The prevalence of MSI in adenomas was more frequently found in those with synchronous gastric cancer (6/37, 16.2%, vs. 1/13, 7.6%) than without, and gastric adenoma accompanied by gastric cancer with multiple MSI tended to have MSI more frequently than that accompanied by cancer without MSI (4/5, 80%, vs. 1/24, 4.2%; p = 0. 01). In at least some individuals, MSI appears to represent one step in the pathway of gastric tumorigenesis, shared by adenoma and carcinoma. We found K-ras gene alteration in 8 lesions (16.0%) out of 50 gastric flat adenomas and no difference in its prevalence between adenoma with or without cancer. Only one gastric cancer, which had adenoma without K-ras mutation, had K-ras codon 12 mutation. Adenomas with a higher grade of atypia (p < 0.05) more frequently carried K-ras point mutation, which is consistent with the situation in colorectal adenoma. We conclude that MSI, not K-ras mutation, is a shared genetic alteration in adenoma and carcinoma of the individual stomach.

Adenoma↗

PubMed1999

Familial gastric cancer: clinicopathological characteristics, RER phenotype and germline p53 and E-cadherin mutations.

Gastric cancer frequently occurs in family members with hereditary non-polyposis colorectal cancer (HNPCC) and Li-Fraumeni syndrome (LFS) and germline E-cadherin mutations were recently identified in a subset of familial gastric cancers. Thus, families with an aggregation of gastric cancers were recruited by reviewing the genealogical trees of 3632 patients with gastric cancer. The criteria for recruiting such families were the following: at least three relatives should have gastric cancer and one of them should be a first degree relative of the other two; at least two successive generations should be affected; in one of the relatives gastric cancer should be diagnosed before age 50. Thirty-one cases (0.9%) fitted all three of these criteria. There were only gastric cancer patients in 18 of the 31 families and there were no families that fitted clinical criteria of HNPCC or LFS. Paraffin-embedded tissues were available in 29 probands and DNA was successfully isolated for molecular analyses in 13 probands. RER phenotype was detected in three (23%) cases, whereas germline p53 mutations were detected in none of 13 cases. A germline E-cadherin mutation was detected in one of three diffuse types and none of 10 intestinal types, however, a mutation resulting in the replacement of Gly by Val was detected in the precursor sequence. Thus, although familial clustering of gastric cancer occurs in approximately 1% of gastric cancer patients, germline mutations of the DNA mismatch repair, p53 and E-cadherin genes do not significantly contribute to such a clustering.

Adolescent↗