Homozygous deletion map at 18q21.1 in pancreatic cancer.

Absolute genetic differences between neoplastic and nonneoplastic cells can be discerned at sites of homozygous deletions. These deletions are of critical interest because they might be useful in the identification of defective biochemical pathways in neoplastic cells, and subsequently for the development of new treatment strategies in human cancer. We identified an area at 18q21.1 involved by homozygous deletions in 30% of pancreatic carcinomas. To characterize the homozygous deletions, we constructed a detailed physical map of nearly 2 Mb, containing yeast artificial chromosomes, P1-derived artificial chromosomes, cosmids and 24 sequence-tagged sites. The homozygously deleted are contained a new candidate tumor-suppressor gene (DPC4). To date, 23 (64%) of 35 pancreatic carcinomas carry at least one homozygous deletion at a published locus. The study of the total gene content of these loci, facilitated by the sequence-tagged site markers and maps of these regions, should help to reveal the absolute biochemical differences between neoplastic and nonneoplastic cells for a common human tumor.