Expression of bcl-2 oncoprotein in pituitary tumours: comparison with c-myc

High-throughput Screening for Cushing Disease: Therapeutic Potential of Thiostrepton via Cell Cycle Regulation

Cushing disease is a life-threatening disorder caused by autonomous secretion of ACTH from pituitary neuroendocrine tumors (PitNETs). Few drugs are indicated for inoperative Cushing disease, in particular that due to aggressive PitNETs. To explore agents that regulate ACTH-secreting PitNETs, we conducted high-throughput screening (HTS) using AtT-20, a murine pituitary tumor cell line characterized by ACTH secretion. For the HTS, we constructed a live cell-based ACTH reporter assay for high-throughput evaluation of ACTH changes. This assay was based on HEK293T cells overexpressing components of the ACTH receptor and a fluorescent cAMP biosensor, with high-throughput acquisition of fluorescence images. We treated AtT-20 cells with compounds and assessed ACTH concentrations in the conditioned media using the reporter assay. Of 2480 screened bioactive compounds, over 50% inhibition of ACTH secreted from AtT-20 cells was seen with 84 compounds at 10 μM and 20 compounds at 1 μM. Among these hit compounds, we focused on thiostrepton (TS) and determined its antitumor effects in both in vitro and in vivo xenograft models of Cushing disease. Transcriptome and flow cytometry analyses revealed that TS administration induced AtT-20 cell cycle arrest at the G2/M phase, which was mediated by FOXM1-independent mechanisms including downregulation of cyclins. Simultaneous TS administration with a cyclin-dependent kinase 4/6 inhibitor that affected the cell cycle at the G0/1 phase showed cooperative antitumor effects. Thus, TS is a promising therapeutic agent for Cushing disease. Our list of hit compounds and new mechanistic insights into TS effects serve as a valuable foundation for future research.

Pituitary adenomas evade apoptosis via noxa deregulation in Cushing's disease

Sporadic pituitary adenomas occur in over 10% of the population. Hormone-secreting adenomas, including those causing Cushing’s disease (CD), cause severe morbidity and early mortality. Mechanistic studies of CD are hindered by a lack of in vitro models and control normal human pituitary glands. Here, we surgically annotate adenomas and adjacent normal glands in 25 of 34 patients. Using single-cell RNA sequencing (RNA-seq) analysis of 27594 cells, we identify CD adenoma transcriptomic signatures compared with adjacent normal cells, with validation by bulk RNA-seq, DNA methylation, qRT-PCR, and immunohistochemistry. CD adenoma cells include a subpopulation of proliferating, terminally differentiated corticotrophs. In CD adenomas, we find recurrent promoter hypomethylation and transcriptional upregulation of PMAIP1 (encoding pro-apoptotic BH3-only bcl-2 protein noxa) but paradoxical noxa downregulation. Using primary CD adenoma cell cultures and a corticotroph-enriched mouse cell line, we find that selective proteasomal inhibition with bortezomib stabilizes noxa and induces apoptosis, indicating its utility as an anti-tumor agent.

Asuzu et al. perform single-cell transcriptomic profiling in Cushing’s disease (CD) adenomas and find overexpression and DNA hypomethylation of PMAIP1, which encodes the pro-apoptotic protein noxa. Noxa is degraded by the proteasome. Proteasomal inhibition rescues noxa and induces apoptosis in CD.

Antagonists of Growth Hormone-Releasing Hormone Inhibit the Growth of Pituitary Adenoma Cells by Hampering Oncogenic Pathways and Promoting Apoptotic Signaling

Simple Summary

Many studies have demonstrated that the antagonists of growth hormone-releasing hormone (GHRH) exert inhibitory activities in a variety of experimental cancers; however, their potential antitumor role in pituitary adenomas (PAs) remains largely unknown. Here, we show that GHRH antagonists of Miami (MIA) class, MIA-602 and MIA-690, are able to reduce the growth and promote cell death in hormone-secreting PA cell lines, through the inhibition of mechanisms implicated in tumorigenesis and cancer progression. MIA-602 and MIA-690 also decreased the viability of tumor cells derived from human pituitary tumors. Overall, these findings suggest that GHRH antagonists may represent new therapeutic tools for the treatment of PAs, both alone or in combination with standard pharmacological treatments.

Abstract

Pituitary adenomas (PAs) are intracranial tumors, often associated with excessive hormonal secretion and severe comorbidities. Some patients are resistant to medical therapies; therefore, novel treatment options are needed. Antagonists of growth hormone-releasing hormone (GHRH) exert potent anticancer effects, and early GHRH antagonists were found to inhibit GHRH-induced secretion of pituitary GH in vitro and in vivo. However, the antitumor role of GHRH antagonists in PAs is largely unknown. Here, we show that the GHRH antagonists of MIAMI class, MIA-602 and MIA-690, inhibited cell viability and growth and promoted apoptosis in GH/prolactin-secreting GH3 PA cells transfected with human GHRH receptor (GH3-GHRHR), and in adrenocorticotropic hormone ACTH-secreting AtT20 PA cells. GHRH antagonists also reduced the expression of proteins involved in tumorigenesis and cancer progression, upregulated proapoptotic molecules, and lowered GHRH receptor levels. The combination of MIA-690 with temozolomide synergistically blunted the viability of GH3-GHRHR and AtT20 cells. Moreover, MIA-690 reduced both basal and GHRH-induced secretion of GH and intracellular cAMP levels. Finally, GHRH antagonists inhibited cell viability in human primary GH- and ACTH-PA cell cultures. Overall, our results suggest that GHRH antagonists, either alone or in combination with pharmacological treatments, may be considered for further development as therapy for PAs.

BRD4 as a therapeutic target for nonfunctioning and growth hormone pituitary adenoma

BACKGROUND

Nonfunctioning pituitary adenoma (NFPA) and growth hormone pituitary adenoma (GHPA) are major subtypes of pituitary adenomas (PAs). The primary treatment is surgical resection. However, radical excision remains challenging, and few effective medical therapies are available. It is urgent to find novel targets for the treatment. Bromodomain-containing protein 4 (BRD4) is an epigenetic regulator that leads to aberrant transcriptional activation of oncogenes. Herein, we investigated the pathological role of BRD4 and evaluated the effectiveness of BRD4 inhibitors in the treatment of NFPA and GHPA.

METHODS

The expression of BRD4 was detected in NFPA, GHPA, and normal pituitary tissues. The efficacies of BRD4 inhibitors were evaluated in GH3 and MMQ cell lines, patient-derived tumor cells, and in vivo mouse xenograft models of PA. Standard western blots, real-time PCR, and flow cytometry experiments were performed to investigate the effect of BRD4 inhibitors on cell cycle progression, apoptosis, and the expression patterns of downstream genes.

RESULTS

Immunohistochemistry studies demonstrated the overexpression of BRD4 in NFPA and GHPA. In vitro and in vivo studies showed that treatment with the BRD4 inhibitor ZBC-260 significantly inhibited the proliferation of PA cells. Further mechanistic studies revealed that ZBC-260 could downregulate the expression of c-Myc, B-cell lymphoma 2 (Bcl2), and related genes, which are vital factors in pituitary tumorigenesis.

CONCLUSION

In this study, we determined the overexpression of BRD4 in NFPA and GHPA and assessed the effects of BRD4 inhibitors on PA cells in vitro and in vivo. Our findings suggest that BRD4 is a promising therapeutic target for NFPA and GHPA.

Increased E2F1 mRNA and miR-17-5p Expression Is Correlated to Invasiveness and Proliferation of Pituitary Neuroendocrine Tumours

miR-17-5p and E2F1 have been described as deregulated in cancer, but they have scarcely been studied in pituitary neuroendocrine tumours (PitNETs). This study evaluates the relationship of E2F1 and miR-17-5p with the invasiveness and proliferation of PitNETs. In this cross-sectional descriptive study, we evaluated the expression of E2F1, MYC, and miR-17-5p by quantitative real time PCR analysis in 60 PitNETs: 29 gonadotroph (GT), 15 functioning somatotroph (ST), and 16 corticotroph (CT) tumours, of which 8 were silent (sCT). The clinical data were collected from the Spanish Molecular Register of Pituitary Adenomas (REMAH) database. We defined invasiveness according to the Knosp classification and proliferation according to a molecular expression of Ki-67 ≥ 2.59. E2F1 was more expressed in invasive than in non-invasive tumours in the whole series (p = 0.004) and in STs (p = 0.01). In addition, it was overexpressed in the silent subtypes (GTs and sCTs; all macroadenomas) and normoexpressed in the functioning ones (fCTs and STs; some microadenomas). miR-17-5p was more expressed in proliferative than in non-proliferative tumours (p = 0.041) in the whole series but not by subtypes. Conclusions: Our study suggests that in PitNETs, E2F1 could be a good biomarker of invasiveness, and miR-17-5p of proliferation, helping the clinical management of these tumours.

Expression of BCL-2, BAX and P53 Proteins in Pituitary Adenomas an Immunohistochemical Study

Aims and Background

Although pituitary adenomas are usually benign lesions, their growth rate is highly variable and unpredictable. Apoptosis appears to be an important process in neoplastic lesions. The purpose of this study was to investigate the expression of apoptosis-related proteins including Bcl-2, bax and p53 in pituitary adenomas and its correlation with hormone function, tumor size, local control, and proliferative activity.

Study Design

The expression of Bcl-2, Bax and p53 proteins and hormonal function were determined in formalin-fixed, paraffin-embedded tissue from 41 untreated pituitary adenomas using immunohistochemistry. The patients were followed for a median of 60 months (range, 12 to 95). Patient charts were reviewed to record tumor recurrence and size. Tumor proliferative activity was assessed by immunohistochemistry using Ki-67 antibody.

Results

Of 41 pituitary adenomas, 26 (63%) were hormone-secreting and 15 (37%) non-functioning, 34 (83%) were macroadenoma and 7 (17%) microadenoma, and 15 (37%) showed local relapse. Six (14%) adenomas were of low proliferative activity, whereas the others (86%) were non-proliferative. Immunohistochemically, 31 adenomas (75%) showed bcl-2 positivity, 37 (90%) bax positivity, and 7 (17%) p53 positivity. Statistical analysis revealed that Bcl-2 protein expression significantly diminished in prolactin-secreting and non-functioning adenomas (P = 0.005 and P = 0.006, respectively), and increased in growth hormone-secreting adenomas (P = 0.003). In addition, expression of bax protein significantly decreased in recurrent tumors, in contrast to p53 protein, which showed a significant increase (P = 0.03 and P = 0.002, respectively).

Conclusions

We think that apoptosis-related proteins such as Bcl-2, Bax and p53 may be significantly related to hormone function and local control in pituitary adenomas.

The interrelationship between genes, microprolactinoma and male homosexuality

This hypothesis clearly proposes the true and previously undiscovered cause of male homosexuality or bisexuality and in most cases the predictability in infancy of the development of this sexuality in adulthood. It is based on compelling new evidence which has accumulated over many years. The fetal and neonatal periods are of the utmost importance in human development because they encompass critical periods which must be adhered to, for normal development. Biological variations may occur during these times, without implying the process of disease. This paper takes into account new paediatric hormonal and other evidence which has accumulated in the past two decades concerning the causation of male homosexuality or bisexuality. It includes indirect genetic influence which has now been shown to be present. It also includes the implications of infant male breast development in regard to sexuality. It is asserted that the major cause of male homosexuality is due to failure of masculinisation of the male brain due to temporary but critical prolactin secretion from microprolactinoma present in their pituitary glands. Genes appear to be involved in the production of these tumours and sometimes in their demise. The assessment of their numbers at any one time in infancy has not been correctly addressed. Secondly, there is absolutely compulsive evidence concerning increased male infant breast development and the true nature of "Witch's Milk" and how it is produced and the profound implications of its presence in male neonates. It adds much persuasion to the causation of male homosexuality as enunciated in this paper. Measurement of testosterone levels at exactly and precisely the right time, are able to predict homosexual or bisexual development in adults. This knowledge would be of great help to parents.

Gene expression in prolactinomas: a systematic review

INTRODUCTION

Prolactinomas are the most common functional pituitary adenomas. Current classification systems rely on phenotypic elements and have few molecular markers for complementary classification. Treatment protocols for prolactinomas are also devoid of molecular targets, leaving those refractory to standard treatments without many options.

METHODS

A systematic literature review was performed utilizing the PRISMA guidelines. We aimed to summarize prior research exploring gene and protein expression in prolactinomas in order to highlight molecular variations associated with tumor development, growth, and prolactin secretion. A PubMed search of select MeSH terms was performed to identify all studies reporting gene and protein expression findings in prolactinomas from 1990 to 2014.

RESULTS

1392 abstracts were screened and 51 manuscripts were included in the analysis, yielding 54 upregulated and 95 downregulated genes measured by various direct and indirect analytical methods. Of the many genes identified, three upregulated (HMGA2, HST, SNAP25), and three downregulated (UGT2B7, Let7, miR-493) genes were selected for further analysis based on our subjective identification of strong potential targets.

CONCLUSIONS

Many significant genes have been identified and validated in prolactinomas and most have not been fully analyzed for therapeutic and diagnostic potential. These genes could become candidate molecular targets for biomarker development and precision drug targeting as well as catalyze deeper research efforts utilizing next generation profiling/sequencing techniques, particularly genome scale expression and epigenomic analyses.

The role of proto-oncogene GLI1 in pituitary adenoma formation and cell survival regulation

The Hedgehog (Hh) pathway is an important regulator of early tissue patterning and stem cell propagation. It was found to be aberrantly activated in numerous types of human cancer and might be relevant in cancer stem cells. The identification of adult stem cells in the pituitary raised the question if tumor-initiating cells and Hh signaling are involved in pituitary adenoma formation. The present study aimed at the evaluation of Hh signaling in relation to stem cell and cell cycle markers in 30 human pituitary adenomas and in cultured murine adenoma cells. Therefore, expression levels of components of the Hh pathway, stem cell marker SOX2, cell cycle regulator tumor-protein 53 (TP53), proliferation marker Ki67 (MKI67) and superoxide dismutase 1 (SOD1) were evaluated in 30 human pituitary adenomas in comparison to control tissue. Modulation of cell function and target gene expression by the inhibition and activation of the Hh pathway were studied in murine adenoma cells. We show that transcription factor glioma-associated oncogene 1 (GLI1) is overexpressed in 87% of all pituitary adenomas. The expression of GLI1 significantly correlated with that of SOX2, TP53, MKI67 and SOD1. Inhibition of GLI1 resulted in the downregulation of the above genes and severe cell death in mouse adenoma cells. On the other hand, activation of the Hh pathway increased cell viability and target gene expression. In conclusion, our findings point toward an alternative, ligand-independent Hh pathway activation with GLI1 playing a major role in the cell survival of pituitary adenoma cells.

Gene and protein expression in pituitary corticotroph adenomas: a systematic review of the literature

OBJECT Functional corticotroph pituitary adenomas (PAs) secrete adrenocorticotropic hormone (ACTH) and are the cause of Cushing's disease, which accounts for 70% of all cases of Cushing's syndrome. Current classification systems for PAs rely primarily on laboratory hormone findings, tumor size and morphology, invasiveness, and immunohistochemical findings. Likewise, drug development for functional ACTH-secreting PAs (ACTH-PAs) is limited and has focused largely on blocking the production or downstream effects of excess cortisol. The authors aimed to summarize the findings from previous studies that explored gene and protein expression of ACTH-PAs to prioritize potential genetic and protein targets for improved molecular diagnosis and treatment of Cushing's disease. METHODS A systematic literature review was performed using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. A PubMed search of select medical subject heading (MeSH) terms was performed to identify all studies that reported gene- and protein-expression findings in ACTH-PAs from January 1, 1990, to August 24, 2014, the day the search was performed. The inclusion criteria were studies on functional ACTH-PAs compared with normal pituitary glands, on human PA tissue only, with any method of analysis, and published in the English language. Studies using anything other than resected PA tissue, those that compared other adenoma types, those without baseline expression data, or those in which any pretreatment was delivered before analysis were excluded. RESULTS The primary search returned 1371 abstracts, of which 307 were found to be relevant. Of those, 178 were selected for secondary full-text analysis. Of these, 64 articles met the inclusion criteria and an additional 4 studies were identified from outside the search for a total of 68 included studies. Compared with the normal pituitary gland, significant gene overexpression in 43 genes and 22 proteins was reported, and gene underexpression in 58 genes and 15 proteins was reported. Immunohistochemistry was used in 39 of the studies, and reverse transcriptase polymerase chain reaction was used in 26 of the studies, primarily, and as validation for 4 others. Thirteen studies used both immunohistochemistry and reverse transcriptase polymerase chain reaction. Other methods used included microarray, in situ hybridization, Northern blot analysis, and Western blot analysis. Expression of prioritized genes emphasized in multiple studies were often validated on both the gene and protein levels. Genes/proteins found to be overexpressed in ACTH-PAs relative to the normal pituitary gland included hPTTG1/securin, NEUROD1/NeuroD1 (Beta2), HSD11B2/11β-hydroxysteroid dehydrogenase 2, AKT/Akt, protein kinase B, and CCND1/cyclin D1. Candidate genes/proteins found to be underexpressed in ACTH-PAs relative to the normal pituitary gland included CDKN1B/p27(Kip1), CDKN2A/p16, KISS1/kisspeptin, ACTHR/ACTH-R, and miR-493. CONCLUSIONS On the basis of the authors' systematic review, many significant gene and protein targets that may contribute to tumorigenesis, invasion, and hormone production/secretion of ACTH have been identified and validated in ACTH-PAs. Many of these potential targets have not been fully analyzed for their therapeutic and diagnostic potential but may represent candidate molecular targets for biomarker development and drug targeting. This review may help catalyze additional research efforts using modern profiling and sequencing techniques and alteration of gene expression.

Expression and clinical significance of Wnt players and survivin in pituitary tumours

Deregulation of the Wnt pathway has been implicated in oncogenesis of numerous tissues including the pituitary gland. Immunohistochemical localization and quantification of β-catenin, Cyclin D1, c-MYC and Survivin expression in 47 pituitary adenomas (35 non-functioning, seven GH-secreting, three prolactinomas, two ACTH-secreting tumour) and six normal controls was undertaken in this study and correlation of protein expression to patient and tumour characteristics analysed. β-catenin was strictly membrane-bound with no difference observed between normal and tumour tissue. In contrast, Cyclin D1 and c-MYC localization was nuclear and significantly higher in tumour versus normal tissue (p < 0.05). c-MYC expression correlated negatively with age at diagnosis (p = 0.006, R = -0.395) while Cyclin D1 expression correlated positively with age (p = 0.036, R = 0.306) and was higher in males than in females (p = 0.036). c-MYC expression was significantly lower in patients with functional tumours requiring octreotide treatment and in patients with non-functioning tumours suffering from hypopituitarism. Survivin expression was extremely low in tumours and absent in normal controls. Involvement of the canonical Wnt pathway appears to be minimal, given the segregation of β-catenin to the membrane. Our data suggest that c-MYC may have an important role in early pituitary tumorigenesis while Cyclin D1 is likely to promote tumour growth at a later stage. We also report a novel gender difference in Cyclin D1 expression, the biological significance of which merits further analysis. The reported reduction of c-MYC in functional tumours subsequently treated with octreotide further supports a role of c-MYC in early tumorigenesis and not in recurrence. The decrease in c-MYC in patients with hypopituitarism provides the first in vivo evidence for hormonal regulation of c-MYC expression.

MicroRNAs in the human pituitary

MicroRNAs (miRNAs) represent a novel class of small RNA molecules that play a crucial role as post-transcriptional regulators of gene expression. As evidence for the involvement of miRNAs in various cellular processes increases, it is important to examine how miRNAs regulate gene expression. In the pituitary, aberrant miRNA expression is strongly linked with neoplasia, thus suggesting they play a role in the control of cell proliferation in adenomas. Research has built fundamental connections between aberrant miRNA expression and clinicopathological features of pituitary adenomas. Moreover, deregulated expression of miRNA target genes is often implicated in important biological pathways and thus provides significant insight into the role of miRNAs in tumorigenesis. This review will assess the significance of miRNAs in pituitary pathology.

Identification of differentially expressed microRNAs by microarray: a possible role for microRNA genes in pituitary adenomas

MicroRNAs (miRNAs) are small non-coding RNAs that control gene expression by targeting mRNA. It has been demonstrated that miRNA expression is altered in many human cancers, suggesting that they may play a role in human neoplasia. To determine whether miRNA expression is altered in pituitary adenomas, we analyzed the entire miRNAome in 32 pituitary adenomas and in 6 normal pituitary samples by microarray and by Real-Time PCR. Here, we show that 30 miRNAs are differentially expressed between normal pituitary and pituitary adenomas. Moreover, 24 miRNAs were identified as a predictive signature of pituitary adenoma and 29 miRNAs were able to predict pituitary adenoma histotype. miRNA expression could differentiate micro- from macro-adenomas and treated from non-treated patient samples. Several of the identified miRNAs are involved in cell proliferation and apoptosis, suggesting that their deregulated expression may be involved in pituitary tumorigenesis. Predictive miRNAs could be potentially useful diagnostic markers, improving the classification of pituitary adenomas.

Inhibitory effects of melatonin on the growth of pituitary prolactin-secreting tumor in rats

The in vivo effects of melatonin on proliferation and apoptosis of 17-beta-estradiol (E2)-induced pituitary prolactin-secreting tumor (prolactinoma) were investigated in rats kept in 12 L/12 D (lights on: 06:00-18:00 hr). As melatonin was shown to induce apoptosis of breast and liver tumor cells, we examined whether melatonin would induce apoptosis of rat pituitary prolactinoma cells. 0.125, 0.25, 0.50 or 1.0 mg melatonin/day/rat was administrated subcutaneously at 17:30-18:00 hr. The weight of prolactinomas was measured. Apoptosis was evaluated using the TdT-mediated dUTP nick-end labeling method. It was found that treatment with 0.25 and 0.50 mg melatonin for 97 days inhibited prolactinoma cell proliferation and increased prolactinoma cell apoptosis. Furthermore, melatonin induced mRNA expression of Bax and cytochrome c protein expression. Conversely, mRNA expression of Bcl-2, and mitochondrial membrane potential were inhibited by melatonin treatment. These results suggest that melatonin inhibits the proliferation and induces apoptosis of rat pituitary prolactin-secreting tumor via perturbation of mitochondria physiology.

Magnetic resonance imaging and biological markers in pituitary adenomas with invasion of the cavernous sinus space

The preoperative diagnosis of cavernous sinus invasion remains difficult and controversial, and there are currently no reliable histological or molecular markers that predict pituitary tumour behaviour and response to treatment. We evaluated 45 patients with pituitary adenoma. The results have shown that the sensitivity of MRI for indicating cavernous sinus invasion in this prospective study was 60%, specificity 85%, positive predictive value 83.33%, negative predictive value 62.96%. Forty-five specimens of pituitary adenomas were analyzed for expression of F8, VEGF, Ki-67, c-myc, bcl-2, nm23 and MMP-9 immunoreactivity using immunoperoxidase staining. MVD was assessed using F8-related antigen. The results have shown that MVD of invasive pituitary adenomas was significantly higher than that of noninvasive (P < 0.001). There was an association between the invasion of pituitary adenomas and Ki-67 LI (P = 0.039) or the expression of VEGF (P < 0.001) and MMP-9 (P < 0.001). But c-myc LI and bcl-2 expression have no association with invasiveness of pituitary adenomas (P = 0.061 vs. P = 0.201). On the other hand, there is an inverse relationship between nm23 expression and tumor invasion (P < 0.001). In conclusion, parasellar extension of pituitary adenomas through the medial wall of the cavernous sinus diagnosed at surgery, can be determined by radiology with sensitive gadolinium-enhanced MRI. Although our study has shown that MVD and the expression of VEGF, Ki-67, nm23 and MMP-9 have associations with invasiveness of pituitary adenomas, they are lack of specificity. These markers can only provide some useful informations on the therapeutic strategy of pituitary adenomas.

Pituicytoma: Report of Two Cases and Clues Regarding Histogenesis

OBJECTIVE AND IMPORTANCE

The pituicytoma is a rare primary tumor of the neurohypophysis. Although histologically benign, the location and vascular nature of these tumors can make surgical resection difficult. We present a report of two patients with pituicytomas and review the literature regarding treatment and prognosis for this unusual lesion. Possible histogenetic relationships of this tumor with other pituitary neoplasms are presented.

CLINICAL PRESENTATION

Patient 1 was a 45-year-old man who presented with a 5-year history of decreased libido. He was found to have a 2-cm suprasellar mass on a magnetic resonance imaging scan. Patient 2 was a 48-year-old man who presented with multiple endocrine complaints. He was found to have an intrasellar mass on magnetic resonance imaging.

INTERVENTION

Patient 1 underwent a right frontal craniotomy, with a subtotal resection of the suprasellar mass through the lamina terminalis. The residual tumor was treated with fractionated stereotactic radiotherapy. The intrasellar mass in Patient 2 was resected via a transsphenoidal approach. On surveillance magnetic resonance imaging, the tumor was found to have recurred and expanded into the suprasellar space. The patient underwent a right frontal craniotomy for decompression and a subtotal resection of the tumor. The patient experienced a second recurrence 7 years after the initial procedure and was subsequently treated with fractionated stereotactic radiotherapy.

CONCLUSION

Pituicytomas are a distinct form of pituitary gland neoplasia that may recur if subtotally resected. These neurohypophysial tumors may contain a small subpopulation of previously unrecognized bcl-2-immunoreactive cells, whose role in the histogenesis of pituicytoma deserves further study.

Apoptotic cell death of oestrogen activated lactotrophs induced by tamoxifen

Stimulation and inhibition of lactotroph cells cause remarkable morphological and functional changes. In keeping with these changes, the size of the lactotroph cell population undergoes striking alterations due to proliferation or cell death. Factors involved in the induction of apoptosis of pituitary cells are not well established. We demonstrated earlier that oestrogens prevent lactotroph cells of female rats to die by apoptosis induced by bromocryptine treatment, a fact that can be reversed in ovariectomised rats. In this study, we developed experimental models for in vivo and in vitro studies to gain further insight on the survival effect of oestrogens on lactotrophs. In rats pretreated with oestrogens, tamoxifen generates a massive cell death by apoptosis as validated by the TUNEL technique and DNA electrophoresis of pituitary gland. On electron microscope observations, numerous lactotrophs exhibited progressive morphological changes in the nuclei compatible with the apoptotic process. The cells remaining intact also exhibit signs of inhibition due to a significant transformation of regular lactotrophs in atypical subtypes. In pituitary cell cultures exposed to tamoxifen and oestrogen simultaneously, most of the lactotrophs displayed features of apoptosis in the nucleus. The present reports gathered new evidences on the apoptogenic potential of tamoxifen on lactotroph cells, and corroborates the contribution of oestrogens to sustain both a balanced population of lactotrophs and a competent secretory activity. The concept that opposed activities, such as inhibition and stimulation, can activate apoptosis is also strengthen by these observations.

Correlation of bcl-2 and bax with apoptosis in human pituitary adenomas

Bcl-2 oncogene and Bax gene play an important role in regulating apoptosis. In the present study, the expression of bcl-2 and bax was investigated and correlated with apoptosis in a series of 81 pituitary adenomas. Bcl-2 and bax proteins were localized by immunohistochemistry and the histoscore (HSC) was assessed by multiplying the immunohistostaining grade (1 to 4) by the staining intensity grade (1 to 3). According to bcl-2/bax HSC the tumors were separated in group A when > or = 1 and group B when < 1. The apoptotic labeling index (ALI) was accessed by the in situ end-labeling (ISEL) technique. Bcl-2 protein was equally detected in functioning and nonfunctioning adenomas with statistically significant higher HSC in nonfunctioning tumors (P < 0.03). Bax protein was immunopositive in the substantial majority of adenomas with significantly higher HSC in functioning as compared to nonfunctioning adenomas (P < 0.0009). The ALI was significantly higher in functioning adenomas as compared to nonfunctioning adenomas (P < 0.04). In addition, ALI was significantly higher in group B than in group A (P < 0.004) and it was correlated with bax HSC (P < 0.004). Finally, the group B of bcl-2/bax significantly predominated in nonfunctioning tumors (P < 0.0009) and in microadenomas (P = 0.05), as compared with functioning adenomas and macroadenomas respectively. In conclusion, our findings suggest that bcl-2 and bax molecules play a role in the regulation of apoptotic mechanisms in pituitary adenomas.

Functional role of estrogen in pituitary tumor pathogenesis

Pituitary hyperplasia and lactotroph replication are induced by estrogen. The product of the pituitary tumor transforming gene (PTTG) exhibits in vitro and in vivo transforming activity and induces basic bFGF secretion, thereby modulating pituitary angiogenesis and tumor formation. We demonstrated previously that pituitary pttg is induced by estrogen and bFGF, the latter being expressed in a concordant fashion with pttg in experimental and human pituitary adenomas. We now elucidate the role of estrogen in paracrine regulation of pituitary tumorigenesis by PTTG. Coincident with the circulating rat estradiol surge and maximal pituitary proliferation, pituitary pttg mRNA, bFGF, and VEGF expression increased approximately threefold during proestrus and estrus. Osmotic mini-pump coinfusion of estrogen and antiestrogen abrogated estrogen-induced pituitary pttg expression in vivo, suppressed serum PRL concentrations by 88%, and attenuated prolactin-secreting pituitary tumor growth by 41% in rats. Antiestrogen treatment of primary human pituitary tumor cultures reduced PTTG expression approximately 65%. Pituitary pttg, bFGF, and VEGF are cyclically expressed during the rat estrus cycle, concordantly with estrogen levels. Because anti-estrogens reduced PTTG expression in human pituitary tumors in vitro and suppressed experimental tumor growth in vivo, concomitantly with reduced PRL secretion, these results indicate a role for selective antiestrogens in treating pituitary tumors.

Role of transcription factors in the pathogenesis of pituitary adenomas: a review

The diversity inherent in every organ has its roots in gene-expression variation and is revealed through distinctions in the molecular profile and hence the identity of individual cell type. Study into the molecular mechanisms of the development of individual cell type within the pituitary, which is under the control of transcription factors, has provided a basis for a deeper insight into the molecular mechanisms underlying the pathogenesis of a variety of hormone-producing pituitary tumors. Identification of some of these transcription factors in pituitary adenomas further supports their role in the pathogenesis of pituitary adenomas. Understanding the molecular mechanisms of regulation of proliferation of pituitary cell types by transcription factors offers a basis for hope that rational genetic or pharmacologic therapies for pituitary tumors can be designed in the future.

Dominant negative ER induces apoptosis in GH(4) pituitary lactotrope cells and inhibits tumor growth in nude mice

The ER plays an important role in the proliferation and differentiation of lactotrope tumor cells. GH(4) cells were infected with adenoviral vectors (AdL540Q and Ad1-536) to investigate the ability of dominant negative ER mutants to affect the regulation of gene expression and cell growth by endogenous ER. The dominant negative mutants suppressed estradiol stimulation of an estrogen-responsive reporter gene and the PRL promoter in these cells. AdL540Q or Ad1--536 infection also inhibited GH(4) cell growth and induced apoptosis, increasing the expression of the proapoptotic Bax protein and decreasing the expression of antiapoptotic Bcl-2. AdwtER-infected cells also showed decreased Bcl-2 protein. E2-induced activation of p38 MAPK, an enzyme that may participate in apoptosis, was observed in cells infected with AdwtER, AdL540Q, and Ad1--536. Consistent with the apoptotic effects in vitro, infection of GH(4) cells with AdL540Q or Ad1--536 inhibited the ability of the cells to form tumors in nude mice. These results indicate that dominant negative ER mutants induce apoptosis of GH(4) cells and suppress tumor formation and development. The delivery of dominant negative ERs by adenoviral vectors may provide an alternative modality for the targeted therapy of pituitary lactotrope adenomas and other estrogen-responsive tumors.

Genesis of pituitary adenomas: state of the art

In recent years, remarkable progress has been made in the understanding of the pathogenesis of pituitary tumors. Pituitary tumors originate from the uncontrolled proliferation of a single transformed cell in which an initiating event has caused a gain of proliferative function. After the initiation, promoting factors cooperate in the clonal expansion. Common oncogenes, such as ras, are only exceptionally involved. The only activating mutations identified so far are gsp mutations causing the constitutive activation of cAMP pathway. However, gsp-positive adenomas are not associated to a more aggressive tumoral phenotype. The oncogenic potential of gsp mutations is limited by a more rapid degradation of the mutant Gs(alpha) with respect to the wild-type protein, and by a faster removal of cAMP due to increased phosphodiesterase activity. Estrogen-inducible gene sequences with transforming properties (pituitary tumor-transforming gene (PTTG)) have been identified in human pituitary tumors. Human pituitary tumor-transforming gene (hPTTG) is involved both in early pituitary tumorigenesis, as it causes in vitro and in vivo transformation acting as a transcription activator, and in tumor progression, as it regulates the production of basic fibroblast growth factor (bFGF), a potent activator of angiogenesis and mitogenesis. Moreover, a role of cyclin D1 in pituitary tumorigenesis is emerging. The allelic loss of loci for unknown oncosuppressor genes are currently under investigation, while an exceedingly limited role for menin gene and RB1 has been demonstrated for sporadic pituitary tumors. Abnormal methylation that predisposing toward genetic instability may favor the allelic loss or the reduced expression of oncosuppressor genes, is also an emerging field of investigation. Several promoting factors, including the excessive action of physiological stimulators, the defective action of inhibitors, the susceptibility to respond to inappropriate stimuli and the locally produced growth factors, help in tumor progression. The study of homeobox genes that intervene in pituitary cell differentiation may help in expanding our knowledge in pituitary tumor cell genealogy.

Genetic basis of pituitary adenoma invasiveness: a review

Compatible with contemporary paradigms of the role of genetic aberrations in the progression of human tumors, the growth of pituitary tumors into a state of invasiveness appears to be due to genetic alterations. Amplification of H-ras and c-myc oncogenes and mutations of p53, nm23 and Rb genes have been identified disproportionately more in aggressive tumors and, in the case of Rb gene, in pituitary carcinomas, providing evidence that amplification of these oncogenes (H-ras and c-myc) and inactivation of tumor suppressor genes (p53, nm23 and Rb) seem to be at least one mechanism by which pituitary tumors progress. The current level of management of invasive pituitary adenomas should become more comprehensive as the advances in our understanding of genetic basis of pituitary adenoma invasiveness becomes translated into development of novel chemotherapy or gene transfer technique.

Molecular basis of pituitary oncogenesis

Recent advances in the molecular biology has served to unveil the underlying genetic and epigenetic alterations in pituitary adenomas. Three nuclear transcriptional factors, AP-1, CREB, and Pit-1, which are targets of protein kinase C and A, appear to play critical roles in both neoplastic growth and hormone secretion in hormone-producing adenomas. The alteration of G proteins such as Gs and Gi2 is a direct cause of the activation of such transcriptional factors. Autocrine growth factor/cytokine loops also contribute to the augmented signal transductions. Bromocriptine and somatostatin analogs have effects to lower cellular cAMP level through inhibitory G proteins, although the mechanism leading to cellular apoptosis is unknown. On the other hand, most non-functioning adenomas may not have PKC- or PKA-mediated oncogenic mechanisms. Although the loss of Rb and p27Kip1 genes has been demonstrated as a cause of murine pituitary adenomas, the role of tumor suppressor genes for human pituitary adenomas remains elusive. However, potential candidates for the suppressor genes are now emerging. The recently cloned multiple endocrine neoplasia type I gene is one example. Alterations of c-myc/bcl-2, and ras, although rare, appear to be an important cause of the process by which adenoma cells acquire aggressive phenotypes. Further studies on the links between abnormal signal transductions and aberrant tumor suppressor genes will be needed to clarify the whole picture of pituitary oncogenesis.

Proliferation, bcl-2 expression and angiogenesis in pituitary adenomas: relationship to tumour behaviour

The prediction of pituitary tumour behaviour, in terms of response to treatment from which can be derived optimal management strategies, is a challenge that has been approached using several different means. Angiogenesis in other tumour types has been shown to be correlated with poor response to treatment and tumour recurrence. The aim of this paper is to assess the role of measurements of cell proliferation and angiogenesis in predicting pituitary tumour behaviour. The proliferative capacity of the tumour was assessed using the Ki-67 labelling index (LI) while bcl-2 expression was used to assess anti-apoptotic pathways. The microvessel density (MVD) was assessed using antibodies to CD31 and factor VIII-related antigen, and with biotinylated ulex europaeus agglutinin I. There was no difference between Ki-67 LI and MVD of functionless tumours that recurred and those that did not, but bcl-2 expression was significantly lower in tumours that subsequently regrew. Macroprolactinomas had significantly higher LI than microprolactinomas and than all other tumours. Cell proliferation and angiogenesis were not related, showing that both processes are under different control mechanisms in pituitary tumours. In contrast there was a positive relationship between markers of angiogenesis and bcl-2 expression in prolactinomas, GH-secreting tumours and non-recurrent functionless tumours with higher levels of bcl-2 expression being found in the more vascular tumours. These findings may suggest that angiogenesis is related to the ability of tumour cells to survive rather than their proliferative activity.

Apoptosis in neuroendocrine tumours

Acquired resistance to apoptosis in neuroendocrine tumours (NETs) may promote clonal expansion and enhance the likelihood that subsequent mutations lead to growth or persistence of the neoplastic clone. Recent studies have demonstrated that deregulation of programmed cell death may be a critical component in multistep tumourigenesis of NETs and that the frequent expression of the Bcl-2 oncoprotein in these tumours may contribute to their pathogenesis. The genetic complementation of simultaneously deregulated Bcl-2 and c-Myc may be implicated in the multistep tumourigenesis of human NETs. Furthermore, because the efficacy of cytotoxic chemotherapy relies on its ability to induce programmed cell death, resistance to apoptosis typically correlates with chemoresistance, a phenomenon that is typical in NETs. Consideration of how oncogenes affect rates of cell death, in addition to augmenting growth, has already provided valuable insights into the biology of cancer. Understanding the molecular and cellular features of this process may enable the development and application of more effective and potentially curative treatment strategies in which the induction of programmed cell death is an integral component.

The effects of age and spontaneous adenoma formation on trophic activity in the rat pituitary gland: a comparison with trophic activity in the human pituitary and in human pituitary adenomas

The effects of ageing on trophic activity in the pituitary gland and the molecular events that underlie pituitary tumour formation are poorly understood. In the present study we have used an extremely accurate system to analyse trophic activity in human pituitary tumours and compared our findings with trophic activity in spontaneous rat pituitary adenomas and with changes in basal rates of turnover as the animals age. Thin, hematoxylin and eosin-stained pituitary sections from groups of male Wistar rats aged 6 weeks to 16 months, killed at 90-min intervals after receiving a single intraperitoneal bolus of colchicine to block cellular passage through mitosis, were evaluated histologically. Extremely accurate quantification of small changes in the prevalence of trophic events, and thus the rate of cell turnover, was achieved using a dedicated computerized aid to manual cell counting. Results were compared with the prevalence of mitotic activity in 24 spontaneous rat pituitary adenomas and with a series of 97 archival human pituitary adenomas and 24 normal human pituitary glands obtained at autopsy. In rats, average basal pituitary cell turnover declined by over 95% between 6 weeks and 16 months of age. Concurrent with this decline was a marked increase in the prevalence of adenoma formation. The prevalence of mitotic activity in spontaneous rat pituitary adenomas averaged almost twice that seen in normal, young rat pituitary and exceeded 16 times that seen in the pituitary of aged animals. In contrast, when compared to normal human pituitary tissue, average trophic activity in human pituitary adenomas remained extremely low.

Proliferation markers in different types of clinically non-secreting pituitary adenomas

160 clinically non-secreting pituitary adenomas were examined in regard to their expression of the markers PCNA, bcl2, Ki 67 in the mib-1 modification and p53 which are still under investigation for their relevance to cell proliferation. The series contained 60 null cell adenomas, 60 oncocytomas and 40 gonadotroph adenomas. The groups that showed a definitely negative and definitely positive staining were evaluated in regard to their further characteristics such as size, invasiveness and recurrence. PCNA showed a highly represented immunostaining index throughout the groups, but not correlation between the PCNA index and an increased recurrence rate could be found. The staining for bcl2 was only rarely positive and only in a small number of cells. No correlation with the clinical data could be seen. We found a significant higher rate of staining in the invasive adenomas in the group of null cell adenomas and oncocytomas for Ki 67, especially in those adenomas expressing p53. p53 positivity was restricted to the invasive adenomas but was found only in 20% of all invasive adenomas. These data confirm in a sufficiently large series of clinically endocrine inactive pituitary adenomas, that p53 and Ki67 immunohistology is useful in evaluating the aggressive behavior of clinically silent pituitary adenomas. Nevertheless, negative results do not exclude clinically relevant invasive behavior.

Apoptosis in nontumorous and neoplastic human pituitaries: expression of the Bcl-2 family of proteins

Analyses of apoptosis and of the apoptosis regulatory proteins Bcl-2, Bax, Bcl-X, and Bad were done in 95 nontumorous and neoplastic pituitary tissues by terminal deoxynucleotide transferase-mediated dUTP nick-end labeling (TUNEL), immunohistochemistry, and Western blotting. The apoptotic index was relatively low in all groups but was at least fourfold higher in pituitary carcinomas compared with any other groups. Pituitaries from pregnant and postpartum women had a fivefold higher apoptotic index compared with matched controls from nonpregnant females. Preoperative treatment of adenomas with octreotide or dopamine agonists did not change the apoptotic index significantly. The lowest levels of Bcl-2, Bax, and Bcl-X expression were in pituitary carcinomas as detected by immunostaining. An immortalized human pituitary adenoma cell line, HP75, developed in our laboratory using a replication-defective recombinant human adenovirus with an early large T-antigen, had a much higher level of apoptosis than nontumorous and neoplastic pituitaries. Treatment with transforming growth factor (TGF)-beta1 and protein kinase C (PKC) inhibitors increased apoptosis in this cell line. Analysis of the Bcl-2 family of proteins after treatment with TGF-beta1 and PKC inhibitors showed a 20% to 30% decrease in Bcl-X in the treated groups compared with controls. These results, which represent the first study of apoptosis in pituitaries from pregnant and postpartum cases and in pituitary carcinomas, indicate that 1) the apoptotic rate is low in nontumorous and neoplastic pituitary tissues but is relatively higher in pituitary carcinomas, 2) there are alterations in the expression of the Bcl-2 family of proteins in pituitary neoplasms with a decrease in Bcl-2 expression in pituitary carcinomas that may contribute to pituitary tumor pathogenesis and/or proliferation, and 3) cultured pituitary tumor cells respond to TGF-beta1 and PKC inhibitors by undergoing apoptotic cell death.

Bcl-2 and c-Myc, but not bax and p53, are expressed during human medullary thyroid tumorigenesis

Medullary thyroid carcinoma (MTC) is a tumor of parafollicular cells of the thyroid gland. It has served as a useful experimental model for the study of tumor proliferation and differentiation. Although recent studies have identified the gene involved in familial forms of MTC, little is known about the molecular pathogenesis of the sporadic variants of this tumor. It has become increasingly clear that deregulation of programmed cell death is a critical component in multistep tumorigenesis. The present investigation was undertaken to determine whether similar molecular events occur in human MTC. Eighteen MTCs from 18 patients (including 12 sporadic and six familial cases and one metastatic lymph gland) and a MTC cell line (TT cells) were used in this study for detecting the expression of apoptosis-regulatory genes bcl-2, bax, c-myc, and p53. Immunohistochemical results showed that all MTC tumor samples displayed Bcl-2 and c-Myc immunoreactivity, whereas only 4 and 2 tumors showed a minority of cells positive for Bax and p53, respectively. Western and Northern blotting showed high levels of 26-kd Bcl-2 protein and bcl-2 transcript. The co-expression of Bcl-2 and c-Myc was also detected in the TT cells by indirect fluorescence immunohistochemistry and Western blotting. Moreover, Bcl-2 immunoreactivity was also found in C-cell hyperplasia from familial patients indicating that expression of this oncogene may represent an early event in the pathogenesis of MTC. The present study suggests that deregulation of programmed cell death may be a critical component in multistep tumorigenesis of MTC and that the frequent expression of the Bcl-2 oncoprotein in these tumors may contribute to their pathogenesis. The genetic complementation of simultaneously deregulated bcl-2 and c-myc may be implicated in the multistep tumorigenesis of human MTC.

Expression of apoptosis-suppressing gene bcl-2 in human carotid body tumours

That carotid body tumours have a genetic aetiology is suggested by the familial occurrence of the neoplasm. Environmental influences are also implied by the fact that the tumour is more common in those living at high altitudes. However, the mechanism of development of sporadic tumours occurring at sea level, which account for the majority of cases, remains unknown. It has become increasingly clear that the deregulation of programmed cell death is a critical component in multistep tumourigenesis. Previous studies have demonstrated a high frequency of bcl-2 expression in the tumours arising from cells derived from the neural crest and tumour cell lines of neural origin. This investigation was undertaken to determine whether similar molecular events occur in human carotid body tumours. Western and Northern analysis revealed that the tumours expressed the 26 kD protein and bcl-2 transcripts. Immunoperoxidase staining, using a monoclonal anti-bcl-2 antibody, revealed that 11 out of 13 specimens stained positively for bcl-2. These results suggest that the deregulation of programmed cell death may be a critical component in the multistep tumourigenesis of carotid body tumours and that the expression of oncoprotein bcl-2 may contribute to the generation of such tumours.