Clinical and molecular characterisation of metastatic papillary thyroid cancer according to radioiodine therapy outcomes

PURPOSE

Radioiodine (RAI) therapy remains the gold-standard approach for distant metastatic differentiated thyroid cancer (TC). The main objective of our work was to identify the clinical and molecular markers that may help to predict RAI avidity and RAI therapy response of metastatic lesions in a cohort of papillary thyroid cancer (PTC) patients.

METHODS

We performed a retrospective analysis of 122 PTC patients submitted to RAI therapy due to distant metastatic disease. We also analysed, through next-generation sequencing, a custom panel of 78 genes and rearrangements, in a smaller cohort of 31 metastatic PTC, with complete follow-up, available RAI therapy data, and existing tumour sample at our centre.

RESULTS

The most frequent outcome after RAI therapy was progression of disease in 59.0% of cases (n = 71), with median estimate progression-free survival of 30 months. RAI avidity was associated with PTC subtype, age and stimulated thyroglobulin at first RAI therapy for metastatic disease. The most frequently altered genes in the cohort of 31 PTC patients' primary tumours were RAS isoforms (54.8%) and TERT promoter (TERTp) (51.6%). The presence of BRAF p.V600E or RET/PTC alterations was associated with lower avidity (p = 0.012). TERTp mutations were not associated with avidity (p = 1.000) but portended a tendency for a higher rate of progression (p = 0.063); similar results were obtained when RAS and TERTp mutations coexisted (p = 1.000 and p = 0.073, respectively).

CONCLUSIONS

Early identification of molecular markers in primary tumours may help to predict RAI therapy avidity, the response of metastatic lesions and to select the patients that may benefit the most from other systemic therapies.

CHEK2 germline variants identified in familial nonmedullary thyroid cancer lead to impaired protein structure and function

Approximately 5 to 15% of nonmedullary thyroid cancers (NMTC) present in a familial form (familial nonmedullary thyroid cancers [FNMTC]). The genetic basis of FNMTC remains largely unknown, representing a limitation for diagnostic and clinical management. Recently, germline mutations in DNA repair-related genes have been described in cases with thyroid cancer (TC), suggesting a role in FNMTC etiology. Here, two FNMTC families were studied, each with two members affected with TC. Ninety-four hereditary cancer predisposition genes were analyzed through next-generation sequencing, revealing two germline CHEK2 missense variants (c.962A > C, p.E321A and c.470T > C, p.I157T), which segregated with TC in each FNMTC family. p.E321A, located in the CHK2 protein kinase domain, is a rare variant, previously unreported in the literature. Conversely, p.I157T, located in CHK2 forkhead-associated domain, has been extensively described, having conflicting interpretations of pathogenicity. CHK2 proteins (WT and variants) were characterized using biophysical methods, molecular dynamics simulations, and immunohistochemistry. Overall, biophysical characterization of these CHK2 variants showed that they have compromised structural and conformational stability and impaired kinase activity, compared to the WT protein. CHK2 appears to aggregate into amyloid-like fibrils in vitro, which opens future perspectives toward positioning CHK2 in cancer pathophysiology. CHK2 variants exhibited higher propensity for this conformational change, also displaying higher expression in thyroid tumors. The present findings support the utility of complementary biophysical and in silico approaches toward understanding the impact of genetic variants in protein structure and function, improving the current knowledge on CHEK2 variants' role in FNMTC genetic basis, with prospective clinical translation.

Identification of Germline FOXE1 and Somatic MAPK Pathway Gene Alterations in Patients with Malignant Struma Ovarii, Cleft Palate and Thyroid Cancer

Germline variants in the FOXE1 transcription factor have been associated with thyroid ectopy, cleft palate (CP) and thyroid cancer (TC). Here, we aimed to clarify the role of FOXE1 in Portuguese families (F1 and F2) with members diagnosed with malignant struma ovarii (MSO), an ovarian teratoma with ectopic malignant thyroid tissue, papillary TC (PTC) and CP. Two rare germline heterozygous variants in the FOXE1 promoter were identified: F1) c.-522G>C, in the proband (MSO) and her mother (asymptomatic); F2) c.9C>T, in the proband (PTC), her sister and her mother (CP). Functional studies using rat normal thyroid (PCCL3) and human PTC (TPC-1) cells revealed that c.9C>T decreased FOXE1 promoter transcriptional activity in both cell models, while c.-522G>C led to opposing activities in the two models, when compared to the wild type. Immunohistochemistry and RT-qPCR analyses of patients' thyroid tumours revealed lower FOXE1 expression compared to adjacent normal and hyperplastic thyroid tissues. The patient with MSO also harboured a novel germline AXIN1 variant, presenting a loss of heterozygosity in its benign and malignant teratoma tissues and observable β-catenin cytoplasmic accumulation. The sequencing of the F1 (MSO) and F2 (PTC) probands' tumours unveiled somatic BRAF and HRAS variants, respectively. Germline FOXE1 and AXIN1 variants might have a role in thyroid ectopy and cleft palate, which, together with MAPK pathway activation, may contribute to tumours' malignant transformation.

CDK4 phosphorylation status and rational use for combining CDK4/6 and BRAF/MEK inhibition in advanced thyroid carcinomas

Background

CDK4/6 inhibitors (CDK4/6i) have been established as standard treatment against advanced Estrogen Receptor-positive breast cancers. These drugs are being tested against several cancers, including in combinations with other therapies. We identified the T172-phosphorylation of CDK4 as the step determining its activity, retinoblastoma protein (RB) inactivation, cell cycle commitment and sensitivity to CDK4/6i. Poorly differentiated (PDTC) and anaplastic (ATC) thyroid carcinomas, the latter considered one of the most lethal human malignancies, represent major clinical challenges. Several molecular evidence suggest that CDK4/6i could be considered for treating these advanced thyroid cancers.

Methods

We analyzed by two-dimensional gel electrophoresis the CDK4 modification profile and the presence of T172-phosphorylated CDK4 in a collection of 98 fresh-frozen tissues and in 21 cell lines. A sub-cohort of samples was characterized by RNA sequencing and immunohistochemistry. Sensitivity to CDK4/6i (palbociclib and abemaciclib) was assessed by BrdU incorporation/viability assays. Treatment of cell lines with CDK4/6i and combination with BRAF/MEK inhibitors (dabrafenib/trametinib) was comprehensively evaluated by western blot, characterization of immunoprecipitated CDK4 and CDK2 complexes and clonogenic assays.

Results

CDK4 phosphorylation was detected in all well-differentiated thyroid carcinomas (n=29), 19/20 PDTC, 16/23 ATC and 18/21 thyroid cancer cell lines, including 11 ATC-derived ones. Tumors and cell lines without phosphorylated CDK4 presented very high p16CDKN2A levels, which were associated with proliferative activity. Absence of CDK4 phosphorylation in cell lines was associated with CDK4/6i insensitivity. RB1 defects (the primary cause of intrinsic CDK4/6i resistance) were not found in 5/7 tumors without detectable phosphorylated CDK4. A previously developed 11-gene expression signature identified the likely unresponsive tumors, lacking CDK4 phosphorylation. In cell lines, palbociclib synergized with dabrafenib/trametinib by completely and permanently arresting proliferation. These combinations prevented resistance mechanisms induced by palbociclib, most notably Cyclin E1-CDK2 activation and a paradoxical stabilization of phosphorylated CDK4 complexes.

Conclusion

Our study supports further clinical evaluation of CDK4/6i and their combination with anti-BRAF/MEK therapies as a novel effective treatment against advanced thyroid tumors. Moreover, the complementary use of our 11 genes predictor with p16/KI67 evaluation could represent a prompt tool for recognizing the intrinsically CDK4/6i insensitive patients, who are potentially better candidates to immediate chemotherapy.

Familial parathyroid tumours-comparison of clinical profiles between syndromes

INTRODUCTION

Primary hyperparathyroidism (PHPT) caused by parathyroid tumours is mostly sporadic, with a genetic cause identified in 5-10% of cases. Familial parathyroid tumours can be included in complex syndromes, such as multiple endocrine neoplasia (MEN) type 1, 2A and 4 or hyperparathyroidism-jaw tumour syndrome (HPT-JT).

OBJECTIVE

Characterisation of the familial parathyroid tumours followed-up at our centre and comparison of the different clinicopathological manifestations between the syndromes.

METHODS

Retrospective analysis of 48 patients with familial parathyroid tumours harbouring RET (n = 11), CDC73 (n = 20) and MEN1 (n = 17) germline mutations was performed.

RESULTS

Cases of PHPT in MEN2A syndrome presented with lower serum PTH (sPTH) and serum calcium (sCa) levels at diagnosis (sPTH = 108.0 (IQR 53.3) pg/mL, sCa = 10.6 ± 1.1 mg/dL) than MEN1 (sPTH = 196.9 (IQR 210.5) pg/mL, sCa = 11.7 ± 1.2 mg/dL) (p = 0.01, p = 0.03, respectively) or HPT-JT cases (sPTH = 383.5 (IQR 775.8) pg/mL, sCa = 12.9 ± 1.8 mg/dL) (p = 0.01; p < 0.001, respectively). There was a statistical difference in sCa levels between MEN1 and HPT-JT (p = 0.02), but not between sPTH (p = 0.07). The predominant first manifestation of the syndrome in MEN1 was gastroenteropancreatic neuroendocrine tumour (GEP-NET) in 47.1% of the cases, in MEN2A was medullary thyroid cancer (90.9%) and in HPT-JT was PHPT in 85% patients. In MEN1 syndrome, the number of affected parathyroid glands was significantly higher than in MEN2A (p < 0.001) and HPT-JT (p = 0.01).

CONCLUSION

The first manifestation of the syndrome in MEN1 cases was GEP-NET and not PHPT. Although presenting at similar ages, patients with MEN2A exhibit less severe biochemical and clinical PHPT at diagnosis than the other familial syndromes.

Target therapy for BRAF mutated anaplastic thyroid cancer: a clinical and molecular study

OBJECTIVES

Anaplastic thyroid carcinoma (ATC) has a poor survival. The combination of Dabrafenib plus Trametinib (DT) had a significant impact in survival of BRAF p.V600E patients. However, durable responses may be compromised by resistance. We aim to present our experience with DT in BRAF positive ATC patients and compare the outcomes with usual therapy, and to study tumor molecular alterations in the DT group.

METHODS

Patients treated between May 2018 and April 2022 in a tertiary referral center, assessed for BRAF status were included. Patients were divided in three groups: BRAF p.V600E treated with DT, BRAF wild type (WT) under multimodal therapy (MT), and BRAF WT under compassionate care (CC). Response was assessed monthly in the first 6 months and every 3 months afterwards, by RECIST 1.1. Overall survival (OS) and progression-free survival (PFS) were estimated with the Kaplan-Meier method and compared with the log-rank test.

RESULTS

Twenty-seven ATC patients were included (DT = 9, MT = 8, and CC = 10). Median OS was 475 days for DT, 156 days for MT, and 39 days for CC (P < .001). At 12 months, only patients in the DT group were alive (71%). Median PFS was 270 days, in the DT group, compared with less than 32 days in BRAF WT (P < .001). No severe adverse events were reported. Molecular profiling showed that in one of the four clinical progressions, a pathogenic NRAS mutation was found.

CONCLUSIONS

Our results show a significant real-world efficacy of Dabrafenib plus Trametinib in both survival and recurrence compared with standard treatment, with a good safety profile.

Parathyroid carcinoma: Single centre experience

OBJECTIVE

Parathyroid Carcinoma is a rare malignant neoplasm, accounting for less than 1% of primary hyperparathyroidism cases. Parathyroid carcinomas are characterized by markedly elevated levels of PTH, severe hypercalcemia and established target organ damage. The authors report the experience of a single centre regarding the management and outcome of patients with parathyroid carcinomas and revise relevant literature.

DESIGN

Retrospective review of all patients with parathyroid carcinoma evaluated at a tertiary oncologic centre from 1991 until 2021.

RESULTS

Seventeen patients were identified (10 males), with a mean age at diagnosis of 53 ± 16 years and a median follow-up of 16.5 years. Most patients presented with hypercalcemia (n = 15), with a mean serum calcium concentration of 13.5 mg/dl (9.6-16.5) and mean PTH of 1173 pg/ml (276-2500). Hyperparathyroidism-mediated organ damage was observed in most patients (n = 16), with predominant renal (n = 12) and skeletal (n = 9) complications. En bloc surgical resection was performed in nine patients. Three patients underwent adjuvant radiotherapy. Recurrence was observed in 8 cases (47.1%) after a median of 24 months following surgery and no independent predictors of recurrence were identified. The overall survival and disease specific survival at 5-year was 88% and 94%, respectively. CDC73 mutations were present in 38.5% of analysed patients and one patient was diagnosed with MEN1.

CONCLUSION

Parathyroid carcinoma is associated with a significant rate of recurrence and limited effective treatment beyond initial complete surgical resection. Therefore, preoperatively high index of suspicion is paramount to optimize patient care. This is, to our knowledge, the largest Portuguese cohort published so far.

A case report of multiple endocrine neoplasia type 1 and autoimmune disease: Coincidence or correlation?

RATIONALE

Multiple Endocrine Neoplasia type 1 (MEN1) is a familial syndrome that results from the disruption of a tumor suppressor protein called MENIN. Its management is challenging, as MEN1 affects different endocrine tissues and predisposes to both benign and malignant tumors. MENIN-deficient cells have recently been recognized to play a role in triggering autoimmunity. Herein, we present a case of MEN1 with multiple endocrine and autoimmune disorders.

PATIENT CONCERNS

A 50 years old female with a 25 years history of complicated nephrolithiasis presented with primary hyperparathyroidism.

DIAGNOSES

Over several decades, she was diagnosed with recurrent primary hyperparathyroidism, autoimmune thyroiditis, multinodular goiter, pernicious anemia, metastatic gastric type 1 neuroendocrine tumor, macroprolactinemia, gonadotropin deficiency, mucosa-associated lymphoid tissue lymphoma of the thyroid gland, positive anti-calcium sensor receptor antibodies, and BRCA 1/2-negative invasive breast cancer. The autoimmune regulator gene was sequenced, but no pathogenic variants were found. Next-generation sequencing revealed both a pathogenic MEN1 mutation and a benign CDC73 gene variant. Familial genetic screening revealed a large kindred with multiple carriers of one or both genetic variants (MEN1 = 19; CDC73 = 7).

INTERVENTIONS

The patient underwent surgical excision of three parathyroid glands, total thyroidectomy and breast tumorectomy plus tamoxifen, and monthly injections of octreotide. The patient and family members with the MEN1 mutation are under a life-long surveillance program for MEN1 prototypic tumors.

OUTCOMES

The patient was stable and alive during a 24-years follow-up period.

LESSONS

With the present case, the authors highlight a new interplay between MENIN and the immune system, which may have implications for future targeted life-long surveillance and treatment of MEN1 patients.

Identification of SPRY4 as a Novel Candidate Susceptibility Gene for Familial Nonmedullary Thyroid Cancer

Background: The molecular basis of familial nonmedullary thyroid cancer (FNMTC) is still poorly understood, representing a limitation for molecular diagnosis and clinical management. In this study, we aimed to identify new susceptibility genes for FNMTC through whole-exome sequencing (WES) analysis of leukocyte DNA of patients from a highly informative FNMTC family. Methods: We selected six affected family members to conduct WES analysis. Bioinformatic analyses were undertaken to filter and select the genetic variants shared by the affected members, which were subsequently validated by Sanger sequencing. To select the most likely pathogenic variants, several studies were performed, including family segregation analysis, in silico impact characterization, and gene expression (messenger RNA and protein) depiction in databases. For the most promising variant identified, we performed in vitro studies to validate its pathogenicity. Results: Several potentially pathogenic variants were identified in different candidate genes. After filtering with appropriate criteria, the variant c.701C>T, p.Thr234Met in the SPRY4 gene was prioritized for in vitro functional characterization. This SPRY4 variant led to an increase in cell viability and colony formation, indicating that it confers a proliferative advantage and potentiates clonogenic capacity. Phosphokinase array and Western blot analyses suggested that the effects of the SPRY4 variant were mediated through the mitogen-activated protein kinase/extracellular signal-regulated kinase pathway, which was further supported by a higher responsiveness of thyroid cancer cells with the SPRY4 variant to a MEK inhibitor. Conclusions: WES analysis in one family identified SPRY4 as a likely novel candidate susceptibility gene for FNMTC, allowing a better understanding of the cellular and molecular mechanisms underlying thyroid cancer development.

Correlation of molecular data with histopathological and clinical features in a series of 66 patients with medullary thyroid carcinoma

PURPOSE

Medullary thyroid carcinoma (MTC) displays a wide variety of histopathological features, and several histological variants have been described. In follicular cell-derived thyroid carcinomas, there is a good correlation between genotype and phenotype. In this study, we investigated whether such a correlation is also present in MTC.

METHODS

The histopathological features were evaluated in a series of 66 molecularly characterised tumours and correlated with the clinical characteristics.

RESULTS

Most MTC exhibited the classical variant (83.3%). Other variants included spindle cell (6.1%), pseudopapillary (4.5%), paraganglioma-like (3.0%), angiosarcoma-like (1.5%), and oncocytic follicular (1.5%). Tumours were classified into four groups: group 1, with somatic p.Met918Thr and p.Ala883Phe RET mutations; group 2, with other RET mutations; group 3, with RAS mutations; and group 4, without RET or RAS mutations. Tumours from groups 1 and 4 were typically associated with the classical variant, with abundant fibrosis, lymphovascular invasion, extrathyroidal extension, and more advanced stages of disease, whereas group 2 included histological variants other than the classical variant (namely, pseudopapillary and paraganglioma-like), with tumours that were highly cellular, less invasive, and with a better overall prognosis. In tumours from group 4, amyloid deposition was characteristically absent or low. The spindle cell variant appeared only in tumours from group 3, which had high cellularity and a degree of invasion and prognosis intermediate between groups 1 and 2, but better than group 4. The grade of fibrosis correlated directly with the clinical outcome.

CONCLUSION

Our results support the idea that a genotype-phenotype correlation does, indeed, exist in MTC. However, further studies are warranted to confirm these findings in a larger sample size.

High-Throughput Sequencing Identifies 3 Novel Susceptibility Genes for Hereditary Melanoma

Cutaneous melanoma is one of the most aggressive human cancers due to its high invasiveness. Germline mutations in high-risk melanoma susceptibility genes have been associated with development hereditary melanoma; however, most genetic culprits remain elusive. To unravel novel susceptibility genes for hereditary melanoma, we performed whole exome sequencing (WES) on eight patients with multiple primary melanomas, high number of nevi, and negative for high and intermediate-risk germline mutations. Thirteen new potentially pathogenic variants were identified after bioinformatics analysis and validation. CDH23, ARHGEF40, and BRD9 were identified as the most promising susceptibility genes in hereditary melanoma. In silico analysis of CDH23 and ARHGEF40 variants provided clues for altered protein structure and function associated with the identified mutations. Then, we also evaluated the clinical value of CDH23, ARHGEF40, and BRD9 expression in sporadic melanoma by using the TCGA dataset (n = 461). No differences were observed in BRD9 expression between melanoma and normal skin samples, nor with melanoma stage, whereas ARHGEF40 was found overexpressed, and CDH23 was downregulated and its loss was associated with worse survival. Altogether, these results reveal three novel genes with clinical relevance in hereditary and sporadic melanoma.

Establishment and characterization of a new patient-derived anaplastic thyroid cancer cell line (C3948), obtained through fine-needle aspiration cytology

PURPOSE

Anaplastic thyroid cancer (ATC) is among the most aggressive and unresectable tumors, presenting a bad prognosis. A better comprehension of the functional and molecular mechanisms behind the aggressiveness of this cancer, as well as new biomarkers for aggressiveness, prognosis, and response to therapy are required. However, owing to their irresectability, ATC tissue is not always accessible. Here we describe the establishment and characterization of a new patient-derived cell line, obtained from an unresectable ATC through fine-needle aspiration cytology (FNAC).

METHODS

The morphology, expression of epithelial and thyroid markers, cytogenetic, mutational and gene expression profiles, doubling time, and drug-resistance profile of the new cell line, designated C3948, were investigated using several methodologies: immunostaining, karyotype analysis, comparative genomic hybridization (CGH), fluorescent in situ hybridization (FISH), next-generation sequencing (NGS), Sanger sequencing, gene expression microarrays, cell counting, and IC₅₀ determination.

RESULTS

Results indicate that C3948 cell line has a histological phenotype representative of original ATC cells and a completely aberrant karyotype with many chromosomal losses and gains; harbors mutated TP53, STK11, and DIS3L2 genes; presents a gene expression profile similar to C643 ATC commercial cell line, but with some unique alterations; has a doubling time similar to C643; and the IC₅₀ profile for paclitaxel, doxorubicin, and cisplatin is similar to C643, although higher for cisplatin.

CONCLUSIONS

These observations are consistent with a typical ATC cell profile, supporting C3948 cell line as a novel preclinical model, and FNAC as a useful approach to better study anaplastic thyroid cancer, including testing of new anticancer therapies.

SDHx-related pheochromocytoma/paraganglioma - genetic, clinical, and treatment outcomes in a series of 30 patients from a single center

PURPOSE

Germline mutations in the four genes that encode the succinate dehydrogenase complex (SDHx) are a risk factor for developing pheochromocytomas and/or paragangliomas. The precise genotype-phenotype correlations are still uncertain and the most common SDHx genetic defects in the Portuguese population are poorly described. The objectives of our study were to characterize the genetic alterations, clinical features, and treatment outcomes of a cohort of SDHx-related pheochromocytomas and/or paragangliomas patients.

METHODS

Single center, retrospective analysis based on the presence of a SDHx mutation in cases diagnosed from 1986 until October 2016.

RESULTS

Thirty cases were included. The mean age at diagnosis was 36.8 years (±15.4 years) and 53.3% were females. Remission was observed in 33.3% and stable disease (including partial responses) in 53.0%. SDHC and SDHD patients were prone to develop single and multiple head and neck paragangliomas, respectively. SDHB patients carried an increased risk of malignancy. Deletions in SDHB exon-1 and in SDHD exon-4 were the most common genetic findings. SDHB patients and head and neck paragangliomas had the worse prognosis, the former related to malignancy, and the latter to cranial nerve deficits, unresectable disease, and multimodality interventions. Peptide receptor radionuclide therapy and radioactive iodine MIBG therapy proved to be ineffective. Radiotherapy represented a good alternative in unresectable head and neck paragangliomas and in bone metastases.

CONCLUSION

This single center study is the most complete Portuguese cohort in the literature and helps to understand the behavior of tumors based on their genotype and anatomical location.

The efficacy of HRAS and CDK4/6 inhibitors in anaplastic thyroid cancer cell lines

PURPOSE

Anaplastic thyroid carcinomas (ATCs) are non-responsive to multimodal therapy, representing one of the major challenges in thyroid cancer. Previously, our group has shown that genes involved in cell cycle are deregulated in ATCs, and the most common mutations in these tumours occurred in cell proliferation and cell cycle related genes, namely TP53, RAS, CDKN2A and CDKN2B, making these genes potential targets for ATCs treatment. Here, we investigated the inhibition of HRAS by tipifarnib (TIP) and cyclin D-cyclin-dependent kinase 4/6 (CDK4/6) by palbociclib (PD), in ATC cells.

METHODS

ATC cell lines, mutated or wild type for HRAS, CDKN2A and CDKN2B genes, were used and the cytotoxic effects of PD and TIP in each cell line were evaluated. Half maximal inhibitory concentration (IC50) values were determined for these drugs and its effects on cell cycle, cell death and cell proliferation were subsequently analysed.

RESULTS

Cell culture studies demonstrated that 0.1 µM TIP induced cell cycle arrest in the G2/M phase (50%, p < 0.01), cell death, and inhibition of cell viability (p < 0.001), only in the HRAS mutated cell line. PD lowest concentration (0.1 µM) increased significantly cell cycle arrest in the G0/G1 phase (80%, p < 0.05), but only in ATC cell lines with alterations in CDKN2A/CDKN2B genes; additionally, 0.5 µM PD induced cell death. The inhibition of cell viability by PD was more pronounced in cells with alterations in CDKN2A/CDKN2B genes (p < 0.05) and/or cyclin D1 overexpression.

CONCLUSIONS

This study suggests that TIP and PD, which are currently in clinical trials for other types of cancer, may play a relevant role in ATC treatment, depending on the specific tumour molecular profile.

The role of EIF1AX in thyroid cancer tumourigenesis and progression

PURPOSE

The EIF1AX gene was recently described as a new thyroid cancer-related gene. Its mutations were mainly reported in poorly differentiated (PDTC) and anaplastic thyroid cancers (ATC), but also in well-differentiated thyroid cancer (WDTC) and in benign thyroid lesions, although less frequently. Our aim was to address whether EIF1AX mutations are present in the different stages of thyroid tumourigenesis (from hyperplasia to well-differentiated and to poorly differentiated/undifferentiated lesions), and to clarify its role in this process.

METHODS

We analysed the EIF1AX gene in a series of 16 PDTC and ATC cases with coexistent well-differentiated regions and/or benign lesions. In EIF1AX mutant cases we also assessed the presence of RAS genes mutations.

RESULTS

We identified the mutation p.Ala113_splice in the EIF1AX gene in two PDTCs (neither present in the well-differentiated counterparts nor in the benign areas). One of these tumours also evidenced the mutation p.Glu61Arg in NRAS in both poorly and well-differentiated regions, further suggesting that the EIF1AX p.Ala113_splice mutation could be associated with tumoural progression. In another patient we did not find any EIF1AX alteration in the PDTC component, but we detected the EIF1AX p.Gly6_splice mutation in the PTC area (both regions were RAS wild-type). This mutation did not seem to be related with dedifferentiation.

CONCLUSIONS

According to our results, distinct mutations on EIF1AX may be related to different phenotypes/behaviours. Despite being a small series, which reflects the difficulty in retrieving PDTC and ATC surgical samples with well-differentiated and/or benign areas, our study may provide new insights into thyroid cancer tumourigenesis and dedifferentiation.

Homozygous Calcium-Sensing Receptor Polymorphism R544Q Presents as Hypocalcemic Hypoparathyroidism

CONTEXT

Autosomal dominant hypocalcemia type 1 (ADH1) is caused by heterozygous activating mutations in the calcium-sensing receptor gene (CASR). Whether polymorphisms that are benign in the heterozygous state pathologically alter receptor function in the homozygous state is unknown.

OBJECTIVE

To identify the genetic defect in an adolescent female with a history of surgery for bilateral cataracts and seizures. The patient has hypocalcemia, hyperphosphatemia, and low serum PTH level. The parents of the proband are healthy.

METHODS

Mutation testing of PTH, GNA11, GCM2, and CASR was done on leukocyte DNA of the proband. Functional analysis in transfected cells was conducted on the gene variant identified. Public single nucleotide polymorphism (SNP) databases were searched for the presence of the variant allele.

RESULTS

No mutations were identified in PTH, GNA11, and GCM2 in the proband. However, a germline homozygous variant (c.1631G>A; p.R544Q) in exon 6 of the CASR was identified. Both parents are heterozygous for the variant. The variant allele frequency was near 0.1% in SNP databases. By in vitro functional analysis, the variant was significantly more potent in stimulating both the Ca2+i and MAPK signaling pathways than wild type when transfected alone (P < 0.05) but not when transfected together with wild type. The overactivity of the mutant CaSR is due to loss of a critical structural cation-π interaction.

CONCLUSIONS

The patient's hypoparathyroidism is due to homozygosity of a variant in the CASR that normally has weak or no phenotypic expression in heterozygosity. Although rare, this has important implications for genetic counseling and clinical management.

Identification of somatic TERT promoter mutations in familial nonmedullary thyroid carcinomas

OBJECTIVE

The genes causing familial nonmedullary thyroid carcinoma (FNMTC) identified to date are only involved in a small fraction of the families. Recently, somatic mutations in TERT promoter region and in EIF1AX gene were reported in thyroid tumours of undefined familial status. The aim of this study was to investigate the role of TERT and EIF1AX mutations in familial thyroid tumours.

DESIGN

The promoter region of TERT was sequenced in leucocyte DNA of the probands from 75 FNMTC families. In thyroid tumours from 54 familial cases, we assessed somatic TERT promoter, RAS and BRAF hotspot mutations, and the whole EIF1AX gene.

RESULTS

No potentially pathogenic germline variants were identified in TERT in the 75 FNMTC families' probands. In the 54 carcinomas, we identified five cases (9%) with hotspot somatic TERT promoter mutations. BRAF mutations were found in 41% of the tumours. All TERT-positive samples were also positive for BRAF p.Val600Glu, and this co-occurrence was found to be statistically significant (P=.008). RAS mutations were detected in four tumours wild-type for TERT (7%). Evaluation of tumour mutation data together with the patients' clinicopathological features revealed a significant correlation between TERT plus BRAF mutations and advanced tumour stage (T4) (P=.020). No mutations were identified in EIF1AX.

CONCLUSIONS

The results of this study suggest that TERT promoter and EIF1AX mutations are not frequently involved in FNMTC aetiology. However, we show for the first time that TERT alterations are associated with familial thyroid tumour progression. Our data also suggest that TERT mutations are more often found in concomitance with BRAF mutations in advanced stages of FNMTC.

Genomic profiling reveals mutational landscape in parathyroid carcinomas

Parathyroid carcinoma (PC) is an extremely rare malignancy lacking effective therapeutic intervention. We generated and analyzed whole-exome sequencing data from 17 patients to identify somatic and germline genetic alterations. A panel of selected genes was sequenced in a 7-tumor expansion cohort. We show that 47% (8 of 17) of the tumors harbor somatic mutations in the CDC73 tumor suppressor, with germline inactivating variants in 4 of the 8 patients. The PI3K/AKT/mTOR pathway was altered in 21% of the 24 cases, revealing a major oncogenic pathway in PC. We observed CCND1 amplification in 29% of the 17 patients, and a previously unreported recurrent mutation in putative kinase ADCK1. We identified the first sporadic PCs with somatic mutations in the Wnt canonical pathway, complementing previously described epigenetic mechanisms mediating Wnt activation. This is the largest genomic sequencing study of PC, and represents major progress toward a full molecular characterization of this rare malignancy to inform improved and individualized treatments.

RAS proto-oncogene in medullary thyroid carcinoma

Medullary thyroid carcinoma (MTC) is a rare malignancy originating from the calcitonin-secreting parafollicular thyroid C cells. Approximately 75% of cases are sporadic. Rearranged during transfection (RET) proto-oncogene plays a crucial role in MTC development. Besides RET, other oncogenes commonly involved in the pathogenesis of human cancers have also been investigated in MTC. The family of human RAS genes includes the highly homologous HRAS, KRAS, and NRAS genes that encode three distinct proteins. Activating mutations in specific hotspots of the RAS genes are found in about 30% of all human cancers. In thyroid neoplasias, RAS gene point mutations, mainly in NRAS, are detected in benign and malignant tumors arising from the follicular epithelium. However, recent reports have also described RAS mutations in MTC, namely in HRAS and KRAS. Overall, the prevalence of RAS mutations in sporadic MTC varies between 0-43.3%, occurring usually in tumors with WT RET and rarely in those harboring a RET mutation, suggesting that activation of these proto-oncogenes represents alternative genetic events in sporadic MTC tumorigenesis. Thus, the assessment of RAS mutation status can be useful to define therapeutic strategies in RET WT MTC. MTC patients with RAS mutations have an intermediate risk for aggressive cancer, between those with RET mutations in exons 15 and 16, which are associated with the worst prognosis, and cases with other RET mutations, which have the most indolent course of the disease. Recent results from exome sequencing indicate that, besides mutations in RET, HRAS, and KRAS, no other recurrent driver mutations are present in MTC.

Familial vs sporadic papillary thyroid carcinoma: a matched-case comparative study showing similar clinical/prognostic behaviour

OBJECTIVE

Familial non-medullary thyroid cancer has been proposed as an aggressive clinical entity. Our aim in this study is to investigate potential distinguishing features as well as the biological and clinical aggressiveness of familial vs sporadic papillary thyroid carcinoma (PTC). We assessed clinicopathological characteristics, outcome measures and DNA ploidy.

DESIGN

A matched-case comparative study.

METHODS

A series of patients with familial PTC (n=107) and two subgroups, one with three or more affected elements (n=32) and another including index cases only (n=61), were compared with patients with sporadic PTC (n=107), matched by age, gender, pTNM disease extension and approximate follow-up duration. Histological variant, extrathyroidal extension, vascular invasion, tumour multifocality and bilateral growth were evaluated. Ploidy pattern was analysed in available samples by DNA flow cytometry. The probabilities of disease-free survival (DFS) and overall survival (OS) were estimated according to the Kaplan-Meier (K-M) method.

RESULTS

No patient with familial PTC died of disease during follow-up (median, 72 months), contrarily to five patients (4.7%) (P=0.06) with sporadic PTC (median, 90 months). There was a significantly higher tumour multifocality in familial PTC (index cases subgroup) vs sporadic PTC (P=0.035), and a trend, in the familial PTC cohort with three or more affected elements, to show extrathyroidal extension (P=0.054) more frequently. No difference was observed in DNA ploidy status. The K-M analyses showed no significant differences between both entities in relation to DFS or OS.

CONCLUSION

Apart from multifocality, familial PTC appears to have similar clinical/prognostic behaviour when compared with sporadic forms of the disease.

FOXE1 polymorphisms are associated with familial and sporadic nonmedullary thyroid cancer susceptibility

OBJECTIVE

FOXE1 is a transcription factor required for thyroid differentiation and function. FOXE1 locus polymorphisms (chromosome 9q22.33) were recently associated with increased sporadic thyroid cancer risk. In this study, we aimed to investigate the association of FOXE1 variants with nonmedullary thyroid cancer (NMTC), in both sporadic and familial (FNMTC) cases from the Portuguese population.

DESIGN AND METHODS

Nine variants located at the FOXE1 locus were sequenced in genomic DNA from 60 FNMTC probands and 80 patients with sporadic NMTC. Alleles were tested for association with thyroid cancer, against 130 healthy matched Portuguese controls.

RESULTS

All variants were significantly associated with increased thyroid cancer risk when combining familial and sporadic cases (OR range = 1·62-2·58). In particular, two reported risk variants were associated with the disease: rs965513 (allele A) with familial (OR = 2·30, 95% CI = 1·48-3·59, P = 0·0002) and sporadic (OR = 2·81, 95% CI = 1·87-4·22, P < 0·0001) NMTC and rs1867277 (allele A) with the sporadic (OR = 1·76, 95% CI = 1·18-2·62, P = 0·0052) and combined NMTC cases (OR = 1·70, 95% CI = 1·21-2·40, P = 0·0022). Interestingly, we also identified association of FOXE1 polyalanine tract expansions (>14 alanines) with thyroid cancer risk, in both familial (OR = 2·56, 95% CI = 1·64-4·01, P < 0·0001) and sporadic (OR = 2·44, 95% CI = 1·61-3·68, P < 0·0001) cases.

CONCLUSIONS

We found compelling evidence of association between FOXE1 variants and thyroid cancer risk in the Portuguese population. To our knowledge, this is the first study supporting the association of this locus with both sporadic and familial NMTC susceptibility.

High prevalence of RAS mutations in RET-negative sporadic medullary thyroid carcinomas

CONTEXT

Sporadic medullary thyroid carcinomas (MTC) frequently harbor mutations in the RET protooncogene. We have earlier reported a series of 51 sporadic MTC with 64.7% of RET-positive and 35.3% of RET-negative cases.

OBJECTIVE

In the present study, we investigated the possible involvement of RAS and BRAF protooncogenes in the development of sporadic RET-negative MTC.

PATIENTS AND DESIGN

We performed PCR amplification and sequencing analysis of the three mutational hotspots (codons 12, 13, and 61) of the H-, K-, and N-RAS genes, and of the mutational hotspot (codon 600) and exon 11 of the BRAF gene in 65 sporadic MTC, of which 40 were RET positive and 25 were RET negative.

RESULTS

Somatic H-RAS and K-RAS mutations were detected in 14 of 25 (56.0%) and three of 25 (12.0%) of RET-negative sporadic MTC, respectively. On the other hand, only one of 40 (2.5%) RET-positive sporadic MTC had a RAS mutation, namely in H-RAS. One of the H-RAS mutations was novel (c.32_37dupCCGGCG). No mutations of N-RAS or BRAF were detected in all assessed tumor samples.

CONCLUSIONS

Overall, our results showed that RAS mutations were present in 68.0% (17 of 25) of the RET-negative MTC and in only 2.5% of the RET-positive MTC (P < 0.0001), suggesting that activation of the protooncogenes RAS and RET represents alternative genetic events in sporadic MTC tumorigenesis.

Differential methylation as a cause of allele dropout at the imprinted GNAS locus

INTRODUCTION

We detected false homozygosity at the NESP55 differentially methylated region of the imprinted GNAS locus while analyzing the segregation of single-nucleotide polymorphisms (SNPs) in families with pseudohypoparathyroidism type Ib (PHP-Ib). We hypothesized that differential methylation of NESP55 could affect polymerase chain reaction (PCR) amplification, resulting in allele dropout.

METHODS

We genotyped 10 normal controls for four SNPs in NESP55 differentially methylated region. SNPs were amplified by standard PCR conditions and with the addition of dimethyl sulfoxide. The methylated allele was identified by HpaII analysis, and haplotypes were confirmed using subcloning strategies. All SNPs were also genotyped in a PHP-Ib patient (P1), carrying methylation at both NESP55 alleles, and in an in vitro methylated control DNA (SSSI-N4).

RESULTS

In the control samples, we identified allele dropout of the methylated allele in 85% of the amplifications, using standard PCR conditions. Addition of dimethyl sulfoxide to the PCR successfully prevented dropout in all cases. No amplification bias was observed for P1 and SSSI-N4 samples.

CONCLUSIONS

For the first time, we report that differential methylation of imprinted regions can lead to preferential amplification of unmethylated alleles. Addition of coadjuvants to the PCR may facilitate amplification of both alleles, providing an accurate genotyping in cases with methylation-related diseases.

Gene expression profiling associated with the progression to poorly differentiated thyroid carcinomas

BACKGROUND

Poorly differentiated thyroid carcinomas (PDTC) represent a heterogeneous, aggressive entity, presenting features that suggest a progression from well-differentiated carcinomas. To elucidate the mechanisms underlying such progression and identify novel therapeutic targets, we assessed the genome-wide expression in normal and tumour thyroid tissues.

METHODS

Microarray analyses of 24 thyroid carcinomas - 7 classic papillary, 8 follicular variants of papillary (fvPTC), 4 follicular (FTC) and 5 PDTC - were performed and correlated with RAS, BRAF, RET/PTC and PAX8-PPARG alterations. Selected genes were validated by quantitative RT-PCR in an independent set of 28 thyroid tumours.

RESULTS

Unsupervised analyses showed that gene expression similarity was higher between PDTC and fvPTC, particularly for tumours harbouring RAS mutations. Poorly differentiated thyroid carcinomas presented molecular signatures related to cell proliferation, poor prognosis, spindle assembly checkpoint and cell adhesion. Compared with normal tissues, PTC had 307 out of 494 (60%) genes over-expressed, FTC had 137 out of 171 (80%) genes under-expressed, whereas PDTC had 92 out of 107 (86%) genes under-expressed, suggesting that gene downregulation is involved in tumour dedifferentiation. Significant UHRF1 and ITIH5 deregulated gene expression in PDTC, relatively to normal tissues, was confirmed by quantitative RT-PCR.

CONCLUSION

Our findings suggest that fvPTC are possible precursors of PDTC. Furthermore, UHRF1 and ITIH5 have a potential therapeutic/prognostic value for aggressive thyroid tumours.

Correlation of RET somatic mutations with clinicopathological features in sporadic medullary thyroid carcinomas

Screening of REarranged during Transfection (RET) gene mutations has been carried out in different series of sporadic medullary thyroid carcinomas (MTC). RET-positive tumours seem to be associated to a worse clinical outcome. However, the correlation between the type of RET mutation and the patients' clinicopathological data has not been evaluated yet. We analysed RET exons 5, 8, 10-16 in fifty-one sporadic MTC, and found somatic mutations in thirty-three (64.7%) tumours. Among the RET-positive cases, exon 16 was the most frequently affected (60.6%). Two novel somatic mutations (Cys630Gly, c.1881del18) were identified. MTC patients were divided into three groups: group 1, with mutations in RET exons 15 and 16; group 2, with other RET mutations; group 3, having no RET mutations. Group 1 had higher prevalence (P=0.0051) and number of lymph node metastases (P=0.0017), and presented more often multifocal tumours (P=0.037) and persistent disease at last control (P=0.0242) than group 2. Detectable serum calcitonin levels at last screening (P=0.0119) and stage IV disease (P=0.0145) were more frequent in group 1, than in the other groups. Our results suggest that, among the sporadic MTC, cases with RET mutations in exons 15 and 16 are associated with the worst prognosis. Cases with other RET mutations have the most indolent course, and those with no RET mutations have an intermediate risk.

Mapping a new familial thyroid epithelial neoplasia susceptibility locus to chromosome 8p23.1-p22 by high-density single-nucleotide polymorphism genome-wide linkage analysis

CONTEXT

Familial nonmedullary thyroid carcinoma (FNMTC) accounts for approximately 5% of all thyroid tumors. Genetic mapping studies have identified four different chromosomal regions predisposing to FNMTC: fPTC/PRN (1p13.2-1q22), NMTC1 (2q21), MNG1 (14q32), and TCO (19p13.2).

OBJECTIVE

Our objective was to map the gene predisposing to familial thyroid epithelial neoplasia in a large Portuguese family.

METHODS AND RESULTS

The clinical screening of a Portuguese family identified 11 members affected with benign thyroid lesions and five affected with thyroid carcinomas. Linkage analysis excluded the involvement of the fPTC/PRN, NMTC1, MNG1, and TCO loci. To map the gene predisposing to thyroid epithelial neoplasia in this family, a genome-wide linkage analysis was conducted, using DNA samples from 17 family members and high-density single-nucleotide polymorphism arrays. A genome-wide significant evidence of linkage, to a single region on chromosome 8p23.1-p22 was obtained, with a maximum parametric haplotype-based LOD score of 4.41 (theta=0.00). Linkage analysis with microsatellite markers confirmed linkage to 8q23.1-p22, and recombination events delimited the minimal region to a 7.46-Mb span. Seventeen suggestive candidate genes located in the minimal region were excluded as susceptibility genes by mutational analysis. Allelic losses in the 8p23.1-p22 region were absent in seven thyroid tumors from family members, suggesting that the inactivation of a putative tumor suppressor gene may have occurred through other mechanisms.

CONCLUSIONS

Our results present evidence for the existence of a novel familial thyroid epithelial neoplasia susceptibility locus on chromosome 8p23.1-p22, providing the basis for the identification of a gene for this disease.

Familial non-medullary thyroid carcinoma (FNMTC): analysis of fPTC/PRN, NMTC1, MNG1 and TCO susceptibility loci and identification of somatic BRAF and RAS mutations

Linkage analysis has identified four familial non-medullary thyroid carcinoma (FNMTC) susceptibility loci: fPTC/PRN (1p13.2-1q22), NMTC1 (2q21), MNG1 (14q32) and TCO (19p13.2). To date, there is no evidence for the involvement of genes from the RAS/RAF signalling pathway in FNMTC. The aim of our study was to evaluate the role of the four susceptibility loci, and RAS/RAF signalling pathway genes, in FNMTC. In total, 8 FNMTC families, and 27 thyroid lesions from family members (22 papillary thyroid carcinomas (PTCs): 11 classic, 10 of the follicular variant and 1 of the mixed variant; 4 follicular thyroid adenomas (FTAs) and 1 nodular goitre (NG)), were evaluated for the involvement of the four susceptibility regions, using linkage and loss of heterozygosity (LOH) analyses. BRAF and H-, N- and K-RAS mutations were also screened in the 27 lesions and patients. Linkage analysis in seven informative families showed no evidence for the involvement of any of the four candidate regions, supporting a genetic heterogeneity for FNMTC. Twenty tumours (74%), of which 18 were PTCs, showed no LOH at the four susceptibility loci. The remaining seven tumours (four PTCs, two FTAs and one NG) showed variable patterns of LOH. Fourteen tumours (52%) had somatic mutations: BRAF-V600E mutation was observed in 9 out of the 22 PTCs (41%); and H-RAS and N-RAS mutations were detected in 5 out of the 22 PTCs (23%). Our data suggest that the four candidate regions are not frequently involved in FNMTC and that the somatic activation of BRAF and RAS plays a role in FNMTC tumourigenesis.

Screening for a BRCA2 rearrangement in high-risk breast/ovarian cancer families: evidence for a founder effect and analysis of the associated phenotypes

PURPOSE

BRCA2 rearrangements are rare genetic events. A large BRCA2 genomic insertion was recurrently observed in our participants, and we sought to characterize it at the molecular and phenotypic level.

PATIENTS AND METHODS

We studied 210 high-risk breast/ovarian cancer families. Fifty-three probands were fully screened for BRCA1/2 mutations, and three of 53 had a large insertion in exon 3 of BRCA2. This finding was analyzed by polymerase chain reaction (PCR), reverse transcriptase PCR (RT-PCR), and sequencing. An additional 157 consecutive families were screened for this mutation by a three-step PCR method. Phenotype and haplotype analysis was also performed.

RESULTS

Sixteen BRCA mutations were observed in 19 of 53 patients (36% detection rate). A recurrent Alu motif insertion in position c.156_157 was observed after sequencing of an abnormal fragment obtained after the amplification of BRCA2 exon 3. RT-PCR revealed exon 3 skipping. Screening of this rearrangement identified 14 additional families (out of 157). In total, 17 (8%) of 210 high-risk families ascertained in our clinic were positive for this mutation. Segregation of a common haplotype (from D13S260 to D13S1695) confirmed a common origin, estimated to have occurred 2,400 to 2,600 years ago. The following four cancer phenotypes were observed in the 17 positive families: female breast (n = 9), male breast (n = 4), breast/ovarian (n = 2), and heterogeneous (n = 2). Male breast cancer was more frequently observed in c.156_157insAlu-positive families compared with negative families (23% v 12%, respectively), and 33% of all male breast cancer families with an identified BRCA mutation were c.156_157insAlu positive.

CONCLUSION

c.156_157insAlu is a founder mutation of Portuguese origin and is the most frequent BRCA2 rearrangement described to date.

Utilisation of a cryptic non-canonical donor splice site of the gene encoding PARAFIBROMIN is associated with familial isolated primary hyperparathyroidism

More than 99% of all splice sites conform to consensus sequences that usually include the invariant dinucleotides gt and ag at the 5' and 3' ends of the introns, respectively. We report on the utilisation of a non-consensus (non-canonical) donor splice site within exon 1 of the HRPT2 gene in familial isolated primary hyperparathyroidism (FIHP). HRPT2 mutations are more frequently associated with the hyperparathyroidism-jaw tumour syndrome (HPT-JT). Patients with FIHP were identified to have a donor splice site mutation, IVS1+1 g-->a, and the consequences of this for RNA processing were investigated. The mutant mRNA lacked 30 bp and DNA sequence analysis revealed this to result from utilisation of an alternative cryptic non-canonical donor splice site (gaatgt) in exon 1 together with the normally occurring acceptor splice site in intron 1. Translation of this mutant mRNA predicted the in-frame loss of 10 amino acids in the encoded protein, termed PARAFIBROMIN. Thus, these FIHP patients are utilising a ga-ag splice site pair, which until recently was considered to be incompatible with splicing but is now known to occur as a rare (<0.02%) normal splicing variant.

Parafibromin mutations in hereditary hyperparathyroidism syndromes and parathyroid tumours

OBJECTIVE

To investigate two patients with the hyperparathyroidism-jaw tumour (HPT-JT) syndrome and three patients with familial isolated hyperparathyroidism (FIHP), together with 31 parathyroid tumours (2 HPT-JT, 2 FIHP and 27 sporadic) for HRPT2 mutations. The HPT-JT syndrome and FIHP are autosomal dominant disorders that may be caused by abnormalities of the HRPT2 gene, located on chromosome 1q31.2. HRPT2 encodes a 531 amino acid protein, parafibromin, which interacts with human homologues of the yeast Paf1 complex.

DESIGN

Leukocyte and tumor DNA was used with HRPT2-specific primers for polymerase chain reaction amplification of the 17 exons and their splice junctions, and the DNA sequences of the polymerase chain reaction products determined.

RESULTS

Three heterozygous germline HRPT2 mutations, two in HPT-JT and one in FIHP patients, were identified. These consisted of one 1-bp duplication (745dup1bp), 1 nonsense (Arg234Stop) and 1 missense (Asp379Asn) mutation. One parathyroid tumour from an FIHP patient was demonstrated to harbour a germline deletion of 1 bp together with a somatic missense (Leu95Pro) mutation, consistent with a 'two-hit' model for hereditary cancer. The 27 sporadic benign parathyroid tumours did not harbour any HRPT2 somatic mutations. Six HRPT2 polymorphisms with allele frequencies ranging from 2% to 15% were detected.

CONCLUSIONS

Our results have identified three novel HRPT2 mutations (two germline and one somatic). The Asp379Asn mutation is likely to disrupt interaction with the human homologue of the yeast Paf1 complex, and the demonstration of combined germline and somatic HRPT2 mutations in a parathyroid tumour provide further evidence for the tumour suppressor role of the HRPT2 gene.

Uterine tumours are a phenotypic manifestation of the hyperparathyroidism-jaw tumour syndrome

The hyperparathyroidism-jaw tumour (HPT-JT) syndrome is an autosomal dominant disorder characterized by parathyroid tumours, which are frequently carcinomas, and ossifying jaw fibromas. In addition, some patients may develop renal tumours and cysts. The gene causing HPT-JT, which is referred to as HRPT2 and is located on chromosome 1q31.2, encodes a 531 amino acid protein called PARAFIBROMIN. To date 42 mutations, of which 22 are germline, have been reported and 97% of these are inactivating and consistent with a tumour suppressor role for HRPT2. We have investigated another four HPT-JT families for germline mutations, searched for additional clinical phenotypes, and examined for a genotype-phenotype correlation. Mutations were found in two families. One family had a novel deletional-insertion at codon 669, and the other had a 2 bp insertion at codon 679, which has been reported in four other unrelated patients. These five unrelated patients and their families with the same mutation were not found to develop the same tumours, thereby indicating an absence of a genotype-phenotype correlation. An analysis of 33 HPT-JT kindreds revealed that affected women in 13 HPT-JT families suffered from menorrhagia in their second to fourth decades. This often required hysterectomy, which revealed the presence of uterine tumours. This resulted in a significantly reduced maternal transmission of the disease. Thus, the results of our analysis expand the spectrum of HPT-JT-associated tumours to include uterine tumours, and these may account for the decreased reproductive fitness in females from HPT-JT families.

Hyperparathyroidism-jaw tumor syndrome in Roma families from Portugal is due to a founder mutation of the HRPT2 gene

The hyperparathyroidism-jaw tumor (HPT-JT) syndrome is an autosomal dominant disorder characterized by the occurrence of parathyroid tumors and ossifying jaw fibromas. The gene causing HPT-JT, HRPT2, is located on chromosome 1q31.2 and consists of 17 exons that encode a 531-amino acid protein, designated parafibromin. We recently identified six Roma families in Portugal with 56 members (11 affected and 45 asymptomatic), who had the HPT-JT syndrome. We postulated that they may have a common ancestor and that the HPT-JT syndrome may be due to a mutation of the HRPT2 gene. Haplotype analysis using 14 chromosome 1q24-q32 polymorphic markers showed that the 11 affected individuals shared a common haplotype defined by seven markers that spanned an approximately 12.5-cM region, flanked centromerically by D1S202 and telomerically by D1S306. DNA sequence analysis identified a 2-bp (TG or GT) frameshift deletion in exon 8, which predicts a truncated parafibromin protein, in all 11 affected individuals. This mutation was also found in 19 unaffected individuals (age range, 12-74 yr) who shared the affected haplotype, suggesting a low age-related penetrance for HPT-JT in these families. Thus, the HPT-JT syndrome in six Roma families from Portugal is due to a novel founder mutation in the HRPT2 gene.

Multiple endocrine neoplasia type 1 (MEN1) germline mutations in familial isolated primary hyperparathyroidism

BACKGROUND

Familial isolated hyperparathyroidism (FIHP) is an autosomal dominant disorder characterized by uniglandular or multiglandular parathyroid tumours that occur in the absence of other endocrine tumours. The disorder may represent either an early stage of multiple endocrine neoplasia type 1 (MEN1), or an allelic variant of MEN1, or a distinct entity involving another locus. We have explored these possibilities in seven families in whom primary hyperparathyroidism occurred as the sole endocrinopathy.

METHODS

Seven FIHP families were ascertained and venous blood samples obtained from 35 members (17 affected and 18 unaffected) for DNA sequence analysis of the MEN1 gene. The mean (+/- SD) follow-up period in the 17 affected members was 15.06 (+/- 8.83) years.

RESULTS

Four heterozygous germline mutations of the MEN1 gene were identified. These consisted of two 4-bp intragenic deletions that would result in prematurely truncated proteins, and two missense (Asp153Val and Ala411Pro) mutations. Furthermore, analysis of parathyroid tumour DNA from one individual revealed a loss of the wild-type allele and retention of the mutant allele, consistent with Knudson's 'two-hit' model of hereditary cancer and a tumour suppressor role for MEN1 in FIHP.

CONCLUSIONS

Our results provide further support for FIHP being a distinct allelic variant of MEN1, and an analysis of the 16 mutations reported to date indicate that FIHP is associated with a higher frequency of missense MEN1 mutations.

Preoperative diagnosis of suspicious parathyroid adenomas by RT-PCR using mRNA extracted from leftover cells in a needle used for ultrasonically guided fine needle aspiration cytology

OBJECTIVE

To determine the usefulness of reverse transcriptase-polymerase chain reaction (RT-PCR) detection of parathormone (PTH) gene mRNA in needle aspirates to confirm the parathyroid nature of suspicious cervical lesions in patients with hyperparathyroidism.

STUDY DESIGN

Ultrasound-guided fine needle aspiration cytology (FNAC) was performed on 12 patients with suspected parathyroid adenomas. The aspirates were subjected to cytologic and chromogranin A examination. Messenger RNA was isolated from left-over cells within the needle, and RT-PCR was used to amplify mRNA encoding PTH.

RESULTS

The 12 aspirates were positive by PTH RT-PCR, and molecular diagnosis was confirmed by histologic examination. The lower sensitivity of cytologic and immunocytochemical methods was demonstrated, respectively, by 67% and 50% of positive results. Sensitivity assays demonstrated that with our system, PTH RT-PCR products are obtained from as few as 10 pg of parathyroid mRNA.

CONCLUSION

The present study showed that RT-PCR-based analysis of PTH gene transcripts in aspirates, obtained by US-guided FNAC of cervical lesions suspicious for parathyroid adenoma, is a feasible, sensitive and specific method for preoperative diagnosis of parathyroid adenomas.

HRPT2, encoding parafibromin, is mutated in hyperparathyroidism-jaw tumor syndrome

We report here the identification of a gene associated with the hyperparathyroidism-jaw tumor (HPT-JT) syndrome. A single locus associated with HPT-JT (HRPT2) was previously mapped to chromosomal region 1q25-q32. We refined this region to a critical interval of 12 cM by genotyping in 26 affected kindreds. Using a positional candidate approach, we identified thirteen different heterozygous, germline, inactivating mutations in a single gene in fourteen families with HPT-JT. The proposed role of HRPT2 as a tumor suppressor was supported by mutation screening in 48 parathyroid adenomas with cystic features, which identified three somatic inactivating mutations, all located in exon 1. None of these mutations were detected in normal controls, and all were predicted to cause deficient or impaired protein function. HRPT2 is a ubiquitously expressed, evolutionarily conserved gene encoding a predicted protein of 531 amino acids, for which we propose the name parafibromin. Our findings suggest that HRPT2 is a tumor-suppressor gene, the inactivation of which is directly involved in predisposition to HPT-JT and in development of some sporadic parathyroid tumors.

Mutational analysis of Portuguese families with multiple endocrine neoplasia type 1 reveals large germline deletions

OBJECTIVE

To determine the spectrum of MEN1 mutations in Portuguese kindreds, and identify mutation-carriers.

PATIENTS, DESIGN AND RESULTS

Six unrelated MEN1 families were studied for MEN1 gene mutations by single-strand conformational polymorphism (SSCP) and DNA sequence analysis of the coding region and exon-intron boundaries of the MEN1 gene. These methods identified 4 different heterozygous mutations in four families: two mutations are novel (mt 1539 delG and mt 655 ims 11 bp) and two have been previously observed (mt 735 del 46p and mt 1656 del C) all resulting in a premature stop codon. In the remaining two families, in whom no mutations or abnormal MEN1 transcripts were detected, segregation studies of the 5' intragenic marker D11S4946 and codon 418 polymorphism in exon 9 revealed two large germline deletions of the MEN1 gene. Southern blot and tumour loss of heterozygosity analysis confirmed and refined the limits of these deletions, which spanned the MEN1 gene at least from: exon 7 to the 3' untranslated region, in one family, and the 5' polymorphic site D11S4946 to exon 9 (obliterating the initiation codon), in the other family. Twenty-six mutant-gene carriers were identified, 6 of which were asymptomatic.

CONCLUSIONS

These results emphasize the importance of the detection of MEN1 germline deletions in patients who do not have mutations of the coding region. Important clues indicating the presence of such deletions may be obtained by segregation studies using the intragenic polymorphisms D11S4946 and at codon 418. The detection of these mutations will help in the genetic counselling of clinical management of the MEN1 families in Portugal.

The hyperparathyroidism-jaw tumour syndrome in a Portuguese kindred

The hyperparathyroidism-jaw tumour (HPT-JT) syndrome is an autosomal dominant disease characterized by the occurrence of parathyroid tumours and fibro-osseous tumours of the jaw bones. Some HPT-JT patients may also develop renal abnormalities, which include Wilms' tumours, hamartomas and polycystic disease. The HPT-JT gene has been mapped to chromosome 1q25-q31, and we report the clinical and genetic findings in a kindred from central Portugal. HPT-JT was observed in six members from three generations; all had primary hyperparathyroidism (five had parathyroid adenomas, one a parathyroid carcinoma). Ossifying jaw fibromas affecting the maxilla and/or mandible were observed in 5/6. Renal cysts (<2.5 cm) were observed in four. Genetic studies using 18 polymorphic loci from chromosome 1q25-q31, together with leukocyte DNA from 11 family members and tumour DNA from three parathyroids (two adenomas and one carcinoma), revealed loss of tumour heterozygosity in the parathyroid carcinoma only, and the retained haplotype was found to cosegregate with the disease in the six affected members. A new Portuguese kindred with the HPT-JT syndrome that maps to chromosome 1q25-q31 has been identified, and these findings will help in the further characterization of this inherited disorder.

Mapping the gene causing hereditary primary hyperparathyroidism in a Portuguese kindred to chromosome 1q22-q31

A Portuguese kindred with autosomal dominant isolated primary hyperparathyroidism (HPT) that was associated with parathyroid adenomas and carcinomas was investigated with the aim of determining the chromosomal location of this gene, designated HPTPort. Leukocyte DNA from 9 affected and 16 unaffected members and 7 parathyroid tumors from 4 patients was used in comparative genomic hybridization (CGH), tumor loss of heterozygosity (LOH), and family linkage studies. The CGH studies revealed abnormalities of chromosomes 1 and 13, and the results of LOH studies were consistent with the involvements of tumor suppressor genes from these regions. Family segregation studies mapped HPTPort to chromosome 1q22-q31 by establishing linkage with eight loci (D1S254, D1S222, D1S202, D1S238, D1S428, D1S2877, D1S422, and D1S412) (peak two-point LOD scores = 3. 46-5.14 at 0% recombination), and defined the location of HPT Port to a 21 cM region flanked centromerically by D1S215 and telomerically by D1S306. Thus, HPTPort has been mapped to chromosome 1q22-q31, and a characterization of this gene will help to elucidate further the mechanisms that are involved in the development of parathyroid tumors.