However in the bordering metaplastic tissues of six out of 10 patients with adenocarcinoma and in dysplastic tissue from two other patients, MT concentrations were on average two-fold higher than those in normal oesophagus. The levels of MT in adenocarcinoma were unremarkable and there was no obvious association between the these MT content and the histological grading. Table 1 Characteristics of patients, histological diagnosis and metallothionein levels in normal, transitional and cancerous oesophageal tissue Metallothionein concentrations were increased in Barrett’s epithelium in 17 out of 20 patients by an average of 108% (Table 2). The mean MT concentration in normal and Barrett’s epithelium was 204��22 (pmol Cd boundmg?1 protein; mean��s.d.) and 411��68, respectively.

The difference between MT concentrations in normal and Barrett’s epithelium was highly significant (P<0.004). There was no association between the MT levels in Barrett's epithelium and the histological diagnosis of inflammation, metaplasia or dysplasia. Table 2 Characteristics of patients, histological diagnosis and metallothionein levels in normal and Barett's epithelium DISCUSSION It has been argued that in Barrett's oesophagus there is a large intra- and interobserver variation in the reporting of various grade dysplasia with inflammatory atypia making the diagnosis problematic. Thus it can be difficult to monitor the progression of oesophagitis to dysplasia in order to detect cancer at a curable stage (Ortiz-Hidalgo et al, 1998).

This has led to the search for new objective indicators which may complement and help reduce the observer variability with histological diagnosis. MT is a potential marker of carcinogenesis and its expression in human cancers can be up- or down-regulated (Cherian et al, 1994). Few studies have focused on the expression of MT in human oesophageal tumours and this is the first to quantitatively measure the concentration of MT in human adenocarcinoma of the oesophagus and in Barrett’s epithelium, which is generally considered to be the premalignant lesion, although the primary cells leading to adenocarcinoma have not been identified. In one study, in situ hybridisation with MT DNA probes and immunochemistry was used to determine MT mRNA and MT protein expression in resected oesophageal tissue from patients with squamous cell carcinoma.

It was concluded that MT expression was a potential marker of the proliferative and metastatic behaviour of this cancer (Hishikawa et al, 1997, 1999). Here we demonstrate that MT expression was not increased above matched normal-appearing oesophagus in 10 patients we investigated with AV-951 adenocarcinoma. In each case, there was histological confirmation that the adenocarcinoma arose from columnar lined Barrett’s mucosa.