MYH, OGG1, MTH1, and APC alterations involved in the colorectal tumorigenesis of Korean patients with multiple adenomas

This study was done to characterize base excision repair (BER) genes and adenomatous polyposis coli (APC) alterations in the tumorigenesis of multiple colorectal adenomas in Korean patients. In total, 217 adenomas (mean number = 10) and 117 cancers were available from 143 patients. The heterozygous genotype of OGG1 c.1-18G>T was closely associated with multiple adenoma families (P < 0.001), while MYH A359V mutation exhibited a tendency (P = 0.053). MYH R170G mutation was exclusively identified in one patient. The G:C>T:A transversion or attenuated familial adenomatous polyposis (AFAP) mutations of APC was identified in the specific genotypes of BER variants. Tubular adenomas or adenomas with none-to-mild dysplasia were significantly associated with polymorphic genotypes of OGG1 IVS4-15 and S326C. In addition, large and pedunculated adenomas were more frequent in patients with G:C>T:A transversion and AFAP mutations of APC, respectively. However, BER variants were not associated with mismatch repair or altered p53 protein expression. Conclusively, two novel mutations of MYH and a novel OGG1 polymorphism seemed to be associated with multiple colorectal adenomas in Korean families, differing from those in other ethnic groups. Some BER variants involved in specific APC mutations are associated with characteristics of histogenesis other than altered mismatch repair or p53 pathway.

Experimental radioimmunoguided surgery for peritoneal metastases of gastric cancer using anticarcinoembryonic antigen-specific T84.66 F(ab')2

PURPOSE

In gastric cancer, peritoneal dissemination is the most frequent cause of the noncurative resection and recurrence after curative resection. We therefore evaluated the feasibility of radioimmunoguided surgery (RIGS) in the treatment of peritoneal metastases of gastric cancer and the use of anti-CEA-specific T84.66 F(ab')2 as an efficient immune agent.

METHODS

Two human gastric cancer cell lines, MKN45 and RF48, were intraperitoneally xenografted into nude mice, which were later injected with 125I-labeled T84.66 F(ab')2. Peritoneal tumors were localized by RIGS 5 days after antibody injection. The minimum number of cells detected by a gamma probe was assayed by in vitro tumor cell localization.

RESULTS

We observed 37 peritoneal metastases: 8 invisible (long diameter, <1 mm), 6 small (1- < 5 mm), and 23 large (> or =5 mm) tumors. The accuracy, sensitivity and specificity of RIGS in detecting peritoneal metastasis were 82% (69/84), 76% (28/37), and 87% (41/47), respectively. RIGS accuracy did not differ with respect to tumor diameter. Mean labeling indices over minimal and maximal normal counts were 6.1+/-1.2 (mean +/- SEM) and 4.7+/-1, respectively. Mean scores of CEA immunostaining and silver grains in tumors were significantly higher than those in the nontumor-bearing peritoneum (P < 0.001). There was a close correlation among radioactivity, immunostaining and microautoradiography (P < 0.001-0.005). We observed six false-positive and nine false-negatives which may have been due to high blood background and negative radioimmune reactivity, respectively.

CONCLUSIONS

125I-labeled T84.66 F(ab')2 efficiently targeted peritoneally disseminated gastric cancer cells, suggesting that RIGS using this immune agent may accurately detect occult peritoneal metastases in patients with gastric cancer.

Genotyping possible polymorphic variants of human mismatch repair genes in healthy Korean individuals and sporadic colorectal cancer patients

The genotypic consequences of numerous single-nucleotide variants in human mismatch repair genes are mostly undetermined. We examined 27 reported single-nucleotide variants, rarely or ambiguously verified in a population-based study, to identify single-nucleotide polymorphisms (SNPs), haplotypes, and the genotype-phenotype association in Korean populations of 330 healthy individuals, 107 sporadic colorectal cancer patients, and 107 of their first-degree relatives. Real-time PCR 5'-nuclease assays (TaqMan) MGB assay) were used to determine 24 single-nucleotide variants, and restriction fragment length polymorphism (RFLP) assays were used to determine 3 variants. Of these 27 variants, 4 (hMSH2 gIVS12-6, hMLH1 655, hMLH1 1151, and hMSH2 1168, in descending order) were identified as SNPs occurring in 4.5 to 53.1% of healthy individuals, with polymorphism levels of 0.023-0.3 (mean, 0.092). East Asian populations had an ethnic predilection for the hMLH1 1151 SNP. The genotype distribution for all four SNPs showed no association with sporadic colorectal cancer. Twenty-three variants were not identified in the Korean population, suggesting that fifteen of these variants are colorectal cancer-related mutations and eight are SNPs. Two haplotype patterns existed exclusively, but with rare frequency, in sporadic colorectal cancer patients. The hMLH1 655 allele was closely correlated with hMLH1 protein expression (P = 0.02), but none of the four SNPs was associated with clinicopathologic variables. Among the 27 single nucleotide variants of mismatch repair genes, 12 were suggestive of nonfunctional SNPs and 15 may be colorectal cancer-related mutations. Further verification in other ethnic groups may provide the genotypic and phenotypic significance of single nucleotide variants found in mismatch repair genes.

Genotyping possible polymorphic variants of human mismatch repair genes in healthy Korean individuals and sporadic colorectal cancer patients

The genotypic consequences of numerous single-nucleotide variants in human mismatch repair genes are mostly undetermined. We examined 27 reported single-nucleotide variants, rarely or ambiguously verified in a population-based study, to identify single-nucleotide polymorphisms (SNPs), haplotypes, and the genotype-phenotype association in Korean populations of 330 healthy individuals, 107 sporadic colorectal cancer patients, and 107 of their first-degree relatives. Real-time PCR 5'-nuclease assays (TaqMan) MGB assay) were used to determine 24 single-nucleotide variants, and restriction fragment length polymorphism (RFLP) assays were used to determine 3 variants. Of these 27 variants, 4 (hMSH2 gIVS12-6, hMLH1 655, hMLH1 1151, and hMSH2 1168, in descending order) were identified as SNPs occurring in 4.5 to 53.1% of healthy individuals, with polymorphism levels of 0.023-0.3 (mean, 0.092). East Asian populations had an ethnic predilection for the hMLH1 1151 SNP. The genotype distribution for all four SNPs showed no association with sporadic colorectal cancer. Twenty-three variants were not identified in the Korean population, suggesting that fifteen of these variants are colorectal cancer-related mutations and eight are SNPs. Two haplotype patterns existed exclusively, but with rare frequency, in sporadic colorectal cancer patients. The hMLH1 655 allele was closely correlated with hMLH1 protein expression (P = 0.02), but none of the four SNPs was associated with clinicopathologic variables. Among the 27 single nucleotide variants of mismatch repair genes, 12 were suggestive of nonfunctional SNPs and 15 may be colorectal cancer-related mutations. Further verification in other ethnic groups may provide the genotypic and phenotypic significance of single nucleotide variants found in mismatch repair genes.

Characterization of Mutator Phenotype in Familial Colorectal Cancer Patients Not Fulfilling Amsterdam Criteria

PURPOSE

Although the mutator phenotype, including genetic and epigenetic alterations of the mismatch repair (MMR) system, seems to be pronounced in familial colorectal cancer, there have been few integrative studies comprising the entire mutator pathway. This study was done to identify the entire mutator pathway determining risk factors in patients with familial colorectal cancer not fulfilling the Amsterdam criteria.

EXPERIMENTAL DESIGN

We consecutively recruited 134 colorectal cancer patients with a family history of accompanying cancers. Patients with hereditary nonpolyposis colorectal cancer meeting the Amsterdam criteria, familial adenomatous polyposis, or those receiving preoperative radiotherapy were excluded. Mutator phenotype was assessed by assaying microsatellite instability (MSI) at 24 markers, hMLH1-promoter methylation, mutations at MMR genes (hMLH1, hMSH2, hMSH6, and hPMS2), and immune staining of MMR proteins (hMLH1, hMSH2, hMSH6, hPMS1, and hPMS2).

RESULTS

Of the 208 cancers in first-degree and/or second-degree relatives of patients, colorectal and gastric cancers (81%) were most common. Of the 134 proband colorectal cancers, 23 (17%) were MSI in high level, and 32 (24%) were MSI in low level. MMR alterations, including known polymorphism and splicing substitution, were identified in eight patients (6%). Twenty-eight tumors with mutator phenotype were further identified by hMLH1-promoter methylation and/or loss of MMR protein expression. In 51 tumors (38%), mutator phenotype was associated with right-sided colon cancer (P < 0.001) and younger age at onset (P=0.032), but the number of patients with a mutator phenotype did not differ with respect to inheritance patterns of accompanying cancers, either successive or horizontal transmission (P=0.815). Familial impact value, which differentially associated the degree of relatives with all accompanying cancers, effectively discriminated MSI in high level from microsatellite stable/MSI in low level tumors.

CONCLUSION

Familial colorectal cancer may be associated with multiple occurrences of colorectal or accompanying cancers inherited by dominant or recessive transmission. MMR gene mutations, however, are less associated with mutator phenotype in familial colorectal cancer.

Efficient targeting of gastric cancer cells using radiolabeled anti-carcinoembryonic antigen-specific T84.66 fragments in experimental radioimmunoguided surgery

BACKGROUND

Radioimmunoguided surgery (RIGS) appears as an efficient tool for accurate tumor detection up to the level of micrometastases by detecting radiolabeled antibody-bound tumor cells during operation. Anti-CEA-specific T84.66 fragments were examined as to whether they efficiently detected gastric cancer cells in experimental RIGS. T84.66, anti-CEA-specific antibody, has widely been used as an immune carrier in the preclinical and clinical trials of radioimmunotherapy and radioimmunoscintiscan.

MATERIALS AND METHODS

Fifty-one tumors from two human gastric carcinoma cell lines with profuse (MKN45) and low (RF48) CEA expression were successfully implanted subcutaneously in the backs of 32 nude mice. Tumors were localized after 125I-labeled T84.66 F(ab')2 and Fab' injection.

RESULTS

The radioactivity of F(ab')2-pretreated mice was greater than that of Fab'-pretreated in all organs and tumors (p<0.001-0.035). Localization indices of the tumor in various organs revealed 7.4 to 32.5 in F(ab')2-pretreated and 1 to 7.1 in Fab'-pretreated mice. Silver grains and immune staining were predominantly distributed in tumor cells regardless of fragment types and cell lines. There was no false-negative evaluation of tumor in F(ab')2-pretreated mice. Sensitivity and specificity of tumor localization by RIGS were the highest in the F(ab')2-pretreated mice (95% for MKN45- and 82% for RF46-xenografted mice) and the least in the Fab'-pretreated mice (66% for MKN45- and 67% for RF46-xenografted mice). In all organs, three quarters of the false-positive evaluations occurred from silver grains as radioimmune complex or dissociated nuclides in the circulation that can be eliminated with time.

CONCLUSION

Anti-CEA-specific T84.66 fragments achieved a great affinity and avidity with accurate localization of gastric carcinoma in experimental RIGS.