Background Circulating miRNAs in pituitary adenomas would improve patient care, especially as minimally invasive biomarkers of tumor recurrence and progression in nonfunctioning adenoma cases. Aim Our aim was to investigate plasma miRNA profiles in patients with pituitary adenomas. Materials and Methods A total of 149 plasma and extracellular vesicle (preoperative, early postoperative, and late postoperative) samples were collected from 45 patients with pituitary adenomas. Adenomas were characterized on the basis of anterior pituitary hormones and transcription factors by immunostaining. miRNA next-generation sequencing was performed on 36 samples (discovery set). Individual TaqMan assays were used for validation on an extended sample set. Pituitary adenoma tissue miRNAs were evaluated by TaqMan array and data in the literature. Results Global downregulation of miRNA expression was observed in plasma samples of pituitary adenomas compared with normal samples. Expression of 29 miRNAs and isomiR variants were able to distinguish preoperative plasma samples from normal controls. miRNAs with altered expression in both plasma and different adenoma tissues were identified. Three, seven, and 66 miRNAs expressed differentially between preoperative and postoperative plasma samples in GH-secreting, FSH/LH+, and hormone-immunonegative groups, respectively. miR‒143-3p was downregulated in late postoperative but not in early postoperative plasma samples compared with preoperative ones exclusively in FSH/LH+ adenomas. The plasma level of miR‒143-3p discriminated these samples with 81.8% sensitivity and 72.3% specificity (area under the curve = 0.79; P = 0.02). Conclusions Differentially expressed miRNAs in pituitary adenoma tissues have low abundance in plasma, minimizing their role as biomarkers. Plasma miR‒143-3p level decreased in patients with FSH/LH+ adenomas, indicating successful surgery, but its application for evaluating tumor recurrence needs further investigation.
Pheochromocytoma/paragangliomas (Pheo/PGL) are rare endocrine cancers with strong genetic background. Mutations in the SDHB subunit of succinate dehydrogenase (SDH) predispose patients to malignant disease with limited therapeutic options and poor prognosis. Using a host of cellular and molecular biology techniques in 2D and 3D cell culture formats we show that SDH inhibition had cell line specific biological and biochemical consequences. Based on our studies performed on PC12 (rat chromaffin cell line), Hela (human cervix epithelial cell line), and H295R (human adrenocortical cell line) cells, we demonstrated that chromaffin cells were not affected negatively by the inhibition of SDH either by siRNA directed against SDHB or treatment with SDH inhibitors (itaconate and atpenin A5). Cell viability and intracellular metabolite measurements pointed to the cell line specific consequences of SDH impairment and to the importance of glutamate metabolism in chromaffin cells. A significant increase in glutaminase-1 (GLS-1) expression after SDH impairment was observed in PC12 cells. GLS-1 inhibitor BPTES was capable of significantly decreasing proliferation of SDH impaired PC12 cells. Glutaminase-1 and SDHB expressions were tested in 35 Pheo/PGL tumor tissues. Expression of GLS1 was higher in the SDHB low expressed group compared to SDHB high expressed tumors. Our data suggest that the SDH-associated malignant potential of Pheo/PGL is strongly dependent on GLS-1 expression and glutaminases may be novel targets for therapy.
Purpose Disrupted mitochondrial functions and genetic variants of mitochondrial DNA (mtDNA) have been observed in different human neoplasms. Next-generation sequencing (NGS) can be used to detect even low heteroplasmy-level mtDNA variants. We aimed to investigate the mitochondrial genome in pituitary adenomas by NGS. Methods We analysed 11 growth hormone producing and 33 non-functioning [22 gonadotroph and 11 hormone immunonegative] pituitary adenomas using VariantPro™ Mitochondrion Panel on Illumina MiSeq instrument. Revised Cambridge Reference Sequence (rCRS) of the mtDNA was used as reference. Heteroplasmy was determined using a 3% cutoff. Results 496 variants were identified in pituitary adenomas with overall low level of heteroplasmy (7.22%). On average, 35 variants were detected per sample. Samples harbouring the highest number of variants had the highest Ki-67 indices independently of histological subtypes. We identified eight variants (A11251G, T4216C, T16126C, C15452A, T14798C, A188G, G185A, and T16093C) with different prevalences among different histological groups. T16189C was found in 40% of non-recurrent adenomas, while it was not present in the recurrent ones. T14798C and T4216C were confirmed by Sanger sequencing in all 44 samples. 100% concordance was found between NGS and Sanger method. Conclusions NGS is a reliable method for investigating mitochondrial genome and heteroplasmy in pituitary adenomas. Out of the 496 detected variants, 414 have not been previously reported in pituitary adenoma. The high number of mtDNA variants may contribute to adenoma genesis, and some variants (i.e., T16189C) might associate with benign behaviour. Electronic supplementary material The online version of this article (10.1007/s40618-019-1005-6) contains supplementary material, which is available to authorized users.
Background Cytosine intermediaries 5-methylcytosine (5mC) and 5-hydroxymethylcytosine (5hmC), epigenetic hallmarks, have never been investigated in pituitary neuroendocrine tumors (PitNET). Objective To examine methylation-demethylation status of global deoxyribonucleic acid (DNA) in PitNET tissues and to assess its correlation with clinical and biological parameters. Materials and Methods Altogether, 57 PitNET and 25 corresponding plasma samples were collected. 5mC and 5hmC were investigated using liquid chromatography–tandem mass spectrometry. Expression of DNA methyltransferase 1 (DNMT1); tet methylcytosine dioxygenase 1 through 3 (TET1-3); and ubiquitin-like, containing PHD and RING finger domains 1 and 2 (UHRF1-2) were measured by reverse transcription–polymerase chain reaction. Levels of 5hmC and UHRF1-2 were explored by immunohistochemistry. Effect of demethylating agent decitabine was tested on pituitary cell lines. Results 5hmC/5mC ratio was higher in less differentiated PitNET samples. A negative correlation between Ki-67 proliferation index and 5hmC, 5hmC to 5mC ratio were revealed. Higher 5mC was observed in SF-1 + gonadotroph adenomas with a higher Ki-67 index. Expressions of TET2 and TET3 were significantly higher in adenomas with higher proliferation rate. UHRF1 showed gradually increased expression in higher proliferative adenoma samples, and a significant positive correlation was detected between UHRF2 expression and 5hmC level. Decitabine treatment significantly decreased 5mC and increased 5hmC levels in both cell lines, accompanied with decreased cell viability and proliferation. Conclusion The demethylation process negatively correlated with proliferation rate and the ratio of 5hmC to 5mC was higher in less differentiated adenomas. Therefore, epigenetic markers can be potential biomarkers for PitNET behavior. Altering the epigenome in adenoma cells by decitabine decreased proliferation, suggesting that this treatment might be a novel medical treatment for PitNET.
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