Genetic rearrangements in sporadic and familial gastric carcinomas detected with microsatellite markers.

Ten gastric carcinomas were studied for loss of heterozygosity by analysis of 21 microsatellite markers from 14 different chromosomes. Four patients had a family history of gastro-intestinal cancer, and six tumours were considered sporadic. We also studied a new mechanism in tumourigenesis recently reported in hereditary non polyposis colon cancer, a defect in mismatch repair that is seen as gain of new bands by the use of dinucleotide repeat markers. Loss of heterozygosity was detected with two markers in one primary tumour and with the majority of markers in one metastasis from a sporadic gastric tumour. Gain of microsatellite bands was seen in one tumour from a gene carrier in a family with hereditary non-polyposis colon cancer and in one sporadic tumour. Two tumours from patients with a family history of gastric cancer showed no rearrangements. Our results suggest that different types of genes are involved in initiation and progression of gastric cancer in sporadic and familial gastric cancer.

High expression of the EGFR in fibroadenomas compared to breast carcinomas.

The epidermal growth factor receptor and its ligands have been implicated as being involved in normal mammary development and breast cancer genesis. Northern blotting was used to assay the mRNA levels of the epidermal growth factor receptor and three of its ligands: the epidermal growth factor, the transforming growth factor alpha and the Amphiregulin in 16 primary carcinomas, 2 metastases and 5 fibroadenomas. In addition, the mRNA levels of the other members of the epidermal growth factor receptor family, erbB2 and erbB3 were also analysed. We found limited expression in the breast carcinomas while all the fibroadenomas showed expression at high levels. Therefore we suggest that the epidermal growth factor receptor plays an important role in the development of fibroadenomas. The erbB2 and erbB3 were more strongly expressed than the epidermal growth factor receptor in the primary carcinomas. This suggests that they could be of importance in breast carcinogenesis.

Loss of heterozygosity studies in tumors from families with breast-ovarian cancer syndrome.

A gene (BRCA1) predisposing for familial breast and ovarian cancer has been mapped to chromosome band 17q12-21. Based on the observation that ovarian tumors from families with breast and ovarian cancer lose the wild-type allele in the region for the BRCA1 locus, it has been suggested that the gene functions as a tumor suppressor gene. We have studied chromosomal deletions in the BRCA1 region in seven breast tumors, three ovarian tumors, one bladder cancer, and one colon cancer from patients in six families with breast-ovarian cancer, in order to test the hypothesis of the tumor suppressor mechanism at this locus. We have found a low frequency of loss of heterozygosity at this region, and our results do not support the idea that BRCA1 is a tumor suppressor gene. Alternatively, the disease segregating in these families is linked to one or more different loci.