Laura Cristina Hernández Ramírez

Loss-of-function (LOF) germline AIP variants are the main genetic cause of familial isolated pituitary adenoma and gigantism. A role for this defect in other neoplasms has been suggested, but remains unclear. We investigated the frequency, associated phenotypes, and in vitro functional effects of germline AIP variants in a cohort of Mexican patients with neuroendocrine neoplasms (NENs). Blood DNA samples from 101 adults (70.3% females) with isolated or syndromic NENs (50 with pituitary neuroendocrine tumors, PitNETs) were analyzed using a next generation sequencing panel. Targeted Sanger screening was carried out in additional family members and tumor samples. Missense and intronic variants were functionally assessed via cycloheximide chase assays or quantitative polymerase chain reaction plus sequence analysis of blood cDNA, as appropriate. Two rare likely benign defects (c.787 + 9C>T and p.T231M), two variants of uncertain significance (p.R106C and p.V291_L292del), one likely pathogenic (LP, p.C238Y), and one pathogenic (p.R304*) variant were found in six cases (5.9%). One individual was diagnosed with multiple gastric NENs and five carried PitNETs. Variant p.V291_L292del produced an unstable protein (P < 0.0001 for half-life curve, compared with wild type) and was reclassified to LP. Loss of heterozygosity in a gastric neuroendocrine tumor and nonsignificantly increased protein stability were observed for p.R106C. No deleterious effects were documented for c.787 + 9C>T. In conclusion, we determined the prevalence of AIP variants in a cohort of NENs and reclassified one VUS to LP. Our findings support the causal association of AIP LOF with PitNETs, but cannot rule out a role for AIP in other NENs.

Context: Genetic tests are part of the routine clinical approach to syndromic and nonsyndromic phenotypes of neuroendocrine neoplasms (NENs). Current data on phenotype–genotype associations in NENs, however, do not accurately represent all populations. Objective: To describe the frequency, inventory, and clinical associations of germline defects associated with multiple types of NENs in a Mexican cohort. Methods: Blood DNA from Mexican adults with NENs was analyzed with a 53-gene next-generation sequencing panel developed ad hoc (n = 90) or Sanger sequencing (n = 2). Single nucleotide variants, indels, and structural variants were identified, classified, and subjected to orthogonal confirmation. When possible, tumor samples and blood DNA from additional family members were tested using Sanger sequencing. Results: Ninety-two probands (70.7% women, 51.5% sporadic) were included; 16 carried pathogenic or likely pathogenic (P/LP) variants and were significantly younger at disease onset than the rest (29.6 ± 10.7 vs 40 [21.5-51.5] years, P = .0384). Likely driving variants were identified in three-quarters of Von Hippel Lindau syndrome cases, one-third of multiple endocrine neoplasia (MEN) type 1, one-quarter of early-onset acromegaly/gigantism, and individual cases of Cushing's disease, MEN2A, and medullary thyroid carcinoma. One patient with clinical MEN1 associated with an SDHA variant and 1 with a pituitary tumor and neurofibromatosis type 1 were also identified. Probands with familial disease were more likely to carry P/LP variants than sporadic cases (26.7 vs 8.5%, P = .0282). Conclusion: P/LP variants were identified in 17.4% of individuals with NENs. Our research provides a view of the landscape of NEN drivers in a population not previously characterized.

Introduction: Patients with neurofibromatosis type 1 (NF1) are at risk for developing various neoplasms. Since the early twentieth century, multiple cases of pituitary neuroendocrine tumors (PitNETs) occurring in this context have been published. Yet, the role of NF1 (17q11.2) loss-of-function (LOF) variants in pituitary tumorigenesis remains unclear.Aim: We report the clinical and molecular characterization of a case of PitNET diagnosed in a patient with NF1. We also review the available data for and against a causal association between NF1 defects and pituitary tumors.Methods: Our patient was recruited via an ongoing prospective study of individuals with neuroendocrine neoplasms. Genetic testing was carried out by means of targeted next generation sequencing (NGS) and Sanger sequencing in blood and tumor DNA, respectively. NF1 expression was analyzed via quantitative polymerase chain reaction (qPCR) in blood and tumor cDNA. Similar cases were searched in the literature.Results: A 54-year-old-man was incidentally diagnosed with a clinically non-functioning PitNET via brain imaging. He had a personal and family history of NF1 and carried the germline pathogenic variant NF1 (NM_001042492.3): c.147C>A, p.Y49*. Via transsphenoidal surgery, a 16 mm lesion was resected, showing strong granular cytoplasmic immunoreactivity with patchy distribution for NF1 and preserved heterozygosity for the NF1 defect. Additional NGS ruled out germline defects in PitNET-associated genes. By qPCR, NF1 was significantly overexpressed in the tumor when compared with another NF-PitNET, but not when compared with a corticotropinoma. We reviewed twenty-three case reports of PitNETs occurring in patients with either clinical NF1 without genetic study, individuals with NF1 germline variants with or without clinical NF1 or associated with somatic NF1 defects. Predominance of GH-secreting and large PitNETs, with young-onset in around half of the cases, were noticed. Two individuals developed multiple endocrine neoplasia-like phenotypes but tested negative for other relevant genetic defects.Conclusions: Although the association of NF1 and PitNETs could be coincidental, the clinical characteristics of the reviewed cases differ from those of typical incidentalomas. NF1 could drive pituitary tumorigenesis via haploinsufficiency, but this hypothesis requires further research. Additional clinical and molecular data from large cohorts of affected individuals should help clarify this question.

The most common genetic drivers of pituitary neuroendocrine tumors (PitNETs) lie within mutational hotspots, which are genomic regions where variants tend to cluster. Some of these hotspot defects are unique to PitNETs, while others are associated with additional neoplasms. Hotspot variants in GNAS and USP8 are the most common genetic causes of acromegaly and Cushing’s disease, respectively. Although it has been proposed that these genetic defects could define specific clinical phenotypes, results are highly variable among studies. In contrast, DICER1 hotspot variants are associated with a familial syndrome of cancer predisposition, and only exceptionally occur as somatic changes. A small number of non-USP8-driven corticotropinomas are due to somatic hotspot variants in USP48 or BRAF; the latter is a well-known mutational hotspot in cancer. Finally, somatic variants affecting a hotspot in SF3B1 have been associated with multiple cancers and, more recently, with prolactinomas. Since the associations of BRAF, USP48, and SF3B1 hotspot variants with PitNETs are very recent, their effects on clinical phenotypes are still unknown. Further research is required to fully define the role of these genetic defects as disease biomarkers and therapeutic targets.

Pituitary adenomas (PAs) are common, usually benign tumors of the anterior pituitary gland which, for the most part, have no known genetic cause. PAs are associated with major clinical effects due to hormonal dysregulation and tumoral impingement on vital brain structures. Following the identification of a loss-of-function variant (p.Arg703Gln) in the PAM gene in a family with pituitary gigantism, we investigated 299 individuals with sporadic PAs and 17 familial isolated pituitary adenomas kindreds for PAM variants. PAM encodes a multifunctional protein responsible for the essential C-terminal amidation of secreted peptides. Genetic screening was performed by germline and tumor sequencing and germline copy number variation (CNV) analysis. No germline CNVs or somatic single nucleotide variants (SNVs) were identified. We detected seven likely pathogenic heterozygous missense, truncating, and regulatory SNVs. These SNVs were found in sporadic subjects with GH excess (p.Gly552Arg and p.Phe759Ser), pediatric Cushing disease (c.-133T>C and p.His778fs), or with different types of PAs (c.-361G>A, p.Ser539Trp, and p.Asp563Gly). The SNVs were functionally tested in vitro for protein expression and trafficking by Western blotting, for splicing by minigene assays, and for amidation activity in cell lysates and serum samples. These analyses confirmed a deleterious effect on protein expression and/or function. By interrogating 200,000 exomes from the UK Biobank, we confirmed a significant association of the PAM gene and rare PAM SNVs to diagnoses linked to pituitary gland hyperfunction. Identification of PAM as a candidate gene associated with pituitary hypersecretion opens the possibility of developing novel therapeutics based on altering PAM function.

Context Ectopic posterior pituitary (EPP), a condition in which the posterior pituitary gland is displaced due to defective neuronal migration, is frequently associated with hypopituitarism. Genetic variants play a role, but many cases remain unexplained. Objective A large EPP cohort was studied to explore the importance of genetic variants and how they correlate with clinical findings. Methods Whole exome sequencing was performed on a discovery sample of 27 cases to identify rare variants. The variants that met the criteria for rarity and biological relevance, or that were previously associated with EPP (ROBO1 and HESX1), were then resequenced in the 27 cases plus a replication sample of 51 cases. Results We identified 16 different variants in 12 genes in 15 of the 78 cases (19.2%). Complete anterior pituitary deficiency was twice as common in cases with variants of interest compared to cases without variants (9/15 [60%] vs 19/63 [30.1%], respectively; Z test, P = 0.06). Breech presentation was more frequent in the variant positive group (5/15 vs 1/63; Z test, P = 0.003). Four cases had variants in ROBO1 and 1 in HESX1, genes previously associated with EPP. The ROBO1 p.S18* variant has not been reported previously; ROBO1 p.Q1227H has not been associated with EPP previously. Conclusion EPP cases with variants of interest identified in this study were more likely to present with severe clinical disease. Several variants were identified in genes not previously associated with EPP. Our findings confirm that EPP is a multigenic disorder. Future studies are needed to identify additional genes.

Objective: Pituitary adenomas (PA) are rare in young patients, and additional studies are needed to fully understand their pathogenesis in this population. We describe the clinical and genetic characteristics of apparently sporadic PA in a cohort of young patients. Design: Clinical and molecular analysis of 235 patients (age ≤ 30 years) with PA. Clinicians from several Spanish and Chilean hospitals provided data. Methods: Genetic screening was performed via next-generation sequencing and comparative genomic hybridization array. Clinical variables were compared among paediatric, adolescent (MEN1 alterations or a limited clinical expression of the syndrome. Despite the low penetrance observed, screening of AIP and MEN1 variants in young patients and relatives is of clinical value.