Analysis of epidermal growth factor receptor and activated epidermal growth factor receptor expression in pituitary adenomas and carcinomas

Strategy for Identifying a Robust Metabolomic Signature Reveals the Altered Lipid Metabolism in Pituitary Adenoma

Despite the well-established connection between systematic metabolic abnormalities and the pathophysiology of pituitary adenoma (PA), current metabolomic studies have reported an extremely limited number of metabolites associated with PA. Moreover, there was very little consistency in the identified metabolite signatures, resulting in a lack of robust metabolic biomarkers for the diagnosis and treatment of PA. Herein, we performed a global untargeted plasma metabolomic profiling on PA and identified a highly robust metabolomic signature based on a strategy. Specifically, this strategy is unique in (1) integrating repeated random sampling and a consensus evaluation-based feature selection algorithm and (2) evaluating the consistency of metabolomic signatures among different sample groups. This strategy demonstrated superior robustness and stronger discriminative ability compared with that of other feature selection methods including Student's t-test, partial least-squares-discriminant analysis, support vector machine recursive feature elimination, and random forest recursive feature elimination. More importantly, a highly robust metabolomic signature comprising 45 PA-specific differential metabolites was identified. Moreover, metabolite set enrichment analysis of these potential metabolic biomarkers revealed altered lipid metabolism in PA. In conclusion, our findings contribute to a better understanding of the metabolic changes in PA and may have implications for the development of diagnostic and therapeutic approaches targeting lipid metabolism in PA. We believe that the proposed strategy serves as a valuable tool for screening robust, discriminating metabolic features in the field of metabolomics.

Aggressive and Metastatic Pituitary Neuroendocrine Tumors: Therapeutic Management and Off-Label Drug Use

Pituitary neuroendocrine tumors (PitNETs) are the most common pituitary tumors and the second most common brain tumors. Although the vast majority (>90%) are benign, a small percentage (<2%) are aggressive. These aggressive PitNETs (AgPitNETs) are defined by the presence of radiological invasion, a high rate of cell proliferation, resistance to conventional treatments, and/or a high propensity for recurrence. Lastly, there are the rare pituitary carcinomas, also known as metastatic PitNETs (MetPitNETs), which account for only 0.2% of cases and are defined by the presence of craniospinal or distant metastases. At present, there are no definitive factors that allow us to predict with certainty the aggressive behavior of PitNETs, making the therapeutic management of AgPitNETs a real challenge. Surgery is considered the first-line treatment for AgPitNETs and MetPitNETs. Radiation therapy can be effective in controlling tumor growth and regulating hormone hypersecretion. Currently, there are no approved non-endocrine medical therapies for the management of AgPitNETs/MetPitNETs, mainly due to the lack of randomized controlled clinical trials. As a result, many of the medical therapies used are off-label drugs, and several are under investigation. Temozolomide (TMZ) is now recognized as the primary medical treatment following the failure of standard therapy (medical treatment, surgery, and radiotherapy) in AgPitNETs/MetPitNETs due to its ability to improve overall and progression-free survival rates in responding patients over 5 years. Other therapeutic options include pituitary-targeted therapies (dopamine agonists and somatostatin analogs), hormonal antisecretory drugs, non-hormonal targeted therapies, radionuclide treatments, and immunotherapy. However, the number of patients who have undergone these treatments is limited, and the results obtained to date have been inconsistent. As a result, it is imperative to expand the cohort of patients undergoing treatment to better determine the therapeutic efficacy and safety of these drugs for individuals with AgPitNETs/MetPitNETs.

Towards precision medicine for clinically non-functioning pituitary tumours

OBJECTIVE

Clinically non-functioning pituitary tumours (NFPT) are a heterogenous group of neoplasms with diverse outcomes. The purpose of this narrative review was to summarize available data on predictive factors, both in routine practice and research settings.

DESIGN

A literature review was conducted for papers published in peer-reviewed journals, investigating clinical, radiological, pathological and genetic predictive factors in NFPT.

RESULTS

Several clinical and radiological factors have been associated with NFPT recurrence and/or aggressiveness, including larger size and pre-/post-operative growth rates. Application of transcription factor immunohistochemistry has given rise to improved subtype identification, including 'higher-risk' subtypes, in routine clinical practice. Numerous other pathological and genetic biomarkers have demonstrated promise for prognostication in the research setting.

CONCLUSION

NFPT are a heterogenous group of tumours, characterized by diverse presentation, pathogenesis and outcomes. Ongoing refinements in understanding of tumour biology are likely to pave the way to improved integrative prognostication and precision medicine for NFPT.

Phosphorylated EGFR (pEGFR T693) as a Novel Predictor of Recurrence in Non-Functioning Pituitary Adenomas

PURPOSE

Non-functioning pituitary adenomas (NFPAs) exhibit high recurrence rates after surgery. However, the determinants of recurrence are inconsistent in the available literature. The present study sought to investigate the association between nuclear phosphorylated EGFR (pEGFR) levels and recurrence of NFPAs.

METHODS

Tissue microarrays from patients undergoing adenomectomy for NFPAs at our tertiary care center from 2003 to 2015 and having a minimum of 60 months of follow-up (n=102) were accessed. Immunohistochemical analysis (IHC) was performed to determine the expression of nuclear pEGFR T693. h-score was calculated as the product of staining intensity and the number of positively staining cells. Radiological surveillance (MRI) was performed to categorize NFPAs as recurrent or non-recurrent on follow-up.

RESULTS

The mean age of the cohort was 50 ± 11 years with a male preponderance (61.1%). Recurrence was observed in 46.1% of the patients at a median of 123 months (IQR 72-159) of follow-up. pEGFR T693 positivity was higher in a significantly greater number of recurrent NFPAs as compared to non-recurrent NFPAs (95.7% vs 81%, p=0.02). h-scores were also significantly higher in recurrent NFPAs (122.1 ± 6 vs 81.54 ± 3.3, p<0.0001). pEGFR T693 positivity significantly predicted recurrence in NFPAs (HR=4.9, CI 2.8-8.8, p<0.0001). ROC analysis revealed an h-score cutoff of 89.8 as being associated significantly with recurrence (sensitivity 80%, specificity 78%, AUC 0.84, p<0.0001).

CONCLUSION

pEGFR T693 was expressed in significantly higher number of recurrent NFPAs. The h-scores were also higher in recurrent NFPAs. Nuclear pEGFR T693 may serve as a predictor of recurrence in NFPAs.

A pituitary metastasis, an adenoma and potential hypophysitis: A case report of tumour to tumour metastasis in the pituitary

Tumour to tumour metastasis is a rare event, especially in the pituitary. Metastases to pituitary adenomas most commonly occurs in late stage disease, commonly presenting with visual field defects and adenohypophyseal dysfunction. The most frequent primary cancers are lung, breast and renal carcinoma which deposit most commonly in prolactinomas, somatotropinomas, gonadotropinomas. In nearly 40% of cases, sellar symptoms are the harbinger to the diagnosis of primary malignancy. The abnormal vascularity and growth promoting microenvironment of pituitary adenomas may encourage metastatic seeding and proliferation of these "collision tumours". Here, we present a case of a breast carcinoma metastasis to a pituitary null-cell adenoma in the setting of immunotherapy. Infundibular thickening in the setting of immunotherapy is often ascribed to hypophysitis, but our case highlights that metastatic spread should be part of the differential diagnosis.

Exploring the Role of Novel Medical Therapies for Aggressive Pituitary Tumors: A Review of the Literature-"Are We There Yet?"

Aggressive pituitary tumors account for up to 10% of pituitary tumors and are characterized by resistance to medical treatment and multiple recurrences despite standard therapies, including surgery, radiotherapy, and chemotherapy. They are associated with increased morbidity and mortality, particularly pituitary carcinomas, which have mortality rates of up to 66% at 1 year after diagnosis. Novel targeted therapies under investigation include mammalian target of rapamycin (mTOR), tyrosine kinase, and vascular endothelial growth factor (VEGF) inhibitors. More recently, immune checkpoint inhibitors have been proposed as a potential treatment option for pituitary tumors. An increased understanding of the molecular pathogenesis of aggressive pituitary tumors is required to identify potential biomarkers and therapeutic targets. This review discusses novel approaches to the management of aggressive pituitary tumors and the role of molecular profiling.

Medical Management of Cushing's Syndrome: Current and Emerging Treatments

Endogenous Cushing's syndrome is a chronic disease associated with increased morbidity and mortality if not appropriately treated. Recurrence and/or persistence of hypercortisolemia after surgical treatment, especially for Cushing's disease, are high, and long-term medical treatment is used to decrease cortisol levels and risk of metabolic comorbidities. Medical treatment is also often required while waiting for radiation effects to take place. In some cases, severe or life-threatening hypercortisolism must be urgently and medically treated, via intravenous medications or with combination therapy, before patients can undergo surgery. In the last decade, medical treatment has progressed from a few steroidogenesis inhibitors to three novel drug groups: new inhibitors for steroidogenic enzymes with possibly fewer side effects, pituitary-directed drugs that aim to inhibit the pathophysiological pathways of Cushing's disease, and glucocorticoid receptor antagonists that block cortisol's action. Understanding the pathophysiology of Cushing's syndrome has also led to the identification of potential targets that may decrease adrenocorticotrophic hormone and/or cortisol excess, and/or decrease tumor cell proliferation, and induce senescence or apoptosis. We provide here a review of current and near-future medical options to treat Cushing's syndrome, and discuss updates on clinical trials and the efficacy and safety of novel or in-development drugs, as well as future potential targets.

Emerging Role of USP8, HMGA, and Non-Coding RNAs in Pituitary Tumorigenesis

Two novel molecular mechanisms with a driver role in pituitary tumorigenesis have been recently identified. They are (a) mutations in the Ubiquitin-Specific Protease 8 (USP8) gene in corticotroph tumors and (b) overexpression of the HMGA1 and HMGA2 genes in most of the pituitary tumors. Moreover, deregulated expression of the non-coding RNAs has been very frequently observed in this neoplasia. The aim of this review is to better elucidate the role, the mechanisms, and the possible clinical impact of these novel alterations in the development of pituitary neoplasia.

Immunotherapy and potential molecular targets for the treatment of pituitary adenomas resistant to standard therapy: a critical review of potential therapeutic targets and current developments

INTRODUCTION

Pituitary adenomas (PAs) are primary central nervous system (CNS) tumors, accounting for as much as 25% of intracranial neoplasms. Although existing remedies show success in treating most PAs, treatment of invasive and non-functioning PAs, in addition to functioning PAs unresponsive to standard therapy, remains challenging. With the continually increasing understanding of biochemical pathways involved in tumorigenesis, immunotherapy stands as a promising alternative therapy for pituitary tumors that are resistant to standard therapy.

EVIDENCE ACQUISITION

A literature search was conducted of the PubMed database for immunotherapies of PAs. The search yielded a total of 2621 articles, 26 of which were included in our discussion.

EVIDENCE SYNTHESIS

Several pathologically expressed molecules could potentially serve as promising targets of current or future immunotherapies for PAs. Programmed death ligand-1, matrix metalloproteinases, EpCAM (Trop1) and Trop2, cancer-testis antigen MAGE-A3, epidermal growth factor receptor (EGFR), folate receptor alpha, vascular endothelial growth factor, and galectin-3 have all been implicated as crucial factors involved with tumor survival and invasion. Inhibition of these pathways may prove efficacious in the management of invasive and treatment-resistant PAs.

CONCLUSIONS

Rapid advancements in tumor immunology may increase the probability of successful treatment of PAs by exploitation of the normal immune response or by targeting novel proteins. Current research on many of the targets reviewed in this article are successfully being utilized to manage various neoplastic disease including CNS tumors. These therapies may eventually play a key role in the treatment of PAs that do not respond to standard therapy.

Effects of miR‑138‑5p and miR‑204‑5p on the migration and proliferation of gastric cancer cells by targeting EGFR

GC (gastric cancer) remains one of the most lethal malignancies worldwide. EGFR (epidermal growth factor receptor) plays an important role in the malignant process of GC, therefore, the present study addressed the relationship between EGFR and its potential regulators and examined their regulatory mechanisms in GC. We examined differences in the expression levels of EGFR in GC and adjacent non‑cancerous tissues. Bioinformatics analyses and dual luciferase reporter assays were used to confirm the putative relationship between miR‑138 or miR‑204 and EGFR, and their relationship was further detected using western blotting, RT‑PCR, and a series of cell studies. EGFR proteins were abundantly expressed in GC tissues, however EGFR mRNA levels remained indistinctive. Consequently, EGFR was revealed as a putative target of miR‑138 and miR‑204 which bound to the 3'UTR of EGFR mRNA. Further analysis revealed that miR‑138 and miR‑204 were significantly downregulated in GC tissues and the overexpression of miR‑138 and miR‑204 in GC cell lines resulted in the significant inhibition of EGFR protein levels and GC cell proliferation and metastasis. Rescue experiments confirmed that the roles of the two microRNAs were specific to EGFR. EGFR is a pivotal oncogene in GC progression that may be regulated by miR‑138 and miR‑204.

Pathogenesis of non-functioning pituitary adenomas

The pathogenesis of non functioning pituitary adenomas (NFPA) is a complex process involving several factors, from molecular to genetic and epigenetic modifications, where tumor suppressor genes, oncogenes, cell cycle derangements have been demonstrated to play an important role. MicroRNAs (miRNAs) have also been identified as possible players in NFPA tumorigenesis and pituitary stem cells have been investigated for their potential role in pituitary tumor initiation. However, a critical role for paracrine signalling has also been highlighted. This review focuses on the current knowledge on the involvement of these factors in NFPA pathogenesis.

Pituitary-Directed Therapies for Cushing's Disease

Cushing's disease (CD) is caused by a pituitary corticotroph neuroendocrine tumor inducing uncontrolled hypercortisolism. Transsphenoidal surgery is the first-line treatment in most cases. Nonetheless, some patients will not achieve cure even in expert hands, others may not be surgical candidates and a significant percentage will experience recurrence. Many patients will thus require medical therapy to achieve disease control. Pharmacologic options to treat CD have increased in recent years, with an explosion in knowledge related to pathophysiology at the molecular level. In this review, we focus on medications targeting specifically pituitary adrenocorticotropic hormone-secreting tumors. The only medication in this group approved for the treatment of CD is pasireotide, a somatostatin receptor ligand. Cabergoline and temozolomide may also be used in select cases. Previously studied and abandoned medical options are briefly discussed, and emphasis is made on upcoming medications. Mechanism of action and available data on efficacy and safety of cell cycle inhibitor roscovitine, epidermal growth factor receptor inhibitor gefitinib, retinoic acid, and silibinin, a heat shock protein 90 inhibitor are also presented.

Trophic and neurotrophic factors in human pituitary adenomas (Review)

The pituitary gland is an organ that functionally connects the hypothalamus with the peripheral organs. The pituitary gland is an important regulator of body homeostasis during development, stress, and other processes. Pituitary adenomas are a group of tumors arising from the pituitary gland: they may be subdivided in functional or non-functional, depending on their hormonal activity. Some trophic and neurotrophic factors seem to play a key role in the development and maintenance of the pituitary function and in the regulation of hypothalamo-pituitary-adrenocortical axis activity. Several lines of evidence suggest that trophic and neurotrophic factors may be involved in pituitary function, thus suggesting a possible role of the trophic and neurotrophic factors in the normal development of pituitary gland and in the progression of pituitary adenomas. Additional studies might be necessary to better explain the biological role of these molecules in the development and progression of this type of tumor. In this review, in light of the available literature, data on the following neurotrophic factors are discussed: ciliary neurotrophic factor (CNTF), transforming growth factors β (TGF‑β), glial cell line-derived neurotrophic factor (GDNF), nerve growth factor (NGF), vascular endothelial growth factor (VEGF), vascular endothelial growth inhibitor (VEGI), fibroblast growth factors (FGFs) and epidermal growth factor (EGF) which influence the proliferation and growth of pituitary adenomas.

Pituitary stem cell regulation: who is pulling the strings?

The pituitary gland plays a pivotal role in the endocrine system, steering fundamental processes of growth, metabolism, reproduction and coping with stress. The adult pituitary contains resident stem cells, which are highly quiescent in homeostatic conditions. However, the cells show marked signs of activation during processes of increased cell remodeling in the gland, including maturation at neonatal age, adaptation to physiological demands, regeneration upon injury and growth of local tumors. Although functions of pituitary stem cells are slowly but gradually uncovered, their regulation largely remains virgin territory. Since postnatal stem cells in general reiterate embryonic developmental pathways, attention is first being given to regulatory networks involved in pituitary embryogenesis. Here, we give an overview of the current knowledge on the NOTCH, WNT, epithelial-mesenchymal transition, SHH and Hippo pathways in the pituitary stem/progenitor cell compartment during various (activation) conditions from embryonic over neonatal to adult age. Most information comes from expression analyses of molecular components belonging to these networks, whereas functional extrapolation is still very limited. From this overview, it emerges that the 'big five' embryonic pathways are indeed reiterated in the stem cells of the 'lazy' homeostatic postnatal pituitary, further magnified en route to activation in more energetic, physiological and pathological remodeling conditions. Increasing the knowledge on the molecular players that pull the regulatory strings of the pituitary stem cells will not only provide further fundamental insight in postnatal pituitary homeostasis and activation, but also clues toward the development of regenerative ideas for improving treatment of pituitary deficiency and tumors.

Recent advances in understanding Cushing disease: resistance to glucocorticoid negative feedback and somatic USP8 mutations

Cushing’s disease is a rare disease with a characteristic phenotype due to significant hypercortisolism driven by over-secretion of adrenocorticotropic hormone and to high morbidity and mortality if untreated. It is caused by a corticotroph adenoma of the pituitary, but the exact mechanisms leading to tumorigenesis are not clear. Recent advances in molecular biology such as the discovery of somatic mutations of the ubiquitin-specific peptidase 8 ( USP8) gene allow new insights into the pathogenesis, which could be translated into exciting and much-needed therapeutic applications.

The Stem Cell Connection of Pituitary Tumors

Tumors in the pituitary gland are typically benign but cause serious morbidity due to compression of neighboring structures and hormonal disruptions. Overall, therapy efficiency remains suboptimal with negative impact on health and comfort of life, including considerable risk of therapy resistance and tumor recurrence. To date, little is known on the pathogenesis of pituitary tumors. Stem cells may represent important forces in this process. The pituitary tumors may contain a driving tumor stem cell population while the resident tissue stem cells may be directly or indirectly linked to tumor development and growth. Here, we will briefly summarize recent studies that afforded a glance behind the scenes of this stem cell connection. A better knowledge of the mechanisms underlying pituitary tumorigenesis is essential to identify more efficacious treatment modalities and improve clinical management.

Microarray technology reveals potentially novel genes and pathways involved in non-functioning pituitary adenomas

Microarray data of non-functioning pituitary adenomas (NFPAs) were analyzed to disclose novel genes and pathways involved in NFPA tumorigenesis. Raw microarray data were downloaded from Gene Expression Omnibus. Data pre-treatment and differential analysis were conducted using packages in R. Functional and pathway enrichment analyses were performed using package GOs-tats. A protein-protein interaction (PPI) network was constructed using server STRING and Cytoscape. Known genes involved in pituitary adenomas (PAs), were obtained from the Comparative Toxicogenomics Database. A total of 604 differentially expressed genes (DEGs) were identifed between NFPAs and controls, including 177 up- and 427 down-regulated genes. Jak-STAT and p53 signaling pathways were significantly enriched by DEGs. The PPI network of DEGs was constructed, containing 99 up- and 288 down-regulated known disease genes (e.g. EGFR and ESR1) as well as 16 up- and 17 down-regulated potential novel NFPAs-related genes (e.g. COL4A5, LHX3, MSN, and GHSR). Genes like COL4A5, LHX3, MSN, and GHSR and pathways such as p53 signaling and Jak-STAT signaling, might participate in NFPA development. Although further validations are required, these findings might provide guidance for future basic and therapy researches.

Genetic aspects of pituitary carcinoma: A systematic review

BACKGROUND

Pituitary carcinoma (PC) is a rare type of malignant intracranial neoplasm defined as distant metastasis of pituitary adenoma (PA). Although PC incidence is low because only 0.1% to 0.2% of PAs ultimately develop into PCs, the prognosis is poor and 66% of patients die within the first year. Existing therapeutic measures, including surgical removal, chemotherapy, and radiotherapy, have limited effectiveness. The lack of efficacy of current treatments is largely caused by the limited understanding of the molecular pathogenesis of PA and the malignant transformation to PC. Therefore, the aim of this systematic review was to summarize published research regarding gene and protein expression in PC to clarify the molecular mechanisms underlying PC genesis and development and identify new candidate diagnostic biomarkers and therapeutic targets for potential use in personalized treatment of PC.

METHODS

We followed the PRISMA guidelines to plan and conduct this systematic review. PubMed, Embase, and Web of Science databases were searched for relevant studies conducted before December 16, 2015 describing the association of PC with gene expression at the mRNA and protein levels. MeSH terms combined with free terms were used to retrieve the references.

RESULTS

In total, 207 records were obtained by primary search, and 32 were included in the systematic review. Compared with normal pituitary gland and/or PA, 30 and 18 genes were found to have higher or lower expression, respectively, in PCs using different analytical methods. Among them, we selected 9 upregulated and 7 downregulated genes for further analysis based on their identification as candidate treatment targets in other cancers, potential clinical application, or further research value.

CONCLUSION

Previous studies demonstrated that many genes promote PC malignant transformation, angiogenesis, invasion, metastasis, and recurrence. Although most of these genes and proteins have not been fully analyzed with regard to their downstream mechanisms or potential diagnostic and therapeutic application, they have the potential to become candidate PC biomarkers and/or molecular targets for guiding personalized treatment. Modern advanced technologies should be utilized in future research to identify more candidate genes for PC pathogenesis, as precisely targeted gene therapies against PC are urgently required.

Over-expression of LRIG1 suppresses biological function of pituitary adenoma via attenuation of PI3K/AKT and Ras/Raf/ERK pathways in vivo and in vitro

Pituitary adenomas (PAs) are well known as a common intracranial benign tumor, and a portion of PAs are refractory to current therapeutic methods. ErbB receptors family signaling pathway regulates the expression of PAs activation associated gene. Inhibition of epidermal growth factor receptor (EGFR) can inhibit proliferation of PAs. Leucine-rich repeats and immunoglobulin-like domains protein 1 ( LRIG1), a negative mediated gene of ErbB receptors family, plays a role in many tumors. However, there are seldom researches about the functional role of LRIG1 in PAs. The aim of this study is to explore the potential effect of LRIG1 and its regulating mechanism in PAs. First, we investigated the role of LRIG1 in cell migration, invasion of PAs with transfected LRIG1 or control. Then, we explored its impact on cell proliferation and apoptosis of PAs in vivo. To study the regulating mechanism of LRIG1, we examined the expression of molecular factor of PI3K/AKT and Ras/Raf/ERK pathway using Western blotting in vitro and RT-PCR in vitro and in vivo. It was found that LRIG1 over-expression inhibited cell migration, invasion and proliferation, and promoted apoptosis of PAs in vivo and in vitro. Furthermore, LRIG1 suppressed the expression of signaling of PI3K/AKT and Ras/Raf/ERK pathways in PAs. LRIG1, as a negative mediated gene of tumor, can inhibit biological function of PAs via inhibiting PI3K/AKT and Ras/Raf/ERK pathways, and it might be a new target for gene therapy of PAs.

Biomarkers of pituitary carcinomas

Pituitary carcinoma is a rare tumor originating from adenohypophyseal cells. Currently, diverse pathogenetic mechanisms, i.e. de novo versus malignant transformation from pituitary adenoma, remain obscure and require further investigation. During the last two decades, scientific research added new horizons not only in regards to general tumor concepts but also in next generation biomarker armamentarium that sheds light on alternate pathways in carcinogenesis. Areas covered: In this review, the impact of apoptotic and proliferative markers, angiogenesis, telomerase activity, H-ras, HIF-1, HER-2/neu, Rb gene, and microRNAs in pathogenetic mechanisms of pituitary carcinomas were revised. Expert commentary: It is becoming increasingly important for the need of standardization of new biomarkers but also for better comprehension of the diverse pathways in tumorigenesis. This can only be accomplished by tapping into the continuously expanding spectrum of new biomarkers.

Genetics of Cushing's disease: an update

INTRODUCTION

Cushing's disease (CD) results from uncontrolled hypercortisolism induced by ACTH-secreting corticotroph adenomas; accordingly, patients diagnosed with CD usually present several comorbidities and an increased risk of mortality. Hypothesis-driven screenings have led to identification of rare alterations in a low number of patients, although the genetic basis underlying CD has remained unclear until recently. Using whole-exome sequencing, recurrent mutations have been reported in the gene coding for the ubiquitin-specific protease 8 (USP8), a protein with deubiquitinase (DUB) activity that modulates the lysosomal turnover of the EGF receptor (EGFR) and other membrane proteins.

METHODS

In this review, we summarize the recent genetic findings and discuss the clinical and pathological implications of USP8 deregulation in corticotroph adenomas.

CONCLUSIONS

Mutations in USP8 have been identified in 35-62 % of functional sporadic corticotroph adenomas causing Cushing's disease, but not in any other type of pituitary tumor. These mutations are found mostly in adult female patients and lead to an aberrant DUB activation by impairing the regulation of USP8 by members of the 14-3-3 family of proteins. The consequence of this hyperactivation is a longer retention of EGFR at the plasma membrane which promotes an enhanced production of ACTH.

The New Molecular Landscape of Cushing's Disease

Cushing's disease (CD) is caused by corticotropin-secreting pituitary adenomas and results in substantial morbidity and mortality. Its molecular basis has remained poorly understood until the past few years, when several proteins and genes [such as testicular orphan nuclear receptor 4 (TR4) and heat shock protein 90 (HSP90)] were found to play key roles in the disease. Most recently, mutations in the gene of ubiquitin-specific peptidase 8 (USP8) increasing its deubiquination activity were discovered in a high percentage of corticotroph adenomas. Here, we will discuss emerging insights in the molecular alterations that finally result in CD. The therapeutic potential of these findings needs to be carefully evaluated in the near future, hopefully resulting in new treatment options for this devastating disorder.

Decoding the genetic basis of Cushing's disease: USP8 in the spotlight

Cushing's disease (CD) arises from pituitary-dependent glucocorticoid excess due to an ACTH-secreting corticotroph tumor. Genetic hits in oncogenes and tumor suppressor genes that afflict other pituitary tumor subtypes are not found in corticotrophinomas. Recently, a somatic mutational hotspot was found in up to half of corticotrophinomas in the USP8 gene that encodes a protein that impairs the downregulation of the epidermal growth factor receptor (EGFR) and enables its constitutive signaling. EGF is an important regulator of corticotroph function and its receptor is highly expressed in Cushing's pituitary tumors, where it leads to increased ACTH synthesis in vitro and in vivo. The mutational hotspot found in corticotrophinomas hyper-activates USP8, enabling it to rescue EGFR from lysosomal degradation and ensure its stimulatory signaling. This review presents new developments in the study of the genetics of CD and focuses on the USP8-EGFR system as trigger and target of corticotroph tumorigenesis.

Prolactinoma ErbB receptor expression and targeted therapy for aggressive tumors

As ErbB signaling is a determinant of prolactin synthesis, role of ErbB receptors was tested for prolactinoma outcomes and therapy. The objective of this study was to characterize ErbB receptor expression in prolactinomas and then perform a pilot study treating resistant prolactinomas with a targeted tyrosine kinase inhibitor (TKI). Retrospective analysis of prolactinomas and pilot study for dopamine agonist resistant prolactinomas in tertiary referral center. We performed immunofluorescent staining of a tissue array of 29 resected prolactinoma tissues for EGFR, ErbB2, ErbB3, and ErbB4 correlated with clinical features. Two patients with aggressive resistant prolactinomas enrolled and completed trial. They received lapatinib 1,250 mg daily for 6 months with tumor and hormone assessments. Main outcome measures were positive tumor staining of respective ErbB receptors, therapeutic reduction of prolactin levels and tumor shrinkage. Treated PRL levels and tumor volumes were suppressed in both subjects treated with TKI. EGFR expression was positive in 82 % of adenomas, ErbB2 in 92 %, ErbB3 in 25 %, and ErbB4 in 71 %, with ErbB2 score > EGFR > ErbB4 > ErbB3. Higher ErbB3 expression was associated with optic chiasm compression (p = 0.03), suprasellar extension (p = 0.04), and carotid artery encasement (p = 0.01). Higher DA response rates were observed in tumors with higher ErbB3 expression. Prolactinoma expression of specific ErbB receptors is associated with tumor invasion, symptoms, and response to dopamine agonists. Targeting ErbB receptors may be effective therapy in patients with resistant prolactinomas.

Co-expression network analysis of differentially expressed genes associated with metastasis in prolactin pituitary tumors

The aim of the present study was to construct a co‑expression network of differently expressed genes (DEGs) in prolactin pituitary (PRL) tumor metastasis. The gene expression profile, GSE22812 was downloaded from the Gene Expression Omnibus database, and including five non‑invasive, two invasive and six aggressive‑invasive PRL tumor samples. Compared with non‑invasive samples, DEGs were identified in invasive and aggressive‑invasive samples using a limma package in R language. The expression values of DEGs were hierarchically clustered. Next, Gene Ontology (GO) function enrichment and Kyoto Encyclopedia of Genes and Genomes pathway analysis of DEGs were performed via The Database for Annotation, Visualization and Integrated Discovery. Finally, gene pairs of DEGs between non‑invasive and aggressive‑invasive samples were identified using the Spearman cor( ) function in R language. Compared with the non‑invasive samples, 61 and 89 DEGs were obtained from invasive and aggressive‑invasive samples, respectively. Cluster analysis showed that four genes were shared by the two samples, including upregulated solute carrier family 2, facilitated glucose transporter member 11 (SLC2A11) and teneurin transmembrane protein 1 (TENM1) and downregulated importin 7 (IPO7) and chromogranin B (CHGB). In the invasive samples, the most significant GO terms responded to cyclic adenosine monophosphate and a glucocorticoid stimulus. However, this occurred in the cell cycle, and was in response to hormone stimulation in aggressive‑invasive samples. The co‑expression network of DEGs showed different gene pairs and modules, and SLC2A11 and CHGB occurred in two co‑expression networks within different co‑expressed pairs. In the present study, the co‑expression network was constructed using bioinformatics methods. SLC2A11, TENM1, IPO7 and CHGB are hypothesized to be closely associated with metastasis of PRL. Furthermore, CHGB and SLC2A11 may be significant in PRL tumor progression and serve as molecular biomarkers for PRL tumors. However, further investigation is required to confirm the current results.

A new medical therapy for Cushing disease?

Members of the ErbB family of cell surface tyrosine kinase receptors are important targets for cancer treatment because they frequently contribute to the pathogenesis of malignancy. In this issue of the JCI, Fukuoka et al. generate data that suggest that using a tyrosine kinase inhibitor (TKI) against epidermal growth factor receptor (EGFR; also known as ErbB1) may be a novel approach for treating patients with hypercortisolemia due to pituitary corticotroph adenomas (Cushing disease). While surgical resection remains the cornerstone of treatment for individuals with such tumors, this study suggests that TKIs could perhaps be used to reduce tumor size prior to surgery or to treat recurrent disease after surgery.

EGFR as a therapeutic target for human, canine, and mouse ACTH-secreting pituitary adenomas

Cushing disease is a condition in which the pituitary gland releases excessive adrenocorticotropic hormone (ACTH) as a result of an adenoma arising from the ACTH-secreting cells in the anterior pituitary. ACTH-secreting pituitary adenomas lead to hypercortisolemia and cause significant morbidity and mortality. Pituitary-directed medications are mostly ineffective, and new treatment options are needed. As these tumors express EGFR, we tested whether EGFR might provide a therapeutic target for Cushing disease. Here, we show that in surgically resected human and canine corticotroph cultured tumors, blocking EGFR suppressed expression of proopiomelanocortin (POMC), the ACTH precursor. In mouse corticotroph EGFR transfectants, ACTH secretion was enhanced, and EGF increased Pomc promoter activity, an effect that was dependent on MAPK. Blocking EGFR activity with gefitinib, an EGFR tyrosine kinase inhibitor, attenuated Pomc expression, inhibited corticotroph tumor cell proliferation, and induced apoptosis. As predominantly nuclear EGFR expression was observed in canine and human corticotroph tumors, we preferentially targeted EGFR to mouse corticotroph cell nuclei, which resulted in higher Pomc expression and ACTH secretion, both of which were inhibited by gefitinib. In athymic nude mice, EGFR overexpression enhanced the growth of explanted ACTH-secreting tumors and further elevated serum corticosterone levels. Gefitinib treatment decreased both tumor size and corticosterone levels; it also reversed signs of hypercortisolemia, including elevated glucose levels and excess omental fat. These results indicate that inhibiting EGFR signaling may be a novel strategy for treating Cushing disease.

Expression and function of ErbB receptors and ligands in the pituitary

The role of ErbB family in discreet pituitary functions is reviewed. Several ErbB receptor ligands, EGF, TGFα, and heregulin are differentially expressed in normal gonadotroph and lacto-somatotroph lineages, and other elements of the anterior pituitary. ErbB receptors, i.e. EGFR and ErbB2, are also localized to the anterior pituitary with preferential EGFR lactosomatotroph expression. EGF regulates CRH and ACTH secretion and corticotroph proliferation as well as exhibiting autocrine and paracrine effects on gonadotrophs and on lactosomatotroph proliferation, gene and protein expression, and hormonal secretion. EGF and EGFR are expressed in both functioning and non-functioning pituitary adenomas, with higher expression in more aggressive tumor subtypes. ErbB2 receptor is detected in all tumor subtypes, particularly in invasive tumors. ErbB tyrosine kinase inhibitors regulate hormonal secretion, cell morphology, and proliferation in lacto-somatotroph tumors, reflecting the emerging application of targeted pituitary therapeutics.

Association of expression of Leucine-rich repeats and immunoglobulin-like domains 2 gene with invasiveness of pituitary adenoma

The Leucine-rich repeats and immunoglobulin-like domains-2 (LRIG2) gene expression in pituitary adenoma and its correlation with tumor invasiveness were studied. The expression of LRIG2 mRNA and protein in human pituitary adenoma obtained surgically was detected by RT-PCR (39 cases) and immunohistochemical staining (30 cases). It was found that LRIG2 was mostly localized at the nucleus of the pituitary adenoma cells. Its expression was significantly higher in the invasive cases than in the non-invasive cases. LRIG2 protein was positive in 14 cases out of 21 cases of invasive adenoma, but only 2 cases were positive in 9 cases of non-invasive adenoma. The positive expression rate of LRIG2 mRNA was 91.3% in invasive cases (total 23 cases) and 62.5% in non-invasive cases (total 16 cases), respectively. LRIG2 gene is overexpressed in invasive pituitary adenoma. It may play an important role in pituitary adenoma invasiveness and further studies are necessary to elucidate the mechanism under this phenomenon.

HER2/ErbB2 receptor signaling in rat and human prolactinoma cells: strategy for targeted prolactinoma therapy

Dopamine agonist resistance or intolerance is encountered in approximately 20% of prolactinoma patients. Because human epidermal growth factor receptor 2 (HER2)/ErbB2 is overexpressed in prolactinomas and ErbB receptor ligands regulate prolactin (PRL) gene expression, we tested the role of HER2/ErbB2 in prolactinoma hormone regulation and adenoma cell proliferation to assess the rationale for targeting this receptor for prolactinoma therapy. As we showed prolactinoma HER2 overexpression, we generated constitutively active HER2-stable GH3 cell transfectants (HER2CA). PRL mRNA levels were induced approximately 250-fold and PRL secretion was enhanced 100-fold in HER2CA cells, which also exhibited increased proliferation. Lapatinib, a dual tyrosine kinase inhibitor (TKI) of both epidermal growth factor receptor (EGFR)/ErbB1 and HER2, blocked receptor signaling, and suppressed PRL expression more than gefitinib, a TKI of EGFR/ErbB1. Lapatinib also suppressed colony formation in soft agar more than gefitinib. Oral lapatinib treatment caused tumor shrinkage and serum PRL suppression both in HER2CA transfectant-inoculated Wistar-Furth rats and in estrogen-induced Fischer344 rat prolactinomas. In cultured human cells derived from resected prolactinoma tissue, lapatinib suppressed both PRL mRNA expression and secretion. These results demonstrate that prolactinoma HER2 potently induces PRL and regulates experimental prolactinoma cell proliferation. Because pituitary HER2 signaling is abrogated by TKIs, this receptor could be an effective target for prolactinoma therapy.

Possible relevance between prohormone convertase 2 expression and tumor growth in human adrenocorticotropin-producing pituitary adenoma

CONTEXT

Methods for preoperative diagnosis of prohormone convertase 2 (PC2)-positive ACTH-producing pituitary adenomas (APPAs) have not been established. Also, their characteristics are not evident.

OBJECTIVE

This study was designed to understand the meaning of plasma alphaMSH levels and the role of cell proliferation-signaling molecules in PC2-positive APPAs.

PATIENTS AND MAIN OUTCOME MEASURES

Nineteen human APPAs (four males and 15 females) were examined for the expression of PC2, phosphorylated ERK1/2, phosphorylated Akt1/2/3 (p-Akt) and receptor tyrosine kinases. alphaMSH was measured in extracted plasma from 17 APPA patients and 30 healthy volunteers.

RESULTS

Nine adenomas (47.4%) were immunopositive for PC2 and were large and invasive in nature. In all normal controls and eight PC2-negative cases, plasma alphaMSH was undetectable, whereas in four PC2-positive cases, it was detected at abnormally higher levels. Eight adenomas (42.1%) were immunopositive for both PC2 and p-Akt, and seven others (36.8%) were immunonegative for both, suggesting significant coexpression of PC2 and p-Akt in tumors. Quantitative RT-PCR revealed that PC2 expression is associated with phosphorylation of Akt but not with its gene expression. Most APPAs expressed receptor tyrosine kinases, but membrane-bound receptors could not be identified.

CONCLUSIONS

Our study suggests that PC2 expression and Akt phosphorylation are related at the molecular level, resulting in a change in cell cycle and an increase in pituitary adenoma size. An elevation of plasma alphaMSH could conjecture the activation of the phosphatidylinositol 3/Akt cascade in PC2-positive APPAs and may become a valuable clinical marker of tumor growth in Cushing's disease.

HMGA1a recognition candidate DNA sequences in humans

High mobility group protein A1a (HMGA1a) acts as an architectural transcription factor and influences a diverse array of normal biological processes. It binds AT-rich sequences, and previous reports have demonstrated HMGA1a binding to the authentic promoters of various genes. However, the precise sequences that HMGA1a binds to remain to be clarified. Therefore, in this study, we searched for the sequences with the highest affinity for human HMGA1a using an existing SELEX method, and then compared the identified sequences with known human promoter sequences. Based on our results, we propose the sequences “-(G/A)-G-(A/T)-(A/T)-A-T-T-T-” as HMGA1a-binding candidate sequences. Furthermore, these candidate sequences bound native human HMGA1a from SK-N-SH cells. When candidate sequences were analyzed by performing FASTAs against all known human promoter sequences, 500–900 sequences were hit by each one. Some of the extracted genes have already been proven or suggested as HMGA1a-binding promoters. The candidate sequences presented here represent important information for research into the various roles of HMGA1a, including cell differentiation, death, growth, proliferation, and the pathogenesis of cancer.

Alkyl isothiocyanates suppress epidermal growth factor receptor kinase activity but augment tyrosine kinase activity

AIM

We have reported the in vitro and in vivo anticancer activities of 6-(methylsulfinyl)hexyl isothiocyanate (6-MITC) derived from a Japanese spice, wasabi. In order to obtain some clues about the mechanism of the anticancer activity, we have studied the effect of alkyl isothiocyanates (MITCs) on protein kinase activities.

METHODS

The anti-autophosphorylation activity of MITCs with respect to the epidermal growth factor (EGF)-stimulated receptor kinase of A431 epidermoid carcinoma cells was examined by incorporation of radioactive ATP into an acid-insoluble fraction. Their anti-phosphorylation activity with respect to the non-receptor protein kinase was analyzed by a standard SDS-PAGE method.

RESULTS

All the tested MITCs interfered with the EGF-stimulated receptor kinase activity in a dose-dependent manner, although their effects were less than 1/10 of that of erbstatin in microg/ml. On the other hand, the MITCs did not interfere with non-receptor kinases (kinase A, kinase C, tyrosine kinase and calmodulin dependent kinase III), but enhanced non-receptor tyrosine kinase.

DISCUSSION

A possible anticancer mechanism of MITCs may involve the suppression of EGF receptor kinase activity and augmentation of non-receptor PTK.

Heregulin regulates prolactinoma gene expression

To investigate the role of p185(her2/neu)/ErbB3 signaling in pituitary tumor function, we examined these receptors in human prolactinomas. Immunofluorescent p185(her2/neu) was detected in almost all (seven of eight), and ErbB3 expression in a subset (four of eight) of tumors (seven adenomas and one carcinoma). Quantitative PCR also showed abundant ErbB3 mRNA in tumor specimens derived from a rarely encountered prolactin-cell carcinoma. Activation of p185(c-neu)/ErbB3 signaling with heregulin, the ErbB3 ligand, in rat lacto-somatotroph (GH4C1) tumor cells specifically induced prolactin (PRL) mRNA expression approximately 5-fold and PRL secretion approximately 4-fold, whereas growth hormone expression was unchanged. Heregulin (6 nmol/L) induced tyrosine phosphorylation and ErbB3 and p185(c-neu) heterodimerization, with subsequent activation of intracellular ERK and Akt. The Akt signal was specific to ErbB3 activation by heregulin, and was not observed in response to epidermal growth factor activation of epidermal growth factor receptor. Gefitinib, the tyrosine kinase inhibitor, suppressed heregulin-mediated p185(c-neu)/ErbB3 signaling to PRL. Heregulin induction of PRL was also abrogated by transfecting cells with short interfering RNA directed against ErbB3. Pharmacologic inhibition of heregulin-induced phosphoinositide-3-kinase/Akt (with LY294002) and ERK (with U0126) signaling, as well as short interfering RNA-mediated mitogen-activated protein kinase-1 down-regulation, showed ERK signaling as the primary transducer of heregulin signaling to PRL. These results show ErbB3 expression in human prolactinomas and a novel ErbB3-mediated mechanism for PRL regulation in experimental lactotroph tumors. Targeted inhibition of up-regulated p185(c-neu)/ErbB3 activity could be useful for the treatment of aggressive prolactinomas resistant to conventional therapy.

Down-regulation of leucine-rich repeats and immunoglobulin-like domain proteins (LRIG1-3) in HP75 pituitary adenoma cell line

Three human leucine-rich repeats and immunoglobulin-like domains (LRIG) genes and proteins, named LRIG1-3, has been previously characterized and it was proposed that they may act as suppressors of tumor growth. The LRIG1 protein can inhibit the growth of tumors of glial cells and the down-regulation of the LRIG1 gene may be involved in the development and progression of the tumor. Real-time reverse transcription-polymerase chain reaction (RT-PCR) is a recently developed technique for quantitative assessment of specific RNA levels. In the current study, it was demonstrated that LRIG1-3 and EGFR mRNA was detected in human pituitary adenoma cell lines and a normal pituitary sample, with differences in the expression levels. Compared to the normal pituitary samples, the expression of LRIG1-3 in HP75 cell line was lower, but the expression of EGFR in HP75 cell line was higher. The results are consistent with LRIG1-3 being tumour suppressor genes, and LRIG genes decreasing the expression of EGFR. The ratio of EGFR/LRIG1 was increased at least 13-fold in HP75 cells compared with the normal pituitary cells, which was also the case for the ratio of EGFR/LRIG2 (14-fold increase in HP75) and EGFR/LRIG3 (11-fold increase in HP75). Further studies were needed to elucidate the explicit role of LRIG genes as negative regulators of oncogenesis in human pituitary adenoma.

Rat prolactinoma cell growth regulation by epidermal growth factor receptor ligands

Epidermal growth factor (EGF) regulates pituitary development, hormone synthesis, and cell proliferation. Although ErbB receptor family members are expressed in pituitary tumors, the effects of EGF signaling on pituitary tumors are not known. Immunoprecipitation and Western blot confirmed EGF receptor (EGFR) and p185(c-neu) protein expression in GH3 lacto-somatotroph but not in adrenocorticotropic hormone-secreting AtT20 pituitary tumor cells. EGF (5 nmol/L) selectively enhanced baseline ( approximately 4-fold) and serum-induced (>6-fold) prolactin (PRL) mRNA levels, whereas gefitinib, an EGFR antagonist, suppressed serum-induced cell proliferation and Pttg1 expression, blocked PRL gene expression, and reversed EGF-mediated somatotroph-lactotroph phenotype switching. Downstream EGFR signaling by ERK, but not phosphoinositide-3-kinase or protein kinase C, mediated the gefitinib response. Tumors in athymic mice implanted s.c. with GH3 cells resulted in weight gain accompanied by increased serum PRL, growth hormone, and insulin growth factor 1. Gefitinib decreased tumor volumes and peripheral hormone levels by approximately 30% and restored normal mouse body weight patterns. Mice treated with gefitinib exhibited decreased tumor tissue ERK1/2 phosphorylation and down-regulated tumor PRL and Pttg1 mRNA abundance. These results show that EGFR inhibition controls tumor growth and PRL secretion in experimental lacto-somatotroph tumors. EGFR inhibitors could therefore be useful for the control of PRL secretion and tumor load in prolactinomas resistant to dopaminergic treatment, or for those prolactinomas undergoing rare malignant transformation.

Folate receptor expression in pituitary adenomas cellular and molecular analysis

Clinically nonfunctional pituitary adenomas cause hypopituitarism or compression of regional structures. Unlike functional tumors, there is no available medical treatment or specific imaging technique for these tumors. We have recently discovered that both folate receptor (FR)alpha mRNA and protein are uniquely overexpressed in nonfunctional pituitary tumors, but not in functional adenomas. We hypothesized that FRalpha may hold significant promise for medical treatment by enabling novel molecular imaging and targeted therapy. Here, we used murine pituitary tumor cell line alphaT3-1 as a model to investigate the biological significance of FRalpha and its mutant FR67. We demonstrate that overexpression of FR facilitated tumor cell growth and anchorage-independent growth in soft agar. More colonies were observed in FR overexpressing cells than in mutant FR67 clones in soft agar. Cell proliferation rate was increased, the percentage of cells in S-phase was increased, and high PCNA staining was detected in cells overexpressing the receptor. In alphaT3-1 cells transfected with mutant FR67, cell proliferation rate was reduced, the percentage of cells residing in S-phase was slightly decreased, and low PCNA staining was observed. By real-time quantitative PCR, the genes involved in NOTCH3 pathway including NOTCH3, HES-1, and TLE2 were altered; the mRNA expression of FGFR1 was upregulated, and ERbeta mRNA was downregulated in FR overexpressing cells. Our findings suggest that FRalpha plays a role in pituitary tumor formation, and this effect may in part be due to its regulation of the NOTCH3 pathway.

The antibody sc-33040-R fails to specifically recognize phosphorylation of ErbB4 on tyrosine1056

Phosphorylation state specific antibodies are important reagents for characterizing protein phosphorylation and signaling. However, these antibodies require proper validation to determine that they do not cross-react with the unphosphorylated peptide or with other phosphoproteins. We have previously shown that phosphorylation of tyrosine1056 of ErbB4 is critical for it to inhibit colony formation on plastic by human tumor cell lines. Thus, an antibody directed against this site would be useful for studying ErbB4 signaling and coupling to biological responses. Here, we demonstrate that a commercially available antibody raised against a phosphopeptide corresponding to the carboxyl-terminal domain of the ErbB4 receptor tyrosine kinase fails to exhibit appropriate specificity. Thus, this antibody does not appear to be suitable for studying ErbB4 phosphorylation or signaling.

Expression of p53, Ki-67 and c-erb B2 in growth hormone-and/or prolactin-secreting pituitary adenomas

The subcellular events implicated on the formation and behavior of pituitary adenomas are not fully understood. In this study we investigated the presence of p53, Ki-67 and c-erb B2 in 38 pituitary adenomas with immunohistochemical positivity for GH and prolactin (n=26; 68.4%), for prolactin (n=9; 23.7%) and for GH (n=3. 7.8%). The analyses revealed the following results: 24 (63.2%) tumors expressed variable positivity for c-erb B2, 11 (28.9%) expressed p53 positivity and 11 (28.9%) tumors were variably positive for Ki-67. Our results demonstrated a high percentage of GH/prolactin-, prolactin- and GH-secreting tumors with immunohistochemical positivity for c-erb B2. Once this membrane receptor is related to growth factors EGF and TGFalpha and both have a definite effect on tumor growth, our data suggest a possible role for c-erb B2 on the evolution of these tumors.

Epidermal growth factor receptor and activated epidermal growth factor receptor expression in gastrointestinal carcinoids and pancreatic endocrine carcinomas

The epidermal growth factor receptor (EGFR) plays an important role in the pathogenesis of many tumors. To analyze the expression of EGFR and activated EGFR in well-differentiated neuroendocrine carcinomas including primary and metastatic gastrointestinal carcinoid tumors and pancreatic endocrine tumors (PET), we examined 58 gastrointestinal carcinoid tumors and 48 PET using immunohistochemistry, Western blotting, and RT-PCR. EGFR and activated EGFR (P-EGFR) were expressed by both gastrointestinal carcinoids and PET in primary and metastatic tumors, although a higher percentage of gastrointestinal carcinoid tumors expressed EGFR and activated EGFR. Western blotting detected a 170 kDa band for both EGFR and activated EGFR in three primary carcinoid tumors and two metastatic carcinoid tumors to the liver. RT-PCR analysis confirmed the expression of EGFR mRNA in both primary and metastatic carcinoid tumors. Patients with activated EGFR expression in their primary PET had a significantly worse prognosis compared to those who did not express activated-EGFR (P = 0.043). These results indicate that gastrointestinal carcinoid tumors as well as PET express EGFR and activated EGFR, and that expression is more common in gastrointestinal carcinoid tumors compared to pancreatic endocrine tumors. These findings implicate the EGFR and P-EGFR signal transduction pathway in the pathogenesis of these neuroendocrine tumors and suggest that targeted therapy directed against the EGFR tyrosine kinase domain may be a useful therapeutic approach in patients with unresectable metastatic gastrointestinal carcinoid tumors and pancreatic endocrine tumors.

Pituitary carcinoma: diagnosis and treatment

Pituitary carcinomas are rare pituitary tumors that by definition have cerebrospinal and/or systemic metastases. Most of the tumors occur in the setting of multiple recurrences of invasive pituitary adenomas. This article reviews the clinical presentation of these tumors, their neuroimaging and pathological features, tumor pathogenesis, and possible treatment modalities.

Metastatic prolactinoma: case report with immunohistochemical assessment for p53 and Ki-67 antigens

Pituitary carcinomas are rare neoplasms characterized by craniospinal and/or systemic metastases originated from the pituitary. Their histopathology is frequently indistinguishable from that of benign adenomas. The development of markers that better reflect their behavior is desirable. We present the case of a 47 year-old man with a prolactin-secreting macroadenoma who was submitted to surgeries, cranial radiation therapy, and bromocriptine treatment, but evolved to a fatal outcome after the disclosure of intracranial metastases. Tumor samples underwent p53 and Ki-67 immunohistochemical assessment. p53 was absent in all samples, a rare finding among pituitary carcinomas. Ki-67 proliferative index was 2.80% in the original tumor, 4.40% in the relapse, and 4.45% in the metastasis. The figure in the relapse is higher than the expected for a noninvasive adenoma. In conclusion, p53 staining is not positive in all pituitary carcinomas. A high Ki-67 proliferative index in a pituitary adenoma might indicate a more aggressive behavior.

Pituitary cell lines and their endocrine applications

The pituitary gland is an important component of the endocrine system, and together with the hypothalamus, exerts considerable influence over the functions of other endocrine glands. The hypothalamus either positively or negatively regulates hormonal productions in the pituitary through its release of various trophic hormones which act on specific cell types in the pituitary to secrete a variety of pituitary hormones that are important for growth and development, metabolism, reproductive and nervous system functions. The pituitary is divided into three sections-the anterior lobe which constitute the majority of the pituitary mass and is composed primarily of five hormone-producing cell types (thyrotropes, lactotropes, corticotropes, somatotropes and gonadotropes) each secreting thyrotropin, prolactin, ACTH, growth hormone and gonadotropins (FSH and LH) respectively. There is also a sixth cell type in the anterior lobe-the non-endocrine, agranular, folliculostellate cells. The intermediate lobe produces melanocyte-stimulating hormone and endorphins, whereas the posterior lobe secretes anti-diuretic hormone (vasopressin) and oxytocin. Representative cell lines of all the six cell types of the anterior pituitary have been established and have provided valuable information on genealogy of the various cell lineages, endocrine feedback control of hormone synthesis and secretions, intrapituitary interactions between the various cell types, as well as the role of specific transcription factors that determine each differentiated cell phenotype. In this review, we will discuss the morphology and function of the cell types that make up the anterior pituitary, and the characteristics of the various functional anterior pituitary cell systems that have been established to be representative of each anterior pituitary cell lineage.