CONTEXT:Patients with multiple endocrine neoplasia type 1 (MEN1) are genetically predisposed to developing tumors of the parathyroid, pancreas, and anterior pituitary. While widespread genetic testing has increased early diagnoses, the value of radiological surveillance for pituitary adenomas in these patients remains unclear. OBJECTIVE:To investigate the impact of pituitary magnetic resonance imaging (MRI) findings on patient management in MEN1. DESIGN:Retrospective longitudinal cohort study. SETTING:NIH Clinical Center. PATIENTS:Genetically confirmed MEN1 evaluated between 1977 and September 2024. MEASURES:Cumulative proportion and rate of intervention for nonfunctional adenomas. RESULTS:Three hundred twenty patients with a mean follow-up duration of 14 ± 12 years were identified. One hundred eighty-two out of 320 patients (57%) had pituitary adenomas, of whom 95/182 (52%) had nonfunctional adenomas. All patients with adenoma had biochemical evaluation at the time of pituitary MRI. There were 21/95 (22%) patients with nonfunctional adenomas that needed an intervention throughout their follow-up. The rate of intervention per 100 patient-years for nonfunctional adenomas was 3.1% (confidence interval 2.0-4.7%). All patients with nonfunctional adenoma who required an intervention reported symptoms or had an abnormal pituitary function test. Tumor volume of 38/48 (79%) nonfunctional adenomas followed over a mean of 8.3 ± 6.1 years remained stable. Only 42/518 (8.1%) MRIs for nonfunctional adenomas were prompted by clinical or biochemical abnormalities. Individualized imaging could have avoided approximately 4 MRIs per patient with nonfunctional microadenoma over their follow-up. CONCLUSION:In an overwhelming majority of patients with MEN1, radiological surveillance for nonfunctional pituitary adenomas offers minimal added benefit beyond patient-reported symptoms and pituitary function testing.

A substantial fraction (60-85%) of hereditary primary hyperparathyroidism (hPHPT) lacks an identifiable genetic etiology. We describe fumarate hydratase (FH) mutations as a potential cause of hPHPT, expanding the phenotypic spectrum of FH deficiency tumor predisposition syndromes. In an index patient who presented with asymptomatic hypercalcemia and a chief-to-transitional cell-dominant parathyroid adenoma, whole-exome sequencing revealed two unique heterozygous FH variants (germline p.Gln376fs*2; somatic p.Pro503_Lys504dup). Functional inactivation of FH was supported by diffuse nuclear and cytoplasmic 2-succinocysteine immunoreactivity and elevated fumarate/malate ratio in tumor tissue. This individual did not show classic HLRCC manifestations. Preserved FH protein expression suggested residual enzymatic activity, which may account for an attenuated phenotype. To assess broader relevance, no additional patients with bona fide FH-deficient parathyroid adenoma were identified among 130 individuals with suspected hPHPT of unknown etiology evaluated at our institute. In a complementary cohort of 11 patients with pheochromocytoma/paraganglioma syndrome harboring pathogenic germline heterozygous FH variants, one female (FH p.Thr234Ala) presented with multi-gland disease requiring parathyroidectomy at age 40 years, features suspicious for hPHPT. These findings support fumarate hydratase deficiency as a plausible etiology for a subset of parathyroid adenomatous disease. Thus, consideration of parathyroid function surveillance in patients with fumarate hydratase deficiency tumor predisposition syndromes may be warranted. CLINICAL TRIAL NUMBER: NCT04969926.

Objective:The aim of this study was to evaluate the efficacy of 6-18F-fluoro-L-3,4-dihydroxyphenylalanine (18F-FDOPA) positron emission tomography/computed tomography (PET/CT) in the identification of primary and metastatic NETs in patients with multiple endocrine neoplasia type 1 (MEN1). Design:This prospective MEN1 cohort study evaluated 16 genetically confirmed patients with MEN1. Inpatient subjects were imaged using CT, magnetic resonance imaging (MRI), 68Ga-DOTATATE PET/CT, and 18F-FDOPA PET/CT. A composite reference test combining up to 3 years of historical imaging and a multidisciplinary evaluation was used against the index test. Lesion-, patient-, and site-based analyses were performed. Setting:The NIH Clinical Center was the setting for this study. Patients:Patients with germline MEN1 variants confirmed to have MEN1 were included in the study. Results:A total of 134 lesions were identified after review of CT, MRI, and 68Ga-DOTATATE PET/CT. 18F-FDOPA PET/CT detected 17% (23/134, 95% CI: 8.2-27.1). Of the total study participants, 50% (8/16) of the patients had 18F-FDOPA PET/CT uptake in primary and metastatic sites with overlapping 68Ga-DOTATATE PET/CT uptake and localization on CT and MRI. Region-based analysis showed that 18F-FDOPA PET/CT had the highest avidity for lung (4/12, 33%) and pancreatic (8/38, 21%) NETs. Conclusion:18F-FDOPA PET/CT has low efficacy overall in detecting MEN1-related NETs. Clinical Trial Registration:https://clinicalstudies.info.nih.gov/protocoldetails.aspx?id=000344-DK&&query=, identifier NCT04969926.

Glial cells missing 2 (GCM2) is an essential transcription factor for the development of parathyroid glands. Germline GCM2 variants that repress or enhance transcriptional activity predispose a subset of patients to hypoparathyroidism or hyperparathyroidism, respectively. A recurrent germline heterozygous activating missense variant of GCM2, p.Y394S has been identified in some patients with primary hyperparathyroidism. A genetically engineered knock-in mouse model of this variant corresponding to p.Y392S in the mouse Gcm2 gene (Gcm2 +/Y392S) did not show obvious parathyroid tumors. However, in GCM2-binding site mediated luciferase reporter assays in HEK293 cells, the mouse and the human variant both exhibited enhanced transcriptional activity. Therefore, we assessed the effect of this variant on gene expression in vivo in parathyroid glands from Gcm2 +/Y392S and WT mice. Using the 10x Genomics Visium platform, spatially resolved transcriptomic analysis was performed on formalin-fixed and paraffin-embedded (FFPE) tracheal tissue sections of Gcm2 +/Y392S and WT mice to capture RNA from parathyroid glands together with other cell types in the tissue sections. Transcriptome sequence data analysis detected 8 different clusters in the tissue sections based on similarity of gene expression profiles. Cluster-1, which contained parathyroid gland cells expressing Pth and Gcm2, was further evaluated for transcripts that were differentially expressed more than 2-fold in Gcm2 +/Y392S compared to WT. Increased transcript level of Lgals3 (galectin-3) was seen in Gcm2 +/Y392S parathyroid gland cells which is among markers of parathyroid carcinoma. Galectin-3 protein was detected in available FFPE human parathyroid samples of patients with germline heterozygous activating GCM2 variants, p.Y394S (n = 4/10) or p.L379Q (n = 2/2). These results indicate a potential for growth and malignancy of parathyroid glands expressing GCM2 variants. The transcriptomic data of mouse parathyroid gland cells generated in this study can serve as a valuable resource for investigating genes and pathways in normal or abnormal parathyroid gland growth and physiology.

Context:Approximately 50% to 70% of patients with multiple endocrine neoplasia type 1 (MEN1) die of duodenopancreatic neuroendocrine tumors (NETs). While c-MET inhibitors in combination with antivascular endothelial growth factor therapy have been shown to result in longer progression-free survival in patients with sporadic NETs, data regarding their efficacy in patients with MEN1-related NETs are lacking. Objective:We sought to characterize c-MET expression in MEN1-related NETs and evaluate its association with clinicopathologic characteristics. Methods:Forty-three tumors from 22 genetically confirmed patients with MEN1-related metastatic NETs were identified. Of these, 15 of 22 (68%) patients had distant metastases while the remaining 7 of 22 had locoregional metastases. Results:c-MET expression was assessed in these tumors via immunohistochemistry. A total of 19 of 43 (44%) were primary tumors (duodenum, pancreas, stomach) while the remaining were metastases. c-MET expression was scored as strongly positive in 3 of 43 (H-score >50), weakly positive in 6 of 43 (H-score: 10-50), and negative in 34 of 43 (H-score <10) tumors. All 3 tumors with strong positive c-MET expression were from patients with a distinctly aggressive clinical course. The 6 tumors with weakly positive c-MET expression were from patients with stable disease, including 4 with distant metastases. Of the 13 patients with all tumors negative for c-MET expression, all but 1 had stable disease. Age at initial NET diagnosis; tumor site, type or grade; number of sites of distant metastases; total number of surgeries for NETs; or the stability of overall tumor burden did not predict c-MET expression. Conclusion:Our findings suggest a role for c-MET inhibition in personalizing therapy for patients with MEN1-related NETs.

Establishing genotype-phenotype correlations in disorders of hereditary endocrine neoplasia is important for clinical screening, genetic counseling, prognostication, surveillance, and surgical strategy, and may also provide clues about disease pathogenesis. Important genotype-phenotype correlations are recognized, for example, in pheochromocytoma/paraganglioma and multiple endocrine neoplasia type 2A. The presence of such correlations has been less clear in other familial endocrine disorders associated with primary hyperparathyroidism including multiple endocrine neoplasia type 1, and the hyperparathyroidism-jaw tumor syndrome (HPT-JT). Characteristic features of HPT-JT, apart from fibro-osseous jaw tumors and uterine lesions, include renal neoplasms, such as Wilms tumor and mixed epithelial and stromal tumor ("renal hamartomas"), and a high incidence of parathyroid cancer. Emerging evidence suggests two different genotype-phenotype correlations in HPT-JT based on the type of variant in the CDC73 tumor suppressor gene. Although multiple CDC73 genotypes can give rise to the Wilms tumor phenotype in HPT-JT, the development of mixed epithelial and stromal tumor of the kidney specifically correlates with the presence of a start-loss variant affecting the initiator methionine codon of parafibromin, the protein product encoded by CDC73. Furthermore, the risk of parathyroid cancer in HPT-JT also appears to correlate with genotype: CDC73 frameshift indel, splice-site, and stop-gain genotypes are associated with a greatly increased risk of parathyroid carcinoma compared to carriers of CDC73 missense and nonframeshift indel variants. The recognition of such genotype-phenotype correlations in HPT-JT may impact genetic counseling, patient care and disease surveillance.

Context Parathyroid cancer has been linked to germline mutations of the Cell Division Cycle 73 (CDC73) gene. However, carriers harboring cancer-associated germline CDC73 mutations may develop only parathyroid adenoma or no parathyroid disease. This incomplete penetrance indicates that additional genomic events are required for parathyroid tumorigenesis. Objective (1) Determine the status of the second CDC73 allele in parathyroid tumors harboring germline CDC73 mutations and (2) compare the genomic landscapes between parathyroid carcinomas and adenomas. Design Whole-exome and RNA sequencing of 12 parathyroid tumors harboring germline CDC73 mutations (6 adenomas and 6 carcinomas) and their matched normal tissues. Results All 12 parathyroid tumors had gained 1 somatic event predicted to cause a complete inactivation of the second CDC73 allele. Several distinctive genomic features were identified in parathyroid carcinomas compared to adenomas, including more single nucleotide variants bearing the C > G transversion and APOBEC deamination signatures, frequent mutations of the genes involved in the PI-3K/mTOR signaling, a greater number of copy number variations, and substantially more genes with altered expression. Parathyroid carcinomas also share some genomic features with adenomas. For instance, both have recurrent somatic mutations and copy number loss that impact the genes involved in T-cell receptor signaling and tumor antigen presentation, suggesting a shared strategy to evade immune surveillance. Conclusion Biallelic inactivation of CDC73 is essential for parathyroid tumorigenesis in carriers harboring germline mutations of this gene. Despite sharing some genomic features with adenomas, parathyroid carcinomas have more distinctive alterations in the genome, some of which may be critical for cancer formation.

Disclosure: Y.B. Omotosho: None. N.U. Vikram: None. E.C. Wright: None. R. Tora: None. V. Dola: None. W. Abbas: None. N. Biassou: None. T. Massie: None. L. Bliss: None. P. Chittiboina: None. L.S. Weinstein: None. W.F. Simonds: None. S. Jha: None. Background: Patients with Multiple Endocrine Neoplasia Type 1 (MEN1) are genetically predisposed to developing pituitary adenomas. However, there is no evidence to guide surveillance testing in this cohort. Functional pituitary adenomas (PAs) can be monitored through laboratory assessments, whereas non-functional PAs require imaging unless they grow large enough to cause hypopituitarism, visual impairment, or other neurological symptoms. The current expert consensus is to obtain a pituitary MRI every 3-5 years. This study aims to examine the natural history of MEN1-related pituitary adenomas, particularly non-functional ones, to inform surveillance strategies. Methods: In this longitudinal cohort study, we identified 320 patients with genetically confirmed disease and available findings from pituitary MRI. Statistical analysis was performed in R studio. A p-value <0.05 defined statistical significance. Results: Of the 320 patients, 161 were females (50.3%) and 159 males (49.7%). Mean age at diagnosis was 33 ± 16 years, and mean age at last follow up was 47± 16 years. 182/320 patients (57%) had PAs. 78/182 (43%) patients were diagnosed with PAs at the time of diagnosis of MEN1. There appeared to be equal prevalence of both functional and non-functional PAs with 87/182 (48%) patients having functional PAs [78/87 (90%) prolactinomas, 2/87 (2%) GH-secreting and 8/87 (9%) ACTH-secreting] and the remaining 95/182 (52%) patients having non-functional PAs. 21/95 (24%) patients with non-functional PAs needed an intervention (medical or surgical) during their follow-up. Patients with macroadenomas were more likely to need an intervention (17/21, 81%) than patients with microadenomas (4/74, 5%), p <0.0001. Of the 21 patients with non-functional PAs needing an intervention, 11/21 (52%) had associated biochemical abnormalities on pituitary function testing and 18/21 (86%) had associated symptoms. There was only one patient with no associated symptom or abnormalities on pituitary function testing. The cumulative incidence of patients with non-functional adenomas requiring an intervention was 6% (CI: 2-14%) by age 35 years. Spaghetti plot analysis of tumor volumes for non-functional PAs without any intervention demonstrated a flat curve indicating minimal annual growth. Discussion: We observed a similar frequency of functional and non-functional pituitary adenomas (PAs) in MEN1. The 24% intervention rate for non-functional adenomas in this cohort aligns with reports that 25-50% of sporadic non-functional PAs show tumor growth or visual field deterioration. Notably, 20/21 cases of non-functional PAs requiring intervention were associated with abnormalities in pituitary function tests or reported symptoms. This finding suggests that surveillance imaging for MEN1-related PAs can be used sparingly, with greater reliance on symptom history and pituitary function testing. Presentation: Saturday, July 12, 2025

BACKGROUNDAmong patients with multiple endocrine neoplasia type 1 (MEN1), 80% develop duodenopancreatic neuroendocrine tumors (dpNETs), of whom 15%-25% die of metastasis. There is a need to identify biomarkers to predict aggressive disease. MEN1 genotype affords an attractive possibility as a biomarker, as it remains constant during life. Currently, patients are clinically diagnosed with MEN1 by the presence of ≥2 primary endocrine tumors (pituitary, parathyroid, and pancreas) or ≥1 primary endocrine tumor with a positive family history. From 10% to 30% of patients diagnosed clinically with MEN1 have no pathogenic germline MEN1 variants.METHODSThis was a retrospective study of 162 index patients or probands with genotype-positive and 47 with genotype-negative MEN1 enrolled from 1977 to 2022.RESULTSCompared with patients with genotype-negative disease, patients with genotype-positive disease were younger at diagnosis and had an increased frequency of recurrent parathyroid tumors, dpNETs, and angiofibromas or collagenomas. We propose a weighted scoring system to diagnose genotype-positive MEN1 based on clinical characteristics. No evidence of MEN1 mosaicism was seen in 30 tumors from 17 patients with genotype-negative MEN1. Patients with germline MEN1 variants in exons 2 and 3 had a reduced risk of distant metastases.CONCLUSIONThe clinical course of genotype-negative MEN1 is distinct from genotype-positive disease, raising uncertainty about the benefits of lifetime surveillance in patients with genotype-negative disease. MEN1 mosaicism is rare.TRIAL REGISTRATION ClinicalTrials.gov NCT04969926FUNDINGIntramural Research Program of National Institute of Diabetes and Digestive and Kidney Diseases, NIH (ZIA DK043006-46).

Abstract Disclosure: R. Tora: None. L. Canaff: None. J. Welch: None. L. Bliss: None. L.S. Weinstein: None. W.F. Simonds: None. S.K. Agarwal: None. J. Blau: None. D. Goltzman: None. S. Jha: None. Familial Hypocalciuric Hypercalcemia (FHH) is characterized by hypercalcemia and low urinary calcium excretion from birth and its diagnosis is confirmed by the presence of a pathogenic germline heterozygous variant in CaSR, AP2S1, or GNA11. Establishing the diagnosis is important as it prevents unnecessary parathyroidectomies as surgery is not curative. We identified patients with germline variants in CaSR, AP2S1, or GNA11 seen at our institute and performed a retrospective review of available clinical parameters. 43 patients (31 kindreds) with 28 unique CaSR variants (15 pathogenic, 13 variants of uncertain significance [VUS]) and one pathogenic AP2S1 variant were identified. Median age at diagnosis was 35 [IQR: 25 - 39] years, with the youngest patient diagnosed at 4.5 months. Median serum calcium was 10.70 [10.25 - 11.00] mg/dL (ref: 8.4 - 10.2) with a median PTH of 51.7 [35.8 - 74.0] pg/mL (ref: 15 - 65). The median fractional excretion of calcium (FECa) was 1.00 [0.54 - 1.40] while median serum magnesium was 2.30 [2.19 - 2.43] mg/dL (ref: 1.6 - 2.6). 5/43 (12%) patients developed kidney stones and 6/43 (14%) men ≤ 50 years and premenopausal women developed osteoporosis with median age at diagnosis of 38 [28.50 - 45.75] years and no alternate underlying secondary cause. Longitudinal follow-up available on 9/43 patients with median duration of 14.4 ± 4.5 years showed no significant changes in serum and urine biochemistries. 23/43 (53%) patients had undergone failed parathyroidectomy prior to diagnosis, of which 20/23 (87%) had multiple glands removed including one who became hypoparathyroid. Functional characterization was performed for 8/13 CaSR VUS (p.D217G, p.C546Y, p.F563S, p.C694Y, p.A880P, p.E109Q, p.D382N, and p.A880S) in HEK293 cells by examining intracellular Ca2+ and ERK/MAPK responses to extracellular Ca2+ using NFAT-Luc and SRE-Luc constructs, respectively. Compared to the wild type (WT) receptor, p.D217G, p.C546Y, p.F563S, and p.C694Y showed less of the cell-membrane-localized mature glycosylated species in Western blots and a significant rightward shift in their concentration-response curve in both SRE- and NFAT-Luc assays. p.A880P showed a significant rightward shift in its concentration-response curve, while p.E109Q, p.D382N, and p.A880S showed no differences on Western blot or concentration-response curves as compared to WT. Further work to characterize the remaining variants (p.T14A, p.T609M, p.V268_P278del, p.G36R, and p.F589V) is ongoing. We conclude that the diagnosis of FHH is frequently missed and that patients with the disease may rarely develop target organ damage. Presentation: 6/2/2024

The dorsal root ganglion (DRG) and trigeminal ganglion (TG) contain cell bodies of the peripheral sensory neurons that transmit pain signals from different parts of body to the central nervous system. Peripheral neuropathy and trigeminal neuralgia are common painful conditions that can be caused by pathologies affecting these nerves. Current clinical treatment of these conditions often relies on anticonvulsant drugs with significant neurological side effects. Lack of effective treatments of these conditions highlights the need for better therapeutic approaches. GNB5 encodes the protein Gβ5, a divergent member of the G protein β family, that binds with members (RGS6, 7, 9 and 11) of the R7 subfamily of the regulators of G signaling (R7-RGS) to form obligate Gβ5/R7-RGS complexes. The Gβ5/R7-RGS complex proteins are expressed primarily in neurons including those in the DRG and TG. They function as GTPase-Activating Proteins (GAP) to dampen signaling downstream of Gi/o-coupled receptors. Studies in our lab demonstrated that Adv-Cre+/−; Gnb5fl/fl mice lacking Gnb5 in sensory neurons have significantly reduced mechanical, thermal and chemical nociception. However, RGS7-Cre+/−; Gnb5fl/fl mice lacking Gnb5 in Rgs7 expressing neurons exhibited only diminished mechanical nociception. Additionally, treatment with GABA-B receptor antagonist 2- hydroxysaclofen abolished the inhibition of mechanical nociception in both Advillin- Cre+/-; Gnb5fl/fl and Rgs7-Cre+/-; Gnb5fl/fl mice, implicating the involvement of GABA-B receptor signaling in Gβ5/Rgs7-associated mechanical nociception. To further understand the cellular and molecular mechanisms of Gβ5/R7-RGS complex-mediated nociception, we analyzed and compared the expression profiles of the Gβ5/R7-RGS genes in DRG and TG through bioinformatic analysis of publicly available scRNAseq datasets and in situ hybridization of selected genes using RNAscope technology. We found high levels of Gnb5 expression across all sensory neuron cell types while the expressions of members of R7-RGS subfamily showed distinctive patterns among these neuron cell types. Single cell clustering analysis using known neuronal markers revealed that Rgs7 and Rgs11 were highly expressed in majority of neuron types, while Rgs6 and Rgs9 were represented in smaller, more distinct clusters. These results suggest that particular members of R7-RGS gene family might play distinct roles in different types of nociception, a finding that warrants further investigation into the individual mechanisms of each member of this gene family in pain transmission. NIDDK Intramural Research Program ZIA DK043304-29. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

A 51-year-old woman with a history of primary hyperparathyroidism (PHPT) with prior parathyroidectomy, osteoporosis, and learning disability was referred for hypercalcemia discovered after a fall. Family history was negative for PHPT, pituitary, enteropancreatic neuroendocrine, or jaw tumors. Dysmorphic facies, multiple cutaneous melanocytic nevi, café au lait macules, long fingers, and scoliosis were observed. Laboratory evaluation showed an elevated parathyroid hormone (PTH) level, hypercalcemia, and hypophosphatemia, all consistent with PHPT. Preoperative imaging revealed a right inferior candidate parathyroid lesion. The patient underwent right inferior parathyroidectomy with normalization of PTH, calcium, and phosphorus. Genetic testing showed a likely pathogenic de novo heterozygous germline missense variant p.R764W in the ZFX gene that encodes a zinc-finger transcription factor previously shown to harbor somatic missense variants in a subset of sporadic parathyroid tumors. Germline variants in ZFX have been reported in patients with an X-linked intellectual disability syndrome with an increased risk for congenital anomalies and PHPT. Further research may determine if genetic testing for ZFX could be of potential benefit for patients with PHPT and developmental anomalies, even in the absence of a family history of parathyroid disease.

Disease-associated variants identified from genome-wide association studies (GWASs) frequently map to non-coding areas of the genome such as introns and intergenic regions. An exclusive reliance on gene-agnostic methods of genomic investigation could limit the identification of relevant genes associated with polygenic diseases such as Alzheimer disease (AD). To overcome such potential restriction, we developed a gene-constrained analytical method that considers only moderate- and high-risk variants that affect gene coding sequences. We report here the application of this approach to publicly available datasets containing 181,388 individuals without and with AD and the resulting identification of 660 genes potentially linked to the higher AD prevalence among Africans/African Americans. By integration with transcriptome analysis of 23 brain regions from 2,728 AD case-control samples, we concentrated on nine genes that potentially enhance the risk of AD: AACS, GNB5, GNS, HIPK3, MED13, SHC2, SLC22A5, VPS35, and ZNF398. GNB5, the fifth member of the heterotrimeric G protein beta family encoding Gβ5, is primarily expressed in neurons and is essential for normal neuronal development in mouse brain. Homozygous or compound heterozygous loss of function of GNB5 in humans has previously been associated with a syndrome of developmental delay, cognitive impairment, and cardiac arrhythmia. In validation experiments, we confirmed that Gnb5 heterozygosity enhanced the formation of both amyloid plaques and neurofibrillary tangles in the brains of AD model mice. These results suggest that gene-constrained analysis can complement the power of GWASs in the identification of AD-associated genes and may be more broadly applicable to other polygenic diseases.

Abstract Disclosure: Y. Li: None. W.F. Simonds: None. H. Chen: None. Introduction: Parathyroid cancer is responsible for ∼1% of primary hyperparathyroidism. The hereditary form of this malignancy has been linked to germline mutations of the CDC73 gene. We previously reported that only the germline CDC73 mutations causing a significant impact on the function/expression of its encoded protein are associated with parathyroid carcinomas. On the other hand, these germline mutations may lead to only parathyroid adenomas or no parathyroid disease, suggesting incomplete penetrance. This observation raises the question of what additional genomic events are required for parathyroid tumorigenesis in carriers with germline CDC73 mutations. Methods: Twelve patients harboring heterozygous germline CDC73 mutations were included in this study. Whole exome sequencing was performed in all 12 parathyroid tumors (6 adenomas and 6 carcinomas) and the paired normal tissues. RNA sequencing was successfully performed in three of each parathyroid carcinomas, adenomas, and normal glands. The sequencing raw data were processed using the CCBR-Pipeliner. EnrichR, Gene Set Enrichment Analysis, and CIBERSORT were used for the downstream analyses. Results: All parathyroid carcinomas and adenomas had gained one somatic event predicted to cause a complete inactivation of the second CDC73 allele. Several distinctive genomic features were identified in parathyroid carcinomas compared to adenomas, including more single nucleotide variants bearing the signature of APOBEC deamination, frequent mutations among the genes involved in the PI-3K/mTOR signaling, and substantially more copy number variations and differentially expressed genes. Parathyroid carcinomas also share some genomic features with adenomas. For instance, both tumors have frequent somatic mutations and copy number loss that impact the genes related to T-cell receptor signaling and tumor antigen presentation, suggesting a shared strategy to evade immune surveillance. Consistent with these findings, an in silico estimation of immune cell composition in tumors found an absence of CD8+ T-cells in parathyroid adenomas and carcinomas. Conclusion: Our study provides evidence that biallelic inactivation of CDC73 is essential for parathyroid tumorigenesis in carriers with germline mutations of this gene. Despite sharing some genomic features with adenomas, parathyroid carcinomas have more distinctive alterations in the genome, some of which may be critical for cancer formation. Presentation: 6/2/2024

Calcium homeostasis is maintained by the actions of the parathyroid glands, which release parathyroid hormone into the systemic circulation as necessary to maintain the serum calcium concentration within a tight physiologic range. Excessive secretion of parathyroid hormone from one or more neoplastic parathyroid glands, however, causes the metabolic disease primary hyperparathyroidism (HPT) typically associated with hypercalcemia. Although the majority of cases of HPT are sporadic, it can present in the context of a familial syndrome. Mutations in the tumor suppressor genes discovered by the study of such families are now recognized to be pathogenic for many sporadic parathyroid tumors. Inherited and somatic mutations of proto-oncogenes causing parathyroid neoplasia are also known. Future investigation of somatic changes in parathyroid tumor DNA and the study of kindreds with HPT yet lacking germline mutation in the set of genes known to predispose to HPT represent two avenues likely to unmask additional novel genes relevant to parathyroid neoplasia.

Abstract Multiple studies have shown that approximately 50-70% of patients with MEN1 die of causes directly related to MEN1 particularly gastroenteropancreatic (GEP) neuroendocrine tumors (NETs). While non-functional GEP-NETs are the most common in the general population, gastrinomas (40%) are the most common functional GEP-NETs in patients with MEN1. c-MET is a proto-oncogene that encodes for c-MET, a tyrosine kinase receptor which promotes tumor cell motility, proliferation, survival, invasion, and metastasis. Studies in patients with sporadic gastrinomas and pancreatic NETs (PNETs) have shown that c-MET expression correlates with decreased survival. While c-MET inhibitors are currently in various stages of investigation for treatment of carcinoids and sporadic PNETs, data regarding their efficacy in patients with MEN1-related GEP NETs is lacking. The majority of trials in patients with GEP-NETs exclude or do not report the number of patients with MEN1. Importantly, somatic MEN1 mutations are observed in 20-40% of sporadic NETs (gastrinomas, PNETs, lung NETs, etc.) but correlation of cMET expression with the presence of somatic or germline MEN1 mutations has not been reported. We sought to investigate the expression of c-MET in tumor tissue from germline MEN1 patients with metastatic GEP-NETs. Methods We identified subjects with a germline positive MEN1 mutation and pathologically confirmed distant metastasis who had a follow-up visit between 2018-2020. Of these, we selected subjects with available tissue specimens (including either multiple organ sources or different tumor types). Where available, we identified specimens from multiple source or tumor types. Immunohistochemistry (IHC) to detect c-MET was performed with anti-MET (Cell Signaling) using the DAKO IHC kit (Agilent). IHC slides were imaged and observed to score the level of c-MET staining (-, 1+ to 5+). A score of 3+ or higher was considered consistent with overexpression. We investigated if age at initial GEP-NET presentation, tumor type, tissue source, tumor grade, total number of surgeries for GEP-NET, number of sites of distant metastasis and disease status from overall GEP-NET burden over the preceding 12 months (stable/progressive) predicted c-MET expression. Results Eight subjects with available tissue specimens were identified, of which six had tissue from multiple organs while five had tissue from multiple tumor types. Six subjects (75%) showed increased expression of c-MET in one or more tumor specimen(s). The frequency of c-MET overexpression varied with tumor types – carcinoids (n=2/2; 100%), gastrinomas (n=3/5; 60%) and non-functional tumors (n=3/6; 50%). c-MET expression also varied among different tumors in the same patient. Tumor tissue from liver (n=2/2), duodenum (n=3/4), stomach (n=1/1), ovary (n=1/1), pancreas (n= 1/5), and lymph nodes (n=1/3), all showed over-expression of c-MET. No clear predictors of c-MET overexpression emerged. Conclusion Our finding suggests a role for c-MET expression in personalizing therapy for patients with MEN1-related NETs with distant metastases. Presentation: Sunday, June 12, 2022 12:30 p.m. - 2:30 p.m., Sunday, June 12, 2022 12:48 p.m. - 12:53 p.m.

CONTEXT:Hyperparathyroidism-jaw tumor (HPT-JT) syndrome is a heritable form of primary hyperparathyroidism caused by germline inactivating mutations in CDC73 encoding parafibromin and is associated with an increased risk of parathyroid cancer. There is little evidence to guide the management of patients with the disease. OBJECTIVE:(1) Characterize the natural history of HPT-JT, (2) correlate genotype and histology of parathyroid tumors with parafibromin immunostaining, (3) understand molecular changes downstream to CDC73 loss. DESIGN:Retrospective study of patients with HPT-JT syndrome (genetically confirmed or affected first-degree relatives). Independent review of uterine tumor from 2 patients and staining for parafibromin on parathyroid tumors from 19 patients (13 adenomas, 6 carcinomas) was performed. RNA-sequencing was performed in 21 parathyroid samples (8 HPT-JT-related adenomas, 6 HPT-JT-related carcinomas, and 7 sporadic carcinomas with wild-type CDC73). RESULTS:We identified 68 patients from 29 kindreds with HPT-JT with median age at last follow-up of 39 [interquartile range, 29-53] years. A total of 55/68 (81%) developed primary hyperparathyroidism; 17/55 (31%) had parathyroid carcinoma. Twelve of 32 (38%) females developed uterine tumors. Of the 11 patients who had surgical resection for uterine tumors, 12/24 (50%) tumors were rare mixed epithelial mesenchymal polypoid lesions. Four of 68 patients (6%) developed solid kidney tumors; 3/4 had a CDC73 variant at p.M1 residue. Parafibromin staining of parathyroid tumors did not correlate with tumor histology or genotype. RNA-sequencing showed a significant association of HPT-JT-related parathyroid tumors with transmembrane receptor protein tyrosine kinase signaling pathway, mesodermal commitment pathway, and cell-cell adhesion. CONCLUSIONS:Multiple, recurrent atypical adenomyomatous uterine polyps appear to be enriched in women with HPT-JT and appear characteristic of the disease. Patients with CDC73 variants at p.M1 residue appear predisposed to kidney tumors. CLINICAL TRIAL NUMBER:NCT04969926.

Context:Autologous implantation of parathyroid tissue is frequently utilized after parathyroidectomy in patients with heritable forms of primary hyperparathyroidism (PHPT). Data on long-term functional outcome of these grafts is sparse.Objective:To investigate long-term outcomes of parathyroid autografts.Methods:Retrospective study of patients with PHPT who underwent parathyroid autografts from 1991 to 2020.Results:We identified 115 patients with PHPT who underwent 135 parathyroid autografts. Median follow-up duration since graft was 10 (4-20) years. Of the 111 grafts with known functional outcome, 54 (49%) were fully functional, 13 (12%) partially functional, and 44 (40%) nonfunctional at last follow-up. Age at time of graft, thymectomy prior to autograft, graft type (delayed vs immediate), or duration of cryopreservation did not predict functional outcome. There were 45 (83%) post-graft PHPT recurrences among 54 fully functional grafts at a median duration of 8 (4-15) years after grafting. Surgery was performed in 42/45 recurrences, but cure was attained in 18/42 (43%) only. Twelve of 18 (67%) recurrences were graft-related while remaining 6 (33%) had a neck or mediastinal source. Median time to recurrence was 16 (11-25) years in neck or mediastinal source vs 7 (2-13) years in graft-related recurrences. Median parathyroid hormone (PTH) gradient was significantly higher at 23 (20-27) in graft-related recurrence vs 1.3 (1.2-2.5) in neck or mediastinal source (P = .03).Conclusions:Post-graft recurrence of PHPT occurs frequently within the first decade after graft and is challenging to localize. Time to recurrence after graft is significantly shorter and PTH gradient higher for graft-related recurrence. Clinical Trial Number: NCT04969926.