Prevalence of mutations in TSHR, GNAS, PRKAR1A and RAS genes in a large series of toxic thyroid adenomas from Galicia, an iodine-deficient area in NW Spain

Molecular Pathology of Thyroid Tumors: Essential Points to Comprehend Regarding the Latest WHO Classification

In 2022, the new WHO Classification of Endocrine and Neuroendocrine Tumors, Fifth Edition (beta version) (WHO 5th), was published. Large-scale genomic analyses such as The Cancer Genome Atlas (TCGA) have revealed the importance of understanding the molecular genetics of thyroid tumors. Consequently, the WHO 5th was fundamentally revised, resulting in a systematic classification based on the cell of origin of tumors and their clinical risk. This paper outlines the following critical points of the WHO 5th. 1. Genetic mutations in follicular cell-derived neoplasms (FDNs) highlight the role of mutations in the MAP kinase pathway, including RET, RAS, and BRAF, as drivers of carcinogenesis. Differentiated thyroid cancers such as follicular thyroid carcinoma (FTC) and papillary thyroid carcinoma (PTC) have specific genetic alterations that correlate with morphological classifications: RAS-like tumors (RLTs) and BRAF p.V600E-like tumors (BLTs), respectively. 2. The framework for benign lesions has been revised. The WHO 5th introduces a new category: "developmental abnormalities". Benign FDNs comprise "thyroid follicular nodular disease", follicular thyroid adenoma (FTA), FTA with papillary architecture, and oncocytic adenoma (OA). "Hürthle cell adenoma/carcinoma" is renamed oncocytic adenoma/carcinoma of the thyroid (OA/OCA), which can be distinguished from FTA/FTC by its unique genetic background. 3. Low-risk tumors include NIFTP, TT-UMP, and HTT, and they have an extremely low malignant potential or an uncertain malignant potential. 4. PTC histological variants are reclassified as "subtypes" in the WHO 5th. 5. The concept of high-grade carcinomas is introduced, encompassing poorly differentiated thyroid carcinoma (PDTC), differentiated high-grade thyroid carcinoma (DHGTC), and high-grade medullary thyroid carcinoma (MTC). 6. Squamous cell carcinoma is included in anaplastic thyroid carcinoma (ATC) in the WHO 5th due to their shared genetic and prognostic features. 7. Other miscellaneous tumors are categorized as salivary-gland-type carcinomas of the thyroid, thyroid tumors of uncertain histogenesis, thymic tumors within the thyroid, and embryonal thyroid neoplasms. The WHO 5th thus emphasizes the importance of classifying tumors based on both genetic abnormalities and histomorphology. This approach aids in achieving accurate pathological diagnosis and facilitates the early selection of appropriate treatment options, including molecular targeted therapies.

Image-guided Thermal Ablation as a Promising Approach to Both Nontoxic and Toxic Autonomously Functioning Thyroid Nodules

RATIONALE AND OBJECTIVES

Although thermal ablation has been recommended as an alternative therapy option for autonomously functioning thyroid nodules (AFTN), current clinical evidence mainly focuses on toxic AFTN. This study aims to evaluate and compare the efficacy and safety of thermal ablation (percutaneous radiofrequency ablation or microwave ablation) in treating nontoxic and toxic AFTN.

MATERIALS AND METHODS

AFTN patients who received a single session of thermal ablation with a follow-up period ≥12 months were recruited. Changes in nodule volume and thyroid function, and complications were evaluated. Technical efficacy was defined as the maintenance or restoration of euthyroidism with a volume reduction rate (VRR) ≥80% at the last follow-up.

RESULTS

In total, 51 AFTN patients (age: 43.8±13.9 years, female: 88.2%) with a median follow-up period of 18.0 (12.0-24.0) months were included, where 31 were nontoxic (nontoxic group), and 20 were toxic (toxic group) before ablation. The median VRR was 96.3% (80.1%-98.5%) and 88.3% (78.3%-96.2%) in the nontoxic and toxic groups, respectively, and the respective euthyroidism rates were 93.5% (29/31, 2 evolved to toxic) and 75.0% (15/20, 5 remained toxic). The corresponding technical efficacy was 77.4% (24/31) and 55.0% (11/20, p=0.126). Except for one case of stress-induced cardiomyopathy in the toxic group, no permanent hypothyroidism or other major complications occurred in both groups.

CONCLUSION

Image-guided thermal ablation is efficacious and safe in treating AFTN, both nontoxic and toxic. Recognition of nontoxic AFTN would be helpful for treatment, efficacy evaluation, and follow-up.

A GNAS Gene Mutation's Independent Expression in the Growth of Colorectal Cancer: A Systematic Review and Meta-Analysis

Globally, colorectal carcinoma CRC is the third most common cancer and the third most common reason for cancer-associated mortality in both genders. The GNAS mutations are significantly linked with poor prognosis and failed treatment outcomes in CRC. A systematic review and meta-analysis of multiple studies executed following Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) criteria and registered with PROSPERO (registration number: CRD42021256452). The initial search includes a total of 271 publications; however, only 30 studies that merit the eligibility criteria were eventually chosen. Data analysis via OpenMeta Analyst and comprehensive meta-analysis 3.0 (CMA 3.0) software were used to investigate the prevalence of GNAS gene mutation among CRC patients. The meta-analysis consisted of 10,689 participants with most being males 6068/10,689 (56.8%). Overall, prevalence of GNAS mutations was 4.8% (95% CI: 3.1−7.3) with I2 = 94.39% and (p < 0.001). In 11/30 studies, the frequency of GNAS gene mutations was majorly in codons R201C [40.7% (95% CI: 29.2−53.2%)] and in codon R201H [39.7% (95% CI = 27.1−53.8)]. Overall prevalence of GNAS mutations was highest among the male gender: 53.9% (95% CI: 48.2−59.5%: I2 = 94.00%, (p < 0.001), tumour location (colon): 50.5% (95% CI: 33.2−67.6%: I2 = 97.93%, (p < 0.001), tumour grade (Well): 57.5% (95% CI: 32.4−79.2%: I2 = 98.10%, (p < 0.001) and tumour late stage: 67.9% (95% CI: 49.7−84.3%: I2 = 98.%, (p < 0.001). When stratified according to study location, a higher prevalence was observed in Japan (26.8%) while Italy has the lowest (0.4%). Overall prevalence of GNAS gene mutations was 4.8% with codons R201C and R201H being the most mutated, and the results conformed with numerous published studies on GNAS mutation.

TSHRV656F Activating Variant of the Thyroid Stimulating Hormone Receptor Gene in Neonatal Onset Hyperthyroidism: A Case Review

An activating variant of the thyroid stimulating hormone receptor (TSHR) gene is one of the rare causes of neonatal hyperthyroidism. This disorder may occur as a result of an autosomal dominant inheritance or sporadically through de novo variation. Here we present a case of neonatal onset congenital non-autoimmune hyperthyroidism (NAH) with a sporadic germline activating TSHRV656F variant. A female infant with tachycardia, who was transferred due to hyperthyroidism in the first week of life, displayed no other symptoms or signs. The patient’s mother did not have Graves’ disease, and TSHR stimulating antibodies were not present in the mother or baby. Imaging showed thyroid gland hyperplasia and left ventricular hypertrophy, the patient was subsequently put on methimazole treatment. After six months undergoing treatment, a heterozygous p.Val656Phe (V656F) (c.1966G>T) variant was detected on exon 10 of the TSHR gene. The variant was not identified in the mother and father, so the case was assumed to be sporadic. In conclusion, although the literature describes V656F variant as a somatic variant in children and adults with toxic thyroid nodule(s) that results in the structural activation of the TSH receptor, no previous cases of neonatal hyperthyroidism due to TSHRV656F variant have been reported. This study is the first case review that highlights the relationship between TSHRV656F variant and neonatal onset NAH.

Moderating Role of TSHR and PTPN22 Gene Polymorphisms in Effects of Excessive Fluoride on Thyroid: a School-Based Cross-Sectional Study

We aimed to investigate the relationship between the effects excessive of fluoride on thyroid health in children and the moderating role of thyroid stimulating hormone receptor (TSHR) or protein tyrosine phosphatase nonreceptor-22 (PTPN22) gene polymorphisms. Four hundred thirteen children (141 with dental fluorosis and 198 boys) were enrolled from both historical endemic and non-endemic areas of fluorosis in Tianjin, China. The fluoride exposure levels, thyroid health indicators, and TSHR (rs2268458) and PTPN22 (rs3765598) polymorphisms were examined. Multiple logistic models were applied to evaluate the relationship between dental fluorosis and thyroid abnormalities. Children over 9 year old with dental fluorosis have lower FT₄ and TGAb levels and thyroid volume and higher TPOAb levels (all P < 0.05). In overall participants, children with dental fluorosis were more likely to have thyroid antibody single positive issues (adjusted P = 0.039) and less likely to have a goiter according to age or body surface area (age or BSA) (adjusted P = 0.003); In the TSHR (rs2268458) SNP = CC/CT or PTPN22 (rs3765598) SNP = CC subgroup, dental fluorosis may cause thyroid antibody single positive (adjusted P = 0.036; adjusted P = 0.002); in the TSHR (rs2268458) SNP = TT or PTPN22 (rs3765598) SNP = CC subgroup, dental fluorosis may protect children from goiter (age or BSA) (adjusted P = 0.018; adjusted P = 0.013). Excessive fluoride may induce thyroid antibody single positive and reduce goiter in children. Heterogeneity exists in the relationship between excessive fluoride and thyroid antibody single positive or goiter issues across children carrying different TSHR (rs2268458) or PTPN22 (rs3765598) genotypes.

Gαs-Protein Kinase A (PKA) Pathway Signalopathies: The Emerging Genetic Landscape and Therapeutic Potential of Human Diseases Driven by Aberrant Gαs-PKA Signaling

Many of the fundamental concepts of signal transduction and kinase activity are attributed to the discovery and crystallization of cAMP-dependent protein kinase, or protein kinase A. PKA is one of the best-studied kinases in human biology, with emphasis in biochemistry and biophysics, all the way to metabolism, hormone action, and gene expression regulation. It is surprising, however, that our understanding of PKA's role in disease is largely underappreciated. Although genetic mutations in the PKA holoenzyme are known to cause diseases such as Carney complex, Cushing syndrome, and acrodysostosis, the story largely stops there. With the recent explosion of genomic medicine, we can finally appreciate the broader role of the Gαs-PKA pathway in disease, with contributions from aberrant functioning G proteins and G protein-coupled receptors, as well as multiple alterations in other pathway components and negative regulators. Together, these represent a broad family of diseases we term the Gαs-PKA pathway signalopathies. The Gαs-PKA pathway signalopathies encompass diseases caused by germline, postzygotic, and somatic mutations in the Gαs-PKA pathway, with largely endocrine and neoplastic phenotypes. Here, we present a signaling-centric review of Gαs-PKA-driven pathophysiology and integrate computational and structural analysis to identify mutational themes commonly exploited by the Gαs-PKA pathway signalopathies. Major mutational themes include hotspot activating mutations in Gαs, encoded by GNAS, and mutations that destabilize the PKA holoenzyme. With this review, we hope to incite further study and ultimately the development of new therapeutic strategies in the treatment of a wide range of human diseases. SIGNIFICANCE STATEMENT: Little recognition is given to the causative role of Gαs-PKA pathway dysregulation in disease, with effects ranging from infectious disease, endocrine syndromes, and many cancers, yet these disparate diseases can all be understood by common genetic themes and biochemical signaling connections. By highlighting these common pathogenic mechanisms and bridging multiple disciplines, important progress can be made toward therapeutic advances in treating Gαs-PKA pathway-driven disease.

Transcriptomic Signature of Human Embryonic Thyroid Reveals Transition From Differentiation to Functional Maturation

The human thyroid gland acquires a differentiation program as early as weeks 3-4 of embryonic development. The onset of functional differentiation, which manifests by the appearance of colloid in thyroid follicles, takes place during gestation weeks 10-11. By 12-13 weeks functional differentiation is accomplished and the thyroid is capable of producing thyroid hormones although at a low level. During maturation, thyroid hormones yield increases and physiological mechanisms of thyroid hormone synthesis regulation are established. In the present work we traced the process of thyroid functional differentiation and maturation in the course of human development by performing transcriptomic analysis of human thyroids covering the period of gestation weeks 7-11 and comparing it to adult human thyroid. We obtained specific transcriptomic signatures of embryonic and adult human thyroids by comparing them to non-thyroid tissues from human embryos and adults. We defined a non-TSH (thyroid stimulating hormone) dependent transition from differentiation to maturation of thyroid. The study also sought to shed light on possible factors that could replace TSH, which is absent in this window of gestational age, to trigger transition to the emergence of thyroid function. We propose a list of possible genes that may also be involved in abnormalities in thyroid differentiation and/or maturation, hence leading to congenital hypothyroidism. To our knowledge, this study represent the first transcriptomic analysis of human embryonic thyroid and its comparison to adult thyroid.

Familial neonatal nonautoimmune hyperthyroidism due to a gain-of-function (D619G) thyrotropin-receptor mutation

OBJECTIVES

Activating germline mutations of the thyroid-stimulating hormone receptor (TSHR) are responsible for a rare form of neonatal nonautoimmune hyperthyroidism (NAH). We report the first case of familial neonatal neonatal nonautoimmune associated with c.1856A>G (p.Asp619Gly) variant in the TSHR gene.

CASE PRESENTATION

We describe an eight-year-old African-American female presenting with neonatal NAH associated with an inherited heterozygous c.1856A>G (p.Asp619Gly) variant in the TSHR gene. This variant was previously described in one patient presenting with sporadic NAH in adolescence. Our patient was diagnosed with hyperthyroidism in the neonatal period. The mother had a history of hyperthyroidism and had thyroidectomy at the age of 4 years. The patient had goiter and elevated free thyroxine (FT4) and free triiodothyronine (FT3) levels that normalized with methimazole treatment; however, TSH level remained suppressed. Thyroid antibodies were negative. The patient also had bilateral exotropia, a trait shared by the mother and may represent a new association.

CONCLUSIONS

Familial neonatal NAH is associated with heterozygous c.1856A>G (p.Asp619Gly) variant of the TSHR gene.

Cytomorphologic features of thyroid disease in patients with DICER1 mutations: A report of cytology-histopathology correlation in 7 patients

BACKGROUND

Germline and somatic mutations of DICER1 have been identified in various types of neoplastic lesions, with germline DICER1 mutation being linked to autosomal dominant hereditary pleiotropic tumor syndrome (DICER1 syndrome). Patients with DICER1 syndrome are at increased risk of developing thyroid disease, including thyroid cancer. The goal of this study was to identify diagnostic cytologic features in thyroid fine-needle aspiration (FNA) samples from patients with DICER1 mutation.

METHODS

Cytology cases of thyroid FNA from 7 patients with DICER1 mutation were identified. Clinical, imaging, cytomorphologic, and molecular data were analyzed.

RESULTS

Cytologic preparations from reviewed cases showed thyroid lesions of follicular derivation with scant colloid, moderate cellularity, uniform follicular cells with round nuclei and inconspicuous nucleoli arranged in small crowded groups and microfollicles. Follicular neoplasm was diagnosed in 4 cases and follicular lesion of undetermined significance in 3 cases, based on the Bethesda System for Reporting Thyroid Cytopathology. Histopathological analysis of thyroid tissue confirmed neoplastic process in 6 out of 7 cases: follicular carcinoma (FC, 3 cases), papillary thyroid carcinoma (2 cases), poorly differentiated thyroid carcinoma (PDTC, 1 case). Genetic studies identified 3 different somatic variants of DICER1 gene, including transcript consequence c.5428G>T, which was detected in FC and PDTC (and has been described previously in multinodular goiter).

CONCLUSION

DICER1 mutation in all analyzed patients was identified as a result of thyroid FNA evaluation, emphasizing the critical role of FNA in the screening of patients with thyroid nodules, proper diagnosis of thyroid disease, and monitoring of patients with DICER1 mutation.

Pitfalls in Challenging Thyroid Tumors: Emphasis on Differential Diagnosis and Ancillary Biomarkers

Thyroid pathology encompasses a heterogenous group of clinicopathological entities including rare and diagnostically challenging neoplasms. The review is focused on morphological, immunohistochemical, and molecular features of rare thyroid neoplasms that can pose diagnostic problems. The tumors are organized based on growth patterns including thyroid neoplasms with predominantly papillary, follicular, solid, and spindle cell growth pattern, as well as neoplasms with distinct cytological characteristics. A special section is also dedicated to rare thyroid tumors with peculiar patterns including thyroid carcinoma with Ewing family tumor elements and intrathyroidal thymic-related neoplasms.

GNAS mutated thyroid carcinoma in a patient with Mc Cune Albright syndrome

Mc Cune-Albright syndrome (MAS) is a rare disorder defined by the triad of polyostotic fibrous dysplasia, “café au lait” skin hyperpigmentation and hyperfunctioning endocrinopathies, such as precocious puberty.

MAS is caused by an activating post zygotic somatic mutation of GNAS gene, coding for the alpha-subunit of the stimulatory G protein (Gsalpha). In endocrine tissues, this mutation results in overproduction of hormones and endocrine cell hyperfunction and proliferation.

Whereas the association of hyperthyroidism and thyroid adenomas is well known in MAS, the relation with thyroid carcinoma has rarely been observed.

We report the occurrence of a thyroid carcinoma in an 18-years old woman with MAS, revealed by subclinical hyperthyroidism detected during her systematic annual follow-up. Ultrasound and thyroid scintigraphy revealed the presence of a nodule in the right lobe. Pathology on hemithyroidectomy revealed an unexpected thyroid follicular carcinoma. Neoplastic thyroid cells harbored the GNAS R201C activating mutation. This observation suggests that MAS may predispose patients to thyroid carcinomas and supports the importance of thyroid assessment by physical examination, hormonal blood test and ultrasound, in the follow-up of patients with MAS. Because ultrasound diagnostic is challenging in MAS, needle puncture of palpable nodules should be advised.

The Thyrotropin Receptor Mutation Database Update

The thyrotropin receptor (TSHR) mutation database, consisting of all known TSHR mutations and their clinical characterizations, was established in 1999. The database contents are updated here with the same website (tsh-receptor-mutation-database.org). The new database contains 638 cases of TSHR mutations: 448 cases of gain of function mutations (7 novel mutations and 41 new cases for previously described mutations since its last update in 2012) and 190 cases of loss of function mutations (28 novel mutations and 31 new cases for previously described mutations since its last update in 2012). This database is continuously updated and allows for rapid validation of patient TSHR mutations causing hyper- or hypothyroidism or insensitivity to TSH.

Nonautoimmune Hyperthyroidism Caused by a Somatic Mosaic GNAS Mutation Involving Part of the Thyroid Gland

Nonautoimmune hyperthyroidism caused by activating mutations in the GNAS gene is a rare condition. In this study, we report a five-year-old girl diagnosed with nonautoimmune hyperthyroidism and tall stature harboring a somatic mosaic gain-of-function mutation in the GNAS gene (NM_080425.3: c.2530C>T;p.Arg844Cys previously reported as NM_000516.5:c.601C>T;p.Arg201Cys) and referred to thereafter as R201C, in three of four quadrants of the thyroid gland. Provision of a molecular diagnosis may avoid unnecessary complete ablation of the thyroid gland.

Partial thyrocyte-specific Gαs deficiency leads to rapid-onset hypothyroidism, hyperplasia, and papillary thyroid carcinoma-like lesions in mice

Thyroid function is controlled by thyroid-stimulating hormone (TSH), which binds to its G protein-coupled receptor [thyroid-stimulating hormone receptor (TSHR)] on thyrocytes. TSHR can potentially couple to all G protein families, but it mainly activates the Gs- and Gq/11-mediated signaling cascades. To date, there is a knowledge gap concerning the role of the individual G protein cascades in thyroid pathophysiology. Here, we demonstrate that the thyrocyte-specific deletion of Gs-protein α subunit (Gαs) in adult mice [tamoxifen-inducible Gs protein α subunit deficient (iTGαsKO) mice] rapidly impairs thyrocyte function and leads to hypothyroidism. Consequently, iTGαsKO mice show reduced food intake and activity. However, body weight and the amount of white adipose tissue were decreased only in male iTGαsKO mice. Unexpectedly, hyperplastic follicles and papillary thyroid cancer-like tumor lesions with increased proliferation and slightly increased phospho-ERK1/2 staining were found in iTGαsKO mice at an older age. These tumors developed from nonrecombined thyrocytes still expressing Gαs in the presence of highly elevated serum TSH. In summary, we report that partial thyrocyte-specific Gαs deletion leads to hypothyroidism but also to tumor development in thyrocytes with remaining Gαs expression. Thus, these mice are a novel model to elucidate the pathophysiological consequences of hypothyroidism and TSHR/Gs/cAMP-mediated tumorigenesis.-Patyra, K., Jaeschke, H., Löf, C., Jännäri, M., Ruohonen, S. T., Undeutsch, H., Khalil, M., Kero, A., Poutanen, M., Toppari, J., Chen, M., Weinstein, L. S., Paschke, R., Kero, J. Partial thyrocyte-specific Gαs deficiency leads to rapid-onset hypothyroidism, hyperplasia, and papillary thyroid carcinoma-like lesions in mice.

Clinical Significance of Thyroid-Stimulating Hormone Receptor Gene Mutations and/or Sodium-Iodine Symporter Gene Overexpression in Indeterminate Thyroid Fine Needle Biopsies

Objectives: To examine the prevalence of genetic alterations of thyroid-stimulating hormone receptor (TSHR) gene and sodium-iodine symporter (NIS) in a series of thyroid fine needle biopsy (FNB) specimens with indeterminate cytology, and to assess the correlation of the type of genetic changes with clinical features and follow-up results in the target thyroid nodule. Methods: Between February 2015 and September 2017, 388 consecutive FNBs with indeterminate cytology were evaluated for TSHR mutations and NIS gene overexpression using ThyroSeqV.2 next-generation sequencing (NGS) panel. Medical records were reviewed for target nodules. Results: Among 388 indeterminate FNBs, TSHR mutations and/or NIS overexpression were detected in 25 (6.4%) nodules. Ten nodules (2.6%) harbored TSHR mutations only, 7 nodules (1.8%) over-expressed NIS gene only, and 8 nodules (2.1%) had both alterations. The TSHR mutations were located between codons 281 and 640, with codon 453 being the most frequently affected. The allelic frequency of the mutated TSHR ranged from 6 to 36%. One nodule with NIS overexpression was simultaneously detected EIF1AX mutation and GNAS mutation. Nodules with TSHR mutations and/or NIS overexpression presented hyperfunctioning (n = 4), hypofunctioning (n = 5), and isofunctioning (n = 3) on the available thyroid scintigraphies. Eight cases accompanied with hyperthyroidism in which only 1 was caused by the target nodule. Evidence of co-existing autoimmune thyroid disease (AITD) and multinodular goiter were found in 52% and 52% of cases, respectively. Seven nodules underwent surgeries and all were benign on final pathology. None of 9 nodules with follow-up by ultrasound (3~33 mon, median 12 mon) showed grow in size. Conclusions: TSHR mutations and/or NIS overexpression can be detected in pre-operative FNB specimens using the NGS approach. These genetic alterations occurred in 6.4% thyroid nodules in this consecutive series with indeterminate cytology. They present not only in hyperfunctioning nodules but also in hypo- or iso-functional nodules, indicating their prevalence may be higher than previously expected. Co-existing AITD was common in cases with these molecular alterations. None of our patients with TSHR mutations and/or NIS overexpression manifested malignant outcomes. How to use these two molecular markers in thyroid FNBs to guide our clinical practice warrants further investigation.

Novel germline mutation (Leu512Met) in the thyrotropin receptor gene (TSHR) leading to sporadic non-autoimmune hyperthyroidism

BACKGROUND

Primary nonautoimmune hyperthyroidism is a rare cause of neonatal hyperthyroidism. This results from an activating mutation in the thyrotropin-receptor (TSHR). It can be inherited in an autosomal dominant manner or occur sporadically as a de novo mutation. Affected individuals display a wide phenotype from severe neonatal to mild subclinical hyperthyroidism. We describe a 6-month-old boy with a de novo mutation in the TSHR gene who presented with accelerated growth, enlarging head circumference, tremor and thyrotoxicosis.

METHODS

Genomic DNA from the patient's and parents' peripheral blood leukocytes was extracted. Exons 9 and 10 of the TSHR gene were amplified by PCR and sequenced.

RESULTS

Sequencing exon 10 of the TSHR gene revealed a novel heterozygous missense mutation substituting cytosine to adenine at nucleotide position 1534 in the patient's peripheral blood leukocytes. This leads to a substitution of leucine to methionine at amino acid position 512. The mutation was absent in the parents. In silico modeling by PolyPhen-2 and SIFT predicted the mutation to be deleterious.

CONCLUSIONS

The p.Leu512Met mutation (c.1534C>A) of the TSHR gene has not been previously described in germline or somatic mutations. This case presentation highlights the possibility of mild thyrotoxicosis in affected individuals and contributes to the understanding of sporadic non-autoimmune primary hyperthyroidism.

microRNA expression in autonomous thyroid adenomas: Correlation with mRNA regulation

The objective of the study was to identify the deregulated miRNA in autonomous adenoma and to correlate the data with mRNA regulation. Seven autonomous adenoma with adjacent healthy thyroid tissues were investigated. Twelve miRNAs were downregulated and one was upregulated in the tumors. Combining bioinformatic mRNA target prediction and microarray data on mRNA regulations allowed to identify mRNA targets of our deregulated miRNAs. A large enrichment in mRNA encoding proteins involved in extracellular matrix organization and different phosphodiesterases were identified among these putative targets. The direct interaction between miR-101-3p and miR-144-3p and PDE4D mRNA was experimentally validated. The global miRNA profiles were not greatly modified, confirming the definition of these tumors as minimal deviation tumors. These results support a role for miRNA in the regulation of extracellular matrix proteins and tissue remodeling occurring during tumor development, and in the important negative feedback of the cAMP pathway, which limits the consequences of its constitutive activation in these tumors.

Differential transcriptional and protein expression of thyroid-stimulating hormone receptor in ovarian carcinomas

OBJECTIVE

Thyroid-stimulating hormone (TSH) regulates normal thyroid function by binding to its receptor (thyroid-stimulating hormone receptor -TSHR) that is expressed at the surface of thyroid cells. Recently, it has been demonstrated that TSHR is abundantly expressed in several tissues apart from the thyroid, among them the normal ovarian surface epithelium. The role of TSHR expression outside the thyroid is not completely understood. The current study examines possible alterations of TSHR expression in ovarian carcinomas and its implication in ovarian carcinogenesis.

MATERIALS AND METHODS

Quantitative real-time polymerase chain reaction and immunohistochemistry analysis of TSHR expression were performed in 34 ovarian carcinoma specimens and 10 normal ovarian tissues (controls).

RESULTS

Significant reduction in TSHR messenger RNA (mRNA) expression was detected in ovarian carcinomas (mean [SD]: 0.518 [0.0934] vs normal, 49.4985 [89.1626]; P < 0.001, Mann-Whitney U test), whereas TSHR protein levels were significantly increased (percentage of positive cells: cancer, 73.55% [20.09%], vs normal, 54.54% [21.14%]; intensity: cancer, 2.52 [0.508], vs normal 1 [0]; P = 0.012, Mann-Whitney U test). No significant differences in TSHR mRNA were found according to history of thyroid disease.

CONCLUSIONS

Our study describes for the first time alterations in TSHR expression both at mRNA and protein levels in ovarian carcinomas. The discrepancy between the decreased levels of the TSHR mRNA and the increased protein expression has already been described in thyroid carcinomas and might be due to alterations in its degradation by the ubiquitin system or other unknown mechanisms. Further analysis could elucidate the role of these findings in ovarian carcinogenesis.

PTCH1 mutation is a frequent event in oesophageal basaloid squamous cell carcinoma

Basaloid squamous cell carcinoma (BSCC) is a rare and poorly differentiated variant of typical squamous cell carcinoma, and is characterised in part by activation of the Wnt signalling pathway. We previously demonstrated that constitutive activation of the Wnt signalling pathway by epigenetic silencing of secreted frizzled-related protein 4 (SFRP4) is observed in this tumour. Increasing evidence shows that the Wnt signalling pathway cross-talks with other developmental pathways, including the Hedgehog (HH) pathway. The HH pathway is stimulated by inactivating mutations of PTCH1, which have a well-described oncogenic role in basal cell carcinoma (BCC) of the skin. We employed polymerase chain reaction followed by direct sequencing to detect inactivating mutations of PTCH1 using archival tissue samples of 30 oesophageal BSCCs. The frequency of PTCH1 mutation was compared to that of Wnt component genes that we reported previously. We found PTCH1 mutations in 53.3% (16/30) of cases, revealing T1195S as a hotspot mutation. This frequency is quite high for cancers other than BCC of the skin, and PTCH1 mutations were almost mutually exclusive with mutations in APC, Axin1 and Axin2. Considering the fact that activation of Wnt signalling via down-regulation of APC and SFRP5 due to promoter methylation is observed in BCC of the skin, Wnt signalling activation in oesophageal BSCC might be a secondary effect of the PTCH1-inactivating mutations. These findings suggest that the HH and Wnt pathways coordinately contribute to tumourigenesis in oesophageal BSCC. Furthermore, this study provides a potential therapeutic application for HH pathway inhibitors in oesophageal BSCC with highly malignant potential.

GNAS mutations identify a set of right-sided, RAS mutant, villous colon cancers

The purpose of this study is to determine the genetic frequency of GNAS activating mutations in colorectal cancer and the corresponding pathology of GNAS mutant tumors. Oncogenic mutations in GNAS have been described in a number of neoplasms including those of the pituitary, kidney, pancreas, and, more recently, in colon cancer. To ascertain the frequency in colon cancer we employed a sensitive pyrosequencing platform for mutation detection of the R201C and R201H GNAS hotspots in tumor samples representing all clinical stages. We additionally assayed for KRAS and BRAF mutations as previous reports have shown that these often co-occur with activating GNAS mutations. Of the 428 colon tumors assayed, mutations in GNAS were present in 10 of the samples (2.3%), indicating this is a significant, albeit infrequent, mutation in colorectal tumors. Nine GNAS mutant tumors (90%) harbored concomitant activating mutations in either the KRAS or BRAF oncogene, which was significantly greater than the mutation frequency of these genes in the tumor population (56%, p<0.0305). All ten of the GNAS mutant tumors arose in the right (proximal) colon (p<0.007), and 7 of 8 reviewed cases exhibited a marked villous morphology. Taken together, these data indicate that GNAS mutant colon tumors commonly have synchronous mutations in KRAS or BRAF, are right-sided in location, and are associated with a villous morphology.

Identification of kinase fusion oncogenes in post-Chernobyl radiation-induced thyroid cancers

Exposure to ionizing radiation during childhood markedly increases the risk of developing papillary thyroid cancer. We examined tissues from 26 Ukrainian patients with thyroid cancer who were younger than 10 years of age and living in contaminated areas during the time of the Chernobyl nuclear reactor accident. We identified nonoverlapping somatic driver mutations in all 26 cases through candidate gene assays and next-generation RNA sequencing. We found that 22 tumors harbored fusion oncogenes that arose primarily through intrachromosomal rearrangements. Altogether, 23 of the oncogenic drivers identified in this cohort aberrantly activate MAPK signaling, including the 2 somatic rearrangements resulting in fusion of transcription factor ETS variant 6 (ETV6) with neurotrophic tyrosine kinase receptor, type 3 (NTRK3) and fusion of acylglycerol kinase (AGK) with BRAF. Two other tumors harbored distinct fusions leading to overexpression of the nuclear receptor PPARγ. Fusion oncogenes were less prevalent in tumors from a cohort of children with pediatric thyroid cancers that had not been exposed to radiation but were from the same geographical regions. Radiation-induced thyroid cancers provide a paradigm of tumorigenesis driven by fusion oncogenes that activate MAPK signaling or, less frequently, a PPARγ-driven transcriptional program.

GNAS-activating mutations define a rare subgroup of inflammatory liver tumors characterized by STAT3 activation

BACKGROUND & AIMS

Mosaic G-protein alpha-subunit (GNAS)-activating mutations are responsible for the McCune-Albright (MCA) syndrome. This oncogene that activates the adenylate cyclase is also mutated in various tumor types leading to the accumulation of cyclic-AMP. Identification of a hepatocellular adenoma (HCA) in two MCA patients led us to search for GNAS activation in benign and malignant hepatocellular carcinogenesis.

METHODS

GNAS mutations were screened by sequencing 164 HCA, 245 hepatocellular carcinoma (HCC), and 17 fibrolamellar carcinomas. Tumors were characterized by quantitative RT-PCR, gene mutation screening and pathological reviewing. The consequences of wild type and mutant GNAS expression were analyzed in hepatocellular cell lines.

RESULTS

A somatic GNAS-activating mutation was identified in 5 benign tumors and in 2 HCC. In benign tumors, GNAS mutations were exclusive from HNF1A, CTNNB1, and IL6ST mutations whereas one HCC demonstrated both CTNNB1 and GNAS mutations. Quantitative RT-PCR showed an activation of the IL-6 and interferon pathways in GNAS-mutated tumor tissues. Accordingly, pathological reviewing identified in GNAS-mutated tumors an inflammatory phenotype characterized by fibrosis and STAT3 activation. We further demonstrated in HCC cell lines that GNAS mutant expression induced inflammatory response and STAT3 activation.

CONCLUSIONS

We identified for the first time the association between two rare diseases, MCA syndrome and HCA occurrence, but also that somatic GNAS-activating mutations in sporadic benign and malignant liver tumors are characterized by an inflammatory phenotype. These results showed a cross-talk between cyclic-AMP and JAK/STAT pathways in liver tumors and they reinforce the role of STAT3 activation in liver tumorigenesis.

Two rare TSH receptor amino acid substitutions in toxic thyroid adenomas

Toxic adenoma and toxic multinodular goiter (TMNG) are common causes of hyperthyroidism in iodine-deficient regions, but they are relatively rare in iodine-sufficient regions, including Japan. Constitutive activating mutations of the thyroid stimulating hormone receptor (TSHR) gene and adenylate cyclase-stimulating G α protein (GNAS) gene are frequent in these thyrotoxic disorders. Here we report two cases of rare TSHR gene mutations in Japanese thyrotoxicosis patients. In Case 1, we observed multiple toxic nodules with thyrotoxicosis, and in Case 2, we detected a solitary toxic nodule in an 8-year-old girl. In both cases, ultrasonography showed thyroid nodules and scintigraphy revealed increased uptake. Total thyroidectomy was performed for Case 1 and a hemi-thyroidectomy was performed for Case 2. Genetic analysis of the resected tissues revealed an I568F mutation in Case 1 and a S281I mutation in the TSHR gene in Case 2. The I568F mutation was located in the second extracellular loop, and the S281I mutation was located in the N-terminal extracellular domain of the TSH receptor. In Case 1, the mutation was restricted to the largest nodule, and was not detected in other functioning nodules or non-nodule thyroid tissue. Bi-allelic expression of the TSHR gene was confirmed by reverse transcription-polymerase chain reaction in both tumors. Both the I568F and S281I mutations were studied previously in vitro, and were revealed to cause basal activation of the protein kinase A pathway. Case 1 represents the second reported case of an I568F mutation and Case 2 represents the third reported case of an S281I mutation.

Study on the relationship between TSHR gene and thyroid diseases

Thyroid stimulating hormone receptor (TSHR) is thought to play a critical role in the pathogenesis of certain thyroid diseases, including Graves' disease (GD), multinodular thyroid goiter (MTG), and Hashimoto's thyroiditis (HT). In order to understand whether single nucleotide polymorphisms in the TSHR gene contribute to thyroid diseases, we have conducted a case-control study in which, we examined 8 TSHR gene single-nucleotide polymorphisms in introns 1, 4, 5, 6 and exons 7 and 8, respectively, among patients with thyroid diseases. These included one family with GD (3 patients and 9 healthy members); 60 patients with familiar thyroid diseases (30 with GD, 20 with MTG, and 10 with HT patients), 48 sporadic patients with GD and 96 healthy control individuals. Direct sequencing of all 10 exons and part of introns of TSHR gene, in these patients as well as healthy controls revealed eight polymorphisms. A novel polymorphism in exon 8 AGA(Arg) → CGA(Arg). However, there were no significant differences between patients and controls in the incidence of these polymorphisms. These results suggest that the polymorphisms (polymorphism in intron 1 at 81 bp upstream of exon 2; polymorphism in intron 4 at 135 bp upstream of exon 5; polymorphism in intron 4 at 365 bp upstream of exon 5; polymorphism in intron 5 at 69 bp upstream of exon 6; means polymorphism in intron 6 at 13 bp downstream of exon 6; polymorphism in intron 6 at 187 bp upstream of exon 7; E7+16: polymorphism in 16 bp of exon 7; polymorphism in 40 bp of exon 8) of the TSHR gene may not contribute to the pathogenesis of thyroid diseases.

Shared sporadic and somatic thyrotropin receptor mutations display more active in vitro activities than familial thyrotropin receptor mutations

BACKGROUND

Germline thyrotropin receptor (TSHR) mutations are associated with sporadic congenital nonautoimmune hyperthyroidism and familial nonautoimmune hyperthyroidism. Somatic TSHR mutations are associated with toxic thyroid nodules (TTNs). The objective of the study was to define a relation of the clinical appearance and the in vitro activity (IVA) of the TSHR mutations described by several authors for these thyroid disorders.

METHODS

We analyzed the IVAs published as linear regression analysis (LRA) of the constitutive activity as a function of the TSHR expression and the basal cyclic adenosine monophosphate (cAMP) values to determine differences between exclusively somatic, exclusively familial, and shared sporadic and somatic TSHR-mutations. Further, we investigated correlations of the LRAs/basal cAMP values with clinical activity characteristics (CACs) of TTNs, such as largest diameter of the TTN and the age of the patient at thyroid surgery.

RESULTS

Shared sporadic and somatic mutations showed higher median LRA (14.5) and higher median basal cAMP values (fivefold) than exclusively familial mutations (6.1, p = 0.0002; 2.9-fold, p < 0.0001, respectively). Moreover, mutations shared between sporadic congenital nonautoimmune hyperthyroidism and toxic thyroid nodules (TTNs) showed higher median LRA/basal cAMP values (p < 0.0001) than exclusively somatic mutations in TTNs (5.1; 3.89-fold, respectively). Exclusively somatic mutations and exclusively familial mutations showed no significant difference in their median LRA values (p = 0.786) but a significant difference for basal cAMP values (p = 0.0006). The two examined CACs showed no correlation with the IVA characterized by LRA/basal cAMP values or with the presence or absence of a TSHR-mutation.

CONCLUSIONS

This systematic analysis of published constitutively activating TSHR-mutations, their CACs, and their IVA provides evidence for higher IVA of shared sporadic and somatic TSHR mutations as compared with familial TSHR mutations. CACs of somatic TSHR mutations in TTNs did not have a clear association with the IVA as characterized by LRA or basal cAMP values.

Identification and evaluation of constitutively active thyroid stimulating hormone receptor mutations

Thyroid stimulating hormone receptor (TSHR) is a guanine nucleotide-binding protein-coupled seven-transmembrane-domain receptor that controls the differentiation, growth, and function of the thyroid gland through stimulation of adenylyl cyclase and phospholipase C pathways. Thyroid stimulating hormone (TSH) is the main TSHR ligand, and unliganded receptor remains silent due to the interaction of its large extracellular domain with the extracellular loops of the serpentine. The TSHR gene is highly mutagenic and constitutively active mutations have been extensively described. Naturally occurring TSHR-activating mutations can affect any part of the receptor, but most activating mutations affect the serpentine region, and the majority of these are located in the third intracellular loop or transmembrane domain six. We describe several simple and relatively cheap methods used in our laboratory to study constitutive TSHR mutations that include (1) screening of TSHR gene mutations in paraffin-embedded thyroid tissue samples, (2) measurement of TSHR constitutive activity in vitro, (3) measurement of TSHR expression at cell surface by flow cytometry analysis, (4) TSH binding to TSHR, and (5) TSHR phosphorylation analysis.

A family with congenital hypothyroidism caused by a combination of loss-of-function mutations in the thyrotropin receptor and adenylate cyclase-stimulating G alpha-protein subunit genes

BACKGROUND

Resistance to thyrotropin (TSH) causes congenital hypothyroidism (CH). TSH receptor (TSHR) and adenylate cyclase-stimulating G alpha protein subunit (GNAS) loss-of-function mutations cause TSH resistance. We describe a family with TSH resistance and CH bearing a combination of inactivating mutations in TSHR and GNAS genes. We describe studies to determine the molecular mechanisms involved in TSH resistance in this family.

METHODS

DNA sequencing to identify TSHR and GNAS gene mutations was performed. In vitro effects of the mutations on cAMP production and TSH binding were investigated in COS7 cells. cAMP production was evaluated by transfecting a cAMP response element (CRE)-luciferase reporter with pSVL-TSHR and pSVK3-GNAS vectors. For binding studies, cells transfected with pSVL-TSHR vectors were incubated with iodine-125 bovine TSH ((125)IbTSH).

RESULTS

Family members with and without CH were heterozygous for the TSHR mutant p.E34K or the GNAS mutant c.750_751insA (=GNASMut). The propositus had CH and he was heterozygous for TSHR p.E34K; his mother, also heterozygous for TSHR p.E34K, did not have CH. The euthyroid propositus' wife was heterozygous for GNASMut. The propositus' two daughters had CH, one was heterozygous for GNASMut and the other a compound heterezygous for TSHR p.E34K and GNASMut. Albright's hereditary osteodystrophy phenotype was present in those with GNASMut mutation but only the daughters had pseudohypoparathyroidism type 1a. Cells transfected with TSHRE34K had lower TSH affinity and less CRE-luciferase response than cells transfected with TSHR wild-type (WT). Cells transfected with GNASMut did not stimulate CRE-luciferase activity, but when cells were transfected with GNASMut plus GNASWT, a similar response to GNASWT alone was observed. The combination of TSHRWT and GNASWT showed higher CRE-luciferase response than TSHRWT and TSHRE34K with either GNASWT or GNASWT plus GNASMut.

CONCLUSIONS

CH was caused by loss-of-function mutations in TSHR and/or GNAS. The absence of CH in the propositus' mother argues against a role for TSHR p.E34K being the only cause of CH. The minimal thyroidal phenotypic differences between the sisters with pseudohypoparathyroidism type 1a and TSH resistance, both heterozygous for GNAS c.750_751insA but only one bearing the TSHR p.E34K mutant, suggest that the main cause for CH was preferential expression of the mutated maternal GNAS allele in the thyroid gland.

Genetic hyperthyroidism: hyperthyroidism due to activating TSHR mutations

Three syndromes affecting the thyroid gland are described in the literature separately: familial nonautoimmune hyperthyroidism, sporadic congenital nonautoimmune hyperthyroidism, and autonomous adenomas. Recent studies have shown that these three syndromes are caused by similar activating mutations of the TSH receptor gene (TSHR), and that the consequences of these mutations on the physiology and gene expression of the thyroid are qualitatively, but not quantitatively, similar. The three syndromes and two suggested unrecognized variants are in fact facets of the same disease, genetic hyperthyroidism due to TSHR mutations, the expression of which depends on the intensity of activation, its timing, and on the number of affected cells.

The activating mutation R201C in GNAS promotes intestinal tumourigenesis in Apc(Min/+) mice through activation of Wnt and ERK1/2 MAPK pathways

Somatically acquired, activating mutations of GNAS, the gene encoding the stimulatory G-protein Gsα subunit, have been identified in kidney, thyroid, pituitary, leydig cell, adrenocortical and more recently, in colorectal tumours, suggesting that mutations such as R201C may be oncogenic in these tissues. To study the role of GNAS in intestinal tumourigenesis, we placed GNAS R201C under the control of the A33-antigen promoter (Gpa33), which is almost exclusively expressed in the intestines. The GNAS R201C mutation has been shown to result in the constitutive activation of Gsα and adenylate cyclase and to lead to the autonomous synthesis of cAMP. Gpa33^{tm1(GnasR201C)Wtsi/+} mice showed significantly elevated cAMP levels and a compensatory upregulation of cAMP-specific phosphodiesterases in the intestinal epithelium. GNAS R201C alone was not sufficient to induce tumourigenesis by 12 months but there was a significant increase in adenoma formation when Gpa33^{tm1(GnasR201C)Wtsi/+} mice were bred onto an Apc^Min/+ background. GNAS R201C expression was associated with elevated expression of Wnt and extracellular signal-regulated kinase 1/2 mitogen-activated protein kinase (ERK1/2 MAPK) pathway target genes, increased phosphorylation of ERK1/2 MAPK, and increased immunostaining for the proliferation marker Ki67. Furthermore, the effects of GNAS R201C on the Wnt pathway were additive to inactivation of Apc. Our data strongly suggest that activating mutations of GNAS cooperate with inactivation of APC and are likely to contribute to colorectal tumourigenesis.

Assessment of nodular goitre

Nodular goitres are enlargements of the thyroid gland. In the absence of thyroid dysfunction, autoimmune thyroid disease, thyroiditis and thyroid malignancy, they constitute an entity described as non-toxic nodular goitre, which occurs both endemically and sporadically. In the early phase of goitrogenesis, goitres are diffuse and, with time, such goitres tend to become nodular. Concomitantly, thyroid function often becomes autonomous, and therefore the patients gradually develop hyperthyroidism. Some non-toxic goitre patients have no symptoms at all, or just complaints of cosmetic disfigurement. In the diagnostic evaluation protocol, neck palpation and several imaging methods are available: ultrasonography (US), the new developed US elastography, scintigraphy, computed tomography (CT) scan and magnetic resonance imaging (MRI). Fine-needle aspiration biopsy (FNAB) provides the most direct and specific information about a thyroid nodule. Recently, a combination of cytology and molecular testing has shown significant improvement in the diagnostic accuracy and allowed for better prediction of malignancy in thyroid nodular disease.

Identification and functional characterization of two novel activating thyrotropin receptor mutants in toxic thyroid follicular adenomas

BACKGROUND

Two previously unreported thyrotropin (TSH) receptor mutations, A623F and I635V, were identified in toxic follicular thyroid adenoma specimens from two patients with hyperthyroidism. Our aim was to characterize both novel mutants in terms of the following: cAMP basal constitutive activity, cAMP response to TSH, plasma membrane expression levels, and TSH binding properties.

METHODS

We performed DNA extraction for TSHR gene sequencing. COS-7 cells were transiently transfected with wild-type and mutated TSH receptor constructs for determination of basal cAMP constitutive activity and dose-response accumulation of cAMP using recombinant human TSH. Flow cytometry analysis was performed to evaluate plasma membrane expression. Binding studies using bovine TSH as a ligand were performed to compare the affinities of wild-type and mutated TSH receptors for TSH.

RESULTS

Both mutants, A623F and I635V, had higher cAMP basal constitutive activities than the wild-type TSH receptor. A623F but not I635V showed lower plasma membrane expression than the wild-type receptor. IC50, an indirect measurement of ligand-receptor affinity, was lower in A623F and higher in I635V than in the wild-type TSH receptor, although no statistically significant differences were observed. No differences were observed in EC50 and although the absolute values of maximal stimulation achieved with both mutants were higher than the wild type, the differences did not achieve statistical significance.

CONCLUSIONS

A623F and I635V are two naturally occurring TSH receptor mutations that increase basal cAMP accumulation and consequently promote the development of toxic follicular thyroid adenoma. cAMP response to increasing TSH dose is retained by A623F and I635V mutated receptors and the maximal stimulation obtained is not different from that of the wild-type receptor. Substitution of alanine 623 by phenylalanine 623 at the third intracellular loop of the TSH receptor decreases its plasma membrane expression, indicating that alanine 623 is important in directing the TSH receptor to the cell surface or in down-regulating the constitutive receptor. By contrast, isoleucine 635, located in the sixth transmembrane domain, is important in regulating TSH receptor basal activity but does not modify its plasma membrane expression.

Prevalence of TSH receptor and Gsalpha mutations in 45 autonomously functioning thyroid nodules in Japan

Somatic mutations of the thyrotropin receptor (TSHR) gene and the gene encoding the alpha subunit of the stimulatory GTP-binding protein (Gsalpha) are the main cause for autonomously functioning thyroid nodules (AFTN) in iodine-deficient regions of the world. In iodine-sufficient regions, including Japan, the genetic relevance of AFTN is unclear. In a series of 45 Japanese subjects with AFTN, exons 9 and 10 of the TSHR and exons 7-10 of Gsalpha , where the activating mutations have been found, were analyzed using direct sequencing. We found 29 somatic mutations: 22 in the TSHR gene and 7 in the Gsalpha gene. The most frequent mutation in TSHR was Met453Thr (10 cases), followed by clustered residues from codons 630 through 633 on TSHR (7 cases). Mutations of Gsalpha were detected at codon 201 in 5 cases and at codon 227 in 2 cases. No patients had coexistent TSHR and Gsalpha mutations in the same nodule. All mutated residues but one, which was deleted at codon 403 on the TSHR gene, are constitutively active. The prevalences of a germline polymorphism of Asp727Glu on the TSHR gene and incidental papillary thyroid carcinoma in thyroid surgical specimens were similar to those reported in other studies. In the present study, more than half of the cases with AFTN had a somatic activating mutation either of the TSHR or Gsalpha gene, despite their high iodine intake.