Anterior pituitary adenomas: inherited syndromes, novel genes and molecular pathways

Comprehensive review of milk fat globule membrane proteins across mammals and lactation periods in health and disease

Milk fat globule membrane (MFGM) is a three-layer membrane-like structure encasing natural milk fat globules (MFGs). MFGM holds promise as a nutritional supplement because of the numerous physiological functions of its constituent protein. This review summarizes and compares the differences in MFGM protein composition across various species, including bovines, goats, camels, mares, and donkeys, and different lactation periods, such as colostrum and mature milk, as assessed by techniques such as proteomics and mass spectrometry. We also discuss the health benefits of MFGM proteins throughout life. MFGM proteins promote intestinal development, neurodevelopment, and glucose and lipid metabolism by upregulating tight junction protein expression, brain function-related genes, and glucose and fatty acid biosynthesis processes. We focus on the mechanisms underlying these beneficial effects of MFGM proteins. MFGM proteins activate key substances in in signaling pathways, such as the phosphatidylinositol 3-kinase/protein kinase B, mitogen-activated protein kinase, and myosin light chain kinase signaling pathways. Overall, the consumption of MFGM proteins plays an essential role in conferring health benefits, some of which are important throughout the mammalian life cycle.

A bioinformatics-based approach and expression assay for identification of dysregulated genes in pituitary adenoma

Non-functioning pituitary adenomas (NFPAs) are a group of pituitary neuroendocrine tumors that are associated with morbidity. The exact pathophysiological process leading to this pathology is not known. Nerve growth factor (NGF) is a neurotropic factor that might be involved in this process. We used bioinformatics tools to analyze expression of genes in NFPA samples. Our analyses led to identification of NGF-related genes, namely ARC, ID1, and SH3GL3 - as well as one long non-coding RNA (lncRNA) called myocardial infarction associated transcript (MIAT). Then, we assessed their expression in NFPAs and their adjacent non-cancerous samples. While expression levels of SH3GL3 and MIAT were different between NFPA samples and control samples, expressions of ARC and ID1 were not meaningfully different between these two groups of specimens. SH3GL3 was over-expressed in NFPA samples compared with control samples (expression ratio (95% CI)= 8.22 (1.51-44.6), P value= 0.03). Similarly, expression of MIAT was higher in NFPAs compared with controls (expression ratio (95% CI)= 7.7 (1.7-33.6), P value= 0.009). Taken together, we validated the bioinformatics results regarding the expression of SH3GL3 and MIAT. This study provides a deeper understanding of the involvement of these genes in the pituitary tumorigenesis.

Pituitary Tumorigenesis-Implications for Management

Pituitary neuroendocrine tumors (PitNETs), the third most common intracranial tumor, are mostly benign. However, some of them may display a more aggressive behavior, invading into the surrounding structures. While they may rarely metastasize, they may resist different treatment modalities. Several major advances in molecular biology in the past few years led to the discovery of the possible mechanisms involved in pituitary tumorigenesis with a possible therapeutic implication. The mutations in the different proteins involved in the Gsa/protein kinase A/c AMP signaling pathway are well-known and are responsible for many PitNETS, such as somatotropinomas and, in the context of syndromes, as the McCune-Albright syndrome, Carney complex, familiar isolated pituitary adenoma (FIPA), and X-linked acrogigantism (XLAG). The other pathways involved are the MAPK/ERK, PI3K/Akt, Wnt, and the most recently studied HIPPO pathways. Moreover, the mutations in several other tumor suppressor genes, such as menin and CDKN1B, are responsible for the MEN1 and MEN4 syndromes and succinate dehydrogenase (SDHx) in the context of the 3PAs syndrome. Furthermore, the pituitary stem cells and miRNAs hold an essential role in pituitary tumorigenesis and may represent new molecular targets for their diagnosis and treatment. This review aims to summarize the different cell signaling pathways and genes involved in pituitary tumorigenesis in an attempt to clarify their implications for diagnosis and management.

ST8SIA6-AS1 Promotes the Epithelial-to-Mesenchymal Transition and Angiogenesis of Pituitary Adenoma

To investigate the effect of long noncoding RNA ST8SIA6-AS1 on the epithelial-to-mesenchymal transition (EMT) and angiogenesis of pituitary adenoma and its possible mechanism. The expression levels of ST8SIA6-AS1 and HOXA9 in noninvasive pituitary adenoma and invasive pituitary adenoma were detected using qRT-PCR. sh-ST8SIA6-AS1 transfection silenced the expression of ST8SIA6-AS1 in GH3 and GTI-1 cells. The effects of ST8SIA6-AS1 on the proliferation, invasion, angiogenesis, and EMT of GH3 and GTI-1 pituitary adenoma cells were detected. The migration ability of cells was detected through scratch assay. Dual luciferase analysis verified the targeting relationship between ST8SIA6-AS1 and miR-5195-3p. ST8SIA6-AS1 and HOXA9 were highly expressed in invasive pituitary adenoma. In pituitary adenomas, miR-5195-3p directly targeted HOXA9. miR-5195-3p is the target gene of ST8SIA6-AS1. ST8SIA6-AS1 knockdown inhibited the proliferation, invasion, angiogenesis, and EMT of pituitary adenoma. HOXA9 expression mediates the biological effect of ST8SIA6-AS1. ST8SIA6-AS1 targets miR-5195-3p to regulate the expression of HOXA9 and promote the EMT of pituitary adenomas.

Renal transplantation in gigantism: A case report

BACKGROUND

Gigantism, characterized by excessive growth and height is due to increased secretion of growth hormone, most commonly from a pituitary adenoma. In addition to the surgical and anesthetic complexity, the extreme stature of these patients presents a unique challenge for kidney transplantation in deciding whether to proceed with a single or dual kidney transplantation. The lack of relevant literature further adds to the dilemma.

CASE SUMMARY

A 45-year-old patient with untreated gigantism and end stage renal failure on renal replacement therapy was waitlisted for a deceased donor dual kidney transplantation due to the extreme physical stature (Height-247 cm and weight-200 kg). He was offered 2 kidneys from a 1-0-1 HLA mismatched 24-year-old DCD donor (Height-179 cm and weight-75 kg), and was planned for a bilateral retroperitoneal implantation into the recipient external iliac vessels. The immunosuppression consisted of alemtuzumab induction (50 mg) and steroid-free maintenance with tacrolimus. The donor’s right kidney was uneventfully implanted extra-peritoneally into the right external iliac vessels. On contralateral exposure, the left common and external iliac arteries were ectatic and frail. A complex vascular reconstruction was not preferred in order to preserve the arterial supply to the left lower limb, to minimise the cold ischemia time and prevent additional warm ischemic insult to the second kidney. Hence, it was decided not to proceed with dual transplantation. Amidst concerns of nephron mass insufficiency, the graft function was remarkable with a serum creatinine of 120 µmol/L within a month from transplantation and 94 µmol/L at 1-year post transplantation, and without proteinuria.

CONCLUSION

To our knowledge, this is the first case report on kidney transplantation in gigantism. Although it is believed that dual kidney transplantation is ideal, a single kidney transplantation from an appropriately selected donor can provide sufficient functioning nephron mass in patients with gigantism.

Clinical and Molecular Update on Genetic Causes of Pituitary Adenomas

Pituitary adenomas are benign tumors with variable functional characteristics that can have a significant impact on patients. The majority arise sporadically, but an inherited genetic susceptibility is increasingly being recognized. Recent advances in genetics have widened the scope of our understanding of pituitary tumorigenesis. The clinical and genetic characteristics of pituitary adenomas that develop in the setting of germline-mosaic and somatic GNAS mutations (McCune-Albright syndrome and sporadic acromegaly), germline MEN1 mutations (multiple endocrine neoplasia type 1), and germline PRKAR1A mutations (Carney complex) have been well described. Non-syndromic familial cases of isolated pituitary tumors can occur as familial isolated pituitary adenomas (FIPA); mutations/deletions of the AIP gene have been found in a minority of these. Genetic alterations in GPR101 have been identified recently as causing X-linked acro-gigantism (X-LAG) leading to very early-onset pediatric gigantism. Associations of pituitary adenomas with other tumors have been described in syndromes like multiple endocrine neoplasia type 4, pheochromocytoma-paraganglioma with pituitary adenoma association (3PAs) syndrome and some of their genetic causes have been elucidated. The genetic etiologies of a significant proportions of sporadic corticotropinomas have recently been identified with the discovery of USP8 and USP48 mutations. The elucidation of genetic and molecular pathophysiology in pituitary adenomas is a key factor for better patient management and effective follow-up.

Pituitary Adenoma in Pediatric and Adolescent Populations

Pituitary adenomas are rare in children and adolescents and although mostly benign, they can sometimes be challenging to manage due to their locally invasive nature. In this study, we examined the clinicopathologic features of 42 pituitary adenomas in patients ≤21 years of age. The youngest patient was 8 years old (median age: 18 years), and the female-to-male ratio was 1.8:1. Five patients had recurrence after resection. There was no obvious difference between the recurrent rates in the typical (11.7%) and atypical adenomas (12.5%) based on the 2004 WHO classification. However, the recurrence rate was much higher in adenomas with an elevated proliferation index of ≥3% (20.8%) or with evidence of local invasion (18.2%). Adenomas with combination of an elevated proliferation index of ≥3% and imaging evidence of local invasion had the highest recurrence rate of 25%. In summary, pituitary adenomas are more frequent in adolescents as compared with children and are more common in girls. An elevated proliferation index of ≥3% and evidence of local invasion on imaging seem to correlate with a high probability of recurrence. Furthermore, we observe rarity of α-thalassemia/mental retardation syndrome X-linked (ATRX) protein loss (surrogate to ATRX mutation) in these tumors without any connotation on prognosis.

An update on the genetics of benign pituitary adenomas in children and adolescents

Pituitary adenomas in children and adolescents are rare tumors that often result from a tumor predisposition syndrome. Several inherited causes for pituitary adenomas have been identified in the last few years, including multiple endocrine neoplasia type 1 and 4, Carney's complex, Tuberous sclerosis, DICER1 syndrome, neurofibromatosis type 1, McCune Albright syndrome, familial isolated pituitary adenoma, and pituitary adenoma association due to defects in succinate dehydrogenase genes. Recently, our group discovered X-linked acrogigantism (X-LAG), a new pediatric disorder that is caused by an Xq26.3 genomic duplication (involving the GPR101 gene). Genes that predispose to pediatric Cushing disease, including CABLES1 and USP8, were also recently identified. Genetic screening and counseling of affected or at risk individuals is a key component of their comprehensive care. In this review, we provide an up-to-date discussion on the latest pediatric genetic discoveries associated with pituitary adenomas with a focus on familial syndromes.

Plurihormonal cells of normal anterior pituitary: Facts and conclusions

Introduction

plurihormonality of pituitary adenomas is an ability of adenoma cells to produce more than one hormone. After the immunohistochemical analysis had become a routine part of the morphological study, a great number of adenomas appeared to be multihormonal in actual practice. We hypothesize that the same cells of a normal pituitary gland releases several hormones simultaneously.

Objective

To analyse a possible co-expression of hormones by the cells of the normal anterior pituitary of adult humans in autopsy material.

Materials and methods

We studied 10 pituitary glands of 4 women and 6 men with cardiovascular and oncological diseases. Double staining immunohistochemistry using 11 hormone combinations was performed in all the cases. These combinations were: prolactin/thyroid-stimulating hormone (TSH), prolactin/luteinizing hormone (LH), prolactin/follicle-stimulating hormone (FSH), prolactin/adrenocorticotropic hormone (ACTH), growth hormone (GH)/TSH, GH/LH, GH/FSH, GH/ACTH, TSH/LH, TSH/FSH, TSH/ACTH. Laser Confocal Scanning Microscopy with a mixture of primary antibodies was performed in 2 cases. These mixtures were ACTH/prolactin, FSH/prolactin, TSH/prolactin, ACTH/GH, and FSH/GH.

Results

We found that the same cells of the normal adenohypophysis can co-express prolactin with ACTH, TSH, FSH, LH; GH with ACTH, TSH, FSH, LH, and TSH with ACTH, FSH, LH. The comparison of the average co-expression coefficients of prolactin, GH and TSH with other hormones showed that the TSH co-expression coefficient was significantly the least (9,5±6,9%; 9,6±7,8%; 1,0±1,3% correspondingly).

Conclusion

Plurihormonality of normal adenohypophysis is an actually existing phenomenon. Identification of different hormones in pituitary adenomas enables to find new ways to improve both diagnostic process and targeted treatment.

Milk fat globule membrane protein promotes C2C12 cell proliferation through the PI3K/Akt signaling pathway

Milk fat globule membrane (MFGM) protein is known to have several health benefits, including an anti-sarcopenia effect; however, its mechanism is unclear. The aim of this study was to investigate the potential mechanism of action of the MFGM protein. The MFGM protein was extracted and separated into 4 fractions, and Fraction 2 (57% of total MFGM) demonstrated the greatest effect on C₂C₁₂ cell proliferation. Milk fat globule-EGF factor 8 (MFG-E8) accounted for 82.35% of the MFGM protein. The effects of whole Fraction 2 (100μg/mL, 200μg/mL and 300μg/mL) on cell proliferation and morphology were measured. Using qRT-PCR or a Western blot assay, several regulatory factors, e.g., PI3K P85α, p-pI3K p85α (Tyr 508), Akt, p-Akt (Ser 473), mTOR and p-mTOR (Ser 2448), were measured in cells incubated with 200μg/mL of Fraction 2 with or without wortmannin. The results demonstrated that Fraction 2 induced C₂C₁₂ cell proliferation in a dose-dependent manner, upregulated the mRNA expression of mTOR and p70S6K, and activated PI3K, Akt, mTOR and P70S6K phosphorylation; however, Fraction 2 inhibited FOXO3a and 4E-BP. The results demonstrate that the MFGM protein, predominantly MFG-E8, promotes cell proliferation through the PI3K/Akt/mTOR signaling pathway. This study elucidated the molecular mechanism of the MFGM protein, primarily MFG-E8, in promoting C₂C₁₂ cell proliferation via the PI3K/Akt/mTOR/P70S6K signal pathway.

Feline hypersomatotropism and acromegaly tumorigenesis: a potential role for the AIP gene

Acromegaly in humans is usually sporadic, however up to 20% of familial isolated pituitary adenomas are caused by germline sequence variants of the aryl-hydrocarbon-receptor interacting protein (AIP) gene. Feline acromegaly has similarities to human acromegalic families with AIP mutations. The aim of this study was to sequence the feline AIP gene, identify sequence variants and compare the AIP gene sequence between feline acromegalic and control cats, and in acromegalic siblings. The feline AIP gene was amplified through PCR using whole blood genomic DNA from 10 acromegalic and 10 control cats, and 3 sibling pairs affected by acromegaly. PCR products were sequenced and compared with the published predicted feline AIP gene. A single nonsynonymous SNP was identified in exon 1 (AIP:c.9T > G) of two acromegalic cats and none of the control cats, as well as both members of one sibling pair. The region of this SNP is considered essential for the interaction of the AIP protein with its receptor. This sequence variant has not previously been reported in humans. Two additional synonymous sequence variants were identified (AIP:c.481C > T and AIP:c.826C > T). This is the first molecular study to investigate a potential genetic cause of feline acromegaly and identified a nonsynonymous AIP single nucleotide polymorphism in 20% of the acromegalic cat population evaluated, as well as in one of the sibling pairs evaluated.

Genetics of gigantism and acromegaly

Gigantism and acromegaly are rare disorders that are caused by excessive GH secretion and/or high levels of its mediator, IGF-1. Gigantism occurs when excess GH or IGF-1 lead to increased linear growth, before the end of puberty and epiphyseal closure. The majority of cases arise from a benign GH-secreting pituitary adenoma, with an incidence of pituitary gigantism and acromegaly of approximately 8 and 11 per million person-years, respectively. Over the past two decades, our increasing understanding of the molecular and genetic etiologies of pituitary gigantism and acromegaly yielded several genetic causes, including multiple endocrine neoplasia type 1 and 4, McCune-Albright syndrome, Carney complex, familial isolated pituitary adenoma, pituitary adenoma association due to defects in familial succinate dehydrogenase genes, and the recently identified X-linked acrogigantism. The early diagnosis of these conditions helps guide early intervention, screening, and genetic counseling of patients and their family members. In this review, we provide a concise and up-to-date discussion on the genetics of gigantism and acromegaly.

AIP mutations in young patients with acromegaly and the Tampico Giant: the Mexican experience

Although aryl hydrocarbon receptor-interacting protein (AIP) mutations are rare in sporadic acromegaly, their prevalence among young patients is nonnegligible. The objectives of this study were to evaluate the frequency of AIP mutations in a cohort of Mexican patients with acromegaly with disease onset before the age of 30 and to search for molecular abnormalities in the AIP gene in teeth obtained from the "Tampico Giant". Peripheral blood DNA from 71 patients with acromegaly (51 females) with disease onset <30 years was analysed (median age of disease onset of 23 years) and correlated with clinical, biochemical and imaging characteristics. Sequencing was also carried out in DNA extracted from teeth of the Tampico Giant. Five patients (7 %) harboured heterozygous, germline mutations of the AIP gene. In two of them (a 9-year-old girl with gigantism and a young man with symptoms of GH excess since age 14) the c.910C>T (p.Arg304Ter), well-known truncating mutation was identified; in one of these two cases and her identical twin sister, the mutation proved to be a de novo event, since neither of their parents were found to be carriers. In the remaining three patients, new mutations were identified: a frameshift mutation (c.976_977insC, p.Gly326AfsTer), an in-frame deletion (c.872_877del, p.Val291_Leu292del) and a nonsense mutation (c.868A > T, p.Lys290Ter), which are predicted to be pathogenic based on in silico analysis. Patients with AIP mutations tended to have an earlier onset of acromegaly and harboured larger and more invasive tumours. A previously described genetic variant of unknown significance (c.869C > T, p.Ala299Val) was identified in DNA from the Tampico Giant. The prevalence of AIP mutations in young Mexican patients with acromegaly is similar to that of European cohorts. Our results support the need for genetic evaluation of patients with early onset acromegaly.

Pituitary gigantism: Causes and clinical characteristics

Acromegaly and pituitary gigantism are very rare conditions resulting from excessive secretion of growth hormone (GH), usually by a pituitary adenoma. Pituitary gigantism occurs when GH excess overlaps with the period of rapid linear growth during childhood and adolescence. Until recently, its etiology and clinical characteristics have been poorly understood. Genetic and genomic causes have been identified in recent years that explain about half of cases of pituitary gigantism. We describe these recent discoveries and focus on some important settings in which gigantism can occur, including familial isolated pituitary adenomas (FIPA) and the newly described X-linked acrogigantism (X-LAG) syndrome.

Clinical and genetic characterization of pituitary gigantism: an international collaborative study in 208 patients

Despite being a classical growth disorder, pituitary gigantism has not been studied previously in a standardized way. We performed a retrospective, multicenter, international study to characterize a large series of pituitary gigantism patients. We included 208 patients (163 males; 78.4%) with growth hormone excess and a current/previous abnormal growth velocity for age or final height >2 s.d. above country normal means. The median onset of rapid growth was 13 years and occurred significantly earlier in females than in males; pituitary adenomas were diagnosed earlier in females than males (15.8 vs 21.5 years respectively). Adenomas were ≥10 mm (i.e., macroadenomas) in 84%, of which extrasellar extension occurred in 77% and invasion in 54%. GH/IGF1 control was achieved in 39% during long-term follow-up. Final height was greater in younger onset patients, with larger tumors and higher GH levels. Later disease control was associated with a greater difference from mid-parental height (r=0.23, P=0.02). AIP mutations occurred in 29%; microduplication at Xq26.3 - X-linked acrogigantism (X-LAG) - occurred in two familial isolated pituitary adenoma kindreds and in ten sporadic patients. Tumor size was not different in X-LAG, AIP mutated and genetically negative patient groups. AIP-mutated and X-LAG patients were significantly younger at onset and diagnosis, but disease control was worse in genetically negative cases. Pituitary gigantism patients are characterized by male predominance and large tumors that are difficult to control. Treatment delay increases final height and symptom burden. AIP mutations and X-LAG explain many cases, but no genetic etiology is seen in >50% of cases.

Clinicopathological correlates of adrenal Cushing's syndrome

Endogenous Cushing's syndrome is a rare endocrine disorder that incurs significant cardiovascular morbidity and mortality, due to glucocorticoid excess. It comprises adrenal (20%) and non-adrenal (80%) aetiologies. While the majority of cases are attributed to pituitary or ectopic corticotropin (ACTH) overproduction, primary cortisol-producing adrenal cortical lesions are increasingly recognised in the pathophysiology of Cushing's syndrome. Our understanding of this disease has progressed substantially over the past decade. Recently, important mechanisms underlying the pathogenesis of adrenal hypercortisolism have been elucidated with the discovery of mutations in cyclic AMP signalling (PRKACA, PRKAR1A, GNAS, PDE11A, PDE8B), armadillo repeat containing 5 gene (ARMC5) a putative tumour suppressor gene, aberrant G-protein-coupled receptors, and intra-adrenal secretion of ACTH. Accurate subtyping of Cushing's syndrome is crucial for treatment decision-making and requires a complete integration of clinical, biochemical, imaging and pathology findings. Pathological correlates in the adrenal glands include hyperplasia, adenoma and carcinoma. While the most common presentation is diffuse adrenocortical hyperplasia secondary to excess ACTH production, this entity is usually treated with pituitary or ectopic tumour resection. Therefore, when confronted with adrenalectomy specimens in the setting of Cushing's syndrome, surgical pathologists are most commonly exposed to adrenocortical adenomas, carcinomas and primary macronodular or micronodular hyperplasia. This review provides an update on the rapidly evolving knowledge of adrenal Cushing's syndrome and discusses the clinicopathological correlations of this important disease.

Genetic mutations in sporadic pituitary adenomas--what to screen for?

Pituitary adenomas are benign intracranial neoplasms that can result in morbidity owing to local invasion and/or excessive or deficient hormone production. The prevalence of symptomatic pituitary adenomas is approximately 1:1,000 in the general population. The vast majority of these tumours occur sporadically and are not part of syndromic disorders. However, germline mutations in genes known to predispose individuals to familial pituitary adenomas are found in a few patients with sporadic pituitary adenomas. Mutations in AIP (encoding aryl-hydrocarbon receptor-interacting protein) are the most frequently observed germline mutations. The prevalence of these mutations in patients with sporadic pituitary adenomas is ∼4%, but can increase to 8-20% in young adults with macroadenomas or gigantism, and also in children. Germline mutations in MEN1 (encoding menin) result in multiple endocrine neoplasia type 1 and are found in very young patients with isolated sporadic pituitary adenomas, which highlights the importance of the chromosome 11q13 locus in pituitary tumorigenesis. In this Review, we describe the clinical features of patients with sporadic pituitary adenomas that are associated with AIP or MEN1 mutations, and discuss the molecular mechanisms that might be involved in pituitary adenoma tumorigenesis. We also discuss genetic screening of patients with sporadic pituitary adenomas and investigations of relatives of these patients who also have the same genetic mutations.

Gigantism and acromegaly due to Xq26 microduplications and GPR101 mutation

BACKGROUND

Increased secretion of growth hormone leads to gigantism in children and acromegaly in adults; the genetic causes of gigantism and acromegaly are poorly understood.

METHODS

We performed clinical and genetic studies of samples obtained from 43 patients with gigantism and then sequenced an implicated gene in samples from 248 patients with acromegaly.

RESULTS

We observed microduplication on chromosome Xq26.3 in samples from 13 patients with gigantism; of these samples, 4 were obtained from members of two unrelated kindreds, and 9 were from patients with sporadic cases. All the patients had disease onset during early childhood. Of the patients with gigantism who did not carry an Xq26.3 microduplication, none presented before the age of 5 years. Genomic characterization of the Xq26.3 region suggests that the microduplications are generated during chromosome replication and that they contain four protein-coding genes. Only one of these genes, GPR101, which encodes a G-protein-coupled receptor, was overexpressed in patients' pituitary lesions. We identified a recurrent GPR101 mutation (p.E308D) in 11 of 248 patients with acromegaly, with the mutation found mostly in tumors. When the mutation was transfected into rat GH3 cells, it led to increased release of growth hormone and proliferation of growth hormone-producing cells.

CONCLUSIONS

We describe a pediatric disorder (which we have termed X-linked acrogigantism [X-LAG]) that is caused by an Xq26.3 genomic duplication and is characterized by early-onset gigantism resulting from an excess of growth hormone. Duplication of GPR101 probably causes X-LAG. We also found a recurrent mutation in GPR101 in some adults with acromegaly. (Funded by the Eunice Kennedy Shriver National Institute of Child Health and Human Development and others.).

Paediatric pituitary adenomas: a decade of change

Pituitary adenomas, although rare in the paediatric age range and mostly benign, represent very challenging disorders for diagnosis and management. The recent identification of genetic alterations in young individuals with pituitary adenomas has broadened the scope of molecular investigations and contributed to the understanding of mechanisms of tumorigenesis. Recent identification of causative mutations of genes such as GNAS, PRKAR1A, MEN1 and AIP has introduced the concept of molecular screening of young apparently healthy family members. Population-based studies have reported a significantly higher number of affected subjects and genetic variations than expected. Radiological techniques have advanced, yet many microadenomas remain undetectable on scanning. However, experience with transsphenoidal and endoscopic pituitary surgery has led to higher rates of cure. Prolactinomas, corticotroph and somatotroph adenomas remain the most prevalent, with each diagnosis presenting its own challenges. As paediatric pituitary adenomas occur very infrequently within the paediatric age range, paediatric endocrine units cannot provide expert management in isolation. Consequently, close co-operation with adult endocrinology colleagues with experience of pituitary disease is strongly recommended.

Low rate of germline AIP mutations in patients with apparently sporadic pituitary adenomas before the age of 40: a single-centre adult cohort

AIM

To study the prevalence of germline mutations of the aryl-hydrocarbon receptor interacting protein (AIP) gene in a large cohort of patients seen in the Oxford Centre for Diabetes Endocrinology and Metabolism (OCDEM), UK, with apparently sporadic pituitary adenomas, who were either diagnosed or had relevant clinical manifestations by the age of 40 years.

PATIENTS

We prospectively investigated all patients who were seen at Oxford University Hospital, OCDEM, and a tertiary referral centre, between 2012 and 2013, and presented with pituitary tumours under the age of 40 years and with no family history: a total of 127 patients were enrolled in the study.

METHODS

Leukocyte-origin genomic DNA underwent sequence analysis of exons 1-6 and the flanking intronic regions of the AIP gene (NM_003977.2), with dosage analysis by multiplex ligation-dependent probe amplification.

RESULTS

AIP variants were detected in 3% of the 127 patients, comprising four of 48 patients with acromegaly (8%), 0 of 43 with prolactinomas, 0 of the 20 patients with non-functioning adenomas, 0 of 15 with corticotroph adenomas and 0 of one with a thyrotroph adenomas. Definite pathogenetic mutations were seen in 2/4 variants, comprising 4.2% of patients with acromegaly.

CONCLUSIONS

This prospective cohort study suggests a relatively low prevalence of AIP gene mutations in young patients with apparently sporadic pituitary adenomas presenting to a tertiary pituitary UK centre. Those with somatotroph macroadenomas have a higher rate of AIP mutation. These findings should inform discussion of genetic testing guidelines.

Improving differential diagnosis of pituitary adenomas

Pituitary adenomas are common tumors arising in adenohypophysial cells or their precursors. For improving control of the disease an early diagnosis is important. Initially considered sporadic tumors, some of them are associated with familial syndromes and their recognition and classification is also required. Morphologically, pituitary adenomas represent a heterogeneous group of tumors with several subtypes and different clinical behavior thus a precise pathological diagnosis is crucial. The simple diagnosis of pituitary adenoma is not satisfactory and the correct classification of histological subtypes may predict aggressiveness in the majority of cases. Although considered not malignant, some of them are clinically aggressive and their recognition remains a challenge. In this paper we present the recent advances in the event of improving early recognition and differential diagnosis of pituitary tumors.

Carney complex and McCune Albright syndrome: an overview of clinical manifestations and human molecular genetics

Endocrine neoplasia syndromes feature a wide spectrum of benign and malignant tumors of endocrine and non-endocrine organs associated with other clinical manifestations. This study outlines the main clinical features, genetic basis, and molecular mechanisms behind two multiple endocrine neoplasia syndromes that share quite a bit of similarities, but one can be inherited whereas the other is always sporadic, Carney complex (CNC) and McCune-Albright (MAS), respectively. Spotty skin pigmentation, cardiac and other myxomas, and different types of endocrine tumors and other characterize Carney complex, which is caused largely by inactivating Protein kinase A, regulatory subunit, type I, Alpha (PRKAR1A) gene mutations. The main features of McCune-Albright are fibrous dysplasia of bone (FD), café-au-lait macules and precocious puberty; the disease is caused by activating mutations in the Guanine Nucleotide-binding protein, Alpha-stimulating activity polypeptide (GNAS) gene which are always somatic. We review the clinical manifestations of the two syndromes and provide an update on their molecular genetics.

Familial isolated pituitary adenoma caused by a Aip gene mutation not described before in a family context

The cause of familial isolated pituitary adenomas (FIPA) remains unknown in a high percentage of cases, but the AIP gene plays an important role in the etiology. The aim of the study is to describe a family with FIPA syndrome and the results of genomic studies. A 16-year-old man had a giant prolactinoma resistant tomedical treatment with delayed growth and pubertal development. His mother had been previously diagnosed with a nonfunctioning pituitary macroadenoma. Transsphenoidal endoscopic resection was performed and a genetic study revealed a heterozygous mutation in exon 6: 974G>A (p.Arg325Gln). Because the AIP gene is a tumor suppressor gene, we searched for loss of heterozygosity within the AIP gene by amplifying exon 6 from tumor tissue of the patient. In the electropherogram, only the A allele was amplified (hemizygous state), indicating loss of the normal allele. We report a Spanish family with FIPA in whom a mutation in the AIP gene previously unreported in a familiar context was identified.

Familial isolated pituitary adenomas (FIPA) and the pituitary adenoma predisposition due to mutations in the aryl hydrocarbon receptor interacting protein (AIP) gene

Pituitary adenomas are one of the most frequent intracranial tumors and occur with a prevalence of approximately 1:1000 in the developed world. Pituitary adenomas have a serious disease burden, and their management involves neurosurgery, biological therapies, and radiotherapy. Early diagnosis of pituitary tumors while they are smaller may help increase cure rates. Few genetic predictors of pituitary adenoma development exist. Recent years have seen two separate, complimentary advances in inherited pituitary tumor research. The clinical condition of familial isolated pituitary adenomas (FIPA) has been described, which encompasses the familial occurrence of isolated pituitary adenomas outside of the setting of syndromic conditions like multiple endocrine neoplasia type 1 and Carney complex. FIPA families comprise approximately 2% of pituitary adenomas and represent a clinical entity with homogeneous or heterogeneous pituitary adenoma types occurring within the same kindred. The aryl hydrocarbon receptor interacting protein (AIP) gene has been identified as causing a pituitary adenoma predisposition of variable penetrance that accounts for 20% of FIPA families. Germline AIP mutations have been shown to associate with the occurrence of large pituitary adenomas that occur at a young age, predominantly in children/adolescents and young adults. AIP mutations are usually associated with somatotropinomas, but prolactinomas, nonfunctioning pituitary adenomas, Cushing disease, and other infrequent clinical adenoma types can also occur. Gigantism is a particular feature of AIP mutations and occurs in more than one third of affected somatotropinoma patients. Study of pituitary adenoma patients with AIP mutations has demonstrated that these cases raise clinical challenges to successful treatment. Extensive research on the biology of AIP and new advances in mouse Aip knockout models demonstrate multiple pathways by which AIP may contribute to tumorigenesis. This review assesses the current clinical and therapeutic characteristics of more than 200 FIPA families and addresses research findings among AIP mutation-bearing patients in different populations with pituitary adenomas.

Familial isolated pituitary adenomas: an emerging clinical entity

Familial pituitary tumors are increasingly recognized. While some of these cases are related to wellknown syndromic conditions such as multiple endocrine neoplasia type 1 (MEN1) or Carney complex, others belong to the familial isolated pituitary adenoma (FIPA) patient group. The discovery of heterozygous, loss-of-function germline mutations in the gene encoding the aryl hydrocarbon receptor interacting protein (AIP) in 2006 has subsequently enabled the identification of a mutation in this gene in 20% of FIPA families and 20% of childhood-onset simplex soma- totroph adenomas. The exact mechanism by which the lack of AIP leads to pituitary adenomas is not clear. AIP mutations cause a low penetrance autosomal dominant disease with often a distinct phenotype characterized by young-onset, aggressive, large GH, mixed GH and PRL or PRL-secreting adenomas. This review aims to summarize currently available clinical data on AIP mutation-positive and negative FIPA patients.

Somatic complex I disruptive mitochondrial DNA mutations are modifiers of tumorigenesis that correlate with low genomic instability in pituitary adenomas

Mitochondrial DNA (mtDNA) mutations leading to the disruption of respiratory complex I (CI) have been shown to exhibit anti-tumorigenic effects, at variance with those impairing only the function but not the assembly of the complex, which appear to contribute positively to cancer development. Owing to the challenges in the analysis of the multi-copy mitochondrial genome, it is yet to be determined whether tumour-associated mtDNA lesions occur as somatic modifying factors or as germ-line predisposing elements. Here we investigated the whole mitochondrial genome sequence of 20 pituitary adenomas with oncocytic phenotype and identified pathogenic and/or novel mtDNA mutations in 60% of the cases. Using highly sensitive techniques, namely fluorescent PCR and allele-specific locked nucleic acid quantitative PCR, we identified the most likely somatic nature of these mutations in our sample set, since none of the mutations was detected in the corresponding blood tissue of the patients analysed. Furthermore, we have subjected a series of 48 pituitary adenomas to a high-resolution array comparative genomic hybridization analysis, which revealed that CI disruptive mutations, and the oncocytic phenotype, significantly correlate with low number of chromosomal aberrations in the nuclear genome. We conclude that CI disruptive mutations in pituitary adenomas are somatic modifiers of tumorigenesis most likely contributing not only to the development of oncocytic change, but also to a less aggressive tumour phenotype, as indicated by a stable karyotype.

Familial pituitary adenomas - who should be tested for AIP mutations?

Familial Isolated Pituitary Adenomas (FIPA), an autosomal dominant disease with low penetrance is being increasingly recognized. FIPA families can be divided into two distinct groups based on genetic and phenotypic features. Patients with mutations in the aryl hydrocarbon receptor-interacting protein (AIP) gene are characterized by young-onset somatotroph or lactotroph macroadenomas, while in the other, larger group of FIPA patients with typically adult-onset disease and more varied adenoma types, no causative gene(s) has been identified. Young-onset macroadenoma patients can also be identified with germline AIP mutation without an apparent family history. Further data and longer follow-up are necessary to establish formal guidelines, but the current data suggest genetic screening of the AIP gene in patients with a pituitary adenoma and no other associated features who have (i) a family history of pituitary adenoma, (ii) childhood-onset pituitary adenoma or (iii) a pituitary somatotroph or lactotroph macroadenoma diagnosed before the age of 30 years.

Pituitary adenoma pathogenesis: an update

PURPOSE OF REVIEW

To describe the recent efforts to understand the molecular and genetic mechanisms involved in the tumorigenesis of pituitary adenomas.

RECENT FINDINGS

There is rapidly accumulating evidence for the roles of molecular abnormalities in pituitary adenoma tumorigenesis, including dysregulation of the cell cycle, signal transduction pathways, oncogenes and tumor suppressor genes. MicroRNAs have been identified as important participants in gene regulation and may have a role in therapy. Stem cells have also provided novel concepts for tumorigenesis and potentially treatment.

SUMMARY

Pituitary adenomas are relatively common neoplasms, whose pathogenesis is still poorly understood. Although considered by many as benign monoclonal proliferations, their clinical spectrum is diverse including hormone hypersecretion, and various degrees of invasiveness, suggesting multiple steps and mechanisms. This review summarizes recent development in the molecular tumorigenesis of pituitary adenomas emphasizing the dysregulation of the cell cycle components, tumor suppressor genes, oncogenes, stem cells and microRNAs.

Lack of mutations in the gene coding for the hGR (NR3C1) in a pediatric patient with ACTH-secreting pituitary adenoma, absence of stigmata of Cushing's syndrome and unusual histologic features

BACKGROUND

Rare cases of human glucocorticoid receptor (hGRalpha) (NR3C1) gene mutations have been described in the gemline or somatic state in Cushing's disease (CD).

AIM

We describe a pediatric patient with CD with clinical evidence of partial glucocorticoid resistance (GR) due to the relative absence of stigmata of Cushing's syndrome (CS).

CASE DESCRIPTION

A 14-year-old boy with slow growth and hypertension, but no other signs of CS was admitted for CD evaluation. Urinary free cortisol levels (UFC) were consistently 2-3-fold the upper normal range. Pituitary magnetic resonance imaging (MRI) revealed a 3x4 mm hypoenhancing lesion in the right side of the pituitary gland anteriorly (microadenoma). A graded dexamethasone suppression test indicated that the patient had partial GR. Histology confirmed an adrenocorticotrophin (ACTH)-producing pituitary adenoma. We hypothesized that a NR3C1 mutation was present. Sequencing of the entire coding region of the gene produced normal results in both peripheral and tumor DNA.

CONCLUSION

We present the case of a pediatric patient with an ACTH-producing tumor but little evidence of CS. No mutations in the coding sequence of NR3C1 were detected. We conclude that low level somatic mosaicism for NR3C1 mutations or a mutation in another molecule participating in hGRalpha-signaling may account for this case.