Common genetic changes in hereditary and sporadic pituitary adenomas detected by comparative genomic hybridization

SDHx mutation and pituitary adenoma: can in vivo 1H-MR spectroscopy unravel the link?

Germline mutations in genes encoding succinate dehydrogenase (SDH) are frequently involved in pheochromocytoma/paraganglioma (PPGL) development and were implicated in patients with the '3PAs' syndrome (associating pituitary adenoma (PA) and PPGL) or isolated PA. However, the causality link between SDHx mutation and PA remains difficult to establish, and in vivo tools for detecting hallmarks of SDH deficiency are scarce. Proton magnetic resonance spectroscopy (1H-MRS) can detect succinate in vivo as a biomarker of SDHx mutations in PGL. The objective of this study was to demonstrate the causality link between PA and SDH deficiency in vivo using 1H-MRS as a novel noninvasive tool for succinate detection in PA. Three SDHx-mutated patients suffering from a PPGL and a macroprolactinoma and one patient with an apparently sporadic non-functioning pituitary macroadenoma underwent MRI examination at 3 T. An optimized 1H-MRS semi-LASER sequence (TR = 2500 ms, TE = 144 ms) was employed for the detection of succinate in vivo. Succinate and choline-containing compounds were identified in the MR spectra as single resonances at 2.44 and 3.2 ppm, respectively. Choline compounds were detected in all the tumors (three PGL and four PAs), while a succinate peak was only observed in the three macroprolactinomas and the three PGL of SDHx-mutated patients, demonstrating SDH deficiency in these tumors. In conclusion, the detection of succinate by 1H-MRS as a hallmark of SDH deficiency in vivo is feasible in PA, laying the groundwork for a better understanding of the biological link between SDHx mutations and the development of these tumors.

Proteogenomic landscape and clinical characterization of GH-producing pituitary adenomas/somatotroph pituitary neuroendocrine tumors

The clinical characteristics of growth hormone (GH)-producing pituitary adenomas/somatotroph pituitary neuroendocrine tumors (GHomas/somatotroph PitNETs) vary across patients. In this study, we aimed to integrate the genetic alterations, protein expression profiles, transcriptomes, and clinical characteristics of GHomas/somatotroph PitNETs to identify molecules associated with acromegaly characteristics. Targeted capture sequencing and copy number analysis of 36 genes and nontargeted proteomics analysis were performed on fresh-frozen samples from 121 sporadic GHomas/somatotroph PitNETs. Targeted capture sequencing revealed GNAS as the only driver gene, as previously reported. Classification by consensus clustering using both RNA sequencing and proteomics revealed many similarities between the proteome and the transcriptome. Gene ontology analysis was performed for differentially expressed proteins between wild-type and mutant GNAS samples identified by nontargeted proteomics and involved in G protein-coupled receptor (GPCR) pathways. The results suggested that GNAS mutations impact endocrinological features in acromegaly through GPCR pathway induction. ATP2A2 and ARID5B correlated with the GH change rate in the octreotide loading test, and WWC3, SERINC1, and ZFAND3 correlated with the tumor volume change rate after somatostatin analog treatment. These results identified a biological connection between GNAS mutations and the clinical and biochemical characteristics of acromegaly, revealing molecules associated with acromegaly that may affect medical treatment efficacy.

Clinical Biology of the Pituitary Adenoma

All endocrine glands are susceptible to neoplastic growth, yet the health consequences of these neoplasms differ between endocrine tissues. Pituitary neoplasms are highly prevalent and overwhelmingly benign, exhibiting a spectrum of diverse behaviors and impact on health. To understand the clinical biology of these common yet often innocuous neoplasms, we review pituitary physiology and adenoma epidemiology, pathophysiology, behavior, and clinical consequences. The anterior pituitary develops in response to a range of complex brain signals integrating with intrinsic ectodermal cell transcriptional events that together determine gland growth, cell type differentiation, and hormonal production, in turn maintaining optimal endocrine health. Pituitary adenomas occur in 10% of the population; however, the overwhelming majority remain harmless during life. Triggered by somatic or germline mutations, disease-causing adenomas manifest pathogenic mechanisms that disrupt intrapituitary signaling to promote benign cell proliferation associated with chromosomal instability. Cellular senescence acts as a mechanistic buffer protecting against malignant transformation, an extremely rare event. It is estimated that fewer than one-thousandth of all pituitary adenomas cause clinically significant disease. Adenomas variably and adversely affect morbidity and mortality depending on cell type, hormone secretory activity, and growth behavior. For most clinically apparent adenomas, multimodal therapy controlling hormone secretion and adenoma growth lead to improved quality of life and normalized mortality. The clinical biology of pituitary adenomas, and particularly their benign nature, stands in marked contrast to other tumors of the endocrine system, such as thyroid and neuroendocrine tumors.

Pediatric pituitary adenoma and medulloblastoma in the setting of p53 mutation: case report and review of the literature

Li-Fraumeni syndrome is a cancer predisposition condition associated with various tumor types. We present the case of a 6-year-old boy who initially presented with a pituitary adenoma that was successfully treated with surgery. It ultimately recurred, requiring further surgical intervention followed by proton beam therapy. He later developed a medulloblastoma, and genetic testing revealed TP53 germline mutation. The patient underwent gross total resection of this medulloblastoma, followed by proton-based craniospinal irradiation and adjuvant chemotherapy. He remained disease-free 12 months after radiation and 7 months after chemotherapy. Current literature does not report pituitary adenoma as the initial central nervous manifestation in Li-Fraumeni syndrome. Early genetic testing should be considered in pediatric patients who present with such rare tumor types to help identify cancer predisposing conditions. Furthermore, as evidenced by our case, the management of multiple brain tumors in the pediatric population poses challenges. A multidisciplinary approach involving neurosurgery, pediatric oncology, pathology, and radiation oncology remains crucial to optimize patient outcomes.

USP8 and TP53 Drivers are Associated with CNV in a Corticotroph Adenoma Cohort Enriched for Aggressive Tumors

CONTEXT

Pituitary corticotroph adenomas are rare tumors that can be associated with excess adrenocorticotropin (ACTH) and adrenal cortisol production, resulting in the clinically debilitating endocrine condition Cushing disease. A subset of corticotroph tumors behave aggressively, and genomic drivers behind the development of these tumors are largely unknown.

OBJECTIVE

To investigate genomic drivers of corticotroph tumors at risk for aggressive behavior.

DESIGN

Whole-exome sequencing of patient-matched corticotroph tumor and normal deoxyribonucleic acid (DNA) from a patient cohort enriched for tumors at risk for aggressive behavior.

SETTING

Tertiary care center.

PATIENTS

Twenty-seven corticotroph tumors from 22 patients were analyzed. Twelve tumors were macroadenomas, of which 6 were silent ACTH tumors, 2 were Crooke's cell tumors, and 1 was a corticotroph carcinoma.

INTERVENTION

Whole-exome sequencing.

MAIN OUTCOME MEASURE

Somatic mutation genomic biomarkers.

RESULTS

We found recurrent somatic mutations in USP8 and TP53 genes, both with higher allelic fractions than other somatic mutations. These mutations were mutually exclusive, with TP53 mutations occurring only in USP8 wildtype (WT) tumors, indicating they may be independent driver genes. USP8-WT tumors were characterized by extensive somatic copy number variation compared with USP8-mutated tumors. Independent of molecular driver status, we found an association between invasiveness, macroadenomas, and aneuploidy.

CONCLUSIONS

Our data suggest that corticotroph tumors may be categorized into a USP8-mutated, genome-stable subtype versus a USP8-WT, genome-disrupted subtype, the latter of which has a TP53-mutated subtype with high level of chromosome instability. These findings could help identify high risk corticotroph tumors, namely those with widespread CNV, that may need closer monitoring and more aggressive treatment.

[Genetic basis of Cushing's disease in children and targeted therapeutic future perspectives]

Cushing's disease (CD) is a multisystem disorder of a cortisol excess caused by ACTH -secreting pituitary tumor (corticotropinoma). CD in children is due to somatic or germline mutations with the late onset causing multiple endocrine tumors. If not treated, hypercortisolism leads to severe decrease in quality of life and life-threating conditions. The first-line treatment for CD is pituitary surgery, which might be followed by complications and relapse with necessity of additional surgery or initiations of second-line treatment. Recent studies of molecular basis of corticotropinoma development made it possible to employ medical therapy in CD. Understanding of corticotropinoma etiology and pathogenesis is an important part of education for pediatric endocrinologists since we need to keep in mind possibility of multisystem disorder in case of CD in children and because medical therapy might gain more important role for CD treatment in future.The most actual genetic aspects of corticotroph adenomas growth and the medical treatment opportunities are present in this review.

Chromosomal instability in the prediction of pituitary neuroendocrine tumors prognosis

The purpose of this study was to analyze the impact of copy number variations (CNV) on sporadic pituitary neuroendocrine tumors (PitNETs) prognosis, to identify specific prognosis markers according to the known clinico-pathological classification. CGH array analysis was performed on 195 fresh-frozen PitNETs (56 gonadotroph, 11 immunonegative, 56 somatotroph, 39 lactotroph and 33 corticotroph), with 5 years post-surgery follow-up (124 recurrences), classified according to the five-tiered grading classification (invasion, Ki-67, mitotic index and p53 positivity). Effect of alterations on recurrence was studied using logistic regression models. Transcriptomic analysis of 32 lactotroph tumors was performed. The quantity of CNV was dependent on tumor type: higher in lactotroph (median(min–max) = 38% (0–97) of probes) compared to corticotroph (11% (0–77)), somatotroph (5% (0–99)), gonadotroph (0% (0–10)) and immunonegative tumors (0% (0–17). It was not predictive of recurrence in the whole cohort. In lactotroph tumors, genome instability, especially quantity of gains, significantly predicted recurrence independently of invasion and proliferation (p-value = 0.02, OR = 1.2). However, no specific CNV was found as a prognostic marker. Transcriptomic analysis of the genes included in the CNV and associated with prognosis didn’t show significantly overrepresented pathway. In somatotroph and corticotroph tumors, USP8 and GNAS mutations were not associated with genome disruption or recurrence respectively. To conclude, CGH array analysis showed genome instability was dependent on PitNET type. Lactotroph tumors were highly altered and the quantity of altered genome was associated with poorer prognosis though the mechanism is unclear, whereas gonadotroph and immunonegative tumors showed the same ‘quiet’ profile, leaving the mechanism underlying tumorigenesis open to question.

Coexistence of Growth Hormone Deficiency and Pituitary Microadenoma in a Child with Unique Mosaic Turner Syndrome: A Case Report and Literature Review

Turner syndrome (TS) is a genetic disorder with phenotypic heterogeneity caused by the monosomy or structural abnormalities of the X chromosome, and it has a prevalence of about 1/2500 females live birth. The variable clinical features of TS include short stature, gonadal failure, and skeletal dysplasia. The association with growth hormone (GH) deficiency or other hypopituitarism in TS is extremely rare, with only a few case reports published in the literature. Here, we report the first case of a patient with mosaic TS with complete GH deficiency and pituitary microadenoma, and we include the literature review. During the work-up of the patient for severe short stature, three GH provocation tests revealed peak GH levels of less than 5 ng/mL, which was compatible with complete GH deficiency. Sella magnetic resonance imaging showed an 8 mm non-enhancing pituitary adenoma with mild superior displacement of the optic chiasm. Karyotyping revealed the presence of ring chromosome X and monosomy X (46,X,r(X)/45,X/46,X,psu dic r(X;X)), which indicated a mosaic TS. It is important to consider not only chromosome analyses in females with short stature, but also the possibility of the coexistence of complete GH deficiency accompanying pituitary lesions in TS. In conclusion, the present study reports the first case of GH deficiency and pituitary adenoma in a patient with rare mosaic TS, which extends the genotype-phenotype spectrum for TS.

Pangenomic Classification of Pituitary Neuroendocrine Tumors

Pituitary neuroendocrine tumors (PitNETs) are common, with five main histological subtypes: lactotroph, somatotroph, and thyrotroph (POU1F1/PIT1 lineage); corticotroph (TBX19/TPIT lineage); and gonadotroph (NR5A1/SF1 lineage). We report a comprehensive pangenomic classification of PitNETs. PitNETs from POU1F1/PIT1 lineage showed an epigenetic signature of diffuse DNA hypomethylation, with transposable elements expression and chromosomal instability (except for GNAS-mutated somatotrophs). In TPIT lineage, corticotrophs were divided into three classes: the USP8-mutated with overt secretion, the USP8-wild-type with increased invasiveness and increased epithelial-mesenchymal transition, and the large silent tumors with gonadotroph transdifferentiation. Unexpected expression of gonadotroph markers was also found in GNAS-wild-type somatotrophs (SF1 expression), challenging the current definition of SF1/gonadotroph lineage. This classification improves our understanding and affects the clinical stratification of patients with PitNETs.

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.

Large Genomic Aberrations in Corticotropinomas Are Associated With Greater Aggressiveness

CONTEXT

Genomic losses/gains are associated with cancer progression and prognosis. In pituitary adenomas, analyses of copy number variations (CNVs) have shown that a subset of adenomas have higher genomic variability. However, whether CNVs are associated with tumor aggressiveness and prognosis has not been determined.

OBJECTIVE

We hypothesized that somatic CNVs of pituitary tumors may play a role in the progression and aggressiveness of pituitary corticotropinomas in children and adolescents.

SAMPLES AND DESIGN

Paired germline and tumor DNA samples from 27 pediatric patients with Cushing disease (CD), were subjected to whole exome sequencing. Somatic CNVs were identified using the ExomeDepth tool. Clinical, histological, and biochemical data from the patients were collected and correlated with the results of the CNV analysis.

RESULTS

Chromosomal instability, involving 23% to 59% of the tumor genome, was noted in 5 of the 27 samples (18.5%). The patients with tumors showing chromosomal instability had similar clinical and biochemical characteristics to the remaining patients, except for tumor size, which was larger (median size 18 mm vs 5.5 mm, P = 0.005). Tumors with chromosomal instability were also associated with a higher rate of invasion of the cavernous sinus (P = 0.029). There was insufficient information on persistence or recurrence of CD to determine whether the risk was higher in those with chromosomal instability.

CONCLUSIONS

A subgroup of corticotropinomas demonstrates chromosomal instability that is associated with markers of aggressiveness of these adenomas. It appears that more genomic gains/losses in a few, rare corticotropinomas may predict poorer prognosis for pediatric patients with CD.

Pediatric pituitary adenomas in Northeast Mexico. A follow-up study

PURPOSE

To review incidence, treatment and outcome of pediatric pituitary adenomas (PAs).

METHODS

A follow-up study patients with the age of ≤19 years old who were treated from 1995 to 2015 in Mexico.

RESULTS

Out of 1244 diagnosed PA, 43 patients were children (35 females, 8 males) with a mean age of 17.2 years. The majority were macroadenomas (70%) with prolactinomas (PRL) dominating (63%) followed by non-functioning adenomas (21%). In total, 40% were diagnosed as invasive. Growth hormone (GH) secreting adenomas, adrenocorticotropic hormone secreting and mixed GH-PRL secreting were rare. The treatment modalities were dopamine agonists and surgery. The average treatment time was 44 months with an average follow-up period of 104 months. Sixty-eight percent (27/40) of the patients had complete response after long time follow-up. Thirty-one percent did not respond to treatment whereof three patients died due to advanced disease and late intervention. The principal causes for treatment failure were treatment resistance, late intervention and poor patient compliance.

CONCLUSIONS

Sixty eight percent had complete treatment response without any sign of disease, while ~31% did not respond to treatment or did not comply to follow up/treatment. Optimized early diagnose, treatment methods with early intervention, long time follow-up and with better measures for patient compliance should improve outcomes.

Genomic Alterations and Complex Subclonal Architecture in Sporadic GH-Secreting Pituitary Adenomas

PURPOSE

The molecular pathogenesis of growth hormone-secreting pituitary adenomas is not fully understood. Cytogenetic alterations might serve as alternative driver events in GNAS mutation-negative somatotroph tumors.

EXPERIMENTAL DESIGN

We performed cytogenetic profiling of pituitary adenomas obtained from 39 patients with acromegaly and four patients with sporadic gigantism by using array comparative genomic hybridization analysis. We explored intratumor DNA copy-number heterogeneity in two tumor samples by using DNA fluorescence in situ hybridization (FISH).

RESULTS

Based on copy-number profiles, we found two groups of adenomas: a low-copy-number alteration (CNA) group (<12% of genomic disruption, 63% of tumors) and a high-CNA group (24% to 45% of genomic disruption, 37% of tumors). Arm-level CNAs were the most common abnormalities. GNAS mutation-positive adenomas belonged exclusively to the low-CNA group, whereas a subgroup of GNAS mutation-negative adenomas had a high degree of genomic disruption. We detected chromothripsis-related CNA profiles in two adenoma samples from an AIP mutation-positive patient with acromegaly and a patient with sporadic gigantism. RNA sequencing of these two samples identified 17 fusion transcripts, most of which resulted from chromothripsis-related chromosomal rearrangements. DNA FISH analysis of these samples demonstrated a subclonal architecture with up to six distinct cell populations in each tumor.

CONCLUSION

Somatotroph pituitary adenomas display substantial intertumor and intratumor DNA copy-number heterogeneity, as revealed by variable CNA profiles and complex subclonal architecture. The extensive cytogenetic burden in a subgroup of GNAS mutation-negative somatotroph adenomas points to an alternative tumorigenic pathway linked to genomic instability.

PRKAR1A mutation causing pituitary-dependent Cushing disease in a patient with Carney complex

CONTEXT

Carney complex (CNC) is an autosomal dominant condition caused, in most cases, by an inactivating mutation of the PRKAR1A gene, which encodes for the type 1 alpha regulatory subunit of protein kinase A. CNC is characterized by the occurrence of endocrine overactivity, myxomas and typical skin manifestations. Cushing syndrome due to primary pigmented nodular adrenocortical disease (PPNAD) is the most frequent endocrine disease observed in CNC.

CASE DESCRIPTION

Here, we describe the first case of a patient with CNC and adrenocorticotropic hormone (ACTH)-dependent Cushing disease due to a pituitary corticotroph adenoma. Loss-of-heterozygosity analysis of the pituitary tumour revealed loss of the wild-type copy of PRKAR1A, suggesting a role of this gene in the pituitary adenoma development.

CONCLUSION

PRKAR1A loss-of-function mutations can rarely lead to ACTH-secreting pituitary adenomas in CNC patients. Pituitary-dependent disease should be considered in the differential diagnosis of Cushing syndrome in CNC patients.

Whole-Exome Sequencing Study of Thyrotropin-Secreting Pituitary Adenomas

CONTEXT

Thyrotropin (TSH)-secreting pituitary adenomas (TSHomas) are a rare cause of hyperthyroidism, and the genetic aberrations responsible remain unknown.

OBJECTIVE

To identify somatic genetic abnormalities in TSHomas.

DESIGN AND SETTING

A single-nucleotide polymorphism (SNP) array analysis was performed on 8 TSHomas. Four tumors with no allelic losses or limited loss of heterozygosity were selected, and whole-exome sequencing was performed, including their corresponding blood samples. Somatic variants were confirmed by Sanger sequencing. A set of 8 tumors was also assessed to validate candidate genes.

PATIENTS

Twelve patients with sporadic TSHomas were examined.

RESULTS

The overall performance of whole-exome sequencing was good, with an average coverage of each base in the targeted region of 97.6%. Six DNA variants were confirmed as candidate driver mutations, with an average of 1.5 somatic mutations per tumor. No mutations were recurrent. Two of these mutations were found in genes with an established role in malignant tumorigenesis (SMOX and SYTL3), and 4 had unknown roles (ZSCAN23, ASTN2, R3HDM2, and CWH43). Similarly, an SNP array analysis revealed frequent chromosomal regions of copy number gains, including recurrent gains at loci harboring 4 of these 6 genes.

CONCLUSIONS

Several candidate somatic mutations and changes in copy numbers for TSHomas were identified. The results showed no recurrence of mutations in the tumors studied but a low number of mutations, thereby highlighting their benign nature. Further studies on a larger cohort of TSHomas, along with the use of epigenetic and transcriptomic approaches, may reveal the underlying genetic lesions.

Landscape of Genomic Alterations in Pituitary Adenomas

Purpose: Pituitary adenomas are the second most common primary brain tumor, yet their genetic profiles are incompletely understood.Experimental Design: We performed whole-exome sequencing of 42 pituitary macroadenomas and matched normal DNA. These adenomas included hormonally active and inactive tumors, ones with typical or atypical histology, and ones that were primary or recurrent.Results: We identified mutations, insertions/deletions, and copy-number alterations. Nearly one-third of samples (29%) had chromosome arm-level copy-number alterations across large fractions of the genome. Despite such widespread genomic disruption, these tumors had few focal events, which is unusual among highly disrupted cancers. The other 71% of tumors formed a distinct molecular class, with somatic copy number alterations involving less than 6% of the genome. Among the highly disrupted group, 75% were functional adenomas or atypical null-cell adenomas, whereas 87% of the less-disrupted group were nonfunctional adenomas. We confirmed this association between functional subtype and disruption in a validation dataset of 87 pituitary adenomas. Analysis of previously published expression data from an additional 50 adenomas showed that arm-level alterations significantly impacted transcript levels, and that the disrupted samples were characterized by expression changes associated with poor outcome in other cancers. Arm-level losses of chromosomes 1, 2, 11, and 18 were significantly recurrent. No significantly recurrent mutations were identified, suggesting no genes are altered by exonic mutations across large fractions of pituitary macroadenomas.Conclusions: These data indicate that sporadic pituitary adenomas have distinct copy-number profiles that associate with hormonal and histologic subtypes and influence gene expression. Clin Cancer Res; 23(7); 1841-51. ©2016 AACR.

Germline deletion and a somatic mutation of the PRKAR1A gene in a Carney complex-related pituitary adenoma

OBJECTIVE

The objective was to assess involvement of loss of the PRKAR1A gene encoding a type 1α regulatory subunit of cAMP-dependent protein kinase A located on 17q24 in a Carney complex (CNC)-related pituitary adenoma.

DESIGN

We investigated aberrations of the PRKAR1A gene in a CNC patient with a GH-producing pituitary adenoma, whose family has three other members with probable CNC.

METHODS

A gene mutation was identified by a standard DNA sequencing method based on PCR. DNA copy number was measured to evaluate allelic loss on 17q24 by quantitative PCR. The breakpoints of deletion were determined by cloning a rearranged region in the deleted allele.

RESULTS

A PRKAR1A mutation of c.751_758del8 (p.S251LfsX16) was found in genomic DNA obtained from a pituitary adenoma, but not leukocytes from the patient. Reduced DNA copy number at loci including the PRKAR1A gene on 17q24 was detected in both the tumor and leukocytes, suggesting a deletion at the loci at the germline level. The deletion size was determined to be ∼ 0.5 Mb and this large deletion was also found in two other family members.

CONCLUSION

This is the first case showing a CNC-related pituitary adenoma with the combination of somatic mutation and a large inherited deletion of the PRKAR1A gene. Biallelic inactivation of PRKAR1A appears to be necessary for the development of CNC-related pituitary adenoma.

Aggressive pituitary tumors

Pituitary adenomas are common intracranial tumors that are mainly considered as benign. Rarely, these tumors can exhibit an aggressive behavior, characterized by gross invasion of the surrounding tissues, resistance to conventional treatment leading to early and frequent recurrences. Even more rarely, pituitary tumors can give rise to cerebrospinal or systemic metastases qualifying as pituitary carcinomas according to the latest WHO definition. In the same classification, a subset of tumors with relatively distinct histopathological features was identified and defined as atypical adenomas designated to follow a more aggressive clinical course. This classification, although clinically useful, does not provide an accurate correlation between histopathological findings and the clinical behavior of these tumors, neither is it adequate to convey the precise features of 'aggressive' tumors. Thus, 'aggressive' pituitary adenomas need to be properly defined with clinical, radiological, histological and molecular markers in order to identify patients at increased risk of early recurrence or subsequent tumor progression. At present, no single marker or classification system of pituitary tumor aggressiveness exists, and clinically useful information in the literature is insufficient to guide diagnostic and therapeutic decisions. Treatment of patients with aggressive pituitary tumors is challenging since conventional treatments often fail, necessitating multiple surgical procedures with additional radiotherapy. Although traditional chemotherapy applied in other neuroendocrine tumors has not been shown to be efficacious, newer agents, particularly temozolomide, have shown promising results and are currently used despite the lack of data from a randomized prospective trial. Molecular targeted therapies such as mTOR and epidermal growth factor inhibitors have also been applied and might prove to be useful in the management of these patients. In the present review, we provide information regarding the epidemiology and clinical, histopathological and molecular features of aggressive pituitary tumors using recent employed definitions. In addition, we review currently employed therapeutic means providing a therapeutic algorithm and highlight the need to identify more specific disease-related and prognostic markers and the necessity for central registration of these tumors.

Aggressive pituitary adenomas--diagnosis and emerging treatments

The WHO categorizes pituitary tumours as typical adenomas, atypical adenomas and pituitary carcinomas, with typical adenomas constituting the major class. However, the WHO classification does not provide an accurate correlation between histopathological findings and clinical behaviour. Tumours lacking typical histological features are classified as atypical, but not all are clinically atypical or exhibit aggressive behaviour. Pituitary carcinomas, by definition, have craniospinal or systemic metastases, although not all display classical cytological features of malignancy. Aggressive pituitary adenomas, defined from a clinical perspective, have earlier and more frequent recurrences and can be resistant to conventional treatments. Specific biomarkers have not yet been identified that can distinguish between clinically aggressive and nonaggressive pituitary adenomas, although the antigen Ki-67 proliferation index might be of value. This Review highlights the need to develop new biomarkers to facilitate the early detection of clinically aggressive pituitary adenomas and discusses emerging markers that hold promise for their identification. Defining aggressiveness is of crucial importance for improving the management of patients by enhancing prognostic predictions and effectiveness of treatment. New drugs, such as temozolomide, have potential use in the management of these patients; anti-VEGF therapy, mTOR and tyrosine kinase inhibitors are also potentially useful in managing selected patients.

Management of endocrine disease: clinicopathological classification and molecular markers of pituitary tumours for personalized therapeutic strategies

Pituitary tumours, the most frequent intracranial tumour, are historically considered benign. However, various pieces of clinical evidence and recent advances in pathological and molecular analyses suggest the need to consider these tumours as more than an endocrinological disease, despite the low incidence of metastasis. Recently, we proposed a new prognostic clinicopathological classification of these pituitary tumours, according to the tumour size (micro, macro and giant), type (prolactin, GH, FSH/LH, ACTH and TSH) and grade (grade 1a, non-invasive; 1b, non-invasive and proliferative; 2a, invasive; 2b, invasive and proliferative and 3, metastatic). In addition to this classification, numerous molecular prognostic markers have been identified, allowing a better characterisation of tumour behaviour and prognosis. Moreover, clinical and preclinical studies have demonstrated that pituitary tumours could be treated by some chemotherapeutic drugs or new targeted therapies. Our improved classification of these tumours should now allow the identification of prognosis markers and help the clinician to propose personalised therapies to selected patients presenting tumours with a high risk of recurrence.

Familial pituitary tumors

Pituitary adenomas are benign intracranial neoplasms that present a major clinical concern due to hormone overproduction and/or tumor mass effects. The majority of pituitary adenomas occur sporadically; however, familial cases are increasingly being recognized, such as multiple endocrine neoplasia type 1 (MEN1), Carney complex (CNC), and familial isolated pituitary adenoma (FIPA). Familial pituitary tumors appear to differ from their sporadic counterparts both in their genetic basis and in clinical characteristics. Evidence suggests that, especially in MEN1 and FIPA, tumors are more aggressive and affect patients at a younger age, therefore justifying the importance of early diagnosis, while in Carney complex pituitary hyperplasia is common. The genetic alterations responsible for the formation of familial pituitary syndromes include the MEN1 gene, responsible for about 80% of MEN1 cases, the regulatory subunit of the protein kinase A, PRKAR1A, responsible for about 70% of Carney complex cases, and AIP, the gene coding the aryl hydrocarbon receptor interacting protein, responsible for about 20% of FIPA cases. Rarely other genes have also been found responsible for familial pituitary adenoma cases. McCune-Albright syndrome (MAS) also has a genetic origin due to mosaic mutations in the G protein-coupled α subunit coded by the GNAS1 gene. In this chapter, we summarize the genetic and clinical characteristics of these familial pituitary syndromes and MAS.

Aggressive and malignant prolactin pituitary tumors: pathological diagnosis and patient management

According to the World Health Organization classification of pituitary tumors, only tumors with systemic metastasis must be considered as carcinomas. Invasive tumors with multiple recurrences are only classified as aggressive tumors or "atypical adenomas". To illustrate the problems encountered in the pathological diagnosis of pituitary carcinoma and in patient management, we present two male patients operated on for an aggressive prolactin pituitary adenoma with and without metastasis. In case 1, 5 surgeries, 3 irradiations, increased doses of dopamine agonists, and trials of temozolomide and carboplatine-VP16 failed to control tumor progression and the appearance of metastases which lead to death 16 years after onset. In case 2, based on the initial diagnosis of an aggressive-invasive adenoma that was resistant to dopamine agonists, gamma-Knife irradiation was initially performed on the intra-cavernous remnant. Eight years after onset, the remnant remained stabilized and the plasma PRL normalized under dopamine agonist. From these 2 cases alongside other cases found in the literature, we propose that the association of certain clinical signs (male sex, dopamine-resistant hyperprolactinemia), radiological signs (invasive macro or giant tumor on MRI) and histological signs (angiogenesis, Ki-67 > 3%, p53 positive, mitoses >2 per high power field, vascular invasion, up-regulation of genes related to invasion and proliferation, and allelic loss of chromosome 11) might suggest aggressiveness and be suspicious of malignancy before the appearance of metastasis. The early detection of an aggressive phenotype of a prolactin pituitary tumor should permit the earlier establishment of the optimum therapeutic strategy associating surgery and radiotherapy to delay or inhibit metastasis.

A new prognostic clinicopathological classification of pituitary adenomas: a multicentric case-control study of 410 patients with 8 years post-operative follow-up

Pituitary adenomas are currently classified by histological, immunocytochemical and numerous ultrastructural characteristics lacking unequivocal prognostic correlations. We investigated the prognostic value of a new clinicopathological classification with grades based on invasion and proliferation. This retrospective multicentric case-control study comprised 410 patients who had surgery for a pituitary tumour with long-term follow-up. Using pituitary magnetic resonance imaging for diagnosis of cavernous or sphenoid sinus invasion, immunocytochemistry, markers of the cell cycle (Ki-67, mitoses) and p53, tumours were classified according to size (micro, macro and giant), type (PRL, GH, FSH/LH, ACTH and TSH) and grade (grade 1a: non-invasive, 1b: non-invasive and proliferative, 2a: invasive, 2b: invasive and proliferative, and 3: metastatic). The association between patient status at 8-year follow-up and age, sex, and classification was evaluated by two multivariate analyses assessing disease- or recurrence/progression-free status. At 8 years after surgery, 195 patients were disease-free (controls) and 215 patients were not (cases). In 125 of the cases the tumours had recurred or progressed. Analyses of disease-free and recurrence/progression-free status revealed the significant prognostic value (p < 0.001; p < 0.05) of age, tumour type, and grade across all tumour types and for each tumour type. Invasive and proliferative tumours (grade 2b) had a poor prognosis with an increased probability of tumour persistence or progression of 25- or 12-fold, respectively, as compared to non-invasive tumours (grade 1a). This new, easy to use clinicopathological classification of pituitary endocrine tumours has demonstrated its prognostic worth by strongly predicting the probability of post-operative complete remission or tumour progression and so could help clinicians choose the best post-operative therapy.

Biomarkers of aggressive pituitary adenomas

Pituitary adenomas exhibit a wide range of behaviors. The prediction of aggressive or malignant behavior in pituitary adenomas remains challenging; however, the utility of biomarkers is rapidly evolving. In this review, we discuss potential biomarkers as they relate to aggressive behavior in pituitary adenomas. While detailed histological subtyping remains the best independent predictor of aggressive behavior in the majority of cases, evidence suggests that the additional analyses of FGFR4, MMP, PTTG, Ki-67, p53, and deletions in chromosome 11 may contribute to decisions concerning management of aggressive pituitary adenomas.

Functional screen analysis reveals miR-26b and miR-128 as central regulators of pituitary somatomammotrophic tumor growth through activation of the PTEN-AKT pathway

MicroRNAs (miRNAs) have been involved in the pathogenesis of different types of cancer; however, their function in pituitary tumorigenesis remains poorly understood. Cyclic-AMP-dependent protein kinase-defective pituitaries occasionally form aggressive growth-hormone (GH)-producing pituitary tumors in the background of hyperplasia caused by haploinsufficiency of the protein kinase's main regulatory subunit, PRKAR1A. The molecular basis for this development remains unknown. We have identified a 17-miRNA signature of pituitary tumors formed in the background of hyperplasia (caused in half of the cases by PRKAR1A-mutations). We selected two miRNAs on the basis of their functional screen analysis: inhibition of miR-26b expression and upregulation of miR-128 suppressed the colony formation ability and invasiveness of pituitary tumor cells. Furthermore, we identified that miR-26b and miR-128 affected pituitary tumor cell behavior through regulation of their direct targets, PTEN and BMI1, respectively. In addition, we found that miR-128 through BMI1 direct binding on the PTEN promoter affected PTEN expression levels and AKT activity in the pituitary tumor cells. Our in vivo data revealed that inhibition of miR-26b and overexpression of miR-128 could suppress pituitary GH3 tumor growth in xenografts. Taken together, we have identified a miRNA signature for GH-producing pituitary tumors and found that miR-26b and miR-128 regulate the activity of the PTEN-AKT pathway in these tumors. This is the first suggestion of the possible involvement of miRNAs regulating the PTEN-AKT pathway in GH-producing pituitary tumor formation in the context of hyperplasia or due to germline PRKAR1A defects. MiR-26b suppression and miR-128 upregulation could have therapeutic potential in GH-producing pituitary tumor patients.

Hereditary pituitary hyperplasia with infantile gigantism

CONTEXT

We report hereditary pituitary hyperplasia.

OBJECTIVE

The objective of the study was to describe the results of the clinical and laboratory analysis of this rare instance of hereditary pituitary hyperplasia.

DESIGN

The study is a retrospective analysis of three cases from one family.

SETTING

The study was conducted at the National Institutes of Health, a tertiary referral center.

PATIENTS

A mother and both her sons had very early-onset gigantism associated with high levels of serum GH and prolactin.

INTERVENTIONS

The condition was treated by total hypophysectomy.

MAIN OUTCOME MEASURE(S)

We performed clinical, pathological, and molecular evaluations, including evaluation basal and provocative endocrine testing, neuroradiological assessment, and assessment of the pituitary tissue by microscopic evaluation, immunohistochemistry, and electron microscopy.

RESULTS

All three family members had very early onset of gigantism associated with abnormally high serum levels of GH and prolactin. Serum GHRH levels were not elevated in either of the boys. The clinical, radiographic, surgical, and histological findings indicated mammosomatotroph hyperplasia. The pituitary gland of both boys revealed diffuse mammosomatotroph hyperplasia of the entire pituitary gland without evidence of adenoma. Prolactin and GH were secreted by the same cells within the same secretory granules. Western blot and immunohistochemistry demonstrated expression of GHRH in clusters of cells distributed throughout the hyperplastic pituitary of both boys.

CONCLUSIONS

This hereditary condition seems to be a result of embryonic pituitary maldevelopment with retention and expansion of the mammosomatotrophs. The findings suggest that it is caused by paracrine or autocrine pituitary GHRH secretion during pituitary development.

Integrated genomic profiling identifies loss of chromosome 11p impacting transcriptomic activity in aggressive pituitary PRL tumors

Integrative genomics approaches associating DNA structure and transcriptomic analysis should allow the identification of cascades of events relating to tumor aggressiveness. While different genome alterations have been identified in pituitary tumors, none have ever been correlated with the aggressiveness. This study focused on one subtype of pituitary tumor, the prolactin (PRL) pituitary tumors, to identify molecular events associated with the aggressive and malignant phenotypes. We combined a comparative genomic hybridization and transcriptomic analysis of 13 PRL tumors classified as nonaggressive or aggressive. Allelic loss within the p arm region of chromosome 11 was detected in five of the aggressive tumors. Allelic loss in the 11q arm was observed in three of these five tumors, all three of which were considered as malignant based on the occurrence of metastases. Comparison of genomic and transcriptomic data showed that allelic loss impacted upon the expression of genes located in the imbalanced region. Data filtering allowed us to highlight five deregulated genes (DGKZ, CD44, TSG101, GTF2H1, HTATIP2), within the missing 11p region, potentially responsible for triggering the aggressive and malignant phenotypes of PRL tumors. Our combined genomic and transcriptomic analysis underlines the importance of chromosome allelic loss in determining the aggressiveness and malignancy of tumors.

The clinical significance of MIB-1 labeling index in pituitary adenomas

Pituitary adenomas are unique in several ways--they are rarely malignant and yet can be invasive of several compartments. Recurrences in tumors with bland histological features that have been radically excised are a reason for frustration faced by endocrinologists and neurosurgeons in treatment of pituitary adenomas. Several attempts have therefore been made to determine the growth potential of pituitary adenomas. The aim of the present study was to define the biological significance of the MIB-1 labelling index (MIB-1 LI) in pituitary adenomas. The study included 159 cases of surgically treated pituitary adenoma seen in a single institution. MIB-1 LI was not found to be related to age or gender. The mean MIB-1 LI for clinically functional adenomas was marginally higher than that for clinically non-functional adenomas. There was a significant difference in the MIB-1 LI for tumors with a maximum diameter of more than 4 cm at a MIB-1 LI of ≥2%, however this difference was not statistically significant at a higher MIB-1 LI cut off value of >3%. The mean MIB-1 LI was significantly higher in tumors causing hydrocephalus and in those with cavernous sinus invasion and not when invasion was defined as invasion by tumor in any direction. We conclude that large pituitary macroadenomas, tumors filling the third ventricle causing hydrocephalus and tumors with true cavernous sinus invasions are more likely to have a higher proliferation index. Close follow up of tumors showing these imaging features would be recommended.

PRKAR1A and the evolution of pituitary tumors

Carney complex (CNC) is an inherited tumor predisposition associated with pituitary tumors, including GH-producing pituitary adenomas and rare reports of prolactinomas. This disease is caused by mutations in PRKAR1A, which encodes the type 1A regulatory subunit of the cAMP-dependent protein kinase, PKA. Loss of PRKAR1A causes enhanced PKA signaling, which leads to pituitary tumorigenesis. Mutations in the gene have not been detected in sporadic pituitary tumors, but there is some data to suggest that non-genomic mechanisms may cause loss of protein expression. Unlike CNC patients, mice heterozygous for Prkar1a mutations do not develop pituitary tumors, although complete knockout of the gene in the Pit1 lineage of the pituitary produces GH-secreting pituitary adenomas. These data indicate that complete loss of Prkar1a/PRKAR1A is able to cause pituitary tumors in mice and men. The pattern of tumors is likely related to the signaling pathways employed in specific pituitary cell types.

Advances in the Diagnosis, Treatment, and Molecular Genetics of Pituitary Adenomas in Childhood

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Pituitary tumors in childhood: update of diagnosis, treatment and molecular genetics

Pituitary tumors are rare in childhood and adolescence, with a reported prevalence of up to one per 1 million children. Only 2-6% of surgically treated pituitary tumors occur in children. Although pituitary tumors in children are almost never malignant and hormonal secretion is rare, these tumors may result in significant morbidity. Tumors within the pituitary fossa are mainly of two types: craniopharyngiomas and adenomas. Craniopharyngiomas cause symptoms by compressing normal pituitary, causing hormonal deficiencies and producing mass effects on surrounding tissues and the brain; adenomas produce a variety of hormonal conditions such as hyperprolactinemia, Cushing disease and acromegaly or gigantism. Little is known about the genetic causes of sporadic lesions, which comprise the majority of pituitary tumors, but in children, more frequently than in adults, pituitary tumors may be a manifestation of genetic conditions such as multiple endocrine neoplasia type 1, Carney complex, familial isolated pituitary adenoma and McCune-Albright syndrome. The study of pituitary tumorigenesis in the context of these genetic syndromes has advanced our knowledge of the molecular basis of pituitary tumors and may lead to new therapeutic developments.

Clinical and molecular genetics of acromegaly: MEN1, Carney complex, McCune-Albright syndrome, familial acromegaly and genetic defects in sporadic tumors

Pituitary tumors are among the most common neoplasms in man; they account for approximately 15% of all primary intracranial lesions (Jagannathan et al., Neurosurg Focus, 19:E4, 2005). Although almost never malignant and rarely clinically expressed, pituitary tumors may cause significant morbidity in affected patients. First, given the critical location of the gland, large tumors may lead to mass effects, and, second, proliferation of hormone-secreting pituitary cells leads to endocrine syndromes. Acromegaly results from oversecretion of growth hormone (GH) by the proliferating somatotrophs. Despite the significant efforts made over the last decade, still little is known about the genetic causes of common pituitary tumors and even less is applied from this knowledge therapeutically. In this review, we present an update on the genetic syndromes associated with pituitary adenomas and discuss the related genetic defects. We next review findings on sporadic, non-genetic, pituitary tumors with an emphasis on pathways and animal models of pituitary disease. In conclusion, we attempt to present an overall, integrative approach to the human molecular genetics of both familiar and sporadic pituitary tumors.

Molecular genetics of the cAMP-dependent protein kinase pathway and of sporadic pituitary tumorigenesis

Pituitary tumors are among the most common human neoplasms. Although these common lesions rarely become clinically manifest and they are almost never malignant, they are the cause of significant morbidity in affected patients. The genetic causes of common pituitary tumors remain for the most part unknown; progress has been limited to the elucidation of the molecular etiology of four genetic syndromes predisposing to pituitary neoplasias: McCune-Albright syndrome, multiple endocrine neoplasia type 1, Carney complex and, most recently, familial acromegaly and prolactinomas and other tumors caused by mutations in the GNAS, menin, PRKAR1A, AIP, and p27 (CDKN1B) genes, respectively. Intense molecular studies of sporadic pituitary tumors from patients with negative family histories and no other neoplasms have yielded interesting findings with abnormalities in growth factor expression and cell cycle control dysregulation. To add to the difficulties in understanding pituitary tumorigenesis in man, good murine models of these neoplasms simply do not exist: pituitary tumors are common in rodents, but their histologic origin (mostly from the intermediate lobe), age of presentation (late in murine life) and clinical course make them hardly models of their human counterparts. The present report reviews the clinical and molecular genetics of the cAMP-dependent protein kinase pathway in human pituitary tumors; it also reviews briefly other pathways that have been involved in sporadic pituitary neoplasms. At the end, we attempt a unifying hypothesis for pituitary tumorigenesis, taking into account data that are also discussed elsewhere in this issue.

Pituitary pathology in patients with Carney Complex: growth-hormone producing hyperplasia or tumors and their association with other abnormalities

First described in the mid 80's, Carney Complex (CNC) is a rare, dominantly heritable disorder with features overlapping those of McCune-Albright syndrome (MAS) and other multiple endocrine neoplasia (MEN) syndromes like MEN type 1 (MEN 1). Pituitary tumors have been described in a number of patients with CNC; they present with elevated growth hormone (GH) levels and mild hyperprolactinemia. However, most patients with CNC have mild hypersomatomammotropinemia starting in adolescence; this is similar to the situation in MAS patients: in both disorders, pituitary hyperplasia appears to precede tumor development. Familial pituitary tumor syndromes such as CNC provide an important insight into the genetics and molecular pathology of pituitary and other endocrine tumors. Our understanding of these conditions is expanding rapidly due to the identification of the causative genes and the availability of murine disease models. The present report reviews the clinical findings related to pituitary tumor development among patients with CNC and provides an update on murine models of the complex.

Molecular cytogenetic analysis in the study of brain tumors: findings and applications

Classic cytogenetics has evolved from black and white to technicolor images of chromosomes as a result of advances in fluorescence in situ hybridization (FISH) techniques, and is now called molecular cytogenetics. Improvements in the quality and diversity of probes suitable for FISH, coupled with advances in computerized image analysis, now permit the genome or tissue of interest to be analyzed in detail on a glass slide. It is evident that the growing list of options for cytogenetic analysis has improved the understanding of chromosomal changes in disease initiation, progression, and response to treatment. The contributions of classic and molecular cytogenetics to the study of brain tumors have provided scientists and clinicians alike with new avenues for investigation. In this review the authors summarize the contributions of molecular cytogenetics to the study of brain tumors, encompassing the findings of classic cytogenetics, interphase- and metaphase-based FISH studies, spectral karyotyping, and metaphase- and array-based comparative genomic hybridization. In addition, this review also details the role of molecular cytogenetic techniques in other aspects of understanding the pathogenesis of brain tumors, including xenograft, cancer stem cell, and telomere length studies.