HABP2 Gene Mutations Do Not Cause Familial or Sporadic Non-Medullary Thyroid Cancer in a Highly Inbred Middle Eastern Population

Chromosomal localization of mutated genes in non-syndromic familial thyroid cancer

Familial non-medullary thyroid carcinoma (FNMTC) is a type of thyroid cancer characterized by genetic susceptibility, representing approximately 5% of all non-medullary thyroid carcinomas. While some cases of FNMTC are associated with familial multi-organ tumor predisposition syndromes, the majority occur independently. The genetic mechanisms underlying non-syndromic FNMTC remain unclear. Initial studies utilized SNP linkage analysis to identify susceptibility loci, including the 1q21 locus, 2q21 locus, and 4q32 locus, among others. Subsequent research employed more advanced techniques such as Genome-wide Association Study and Whole Exome Sequencing, leading to the discovery of genes such as IMMP2L, GALNTL4, WDR11-AS1, DUOX2, NOP53, MAP2K5, and others. But FNMTC exhibits strong genetic heterogeneity, with each family having its own pathogenic genes. This is the first article to provide a chromosomal landscape map of susceptibility genes associated with non-syndromic FNMTC and analyze their potential associations. It also presents a detailed summary of variant loci, characteristics, research methodologies, and validation results from different countries.

Genetic alterations landscape in paediatric thyroid tumours and/or differentiated thyroid cancer: Systematic review

Differentiated thyroid cancer (DTC) is a rare disease in the paediatric population (≤ 18 years old. at diagnosis). Increasing incidence is reflected by increases in incidence for papillary thyroid carcinoma (PTC) subtypes. Compared to those of adults, despite aggressive presentation, paediatric DTC has an excellent prognosis. As for adult DTC, European and American guidelines recommend individualised management, based on the differences in clinical presentation and genetic findings. Therefore, we conducted a systematic review to identify the epidemiological landscape of all genetic alterations so far investigated in paediatric populations at diagnosis affected by thyroid tumours and/or DTC that have improved and/or informed preventive and/or curative diagnostic and prognostic clinical conduct globally. Fusions involving the gene RET followed by NTRK, ALK and BRAF, were the most prevalent rearrangements found in paediatric PTC. BRAF V600E was found at lower prevalence in paediatric (especially ≤ 10 years old) than in adults PTC. We identified TERT and RAS mutations at very low prevalence in most countries. DICER1 SNVs, while found at higher prevalence in few countries, they were found in both benign and DTC. Although the precise role of DICER1 is not fully understood, it has been hypothesised that additional genetic alterations, similar to that observed for RAS gene, might be required for the malignant transformation of these nodules. Regarding aggressiveness, fusion oncogenes may have a higher growth impact compared with BRAF V600E. We reported the shortcomings of the systematized research and outlined three key recommendations for global authors to improve and inform precision health approaches, glocally.

Genetic susceptibility to hereditary non-medullary thyroid cancer

Non-medullary thyroid cancer (NMTC) is the most common type of thyroid cancer. With the increasing incidence of NMTC in recent years, the familial form of the disease has also become more common than previously reported, accounting for 5-15% of NMTC cases. Familial NMTC is further classified as non-syndromic and the less common syndromic FNMTC. Although syndromic NMTC has well-known genetic risk factors, the gene(s) responsible for the vast majority of non-syndromic FNMTC cases are yet to be identified. To date, several candidate genes have been identified as susceptibility genes in hereditary NMTC. This review summarizes genetic predisposition to non-medullary thyroid cancer and expands on the role of genetic variants in thyroid cancer tumorigenesis and the level of penetrance of NMTC-susceptibility genes.

Susceptibility Genes and Chromosomal Regions Associated With Non-Syndromic Familial Non-Medullary Thyroid Carcinoma: Some Pathogenetic and Diagnostic Keys

Thyroid cancer is the malignant tumor that is increasing most rapidly in the world, mainly at the expense of sporadic papillary thyroid carcinoma. The somatic alterations involved in the pathogenesis of sporadic follicular cell derived tumors are well recognized, while the predisposing alterations implicated in hereditary follicular tumors are less well known. Since the genetic background of syndromic familial non-medullary carcinoma has been well established, here we review the pathogenesis of non-syndromic familial non-medullary carcinoma emphasizing those aspects that may be useful in clinical and pathological diagnosis. Non-syndromic familial non-medullary carcinoma has a complex and heterogeneous genetic basis involving several genes and loci with a monogenic or polygenic inheritance model. Most cases are papillary thyroid carcinoma (classic and follicular variant), usually accompanied by benign thyroid nodules (follicular thyroid adenoma and/or multinodular goiter). The possible diagnostic and prognostic usefulness of the changes in the expression and/or translocation of various proteins secondary to several mutations reported in this setting requires further confirmation. Given that non-syndromic familial non-medullary carcinoma and sporadic non-medullary thyroid carcinoma share the same morphology and somatic mutations, the same targeted therapies could be used at present, if necessary, until more specific targeted treatments become available.

Familial follicular cell thyroid carcinomas in a large number of Dutch German longhaired pointers

Thyroid carcinomas (TCs) originating from follicular cells of the thyroid gland occur in both humans and dogs, and they have highly similar histomorphologic patterns. In dogs, TCs have not been extensively investigated, especially concerning the familial origin of TCs. Here, we report familial thyroid follicular cell carcinomas (FCCs) confirmed by histology in 54 Dutch origin German longhaired pointers. From the pedigree, 45 of 54 histopathologically confirmed cases are closely related to a pair of first‐half cousins in the past, indicating a familial disease. In addition, genetics contributed more to the thyroid FCC than other factors by an estimated heritability of 0.62 based on pedigree. The age of diagnosis ranged between 4.5 and 13.5 years, and 76% of cases were diagnosed before 10 years of age, implying an early onset of disease. We observed a significant higher pedigree‐based inbreeding coefficient in the affected dogs (mean F, 0.23) compared to unaffected dogs (mean F, 0.14), suggesting the contribution of inbreeding to tumour development. The unique occurrence of familial thyroid FCC in this dog population and the large number of affected dogs make this population an important model to identify the genetic basis of familial thyroid FCC in this breed and may contribute to the research into pathogenesis, prevention and treatment in humans.

Familial non medullary thyroid carcinoma: Beyond the syndromic forms

Familial non-medullary thyroid cancer is defined as the presence of non-medullary thyroid cancer in two or more first-degree relatives, in the absence of other predisposing factors. It represents up to 9% of differentiated thyroid cancers, and only a minority appears in well-known hereditary syndromes that associate thyroid cancer among many other clinical manifestations. However, in more than 95% of cases, thyroid cancer appears isolated, and its genetic causes have yet to be elucidated. We review here the current knowledge of the genetic basis of this pathology, as well as its clinical characteristics. Understanding the genetic mechanisms implied would help to comprehend the metabolic pathways involved, with the consequent potential therapeutic application. In addition, it would allow genetic counseling and to focus our efforts on patients at risk of developing this disorder.

Non-medullary Thyroid Cancer Susceptibility Genes: Evidence and Disease Spectrum

BACKGROUND

The prevalence of non-medullary thyroid cancer (NMTC) is increasing worldwide. Although most NMTCs grow slowly, conventional therapies are less effective in advanced tumors. Approximately 5-15% of NMTCs have a significant germline genetic component. Awareness of the NMTC susceptibility genes may lead to earlier diagnosis and better cancer prevention.

OBJECTIVE

The aim of this study was to provide the current panorama of susceptibility genes associated with NMTC and the spectrum of diseases associated with these genes.

METHODS

Twenty-five candidate genes were identified by searching for relevant studies in PubMed. Each candidate gene was carefully checked using six authoritative genetic resources: ClinGen, National Comprehensive Cancer Network guidelines, Online Mendelian Inheritance in Man, Genetics Home Reference, GeneCards, and Gene-NCBI, and a validated natural language processing (NLP)-based literature review protocol was used to further assess gene-disease associations where there was ambiguity.

RESULTS

Among 25 candidate genes, 10 (APC, DICER1, FOXE1, HABP2, NKX2-1, PRKAR1A, PTEN, SDHB, SDHD, and SRGAP1) were verified among the six genetic resources. Two additional genes, CHEK2 and SEC23B, were verified using the NLP protocol. Seventy-nine diseases were found to be associated with these 12 NMTC susceptibility genes. The following diseases were associated with more than one NMTC susceptibility gene: colorectal cancer, breast cancer, gastric cancer, kidney cancer, gastrointestinal stromal tumor, paraganglioma, pheochromocytoma, and benign skin conditions.

CONCLUSION

Twelve genes predisposing to NMTC and their associated disease spectra were identified and verified. Clinicians should be aware that patients with certain pathogenic variants may require more aggressive surveillance beyond their thyroid cancer risk.

Clinical and Genetic Features of a Large Monocentric Series of Familial Non-Medullary Thyroid Cancers

Several low penetration susceptibility risk loci or genes have been proposed in recent years with a possible causative role for familial non-medullary thyroid cancer (FNMTC), though the results are still not conclusive or reliable. Among all the candidates, here fully reviewed, a new extremely rare germline variant c.3607A>G (p.Y1203H) of the DUOX2 gene, has been recently reported to co-segregate with the affected members of one non-syndromic FNMTC family. We aimed to validate this finding in our series of 33 unrelated FNMTC Italian families, previously found to be negative for two susceptibility germline variants in the HABP2 and MAP2K5 genes. Unfortunately, the DUOX2 p.Y1203H variant was not found in either the 74 affected or the 12 not affected family members of our series. We obtained interesting data by comparing the clinico-pathological data of the affected members of our kindreds with a large consecutive series of sporadic cases, followed at our site. We found that familial tumors had a statistically significant more aggressive presentation at diagnosis, though not resulting in a worst outcome. In conclusion, we report genetic and clinical data in a large series of FNMTC kindreds. Our families are negative for variants reported as likely causative, namely those lying in the HABP2, MAP2K5 and DUOX2 genes. The extensive review of the current knowledge on the genetic risk factors for non-syndromic FNMTCs underlies how the management of these tumors remains mainly clinical. Despite the more aggressive presentation of familial cases, an appropriate treatment leads to an outcome similar to that observed for sporadic cases.

BROX haploinsufficiency in familial nonmedullary thyroid cancer

BACKGROUND

The familial nonmedullary thyroid cancer (FNMTC) is suspected to be a Mendelian condition in up to 3-8% of thyroid cancers. The susceptibility chromosomal loci and genes of 95% of FNMTC cases remain to be characterized. The inheritance of FNMTC appears to be autosomal dominant with incomplete penetrance and variable expressivity. The finding of the causative gene of FNMTC and the identification of patients at risk that need genetic testing were our aim.

METHODS

We analyzed by whole-exome sequencing patients and non-affected relatives of five families with at least two family members affected by papillary thyroid cancer, selecting for new or extremely rare variants with predicted pathogenic value.

RESULTS

A family showed, in all three affected members, a new loss-of-function variant (frameshift deletion) in BROX gene at 1q41 that was absent from all internal and external databases. In a second family with three affected relatives, we found an additional new BROX variant. The smaller families presented no variants in BROX or in the other causative genes studied.

CONCLUSIONS

BROX could be a new causative gene for FNMTC. Variants in BROX may result in the haploinsufficiency of a key gene involved in the morphogenesis of MVBs, in the endosomal sorting of cargo proteins, and in EGFR. Functional studies are needed to support this result. The thorough genomic analysis by NGS in all families with three or more affected members should become a routine approach to obtain a comprehensive genetic view and find confirmative second cases.

Familial non medullary thyroid carcinoma: Beyond the syndromic forms

Familial non-medullary thyroid cancer is defined as the presence of non-medullary thyroid cancer in two or more first-degree relatives, in the absence of other predisposing factors. It represents up to 9% of differentiated thyroid cancers, and only a minority appears in well-known hereditary syndromes that associate thyroid cancer among many other clinical manifestations. However, in more than 95% of cases, thyroid cancer appears isolated, and its genetic causes have yet to be elucidated. We review here the current knowledge of the genetic basis of this pathology, as well as its clinical characteristics. Understanding the genetic mechanisms implied would help to comprehend the metabolic pathways involved, with the consequent potential therapeutic application. In addition, it would allow genetic counseling and to focus our efforts on patients at risk of developing this disorder.

Familial non-medullary thyroid carcinoma: clinico-pathological features, current knowledge and novelty regarding genetic risk factors

Familial non-medullary thyroid cancer (FNMTC) constitutes 3-9% of all thyroid cancers and occurs in two or more first-degree relatives in the absence of predisposing environmental factors. Out of all FNMTC cases, only 5% are represented by syndromic forms (Gardner's Syndrome, familial adenomatous polyposis, Cowden's Syndrome, Carney complex 1, Werner's Syndrome and DICER1 syndrome), in which thyroid cancer occurs as a minor component and the genetic alterations are well-known. The non-syndromic forms represent the majority of all FNMTCs (95%), and the thyroid cancer is the predominant feature. Several low penetration susceptibility risk loci or genes (i.e. TTF1, FOXE1, SRGAP1, SRRM2, HABP2, MAP2K5, and DUOX2), here fully reviewed, have been proposed in recent years with a possible causative role, though the results are still not conclusive or reliable. FNMTC is indistinguishable from sporadic non-medullary thyroid cancer (sNMTC), which means that FNMTC cannot be diagnosed until at least one of the patient's first-degree relatives is affected by tumor. Some studies reported that the non-syndromic FNMTC is more aggressive than the sNMTC, being characterized by a younger age of onset and a higher rate of multifocal and bilateral tumors, extrathyroidal extension, lymph node metastasis, and recurrence. On the contrary, other studies did not find clinical differences between non-syndromic FNMTCs and sporadic cases. Here, I reported an extensive review on genetic and clinico-pathological features of the FNMTC, with particular attention on novel genetic risk factors for non-syndromic forms.

Diagnostic and prognostic value of HABP2 as a novel biomarker for endometrial cancer

BACKGROUND

Endometrial cancer is the fifth most common malignant disorder in women, with its incidence increasing. A biomarker with diagnostic and prognostic value remains to be found. The HABP2 protein, or Factor VII-activating protease, encodes a hyaluronic acid-binding protein.

METHODS

Patient data including clinical characteristics and RNAseq information of HABP2 was obtained from The Cancer Genome Atlas (TCGA), and analyzed by R statistic packages. A total of 370 women with endometrial cancer were enrolled in the study. To study the diagnostic value of HABP2 in patients with endometrial cancer, receiver operating characteristic (ROC) curves were plotted by the pROC package. To study the prognostic value of HABP2 in patients with endometrial cancer, the survival package in R was used and the Cox model was established.

RESULTS

HABP2 expression was lower in endometrial cancer compared with normal endometrial tissues. HABP2 showed moderate diagnostic value for endometrial cancer, with HBP2 expression associated with vital status, histologic grade, and residual tumor. HABP2 was an independent prognostic factor, with low HABP2 expression indicating a better overall survival.

CONCLUSIONS

HABP2 has diagnostic and prognostic value and maybe a novel biomarker for endometrial cancer.

Current Knowledge of Germline Genetic Risk Factors for the Development of Non-Medullary Thyroid Cancer

The thyroid is the most common site of endocrine cancer. One type of thyroid cancer, non-medullary thyroid cancer (NMTC), develops from follicular cells and represents approximately 90% of all thyroid cancers. Approximately 5%–15% of NMTC cases are thought to be of familial origin (FNMTC), which is defined as the occurrence of the disease in three or more first-degree relatives of the patient. It is often divided into two groups: Syndrome-associated and non-syndromic. The associated syndromes include Cowden syndrome, familial adenomatous polyposis, Gardner syndrome, Carney complex and Werner syndrome. The hereditary factors contributing to the unfavorable course of FNMTC remain poorly understood; therefore, considerable effort is being expended to identify contributing loci. Research carried out to date identifies fourteen genes (DICER1, FOXE1, PTCSC2, MYH9, SRGAP1, HABP2, BRCA1, CHEK2, ATM, RASAL1, SRRM2, XRCC1, TITF-1/NKX2.1, PTCSC3) associated with vulnerability to FNMTC that are not related to hereditary syndromes. In this review, we summarize FNMTC studies to date, and provide information on genes involved in the development of non-syndromic familial non-medullary thyroid cancers, and the significance of mutations in these genes as risk factors. Moreover, we discuss whether the genetic polymorphism rs966423 in DIRC3 has any potential as a prognostic factor of papillary thyroid cancer.

Targeted next-generation sequencing in papillary thyroid carcinoma patients looking for germline variants predisposing to the disease

PURPOSESS

The purpose of this study was using next-generation sequencing technique to explore the potential association between germline variants of 14 targeted genes and papillary thyroid carcinoma (PTC) predisposition as well as disease progression.

METHODS

In all, 516 subjects were enrolled in this study including 416 PTC patients and 100 healthy controls. PTC patients were divided into distant metastasis group and non-distant metastasis group. Patients in distant metastasis group were further divided into radioiodine-refractory PTC (RR-PTC) and non-RR-PTC depending on their response to radioiodine therapy. Genomic DNA was extracted from peripheral blood sample and MiSeq Benchtop Sequencer was used for sequencing.

RESULTS

We found rs11246050 in NLRP6 (dominant model, OR/95% CI: 2.028/1.091-3.769, p = 0.025), rs2286742 and rs3740530 in HABP2 (recessive model, OR/95% CI: 9.644/1.307-71.16, p = 0.026 and 3.989/1.413-11.26, p = 0.009), rs2736098 in TERT (recessive model, OR/95% CI: 2.322/1.028-5.242. p = 0.042) and rs62054619 in GAS8-AS1 (recessive model, OR/95% CI: 2.219/1.067-4.617, p = 0.033) were associated with the risk of PTC. rs1137282 in KRAS (dominant model, OR/95% CI: 0.5430/0.3192-0.9236, p = 0.024), rs1347591 and rs4461062 in NUP93 (dominant model, OR/95% CI: 0.6121/0.4128-0.9076, p = 0.015 and 0.6156/0.4157-0.9117, p = 0.015) were associated with low risk of distant metastatic disease in PTC patients. rs33954691 in TERT was associated with the risk of RR-PTC under dominant model (OR/95% CI: 3.161/1.596-6.262).

CONCLUSIONS

Germline variants of related genes could be associated with the susceptibility of PTC as well as disease progression (distant metastasis and radioiodine-refractory status). However, these results must be further verified and the potential biological functions of these germline variants in the pathogenesis of PTC remain to be determined in future studies.

Frequent and Rare HABP2 Variants Are Not Associated with Increased Susceptibility to Familial Nonmedullary Thyroid Carcinoma in the Spanish Population

BACKGROUND/AIMS

A genomic HABP2 variant was proposed to be responsible for familial nonmedullary thyroid carcinoma (FNMTC). However, its involvement has been questioned in subsequent studies. We aimed to identify genetic HABP2 mutations in a series of FNMTC patients and investigate their involvement in the disease.

METHODS

HABP2 was sequenced from 6 index patients. Presence of the variants was investigated in all members of one family. Somatic BRAF and RAS "hotspot" mutations were investigated by the IdyllaTM BRAF Mutation Test and/or Sanger sequencing.

RESULTS

Two HABP2 variants (p.E393Q and p.G534E) were identified in the index patient from one family with papillary thyroid carcinoma (PTC) (follicular variant). The prevalence of p.E393Q in Spanish control alleles was 0.5% and that of p.G534E was 5.1%. However, neither change cosegregated with the phenotype in 3 affected members and 5 healthy members of the kindred. Interestingly, all 3 members affected by PTC harbored the p.V600E somatic mutation in BRAF.

CONCLUSIONS

The variant G534E is prevalent in the Spanish population (5.1%); however, p.E393Q is rare (< 1%) and none cosegregated with the FNMTC phenotype. The presence of the noninheritable V600E BRAF mutation in this family supports Knudson's "double-hit" hypothesis for cancer development and suggests the involvement of more than 1 gene in the clinical expression of FNMTC.

Whole exome and target sequencing identifies MAP2K5 as novel susceptibility gene for familial non-medullary thyroid carcinoma

Although the genotype-phenotype for familial medullary thyroid carcinoma (FMTC) is well studied, only few low susceptibility risk loci were identified for familial non-medullary thyroid carcinoma (FNMTC). The aim of this study is to screen and identify high-penetrate genes for FNMTC. A total of 34 families with more than two first-degree relatives diagnosed as papillary thyroid cancer without other familial syndrome were recruited. Whole exome and target gene sequencing were performed for candidate variants. These variants were screened and analyzed with ESP6500, ExAC, 1000 genomes project, and the Cancer Genome Atlas (TCGA) with SIFT score and Polyphen2 prediction. Finally, we identified recurrent genetic mutation of MAP2K5 variants c.G961A and c.T1100C (p. A321T and p.M367 T) as susceptibility loci for FNMTC. The frequencies of MAP2K5 c.G961A and c.T1100C were found, 0.0385 and 0.0259 in FNMTC and 0 and 0.00022523 in healthy Chinese controls (n = 2200, P < 0.001), respectively. Both variants were located in the protein kinase domain. The functional study showed that MAP2K5 A321T or M367 T could consistently phosphorylate downstream protein ERK5 on site Ser731 + Thr733 or Ser496, promoting nuclear translocation and subsequently altering target gene expressions. Our data revealed that MAP2K5 variants A321T or M367 T can activate MAP2K5-ERK5 pathway, alter downstream gene expression, and subsequently induce thyroid epithelial cell malignant transformation. While classic MAP2K1/2(MEK1/2)-ERK1/2 signaling is well known for driving sporadic NMTC, our research indicated that MAP2K5 (MEK5) is a susceptibility gene for FNMTC. These findings highlight the potential application of MAP2K5 for molecular diagnosis as well as early prevention.

The p.G534E variant of HABP2 is not associated with sporadic papillary thyroid carcinoma in a Polish population

Thyroid cancer is one of the most frequently diagnosed cancers of the endocrine system. There are no known genetic risk factors for non-medullary thyroid cancer, other than a small number of hereditary syndromes; however, approximately 5% of non-medullary thyroid cancer, designated familial non-medullary thyroid cancer, exhibits heritability. The p.G534E (c.1601G>A) variant of HABP2 was recently reported as a risk factor for familial non-medullary thyroid cancer, including papillary thyroid carcinoma. We analyzed the incidence of the c.1601G>A variant of HABP2 in a Polish population consisting of 326 cases of papillary thyroid carcinoma and 400 control individuals by DNA genotyping, performed by Sanger sequencing. The c.1601G>A variant was detected in 3.7% of sporadic papillary thyroid carcinoma cases and 4.7% of healthy controls, and we did not detect an association between this variant and sporadic papillary thyroid carcinoma risk (OR = 0.71, 95% CI: 0.33-1.51; p = 0.3758). Additionally, no significant associations were identified between clinical and pathological disease features, response to primary treatment, and clinical status at the end of the observation, and HABP2 c.1601G>A genotype. In conclusion, the p.G534E variant of HABP2 is not associated with sporadic papillary thyroid carcinoma risk in the Polish population.

Letter regarding the article: "Multiple HABP2 variants in familial papillary thyroid carcinoma: Contribution of a group of "thyroid-checked" controls" by Kern et al

This Journal recently published a study (Kern et al., 2017) reporting the genetic analysis of the whole HABP2 gene in 11 independent kindreds with familial non medullary thyroid cancer (FNMTC). The Authors showed that a new variant (p.R122W) displayed a minor allele frequency (MAF) significantly higher in FNMTC patients than in controls (7.5 vs 0.73%, p = 0.016) and cosegregated with thyroid cancer in one kindred, thus suggesting the need for the evaluation of its possible pathogenicity in other series. We thus analyzed this new HABP2 p.R122W variant in our wide series of 32 unrelated FNMTC Italian kindreds. The variant was not found in any of the 72 affected and 12 not affected family members. In conclusion, the HABP2^R122W was not found in our wide series and it is thus unlikely to be causal to FNMTC. We therefore suggest that careful replication studies should be performed when assessing the possible association between FNMTC risk and any HABP2 variant.

HABP2 p.G534E variant in patients with family history of thyroid and breast cancer

Familial Papillary Thyroid Carcinoma (PTC) has been described as a hereditary predisposition cancer syndrome associated with mutations in candidate genes including HABP2. Two of 20 probands from families with history of PTC and breast carcinoma (BC) were evaluated by whole exome sequencing (WES) revealing HABP2 p.G534E. Sanger sequencing was used to confirm the involvement of this variant in three families (F1: 7 relatives; F2: 3 and F3: 3). The proband and his sister (with no malignant tumor so far) from F1 were homozygous for the variant whereas one relative with PTC from F2 was negative for the variant. Although the proband of the F3 with PTC was HABP2 wild type, three relatives presented the variant. Five of 170 healthy Brazilian individuals with no family history of BC or PTC and three of 50 sporadic PTC presented the p.G534E. These findings suggested no association of this variant with our familial PTC cases. Genes potentially associated with deregulation of the extracellular matrix organization pathway (CTSB, TNXB, COL4A3, COL16A1, COL24A1, COL5A2, NID1, LOXL2, MMP11, TRIM24 and MUSK) and DNA repair function (NBN and MSH2) were detected by WES, suggesting that other cancer-associated genes have pathogenic effects in the risk of familial PTC development.

Segregation and expression analyses of hyaluronan-binding protein 2 (HABP2): insights from a large series of familial non-medullary thyroid cancers and literature review

INTRODUCTION

Recently, the G534E variant of the HABP2 gene was reported as the underlying genetic defect in a large kindred with nonsyndromic familial nonmedullary thyroid cancer (FNMTC). Nevertheless, this postulated role was not confirmed in additional cohorts. Contrasting data are also available on HABP2 expression in the thyroid.

OBJECTIVES

To investigate HABP2 as a potential susceptibility gene in a large series of 27 unrelated families with FNMTC and to test its expression in thyroid tumour and matched normal tissues.

RESULTS

Three of the 27 FNMTC families (11·1%) carried the HABP2^G534E variant. The genotyping of these families showed that HABP2^G534E does not segregate with cancer. Indeed, affected individuals not carrying HABP2^G534E were identified, and the variant was present also in members without thyroid cancer. HABP2 mRNA had a very variable expression in tissues from FNMTC, sporadic papillary thyroid cancers (PTCs) or contralateral normal tissues, by either nonquantitative or quantitative RT-polymerase chain reaction. In almost all cases, the gene appeared down- or up-regulated in tumours with respect to the corresponding normal tissue. At immunohistochemistry, HABP2 was expressed in both tumour and matched control tissues, without differences between sporadic and familial cases.

CONCLUSIONS

This study on a wide series of FNMTC indicates that the HABP2^G534E variant is frequent, but does not segregate with the disease. Nevertheless, the dysregulation of HABP2 expression found in either sporadic or familial PTCs or normal thyroid tissues is consistent with similar findings in other malignancies and could indicate a role of this gene also in thyroid cancer.

HABP2 G534E variation in familial non-medullary thyroid cancer: an Italian series

INTRODUCTION

Thyroid cancer may have a familial predisposition and may occur in the context of hereditary syndromes or as isolated tumor. Recently, the G534E variant in the HABP2 gene has been suggested as causative mutation for familial thyroid cancer, but other studies gave contradictory results.

METHODS

We have analyzed the G534E variant in an Italian series of 63 familial thyroid cancer patients and 41 unaffected family members with end-point PCR, DHPLC and direct sequencing.

RESULTS

All samples analyzed displayed a pattern typical of the homozygous wild type revealing the absence of the G534E variant.

CONCLUSION

In this study, HABP2 G534E variant is not correlated with the familial form of PTC.

Pitfalls of exome sequencing: a case study of the attribution of HABP2 rs7080536 in familial non-medullary thyroid cancer

Next-generation sequencing using exome capture is a common approach used for analysis of familial cancer syndromes. Despite the development of robust computational algorithms, the accrued experience of analyzing exome data sets and published guidelines, the analytical process remains an ad hoc series of important decisions and interpretations that require significant oversight. Processes and tools used for sequence data generation have matured and are standardized to a significant degree. For the remainder of the analytical pipeline, however, the results can be highly dependent on the choices made and careful review of results. We used primary exome sequence data, generously provided by the corresponding author, from a family with highly penetrant familial non-medullary thyroid cancer reported to be caused by HABP2 rs7080536 to review the importance of several key steps in the application of exome sequencing for discovery of new familial cancer genes. Differences in allele frequencies across populations, probabilities of familial segregation, functional impact predictions, corroborating biological support, and inconsistent replication studies can play major roles in influencing interpretation of results. In the case of HABP2 rs7080536 and familial non-medullary thyroid cancer, these factors led to the conclusion of an association that most data and our re-analysis fail to support, although larger studies from diverse populations will be needed to definitively determine its role.

Familial non-medullary thyroid cancer: unraveling the genetic maze

Familial non-medullary thyroid cancer (FNMTC) constitutes 3-9% of all thyroid cancers. Out of all FNMTC cases, only 5% in the syndromic form has well-studied driver germline mutations. These associated syndromes include Cowden syndrome, familial adenomatous polyposis, Gardner syndrome, Carney complex type 1, Werner syndrome and DICER1 syndrome. It is important for the clinician to recognize these phenotypes so that genetic counseling and testing can be initiated to enable surveillance for associated malignancies and genetic testing of family members. The susceptibility chromosomal loci and genes of 95% of FNMTC cases remain to be characterized. To date, 4 susceptibility genes have been identified (SRGAP1 gene (12q14), TITF-1/NKX2.1 gene (14q13), FOXE1 gene (9q22.33) and HABP2 gene (10q25.3)), out of which only the FOXE1 and the HABP2 genes have been validated by separate study groups. The causal genes located at the other 7 FNMTC-associated chromosomal loci (TCO (19q13.2), fPTC/ PRN (1q21), FTEN (8p23.1-p22), NMTC1 (2q21), MNG1 (14q32), 6q22, 8q24) have yet to be identified. Increasingly, gene regulatory mechanisms (miRNA and enhancer elements) are recognized to affect gene expression and FNMTC tumorigenesis. With newer sequencing technique, along with functional studies, there has been progress in the understanding of the genetic basis of FNMTC. In our review, we summarize the FNMTC studies to date and provide an update on the recently reported susceptibility genes including novel germline SEC23B variant in Cowden syndrome, SRGAP1 gene, FOXE1 gene and HABP2 genes in non-syndromic FNMTC.

HABP2 germline variants are uncommon in familial nonmedullary thyroid cancer

Background

The genetic basis of nonsyndromic familial nonmedullary thyroid cancer (FNMTC) is poorly understood. A recent study identified HABP2 as a tumor suppressor gene and identified a germline variant (G534E) in an extended FNMTC kindred. The relevance of this to other FNMTC kindreds is uncertain.

Methods

Sanger sequencing was performed on peripheral blood DNA from probands from 37 Australian FNMTC kindreds to detect the G534E variant. Whole exome data from 59 participants from 20 kindreds were examined for mutations in HABP2 and the thyroid cancer susceptibility genes SRGAP1, NKX2-1, SRRM2 and FOXE1. The population prevalence of the G534E variant in HABP2 was examined in two independent cohorts.

Results

Heterozygosity for the G534E variant in HABP2 was found in 1 of 37 probands (2.7 %), but did not cosegregate with disease in this kindred, being absent in the proband’s affected sister. From whole exome data, pathogenic mutations were not identified in HABP2, SRGAP1, NKX2-1, SRRM2 or FOXE1. Heterozygosity for the G534E variant in HABP2 was present in 7.6 % of Busselton Health Study participants (N = 4634, unknown disease status) and 9.3 % of TwinsUK participants (N = 1195, no history of thyroid cancer).

Conclusions

The G534E variant in HABP2 does not account for the familial nature of NMTC in Australian kindreds, and is common in the general population. Further research is required to elucidate the genetic basis of nonsyndromic FNMTC.

The impact of family history on non-medullary thyroid cancer

INTRODUCTION

Around 10% of patients with non-medullary thyroid cancer (NMTC) will have a positive family history for the disease. Although many will be sporadic, families where 3 first-degree relatives are affected can be considered to represent true familial non-medullary thyroid cancer (FNMTC). The genetic basis, impact on clinical and pathological features, and overall effect on prognosis are poorly understood.

METHODS

A literature review identified articles which report on genetic, clinical, therapeutic and screening aspects of FNMTC. The results are presented to allow an understanding of the genetic basis and the impact on clinical-pathological features and prognosis in order to inform clinical decision making.

RESULTS

The genetic basis of FNMTC is unknown. Despite this, significant progress has been made in identifying potential susceptibility genes. The lack of a test for FNMTC has led to a clinical definition requiring a minimum of 3 first-degree relatives to be diagnosed with NMTC. Although some have shown an association with multi-centric disease, younger age and increased rates of extra-thyroidal extension and nodal metastases, these findings are not supported by all. The impact of FNMTC is unclear with all groups reporting good outcome, and some finding an association with more aggressive disease. The role of screening remains controversial.

CONCLUSION

FNMTC is rare but can be diagnosed clinically. Its impact on prognostic factors and the subsequent role in influencing management is debated. For those patients who present with otherwise low-risk differentiated thyroid cancer, FNMTC should be included in risk assessment when discussing therapeutic options.