PCSK1N as a tumor size marker and an ER stress response protein in corticotroph pituitary adenomas.

PURPOSE: Silent corticotroph adenoma (SCA) exhibits more tumor aggressiveness features than functioning adenomas (FCA). We aimed to investigate PCSK1N expression in CA and examine if ER stress-induced responses affect cell survival in a corticotroph tumor cell model. METHODS: Clinical and imaging characteristics were recorded in 33 patients with FCA (20 women, 11 macroadenomas) and 18 SCA (8 women, all macroadenomas). Gene expression of proopiomelanocortin (POMC), T-box transcription factor 19(TBX19)/TPIT, proprotein convertase subtilisin/kexin type 1(PCSK1)/PC1/3, and its inhibitor PCSK1N, was measured by RT-qPCR in adenoma tissue.Mouse pituitary corticotroph tumor (AtT-20) cells were treated with tanespimycin (17-AAG), a HSP90 chaperone inhibitor, to induce ER stress, followed by gene and protein analyses. RESULTS: POMC, TPIT, and PCSK1 expression were higher, whereas PCSK1N was lower in FCA compared to SCA. PCSK1N correlated with POMC (rs= -0.514, p <0.001), TPIT (rs= -0.386, p = 0.005), PCSK1 (rs= -0.3691, p = 0.008), and tumor largest diameter (rs= 0.645, p <0.001), in all CA. Induction of ER stress by 17-AAG in AtT-20 cells led to a decrease of POMC and an increase of PCSK1N gene expression at 24h. Moreover, a downregulation of cell cycle, apoptosis, and senescence pathways, and alterations in cell adhesion and cytoskeleton were observed at the protein level. CONCLUSIONS: PCSK1N is higher in SCA compared with FCA, and associated with corticotroph cell markers and tumor size. PCSK1N is likely to be part of the adaptive response to ER stress, potentially conferring a survival advantage to the corticotroph tumor cell in conjunction with other proteins.

TGFBR3L-An Uncharacterised Pituitary Specific Membrane Protein Detected in the Gonadotroph Cells in Non-Neoplastic and Tumour Tissue.

Here, we report the investigation of transforming growth factor beta-receptor 3 like (TGFBR3L), an uncharacterised pituitary specific membrane protein, in non-neoplastic anterior pituitary gland and pituitary neuroendocrine tumours. A polyclonal antibody produced within the Human Protein Atlas project (HPA074356) was used for TGFBR3L staining and combined with SF1 and FSH for a 3-plex fluorescent protocol, providing more details about the cell lineage specificity of TGFBR3L expression. A cohort of 230 pituitary neuroendocrine tumours were analysed. In a subgroup of previously characterised gonadotroph tumours, correlation with expression of FSH/LH, E-cadherin, oestrogen (ER) and somatostatin receptors (SSTR) was explored. TGFBR3L showed membranous immunolabeling and was found to be gonadotroph cell lineage-specific, verified by co-expression with SF1 and FSH/LH staining in both tumour and non-neoplastic anterior pituitary tissues. TGFBR3L immunoreactivity was observed in gonadotroph tumours only and demonstrated intra-tumour heterogeneity with a perivascular location. TGFBR3L immunostaining correlated positively to both FSH (R = 0.290) and LH (R = 0.390) immunostaining, and SSTR3 (R = 0.315). TGFBR3L correlated inversely to membranous E-cadherin staining (R = -0.351) and oestrogen receptor ß mRNA (R = -0.274). In conclusion, TGFBR3L is a novel pituitary gland specific protein, located in the membrane of gonadotroph cells in non-neoplastic anterior pituitary gland and in a subset of gonadotroph pituitary tumours.

FSH Levels Are Related to E-cadherin Expression and Subcellular Location in Nonfunctioning Pituitary Tumors.

CONTEXT: Gonadotroph pituitary neuroendocrine tumors (PitNETs) can express follicle-stimulating hormone (FSH) and luteinizing hormone (LH) or be hormone negative, but they rarely secrete hormones. During tumor development, epithelial cells develop a mesenchymal phenotype. This process is characterized by decreased membranous E-cadherin and translocation of E-cadherin to the nucleus. Estrogen receptors (ERs) regulate both E-cadherin and FSH expression and secretion. Whether the hormone status of patients with gonadotroph PitNETs is regulated by epithelial-to-mesenchymal transition (EMT) and ERs is unknown. OBJECTIVES: To study the effect of EMT on hormone expression in gonadotroph nonfunctioning (NF)-PitNETs. DESIGN: Molecular and clinical analyses of 105 gonadotroph PitNETs. Immunohistochemical studies and real-time quantitative polymerase chain reaction were performed for FSH, LH, E-cadherin, and ERα. Further analyses included blood samples, clinical data, and radiological images. SETTING: All patients were operated on in the same tertiary referral center. RESULTS: NF-PitNET with high FSH expression had decreased immunohistochemical staining for membranous E-cadherin (P < .0001) and increased staining for nuclear E-cadherin (P < .0001). Furthermore, high FSH expression was associated with increased ERα staining (P = .0002) and ERα mRNA (P = .0039). Circulating levels of plasma-FSH (P-FSH) correlated with FSH staining in gonadotroph NF-PitNET (P = .0025). Tumor size and invasiveness was not related to FSH staining, E-cadherin, or ERα. LH expression was not associated with E-cadherin or ERα. CONCLUSION: In gonadotroph PitNETs, FSH staining is related to E-cadherin, ERα expression, and circulating levels of P-FSH. There was no association between FSH staining and invasiveness. The clinical significance of these findings will be investigated in ongoing prospective studies.

Distinct Pattern of Endoplasmic Reticulum Protein Processing and Extracellular Matrix Proteins in Functioning and Silent Corticotroph Pituitary Adenomas.

Functioning (FCA) and silent corticotroph (SCA) pituitary adenomas act differently from a clinical perspective, despite both subtypes showing positive TBX19 (TPIT) and/or adrenocorticotropic hormone (ACTH) staining by immunohistochemistry. They are challenging to treat, the former due to functional ACTH production and consequently hypercortisolemia, and the latter due to invasive and recurrent behavior. Moreover, the molecular mechanisms behind their distinct behavior are not clear. We investigated global transcriptome and proteome changes in order to identify signaling pathways that can explain FCA and SCA differences (e.g., hormone production vs. aggressive growth). In the transcriptomic study, cluster analyses of differentially expressed genes revealed two distinct groups in accordance with clinical and histological classification. However, in the proteomic study, a greater degree of heterogeneity within the SCA group was found. Genes and proteins related to protein synthesis and vesicular transport were expressed by both adenoma groups, although different types and a distinct pattern of collagen/extracellular matrix proteins were presented by each group. Moreover, several genes related to endoplasmic reticulum protein processing were overexpressed in the FCA group. Together, our findings shed light on the different repertoires of activated signaling pathways in corticotroph adenomas, namely, the increased protein processing capacity of FCA and a specific pattern of adhesion molecules that may play a role in the aggressiveness of SCA.