Dinucleotide repeat polymorphism at the D22S351 locus

Genetic alterations in gastric cancers from British patients

Twenty-six gastric carcinoma and matching normal tissue DNAs, which had previously been analyzed for alterations of the APC (adenomatous polyposis coli) and MCC (mutated in colorectal cancer) genes were further investigated for the following genetic alterations: mutation and loss of heterozygosity (LOH) of the p53 gene, replication error (RER) and LOH at 12 microsatellite repeat loci, and mutation of the hMSH2 gene. In addition, 9 of the 26 gastric carcinomas were analyzed for genetic alterations using comparative genomic hybridization (CGH). Somatic mutations of the p53 gene were found to be frequent being detected in 31% of gastric carcinomas while LOH at the p53 locus was observed in 37.5% of informative cases. Loss of wild type p53 allele was detected in the majority (7 of 8) tumors found to be harboring a mutation. In the hMSH2 gene, an intronic 4 base pair insertion at 31 base pairs upstream of the beginning of exon 13 was detected in both tumor and normal tissue from one gastric carcinoma case. RER was detected in 11.5% of gastric carcinomas, at one or more microsatellite repeat loci. Of the 12 microsatellite repeat loci analyzed LOH was most frequently observed at D22S351 (30% informative cases) suggesting that a tumor suppressor gene on 22q may be important in gastric carcinogenesis. In support of this, CGH analysis carried out on 9 of the gastric carcinomas identified loss of chromosome 22 in 5 of these tumors.

A molecular and FISH approach to determining karyotype and phenotype correlations in six patients with supernumerary marker(22) chromosomes

In a cytogenetic, molecular, and clinical study of patients with autosomal supernumerary marker chromosomes (SMC), 6 out of 72 (8.3%) were shown by fluorescence in situ hybridisation (FISH) to be derived from chromosome 22. PCR microsatellite analysis and FISH using primers and cosmids from proximal 22q showed 3 of the 6 to contain euchromatin. The first, a de novo nonmosaic bisatellited, dicentric SMC, was acsertained in a patient with cat eye syndrome and Duane anomaly. Microsatellite analysis showed the SMC was maternal in origin with euchromatin extending to D22S427, i.e., proximal to the DiGeorge syndrome critical region (DGSCR). The second, a nonmosaic bisatellited, dicentric marker, was found in a child with severe hypotonia and developmental delay and had been inherited from the patient's phenotypically normal father. FISH showed the SMC to contain euchromatin extending into the DGSCR. The third, a de novo SMC, was ascertained antenatally and was shown to contain 22q euchromatin extending distal to the DGSCR. The 19-week terminated fetus was phenotypically normal at autopsy. Two of the three SMC(22)s not containing detectable proximal 22q euchromatin were ascertained coincidentally in phenotypically normal individuals, whereas the third, the only mosaic with a minority euploid cell line, was found in a patient with mild developmental delay. These results suggest that SMC(22)s devoid of proximal 22q euchromatin are not associated with adverse phenotypic effects whereas SMC(22)s containing euchromatin may be found in individuals with phenotypes ranging from cat eye syndrome to normal.

Identification of allelic losses in benign, borderline, and invasive epithelial ovarian tumors and correlation with clinical outcome

BACKGROUND

The somatogenetic alterations that lead to the development of benign adenomas, borderline tumors, and invasive ovarian carcinomas are not well understood. This study investigated allelic losses in these three types of ovarian tumors.

METHODS

Twelve genetic regions on chromosomes 2q, 5q, 6p, 6q, 9p, 11q, 17p, 17q, 18q, and 22q were analyzed by polymerase chain reaction for loss of heterozygosity (LOH). The study was performed on formalin fixed, paraffin embedded tissue samples from 72 invasive ovarian carcinomas, 35 ovarian tumors of borderline malignancy, and 25 benign ovarian adenomas.

RESULTS

LOH was found in only 8% of the analyzed adenomas (at 2q21 and 17p13) and 11% of the borderline tumors (at 2q21, 5q21, 6p21, 17p13, and 17q21). Allelic losses were noted for 77.7% of all of the invasive carcinomas analyzed. The frequency of LOH was 56% at a locus near 17p13 (TP53) and 40.5% at 17q21 (BRCA1). LOH was observed in 30.4% of informative cases at 5q21 and in 21.4% at chromosome 18q21. The chromosomal regions 2q21-22 and 9p21 had deletions at frequencies of 32.4% and 25%, respectively. International Federation of Gynecology and Obstetrics stage and the presence of LOH correlated significantly with survival but were not independent predictors of survival. Serous subtypes of invasive carcinoma were significantly more prone to deletions than nonserous tumors.

CONCLUSIONS

The results of this study suggest that LOH occurs only occasionally in adenomas and borderline tumors, whereas it is frequently observed in invasive ovarian carcinomas. Therefore, other genetic events seem to be involved in early ovarian tumor development. However, the presence of multiple allelic losses is an indicator of higher stages of invasive carcinoma.