Endocrine Abstracts

Background: Although the role of hypermethylation of certain tumor suppressor genes are known in pituitary adenomas little information is available regarding whole methylation-demethylation status and especially regarding its correlation with clinical parameters. High-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) is an easy and accurate method to detect the level of methylcytosine (5 mC) and the demethylation intermedier hydroxymethylcytosine (5 hmC) too.

Material and methods: Overall, 44 fresh frozen pituitary adenoma tissues (29 gonadotroph, 12 somatotroph, 3 corticotroph). were collected and categorized according to the 2017 WHO classification After DNA extraction cytosine (C)%, 5mC% and 5 hmC% and (5 hmC/5 mC)*100) ratios were determined by HPLC-MS/MS system. Results were correlated with clinicopathological parameters.

Results: Higher level of 5hmC% and 5hmC%/5mC% ratio was confirmed in hormone-negative (HN) HN-SF1+ and HN-Tpit+ groups compared to FSH/LH+ and GH secreting adenomas. Significant difference between HN-SF1+ gonadotroph and FSH/LH+ gonadotroph adenomas was found but there was no alteration between HN-SF1+ and HN-Tpit+ tumors. In samples with higher proliferative index (Ki-67>4% vs 1–2% or 3–4%) significantly lower 5 hmC% and 5hmC%/5mC% were detected regardless of tumor type (P=0.009). However, after dissecting histological groups this phenomenon was most characteristic of GH+ and HN adenomas and it was absent in FSH/LH+ adenomas (by two-way ANOVA both Ki-67 and histological group factors reached significance levels (P=0.003 and P=0.029, respectively)).

Conclusion: 5hmC% and 5hmC/5mC ratio indicating demethylation status can be reliably detected by HPLC-MS-MS method in somatic DNA extracted from pituitary adenomas. HN adenomas show increased demethylation compared to FSH/LH+ and GH+ adenomas independently from their transcription factor status. Adenomas with higher Ki-67 indexes exhibit gradually lower demethylation. 5 hmC/5 mC ratio may be used as prognostic tissue biomarker but these data need to be further investigated on higher sample set.