The evolution of loss of heterozygosity on chromosome 17 during the progression to barrett's adenocarcinoma involves a unique combination of target sites in individual specimens.

We have previously identified thirteen common minimally deleted regions (MRs) on chromosome 17 in twelve Barrett's esophageal adenocarcinoma (BOA) specimens using 41 precisely mapped microsatellite markers (Dunn et al., Oncogene, 17: 987-993, 1999). The aim of the present study has been to identify the earliest sites of loss on this chromosome that arise and persist during the progression to BOA. This has been undertaken by the analysis of multiple carefully microdissected tissue samples from each of five esophagectomy specimens, several of which contained identifiable premalignant tissue. Our data demonstrate a stepwise accumulation of loss in each analyzed specimen, consistent with a single clonal pathway in four specimens and several coexisting pathways in one specimen. Several clonal anomalies (loss preceding heterozygosity and variable intrasample degrees of loss at different markers) were also observed. Within extensively deleted regions of the tumor (seen in three specimens), small deletions were detected in premalignant tissue, predominantly at the site of our identified MRs, and these losses were seen to expand and merge during the progression to BOA. Clonal losses at MRs were first detected in tissue showing early changes histologically, including Barrett's intestinal metaplasia and intermediate-grade dysplasia. Our results provide further support for many of the MRs we have previously identified, thereby adding to evidence for the existence of multiple novel cancer-associated genes on chromosome 17 involved in the development of BOA.

Enteroscopy.

It is now more than 25 years since small bowel enteroscopy (SBE) was first described. For several reasons, this technique developed more slowly than other more usual forms of endoscopy. First, small bowel disease is relatively rare in comparison with other gastrointestinal diseases. Also, there was lack of initial design agreement, and three different types of enteroscopes were developed within a short time of each other, two of which (push-type and sonde) are now available commercially. Finally, commercial interests of the manufacturers of endoscopes were mainly focused on the more conventional, large volume markets. In the last few years, specifically designed modern small bowel enteroscopes have become available and, in centers that have access to them, they have superseded attempts at SBE using adult or pediatric colonoscopes. There are now clear indications for SBE, such as: the investigation of obscure causes of bleeding and anemia; malabsorption; clarification of x-ray abnormalities; and, increasingly, the application of therapeutic endoscopy to lesions within the small bowel. Problem areas remain, but with advancing technology and more professional interest in this area, these will be addressed during the next few years.