Epigenetic inactivation of RASSF1a in uveal melanoma.

PURPOSE The RAS association domain family 1 (RASSF1) gene is a tumor-suppressor gene located on chromosome 3p21.3. The alternative transcript (RASSF1a) has been shown to be inactivated by hypermethylation in several human malignancies, including breast, prostate, and lung cancer, and in cutaneous melanoma. The purpose of this study was to evaluate the methylation status of RASSF1a in human uveal melanoma. METHODS The methylation status of the RASSF1a promoter region was analyzed using PCR in combination with melting curve analysis, sequencing, and restriction enzyme analysis. Eleven human uveal melanoma cell lines, normal melanocytes, 39 archival frozen tumor specimens, and a metastatic lesion of untreated primary uveal melanoma were studied. In addition, whether RASSF1a methylation correlates with patient survival and development of metastatic disease was investigated. RESULTS RASSF1a promoter methylation was detected in 10 of the 11 (91%) cell lines, in 19 of the 38 (50%) patients with primary uveal melanoma and in the metastatic lesion. A positive correlation was found between RASSF1a promoter methylation and development of metastatic disease (P = 0.041). A correlation with disease-free survival could not be established, but a positive trend was observed (P = 0.063). CONCLUSIONS These data show that RASSF1a methylation is a common epigenetic event in uveal melanoma development, potentially of clinical relevance. The presence of a methylated RASSF1a promoter region might therefore serve as a tumor marker and as a possible target for therapeutic intervention.