Multiple Endocrine Neoplasia Type 1 (MEN1) 5'UTR Deletion, in MEN1 Family, Decreases Menin Expression

Beyond MEN1, When to Think About MEN4? Retrospective Study on 5600 Patients in the French Population and Literature Review

CONTEXT

Germline CDKN1B variants predispose patients to multiple endocrine neoplasia type 4 (MEN4), a rare MEN1-like syndrome, with <100 reported cases since its discovery in 2006. Although CDKN1B mutations are frequently suggested to explain cases of genetically negative MEN1, the prevalence and phenotype of MEN4 patients is poorly known, and genetic counseling is unclear.

OBJECTIVE

To evaluate the prevalence of MEN4 in MEN1-suspected patients and characterize the phenotype of MEN4 patients.

DESIGN

Retrospective observational nationwide study. Narrative review of literature and variant class reassessment.

PATIENTS

We included all adult patients with class 3/4/5 CDKN1B variants identified by the laboratories from the French Oncogenetic Network on Neuroendocrine Tumors network between 2015 and 2022 through germline genetic testing for MEN1 suspicion. After class reassessment, we compared the phenotype of symptomatic patients with class 4/5 CDKN1B variants (ie, with genetically confirmed MEN4 diagnosis) in our series and in literature with 66 matched MEN1 patients from the UMD-MEN1 database.

RESULTS

From 5600 MEN1-suspected patients analyzed, 4 with class 4/5 CDKN1B variant were found (0.07%). They presented with multiple duodenal NET, primary hyperparathyroidism (PHPT) and adrenal nodule, isolated PHPT, PHPT, and pancreatic neuroendocrine tumor. We listed 29 patients with CDKN1B class 4/5 variants from the literature. Compared with matched MEN1 patients, MEN4 patients presented lower NET incidence and older age at PHPT diagnosis.

CONCLUSION

The prevalence of MEN4 is low. PHPT and pituitary adenoma represent the main associated lesions, NETs are rare. Our results suggest a milder and later phenotype than in MEN1. Our observations will help to improve genetic counseling and management of MEN4 families.

Genetics of hereditary forms of primary hyperparathyroidism

Primary hyperparathyroidism (PHPT), a relatively common disorder characterized by hypercalcemia with raised or inappropriately normal serum parathyroid hormone (PTH) concentrations, may occur as part of a hereditary syndromic disorder or as a non-syndromic disease. The associated syndromic disorders include multiple endocrine neoplasia types 1-5 (MEN1-5) and hyperparathyroidism with jaw tumor (HPT-JT) syndromes, and the non-syndromic forms include familial hypocalciuric hypercalcemia types 1-3 (FHH1-3), familial isolated hyperparathyroidism (FIHP), and neonatal severe hyperparathyroidism (NS-HPT). Such hereditary forms may occur in > 10% of patients with PHPT, and their recognition is important for implementation of gene-specific screening protocols and investigations for other associated tumors. Syndromic PHPT tends to be multifocal and multiglandular with most patients requiring parathyroidectomy with the aim of limiting end-organ damage associated with hypercalcemia, particularly osteoporosis, nephrolithiasis, and renal failure. Some patients with non-syndromic PHPT may have mutations of the MEN1 gene or the calcium-sensing receptor (CASR), whose loss of function mutations usually cause FHH1, a disorder associated with mild hypercalcemia and may follow a benign clinical course. Measurement of the urinary calcium-to-creatinine ratio clearance (UCCR) may help to distinguish patients with FHH from those with PHPT, as the majority of FHH patients have low urinary calcium excretion (UCCR < 0.01). Once genetic testing confirms a hereditary cause of PHPT, further genetic testing can be offered to the patients' relatives and subsequent screening can be carried out in these affected family members, which prevents inappropriate testing in normal individuals.

[Plasma miRNA expression in patients with genetically confirmed multiple endocrine neoplasia type 1 syndrome and its phenocopies]

BACKGROUND

MEN-1 is a rare autosomal dominant disease caused by mutations in MEN1 gene encoding the menin protein. This syndrome is characterized by the occurrence of parathyroid tumors, gastroenteropancreatic neuroendocrine tumors, pituitary adenomas, as well as other endocrine and non-endocrine tumors. If a patient with the MEN-1 phenotype carry no mutations in the MEN1 gene, the condition considers a phenocopy of syndrome (phMEN1). The possible cause of this changes could be changes in epigenetic regulation, particularly in microRNA expression that might affect menin signaling pathways.

AIM

to identify differently expressed circulating miRNAs in plasma in patients with genetically confirmed MEN-1 syndrome, its phenocopies and healthy controls.

MATERIALS AND METHODS

single-center, case-control study was conducted. We assessed plasma microRNA expression in patients with genetically confirmed MEN-1 (gMEN1), phMEN1 and healthy controls. Morning plasma samples were collected from fasting patients and stored at -80°C. Total RNA isolation was performed using miRNeasy Mini Kit with QIAcube. The libraries were prepared by the QIAseq miRNA Library Kit following the manufacturer. Circulating miRNA sequencing was done on Illumina NextSeq 500 (Illumina). Subsequent data processing was performed using the DESeq2 bioinformatics algorithm.

RESULTS

we enrolled 21 consecutive patients with gMEN1 and 11 patients with phMEN1, along with 12 gender matched controls. Median age of gMEN1 was 38,0 [34,0; 41,0]; in phMEN1 - 59,0 [51,0; 60,0]; control - 59,5 [51,5; 62,5]. The gMEN1 group differed in age (p<0.01) but not gender (р=0.739) or BMI (р=0.116) compared to phMEN1 and controls group, the last two groups did not differ by these parameters (p>0.05). 25 microRNA were differently expressed in groups gMEN1 and phMEN1 (21 upregulated microRNAs, 4 - downregulated). Comparison of samples from the phMEN-1 group and relatively healthy controls revealed 10 differently expressed microRNAs: 5 - upregulated; 5 - downregulated. In the gMEN-1 and control groups, 26 differently expressed microRNAs were found: 24 - upregulated; 2 - downregulated. The miRNAs most differing in expression among the groups were selected for further validation by RT-qPCR (in the groups of gMEN1 vs phMEN1 - miR-3613-5p, miR-335-5p, miR-32-5p, miR-425-3p, miR-25-5p, miR-576-5p, miR-215-5p, miR-30a-3p, miR-141-3p, miR-760, miR-501-3p; gMEN1 vs control - miR-1976, miR-144-5p miR-532-3p, miR-375; as well as in phMEN1 vs control - miR-944, miR-191-5p, miR-98-5p).

CONCLUSION

In a pilot study, we detected microRNAs that may be expressed differently between patients with gMEN-1 and phMEN-1. The results need to be validated using different measurement method with larger sample size.

Genetics of monogenic disorders of calcium and bone metabolism

Disorders of calcium homeostasis are the most frequent metabolic bone and mineral disease encountered by endocrinologists. These disorders usually manifest as primary hyperparathyroidism (PHPT) or hypoparathyroidism (HP), which have a monogenic aetiology in 5%-10% of cases, and may occur as an isolated endocrinopathy, or as part of a complex syndrome. The recognition and diagnosis of these disorders is important to facilitate the most appropriate management of the patient, with regard to both the calcium-related phenotype and any associated clinical features, and also to allow the identification of other family members who may be at risk of disease. Genetic testing forms an important tool in the investigation of PHPT and HP patients and is usually reserved for those deemed to be an increased risk of a monogenic disorder. However, identifying those suitable for testing requires a thorough clinical evaluation of the patient, as well as an understanding of the diversity of relevant phenotypes and their genetic basis. This review aims to provide an overview of the genetic basis of monogenic metabolic bone and mineral disorders, primarily focusing on those associated with abnormal calcium homeostasis, and aims to provide a practical guide to the implementation of genetic testing in the clinic.

miR-3156-5p is downregulated in serum of MEN1 patients and regulates expression of MORF4L2

Multiple endocrine neoplasia type 1 (MEN1), caused by mutations in the MEN1 gene encoding menin, is an autosomal dominant disorder characterised by the combined occurrence of parathyroid, pituitary and pancreatic neuroendocrine tumours (NETs). Development of these tumours is associated with wide variations in their severity, order and ages (from <5 to >80 years), requiring life-long screening. To improve tumour surveillance and quality of life, better circulating biomarkers, particularly for pancreatic NETs that are associated with higher mortality, are required. We, therefore, examined the expression of circulating miRNA in the serum of MEN1 patients. Initial profiling analysis followed by qRT-PCR validation studies identified miR-3156-5p to be significantly downregulated (-1.3 to 5.8-fold, P < 0.05-0.0005) in nine MEN1 patients, compared to matched unaffected relatives. MEN1 knock-down experiments in BON-1 human pancreatic NET cells resulted in reduced MEN1 (49%, P < 0.05), menin (54%, P < 0.05) and miR-3156-5p expression (20%, P < 0.005), compared to control-treated cells, suggesting that miR-3156-5p downregulation is a consequence of loss of MEN1 expression. In silico analysis identified mortality factor 4-like 2 (MOR4FL2) as a potential target of miR-3156-5p, and in vitro functional studies in BON-1 cells transfected with either miR-3156-5p mimic or inhibitors showed that the miR-3156-5p mimic significantly reduced MORF4L2 protein expression (46%, P < 0.005), while miR-3156-5p inhibitor significantly increased MORF4L2 expression (1.5-fold, P < 0.05), compared to control-treated cells, thereby confirming that miR-3156-5p regulates MORF4L2 expression. Thus, the inverse relationship between miR-3156-5p and MORF4L2 expression represents a potential serum biomarker that could facilitate the detection of NET occurrence in MEN1 patients.

MEN4, the MEN1 Mimicker: A Case Series of three Phenotypically Heterogenous Patients With Unique CDKN1B Mutations

CONTEXT

Germline CDKN1B pathogenic variants result in multiple endocrine neoplasia type 4 (MEN4), an autosomal dominant hereditary tumor syndrome variably associated with primary hyperparathyroidism, pituitary adenoma, and duodenopancreatic neuroendocrine tumors.

OBJECTIVE

To report the phenotype of 3 unrelated cases each with a unique germline CDKN1B variant (of which 2 are novel) and compare these cases with those described in the current literature.

DESIGN/METHODS

Three case studies, including clinical presentation, germline, and tumor genetic analysis and family history.

SETTING

Two tertiary University Hospitals in Sydney, New South Wales, and 1 tertiary University Hospital in Canberra, Australian Capital Territory, Australia.

OUTCOME

Phenotype of the 3 cases and their kindred; molecular analysis and tumor p27kip1 immunohistochemistry.

RESULTS

Family A: The proband developed multiglandular primary hyperparathyroidism, a microprolactinoma and a multifocal nonfunctioning duodenopancreatic neuroendocrine tumor. Family B: The proband was diagnosed with primary hyperparathyroidism from a single parathyroid adenoma. Family C: The proband was diagnosed with a nonfunctioning pituitary microadenoma and ectopic Cushing's syndrome from an atypical thymic carcinoid tumor. Germline sequencing in each patient identified a unique variant in CDKN1B, 2 of which are novel (c.179G > A, p.Trp60*; c.475G > A, p.Asp159Asn) and 1 previously reported (c.374_375delCT, p.Ser125*).

CONCLUSIONS

Germline CDKN1B pathogenic variants cause the syndrome MEN4. The phenotype resulting from the 3 pathogenic variants described in this series highlights the heterogenous nature of this syndrome, ranging from isolated primary hyperparathyroidism to the full spectrum of endocrine manifestations. We report the first described cases of a prolactinoma and an atypical thymic carcinoid tumor in MEN4.

Hereditary Primary Hyperparathyroidism

Primary hyperparathyroidism (PHPT) is a commonly encountered clinical problem and occurs as part of an inherited disorder in ∼10% of patients. Several features may alert the clinician to the possibility of a hereditary PHPT disorder (eg, young age of disease onset) whilst establishing any relevant family history is essential to the clinical evaluation and will help inform the diagnosis. Genetic testing should be offered to patients at risk of a hereditary PHPT disorder, as this may improve management and allow the identification and investigation of other family members who may also be at risk of disease.

[Morphological characteristics of pituitary adenomas in the phenocopy of multiple endocrine neoplasia type 1]

BACKGROUND

Multiple endocrine neoplasia type 1 (MEN 1) is a rare autosomal dominant disorder caused by mutations in the MEN1 gene, which encodes the menin protein. If a patient has the MEN 1 phenotype in the absence of mutations in the MEN1 gene, the condition is classified as a phenocopy of this syndrome. Although significant progress has been made in understanding the function of menin, its role in the oncogenesis of the endocrine glands is still being elucidated. Due to its key role in physiological and pathological processes, the assessment of the menin expression can provide valuable information.

AIM

to determine whether there are any differences in the expression of menin in the pituitary adenomas (PA) in patients with phenocopy of MEN 1 (phMEN 1) and genetically confirmed MEN 1 (gMEN 1) compared with their sporadic forms.

MATERIALS AND METHODS

immunohistochemical assessment of the menin expression was carried out in PA of patients with gMEN 1, phMEN 1 and sporadic acromegaly (SA), surgically treated in 2008-2020. IHC was performed using antibodies to menin, PRL, GH, ACTH, FSH, TSH, Pit-1, T-box, ERA on previously prepared histological section.

RESULTS

The study included 35 samples of PA: gMEN 1 - 9 samples, phMEN 1 - 12 (somatotropinomas + PHPT); CA - 14  samples. The patients were comparable by gender, adenoma size, and drug intake. The gMEN  1 group differed from phMEN 1 and SA by age (p = 0.0005). In patients with gMEN 1, the expression of menin varied from no staining (5/9) to intense cytoplasm staining. Cytoplasmic expression of menin was mainly present (11/12) in the phMEN 1. In the SA group, there was no staining in 1 case; nuclear expression was detected in 6/14 cases. The phMEN  1 group showed significantly higher cytoplasmic expression of menin than the gMEN  1 group (p = 0.006). The gMEN 1 group also differed from the SA group (p = 0.012). There were no statistically significant differences between the phMEN 1 and SA groups (p = 0.049).

CONCLUSION

It was revealed that the menin expression, in general, is retained in phMEN 1 and SA groups, although with different localization in the cell structure (nucleus and / or cytoplasm). At the same time, the expression of menin varies greatly in patients with gMEN 1. According to the data obtained, it can be assumed that the pathogenesis of PA in phMEN 1 and SA may have similarities; however, there could be factors contributing to the appearance of several tumors of the endocrine glands in one person with phMEN 1. To understand this process, it is necessary to further study the genes associated with MEN 1, epigenetic factors, signaling pathways in which menin is involved.