Abstract

Aim: Inactivation of tumor-related genes by promoter hypermethylation is a common epigenetic event occurring in the development of a variety of tumors. In this study, we investigated in primary uveal melanoma the status of promoter methylation of genes thought to be involved in tumor development, such as p16, TIMP3, RASSF1, RARB, FHIT, hTERT and APC.

Materials and methods: Gene promoter methylation was studied by methylation-sensitive single-strand conformation analysis (MS-SSCA) and dot blot assay (MS-DBA) in a series of 23 primary uveal melanomas. All DNA samples were obtained from paraffin-embedded formalin-fixed tissue blocks.

Results: In our series of primary uveal melanoma, hTERT promoter methylation was found with a relatively high frequency (52%). Promoter methytion of p16, TIMP3, RASSF1, RARB, FHIT and APC was an infrequent event. For none of these genes promoter methylation exceeded 15% of tumor samples and for some genes, no methylation was found at all (FHIT and APC). Furthermore, absence of promoter methylation was noticed in 39% (9/23) of cases. In only 22% (5/23) of cases, hypermethylation of at least 2 promoters was observed.

Conclusions: Promoter methylation of hTERT is a regularly occurring event in uveal melanoma. Hypermethylation of the other studied genes does not seem to be a crucial element in the development of this tumor. As APC, RASSF1 and RARB promoter methylation has been frequently observed in cutaneous melanoma, our results tend to demonstrate that different epigenetic events occur in the development of cutaneous and uveal melanoma.