Project description:Pituicytoma (PITUI), granular cell tumor (GCT), and spindle cell oncocytoma (SCO) are rare tumors of the posterior pituitary lobe. Histologically, they may be challenging to distinguish and have been proposed to represent a histological spectrum of a single entity. We performed targeted next-generation sequencing, DNA methylation profiling, and copy number analysis on 47 tumors (14 PITUI; 12 GCT; 21 SCO) to investigate molecular features and explore possibilities of clinically meaningful tumor subclassification. We detected two main epigenomic subgroups by unsupervised clustering of DNA methylation data, though the overall methylation differences were subtle. The largest group (n=23) contained most PITUIs and a subset of SCOs and was enriched for pathogenic mutations within genes in the MAPK/PI3K pathways (12/17 [71%] of sequenced tumors: FGFR1 (3), HRAS (3), BRAF (2), NF1 (2), CBL (1), MAP2K2 (1), PTEN (1)) and two with TERT promoter mutation. The second group (n=16) contained most GCTs and a subset of SCOs, which mostly lacked identifiable genetic drivers. Outcome analysis demonstrated that the presence of chromosomal imbalances is significantly associated with reduced progression-free survival especially within the combined PITUI and SCO group (p= 0.031). In summary, we observed only subtle DNA methylation differences between posterior pituitary tumors, indicating that these tumors may be best classified as subtypes of a single entity. Nevertheless, our data indicate differences in mutation patterns and clinical outcome. For a clinically meaningful subclassification, we propose a combined histo-molecular approach into three subtypes: One subtype is defined by granular cell histology, has low mutation rates and favorable outcome. The other two subtypes have SCO or PITUI histology but are separated by chromosomal copy number profile into a favorable group (no copy number changes) and a less favorable group (copy number imbalances present). Both of the latter groups have recurrent MAPK alterations that represent potential therapeutic targets.

Project description:Pituicytoma (PITUI), granular cell tumor (GCT), and spindle cell oncocytoma (SCO) are rare tumors of the posterior pituitary. Histologically, they may be challenging to distinguish and have been proposed to represent a histological spectrum of a single entity. We performed targeted next-generation sequencing, DNA methylation profiling, and copy number analysis on 47 tumors (14 PITUI; 12 GCT; 21 SCO) to investigate molecular features and explore possibilities of clinically meaningful tumor subclassification. We detected two main epigenomic subgroups by unsupervised clustering of DNA methylation data, though the overall methylation differences were subtle. The largest group (n = 23) contained most PITUIs and a subset of SCOs and was enriched for pathogenic mutations within genes in the MAPK/PI3K pathways (12/17 [71%] of sequenced tumors: FGFR1 (3), HRAS (3), BRAF (2), NF1 (2), CBL (1), MAP2K2 (1), PTEN (1)) and two with accompanying TERT promoter mutation. The second group (n = 16) contained most GCTs and a subset of SCOs, all of which mostly lacked identifiable genetic drivers. Outcome analysis demonstrated that the presence of chromosomal imbalances was significantly associated with reduced progression-free survival especially within the combined PITUI and SCO group (p = 0.031). In summary, we observed only subtle DNA methylation differences between posterior pituitary tumors, indicating that these tumors may be best classified as subtypes of a single entity. Nevertheless, our data indicate differences in mutation patterns and clinical outcome. For a clinically meaningful subclassification, we propose a combined histo-molecular approach into three subtypes: one subtype is defined by granular cell histology, scarcity of identifiable oncogenic mutations, and favorable outcome. The other two subtypes have either SCO or PITUI histology but are segregated by chromosomal copy number profile into a favorable group (no copy number changes) and a less favorable group (copy number imbalances present). Both of the latter groups have recurrent MAPK/PI3K genetic alterations that represent potential therapeutic targets.

Project description:Gonadotrope or null cell pituitary tumors present clinically with signs of hypogonadism and hypopituitarism, together with visual disturbances due to mass effects. Since there are no medical therapies, surgery and/or radiation are the only therapeutic options. To identify dysregulated genes and/or pathways that may play a role in tumorigenesis and/ or progression, molecular profiling was performed on 14 gonadotrope tumors and 9 normal human pituitaries from autopsy samples. Principle component analysis (PCA) revealed clear discrimination between tumor and normal pituitary gene expression profiles. Bioinformatic analysis identified specific genes and pathways that were highly differentially regulated, including a cohort of putative downstream effectors of p53 were repressed in gonadotrope pituitary tumors, including GADD45Î², GADD45Î³ and Reprimo with concomitant downregulation of the upstream regulator, PLAGL1. PLAGL1 reexpression in gonadotrope cells did not directly modulate the downstream targets. Further functional analysis of GADD45Î² was performed. Overexpression of GADD45Î² in mouse gonadotrope cells blocked proliferation, increased rates of apoptosis in response to growth factor withdrawal and increased colony formation in soft agar. In contrast to prior studies with GADD45Î³, methylation interference assays showed no evidence of epigenetic modification of the GADD45Î² promoter in pituitary tumors. Thus, our data suggest that many components downstream of p53 are suppressed in gonadotrope pituitary tumors. A novel candidate, GADD45Î² is low in tumors and reexpression blocks proliferation, survival and tumorigenesis in gonadotrope cells. Unlike GADD45Î³, GADD45Î² is not methylated to block its expression. Together these studies identify new targets and mechanisms to explore concerning pituitary tumor initiation and progression. To elucidate mechanisms involved in pituitary tumorigenesis and progression, we performed individual gene expression microarray analysis using Affy U133 Plus 2.0 GeneChips comparing 14 gonadotrope tumors with 9 normal pituitary samples obtained at autopsy.

Project description:Pituitary adenomas are common benign neoplasms giving rise to disorders of growth, reproductive function and cortisol production. Although recently determined to be monoclonal, very little is known about the mechanisms regulating the development of pituitary hyperplasia and neoplasia in humans. Surgical resection is the treatment of choice for most symptomatic pituitary adenomas. The goal of surgery is the complete removal of the tumor and the success of surgery is strongly affected by the presence of local invasion. However, complete tumor removal is unlikely when there is extensive local invasion. Identifying genes that control the invasiveness and recurrence of this class of tumors will provide therapeutic targets for this class of tumors. We will determine the expression pattern of genes in recurrent and invasive and pituitary adenomas and compare those to non-invasive and non-recurrent tumors. We hypothesize that the differential expression and activation of a number of genes affect pituitary adenoma recurrence and invasiveness. Rationale: Preliminary result showed a differential expression of novel PKC isozymes in non-invasive and invasive pituitary adenomas. PMA, an activator of both novel and classical PKC isozymes increased the expression of gelatinase A (MMP-2) mRNA in human pituitary adenoma cell line. This result raises a fundamental question as to the functional role of novel PKC isozymes and proteases in the invasive phenotype of pituitary adenomas. The primary component of this Specific Aim is to determine whether specific genes are differentially expressed in recurrent or invasive adenomas when compared with control non-invasive tumors. Tissue specimens from non-invasive and invasive (dural invasion based microscopic examination) and recurrent vs non-recurrent tumors will be used for microarray analysis. Frozen pituitaryspecimens will be collected and total RNA extracted with TriZol reagent. We will provide total RNA (10 ug) from non-invasive, invasive, reoccurred and non-occurrent pituitary adenomas.

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Genetic and epigenetic characterization of posterior pituitary tumors

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