Correlations of pituitary tumor transforming gene expression with human pituitary adenomas: a meta-analysis

Expression and clinical significance of Cathepsin K and MMPs in invasive non-functioning pituitary adenomas

Background

Cathepsin K (CTSK) is a protease that degrades type I collagen and extracellular matrix, thereby contributing to bone resorption and tumor invasion. Some pituitary adenomas (PAs) could invade the sphenoid sinus (SS) and cavernous sinus (CS).

Purpose

This retrospective cohort study aimed to study the expression of tumoral biomarkers (CTSK, MMP9, MMP2, TIMP2, and PTTG1) and evaluate their clinical significance in non-functioning pituitary adenomas (NFPAs) with different invasion patterns.

Methods

We assessed the expression levels of candidate invasion-specific protein biomarkers CTSK, MMP9, MMP2, TIMP2, and PTTG1 by immunohistochemical staining in paraffin-embedded NFPA tumor tissues. Variations in staining intensity were analyzed in cases with SS and CS invasion and non-invasive NFPAs.

Results

We found that the levels of CTSK were higher in PA cases with SS invasion than that in PA cases with CS invasion (95.57 ± 31.57 vs. 65.29 ± 29.64, P < 0.001), and the expression of MMP9 and MMP2 was higher in CS-invasive cases than that in SS-invasive cases (145.02 ± 49.25 vs. 111.80 ± 51.37, P = 0.002, and 138.67 ± 52.06 vs. 108.30 ± 41.70, P = 0.002). Multiple Cox regression demonstrated that higher CTSK expression (P=0.011), subtotal resection (P<0.001), invasion (P=0.037), and larger tumor diameter (P=0.001) were independent risk factors for recurrence. A positive correlation was observed between CTSK expression and tumor size (r=0.671, p<0.001). There was no significant difference in TIMP2 and PTTG1 levels between CS-and SS-invasive cases (97.42± 39.80 vs. 102.10± 43.22, P = 0.58 and 13.89 ± 4.59 vs. 12.56 ± 3.96, P = 0.14).

Conclusion

Our data indicated that CTSK has the potential as a marker for SS invasion of PAs, whereas MMP9 and MMP2 may be markers for CS invasion. And CTSK may play an important role in tumor relapse.

The p300 Inhibitor A-485 Exerts Antitumor Activity in Growth Hormone Pituitary Adenoma

CONTEXT

Growth hormone pituitary adenoma (GHPA), a major subtype of pituitary adenoma (PA), can lead to progressive somatic disfigurement, multiple complications, and even increased mortality. The efficacy of current treatments is limited; thus, a novel pharmacological treatment is urgently needed. As a histone acetyltransferase (HAT) coactivator, p300 can regulate the transcription of several genes that are crucial for PA tumorigenesis and progression. However, the role of p300 and its catalytic inhibitor in GHPA is still unclear.

OBJECTIVE

We aimed to identify the expression of p300 in GHPA and in normal pituitary glands.

METHODS

The expression of p300 was detected in GHPA and normal pituitary tissues. Genetic knockdown was performed by siRNA. The efficacy of the p300 inhibitor A-485 in the cell cycle, proliferation, apoptosis, and hormone secretion was investigated by flow cytometry, ELISAs, Western blotting, and qRT-PCR. RNA sequencing, bioinformatic analysis, and subsequent validation experiments were performed to reveal the potential biological mechanism of A-485.

RESULTS

High expression of p300 was found in GHPA tissues compared with normal pituitary tissues. Knockdown of p300 inhibited cell proliferation and clone formation. Treatment with A-485 suppressed cell growth and inhibited the secretion of GH in vitro and in vivo. Further mechanistic studies showed that A-485 could downregulate the expression or activity of several oncogenes, such as genes in the Pttg1, c-Myc, cAMP and PI3K/AKT/mTOR signaling pathways, which are crucial for PA tumorigenesis and progression.

CONCLUSION

Our findings demonstrate that inhibition of HAT p300 by its selective inhibitor A-485 is a promising therapy for GHPA.

Aggressive pituitary tumours and pituitary carcinomas

Although usually benign, anterior pituitary tumours occasionally exhibit aggressive behaviour, with invasion of surrounding tissues, rapid growth, resistance to conventional treatments and multiple recurrences. In very rare cases, they metastasize and are termed pituitary carcinomas. The time between a 'classical' pituitary tumour and a pituitary carcinoma can be years, which means that monitoring should be performed regularly in patients with clinical (invasion and/or tumour growth) or pathological (Ki67 index, mitotic count and/or p53 detection) markers suggesting aggressiveness. However, although both invasion and proliferation have prognostic value, such parameters cannot predict outcome or malignancy without metastasis. Future research should focus on the biology of both tumour cells and their microenvironment, hopefully with improved therapeutic outcomes. Currently, the initial therapeutic approach for aggressive pituitary tumours is generally to repeat surgery or radiotherapy in expert centres. Standard medical treatments usually have no effect on tumour progression but they can be maintained on a long-term basis to, at least partly, control hypersecretion. In cases where standard treatments prove ineffective, temozolomide, the sole formally recommended treatment, is effective in only one-third of patients. Personalized use of emerging therapies, including peptide receptor radionuclide therapy, angiogenesis-targeted therapy and immunotherapy, will hopefully improve the outcomes of patients with this severe condition.

Novel Insights into Pituitary Tumorigenesis: Genetic and Epigenetic Mechanisms

Substantial advances have been made recently in the pathobiology of pituitary tumors. Similar to many other endocrine tumors, over the last few years we have recognized the role of germline and somatic mutations in a number of syndromic or nonsyndromic conditions with pituitary tumor predisposition. These include the identification of novel germline variants in patients with familial or simplex pituitary tumors and establishment of novel somatic variants identified through next generation sequencing. Advanced techniques have allowed the exploration of epigenetic mechanisms mediated through DNA methylation, histone modifications and noncoding RNAs, such as microRNA, long noncoding RNAs and circular RNAs. These mechanisms can influence tumor formation, growth, and invasion. While genetic and epigenetic mechanisms often disrupt similar pathways, such as cell cycle regulation, in pituitary tumors there is little overlap between genes altered by germline, somatic, and epigenetic mechanisms. The interplay between these complex mechanisms driving tumorigenesis are best studied in the emerging multiomics studies. Here, we summarize insights from the recent developments in the regulation of pituitary tumorigenesis.

G-protein Coupled Estrogen Receptor Expression in Growth Hormone Secreting and Non-Functioning Adenomas

PURPOSE

To evaluate the expression of G-protein coupled estrogen receptor (GPER1), aromatase, estrogen receptor α (ERα), estrogen receptor β (ERβ), pituitary tumor transforming gene (PTTG), and fibroblast growth factor 2 (FGF2) in GH-secreting and non-functioning adenomas (NFA).

METHODS

Thirty patients with acromegaly and 27 patients with NFA were included. Gene expression was determined via quantitative reverse transcription polymerase chain reaction (QRT-PCR). Protein expression was determined via immunohistochemistry.

RESULTS

There was no difference, in terms of gene expression of aromatase, ERα, PTTG, and FGF2 between the two groups (p>0.05 for all). ERβ gene expression was higher and GPER1 gene expression was lower in GH-secreting adenomas than NFAs (p<0.05 for all). Aromatase and ERβ protein expression was higher in GH-secreting adenomas than NFAs (p=0.01). None of the tumors expressed ERα. GPER1 expression was detected in 62.2% of the GH-secreting adenomas and 45% of NFAs. There was no difference in terms of GPER1, PTTG, FGF2 H scores between the two groups (p>0.05 for all). GPER1 gene expression was positively correlated to ERα, ERβ, PTTG, and FGF2 gene expression (p<0.05 for all). There was a positive correlation between aromatase and GPER1 protein expression (r=0.31; p=0.04).

CONCLUSIONS

GPER1 is expressed at both gene and protein level in a substantial portion of GH-secreting adenomas and NFAs. The finding of a positive correlation between GPER1 and ERα, ERβ, PTTG, and FGF2 gene expression and aromatase and GPER1 protein expression suggests GPER1 along with aromatase and classical ERs might mediate the effects of estrogen through upregulation of PTTG and FGF2.

Expression of Serum PTTG1 in Laryngeal Carcinoma and Its Correlation to Prognosis

Objectives.

The purpose of this study was to investigate serum pituitary tumor transforming gene (PTTG1) expression in laryngeal carcinoma and its relationship with the clinical pathological characteristics and prognosis.

Methods.

Expression of serum PTTG1 was measured by enzyme-linked immunosorbent assay in 110 patients with laryngeal carcinoma and 60 patients with vocal cord polyps. Expression of the serum PTTG1 levels relationship with the clinicopathological characteristics and prognosis were analyzed.

Results.

In laryngeal carcinoma patients’ serum, the PTTG1 median concentration was 141.43 pg/mL (interquartile range [IQR], 111.387 to 160.837 pg/mL), significantly higher than that of the vocal cord polyp group of 94.01 pg/mL (IQR, 81.26 to 108.59 pg/mL), and the difference was statistically significant (z=–6.715, P<0.001). PTTG1 expression with lymph node metastasis, clinical stage, and patients with laryngeal carcinoma was significantly correlated with the tumor differentiation degree (P<0.05). The total survival rate of the PTTG1 high expression group was significantly lower than the low expression group, and the difference of total survival time of the two groups was statistically significant (P<0.001).

Conclusion.

The PTTG1 expression level can be used as an index for evaluating prognosis of laryngeal cancer. High PTTG1 expression is one of the factors of poor prognosis of laryngeal carcinoma patients.

Acromegaly

Acromegaly is characterized by increased release of growth hormone and, consequently, insulin-like growth factor I (IGF1), most often by a pituitary adenoma. Prolonged exposure to excess hormone leads to progressive somatic disfigurement and a wide range of systemic manifestations that are associated with increased mortality. Although considered a rare disease, recent studies have reported an increased incidence of acromegaly owing to better disease awareness, improved diagnostic tools and perhaps a real increase in prevalence. Acromegaly treatment approaches, which include surgery, radiotherapy and medical therapy, have changed considerably over time owing to improved surgical procedures, development of new radiotherapy techniques and availability of new medical therapies. The optimal use of these treatments will reduce mortality in patients with acromegaly to levels in the general population. Medical therapy is currently an important treatment option and can even be the first-line treatment in patients with acromegaly who will not benefit from or are not suitable for first-line neurosurgical treatment. Pharmacological treatments include somatostatin receptor ligands (such as octreotide, lanreotide and pasireotide), dopamine agonists and the growth hormone receptor antagonist pegvisomant. In this Primer, we review the main aspects of acromegaly, including scientific advances that underlie expanding knowledge of disease pathogenesis, improvements in disease management and new medical therapies that are available and in development to improve disease control.

Identification of peptide-mediated interactions between human PTTG and SH3 domains in pALL gene expression profile

Human pituitary tumor-transforming gene (PTTG) plays an essential role in the development and progression of pediatric acute lymphoblastic leukemia (pALL). PTTG has two SH3-binding peptide motifs that can be recognized by a variety of SH3-containing proteins in the pALL through peptide-mediated interactions. In this study, the gene expression profile of pALL was examined in detail by integrating computational modeling and experimental assay, aiming to identify those potential partner proteins of human PTTG. The binding potency of domain candidates to peptide motifs was ranked using knowledge-based scoring and fluorescence titration. A number of SH3 domains found in a variety of pALL proteins were identified as potent binders with moderate or high affinity for PTTG. It is revealed that the PTTG peptide motifs show different affinity profiles for various candidate proteins, indicating that the PTTG selectivity is optimized across pALL gene expression space. The PTTG peptides were then mutated rationally to target the SH3 domains of identified partner proteins by competing with the native peptide motifs.

Integrated In Silico-In Vitro Identification and Characterization of the SH3-Mediated Interaction between Human PTTG and its Cognate Partners in Medulloblastoma

The human pituitary tumor-transforming gene is an oncogenic protein which serves as a central hub in the cellular signaling network of medulloblastoma. The protein contains two vicinal PxxP motifs at its C terminus that are potential binding sites of peptide-recognition SH3 domains. Here, a synthetic protocol that integrated in silico analysis and in vitro assay was described to identify the SH3-binding partners of pituitary tumor-transforming gene in the gene expression profile of medulloblastoma. In the procedure, a variety of structurally diverse, non-redundant SH3 domains with high gene expression in medulloblastoma were compiled, and their three-dimensional structures were either manually retrieved from the protein data bank database or computationally modeled through bioinformatics technique. The binding capability of these domains towards the two PxxP-containing peptides m1p: ¹⁶¹LGPPSPVK¹⁶⁸ and m2p: ¹⁶⁸KMPSPPWE¹⁷⁵ of pituitary tumor-transforming gene were ranked by structure-based scoring and fluorescence-based assay. Consequently, a number of SH3 domains, including MAP3K and PI3K, were found to have moderate or high affinity for m1p and/or m2p. Interestingly, the two overlapping peptides exhibits a distinct binding profile to these identified domain partners, suggesting that the binding selectivity of m1p and m2p is optimized across the medulloblastoma expression spectrum by competing for domain candidates. In addition, two redesigned versions of m1p peptide ware obtained via a structure-based rational mutation approach, which exhibited an increased affinity for the domain as compared to native peptide.

Expression and clinical significance of EGR-1 and PTEN in the pituitary tumors of elderly patients

The aim of the study was to investigate the expression and clinical significance of early growth response protein 1 (EGR-1) and phosphatase and tensin homolog (PTEN) in the pituitary tumors of elderly patients. From January 2014 to December 2015, we collected 25 patient cases with non-invasive pituitary tumors, 10 cases with invasive pituitary tumors and 35 cases with healthy pituitary tissues (the healthy control group). Immunohistochemical staining was used to detect the expression of EGR-1 and PTEN, and analyze specific differences. The expression of EGR-1 and PTEN in patients with invasive and non-invasive pituitary tumors increased significantly, when compared with the healthy control group, and the difference was statistically significant (p<0.05). In patients with invasive tumors, EGR-1 levels were higher than levels in patients with non-invasive tumors. The difference was statistically significant (p<0.05). PTEN levels in patients with invasive tumors were significantly lower than levels in patients with non-invasive tumors. The difference was statistically significant (p<0.05). In conclusion, EGR-1 and PTEN levels in patients with pituitary tumors were significantly higher. In addition, EGR-1 levels were higher in patients with invasive pituitary tumors, while PTEN levels were lower. The combination of increases in both levels highlights an important role in the evaluation and prognosis of elderly patients with pituitary tumors.

Genetic Aspects of Pituitary Adenomas

Although most of pituitary adenomas are benign, they may cause significant burden to patients. Sporadic adenomas represent the vast majority of the cases, where recognized somatic mutations (eg, GNAS or USP8), as well as altered gene-expression profile often affecting cell cycle proteins have been identified. More rarely, germline mutations predisposing to pituitary adenomas -as part of a syndrome (eg, MEN1 or Carney complex), or isolated to the pituitary (AIP or GPR101) can be identified. These alterations influence the biological behavior, clinical presentations and therapeutic responses, and their full understanding helps to provide appropriate care for these patients.

Transcriptome Analysis Showed a Differential Signature between Invasive and Non-invasive Corticotrophinomas

ACTH-dependent hypercortisolism caused by a pituitary adenoma [Cushing's disease (CD)] is the most common cause of endogenous Cushing's syndrome. CD is often associated with several morbidities, including hypertension, diabetes, osteoporosis/bone fractures, secondary infections, and increased cardiovascular mortality. While the majority (≈80%) of the corticotrophinomas visible on pituitary magnetic resonance imaging are microadenomas (MICs, <10 mm of diameter), some tumors are macroadenomas (MACs, ≥10 mm) with increased growth potential and invasiveness, exceptionally exhibiting malignant demeanor. In addition, larger and invasive MACs are associated with a significant increased risk of local complications, such as hypopituitarism and visual defects. Given the clinical and molecular heterogeneity of corticotrophinomas, the aim of this study was to investigate the pattern of genetic differential expression between MIC and MAC, including the invasiveness grade as a criterion for categorizing these tumors. In this study, were included tumor samples from patients with clinical, laboratorial, radiological, and histopathological diagnosis of hypercortisolism due to an ACTH-producing pituitary adenoma. Differential gene expression was studied using an Affymetrix microarray platform in 12 corticotrophinomas, classified as non-invasive MIC (n = 4) and MAC (n = 5), and invasive MAC (n = 3), according to modified Hardy criteria. Somatic mutations in USP8 were also investigated, but none of the patients exhibited USP8 variants. Differential expression analysis demonstrated that non-invasive MIC and MAC have a similar genetic signature, while invasive MACs exhibited a differential expression profile. Among the genes differentially expressed, we highlighted CCND2, ZNF676, DAPK1, and TIMP2, and their differential expression was validated through quantitative real-time PCR in another cohort of 15 non-invasive and 3 invasive cortocotrophinomas. We also identified potential biological pathways associated with growth and invasiveness, TGF-β and G protein signaling pathways, DNA damage response pathway, and pathways associated with focal adhesion. Our study revealed a differential pattern of genetic signature in a subgroup of MAC, supporting a genetic influence on corticotrophinomas in patients with CD.

Angiogenesis in pituitary adenomas: human studies and new mutant mouse models

The role of angiogenesis in pituitary tumor development has been questioned, as pituitary tumors have been usually found to be less vascularized than the normal pituitary tissue. Nevertheless, a significantly higher degree of vasculature has been shown in invasive or macropituitary prolactinomas when compared to noninvasive and microprolactinomas. Many growth factors and their receptors are involved in pituitary tumor development. For example, VEGF, FGF-2, FGFR1, and PTTG, which give a particular vascular phenotype, are modified in human and experimental pituitary adenomas of different histotypes. In particular, vascular endothelial growth factor, VEGF, the central mediator of angiogenesis in endocrine glands, was encountered in experimental and human pituitary tumors at different levels of expression and, in particular, was higher in dopamine agonist resistant prolactinomas. Furthermore, several anti-VEGF techniques lowered tumor burden in human and experimental pituitary adenomas. Therefore, even though the role of angiogenesis in pituitary adenomas is contentious, VEGF, making permeable pituitary endothelia, might contribute to adequate temporal vascular supply and mechanisms other than endothelial cell proliferation. The study of angiogenic factor expression in aggressive prolactinomas with resistance to dopamine agonists will yield important data in the search of therapeutical alternatives.