Amplification of cyclin D1 and MDM-2 in oesophageal carcinoma.

ABSTRACT

AIMS: This study investigated amplification of the cyclin D1 and MDM-2 genes, and overexpression of the cyclin D1 gene product, in oesophageal carcinoma. METHODS: Paired tumour and normal DNA samples from 26 oesophageal adenocarcinomas and 19 squamous cell carcinomas were analysed by Southern blotting with specific DNA probes for cyclin D1 and MDM-2, and for a control gene (alpha-lactalbumin). The cyclin D1 and MDM-2 gene copy numbers were calculated for each tumour. Expression of the cyclin D1 gene was assessed by immunohistochemical analysis of its protein product. RESULTS: Cyclin D1 gene amplification (by a factor of between two and six) was identified in seven tumours (16%). MDM-2 gene amplification (by a factor of between two and 11) was identified in 10 tumours (22%). Overexpression of cyclin D1 protein was identified in eight tumours and was significantly associated with gene amplification (P=0.04; Fisher's exact test), and with early T stage (P=0.01; Fisher's exact test). CONCLUSIONS: Cyclin D1 and MDM-2 amplification and cyclin D1 overexpression occur, although infrequently, in the development of oesophageal carcinoma. Cyclin D1 overexpression may influence tumour behaviour, causing the disease to present at an earlier T stage. The mechanism for this effect is unclear, and warrants further investigation.