Resistant Paediatric Somatotropinomas due to AIP Mutations: Role of Pegvisomant

Growth hormone receptor antagonist pegvisomant and its role in the medical therapy of growth hormone excess

Pegvisomant is a growth-hormone (GH) receptor antagonist that prevents the formation of the active heterotrimer of the dimerised GH receptor and the GH molecule necessary for downstream signal transduction. Over the past 20 years, it has become a key therapeutic option for physicians treating syndromes of GH/IGF-1 excess. Sufficient longitudinal follow-up data suggest that it can be deemed both safe and effective. It is the drug with the greatest potential for achieving an amelioration of the biochemical effects of GH excess with a corresponding normalisation of IGF-1 levels; however, insufficient dose titration has lessened real-world therapeutic outcomes. Theoretical concerns about stimulating tumour growth have been resolved as this has not been observed, while derangement of liver enzymes and local skin-related adverse reactions may occur in a minority of the patients. It may be a particularly impactful medication for the treatment of children, young people, and those with inherited disorders of GH excess, where other treatment modalities often fail. Combination therapy of pegvisomant with first- and second-generation somatostatin receptor ligands or with dopamine agonists remains an ongoing area of interest and research. High cost remains a barrier to the use of pegvisomant in many settings.

An update on, and genetics of refractory adenomas of childhood

Pituitary adenomas in childhood tend to be more frequently due to germline genetic changes and are often diagnosed at late stages due to delayed recognition by pediatricians and other caretakers who are not familiar with this rare disease in childhood. As a result, often, pediatric pituitary adenomas are aggressive or remain refractory to treatment. In this review, we discuss germline genetic defects that account for the most common pediatric pituitary adenomas that are refractory to treatment. We also discuss some somatic genetic events, such as chromosomal copy number changes that characterize some of the most aggressive pituitary adenomas in childhood that end up being refractory to treatment.

Pediatric growth hormone and prolactin-secreting tumor associated with an AIP mutation and a MEN1 variant of uncertain significance

OBJECTIVES

Pituitary gigantism is a rare condition and it often has an identifiable genetic cause. In this article we report a case of a young girl with pituitary gigantism and two genetic changes.

CASE PRESENTATION

A 15-year-old girl with primary amenorrhea was diagnosed with a growth hormone (GH) and prolactin (PRL)-producing tumor, needing surgery and medical treatment with octreotide in order to achieve disease control. The co-occurrence of an AIP mutation and a MEN1 variant of uncertain significance was demonstrated in this patient. The germline mutation involving AIP was inherited from her father who at the age of 55 was unaffected and the MEN1 variant was a de novo duplication of the region 11q13.1. The latter variant, not previously reported, is unlikely to be pathogenic. Nonetheless, screening for other components of multiple endocrine neoplasia type 1 (MEN1) was performed and proved negative.

CONCLUSIONS

The rare co-occurrence of an AIP mutation and a MEN 1 variant of uncertain significance was demonstrated in this patient.

Complicated Clinical Course in Incipient Gigantism Due to Treatment-resistant Aryl Hydrocarbon Receptor–Interacting Protein–mutated Pediatric Somatotropinoma

Background

Our objective was to describe the clinical course and treatment challenges in a very young patient with a pituitary adenoma due to a novel aryl hydrocarbon receptor–interacting protein (AIP) gene mutation, highlighting the limitations of somatostatin receptor immunohistochemistry to predict clinical responses to somatostatin analogs in acromegaly.

Case Report

We report the case of a 7-year-old boy presenting with headache, visual field defects, and accelerated growth following failure to thrive. The laboratory results showed high insulin-like growth factor I (IGF-I) (standardised deviation scores ( +3.49) and prolactin levels (0.5 nmol/L), and magnetic resonance imaging identified a pituitary macroadenoma. Tumoral/hormonal control could not be achieved despite 3 neurosurgical procedures, each time with apparent total resection or with lanreotide or pasireotide. IGF-I levels decreased with the GH receptor antagonist pegvisomant. The loss of somatostatin receptor 5 was observed between the second and third tumor resection. In vitro, no effect on tumoral GH release by pasireotide (with/without cabergoline) was observed. Genetic analysis revealed a novel germline AIP mutation: p.Tyr202∗ (pathogenic; class 4).

Discussion

In vitro response of tumor tissue to somatostatin may better predict tumoral in vivo responses of somatostatin analogs than somatostatin receptor immunohistochemistry.

Conclusion

We identified a novel pathologic AIP mutation that was associated with incipient acrogigantism in an extremely young patient who had a complicated course of disease. Growth acceleration can be masked due to failure to thrive. Tumoral growth hormone release in vivo may be predicted with in vitro exposure to somatostatin receptor analogs, as it cannot be assumed that all AIP-mutated somatotropinomas respond well to pasireotide.

Genetics, clinical features and outcomes of non-syndromic pituitary gigantism: experience of a single center from Sao Paulo, Brazil

PURPOSE

Non-syndromic pituitary gigantism (PG) is a very rare disease. Aryl hydrocarbon receptor-interacting protein (AIP) and G protein-coupled receptor 101 (GPR101) genetic abnormalities represent important etiologic causes of PG and may account for up to 40% of these cases. Here, we aimed to characterize the clinical and molecular findings and long-term outcomes in 18 patients (15 males, three females) with PG followed at a single tertiary center in Sao Paulo, Brazil.

METHODS

Genetic testing for AIP and GPR101 were performed by DNA sequencing, droplet digital PCR and array comparative genomic hybridization (aCGH).

RESULTS

Pathogenic variants in the AIP gene were detected in 25% of patients, including a novel variant in splicing regulatory sequences which was present in a sporadic male case. X-LAG due to GPR101 microduplication was diagnosed in two female patients (12.5%). Of interest, these patients had symptoms onset by age 5 and 9 years old and diagnosis at 5 and 15 years, respectively. X-LAG, but not AIP, patients had a significantly lower age of symptoms onset and diagnosis and a higher height Z-score when compared to non-X-LAG. No other differences in clinical features and/or treatment outcomes were observed among PG based on their genetic background.

CONCLUSION

We characterize the clinical and molecular findings and long-term outcome of the largest single-center PG cohort described so far.

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

CONTEXT

Germline 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).

OBJECTIVE

To 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.

DESIGN

12-year prospective, observational study.

PARTICIPANTS & SETTING

We 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).

RESULTS

Prospectively 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).

CONCLUSIONS

Prospectively 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.

Aggressive pituitary tumors in the young and elderly

Aggressive pituitary tumors (APTs) represent rare pituitary adenomas (PAs) with local invasion of surrounding tissues, increased risk for multiple recurrence, rapid tumor growth, or resistance to standard therapies. The most common APTs in children and adolescents are giant prolactinomas and somatotropinomas. Few cases of Crooke's cell adenomas, silent corticotroph adenomas and pituitary carcinomas have also been reported in the literature. Pediatric patients with APTs have higher risk of harboring germline genetic defects, most commonly in the MEN1 and AIP genes. Since certain genetic defects confer a more aggressive behavior to PAs, genetic testing should be considered in tumors with young onset and positive family history. The management of pediatric APTs involves usually a combination of standard therapies (surgical, medical, radiation). Newer agents, such as temozolomide, have been used in few cases of pediatric pituitary tumors with promising results. In the elderly, PAs are more commonly non-functioning. Their management often poses dilemmas given the coexistence of age-related comorbidities. However, standard surgical treatment and temozolomide seem to be safe and well tolerated in elderly patients.

The Genetics of Pituitary Adenomas

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

AIP-mutated acromegaly resistant to first-generation somatostatin analogs: long-term control with pasireotide LAR in two patients

Acromegaly is a rare disease due to chronic excess growth hormone (GH) and IGF-1. Aryl hydrocarbon receptor interacting protein (AIP) mutations are associated with an aggressive, inheritable form of acromegaly that responds poorly to SST2-specific somatostatin analogs (SSA). The role of pasireotide, an SSA with affinity for multiple SSTs, in patients with AIP mutations has not been reported. We studied two AIP mutation positive acromegaly patients with early-onset, invasive macroadenomas and inoperable residues after neurosurgery. Patient 1 came from a FIPA kindred and had uncontrolled GH/IGF-1 throughout 10 years of octreotide/lanreotide treatment. When switched to pasireotide LAR, he rapidly experienced hormonal control which was associated with marked regression of his tumor residue. Pasireotide LAR was stopped after >10 years due to low IGF-1 and he maintained hormonal control without tumor regrowth for >18 months off pasireotide LAR. Patient 2 had a pituitary adenoma diagnosed when aged 17 that was not cured by surgery. Chronic pasireotide LAR therapy produced hormonal control and marked tumor shrinkage but control was lost when switched to octreotide. Tumor immunohistochemistry showed absent AIP and SST2 staining and positive SST5. Her AIP mutation positive sister developed a 2.5 cm follicular thyroid carcinoma aged 21 with tumoral loss of heterozygosity at the AIP locus and absent AIP staining. Patients 1 and 2 required multi-modal therapy to control diabetes. On stopping pasireotide LAR after >10 years of treatment, Patient 1's glucose metabolism returned to baseline levels. Long-term pasireotide LAR therapy can be beneficial in some AIP mutation positive acromegaly patients that are resistant to first-generation SSA.