Hydrocarbon Receptor Interacting Protein Gene Research Articles

Diagnosis and management of pituitary adenomas in children and adolescents.

Pituitary adenomas (PAs)-also now called pituitary neuroendocrine tumours or Pit-NETS-are rare in children and adolescents and exceptional below the age of 10. Most evidence-based high-quality data are derived from larger studies in adult patients. We will review recent knowledge on the epidemiology, clinical features, diagnosis, and treatment modalities of the different types of pituitary adenomas diagnosed in children and adolescents, emphasizing the many reasons why these cases should be discussed within pituitary-specific multidisciplinary teams with experts from both paediatric and adult practice. Paediatric PA presents multiple peculiarities that may challenge their adequate management. They are overall proportionally larger and more aggressive than in adults, with potential mass effects including hypopituitarism. Hormonal hypersecretion is frequent, resulting in clinical syndromes affecting normal growth and pubertal development. Prolactinomas represent the most frequent subtype of PA found during childhood, followed by adrenocorticotropin (ACTH) and growth hormone (GH)-secreting adenomas, while clinically non-functioning adenomas are exceptionally diagnosed before the age of 16. The occurrence of a pituitary tumour in a young individual should also prompt genetic testing in each case, searching for either germline mutations in one of the known genes that may drive inherited/familial PA (such as the multiple endocrine neoplasia type 1 or MEN1 gene, or the aryl hydrocarbon receptor interacting protein or AIP gene), or for a mosaic activating mutation of GNAS as found in the McCune-Albright syndrome.

Germline AIP variants in sporadic young acromegaly and pituitary gigantism: clinical and genetic insights from a Han Chinese cohort.

Variants in the Aryl hydrocarbon receptor-interacting protein (AIP) gene have been identified in sporadic acromegaly and pituitary gigantism, especially in young patients, with a predisposition to aggressive clinical phenotype and poor treatment efficacy. The clinical characteristics of patients with sporadic acromegaly and pituitary gigantism as well as AIP variants in Han Chinese have been rarely reported. We aimed to identify AIP gene variants and analyze the clinical characteristics of patients with sporadic acromegaly and pituitary gigantism in Han Chinese. The study included 181 sporadic acromegaly (N = 163) and pituitary gigantism (N = 18) patients with an onset age of no more than 45 years old, who were diagnosed, treated, and followed up in Huashan Hospital. All 6 exons and their flanking regions of the AIP gene were analyzed with Sanger sequencing or NGS. The clinical characteristics were compared between groups with and without AIP variants. Germline AIP variants were found in 15/181 (8.29%) cases. In patients with an onset age ≤30 years old, AIP variants were identified in 12/133 (9.02%). Overall, 13 variants were detected. The pathogenic (P) variants p.R304X and p.R81X were identified in four cases, with two instances of each variant. Six exon variants (p.C254R, p.K103fs, p.Q228fs, p.Y38X, p.Q213*, and p.1115 fs) have not been reported before, which were likely pathogenic (LP). Patients with P/LP variants had younger onset ages, a higher prevalence of pituitary gigantism, larger tumor volumes, and a higher percentage of Ki-67-positive cells in tumors. In addition, the group with P/LP variants showed a less significant reduction of GH levels in an acute octreotide suppression test (OST) [17.7% (0, 65.0%) vs. 80.5% (63.9%, 90.2%), P = 0.001], and a trend of less GH decrease after the 3-month treatment with long-acting somatostatin analogs (SSAs). Germline AIP variants existed in sporadic Chinese Han acromegaly and pituitary gigantism patients and were more likely to be detected in young patients. AIP variants were associated with more aggressive tumor phenotypes and less response to SSA treatment.

THU079 Danio Rerio (Zebrafish): A New Model Of AIP Loss Of Function

Abstract Disclosure: X. Wang: None. A. Leggieri: None. S. Anagianni: None. C.H. Brennan: None. M. Korbonits: None. Background: Mutations in the aryl hydrocarbon receptor-interacting protein (AIP) gene account for 10% of cases with familial isolated pituitary adenoma (FIPA). The main features of patients carrying heterozygous AIP mutations include young-onset, large and invasive growth hormone and/or prolactin-secreting pituitary tumours, although a milder spectrum of presentation has been also described. In several animal models (mouse, fruit fly, round worm), homozygous deletion of AIP results in embryonic mortality. In mice abnormal cardiac development has been observed. Objective: The aim of this study was to generate a zebrafish loss-of-function model to explore the cellular biological processes affected by heterozygous or homozygous aip mutations. Methods: Zebrafish homologue of human AIP was identified by EMBOSS Needle program. We used CRISPR/Cas9 to generate a line of fish carrying loss-of-function mutations targeting zebrafish aip exon 2. aip RNA expression was examined using in situ hybridisation. The growth rate and cardiac function were assessed using a stereo microscope with an integrated camera. The videos and pictures were analysed in ImageJ. Antisense in situ hybridisation with probes to growth hormone 1 (gh1), prolactin (prl) and proopiomelanocortin a (pomca) was used to assess pituitary phenotypes. Results: Zebrafish aip shows 78.8% of homology to human AIP. aip mRNA is expressed throughout the developing zebrafish embryo until 28 hours post fertilisation (hpf) stage when it becomes more strongly expressed in the head. We generated a 29 bp deletion in exon 2 of the zebrafish aip gene. These mutant animals showed reduced aip expression. No significant gross morphology differences were observed at 3 to 7 days post fertilisation (dpf) between wildtype (WT) and heterozygote (Het) animals. At 5dpf, WTs showed an increased heart rate than Hets (P=0.033). Conclusion: We have generated an aip loss of function zebrafish line that provides an ideal opportunity to analyse the role of aip in development. Presentation: Thursday, June 15, 2023

Studying the genotype of Aryl Hydrocarbon Receptor-Interacting Protein (AIP) Gene (rs641081C>A) in ‎Iraqi Samples with Acromegaly Pituitary Adenoma

Pituitary adenomas are the anterior pituitary tumors. Patients with an Aryl Hydrocarbon Receptor-Interacting Protein (AIP) mutation (AIP- mut) tend to have more aggressive tumors occurring at a younger age. Single nucleotide polymorphisms (SNPs) in many studies have been related to metabolic comorbidities in the general population. Study aims investigated the role of AIP gene SNPs with susceptibility to acromegaly pituitary- adenoma, with levels of LH, FSH, TSH, Testosterone, IGF1,GH, FT4 , Prolactin hormones and blood sugar levels. The study ‎was conducted on a group of acromegaly patients, including 50 patients) both Genders( with ‎hyperplasia of the ends, and apparently healthy control group. Genotyping of AIP gene SNP (rs641081C >A‎) was indicated significant differences in frequency percentage between the study groups. The frequency of heterozygous CA genotype was significantly (p<0.01) higher in the patients' group when compared with control. The Means of IGF1, GH, prolactin, testosterone, and FBS were significantly ‎higher in patients at first treatment than that in control.‎ While,‎ the means of IGF1, GH, prolactin, and testosterone increased significantly in patients at last treatment than control. Patients mean level of TSH decreased significantly at last ‎treatment. No significant differences (P ≥ 0.05) were detected between study ‎groups in all other values.‎ The Means of IGF1, GH, and prolactin at first and last treatment were significantly decreased, while LH ‎was significantly increased at last treatment. In ‎patients with heterozygous mutant and wild genotype, means of IGF1, GH, and ‎prolactin decreased significantly at last treatment compared ‎to first treatment. ‎In this study heterozygous rs641081C>A showed a risk factor for susceptibility of acromegaly. Also, serum IGF1, GH, prolactin, were affected by the SNP of AIP gene within carriers of genotypes of rs641081C>A. IGF1, prolactin and GH ‎decreased significantly at last treatment compared to first treatment.

Prolactinoma in Two Brothers - Unidentified Genetic Cause Versus Co-Incidence?

Background: Most prolactinomas occur sporadically. Familial prolactinomas are uncommon. Clinical Case(s): A 35 YO male with no significant past medical history presented to endocrine clinic with c/o fatigue, decreased libido, and erectile dysfunction. Labs showed low total testosterone of 177 ng/dl (normal range 250-1100 ng/dl), low free testosterone of 19.9 pg/ml (normal range 46-224), low LH 1.1 (normal range 1.5-9.3 mIU/ml) with elevated prolactin of 47 ng/ml (normal range 2-18). MRI pituitary showed a 4.2x4x6 mm pituitary microadenoma. Physical exam was unremarkable except for obese body habitus. No known family history of MEN syndromes or parathyroid /calcium disorders. Dopamine agonist therapy resulted in significant improvement in testosterone levels, fatigue, and libido. One year after patient’s diagnosis his 32 YO younger brother was evaluated for c/o fatigue, inability to lose weight, left breast enlargement, galactorrhea, and decreased libido. Work up showed markedly elevated prolactin levels of 2405 ng/ml (normal range 4-15), decreased total testosterone of 70 ng/dl (normal range 249-836), low free testosterone of 4.8 pg/ml (normal range 8.7 to 25.1), FSH <0.1 mIU/ml (normal range 1.4-15.4), LH < 0.1 mIU/ml (normal range 1.7-8.6). MRI Pituitary showed a 25x28x20 mm pituitary macroadenoma invading the right cavernous sinus, encasing the right internal carotid artery, and abutting the optic chiasma. Our patient had genetic testing done for sequencing and deletion/duplication analysis of MEN1 and AIP (Aryl hydrocarbon receptor interacting protein) genes—two well identified causes of familial pituitary adenomas—and tested negative for both. His brother was treated with dopamine agonists with marked improvement in Prolactin to undetectable levels within a few weeks. His energy levels, headaches, and sexual function improved and galactorrhea resolved. However, testosterone levels remained below normal range even after 11 months, despite normal prolactin levels. Discussion: Prolactinomas are the most common functional pituitary adenomas, majority of them sporadic. Familial pituitary adenomas in non-syndromic form are rare. Familial isolated pituitary adenoma (FIPA) and Multiple endocrine neoplasia type 1(MEN 1) are two main causes of familial pituitary adenomas. In FIPA, pituitary adenomas occur as a result of mutations or deletions in aryl hydrocarbon receptor interacting protein gene (AIP). Identifying these mutations is important as pituitary adenomas in FIPA tend to be more aggressive, present at a younger age and are resistant to treatment. Our patient tested negative for both MEN 1 and AIP gene mutations. Whether our patient has an unidentified genetic cause or whether it was a coincidence that two brothers have prolactinomas is unclear.

Isolated Macroprolactinomas in Four Young Adult Males Harboring a Variant of the Aryl Hydrocarbon Interacting Protein (AIP) Gene: Isn’t It Too Much of a Coincidence?

Background: Germline mutations in the Aryl hydrocarbon receptor-Interacting Protein (AIP) gene are associated with pituitary adenomas in young patients usually in the setting of Familial Isolated Pituitary Adenomas (FIPA). The majority of these adenomas are somatotropinomas followed by prolactinomas, and rarely non-secreting adenomas. AIP-mutation-related prolactinomas predominantly affect men, as opposed to sporadic prolactinomas, that typically affect women. Clinical Case: We previously described an AIP gene mutation in two patients affected by prolactinomas. During the past years, we continued our study and have identified two more male patients with macroprolactinomas originally from the same small village and harboring the same AIP gene mutation. These male patients aged 19 to 44 years at the time of diagnosis. Two of them had neurological manifestations as the first clinical manifestation of the disease, one was studied because of hypogonadism and two patients had visual field defects. All of them had prolactin levels above 1000 ng/dl (mean 2946.5±948.7 ng/dl, reference range 10-21). In the imaging exams (CT/MRI) they presented pituitary adenomas larger than 20 mm (macroprolactinomas) and in two of the cases, the adenomas were even larger than 40 mm (giant prolactinomas). In order to exclude mutations most often associated with prolactinomas, DNA samples were obtained and analyzed by Next Generation Sequencing (NGS) using TruSightCancer Gene Set (Illumina) methodology. Investigation of significant deletions and/or duplications was performed using the MLPA (Multiplex ligation-dependent probe amplification) technique. None of the patients were positive for mutations of Multiple Endocrine Neoplasia type 1 (MEN1) gene. A variant of the AIP gene c.47G>A, expecting to lead to a substitution of arginine by histidine at position 16 (p.Arg16His) of the AIP was found in these four patients, including a father and his son. Seven asymptomatic carriers were identified among their first-degree relatives. In silico analysis and the information available in the literature, as well as in databases is not in agreement with the pathogenicity of this variant of the AIP gene. However, our findings point to a founder effect transmitted as a dominant trait with incomplete penetrance (4 out of 11 patients, 36%). Conclusion: The variant of the AIP gene identified in our patients behaved as a pathogenic mutation and was only associated with prolactinomas, including two giant prolactinomas.

Pituitary Disease in AIP Mutation-Positive Familial Isolated Pituitary Adenoma (FIPA): A Kindred-Based Overview.

Clinically-relevant pituitary adenomas occur in about 1:1000 of the general population, but only about 5% occur in a known genetic or familial setting. Familial isolated pituitary adenomas (FIPA) are one of the most important inherited settings for pituitary adenomas and the most frequent genetic cause is a germline mutation in the aryl hydrocarbon receptor-interacting protein (AIP) gene. AIP mutations lead to young-onset macroadenomas that are difficult to treat. Most are growth hormone secreting tumors, but all other secretory types can exist and the clinical profile of affected patients is variable. We present an overview of the current understanding of AIP mutation-related pituitary disease and illustrate various key clinical factors using examples from one of the largest AIP mutation-positive FIPA families identified to date, in which six mutation-affected members with pituitary disease have been diagnosed. We highlight various clinically significant features of FIPA and AIP mutations, including issues related to patients with acromegaly, prolactinoma, apoplexy and non-functioning pituitary adenomas. The challenges faced by these AIP mutation-positive patients due to their disease and the long-term outcomes in older patients are discussed. Similarly, the pitfalls encountered due to incomplete penetrance of pituitary adenomas in AIP-mutated kindreds are discussed.

Phenotypic and genotypic features of a large kindred with a germline AIP variant.

Acromegaly is usually a sporadic disease, but familial cases occur. Mutations in the aryl hydrocarbon receptor-interacting protein (AIP) gene are associated with familial pituitary adenoma predisposition. However, the pathogenicity of some AIP variants remains unclear and additional unknown genes may be involved. To explore the phenotype and genotype of a large kindred carrying the p.R304Q AIP variant. The family comprised 52 family members at risk of carrying the p.R304Q AIP variant including a case with gigantism and one with acromegaly and several family members with acromegalic features. Nine family members (three trios) underwent exome sequencing to identify putative pathogenic variants. We identified 31 p.R304Q carriers, and based on two cases with somatotropinomas, the disease penetrance was 6%. We observed physical signs of acromegaly in several family members, which were independent of AIP status. Serum insulin-like growth factor-I (IGF-I) levels in all family members were above the mean for age and sex (IGF-I SDS: +0.6 [CI95% +0.4-0.9], P<.01). Exome analysis identified two candidate genes: PDE11A, known to be associated with the development of adrenal tumours, and ALG14. Ten asymptomatic p.R304Q family members (age >50years) were screened for the PDE11A and ALG14 variant; both variants were present in five of ten persons. This large family adds new information on the p.R304Q AIP variant, and data suggest two new candidate genes could be associated with growth hormone excess.

Significant Benefits of AIP Testing and Clinical Screening in Familial Isolated and Young-onset Pituitary Tumors.

ContextGermline mutations in the aryl hydrocarbon receptor-interacting protein (AIP) gene are responsible for a subset of familial isolated pituitary adenoma (FIPA) cases and sporadic pituitary neuroendocrine tumors (PitNETs).ObjectiveTo compare prospectively diagnosed AIP mutation-positive (AIPmut) PitNET patients with clinically presenting patients and to compare the clinical characteristics of AIPmut and AIPneg PitNET patients.Design12-year prospective, observational study.Participants & SettingWe studied probands and family members of FIPA kindreds and sporadic patients with disease onset ≤18 years or macroadenomas with onset ≤30 years (n = 1477). This was a collaborative study conducted at referral centers for pituitary diseases.Interventions & Outcome AIP testing and clinical screening for pituitary disease. Comparison of characteristics of prospectively diagnosed (n = 22) vs clinically presenting AIPmut PitNET patients (n = 145), and AIPmut (n = 167) vs AIPneg PitNET patients (n = 1310).ResultsProspectively diagnosed AIPmut PitNET patients had smaller lesions with less suprasellar extension or cavernous sinus invasion and required fewer treatments with fewer operations and no radiotherapy compared with clinically presenting cases; there were fewer cases with active disease and hypopituitarism at last follow-up. When comparing AIPmut and AIPneg cases, AIPmut patients were more often males, younger, more often had GH excess, pituitary apoplexy, suprasellar extension, and more patients required multimodal therapy, including radiotherapy. AIPmut patients (n = 136) with GH excess were taller than AIPneg counterparts (n = 650).ConclusionsProspectively diagnosed AIPmut patients show better outcomes than clinically presenting cases, demonstrating the benefits of genetic and clinical screening. AIP-related pituitary disease has a wide spectrum ranging from aggressively growing lesions to stable or indolent disease course.

Somatic and germline mutations in the pathogenesis of pituitary adenomas.

Pituitary adenomas are frequently occurring neoplasms that produce clinically significant disease in 1:1000 of the general population. The pathogenesis of pituitary tumors is a matter of interest as it could help to improve diagnosis and treatment. Until recently, however, disruptions in relatively few genes were known to predispose to pituitary tumor formation. In the last decade, several more genes and pathways have been described. Germline pathogenic variants in the aryl hydrocarbon receptor-interacting protein (AIP) gene were found in familial or sporadic pituitary adenomas, usually with an aggressive clinical course. Cyclin-dependent kinase inhibitor 1B (CDKN1B) pathogenic variants lead to multiple endocrine neoplasia type 4 (MEN4) syndrome, in which pituitary adenomas can occur. Xq26.3 duplications involving the gene GPR101 cause X-linked acrogigantism. The pheochomocytoma and/or paraganglioma with pituitary adenoma association (3PAs) syndrome suggests that pathogenic variants in the genes of the succinate dehydrogenase complex or MYC-associated factor X (MAX) might be involved in pituitary tumorigenesis. New recurrent somatic alterations were also discovered in pituitary adenomas, such as, ubiquitin-specific protease 8 (USP8) and USP48 pathogenic variants in corticotropinomas. The aim of the present review is to provide an overview of the genetic pathophysiology of pituitary adenomas and their clinical relevance.

Development and validation of a targeted gene sequencing panel for application to disparate cancers

Next generation sequencing has revolutionised genomic studies of cancer, having facilitated the development of precision oncology treatments based on a tumour’s molecular profile. We aimed to develop a targeted gene sequencing panel for application to disparate cancer types with particular focus on tumours of the head and neck, plus test for utility in liquid biopsy. The final panel designed through Roche/Nimblegen combined 451 cancer-associated genes (2.01 Mb target region). 136 patient DNA samples were collected for performance and application testing. Panel sensitivity and precision were measured using well-characterised DNA controls (n = 47), and specificity by Sanger sequencing of the Aryl Hydrocarbon Receptor Interacting Protein (AIP) gene in 89 patients. Assessment of liquid biopsy application employed a pool of synthetic circulating tumour DNA (ctDNA). Library preparation and sequencing were conducted on Illumina-based platforms prior to analysis with our accredited (ISO15189) bioinformatics pipeline. We achieved a mean coverage of 395x, with sensitivity and specificity of >99% and precision of >97%. Liquid biopsy revealed detection to 1.25% variant allele frequency. Application to head and neck tumours/cancers resulted in detection of mutations aligned to published databases. In conclusion, we have developed an analytically-validated panel for application to cancers of disparate types with utility in liquid biopsy.

Pituitary gigantism: a case series from Hospital de San José (Bogotá, Colombia).

Gigantism is a rare pediatric disease characterized by increased production of growth hormone (GH) before epiphyseal closure, that manifests clinically as tall stature, musculoskeletal abnormalities, and multiple comorbidities. Case series of 6 male patients with gigantism evaluated at the Endocrinology Service of Hospital de San José (Bogotá, Colombia) between 2010 and 2016. All patients had macroadenomas and their mean final height was 2.01 m. The mean age at diagnosis was 16 years, and the most common symptoms were headache (66%) and hyperhidrosis (66%). All patients had acral changes, and one had visual impairment secondary to compression of the optic chiasm. All patients underwent surgery, and 5 (83%) required additional therapy for biochemical control, including radiotherapy (n = 4, 66%), somatostatin analogues (n = 5, 83%), cabergoline (n = 3, 50%), and pegvisomant (n = 2, 33%). Three patients (50%) achieved complete biochemical control, while 2 patients showed IGF-1 normalization with pegvisomant. Two patients were genetically related and presented a mutation in the aryl hydrocarbon receptor-interacting protein (AIP) gene (pathogenic variant, c.504G>A in exon 4, p.Trp168*), fulfilling the diagnostic criteria of familial isolated pituitary adenoma. This is the largest case series of patients with gigantism described to date in Colombia. Transsphenoidal surgery was the first-choice procedure, but additional pharmacological therapy was usually required. Mutations in the AIP gene should be considered in familial cases of GH-producing adenomas.

SAT-462 AIP Mutation-Positive Patients with Somatotropinomas End up Taller and Requiring Radiotherapy More Often Compared to AIP Mutation-Negative Patients: Data from 784 Familial and Young-Onset Cases

Introduction: Germline mutations in the aryl hydrocarbon receptor-interacting protein gene (AIP) are responsible for up to 50% of familial isolated pituitary adenoma (FIPA) kindreds affected only with somatotropinomas. AIP mutation-positive (AIPmut) somatotropinomas present earlier, more aggressively and are often more resistant to therapy. We aimed to further characterise AIPmut somatotropinomas in terms of clinical features and outcomes. Methods: We studied AIPmut somatotropinomas which presented clinically; prospectively-diagnosed AIPmut somatotropinomas (i.e. somatotropinomas diagnosed following genetic and clinical screening) were excluded from the analysis. Indications for AIP genetic testing were: i) FIPA patients, ii) sporadic pituitary GH-secreting macroadenomas with disease onset <30y, or iii) GH-secreting microadenomas with age of onset <18y. Results: Out of 784 patients with somatotropinomas included in our study, 139 had an AIP mutation (17.7%). In comparison to AIP mutation-negative somatotropinomas (AIPneg), patients with AIPmut somatotropinomas had a younger age at first symptoms (18.9±9.0 vs 26.1±11.7y; p<0.001) and at diagnosis (24.1±10.5 vs 30.1±12.4y; p<0.001), higher rates of pituitary apoplexy (9.5 vs 1.9%; p<0.001), suprasellar extension (66.1 vs 45.3%; p=0.003), extrasellar extension (81.2 vs 68.3%; p=0.032) and a higher mean number of pituitary deficiencies at diagnosis (0.4±0.9 vs 0.2±0.6, p=0.020). The clinical diagnosis of most AIPmut patients was gigantism (55.4 vs 18.4%, p<0.001). The mean final height was higher in the AIPmut somatotropinoma subgroup (187.2±18.4 vs 177.2±19.6cm; p<0.001). AIPmut male patients ended up taller than AIPneg males (193.0±17.7 vs 183.0±23.1cm; p=0.002); similarly, AIPmut female patients were taller than AIPneg ones (175.5±13.0 vs 169.2±8.6cm; p=0.007). Both AIPmut and AIPneg groups had more male patients (60.4% in AIPmut and 52.7% in AIPneg groups). The mean number of overall treatments (2.34±1.65 vs 2.32±1.45; p=0.896) or surgical operations (1.05±0.78 vs 1.07±0.63; p=0.745) did not differ significantly between AIPmut and AIPneg somatotropinomas; however, AIPmut patients were more often treated with radiotherapy (41.7 vs 28.0%; p=0.020). Conclusions:AIPmut somatotropinomas present earlier and more often with pituitary apoplexy, suprasellar and extrasellar extensions, and had a higher number of pituitary deficiencies. The remarkably higher final height in the AIPmut setting, both in males and females, likely reflects the earlier onset of disease, but also emphasizes the management challenges as suggested by the increased proportion of patients requiring radiotherapy.

A Novel Mutation of Aryl Hydrocarbon Receptor Interacting Protein Gene Associated with Familial Isolated Pituitary Adenoma Mediates Tumor Invasion and Growth Hormone Hypersecretion

Germline mutations in the aryl hydrocarbon receptor-interacting protein (AIP) gene were identified in nearly 20% of families with familial isolated pituitary adenoma. Some variants of AIP have been confirmed to induce tumor cell proliferation and invasiveness; however, the mechanism is still unclear. A novel missense mutation (c.512C>T, p.T171I) was discovered in 3 patients from a Chinese family with familial isolated pituitary adenoma. In silico and multiplex ligation-dependent probe amplification analysis predicted the mutation to be pathogenic. GH3 and 293FT cell lines were used to verify the variant's effect on cell proliferation (Cell Counting Kit-8), invasiveness (Transwell) and growth hormone (GH) secretion (enzyme-linked immunosorbent assay) by transfection with different vectors: control, blank vector, wild-type AIP, p.T171I variant (experimental group), p.Q315* variant, and AIP small interfering RNA. Furthermore, Zac1, Sstr2, interleukin (IL)-6, and Stat3/phosphorylation-Stat3 expression (reverse transcription polymerase chain reaction, Western blot) in each group was also evaluated. The experimental group, p.Q315* variant group, and AIP small interfering RNA-overexpressing group promoted cell proliferation at 24 and 48 hours, respectively (compared with the control group; P < 0.01 for both). Similarly, the cells in the experimental group manifested more invasion and GH secretion compared with the control group (P < 0.01 and P < 0.05, respectively). Furthermore, the experimental group cells expressed less Sstr2 (a prerequisite for the responsiveness to somatostatin analogues) and Zac1 (tumor suppressor gene), but more IL-6 and phosphorylated-Stat3 (GH-secretion related). The novel AIP mutation c.512C>T (p.T171I) is a pathogenic variant that promoted cell proliferation, invasiveness, and GH secretion through regulation of Sstr2, Zac1, and IL-6/phosphorylated-Stat3 expression.

Interaction of AIP with protein kinase A (cAMP-dependent protein kinase).

Germline mutations in the aryl hydrocarbon receptor-interacting protein (AIP) gene cause mostly somatotropinomas and/or prolactinomas in a subset of familial isolated pituitary adenomas (FIPA). AIP has been shown to interact with phosphodiesterases (PDEs) and G proteins, suggesting a link to the cyclic AMP (cAMP)-dependent protein kinase (PKA) pathway. Upregulation of PKA is seen in sporadic somatotropinomas that carry GNAS mutations, and those in Carney complex that are due to PRKAR1A mutations. To elucidate the mechanism of AIP-dependent pituitary tumorigenesis, we studied potential functional and physical interactions of AIP with PKA's main subunits PRKAR1A (R1α) and PRKACA (Cα). We found that AIP physically interacts with both R1α and Cα; this interaction is enhanced when all three components are present, but maintained during Cα-R1α dissociation by PKA activation, indicating that AIP binds Cα/R1α both in complex and separately. The interaction between AIP and R1α/Cα is reduced when the frequent AIP pathogenic mutation p.R304* is present. AIP protein levels are regulated both by translation and the ubiquitin/proteasome pathway and Cα stabilizes both AIP and R1α protein levels. AIP reduction by siRNA leads to an increase of PKA activity, which is disproportionately enhanced during PDE4-inhibition. We show that AIP interacts with the PKA pathway on multiple levels, including a physical interaction with both the main regulatory (R1α) and catalytic (Cα) PKA subunits and a functional interaction with PDE4-dependent PKA activation. These findings provide novel insights on the mechanisms of AIP-dependent pituitary tumorigenesis.

In vivo bioassay to test the pathogenicity of missense human AIP variants

BackgroundHeterozygous germline loss-of-function mutations in the aryl hydrocarbon receptor-interacting protein gene (AIP) predispose to childhood-onset pituitary tumours. The pathogenicity of missense variants may pose difficulties for genetic counselling and family...

Germline mutations of aryl hydrocarbon receptor-interacting protein (AIP) gene and somatostatin receptor 1-5 and AIP immunostaining in patients with sporadic acromegaly with poor versus good response to somatostatin analogues.

To determine aryl hydrocarbon interacting protein (AIP) gene variations and AIP and somatostatin receptor (SSTR) 1-5 immunostaining in patients with apparently sporadic acromegaly with poor versus good response to somatostatin analogues (SRLs). A total of 94 patients (66 with poor and 28 with good response to SRLs) were screened for the AIP gene variations using Sanger sequencing. Immunostaining was performed in 60 tumors. Several variations, albeit some with undetermined significance, were detected, especially in poor responder patients. The prevalence of AIP mutation was 2.1% in the whole group and 1.5% in patients with poor response to SRLs. AIP, SSTR2A, and SSTR2B immunostainings were decreased in patients with poor response (p < 0.05 for all), and other SSTRs did not differ between the groups (p > 0.05 for all). Patients with low AIP had decreased levels of SSTR2A and SSTR3 (p < 0.05 for all). AIP and SSTR2A immunostainings were positively correlated to the treatment response and age at diagnosis was negatively correlated (p < 0.05 for all). In poor responder patients with high SSTR2A immunostaining, SSTR2B immunostaining and preoperative tumor size were positively and negatively correlated, respectively, to SRL response (p < 0.05 for all). Lack of response to SRLs does not necessarily increase the risk of harboring AIP mutations. The finding of decreased AIP, SSTR2A, and SSTR2B immunostaining in patients with poor response to SRLs and decreased SSTR2A and SSTR3 level in those with low AIP immunostaining suggests a possible interaction between AIP and some SSTR subtypes that might alter SRL sensitivity.

Multi-chaperone function modulation and association with cytoskeletal proteins are key features of the function of AIP in the pituitary gland.

Despite the well-recognized role of loss-of-function mutations of the aryl hydrocarbon receptor interacting protein gene (AIP) predisposing to pituitary adenomas, the pituitary-specific function of this tumor suppressor remains an enigma. To determine the repertoire of interacting partners for the AIP protein in somatotroph cells, wild-type and variant AIP proteins were used for pull-down/quantitative mass spectrometry experiments against lysates of rat somatotropinoma-derived cells; relevant findings were validated by co-immunoprecipitation and co-localization. Global gene expression was studied in AIP mutation positive and negative pituitary adenomas via RNA microarrays. Direct interaction with AIP was confirmed for three known and six novel partner proteins. Novel interactions with HSPA5 and HSPA9, together with known interactions with HSP90AA1, HSP90AB1 and HSPA8, indicate that the function/stability of multiple chaperone client proteins could be perturbed by a deficient AIP co-chaperone function. Interactions with TUBB, TUBB2A, NME1 and SOD1 were also identified. The AIP variants p.R304* and p.R304Q showed impaired interactions with HSPA8, HSP90AB1, NME1 and SOD1; p.R304* also displayed reduced binding to TUBB and TUBB2A, and AIP-mutated tumors showed reduced TUBB2A expression. Our findings suggest that cytoskeletal organization, cell motility/adhesion, as well as oxidative stress responses, are functions that are likely to be involved in the tumor suppressor activity of AIP.

AIP mutations in Brazilian patients with sporadic pituitary adenomas: a single-center evaluation.

Aryl hydrocarbon receptor-interacting protein (AIP) gene mutations (AIPmut) are the most frequent germline mutations found in apparently sporadic pituitary adenomas (SPA). Our aim was to evaluate the frequency of AIPmut among young Brazilian patients with SPA. We performed an observational cohort study between 2013 and 2016 in a single referral center. AIPmut screening was carried out in 132 SPA patients with macroadenomas diagnosed up to 40 years or in adenomas of any size diagnosed until 18 years of age. Twelve tumor samples were also analyzed. Leukocyte DNA and tumor tissue DNA were sequenced for the entire AIP-coding region for evaluation of mutations. Eleven (8.3%) of the 132 patients had AIPmut, comprising 9/74 (12%) somatotropinomas, 1/38 (2.6%) prolactinoma, 1/10 (10%) corticotropinoma and no non-functioning adenomas. In pediatric patients (≤18 years), AIPmut frequency was 13.3% (2/15). Out of the 5 patients with gigantism, two had AIPmut, both truncating mutations. The Y268* mutation was described in Brazilian patients and the K273Rfs*30 mutation is a novel mutation in our patient. No somatic AIP mutations were found in the 12 tumor samples. A tumor sample from an acromegaly patient harboring the A299V AIPmut showed loss of heterozygosity. In conclusion, AIPmut frequency in SPA Brazilian patients is similar to other populations. Our study identified two mutations exclusively found in Brazilians and also shows, for the first time, loss of heterozygosity in tumor DNA from an acromegaly patient harboring the A299V AIPmut. Our findings corroborate previous observations that AIPmut screening should be performed in young patients with SPA.

AIP and the somatostatin system in pituitary tumours.

Classic somatostatin analogues aimed at somatostatin receptor type 2, such as octreotide and lanreotide, represent the mainstay of medical treatment for acromegaly. These agents have the potential to decrease hormone secretion and reduce tumour size. Patients with a germline mutation in the aryl hydrocarbon receptor-interacting protein gene, AIP, develop young-onset acromegaly, poorly responsive to pharmacological therapy. In this review, we summarise the most recent studies on AIP-related pituitary adenomas, paying special attention to the causes of somatostatin resistance; the somatostatin receptor profile including type 2, type 5 and truncated variants; the role of G proteins in this pathology; the use of first and second generation somatostatin analogues; and the role of ZAC1, a zinc-finger protein with expression linked to AIP in somatotrophinoma models and acting as a key mediator of octreotide response.