Resected pancreatic ductal and ampullary adenocarcinomas (n = 50) were analyzed for loss of heterozygosity (LOH) at 15 markers including 5q(APC), 6q(TBSP2), 9p(p16), 10q(PTEN), 12q(MDM2), 17p(TP53), and 18q(DCC/SMAD4).
The presence of chromosome 18q loss and DPC4 mutations in appendiceal adenocarcinomas suggests involvement of DPC4 and nearby genes on chromosome 18q (DCC and/or JV-18) in the pathogenesis of appendiceal adenocarcinomas.
These results suggest that LOH at the sites of the DCC, adenomatous polyposis coli (APC), and TP53 tumor suppressor genes occur before the development of adenocarcinoma in Barrett's esophagus, and so merit further study as potential biomarkers of neoplastic progression in patients with Barrett's esophagus undergoing endoscopic and histological surveillance.
Four of the five tumors with associated adenocarcinoma showed LOH of the DCC gene; in three of these four tumors, the PDNC and adenomatous components showed LOH of the same allele.
In addition to the p53 gene on 17p and the DCC gene on 18q, which are known to be frequently deleted in differentiated adenocarcinomas of the stomach, other unknown tumour suppressor genes on the above-mentioned chromosomes may also be inactivated.
Progression to the adenocarcinoma phenotype was shown to involve a specific chromosome 1 rearrangement, loss of both normal copies of chromosome 18 (although DCC gene sequences were retained), loss of the remaining wild type allele of k-ras resulting in homozygosity for the k-ras codon 12 mutation and increased cellular p53 protein as detected by SDS-PAGE Western blotting.
We examined 72 esophageal tumors (46 squamous cell carcinomas and 26 adenocarcinomas) for loss of heterozygosity at the p53, Rb, APC, MCC, and DCC loci.