Screening of AIP Gene Variations in a Cohort of Turkish Patients with Young-Onset Sporadic Hormone-Secreting Pituitary Adenomas

Reassessing the role of the p.(Arg304Gln) missense AIP variant in pituitary tumorigenesis

OBJECTIVE

Heterozygous germline loss-of-function variants in AIP are associated with young-onset growth hormone and/or prolactin-secreting pituitary tumours. However, the pathogenic role of the c.911G > A; p.(Arg304Gln) (R304Q) AIP variant has been controversial. Recent data from public exome/genome databases show this variant is not infrequent. The objective of this work was to reassess the pathogenicity of R304Q based on clinical, genomic, and functional assay data.

DESIGN

Data were collected on published R304Q pituitary neuroendocrine tumour cases and from International Familial Isolated Pituitary Adenoma Consortium R304Q cases (n = 38, R304Q cohort). Clinical features, population cohort frequency, computational analyses, prediction models, presence of loss-of-heterozygosity, and in vitro/in vivo functional studies were assessed and compared with data from pathogenic/likely pathogenic AIP variant patients (AIPmut cohort, n = 184).

RESULTS

Of 38 R304Q patients, 61% (23/38) had growth hormone excess, in contrast to 80% of AIPmut cohort (147/184, P < .001). R304Q cohort was older at disease onset and diagnosis than the AIPmut cohort (median [quartiles] onset: 25 y [16-35] vs 16 y [14-23], P < .001; median [quartiles] diagnosis: 36 y [24-44] vs 21 y [15-29], P < .001). R304Q is present in gnomADv2.1 (0.31%) and UK Biobank (0.16%), including three persons with homozygous R304Q. No loss-of-heterozygosity was detected in four R304Q pituitary neuroendocrine tumour samples. In silico predictions and experimental data were conflicting.

CONCLUSIONS

Evidence suggests that R304Q is not pathogenic for pituitary neuroendocrine tumour. We recommend changing this variant classification to likely benign and do not recommend pre-symptomatic genetic testing of family members or follow-up of already identified unaffected individuals with the R304Q variant.

The clinical and therapeutic profiles of prolactinomas associated with germline pathogenic variants in the aryl hydrocarbon receptor interacting protein (AIP) gene

Introduction

Prolactinomas are the most frequent type of pituitary adenoma encountered in clinical practice. Dopamine agonists (DA) like cabergoline typically provide sign/ symptom control, normalize prolactin levels and decrease tumor size in most patients. DA-resistant prolactinomas are infrequent and can occur in association with some genetic causes like MEN1 and pathogenic germline variants in the AIP gene (AIPvar).

Methods

We compared the clinical, radiological, and therapeutic characteristics of AIPvar-related prolactinomas (n=13) with unselected hospital-treated prolactinomas ("unselected", n=41) and genetically-negative, DA-resistant prolactinomas (DA-resistant, n=39).

Results

AIPvar-related prolactinomas occurred at a significantly younger age than the unselected or DA-resistant prolactinomas (p<0.01). Males were more common in the AIPvar (75.0%) and DA- resistant (49.7%) versus unselected prolactinomas (9.8%; p<0.001). AIPvar prolactinomas exhibited significantly more frequent invasion than the other groups (p<0.001) and exhibited a trend to larger tumor diameter. The DA-resistant group had significantly higher prolactin levels at diagnosis than the AIPvar group (p<0.001). Maximum DA doses were significantly higher in the AIPvar and DA-resistant groups versus unselected. DA-induced macroadenoma shrinkage (>50%) occurred in 58.3% in the AIPvar group versus 4.2% in the DA-resistant group (p<0.01). Surgery was more frequent in the AIPvar and DA- resistant groups (43.8% and 61.5%, respectively) versus unselected (19.5%: p<0.01). Radiotherapy was used only in AIPvar (18.8%) and DA-resistant (25.6%) groups.

Discussion

AIPvar confer an aggressive phenotype in prolactinomas, with invasive tumors occurring at a younger age. These characteristics can help differentiate rare AIPvar related prolactinomas from DA-resistant, genetically-negative tumors.

AIP gene germline variants in adult Polish patients with apparently sporadic pituitary macroadenomas

INTRODUCTION

Up to 5% of all pituitary tumors are hereditary e.g. due to MEN1 or aryl hydrocarbon receptor-interacting protein (AIP) genes mutations.

OBJECTIVES

The study was aimed at the assessment of the frequency and characteristics of AIP-mutation related tumors in patients with apparently sporadic pituitary macroadenomas in the Polish population.

MATERIALS AND METHODS

The study included 131 patients (57 males, 74 females; median age 42 years) diagnosed with pituitary macroadenomas, and with a negative family history of familial isolated pituitary adenoma (FIPA) or multiple endocrine neoplasia type 1 (MEN1) syndromes. Sanger sequencing was used for the assessment of AIP gene variants. The study was approved by the Ethics Board of JUMC.

RESULTS

AIP variants were identified in five of the 131 included subjects (3.8%): one diagnosed with Cushing's disease, two with acromegaly, and two with non-secreting adenomas. Patients harboring hereditary AIP gene alterations did not differ from the rest of the study group in median age at diagnosis (41.0 vs. 42.5 years, P=0.8), median largest tumor diameter (25 vs. 24 mm, P=0.6), gender distribution (60.0% vs. 56.3% females, P=0.8), secreting tumor frequency (60.0% vs. 67.5%, P=0.7), or acromegaly diagnosis frequency (40.0% vs.37.3%, P=0.9).

CONCLUSIONS

In our series of apparently sporadic pituitary macroadenomas, AIP gene variant carriers did not differ substantially from patients with negative genetic testing. A risk factor-centred approach to AIP genetic screening may result in missing germline variants. Considering the clinical impact of such genetic variants and their relatively low penetrance, it is, however, doubtful if general genetic screening benefits the whole cohort of pituitary macroadenoma patients and their families.

Management of prolactinomas in children and adolescents; which factors define the response to treatment?

PURPOSE

Prevalence, presentation and clinical outcome of prolactinomas vary in children and adults. In this study, we evaluated the clinical features and outcome of children and adolescents with prolactinoma to identify the differences from that of adults, and thus to establish the management strategies for this age group.

METHODS

Patients with prolactinoma diagnosed before 18 years of age from a single center in the last 20-years were included. Clinical and laboratory data, radiological findings and treatment outcome were evaluated retrospectively.

RESULTS

Twenty-eight patients (23 female; 82.1%) with prolactinoma were included. Median age at diagnosis was 15.2 years (12.6-17.7 years) in girls, 12.9 years (12.0-16.7 years) in boys. First line treatment was cabergoline in 82% of patients and normal prolactin level was achieved with maximum dose of 2 mg/week in 78%. Surgery was required in 28% of patients. Adenomas < 13.5 mm responded conventional doses of CAB. Adenomas > 30 mm were drug resistant or required surgery. Adenomas between 13.5 mm and 30 mm with invasion/extension were more likely to have drug resistance. CAB had to be continued following surgery in all patients. One macroprolactinoma had an increase in size which was accompanied with increasing prolactin level.

CONCLUSIONS

All microprolactinomas responded well to DA treatment. However, all adenomas larger than 30 mm was resistant to CAB or required surgery. Probability of drug resistance and requirement of second line therapy were higher in adenomas between 13.5 mm and 30 mm with invasion/extension. Doses over 2 mg/week of CAB in drug-resistant patients may not provide additional benefit. The frequency of follow-up MRI could be determined based on prolactin levels and emergence of new neurological symptoms.

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

CONTEXT

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.

OBJECTIVE

To explore the phenotype and genotype of a large kindred carrying the p.R304Q AIP variant.

METHODS

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.

RESULTS

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 >50 years) were screened for the PDE11A and ALG14 variant; both variants were present in five of ten persons.

CONCLUSIONS

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.

Clinical Relevance of Genetic Analysis in Patients With Pituitary Adenomas: A Systematic Review

Pituitary adenomas (PA) are amongst the most prevalent intracranial tumors, causing complications by hormonal overproduction or deficiency and tumor mass effects, with 95% of cases occurring sporadically. Associated germline mutations (AIP, MEN1, CDKN1B, PRKAR1A, SDHx) and Xq26.3 microduplications are increasingly identified, but the clinical consequences in sporadic PA remain unclear. This systematic review evaluates predictors of a genetic cause of sporadic PA and the consequences for treatment outcome. We undertook a sensitive MEDLINE/Pubmed, EMBASE, and Web of Science search with critical appraisal of identified studies. Thirty-seven studies on predictors of mutations and 10 studies on the influence on treatment outcome were included. AIP and MEN1 mutations were associated with young age of PA diagnosis. AIP mutations were also associated with gigantism and macroadenomas at time of diagnosis. Xq26.3 microduplications were associated with PA below the age of five. AIP and MEN1 mutation analysis is therefore recommended in young patients (≤30 years). AIP mutation analysis is specifically recommended for patients with PA induced gigantism and macroadenoma. Screening for Xq26.3 microduplications is advisable in children below the age of five with increased growth velocity due to PA. There is no evidence supporting mutation analysis of other genes in sporadic PA. MEN1 mutation related prolactinoma respond well to dopamine agonists while AIP mutation associated somatotroph and lactotroph adenoma are frequently resistant to medical treatment. In patients harboring an Xq26.3 microduplication treatment is challenging, although outcome is not different from other patients with PA induced gigantism. Effective use of genetic analysis may lead to early disease identification, while knowledge of the impact of germline mutations on susceptibility to various treatment modalities helps to determine therapeutic strategies, possibly lowering disease morbidity.