Epigenetic and expression analysis of TRAIL-R2 and BCL2: on the TRAIL to knowledge of apoptosis in ovarian tumors

Abstract

This study assesses TRAIL-R2 (TNF-related apoptosis-inducing ligand receptor 2) and BCL2 (B cell CLL/lymphoma 2) expression as well as CpG island methylation within the TRAIL-R2 promoter in ovarian serous tumors and primary and metastatic serous EOC (epithelial ovarian cancer). RNA and DNA were obtained from women with normal ovarian tissues (n = 18), ovarian serous cystadenoma tumors (n = 11) and serous EOC (n = 16) using Trizol®. Quantitative PCR was performed to quantify the relative levels of TRAIL-R2 and BCL2. The methylation frequency of the TRAIL-R3 promoter was assessed using a methylation-specific PCR assay after DNA bisulfite conversion. Differences between the groups were evaluated using the χ (2), Mann-Whitney U or Kruskal-Wallis tests, as indicated. We identified TRAIL-R2 and BCL2 mRNA expressed in all ovarian tumor groups, and there were significant differences between the groups. Both genes had low expression levels in ovarian serous cystadenoma and primary EOC tumors when compared with metastatic EOC. Methylation of the TRAIL-R2 promoter was frequently observed in all groups; however, there were no statistically significant associations. Primary EOC is associated with lower TRAIL-R2 and BCL2 expression levels, while metastatic EOC is associated with higher expression of these genes. Promoter DNA methylation was not related to this finding, suggesting there are other mechanisms involved in transcriptional control.