Invasive and Noninvasive Nonfunctioning Gonadotroph Pituitary Tumors Differ in DNA Methylation Level of LINE-1 Repetitive Elements

Abstract

Purpose: Epigenetic dysregulation plays a role in pituitary tumor pathogenesis. Some differences in DNA methylation were observed between invasive and noninvasive nonfunctioning gonadotroph tumors. This study sought to determine the role of DNA methylation changes in repetitive LINE-1 elements in nonfunctioning gonadotroph pituitary tumors. Methods: We investigated LINE-1 methylation levels in 80 tumors and normal pituitary glands with bisulfite-pyrosequencing. Expression of two LINE-1 open reading frames (L1-ORF1 and L1-ORF2) was analyzed with qRT-PCR in tumor samples and mouse gonadotroph pituitary cells treated with DNA methyltransferase inhibitor. Immunohistochemical staining against L1-ORF1p was also performed in normal pituitary glands and tumors. Results: Hypomethylation of LINE-1 was observed in pituitary tumors. Tumors characterized by invasive growth revealed lower LINE-1 methylation level than noninvasive ones. LINE-1 methylation correlated with overall DNA methylation assessed with HM450K arrays and negatively correlated with L1-ORF1 and L1-ORF2 expression. Treatment of αT3-1 gonadotroph cells with 5-Azacytidine clearly increased the level of L1-ORF1 and L1-ORF2 mRNA; however, its effect on LβT2 cells was less pronounced. Immunoreactivity against L1-ORF1p was higher in tumors than normal tissue. No difference in L1-ORF1p expression was observed in invasive and noninvasive tumors. Conclusion: Hypomethylation of LINE-1 is related to invasive growth and influences transcriptional activity of transposable elements.

Transcriptomic Classification of Pituitary Neuroendocrine Tumors Causing Acromegaly

“…SF-1 ( NR5A1 ) is a commonly accepted marker of pituitary gonadotroph cell lineage; therefore, its higher expression in group 1 of somatotropinomas requires special attention. We measured NR5A1 expression in somatotroph tumors of transcriptomic group 1 and gonadotroph PitNET samples (tumor samples from our previous investigation [ 38 ]) with qRT-PCR. This analysis showed that the range of NR5A1 expression in group 1 of somatotroph PitNETs and in gonadotroph PitNETs is similar ( Figure 5 B).…”

Transcriptomic classification of pituitary neuroendocrine tumors causing acromegaly

“…SF-1 ( NR5A1 ) is a commonly accepted marker of pituitary gonadotroph cell lineage, therefore, its higher expression in group 1 of somatotropinomas requires special attention (Figure 4). We measured NR5A1 expression in somatotroph tumors of transcriptional group 1 and gonadotroph PitNET samples (tumor samples from our previous investigation (Rusetska et al , 2021)) with qRT-PCR. This showed that the range of NR5A1 expression in group 1 somatotroph PitNETs and gonadotroph PitNETs is similar (Figure 4B).…”

MiR-128-3p – a gray eminence of the human central nervous system

“…The mechanisms responsible for their genesis and progression into more aggressive forms remain unknown. 83 , 84 , 85 In the aggressive pituitary adenoma type, miR-128-3p is one of the few microRNAs suppressed compared with control tissues. Its reintroduction into pituitary cancer cells inhibits their colony-forming ability and invasiveness in vitro .…”