Project description:Secretion of growth hormone by sporadic somatotroph neuroendocrine pituitary tumors (PitNETs) is the most common cause of acromegaly.Genome-wide DNA methylation was investigated in 48 somatotroph PitNETs with EPIC microarrays. Three subtypes of the tumors were identified. Subtype 1 tumors are densely granulated tumors without GNAS mutation characterized by high expression of NR5A1 (SF-1) and GIPR. The expression of both genes is correlated with specific methylation pattern at gene body and promoter methylation. Subtype 1 has generally lower methylation level at 5’ gene regulatory regions and CpG islands as compared to other tumor clusters. Subtype 2 are densely granulated PiNETs with common GNAS-mutations while Subtype 3 are mainly sparsely granulated tumors. Methylation/expression analysis indicate that the levels of ~50% genes differentially expressed genes between tumor subtypes that are located at in differentially methylated regions are DNA methylation dependent. These DNA methylation-controlled genes include CDKN1B, CCND2, EBF3, CDH4, CDH12 MGMT, STAT5A, PLXND1, PTPRE and MMP16 as wells as genes encoding ion channels and semaphorins. Results of DNA methylation profiling confirms three molecular subtypes of somatotroph PitNETs that differ in both gene expression and methylation pattern. High expression of NR5A1 and GIPR in subtype 1 tumors is correlated to specific methylation at both genes.
Project description:Pituitary neuroendocrine tumors (PitNET)/adenomas are classified according to cell lineage, which requires immunohistochemistry for the transcription factors (TFs) PIT1, SF1, and TPIT. Co-expression of PIT1/SF1 was previously reported in PitNETs, which otherwise correspond to the somatotroph lineage. However, little is known about the clinicopathological features of these tumors. We compiled an in-house case series of 100 tumors, previously diagnosed as densely or sparsely granulated somatotroph PitNETs. Following TF staining, histopathological features associated with PIT1/SF1-coexpression were assessed. Global DNA methylation profiling was conducted on 31 of 100 in-house samples and integrated with publicly available sample data. The majority (74%, 52/70) of our densely granulated somatotroph PitNETs (DGST) unequivocally co-expressed PIT1 and SF1 (DGST-PIT1/SF1). None of our SGST (0%, 0/30) stained positive for SF1 (SGST-PIT1). Integrated molecular analyses including publicly available sample data confirmed that DGST-PIT1/SF1, DGST-PIT1 and SGST-PIT1 represent distinct tumour subtypes. In summary, we spotlight that a substantial proportion of previously diagnosed densely granulated somatotroph PitNET co-express PIT1 and SF1 and exhibit clinical, histopathological, and molecular distinctness from other pure PIT1-lineage somatotroph PitNET.
Project description:Corticotropin (ACTH)-secreting pituitary adenomas give rise to a severe endocrinological disorder, i.e., Cushing’s disease, with multifaceted clinical presentation and treatment outcomes. Experimental studies suggested that disease variability is inherent to the pituitary tumor, thus pointing to the need for further studies into tumor biology. Aim of the present study was to evaluate transcriptome expression pattern in a large series of ACTH-secreting pituitary adenoma specimens, in order to identify molecular signatures of these tumors. Gene expression profiling of formalin-fixed paraffin-embedded specimens from 40 human ACTH-secreting pituitary adenomas revealed significant expression of genes involved in protein biosynthesis and ribosomal function, in keeping with neuroendocrine cell profile. Unsupervised cluster analysis identified three distinct gene profile clusters and several genes were uniquely overexpressed in a given cluster, accounting for different molecular signatures. Of note, gene expression profiles were associated with clinical features such as age and size of the tumor. Altogether, our study shows that corticotrope tumors are characterized by neuroendocrine gene expression profile and present subgroup-specific molecular features.
Project description:Background: Lactotroph pituitary neuroendocrine tumors (PitNETs) are common pituitary tumors, but their underlying molecular mechanisms remain unclear. This study aimed to investigate the transcriptomic landscape of lactotroph PitNETs and identify potential molecular mechanisms and therapeutic targets through RNA sequencing and ingenuity pathway analysis (IPA). Methods: Lactotroph PitNET tissues from five surgical cases without dopamine agonist treatment underwent RNA sequencing. Normal pituitary tissues from three patients served as controls. Differentially expressed genes (DEGs) were identified, and the functional pathways and gene networks were explored by IPA. Results: Transcriptome analysis revealed that lactotroph PitNETs had gene expression patterns that were distinct from normal pituitary tissues. We identified 1,172 upregulated DEGs, including nine long intergenic noncoding RNAs (lincRNAs) belonging to the top 30 DEGs. IPA of the upregulated DEGs showed that the estrogen receptor signaling, oxidative phosphorylation signaling, and EIF signaling were activated. In gene network analysis, key upstream regulators, such as EGR1, PRKACA, PITX2, CREB1, and JUND, may play critical roles in lactotroph PitNETs.
Project description:The tumorigenesis of small intestinal neuroendocrine tumors (NETs) is poorly understood. Recent studies have associated alternative polyadenylation with proliferation, cell transformation and cancer. Polyadenylation is the process in which the pre-mRNA is cleaved at a polyA site and a polyA tail is added. Genes with two or more polyA sites can undergo alternative polyadenylation. This produces two or more distinct mRNA isoforms with different 3M-bM-^@M-^Y untranslated regions. Additionally, alternative polyadenylation can also produce mRNAs containing different 3M-bM-^@M-^Y-terminal coding regions. Therefore, alternative polyadenylation alters both the repertoire and the expression level of proteins. Here we used high-throughput sequencing data to map polyA sites and characterize polyadenylation genome-wide in three small intestinal neuroendocrine tumors and a reference sample. In the tumors sixteen genes showed significant changes of alternative polyadenylation pattern, which lead to either the 3M-bM-^@M-^Y truncation of mRNA coding regions or 3M-bM-^@M-^Y untranslated regions. Among these, 11 genes had been previously associated with cancer, with 4 genes being known tumor suppressors: DCC, PDZD2, MAGI1 and DACT2. We validated the alternative polyadenylation in 3 out of 3 cases with Q-RT-PCR. Our findings suggest that changes of alternative polyadenylation pattern in these 16 genes could be involved in the tumorigenesis of small intestinal neuroendocrine tumors. Furthermore, they also point to alternative polyadenylation as a new target for both diagnostic and treatment of small intestinal neuroendocrine tumors. The identified genes with alternative polyadenylation specific to the small intestinal neuroendocrine tumors could be further tested as diagnostic markers and drug targets for disease prevention and treatment. PolyA-seq profiling of 3 human neuroendocrine tumors compared and pituitary using Direct RNA Sequencing from Helicos Biosciences Technology
Project description:Acromegaly is a severe and life-threatening disease caused by persistent excess of growth hormone (GH) which stimulates the synthesis and secretion of insulin-like growth factor-1 (IGF-1). In the majority (95%) of patients acromegaly is caused by sporadic GH-secreting neuroendocrine pituitary tumor (PitNET). Acromegaly-causing tumors are histologically diverse. The aim was to determine transcriptomic profiles in different histological subtypes and evaluate clinical implication of differential gene expression.