p53 gene mutations in pituitary adenomas: rare events

An Overview of Pituitary Neuroendocrine Tumors (PitNET) and Algorithmic Approach to Diagnosis

The diagnostic algorithm and nomenclature of pituitary neuroendocrine tumors have evolved over the past decade, beginning with simpler categorical schemes focused on histomorphologic features and moving to a more sophisticated lineage-specific categorization. This contemporary overview highlights a multimodal approach to pituitary neuroendocrine tumors with a focus on changes in nomenclature, classification, and subclassification; including, brief comments on treatment, and new guidelines for genetic screening, particularly for young patients with such neoplasms.

TP53 mutations in functional corticotroph tumors are linked to invasion and worse clinical outcome

Corticotroph macroadenomas are rare but difficult to manage intracranial neoplasms. Mutations in the two Cushing's disease mutational hotspots USP8 and USP48 are less frequent in corticotroph macroadenomas and invasive tumors. There is evidence that TP53 mutations are not as rare as previously thought in these tumors. The aim of this study was to determine the prevalence of TP53 mutations in corticotroph tumors, with emphasis on macroadenomas, and their possible association with clinical and tumor characteristics. To this end, the entire TP53 coding region was sequenced in 86 functional corticotroph tumors (61 USP8 wild type; 66 macroadenomas) and the clinical characteristics of patients with TP53 mutant tumors were compared with TP53/USP8 wild type and USP8 mutant tumors. We found pathogenic TP53 variants in 9 corticotroph tumors (all macroadenomas and USP8 wild type). TP53 mutant tumors represented 14% of all functional corticotroph macroadenomas and 24% of all invasive tumors, were significantly larger and invasive, and had higher Ki67 indices and Knosp grades compared to wild type tumors. Patients with TP53 mutant tumors had undergone more therapeutic interventions, including radiation and bilateral adrenalectomy. In conclusion, pathogenic TP53 variants are more frequent than expected, representing a relevant amount of functional corticotroph macroadenomas and invasive tumors. TP53 mutations associated with more aggressive tumor features and difficult to manage disease.

Genetics of Cushing's disease

Corticotroph tumours are primarily sporadic monoclonal neoplasms and only rarely found in genetic syndromes. Recurrent mutations in the ubiquitin specific protease 8 (USP8) gene are found in around half of cases. Mutations in other genes such as USP48 and NR3C1 are less frequent, found in less than ~20% of cases. TP53 and ATXR mutations are reported in up to one out of four cases, when focusing in USP8 wild type or aggressive corticotroph tumours and carcinomas. At present, USP8 mutations are the primary driver alterations in sporadic corticotroph tumours, TP53 and ATXR mutations may indicate transition to more aggressive tumour phenotype. Next generation sequencing efforts have identified additional genomic alterations, whose role and importance in corticotroph tumorigenesis remains to be elucidated.

Challenges in the Diagnosis of Pituitary Neuroendocrine Tumors

Detailed analysis of cytodifferentiation and hormone production has classified pituitary neuroendocrine tumors (PitNETs) in a formal system that reflects the lineage differentiation of nontumorous adenohypophysial cells as well as subtypes of tumors that have predictive value. In addition, tumors composed of cells that lack terminal differentiation are well characterized. To comply with the proposal to create an overarching classification of neuroendocrine neoplasia, these tumors are now called PitNETs rather than adenomas. The next important step will be to relinquish the term "pituitary carcinoma" for metastatic PitNETs that remain well differentiated, and to alter the terminology used for tumors that are not terminally differentiated to reflect only their immature lineage. The existence of mixed neuroendocrine and non-neuroendocrine neoplasms (MiNENs) similar to those at other body sites is proven by mixed craniopharyngiomas with PitNETs. As with other NETs, these neoplasms should be reported with synoptic data that guide completeness of reporting. A formal system of grading should be created, but not only based on proliferation, as these tumors have shown the prognostic value of cytodifferentiation. A formal system of staging should also be devised to complement grade in the thorough and accurate diagnosis of tumors that arise from adenohypophysial cells.

Genomics and Epigenomics of Pituitary Tumors: What Do Pathologists Need to Know?

Molecular pathology has advanced our understanding of many tumors and offers opportunities to identify novel therapies. In the pituitary, the field has uncovered several genetic mutations that predispose to pituitary neuroendocrine tumor (PitNET) development, including MEN1, CDKN1B, PRKRIα, AIP, GPR101, and other more rare events; however, these genes are only rarely mutated in sporadic PitNETs. Recurrent genetic events in sporadic PitNETs include GNAS mutations in a subset of somatotroph tumors and ubiquitin-specific peptidase mutations (e.g., USP8, USP48) in some corticotroph tumors; to date, neither of these has resulted in altered management, and instead, the prognosis and management of PitNETs still rely more on cell type and subtype as well as local growth that determines surgical resectability. In contrast, craniopharyngiomas have either CTNNB1 or BRAF^V600E mutations that correlate with adamantinomatous or papillary morphology, respectively; the latter offers the opportunity for targeted therapy. DICER1 mutations are found in patients with pituitary blastoma. Epigenetic changes are implicated in the pathogenesis of the more common sporadic pituitary neoplasms including the majority of PitNETs and tumors of pituicytes.

Genetic analysis of the cooperative tumorigenic effects of targeted deletions of tumor suppressors Rb1, Trp53, Men1, and Pten in neuroendocrine tumors in mice

Genetic alterations of tumor suppressor genes (TSGs) are frequently observed to have cumulative or cooperative tumorigenic effects. We examined whether the TSGs Rb1, Trp53, Pten and Men1 have cooperative effects in suppressing neuroendocrine tumors (NETs) in mice. We generated pairwise homozygous deletions of these four genes in insulin II gene expressing cells using the Cre-LoxP system. By monitoring growth and examining the histopathology of the pituitary (Pit) and pancreas (Pan) in these mice, we demonstrated that pRB had the strongest cooperative function with PTEN in suppressing PitNETs and had strong cooperative function with Menin and TRP53, respectively, in suppressing PitNETs and PanNETs. TRP53 had weak cooperative function with PTEN in suppressing pituitary lesions. We also found that deletion of Pten singly led to prolactinomas in female mice, and deletion of Rb1 alone led to islet hyperplasia in pancreas. Collectively, our data indicated that pRB and PTEN pathways play significant roles in suppressing PitNETs, while the Menin-mediated pathway plays a significant role in suppressing PanNETs. Understanding the molecular mechanisms of these genes and pathways on NETs will help us understand the molecular mechanisms of neuroendocrine tumorigenesis and develop effective preclinical murine models for NET therapeutics to improve clinical outcomes in humans.

Cushing syndrome: Old and new genes

Cushing syndrome (CS) describes the signs and symptoms caused by exogenous or endogenous hypercortisolemia. Endogenous CS is caused by either ACTH-dependent sources (pituitary or ectopic) or ACTH-independent (adrenal) hypercortisolemia. Several genes are currently known to contribute to the pathogenesis of CS. Germline gene defects, such as MEN1, AIP, PRKAR1A and others, often present in patients with pituitary or adrenal involvement as part of a genetic syndrome. Somatic defects in genes, such as USP8, TP53, and others, are also involved in the development of pituitary or adrenal tumors in a large percentage of patients with CS, and give insight in pathways involved in pituitary or adrenal tumorigenesis.

The Genetics of Pituitary Adenomas

The genetic landscape of pituitary adenomas (PAs) is diverse and many of the identified cases remain of unclear pathogenetic mechanism. Germline genetic defects account for a small percentage of all patients and may present in the context of relevant family history. Defects in AIP (mutated in Familial Isolated Pituitary Adenoma syndrome or FIPA), MEN1 (coding for menin, mutated in Multiple Endocrine Neoplasia type 1 or MEN 1), PRKAR1A (mutated in Carney complex), GPR101 (involved in X-Linked Acrogigantism or X-LAG), and SDHx (mutated in the so called "3 P association" of PAs with pheochromocytomas and paragangliomas or 3PAs) account for the most common familial syndromes associated with PAs. Tumor genetic defects in USP8, GNAS, USP48 and BRAF are some of the commonly encountered tissue-specific changes and may explain a larger percentage of the developed tumors. Somatic (at the tumor level) genomic changes, copy number variations (CNVs), epigenetic modifications, and differential expression of miRNAs, add to the variable genetic background of PAs.

Conserved Pseudoknots in lncRNA MEG3 Are Essential for Stimulation of the p53 Pathway

Long non-coding RNAs (lncRNAs) are key regulatory molecules, but unlike with other RNAs, the direct link between their tertiary structure motifs and their function has proven elusive. Here we report structural and functional studies of human maternally expressed gene 3 (MEG3), a tumor suppressor lncRNA that modulates the p53 response. We found that, in an evolutionary conserved region of MEG3, two distal motifs interact by base complementarity to form alternative, mutually exclusive pseudoknot structures ("kissing loops"). Mutations that disrupt these interactions impair MEG3-dependent p53 stimulation in vivo and disrupt MEG3 folding in vitro. These findings provide mechanistic insights into regulation of the p53 pathway by MEG3 and reveal how conserved motifs of tertiary structure can regulate lncRNA biological function.

Next-generation sequencing identifies novel mitochondrial variants in pituitary adenomas

PURPOSE

Disrupted mitochondrial functions and genetic variants of mitochondrial DNA (mtDNA) have been observed in different human neoplasms. Next-generation sequencing (NGS) can be used to detect even low heteroplasmy-level mtDNA variants. We aimed to investigate the mitochondrial genome in pituitary adenomas by NGS.

METHODS

We analysed 11 growth hormone producing and 33 non-functioning [22 gonadotroph and 11 hormone immunonegative] pituitary adenomas using VariantPro™ Mitochondrion Panel on Illumina MiSeq instrument. Revised Cambridge Reference Sequence (rCRS) of the mtDNA was used as reference. Heteroplasmy was determined using a 3% cutoff.

RESULTS

496 variants were identified in pituitary adenomas with overall low level of heteroplasmy (7.22%). On average, 35 variants were detected per sample. Samples harbouring the highest number of variants had the highest Ki-67 indices independently of histological subtypes. We identified eight variants (A11251G, T4216C, T16126C, C15452A, T14798C, A188G, G185A, and T16093C) with different prevalences among different histological groups. T16189C was found in 40% of non-recurrent adenomas, while it was not present in the recurrent ones. T14798C and T4216C were confirmed by Sanger sequencing in all 44 samples. 100% concordance was found between NGS and Sanger method.

CONCLUSIONS

NGS is a reliable method for investigating mitochondrial genome and heteroplasmy in pituitary adenomas. Out of the 496 detected variants, 414 have not been previously reported in pituitary adenoma. The high number of mtDNA variants may contribute to adenoma genesis, and some variants (i.e., T16189C) might associate with benign behaviour.

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.

Overview of the 2017 WHO Classification of Pituitary Tumors

This review focuses on discussing the main changes on the upcoming fourth edition of the WHO Classification of Tumors of the Pituitary Gland emphasizing histopathological and molecular genetics aspects of pituitary neuroendocrine (i.e., pituitary adenomas) and some of the non-neuroendocrine tumors involving the pituitary gland. Instead of a formal review, we introduced the highlights of the new WHO classification by answering select questions relevant to practising pathologists. The revised classification of pituitary adenomas, in addition to hormone immunohistochemistry, recognizes the role of other immunohistochemical markers including but not limited to pituitary transcription factors. Recognizing this novel approach, the fourth edition of the WHO classification has abandoned the concept of "a hormone-producing pituitary adenoma" and adopted a pituitary adenohypophyseal cell lineage designation of the adenomas with subsequent categorization of histological variants according to hormone content and specific histological and immunohistochemical features. This new classification does not require a routine ultrastructural examination of these tumors. The new definition of the Null cell adenoma requires the demonstration of immunonegativity for pituitary transcription factors and adenohypophyseal hormones Moreover, the term of atypical pituitary adenoma is no longer recommended. In addition to the accurate tumor subtyping, assessment of the tumor proliferative potential by mitotic count and Ki-67 index, and other clinical parameters such as tumor invasion, is strongly recommended in individual cases for consideration of clinically aggressive adenomas. This classification also recognizes some subtypes of pituitary neuroendocrine tumors as "high-risk pituitary adenomas" due to the clinical aggressive behavior; these include the sparsely granulated somatotroph adenoma, the lactotroph adenoma in men, the Crooke's cell adenoma, the silent corticotroph adenoma, and the newly introduced plurihormonal Pit-1-positive adenoma (previously known as silent subtype III pituitary adenoma). An additional novel aspect of the new WHO classification was also the definition of the spectrum of thyroid transcription factor-1 expressing pituitary tumors of the posterior lobe as representing a morphological spectrum of a single nosological entity. These tumors include the pituicytoma, the spindle cell oncocytoma, the granular cell tumor of the neurohypophysis, and the sellar ependymoma.

Role of a p53 polymorphism in the development of nonfunctional pituitary adenomas

Non-functional pituitary adenomas (NFPAs) are among the commonest intracranial neoplasms. While histologically benign, NFPAs sometimes become large enough to limit therapeutic options and reduce quality of life. Investigations of the molecular etiology of NFPAs have failed to identify prevalent genetic changes and, while a role for p53 has been suggested, TP53 gene alterations have yet to be described in NFPAs. We found that the polymorphism rs1042522:C > G in codon 72 of exon 4 of the TP53 gene, whose C variant produces a proline and is more common in most ethnicities, has a G variant producing an arginine in 79.8% of NFPAs (n = 42; p < 1.411 × 10^-18 vs. 1000 Genomes database), causing patients to present a decade earlier with symptomatic NFPAs. In cultured NFPA cells, transfection with the rs1042522 G variant versus the C variant reduced expression of cell arrest gene p21 and increased proliferation. These findings suggest that this TP53 polymorphism influences NFPA growth.

The Role of p16 and MDM2 Gene Polymorphisms in Prolactinoma: MDM2 Gene Polymorphisms May Be Associated with Tumor Shrinkage

AIM

Prolactinomas are thought to arise from clonal expansion of a single mutated cell which is subjected to growth stimuli of several permissive factors, although the pathogenetic mechanisms underlying tumorigenesis remain unclear. The present study aimed to investigate the role of p16 (540C→G and 580C→T) and mouse double minute 2 (MDM2) (SNP309T→G) gene polymorphisms in tumorigenesis and characteristics of prolactinoma.

PATIENTS AND METHODS

A total of 74 patients with prolactinoma and 100 age- and gender-matched healthy individuals were enrolled in the study. Serum prolactin levels were measured by enzyme-linked immunosorbent assay (ELISA). p16 and MDM2 polymorphisms were determined by polymerase chain reaction-restriction fragment polymorphism and agarose gel electrophoresis.

RESULTS

p16 540C→G genotype distribution was found to be: CC: 66.2%, CG: 28.4%, GG: 5.4%; p16 580C→T genotype distribution was found to be: CC: 82.4%, CT: 17.6%, TT: 0% and MDM2 genotype distribution was found to be: TT: 31.1%, TG: 47.3%, GG: 21.6% in patients with prolactinoma. Tumor diameter before treatment was correlated with prolactin levels before treatment and percentage of prolactin decrease with treatment (r=0.719, p<0.001, p=0.034 r=0.256, respectively). The number of patients with tumor size decrease of more than 50% in those with homozygous genotype (TT+GG) of MDM2 SNP309T→G was significantly higher than in heterozygous genotype (TG) carriers (odds ratio(OR)=0.18, 95% confidence interval(CI)=0.06-0.58; p=0.003).

CONCLUSION

This study showed that p16 and MDM2 polymorphisms do not play a decisive role in tumorigenesis, but some genotypes of these polymorphisms might be associated with follow-up characteristics of prolactinoma.

Gene mutations in Cushing's disease

Cushing's disease (CD) is a severe (and potentially fatal) disease caused by adrenocorticotropic hormone (ACTH)-secreting adenomas of the pituitary gland (often termed pituitary adenomas). The majority of ACTH-secreting corticotroph tumors are sporadic and CD rarely appears as a familial disorder, thus, the genetic mechanisms underlying CD are poorly understood. Studies have reported that various mutated genes are associated with CD, such as those in menin 1, aryl hydrocarbon receptor-interacting protein and the nuclear receptor subfamily 3 group C member 1. Recently it was identified that ubiquitin-specific protease 8 mutations contribute to CD, which was significant towards elucidating the genetic mechanisms of CD. The present study reviews the associated gene mutations in CD patients.

Aggressive Pituitary Tumors or Localized Pituitary Carcinomas: Defining Pituitary Tumors

Pituitary tumors are common and exhibit a wide spectrum of hormonal, proliferative and invasive behaviors. Traditional classifications consider them malignant only when they exhibit metastasis. Patients who suffer morbidity and mortality from aggressive tumors classified as "adenomas" are denied support provided to patients with "cancers" and in many jurisdictions, these tumors are considered curiosities that do not warrant reporting in health registries. We propose use of the term "tumor" rather than "adenoma" to align with other neuroendocrine tumors. The features that can serve as diagnostic, prognostic and predictive markers are reviewed. Clinico-pathological and radiographic classifications provide important information and to date, no single biomarker has been able to offer valuable insight to guide the management of patients with pituitary tumors.

MEN1, MEN4, and Carney Complex: Pathology and Molecular Genetics

Pituitary adenomas are a common feature of a subset of endocrine neoplasia syndromes, which have otherwise highly variable disease manifestations. We provide here a review of the clinical features and human molecular genetics of multiple endocrine neoplasia (MEN) type 1 and 4 (MEN1 and MEN4, respectively) and Carney complex (CNC). MEN1, MEN4, and CNC are hereditary autosomal dominant syndromes that can present with pituitary adenomas. MEN1 is caused by inactivating mutations in the MEN1 gene, whose product menin is involved in multiple intracellular pathways contributing to transcriptional control and cell proliferation. MEN1 clinical features include primary hyperparathyroidism, pancreatic neuroendocrine tumours and prolactinomas as well as other pituitary adenomas. A subset of patients with pituitary adenomas and other MEN1 features have mutations in the CDKN1B gene; their disease has been called MEN4. Inactivating mutations in the type 1α regulatory subunit of protein kinase A (PKA; the PRKAR1A gene), that lead to dysregulation and activation of the PKA pathway, are the main genetic cause of CNC, which is clinically characterised by primary pigmented nodular adrenocortical disease, spotty skin pigmentation (lentigines), cardiac and other myxomas and acromegaly due to somatotropinomas or somatotrope hyperplasia.

Histological criteria for atypical pituitary adenomas - data from the German pituitary adenoma registry suggests modifications

INTRODUCTION

The term atypical pituitary adenoma (APA) was revised in the 2004 World Health Organization (WHO) classification of pituitary tumors. However, two of the four parameters required for the diagnosis of APAs were formulated rather vaguely (i.e., "extensive" nuclear staining for p53; "elevated" mitotic index). Based on a case-control study using a representative cohort of typical pituitary adenomas and APAs selected from the German Pituitary Tumor Registry, we aimed to obtain reliable cut-off values for both p53 and the mitotic index. In addition, we analyzed the impact of all four individual parameters (invasiveness, Ki67-index, p53, mitotic index) on the selectivity for differentiating both adenoma subtypes.

METHODS

Of the 308 patients included in the study, 98 were diagnosed as APAs (incidence 2.9 %) and 10 patients suffered from a pituitary carcinoma (incidence 0.2 %). As a control group, we selected 200 group matched patients with typical pituitary adenomas (TPAs). Cut-off values were attained using ROC analysis.

RESULTS

We determined significant threshold values for p53 (≥2 %; AUC: 0.94) and the mitotic index (≥2 mitosis within 10 high power fields; AUC: 0.89). The most reliable individual marker for differentiating TPAs and APAs was a Ki-67-labeling index ≥ 4 % (AUC: 0.98). Using logistic regression analysis (LRA) we were able to show that all four criteria (Ki-67 (p < 0.001); OR 5.2// p53 (p < 0.001); OR 3.1// mitotic index (p < 0.001); OR 2.1// invasiveness (p < 0.001); OR 8.2)) were significant for the group of APAs. Furthermore, we describe the presence of nucleoli as a new favorable parameter for TPAs (p = 0.008; OR: 0.4; CI95 %: 0.18; 0.77).

CONCLUSIONS

Here we present a proposed rectification of the current WHO classification of pituitary tumors describing an additional marker for TPA and specific threshold values for p53 and the mitotic index. This will greatly help in the reliable diagnosis of APAs and facilitate further studies to ascertain the prognostic relevance of this categorization.

Invasion of the cavernous sinus space in pituitary adenomas: endoscopic verification and its correlation with an MRI-based classification

OBJECT An important prognostic factor for the surgical outcome and recurrence of a pituitary adenoma is its invasiveness into parasellar tissue, particularly into the space of the cavernous sinus (CS). The aims of this study were to reevaluate the existing parasellar classifications using an endoscopic technique and to evaluate the clinical and radiological outcomes associated with each grade. METHODS The authors investigated 137 pituitary macroadenomas classified radiologically at least on one side as Grade 1 or higher (parasellar extension) and correlated the surgical findings using an endoscopic technique, with special reference to the invasiveness of the tumor into the CS. In each case, postoperative MRI was performed to evaluate the gross-total resection (GTR) rate and the rate of endocrinological remission (ER) in functioning adenomas. RESULTS The authors found a 16% rate of CS invasion during surgery for these macroadenomas. Adenomas radiologically classified as Grade 1 were found to be invasive in 1.5%, and the GTR/ER rate was 83%/88%. For Grade 2 adenomas, the rate of invasion was 9.9%, and the GTR/ER rate was 71%/60%. For Grade 3 adenomas, the rate of invasion was 37.9%, and the GTR/ER rate was 75%/33%. When the superior compartment of the CS (Grade 3A) was involved, the authors found a rate of invasion that was lower (p < 0.001) than that when the inferior compartment was involved (Grade 3B). The rate of invasion in Grade 3A adenomas was 26.5% with a GTR/ER rate of 85%/67%, whereas for Grade 3B adenomas, the rate of surgically observed invasion was 70.6% with a GTR/ER rate of 64%/0%. All of the Grade 4 adenomas were invasive, and the GTR/ER rate was 0%. A comparison of microscopic and endoscopic techniques revealed no difference in adenomas with Grade 1 or 4 parasellar extension. In Grade 2 adenomas, however, the CS was found by the endoscopic technique to be invaded in 9.9% and by microscopic evaluation to be invaded in 88% (p < 0.001); in Grade 3 adenomas, the difference was 37.9% versus 86%, respectively (p = 0.002). Grade 4 adenomas had a statistically significant lower rate of GTR than those of all the other grades. In case of ER only, Grade 1 adenomas had a statistically significant higher rate of remission than did Grade 3B and Grade 4 adenomas. CONCLUSIONS The proposed classification proved that with increasing grades, the likelihood of surgically observed invasion rises and the chance of GTR and ER decreases. The direct endoscopic view confirmed the low rate of invasion of Grade 1 adenomas but showed significantly lower rates of invasion in Grade 2 and 3 adenomas than those previously found using the microscopic technique. In cases in which the intracavernous internal carotid artery was encased (Grade 4), all the adenomas were invasive and the GTR/ER rate was 0%/0%. The authors suggest the addition of Grades 3A and 3B to distinguish the strikingly different outcomes of adenomas invading the superior CS compartments and those invading the inferior CS compartments.

Genetic and epigenetic mutations of tumor suppressive genes in sporadic pituitary adenoma

Human pituitary adenomas are the most common intracranial neoplasms. Approximately 5% of them are familial adenomas. Patients with familial tumors carry germline mutations in predisposition genes, including AIP, MEN1 and PRKAR1A. These mutations are extremely rare in sporadic pituitary adenomas, which therefore are caused by different mechanisms. Multiple tumor suppressive genes linked to sporadic tumors have been identified. Their inactivation is caused by epigenetic mechanisms, mainly promoter hypermethylation, and can be placed into two groups based on their functional interaction with tumor suppressors RB or p53. The RB group includes CDKN2A, CDKN2B, CDKN2C, RB1, BMP4, CDH1, CDH13, GADD45B and GADD45G; AIP and MEN1 genes also belong to this group. The p53 group includes MEG3, MGMT, PLAGL1, RASSF1, RASSF3 and SOCS1. We propose that the tumor suppression function of these genes is mainly mediated by the RB and p53 pathways. We also discuss possible tumor suppression mechanisms for individual genes.

HIF-1α inhibition sensitizes pituitary adenoma cells to temozolomide by regulating MGMT expression

Suppression of hypoxia-inducible factor 1α (HIF-1α) has been shown to sensitize glioblastoma cells to temozolomide (TMZ) treatment via down-modulation of O6-methylguanine-DNA methyltransferase (MGMT) expression. To date, whether the efficacy of TMZ therapy is correlated with MGMT expression and whether HIF-1α suppression exerts similar effects in human pituitary adenoma cells have not been defined. In the present study, using an HIF-1α knockdown strategy and the HIF-1α inhibitor 2-methoxyestradiol (2ME), we demonstrated for the first time that HIF-1α suppression increases the efficacy of TMZ in human pituitary adenoma cells in vitro and in vivo. Our mechanistic study showed that HIF-1α suppression resulted in down-modulation of MGMT expression and decreased DNA damage repair ability as demonstrated by decreased RAD51 protein expression. These results suggest an HIF-1α-dependent regulation of MGMT expression in human pituitary adenoma cells, and HIF-1α knockdown or the HIF-1α inhibitor 2ME can confer TMZ sensitization in human pituitary adenomas. The clinical application of 2ME as an adjuvant therapy may be a potential approach to improve the efficacy of TMZ therapy for pituitary adenomas.

Overexpression of RBBP6, alone or combined with mutant TP53, is predictive of poor prognosis in colon cancer

Retinoblastoma binding protein 6 (RBBP6) plays an important role in chaperone-mediated ubiquitination and interacts with TP53 in carcinogenesis. However, the clinicopathologic significance of RBBP6 expression in colon cancer is unknown; in particular, the prognostic value of RBBP6 combined with TP53 expression has not been explored. Therefore, quantitative real-time PCR and western blot analyses were performed to detect RBBP6 expression in colon cancer tissues. RBBP6 and TP53 expression were assessed by immunohistochemistry in a tissue microarray format, in which the primary colon cancer tissue was paired with noncancerous tissue. Tissue specimens were obtained from 203 patients. We found that RBBP6 was overexpressed in colon tumorous tissues and was significantly associated with clinical stage, depth of tumor invasion, lymph node metastasis (LNM), distant metastasis, and histologic grade. Further studies revealed that a corresponding correlation between RBBP6 overexpression and mutant TP53 was evident in colon cancer (r = 0.450; P<0.001). RBBP6 expression was an independent prognostic factor for overall survival (OS) and disease free survival (DFS). Interestingly, patients with tumors that had both RBBP6 overexpression and mutant TP53 protein accumulation relapsed and died within a significantly short period after surgery (P<0.001). Multivariate analysis showed that patients with LNM and patients with both RBBP6- and TP53-positive tumors had extremely poor OS (HR 6.75; 95% CI 2.63–17.35; P<0.001) and DFS (HR 8.08; 95% CI 2.80–23.30; P<0.001). These clinical findings indicate that the assessment of both RBBP6 and mutant TP53 expression will be helpful in predicting colon cancer prognosis.

Pituitary carcinomas and aggressive pituitary tumours: merits and pitfalls of temozolomide treatment

Pituitary carcinomas are rare, accounting for about 0.2% of all pituitary tumours. They represent a challenge to clinical practice in both diagnosis and treatment. They may present initially as typical pituitary adenomas, with a delayed appearance of aggressive signs, or as aggressive tumours from the outset. Predicting the pituitary tumour behaviour remains difficult: increased mitotic, Ki-67 and P53 indices might be associated with tumour aggression. The treatment of pituitary carcinomas and aggressive pituitary tumours includes surgery, adjuvant medical treatment, external beam radiotherapy and chemotherapy. Until recently, the treatment of pituitary carcinomas was mainly palliative and did not seem to increase overall survival. Recent case reports have detailed the successful use of temozolomide, an orally administered alkylating agent used to treat malignant gliomas, in the management of pituitary carcinomas and aggressive pituitary tumours. The outcome of treatment might depend on the expression of O(6)-methylguanine-DNA methyltransferase (MGMT), a DNA repair enzyme that potentially interferes with drug efficacy. This review describes the clinical presentation and response to temozolomide in 44 patients with pituitary carcinomas or aggressive pituitary tumours reported in the literature. The results suggest that temozolomide should be considered a drug of major importance in the therapeutic algorithm of aggressive pituitary tumours and pituitary carcinomas. Because of the inconsistency of published data, MGMT expression should probably not be taken as a reason to deny these patients the potential benefit of temozolomide treatment, taking into account the paucity of other available treatments.

Possible role of a radiation-induced p53 mutation in a Nelson's syndrome patient with a fatal outcome

Nelson's syndrome (NS) is characterized by the appearance and/or progression of ACTH-secreting pituitary macroadenomas in patients who had previously undergone bilateral adrenalectomy for the treatment of Cushing's disease. Such corticotroph macroadenomas respond poorly to currently available therapeutic options which include surgery, radiotherapy and chemotherapy. P53 protein accumulation may be detected by immunohistochemistry in pituitary corticotroph adenomas and it has been suggested that it might be causally related to tumor development. Wild type P53 protein plays an important role in the cellular response to ionizing radiation and other DNA damaging agents and is mutated in many human tumors. In this study we report an adult male patient with NS who underwent both transsphenoidal and transcranial pituitary surgeries, conventional and stereotaxic radiotherapy and brachytherapy. Despite of the efforts to control tumor mass and growth, this macroadenoma displayed relentless growth and aggressive behavior. DNA extracted from the first two surgical samples, as well as DNA from peripheral blood leukocytes disclosed normal p53 sequence. DNA extracted from tumor samples obtained at surgeries performed after pituitary irradiation carried a somatic heterozygous mutation, consisting of a deletion of four cytosines between nucleotides 12,144-12,149 in exon 4 of the p53 gene. This frameshift mutation creates a stop codon in exon 4 excluding the expression of a functional protein from the defective allele. These data demonstrate a possible association between the P53 protein loss of function induced by radiotherapy and the aggressive course of the disease in this patient.

Identification of growth arrest and DNA-damage-inducible gene beta (GADD45beta) as a novel tumor suppressor in pituitary gonadotrope tumors

Gonadotrope and null cell pituitary tumors cause significant morbidity, often presenting with signs of hypogonadism together with visual disturbances due to mass effects. Surgery and radiation are the only therapeutic options to date. To identify dysregulated genes and pathways that may play a role in tumorigenesis and/or progression, molecular profiling was performed on 14 gonadotrope tumors, with nine normal human pituitaries obtained at autopsy serving as controls. Bioinformatic analysis identified putative downstream effectors of tumor protein 53 (p53) that were consistently repressed in gonadotrope pituitary tumors, including RPRM, P21, and PMAIP1, with concomitant inhibition of the upstream p53 regulator, PLAGL1(Zac1). Further analysis of the growth arrest and DNA damage-inducible (GADD45) family revealed no change in the p53 target, GADD45α, but identified repression of GADD45β in pituitary tumors in addition to the previously reported inhibition of GADD45γ. Overexpression of GADD45β in LβT2 mouse gonadotrope cells blocked tumor cell proliferation and increased rates of apoptosis in response to growth factor withdrawal. Stable gonadotrope cell transfectants expressing increased GADD45β showed decreased colony formation in soft agar, confirming its normal role as a tumor suppressor. Unlike previous studies of GADD45γ in pituitary tumors and α and β in other tumors, bisulfite sequencing showed no evidence of hypermethylation of the GADD45β promoter in human pituitary tumor samples to explain the repression of its expression. Thus, GADD45β is a novel pituitary tumor suppressor whose reexpression blocks proliferation, survival, and tumorigenesis. Together these studies identify new targets and mechanisms to explore in pituitary tumor initiation and progression.

Aggressive prolactinoma in a child related to germline mutation in the ARYL hydrocarbon receptor interacting protein (AIP) gene

The objective of this study was to describe a familial screening for AIP mutations in the context of aggressive prolactinoma in childhood. A 12-year-old boy, presented headaches and bilateral hemianopsia. He had adequate height and weight for his age (50th percentile), Tanner stage G1 P1. His bone age was 10 years. Prolactin was 10.560 ng/mL (3-25), FSH and LH were undetectable, IGF-1, TSH, Free T4, ACTH, and cortisol were within normal ranges. MRI showed a pituitary macroadenoma, 5.3 X 4.0 X 3.5 cm with compression of the optic chiasm, bilateral cavernous sinus invasion, encasement of carotids, and extension to clivus. Surgical debulking was performed. Resistance to cabergoline was characterized and he was submitted to two surgeries and radiotherapy. Immunohistochemical evaluation included prolactin, ACTH, GH, FSH, LH,AIP, c-erb B2, Ki-67, and p53. Genomic DNA was isolated from the index case and 48 relatives, PCR and sequencing were performed.A germline A195V mutation in AIP was identified in the index case and in five asymptomatic relatives. Germline mutations in the AIP gene may be involved in the predisposition to pituitary adenoma formation, as cause or co-factor in pathogenesis of aggressive tumors in young patients.

Isolation and characterization of novel pituitary tumor related genes: a cDNA representational difference approach

Recently, progress has been made in understanding human pituitary tumor pathogenesis by the investigation of differences in gene expression between normal pituitary tissue and pituitary tumors. A number of approaches, including differential display (DD), representational difference analysis (RDA), and microarray analysis have been used and several molecular targets potentially associated with pituitary tumor development and invasion have been identified. We have used RDA to compare gene expression patterns between normal human pituitary and clinically non-functioning pituitary adenomas, and identified genes with growth suppression function which are expressed in the normal pituitary but not in pituitary tumors. In particular, we have focused on an imprinted gene, Maternally Expressed Gene 3 (MEG3), which is specifically associated with clinically non-functioning pituitary adenomas of a gonadotroph lineage. MEG3 functions to suppress tumor cell growth, increase protein expression of the tumor suppressor p53, and selectively activate p53 target genes. Interestingly, MEG3 does not encode a protein but a non-coding RNA. Therefore, these studies have revealed novel mechanisms for the function of a non-coding RNA in pituitary physiology and tumorigenesis.

Somatostatin-producing atypical null cell adenoma manifesting as severe hypopituitarism and rapid deterioration--case report

Atypical adenoma has an aggressive biological character, invades the surrounding structures, and grows rapidly. Morphological malignant findings such as increasing cellularity and nuclear atypism are not involved in this entity, but some cases with overt malignant features such as significant nuclear atypism and/or necrosis are known. Null cell adenoma generally grows slowly, but hormone secretion is little understood. Atypical null cell adenoma is rare, and hormone production is unknown. A 55-year-old woman presented with severe hypopituitarism and diabetes insipidus and bilateral upper temporal quadrantanopsia. Head magnetic resonance imaging revealed a large sellar tumor compressing the optic chiasm. Transsphenoidal surgery was performed, but the tumor was partially removed because of invasion into the neuronal structures. Histological examination showed atypical null cell adenoma with significant nuclear atypism and extensive necrosis. Immunohistochemistry showed positive reaction to somatostatin. Adjuvant treatment was planned, but the tumor regrew within 3 months. Conventional irradiation resulted in slight decrease in tumor size, but she required assistance for every type of daily activity. Atypical null cell adenoma has an aggressive biological character, and immediate adjuvant treatment is essential. Somatostatin secretion was proven in this tumor type.

The genetics of pituitary adenomas

Pituitary adenomas are one of the most frequent intracranial tumors with a prevalence of clinically-apparent tumors close to 1:1000 of the general population. They are clinically significant because of hormone overproduction and/or tumor mass effects in addition to the need for neurosurgery, medical therapies and radiotherapy. The majority of pituitary adenomas have a sporadic origin with recognized genetic mutations seldom being found; somatotropinomas are an exception, presenting frequent somatic GNAS mutations. In this and other phenotypes, tumorigenesis could possibly be explained by altered function of genes implicated in cell cycle regulation, growth factors or their receptors, cell-signaling pathways, specific hormonal factors or other molecules with still unclear mechanisms of action. Genetic changes, such as allelic loss or gene amplification, and epigenetic changes, usually by promoter methylation, have been implicated in abnormal gene expression, but alternative mechanisms may be present. Familial cases of pituitary adenomas represent 5% of all pituitary tumors. MEN1 mutations cause multiple endocrine neoplasia type 1 (MEN1), while the Carney complex (CNC) is characterized by mutations in the protein kinase A regulatory subunit-1alpha (PRKAR1A) gene or changes in a locus at 2p16. Recently, a MEN1-like condition, MEN4, was found to be related to mutations in the CDKN1B gene. The clinical entity of familial isolated pituitary adenomas (FIPA) is characterized by genetic defects in the aryl hydrocarbon receptor interacting protein (AIP) gene in about 15% of all kindreds and 50% of homogenous somatotropinoma families. Identification of familial cases of pituitary adenomas is important as these tumors may be more aggressive than their sporadic counterparts.

Prognostic factors in prolactin pituitary tumors: clinical, histological, and molecular data from a series of 94 patients with a long postoperative follow-up

CONTEXT AND OBJECTIVE

Predicting pituitary tumor behavior remains a challenge. This multiparameter investigation aimed to identify markers for recurrence and progression in prolactin tumors.

DESIGN

From a cohort of patients treated for prolactin tumors by surgery, we retrospectively studied clinical data, tumor characteristics, clinical outcome, and the expression of nine genes by quantitative RT-PCR.

RESULTS

This study included 94 patients (62 females and 32 men), with long postoperative follow-up periods (mean, 138 +/- 46 months); 54.3% of patients had a macro or giant adenoma. Tumors were classified into three pathological groups based on their radiological and histological characteristics (noninvasive, 61; invasive, 22; and aggressive-invasive, 11). Immediately after surgery, 60 patients (63.8%) went into remission (prolactin level normalization). Persistently elevated prolactin levels (36.2%) were associated with increasing age, male sex, high preoperative prolactin levels, large tumor size on univariate analysis, and invasion and pathological classification on univariate and multivariate (P = 8 x 10(-10) and 3 x 10(-8)) analysis. During follow-up, 19 patients (20%) had tumors that recurred or progressed under dopamine agonist treatment. Invasion and pathological classification were associated with recurrence or progression on univariate analysis. Seven genes (ADAMTS6, CRMP1, PTTG, ASK, CCNB1, AURKB, and CENPE) were associated with tumor recurrence or progression and five of these (ADAMTS6, CRMP1, ASK, CCNB1, and CENPE) were associated with the pathological classification.

CONCLUSION

This study identifies both the clinical and histological factors that relate to prolactin tumor recurrence or progression. Molecular markers give additional information for prognosis of such tumors. Altogether, our results could influence the management of patients with pituitary tumors.

Clinicopathological study of prognostic factors in patients with pituitary adenomas and Ki-67 labeling index of more than 3%

BACKGROUND

Pituitary adenoma is generally indolent, but an aggressive subtype including atypical adenoma has uncertain prognosis, and an unclear relationship between prognosis and morphology.

AIM

To investigate the prognostic factors of adenomas with Ki-67 labeling index of more than 3%.

SUBJECTS AND METHODS

Patients with surgically treated pituitary adenomas with Ki-67 labeling index of more than 3% were retrospectively identified as 13 males and 20 females aged from 15 to 73 yr (mean 47.2 yr) among 527 patients with pituitary adenoma treated at the Department of Neurosurgery, Tohoku University and Department of Neurosurgery, Kohnan Hospital between January 2001 and December 2007.

RESULTS

The tumors included 12 cases of gross totally removed pituitary adenomas, and 21 non-totally removed adenomas. Statistical analysis found significant differences in recurrence between gross total and non-total removal (log-rank test, p<0.001), and giant adenomas had higher risk of recurrence or re-growth (log-rank test, p<0.01); 71.4% of re-growth was detected within 12 months if the patients had tumor remnants after the operation. Both immunohistochemical types of tumor and invasion of the surrounding tissue had no statistical correlation with tumor regrowth, and high Ki-67 and p53 labeling index had no relationship with duration of stable disease among these patients independently.

CONCLUSIONS

Gross total removal is the most important prognostic factor in patients with adenoma with Ki-67 labeling index of more than 3%. In contrast, giant adenoma carries higher risk of recurrence and/or re-growth. If gross total removal is not achieved immediate adjuvant therapy should be performed.

The pathogenesis of pituitary tumors

Recently there has been significant progress in our understanding of pituitary development, physiology, and pathology. New information has helped to clarify the classification of pituitary tumors. Epidemiologic analyses have identified a much higher incidence of pituitary tumors than previously thought. We review the pathogenetic factors that have been implicated in pituitary tumorigenesis and the application of novel targeted therapies that underscore the increasingly important role of the pathologist in determining accurate diagnoses and facilitating appropriate treatment of patients with these disorders.

Hormonal signaling and pituitary adenomas

In recent years the demonstration that human pituitary adenomas are monoclonal in origin provides further evidence that pituitary neoplasia arise from the replication of a single mutated cell in which growth advantage results from either activation of proto-oncogenes or inactivation of tumor suppressor genes. Mutations in common oncogenes and tumor suppressor genes are only exceptionally involved in pituitary tumors. Since pituicytes may proliferate in response to hypothalamic neurohormones, locally produced growth factors and peripheral hormones, it has been speculated that dysregulation of the signaling molecules that constitute these pathways may confer growth advantage to the target cell, finally resulting in tumor formation. The only mutational change so far recognized to be unequivocally associated with pituitary tumors occur in the Gs alpha gene (GNAS1) and cause constitutive activation of the cAMP-dependent pathway. However, other components of pituitary-specific pathways are frequently altered in their expression and activity. This review will focus on the possible impact of G proteins and other components of hormone signaling on pituitary tumorigenesis.

Pituitary adenomas in childhood: development and diagnosis

Pituitary adenomas account for approximately 2.7% of all supratentorial tumors in the pediatric age range, and children are more likely than adults to develop a functioning adenoma. X chromosome inactivation studies indicate that pituitary adenomas arise from the clonal expression of a single mutated cell, and various intracellular mechanisms contribute to tumoral transformation. Functional pituitary tumors in childhood result in physical and biochemical effects of excess production of the oversecreted hormone, such as ACTH, prolactin, human growth hormone, TSH, LH, or FSH. In the clinical approach to pituitary adenomas, it is important to establish the presence of hormonal excess prior to undertaking imaging studies.

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.

[Pituitary tumorigenesis]

Pituitary adenomas, almost invariably adenomas, account for 10% to 15% of all intracranial neoplasms and are incidentally detected in up to 27% of non selected autopsies. They are morphologically classified as microadenomas (diameter < 1 cm) or macroadenomas, which can be enclosed, invasive and/or expansive. Functionally, they are classified as secreting adenomas (PRL, GH, ACTH, TSH, LH, and FSH, and those co-secreting two or more hormones), and clinically non secreting or "non functioning" tumors. Diagnosis is based on the hypersecretion phenotype (acromegaly, Cushing, etc), and on mass effect of macroadenomas leading to neurological disturbances, mainly visual complaints and headache. Pituitary tumorigenesis mechanisms include those of primary hypothalamic versus pituitary origin, the latter is supported by evidence of pituitary adenoma monoclonality, as well as the absence of hyperplastic tissue surrounding the surgically removed tumor, and the relative independence of tumor hypothalamic control. Nevertheless, a permissive role of the hypothalamus on tumor progression is also postulated. Several molecular mechanisms involved in pituitary tumorigenesis have been unraveled including oncogenes, tumor suppressor genes and growth factors involved in neoplastic development, and will be described in this review.

Hepatocyte growth factor-regulated tyrosine kinase substrate (HGS) and guanylate kinase 1 (GUK1) are differentially expressed in GH-secreting adenomas

Pituitary tumors, adenomas in their vast majority, represent around 10-15% of the intracranial neoplasms. Pituitary carcinomas are exceedingly rare. Clinically, these neoplasms cause hormonal dysfunctions, and mass effect symptoms as headache and visual disorders in the case of macroadenomas. Pituitary tumorigenesis is still poorly understood. In order to investigate the expression of cancer-related genes in pituitary tumors, we employed a human cancer cDNA macroarray membrane with 1176 well-characterized human genes related to cancer and tumor biology. We were able to identify several differentially expressed genes, among them hepatocyte growth factor-regulated tyrosine kinase substrate (HGS) and guanylate kinase 1 (GUK1) which were over expressed in a pool of clinically nonfunctioning pituitary adenomas, compared with a spinal cord metastasis of a nonfunctioning pituitary carcinoma. HGS and GUK1 mRNA expression were chosen to be validated by quantitative RT-qPCR, however, only GUK1 had the differential expression confirmed between the adenomas and the metastasis of a pituitary carcinoma. We have also investigated HGS and GUK1 mRNA expressions in a series of 46 pituitary adenomas (18 nonfunctioning, 12 GH-secreting, nine PRL-secreting, and seven ACTH-secreting adenomas). HGS and GUK1 were significantly over expressed in GH-secreting adenomas, compared with ACTH-secreting adenomas and nonfunctioning tumors, and with PRL-secreting adenomas, respectively. We have shown that these genes, involved in tumorigenesis in other tissues, are as well over expressed in the pituitary tumors, however, their role in the oncogenesis of these tumors need to be further investigated.

[Non-functioning pituitary adenomas: clinical features and immunohistochemistry]

Clinically non-functioning pituitary adenomas do not produce clinical signs of hormonal hypersecretion. Therefore, signs and symptoms will depend on the mass effect of these adenomas over the central nervous system. Their etiopathogeny is complex and their development is probably influenced by several factors, such as hypothalamic hormones (GHRH), growth factors (FGF), proliferation factors (PCNA, and KI-67), protein P53 and the proto-oncogene c-erb-B2.

OBJECTIVE

1) Determining the clinical features of a population of 117 patients treated for clinically non-functioning pituitary adenoma (age, sex, tumor size, number of surgical procedures, development of hormonal deficiency and hyperprolactinemia). 2) Identifying, after the patients had been clinically characterized, those with clinically non-functioning adenomas with positive immunohistochemistry for hypophyseal hormones (PRL, LH, FSH, GH, TSH and ACTH). 3) Determining if the immunohistochemistry of this population was positive for the cellular proliferation factor Ki-67, protein P53 and protein C-erb-B2 and establishing a correlation with tumor size and tumor invasiveness. This will help in the evaluation of the prognostic value of these proliferation factors. 4) Confronting the results of immunohistochemistry using a standard block with the results of immunohistochemistry using a tissue micro-array.

METHOD

Study of the clinical features of 117 patients with clinically non-functioning pituitary adenoma (age, sex, tumor size, number of surgical procedures, development of hormonal deficiency and hyperprolactinemia). Immunohistochemical study (H&E) of 39 patients for hypophyseal hormones, protein P53, protein C-erb-B2, Ki-67 to establish their correlation to tumor growth. The next step was a tissue micro-array of the 39 previously studied cases, using immunohistochemistry for hypophyseal hormones, protein P 53, protein C-erb-B2, Ki-67 to establish their correlation to tumor growth.

RESULTS

There was no statistically significant difference between males and females with regards to age, tumor size and number of surgical procedures (p=0.279, p=813, p=139 respectively). There is a statistically significant correlation between the size of the tumor, the number of surgical procedures and hormonal deficiency (p=0.032, p=0.223 respectively). There was no statistically significant correlation between a positive immunohistochemistry for protein P53, protein C-erb-B2, Ki-67 and tumor size (r=0.182, p=0.396; r=-0.181, p=0.397; r=0.272, p=0.199, respectively). The tissue micro-array also did not demonstrate a correlation between positive immunohistochemistry for Ki-67 and C-erb-B2 and tumor size, but it showed a statistically significant correlation between a positive immunohistochemistry for p53 and tumor size (r=-0.696; p=001).

CONCLUSION

The biological behavior of the clinically non-functioning adenoma is similar for both sexes. The larger the tumor the greater the number of surgical procedures needed. Hormonal deficiency also becomes more significant as the size of the tumor increases. This paper suggests that a positive immunohistochemistry for p53 is negatively correlated to tumor size, thus demonstrating that it has a predictor value. However, a positive immunohistochemistry for Ki-67 and protein C-erb-B2 does not seem to be a prognostic factor for clinically non-functioning pituitary adenomas, as is the case with other neoplasias.

Pituitary radiotherapy: current controversies

External beam radiotherapy has been used extensively in the management of patients with pituitary disease. However, in view of advances in the techniques of radiotherapy planning and administration, neurosurgery and pharmacological manipulation of the pituitary, there are a growing number of questions and controversies surrounding the current and future use of pituitary radiotherapy in the management of pituitary disease.

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.

Pituitary tumors: prognostic indicators

Many factors influence the proliferation of pituitary adenomas: angiogenesis, apoptosis, growth factors, oncogenes, tumor suppressor genes, and hormone receptors. These elements can be demonstrated by immunohistochemistry and/or molecular pathology but no single factor can be used for determination of biological behavior resp. prognosis. Pituitary adenomas can be enclosed or invasive and may be very large or may be microadenomas, but the most important point for prognosis is the total resection in the first or second surgery or the reaction on treatments by drugs. Especially for residual tumor tissue proliferation, markers are important because they may indicate the growth rate and the aggressiveness of the tumor. Radiation therapy is indicated in many of these recurrent tumors and can improve the prognosis.

Adenomas hipofisários produtores de glicoproteínas: patogênese, diagnóstico e tratamento

Os adenomas hipofisários produtores de glicoproteínas compreendem duas entidades clínicas e patológicas distintas: os adenomas gonadotróficos e os tirotróficos. Embora possam ser agrupados por produzirem hormônios e/ou sub-unidades que são glicoproteínas, esses tumores se originam em tipos celulares distintos (gonadotrofos e tirotrofos) que são apenas remotamente relacionados. Os gonadotróficos estão entre os adenomas hipofisários mais comuns, correspondendo à grande maioria dos assim chamados adenomas "não-funcionantes", silenciosos ou clinicamente não-secretores, enquanto os tirotróficos são extremamente raros e clinicamente se apresentam com hipertiroidismo por secreção inapropriada de TSH. Nesse artigo, os autores revisam aspectos epidemiológicos, patológicos, patogenéticos, clínicos, diagnósticos e terapêuticos desses adenomas. Uma ênfase maior foi dada à patogênese molecular dos tumores hipofisários em geral, buscando, sempre que possível, contrastar as alterações moleculares encontradas nesses adenomas com outros tipos de adenomas hipofisários. No lado mais prático, a experiência dos autores de mais de duas décadas no diagnóstico e tratamento desses tumores na Unidade de Neuroendocrinologia da Unifesp, foi criteriosamente utilizada para discutir a literatura disponível nesses tópicos.

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.

Elevated expression of p21 (WAF1/Cip1) in hormonally active pituitary adenomas

Although most pituitary adenomas arise sporadically, molecular studies show alterations of known oncogenes and/or tumor suppressor genes in a small percentage of adenomas, and the molecular pathology of most is unknown. The p21 gene is a universal inhibitor of cyclin-dependent kinases and serves as a cell-cycle blocker and cell-growth inhibitor. Pituitary adenomas (n = 54) were immunophenotyped for hormone production (prolactin, growth hormone, adrenocorticotropin, thyrotropin, follicle-stimulating hormone, and luteinizing hormone), and expression of p21 was determined by immunohistochemistry. The percentage of cells expressing p21 for each tumor was evaluated blindly with regard to hormone status, and expression of p21 was then correlated with the results of hormone immunotyping. Results show a striking difference in the expression of p21 between immunonegative adenomas and hormone-producing tumors. Whereas 71% (10/14) of nonfunctional adenomas exhibit p21 expression in fewer than 5% of cells, 77% (31/40) of hormone-producing adenomas show expression in more than 25% of cells, and of these, 68% (21/31) show expression in more than 75% of cells. Overexpression of p21 is particularly striking for growth hormone-producing tumors, of which 92% (11/12) show expression in more than 75% of cells. Hormone-producing pituitary adenomas express much more p21 than do immunonegative adenomas. These high levels of p21 expression represent the most widespread molecular genetic alteration demonstrated to date in pituitary adenomas.

Pathogenesis of prolactinomas

In recent years the demonstration that human pituitary adenomas are monoclonal in origin provides further evidence that pituitary neoplasia arise from the replication of a single mutated cell in which growth advantage results from either activation of proto-oncogenes or inactivation of tumor suppressor genes. However, with the exception of one RAS mutation identified in a single unusually aggressive prolactinoma resistant to dopaminergic inhibition that resulted to be lethal, no mutational changes have been so far detected in prolactinomas. In the absence of genetic changes, modifications in the level of expression of oncogenes or tumor suppressor genes have been detected in these tumors, although it is unknown whether these changes have a causative role or are a secondary event. Indeed, our knowledge on the molecular events involved in lactotroph proliferation is even more limited in comparison to the other tumor types, since these tumors are very infrequently surgically removed and therefore available for molecular biology studies. In this respect, it is worth noting that the molecular and biological abnormalities so far described in prolactinomas mainly concern aggressive and atypical tumors and likely do not apply to the typical prolactinomas, that are characterized by good response to medical treatment and a very low growth rate.

Bases moleculares dos adenomas hipofisários com ênfase nos somatotropinomas

Esta revisão descreve as bases moleculares dos adenomas hipofisários com ênfase nos tumores secretores de GH (somatotropinomas). São discutidos os papéis de genes de supressão tumoral (como RB1, MEN-1) e de oncogenes (como gsp, PTTG) na iniciação e progressão destes tumores. A caracterização destes marcadores moleculares pode ajudar na compreensão do comportamento tumoral, auxiliando a conduta terapêutica. Entretanto, apesar dos recentes avanços, ainda não é totalmente conhecida a seqüência de alterações genéticas envolvidas na patogênese destes adenomas.

Isolation and characterization of a novel pituitary tumor apoptosis gene

To determine mechanisms for pituitary neoplasia we used methylation-sensitive arbitrarily primed-PCR to isolate novel genes that are differentially methylated relative to normal pituitary. We report the isolation of a novel differentially methylated chromosome 22 CpG island-associated gene (C22orf3). Sodium bisulfite sequencing of pooled tumor cohorts, used in the isolation of this gene, showed that only a proportion of the adenomas within the pools were methylated; however, expression analysis by quantitative RT-PCR of individual adenoma irrespective of subtype showed the majority (30 of 38; 79%) failed to express this gene relative to normal pituitary. Sodium bisulfite sequencing of individual adenomas showed that 6 of 30 (20%) that failed to express pituitary tumor apoptosis gene (PTAG) were methylated; however, genetic change as determined by loss of heterozygosity and sequence analysis was not apparent in the remaining tumors that failed to express this gene. In those cases where the CpG island of these genes was methylated it was invariably associated with loss of transcript expression. Enforced expression of C22orf3 in AtT20 cells had no measurable effects on cell proliferation or viability; however, in response to bromocriptine challenge (10-40 microm) cells expressing this gene showed a significantly augmented apoptotic response as determined by both acridine orange staining and TUNEL labeling. The apoptotic response to bromocriptine challenge was inhibited in coincubation experiments with the general caspase inhibitor z-VAD-fmk. In addition, in time course experiments, direct measurement of active caspases by fluorochrome-labeled inhibition of caspases, showed an augmented increase (approximately 2.4 fold) in active caspases in response to bromocriptine challenge in cells expressing C22orf3 relative to those harboring an empty vector control. The pituitary tumor derivation and its role in apoptosis of this gene led us to assign the acronym PTAG to this gene and its protein product. The ability of cells, showing reduced expression of PTAG, to evade or show a blunted apoptotic response may underlie oncogenic transformation in both the pituitary and other tumor types.