P13.01 TERTpromoter methylation is significantly associated withTERTupregulation and tumor progression in pituitary adenomas

Abstract

Abstract BACKGROUND Activation of telomerase plays a critical role in tumor development. Somatic alterations in the promoter of the telomerase reverse transcriptase (TERT) gene are a major mechanism of upregulating telomerase. Several mechanisms have been associated with TERT abnormalities, including TERT promoter mutations or methylation. Mutations in the TERT promoter have been observed in a subset of brain tumors, especially in adult gliomas. In pituitary adenomas (PAs), however, TERT abnormalities are not fully understood. The present study aimed to investigate not only mutational but also methylation status changes in the TERT promoter in PAs and to analyze their correlations with clinical variables. MATERIAL AND METHODS We retrospectively studied 70 PAs consisting of 53 primary and 17 recurrent samples. Clinical data, including age at surgery, sex, tumor size, tumor subtype, resection rate, presence or absence of postoperative irradiation, and progression-free survival (PFS), were obtained from medical records. First, we investigated TERT promoter hotspot mutations via Sanger sequencing. Next, we quantified the methylation status of the TERT promoter using methylation-sensitive high-resolution melting analysis (MS-HRM). Finally, we investigated TERT mRNA expression levels using real-time quantitative PCR. Fisher’s exact test was applied to evaluate the statistical significance between TERT promoter methylation status and tumor recurrence. PFS was calculated using Kaplan-Meier estimates and compared between methylated with ummethylated PAs with the log-rank test. The correlation between TERT promoter methylation status and mRNA levels was analyzed with the Mann-Whitney U-test. PFS was analyzed using multivariate analysis with the Cox proportional hazards model and included the following variables: age, sex, tumor size, tumor subtype, resection rate, radiation therapy, and methylation status. RESULTS TERT promoter hotspot mutations were not observed in any PA sample. Nineteen percent of PAs exhibitedTERT promoter methylation, which was significantly predominant in recurrent PA samples. PFS was significantly shorter in the methylated cases than in the unmethylated cases. Higher TERT expression levels were correlated with methylation status. CONCLUSION We found that TERT promoter methylation upregulated TERT expression and was associated with shorter PFS in PAs. Our results suggest thatTERT promoter methylation may be a potential biomarker for predicting tumor recurrence in PAs.