Multiple endocrine neoplasia 2 in Cyprus: evidence for a founder effect

Genetic diagnosis of endocrine disorders in Cyprus through the Cyprus Institute of Neurology and Genetics: an ENDO-ERN Reference Center

The report covers the current and past activities of the department Molecular Genetics-Function and Therapy (MGFT) at the Cyprus Institute of Neurology and Genetics (CING), an affiliated Reference Center for the European Reference Network on Rare Endocrine Conditions (Endo-ERN).The presented data is the outcome of > 15 years long standing collaboration between MGFT and endocrine specialists from the local government hospitals and the private sector. Up-to-date > 2000 genetic tests have been performed for the diagnosis of inherited rare endocrine disorders. The major clinical entities included Congenital Adrenal Hyperplasia (CAH) due to pathogenic variants in CYP21A2 gene and Multiple Endocrine Neoplasia (MEN) type 2 due to pathogenic variants in the RET proto-oncogene. Other rare and novel pathogenic variants in ANOS1, WDR11, FGFR1, RNF216, and CHD7 genes were also found in patients with Congenital Hypogonadotropic Hypogonadism. Interestingly, a few patients with Disorders of Sexual Differentiation (DSD) shared rare pathogenic variants in the SRD5A2, HSD17B3 and HSD3B2 while patients with Glucose and Insulin Homeostasis carried theirs in GCK and HNF1A genes. Lastly, MGFT over the last few years has established an esteemed diagnostic and research program on premature puberty with emphasis on the implication of MKRN3 gene on the onset of the disease and the identification of other prognosis biomarkers.As an Endo-ERN member MGFT department belongs to this large European network and holds the same humanistic ideals which aim toward the improvements of health care for patients with rare endocrine conditions in respect to improved and faster diagnosis.

Applications of genomic research in pediatric endocrine diseases

Recent advances in molecular genetics have advanced our understanding of the molecular mechanisms involved in pediatric endocrine disorders and now play a major role in mainstream medical practice. The spectrum of endocrine genetic disorders has 2 extremes: Mendelian and polygenic. Mendelian or monogenic diseases are caused by rare variants of a single gene, each of which exerts a strong effect on disease risk. Polygenic diseases or common traits are caused by the combined effects of multiple genetic variants in conjunction with environmental and lifestyle factors. Testing for a single gene is preferable if the disease is phenotypically and/or geneically homogeneous. Next-generation sequencing (NGS) can be applied to phenotypically and genetically heterogeneous conditions. Genome-wide association studies (GWASs) have examined genetic variants across the entire genome in a large number of individuals who have been matched for population ancestry and assessed for a disease or trait of interest. Common endocrine diseases or traits, such as type 2 diabetes mellitus, obesity, height, and pubertal timing, result from the combined effects of multiple variants in various genes that are frequently found in the general population, each of which contributes a small individual effect. Isolated founder mutations can result from a true founder effect or an extreme reduction in population size. Studies of founder mutations offer powerful advantages for efficiently localizing the genes that underlie Mendelian disorders. The Korean population has settled in the Korean peninsula for thousands of years, and several recurrent mutations have been identified as founder mutations. The application of molecular technology has increased our understanding of endocrine diseases, which have impacted on the practice of pediatric endocrinology related to diagnosis and genetic counseling. This review focuses on the application of genomic research to pediatric endocrine diseases using GWASs and NGS technology for diagnosis and treatment.

Clinical characteristics of a large familial cohort with Medullary thyroid cancer and germline Cys618Arg RET mutation in an Israeli multicenter study

Objective

To determine genealogical, clinical and pathological characteristics of a cohort with Cys618Arg mutation from an Israeli multicenter MTC study.

Methods

Retrospective database analysis examining RET mutations and comparing Cys618Arg and Cys634Arg/Thr/Tyr subgroups.

Results

Genetic testing was performed in 131/275 MTC patients (47.6%). RET mutations were found in 50/131 (38.2%), including Cys618Arg (28/50 cases,56%), and Cys634Arg/Thr/Tyr (15/50,30%). Through genealogical study, 31 MTC patients were found descendants of one family of Jewish Moroccan descent, accounting for 27/28 patients with documented Cys618Arg mutation and 4 patients without available genetic testing. Familial Cys618Arg cases (n=31) and Cys634Arg/Thr/Tyr cases (n=15, from 6 families) were compared. Although surgical age was similar (25.7 vs 31.3 years, p=0.19), the Cys618Arg group had smaller tumors (8.9mm vs 18.5mm, p=0.004) and lower calcitonin levels (33.9 vs 84.5 X/ULN, p=0.03). Youngest ages at MTC diagnosis were 8 and 3 years in Cys618Arg and Cys634Arg/Thr/Tyr cohorts, respectively. Long-term outcome was similar between groups. The Cys618Arg cohort had lower rates of pheochromocytoma (6.5% vs 53.3%, p=0.001) and primary hyperparathyroidism (3.2% vs 33.3%, p=0.01).

Conclusion

This is the first description of RET mutation distribution in Israel. Of 131 tested MTC patients, Cys618Arg was the predominant mutation. To the best of our knowledge, this is the largest cohort of Cys618Arg mutation described. For Cys618Arg and Cys634Arg/Thr/Tyr cohorts, MTC was diagnosed earlier than expected, likely due to familial genetic screening, and MTC outcomes were similar between groups. International studies are necessary to further characterize the clinical features of Cys618 mutations due to their relative rarity.

RET Proto-Oncogene Variants in Patients with Medullary Thyroid Carcinoma from the Mediterranean Basin: A Brief Report

Multiple endocrine neoplasia type 2 (MEN2) is an autosomal dominant (AD) condition with very high penetrance and expressivity. It is characterized into three clinical entities recognized as MEN2A, MEN2B, and familial medullary thyroid carcinoma (FMTC). In both MEN2A and MEN2B, there is a manifestation of multicentric tumor formation in the major organs such as the thyroid, parathyroid, and adrenal glands where the RET proto-oncogene is expressed. The FMTC form differs from MEN2A and MEN2B, since medullary thyroid carcinoma (MTC) is the only feature observed. In this present brief report, we demonstrate a collection of RET proto-oncogene genotype data from countries around the Mediterranean Basin with variable characteristics. As expected, a great extent of the Mediterranean RET proto-oncogene genotype data resemble the data reported globally. Most interestingly, higher frequencies are observed in the Mediterranean region for specific pathogenic RET variants as a result of local prevalence. The latter can be explained by founder effect phenomena. The Mediterranean epidemiological data that are presented herein are very important for domestic patients, their family members' evaluation, and ultimately their treatment.

Multiple endocrine neoplasia 2: an overview

This review article discusses the diagnosis and treatment of patients with multiple endocrine neoplasia type 2 (MEN2). The most common tumors associated with MEN2 are those of the parathyroid, thyroid, and adrenal glands. Additional manifestations include characteristic clinical phenotypes or features as described in the article. This review provides an overview of clinical manifestations, screening, diagnosis, treatment, and surveillance of patients with MEN2.

Pathogenic and Low-Frequency Variants in Children With Central Precocious Puberty

Background

Central precocious puberty (CPP) due to premature activation of GnRH secretion results in early epiphyseal fusion and to a significant compromise in the achieved final adult height. Currently, few genetic determinants of children with CPP have been described. In this translational study, rare sequence variants in MKRN3, DLK1, KISS1, and KISS1R genes were investigated in patients with CPP.

Methods

Fifty-four index girls and two index boys with CPP were first tested by Sanger sequencing for the MKRN3 gene. All children found negative (n = 44) for the MKRN3 gene were further investigated by whole exome sequencing (WES). In the latter analysis, the status of variants in genes known to be related with pubertal timing was compared with an in-house Cypriot control cohort (n = 43). The identified rare variants were initially examined by in silico computational algorithms and confirmed by Sanger sequencing. Additionally, a genetic network for the MKRN3 gene, mimicking a holistic regulatory depiction of the crosstalk between MKRN3 and other genes was designed.

Results

Three previously described pathogenic MKRN3 variants located in the coding region of the gene were identified in 12 index girls with CPP. The most prevalent pathogenic MKRN3 variant p.Gly312Asp was exclusively found among the Cypriot CPP cohort, indicating a founder effect phenomenon. Seven other CPP girls harbored rare likely pathogenic upstream variants in the MKRN3. Among the 44 CPP patients submitted to WES, nine rare DLK1 variants were identified in 11 girls, two rare KISS1 variants in six girls, and two rare MAGEL2 variants in five girls. Interestingly, the frequent variant rs10407968 (p.Gly8Ter) of the KISS1R gene appeared to be less frequent in the cohort of patients with CPP.

Conclusion

The results of the present study confirm the importance of the MKRN3-imprinted gene in genetics of CPP and its key role in pubertal timing. Overall, the results of the present study have emphasized the importance of an approach that aligns genetics and clinical aspects, which is necessary for the management and treatment of CPP.

Increasing incidence and survival of paediatric and adolescent thyroid cancer in Cyprus 1998-2017: A population-based study from the Cyprus Pediatric Oncology Registry

BACKGROUND

Paediatric and adolescent thyroid cancer incidence rates are increasing in many countries. We determined incidence rates, temporal trends and survival from thyroid cancer diagnosed in childhood and adolescence in Cyprus during 1998-2017.

METHODS

Patients aged 0-19 years, diagnosed with thyroid cancer in the Pediatric Oncology Registry of Cyprus were included. Crude incidence rates, age standardized rates, time trends and overall survival were analysed. Annual rates and temporal trends were calculated using Microsoft Excel 2016 and Joinpoint regression analysis.

RESULTS

Eighty-one cases (76.5 % female, 23.5 % male) were identified. The crude rates (per 100,000 persons) were for both sexes 2.00 (95 % CI 1.61, 2.49), females 3.15 (95 % CI 2.45, 4.03) and males 0.92 (95 % CI 0.58, 1.44). The annual percentage changes of crude and standardised rates were 7.5 % (p < 0.05) and 7.6 % (p < 0.05). The annual percentage changes of crude rates were for females 5.1 % (p = 0.1), males 8.4 % (p < 0.05) and 15-19-year-olds 7.6 % (p < 0.05). The female to male rate ratio was 3.42 (95 % CI 2.06, 5.74). Papillary thyroid carcinoma represented 86.4 % of all cases. There was only one case after previous cancer therapy. The rate ratio of 2nd (2008-2017) to 1st (1998-2007) periods for metastatic (regional) stages was 3.76 (95 % CI 1.74, 8.31). Survival until 2018 was 100 %.

CONCLUSION

This population-based study demonstrated that thyroid cancer incidence rates in 0-19-year-olds in Cyprus was among the world's highest. Increasing trends mainly affected males and females aged 15-19 years with papillary thyroid carcinoma, the dominant type. Cases after previous cancer therapy didn't contribute to increasing rates. The increase of metastatic cases suggests a true increase of thyroid cancer rather than overdiagnosis. Although prognosis is excellent with 100 % survival, the rising incidence rate is unexplained, indicating the need to identify causes.

Targeted therapies for RET-fusion cancer: Dilemmas and breakthrough

Genomic profiling has revolutionized treatment options for patients with oncogene-driven cancers, such as epidermal growth factor receptor (EGFR) mutant carcinoma. Rearranged during transfection (RET) rearrangement, as one of the main activated oncogenes, has been well studied and found to be involved in the malignant behavior of carcinogenesis, resulting in acquired resistance to EGFR tyrosine kinase inhibitors and inducing an intrinsic resistance to immunotherapy. Thus, targeted therapies have been investigated against RET arrangement cancers, including several multi-kinase inhibitors and selective RET inhibitors. However, modest efficacy, a relatively high rate of toxicity, and poor effectiveness against brain metastasis are common limitations of multi-targeted novel molecular inhibitors. A promising prospect was shown recently in selective RET inhibitors in several ongoing clinical trials. In this review, we reviewed the concurrent dilemmas of targeted therapies against RET arrangement cancer from preclinical and clinical studies and proposed several clinical considerations for clinical practice prospectively.

Twenty-Five Years Experience on RET Genetic Screening on Hereditary MTC: An Update on The Prevalence of Germline RET Mutations

BACKGROUND

Pathogenic germline mutations affecting the RET proto-oncogene underlie the development of hereditary medullary thyroid carcinoma (MTC). The aims of this study were to evaluate the prevalence of germline RET mutations in a large series of MTC, collected over the last 25 years, and to reappraise their clinical significance.

METHODS

We performed RET genetic screening in 2031 Italian subjects: patients who presented with sporadic (n = 1264) or hereditary (n = 117) MTC, plus 650 relatives.

RESULTS

A RET germline mutation was found in 115/117 (98.3%) hereditary and in 78/1264 (6.2%) apparently sporadic cases: in total, 42 distinct germline variants were found. The V804M mutation was the most prevalent in our cohort, especially in cases that presented as sporadic, while mutations affecting cysteine residues were the most frequent in the group of clinically hereditary cases. All M918T mutations were "de novo" and exclusively associated with MEN2B. Several variants of unknown significance (VUS) were also found.

CONCLUSIONS

a) RET genetic screening is informative in both hereditary and sporadic MTC; b) the prevalence of different mutations varies with V804M being the most frequent; c) the association genotype-phenotype is confirmed; d) by RET screening, some VUS can be found but their pathogenic role must be demonstrated before screening the family.

Long-term outcome after DNA-based prophylactic neck surgery in children at risk of hereditary medullary thyroid cancer

Advances in sequencing technology, providing unprecedented insights into cancer progression, have shifted the treatment paradigm towards precision medicine for hereditary medullary thyroid cancer (MTC), away from the 'one-size-fits-all' approach predicated on genetic risk alone. The DNA-based/biochemical concept, factoring serum calcitonin into the benefit-risk equation, optimizes biochemical cure while minimizing extent of prophylactic surgery and operative morbidity in children at risk. The transformative effect that has taking effect on medical practice has been impressive: Increasingly earlier molecular diagnosis and more limited prophylactic neck operations yielded excellent clinical outcomes at expert facilities 7-16 years postoperatively: biochemical cure rates approximating 100%; absence of residual structural disease or recurrence; and rarely any permanent operative morbidity. These excellent results, contingent on proper health care funding and pediatric surgical specialization, make a case for early prophylactic thyroidectomy in experienced hands once calcitonin serum levels exceed the upper normal limit of the assay in young gene carriers.

p.Ser891Ala RET gene mutations in medullary thyroid cancer: Phenotypical and genealogical characterization of 28 apparently unrelated kindreds and founder effect uncovering in Northern Italy

Applying genetic screening in medullary thyroid cancer (MTC) patients we identified an unexpectedly high frequency of c.2671T>G, p.Ser891Ala RET mutation carriers. Our aim was to: (a) deeply characterize the clinical expression of this mutation, (b) identify the presence of a founder effect in our region. Genetic analysis was performed in 251 relatives from 28 Ser891Ala kindreds, among 108 p.Ser891Ala asymptomatic carriers, 64 were submitted to thyroidectomy: mean age for 10 subjects presenting C-cells hyperplasia was 30.2 ± 13.7 years, raising to 37.9 ± 10.3 in 14 subjects with micro-MTC and to 55.0 ± 14.7 years in 39 subjects with MTC. Age-related progression across histopathological groups CCH/microMTC and MTC were statistically significant: genetic screening in Ser891Ala families could be safely postponed at the age of 14. To investigate the hypothesis of a common ancestor for Ser891Ala mutation we genotyped for 18 polymorphic microsatellite markers encompassing RET locus all subjects belonging to Ser891Ala families and we identified a founder effect, estimating the age of a common ancestor, dating back to 1493 AD. Ethnographic data collected in historical archives support laboratory results; the high prevalence of this mutation in our region could suggest the hypothesis of a population study to realize a preventive intervention in a rare neoplastic disease.

Association of polymorphisms of CYP11B2 gene -344C/T and ACE gene I/D with antihypertensive response to angiotensin receptor blockers in Chinese with hypertension

The aim of this study was to determine whether the polymorphism of aldosterone synthase (CYP11B2) -344C/T and angiotensin-converting enzyme (ACE) insertion/deletion (I/D) were associated with the response of blood pressure (BP) to telmisartan treatment. After a two-week single-blind placebo run-in period, 148 patients with mild-to-moderate primary hypertension received monotherapy of telmisartan with 80 mg/day and then were followed up for eight weeks. Polymorphisms of CYP11B2 -344C/T and ACE I/D gene were determined through polymerase chain reaction-restriction fragment polymorphism analysis. The relationship between these polymorphisms and changes in BP was monitored and evaluated after eight weeks of treatment. With respect tothe polymorphism of CYP11B2 -344C/T, the reduction in diastolic BP was significantly greater in patients carrying the C allele (CC+CT) compared with those carrying the TT genotype. There was no significant differences between ACE I/D polymorphism and BP reduction after treatment. We concluded that the aldosterone synthase -344C/T polymorphism was related to the antihypertensive treatment with telmisartan in hypertensive patients.

Incidence and prevalence of multiple endocrine neoplasia 2A in Denmark 1901-2014: a nationwide study

Background

The incidence and prevalence of multiple endocrine neoplasia 2A (MEN2A) have only been reported once in a nationwide setting. However, it is unclear whether the figures are representative of other populations, as the major component of the syndrome, hereditary medullary thyroid carcinoma (MTC), has been reported as rare in the same country. We conducted a nationwide retrospective cohort study of MEN2A in Denmark from 1901 to 2014, aiming to describe the incidence and prevalence.

Methods

This study included 250 unique MEN2A patients born or resident in Denmark before December 31, 2014. Patients were identified through the Danish REarranged during Transfection (RET) cohort, linkage of MEN2A pedigrees, the Danish MTC cohort, a nationwide collaboration of MEN2 centers, cross-checking of other relevant cohorts, and a systematic literature search.

Results

The incidence from 1971 to 2000 was 28 (95% CI: 21–37) per million live births per year. Incidence for the specific mutations or for the overall MEN2A group did not change significantly from 1901 to 2014 (P>0.05). Point prevalence at January 1, 2015, was 24 per million (95% CI: 20–28).

Conclusion

The incidence and prevalence of MEN2A in Denmark seem higher than those reported in other countries. This is likely explained by the Danish C611Y founder effect. Also, our data indicate no significant change in MEN2A incidence during the last century.