POT1 germline mutations but not TERT promoter mutations are implicated in melanoma susceptibility in a large cohort of Spanish melanoma families

Identification of P21 (CDKN1A) Activated Kinase 4 as a Susceptibility Gene for Familial Non-Medullary Thyroid Carcinoma

Background: Familial non-medullary thyroid carcinoma (FNMTC) is a genetically predisposed disease with unclear genetic mechanisms. This makes research on susceptibility genes important for the diagnosis and treatment options. Methods: This study included a five-member family affected by papillary thyroid carcinoma. The candidate genes were identified through whole-exome sequencing and Sanger sequencing in family members, other FNMTC patients, and sporadic non-medullary thyroid carcinoma patients. The pathogenicity of the mutation was predicted using in silico tools. Cell phenotype experiments in vitro and models of lung distant metastasis in vivo were conducted to confirm the characteristics of the mutation. Transcriptome sequencing and mechanistic validation were employed to compare the disparities between PAK4 wild-type (WT) and PAK4 mutant (MUT) cell lines. Results: This mutation alters the protein structure, potentially increasing instability by affecting hydrophobicity, intra-molecular hydrogen bonding, and phosphorylation sites. It specifically promotes phosphorylated PAK4 nuclear translocation and expression in thyroid tissue and cell lines. Compared with the WT cells line, PAK4 I417T demonstrates enhanced proliferation, invasiveness, accelerated cell division, and inhibition of cell apoptosis in vitro. In addition, it exhibits a significant propensity for metastasis in vivo. It activates tumor necrosis factor signaling through increased phosphorylation of PAK4, JNK, NFκB, and c-Jun, unlike the WT that activates it via the PAK4-NFκ-MMP9 axis. In addition, PAK4 MUT protein interacts with matrix metalloproteinase (MMP)3 and regulates MMP3 promoter activity, which is not observed in the WT. Conclusions: Our study identified PAK4: c.T1250C: p.I417T as a potential susceptibility gene for FNMTC. The study concludes that the mutant form of PAK4 exhibits oncogenic function, suggesting its potential as a novel diagnostic molecular marker for FNMTC.

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.

Association between thyroid disorders and extra-thyroidal cancers, a review

Thyroid hormone has been shown to have both tumor-promoting and tumor-suppressing actions, which has led to significant debate over its involvement in the development of cancer. Proliferation, apoptosis, invasiveness, and angiogenesis are all aspects of cancer that are affected by the thyroid hormones T3 and T4, according to research conducted in animal models and in vitro experiments. The effects of thyroid hormones on cancer cells are mediated by many non-genomic mechanisms, one of which involves the activation of the plasma membrane receptor integrin αvβ3. Typically, abnormal amounts of thyroid hormones are linked to a higher occurrence of cancer. Both benign and malignant thyroid disorders were found to be associated with an increased risk of extra-thyroidal malignancies, specifically colon, breast, prostate, melanoma, and lung cancers. The purpose of this review was to shed light on this link to define which types of cancer are sensitive to thyroid hormones and, as a result, are anticipated to respond favorably to treatment of the thyroid hormone axis.

Cutaneous malignancies in chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is a common lymphoid malignancy that is associated with an increased risk of developing cutaneous malignancies. Clinical outcomes for these malignancies, including melanoma and keratinocyte cancers (KC), are worse for patients with CLL. Individuals with CLL develop an immunodeficiency of both the adaptive and innate immune system, which plays a role in the increased prevalence of skin cancers. This review focuses on the complex interplay between genetics, immunity, and pathogens that influence the cellular composition and biology of skin tumors and their microenvironment in CLL patients, and in comparison with other chronic hematological malignancies. It is paramount for dermatologists to be aware of the association between CLL (and chronic hematological malignancies more broadly) and cutaneous malignancies. This is a high-risk population who require regular and vigorous dermatologic follow-up.

Prognosis of CDKN2A germline mutation in patients with familial melanoma: a systematic review and meta-analysis

Familial melanoma is defined as melanoma occurring in two or more first-degree relatives by the WHO. Germline mutations are isolated in a subset of them. It is well known that CDKN2A is the most frequently mutated high-risk gene in familial melanoma, however, the prognosis it confers to patients who carry its mutations is still controversial. This review aims to assess whether germline mutations imply a worse prognosis in patients with familial melanoma. A systematic review and meta-analysis were conducted by searching the electronic databases PubMed/MEDLINE, EMBASE, and Cochrane Library. Data from 3 independent populations were eventually included in the meta-analysis, involving 291 cases and 57 416 controls. The results of this systematic review and meta-analysis suggest that there is a tendency for patients with germline mutations in the CDKN2A gene to have a worse overall survival (HR = 1.30, 95% CI = 0.99-1.69, P  = 0.05) and melanoma-specific survival (HR = 1.5, 95% CI = 0.97-2.31, P  = 0.07). Carrier patients would not only have more incidence of melanoma and a higher risk of a second melanoma, but they also seem to have a worse prognosis. The inclusion of gene panel testing in clinical practice and the collaboration within consortia are needed to provide further evidence on the prognosis of these patients.

Characterization of Potential Melanoma Predisposition Genes in High-Risk Brazilian Patients

Increased genetic risk for melanoma can occur in the context of germline pathogenic variants in high-penetrance genes, such as CDKN2A and CDK4, risk variants in low- to moderate-penetrance genes (MC1R and MITF), and possibly due to variants in emerging genes, such as ACD, TERF2IP, and TERT. We aimed to identify germline variants in high- and low- to moderate-penetrance melanoma risk genes in Brazilian patients with clinical criteria for familial melanoma syndrome. We selected patients with three or more melanomas or melanoma patients from families with three tumors (melanoma and pancreatic cancer) in first- or second-degree relatives. Genetic testing was performed with a nine-gene panel (ACD, BAP1, CDK4, CDKN2A, POT1, TERT, TERF2IP, MC1R, and MITF). In 36 patients, we identified 2 (5.6%) with germline pathogenic variants in CDKN2A and BAP1 and 4 (11.1%) with variants of uncertain significance in the high-penetrance genes. MC1R variants were found in 86.5%, and both red hair color variants and unknown risk variants were enriched in patients compared to a control group. The low frequency of germline pathogenic variants in the high-penetrance genes and the high prevalence of MC1R variants found in our cohort show the importance of the MC1R genotype in determining the risk of melanoma in the Brazilian melanoma-prone families.

TINF2 is a major susceptibility gene in Danish patients with multiple primary melanoma

TINF2 encodes the TINF2 protein, which is a subunit in the shelterin complex critical for telomere regulation. Three recent studies have associated six truncating germline variants in TINF2 that have previously been associated with a cancer predisposition syndrome (CPS) caused by elongation of the telomeres. This has added TINF2 to the long telomere syndrome genes, together with other telomere maintenance genes such as ACD, POT1, TERF2IP, and TERT. We report a clinical study of 102 Danish patients with multiple primary melanoma (MPM) in which a germline truncating variant in TINF2 (p.(Arg265Ter)) was identified in four unrelated participants. The telomere lengths of three variant carriers were >90% percentile. In a routine diagnostic setting, the variant was identified in two more families, including an additional MPM patient and monozygotic twins with thyroid cancer and other cancer types. A total of 10 individuals from six independent families were confirmed carriers, all with cancer history, predominantly melanoma. Our findings suggest a major role of TINF2 in Danish patients with MPM. In addition to melanoma, other cancers in the six families include thyroid, renal, breast, and sarcoma, supporting a CPS in which melanoma, thyroid cancer, and sarcoma predominate. Further studies are needed to establish the full spectrum of associated cancer types and characterize lifetime cancer risk in carriers.

Population-based analysis of POT1 variants in a cutaneous melanoma case-control cohort

Pathogenic germline variants in the protection of telomeres 1 gene (POT1) have been associated with predisposition to a range of tumour types, including melanoma, glioma, leukaemia and cardiac angiosarcoma. We sequenced all coding exons of the POT1 gene in 2928 European-descent melanoma cases and 3298 controls, identifying 43 protein-changing genetic variants. We performed POT1-telomere binding assays for all missense and stop-gained variants, finding nine variants that impair or disrupt protein-telomere complex formation, and we further define the role of variants in the regulation of telomere length and complex formation through molecular dynamics simulations. We determine that POT1 coding variants are a minor contributor to melanoma burden in the general population, with only about 0.5% of melanoma cases carrying germline pathogenic variants in this gene, but should be screened in individuals with a strong family history of melanoma and/or multiple malignancies.

Association of germline variants in telomere maintenance genes (POT1, TERF2IP, ACD, and TERT) with spitzoid morphology in familial melanoma: A multi-center case series

Background

Spitzoid morphology in familial melanoma has been associated with germline variants in POT1, a telomere maintenance gene (TMG), suggesting a link between telomere biology and spitzoid differentiation.

Objective

To assess if familial melanoma cases associated with germline variants in TMG (POT1, ACD, TERF2IP, and TERT) commonly exhibit spitzoid morphology.

Methods

In this case series, melanomas were classified as having spitzoid morphology if at least 3 of 4 dermatopathologists reported this finding in ≥25% of tumor cells. Logistic regression was used to calculate odds ratios (OR) of spitzoid morphology compared to familial melanomas from unmatched noncarriers that were previously reviewed by a National Cancer Institute dermatopathologist.

Results

Spitzoid morphology was observed in 77% (23 of 30), 75% (3 of 4), 50% (2 of 4), and 50% (1 of 2) of melanomas from individuals with germline variants in POT1, TERF2IP, ACD, and TERT, respectively. Compared to noncarriers (n = 139 melanomas), POT1 carriers (OR = 225.1, 95% confidence interval: 51.7-980.5; P < .001) and individuals with TERF2IP, ACD, and TERT variants (OR = 82.4, 95% confidence interval: 21.3-494.6; P < .001) had increased odds of spitzoid morphology.

Limitations

Findings may not be generalizable to nonfamilial melanoma cases.

Conclusion

Spitzoid morphology in familial melanoma could suggest germline alteration of TMG.

POT1 mutations cause differential effects on telomere length leading to opposing disease phenotypes

The protection of telomere protein (POT1) is a telomere-binding protein and is an essential component of the six-membered shelterin complex, which is associated with the telomeres. POT1 directly binds to the 3' single-stranded telomeric overhang and prevents the activation of DNA damage response at telomeres thus preventing the telomere-telomere fusions and genomic instability. POT1 also plays a pivotal role in maintaining telomere length by regulating telomerase-mediated telomere elongation. Mutations in POT1 proteins result in three different telomere phenotypes, which include long, short, or aberrant telomere length. Long telomeres predispose individuals to cancer, while short or aberrant telomere phenotypes result in pro-aging diseases referred to as telomeropathies. Here, we review the function of POT1 proteins in telomere length hemostasis and how the spectrum of mutations reported in POT1 can be segregated toward developing very distinct disease phenotypes of cancer and telomeropathies.

UV light-induced dual promoter mutations dismantle the telomeric guardrails in melanoma

Understanding how benign nevi can progress to invasive and metastatic Department of Environmental and Occupational Health, University of Pittsburgh School of Public Health, USAelanoma is critical for developing interventions and therapeutics for this most deadly form of skin cancer. UV-induced mutations in the telomerase TERT gene promoter occur in the majority of melanomas but fail to prevent telomere shortening despite telomerase upregulation. This suggests additional "hits" are required to enable telomere maintenance. A new study in Science identified somatic variants in the promoter of the gene that encodes telomere shelterin protein TPP1 in human melanomas. These variants show mutational signatures of UV-induced DNA damage and upregulate TPP1 expression, which synergizes with telomerase to lengthen telomeres. This study provides evidence that TPP1 promoter variants are a critical second hit to prevent telomere shortening and promote immortalization of melanoma cells.

Melanoma and Glioblastoma-Not a Serendipitous Association

Recently, we came across a patient with malignant melanoma and primary glioblastoma. Given this, we parsed the literature to ascertain the relationship, if any, between these 2 malignancies. We begin with a brief overview of melanoma and glioma in isolation followed by a chronologic overview of case reports and epidemiologic studies documenting both neoplasms. This is followed by studies detailing genetic abnormalities common to both malignancies with a view to identifying unifying genetic targets for therapeutic strategies as well as to explore the possibility of a putative association and an inherited cancer susceptibility trait. From a scientific perspective, we believe we have provided evidence favoring an association between melanoma and glioma. Future studies that include documentation of additional cases, as well as a detailed molecular analyses, will lend credence to our hypothesis that the co-occurrence of these 2 conditions is likely not serendipitous.

Genetic risk factors in melanoma etiopathogenesis and the role of genetic counseling: A concise review

Melanoma is a highly aggressive cancer originating from melanocytes. Its etiopathogenesis is strongly related to genetic, epigenetic, and environmental factors. Melanomas encountered in clinical practice are predominantly sporadic, whereas hereditary melanomas account for approximately 10% of the cases. Hereditary melanomas mainly develop due to mutations in the CDKN2A gene, which encodes two tumor suppressor proteins involved in the cell cycle regulation. CDKN2A, along with CDK4, TERT, and POT1 genes, is a high-risk gene for melanoma. Among the genes that carry a moderate risk are MC1R and MITF, whose protein products are involved in melanin synthesis. The environment also contributes to the development of melanoma. Patients at risk of melanoma should be offered genetic counseling to discuss genetic testing options and the importance of skin UV protection, avoidance of sun exposure, and regular preventive dermatological examinations. Although cancer screening cannot prevent the development of the disease, it allows for early diagnosis when the survival rate is the highest.

Is Melanoma Progression Affected by Thyroid Diseases?

Clinical and epidemiological evidence indicate a relationship between thyroid diseases and melanoma. In particular, the hypothyroidism condition appears to promote melanoma spread, which suggests a protective role of thyroid hormones against disease progression. In addition, experimental data suggest that, in addition to thyroid hormones, other hormonal players of the hypothalamic–pituitary–thyroid (HPT) axis, namely the thyrotropin releasing hormone and the thyrotropin, are likely to affect melanoma cells behavior. This information warrants further clinical and experimental studies in order to build a precise pattern of action of the HPT hormones on melanoma cells. An improved knowledge of the involved molecular mechanism(s) could lead to a better and possibly personalized clinical management of these patients.

POT1 mutations are frequent and associated with Ki-67 index in canine diffuse large B-cell lymphoma

Diffuse large B-cell lymphoma (DLBCL) represents one of the most frequent and deadliest neoplasia in dogs worldwide and is characterized by a remarkable degree of clinical heterogeneity, with poor chances to anticipate the outcome. Even if in the last years some recurrently mutated genes have been identified, the genetic origin of canine DLBCL (cDLBCL) is not yet completely understood. The aim of the present study was to assess the prevalence of POT1 mutations in cDLBCL and to elucidate the role of such gene in the pathogenesis of this tumor. Mutations in POT1 were retrieved in 34% of cases, in line with previous reports, but no significant associations with any clinico-pathological variable were identified. Likewise, POT1 mutations are not predictive of worse prognosis. Interestingly, Ki-67 index was significantly higher in dogs harboring POT1 mutations compared to wild-type ones. These results suggest that POT1 mutations may exert their pathogenic role in cDLBCL by promoting cellular proliferation.

The biology and management of dyskeratosis congenita and related disorders of telomeres

BACKGROUND

Dyskeratosis congenita (DC) is a multisystem syndrome characterized by mucocutaneous abnormalities, bone marrow failure, and predisposition to cancer. Studies over the last 25 years have led to the identification of 18 disease genes. These have a principal role in telomere maintenance, and patients usually have very short/abnormal telomeres. The advances have also led to the unification of DC with a number of other diseases, now collectively referred to as the telomeropathies or telomere biology disorders.

WHAT IS COVERED

Clinical features, genetics, and biology of the different subtypes. Expert view on diagnosis, treatment of the hematological complications and future.

EXPERT VIEW

As these are very pleotropic disorders affecting multiple organs, a high index of suspicion is necessary to make the diagnosis. Telomere length measurement and genetic analysis of the disease genes have become useful diagnostic tools. Although hematological defects can respond to danazol/oxymetholone, the only current curative treatment for these is hematopoietic stem cell transplantation (HSCT) using fludarabine-based conditioning protocols. New therapies are needed where danazol/oxymetholone is ineffective and HSCT is not feasible.

Explore the molecular mechanism of angle-closure glaucoma in elderly patients induced telomere shortening of retinal ganglion cells through oxidative stress

Senile glaucoma is a common ophthalmological disease in the elderly. It is a disease of visual papillary perfusion caused by elevated intraocular pressure, complicated by visual dysfunction. Glaucoma can cause serious damage to the normal vision of the elderly. Therefore, exploring the related molecular mechanisms of glaucoma is of great significance to the diagnosis and treatment of glaucoma. This is an exploratory study. Establish a mouse model and conduct experimental groupings. After one week of adaptive feeding, the mice were intraperitoneally injected with an anesthetic mixture: ketamine + xylazine. Then the mice were sacrificed by neck dissection, and the eyeball tissues were immediately dissected. HE staining was used to analyze the histopathological characteristics of the retina of each group of mice. MitoSOX fluorescent probe was used to analyze the content of ROS in retinal tissue. The ELISA analysis was used to detect the activation of β-galactosidase for the aging characteristics of retinal ganglion cells in retinal tissues. Immunohistochemistry experiments were used to analyze the expression of telomerase TERT in retinal tissues. Western blot analysis was used to determine the expression of proteins POT1, TERF1, TERF2, and TINF2 in retinal tissues. The HE staining experiment showed that the damage of retinal tissue decreased from group Glaucoma to group Old, group Old to group Young. The experimental results of MitoSOX fluorescent probe show that ROS content is positively correlated with the degree of tissue damage. ELISA analysis results showed that the expression trend of β-galactosidase was the same as the ROS content. The protein expression levels related to telomere protection (TRET, POT1, TREF1, TREF2 and TINF2) all increased from group Glaucoma to group Old, group Old to group Young. The increase in ROS content, the decrease in telomere protection-related protein expression (telomere shortening) induced by ROS, and the increase of the expression of β-galactosidase, are all potential molecular mechanisms for the occurrence of angle-closure glaucoma in elderly patients.

Overview of the 2022 WHO Classification of Familial Endocrine Tumor Syndromes

This review of the familial tumor syndromes involving the endocrine organs is focused on discussing the main updates on the upcoming fifth edition of the WHO Classification of Endocrine and Neuroendocrine Tumors. This review emphasizes updates on histopathological and molecular genetics aspects of the most important syndromes involving the endocrine organs. We describe the newly defined Familial Cancer Syndromes as MAFA-related, MEN4, and MEN5 as well as the newly reported pathological findings in DICER1 syndrome. We also describe the updates done at the new WHO on the syndromic and non-syndromic familial thyroid diseases. We emphasize the problem of diagnostic criteria, mention the new genes that are possibly involved in this group, and at the same time, touching upon the role of some immunohistochemical studies that could support the diagnosis of some of these conditions. As pathologists play an important role in identifying tumors within a familial cancer syndrome, we highlight the most important clues for raising the suspicious of a syndrome. Finally, we highlight the challenges in defining these entities as well as determining their clinical outcome in comparison with sporadic tumors. Instead of the usual subject review, we present the highlights of the updates on familial cancer syndromes by answering select questions relevant to practicing pathologists.

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.

Molecular landscape of Hereditary Melanoma

Melanoma is considered the most lethal skin cancer and its incidence has increased during the past decades. About 10 % of cases are classified as hereditary melanoma. Genetic predisposition usually manifests itself clinically as early onset and multiple cutaneous melanomas. Several genes have been identified as involved to melanoma susceptibility, some of them still with unknown clinical relevance. Beyond melanoma, the affected families are also more prone to develop other malignancies, such as pancreatic cancer. The identification of risk families and involved genes is of great importance, since different forms of oncological surveillance are recommended. However, well established guidelines to standardize both the selection of individuals and the genetic panel to be requested are still lacking. Given the importance of the genetic counseling and testing in the context of clinical suspicion of hereditary melanoma, this paper aims to review the literature regarding genetic panel indications worldwide.

Inherited Follicular Epithelial-Derived Thyroid Carcinomas: From Molecular Biology to Histological Correlates

Cancer derived from thyroid follicular epithelial cells is common; it represents the most common endocrine malignancy. The molecular features of sporadic tumors have been clarified in the past decade. However the incidence of familial disease has not been emphasized and is often overlooked in routine practice. A careful clinical documentation of family history or familial syndromes that can be associated with thyroid disease can help identify germline susceptibility-driven thyroid neoplasia. In this review, we summarize a large body of information about both syndromic and non-syndromic familial thyroid carcinomas. A significant number of patients with inherited non-medullary thyroid carcinomas manifest disease that appears to be sporadic disease even in some syndromic cases. The cytomorphology of the tumor(s), molecular immunohistochemistry, the findings in the non-tumorous thyroid parenchyma and other associated lesions may provide insight into the underlying syndromic disorder. However, the increasing evidence of familial predisposition to non-syndromic thyroid cancers is raising questions about the importance of genetics and epigenetics. What appears to be "sporadic" is becoming less often truly so and more often an opportunity to identify and understand novel genetic variants that underlie tumorigenesis. Pathologists must be aware of the unusual morphologic features that should prompt germline screening. Therefore, recognition of harbingers of specific germline susceptibility syndromes can assist in providing information to facilitate early detection to prevent aggressive disease.

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.

Role of POT1 in Human Cancer

Simple Summary

The segmentation of eukaryotic genomes into discrete linear chromosomes requires processes to solve several major biological problems, including prevention of the chromosome ends being recognized as DNA breaks and compensation for the shortening that occurs when linear DNA is replicated. A specialized set of six proteins, collectively referred to as shelterin, is involved in both of these processes, and mutations in several of these are now known to be involved in cancer. Here, we focus on Protection of Telomeres 1 (POT1), the shelterin protein that appears to be most commonly involved in cancer, and consider the clinical significance of findings about its biological functions and the prevalence of inherited and acquired mutations in the POT1 gene.

Abstract

Telomere abnormalities facilitate cancer development by contributing to genomic instability and cellular immortalization. The Protection of Telomeres 1 (POT1) protein is an essential subunit of the shelterin telomere binding complex. It directly binds to single-stranded telomeric DNA, protecting chromosomal ends from an inappropriate DNA damage response, and plays a role in telomere length regulation. Alterations of POT1 have been detected in a range of cancers. Here, we review the biological functions of POT1, the prevalence of POT1 germline and somatic mutations across cancer predisposition syndromes and tumor types, and the dysregulation of POT1 expression in cancers. We propose a framework for understanding how POT1 abnormalities may contribute to oncogenesis in different cell types. Finally, we summarize the clinical implications of POT1 alterations in the germline and in cancer, and possible approaches for the development of targeted cancer therapies.

Candidate genes for hereditary colorectal cancer: Mutational screening and systematic review

Genome-wide approaches applied for the identification of new hereditary colorectal cancer (CRC) genes, identified several potential causal genes, including RPS20, IL12RB1, LIMK2, POLE2, MRE11, POT1, FAN1, WIF1, HNRNPA0, SEMA4A, FOCAD, PTPN12, LRP6, POLQ, BLM, MCM9, and the epigenetic inactivation of PTPRJ. Here we attempted to validate the association between variants in these genes and nonpolyposis CRC by performing a mutational screening of the genes and PTPRJ promoter methylation analysis in 473 familial/early-onset CRC cases, a systematic review of the published cases, and assessment of allele frequencies in control population. In the studied cohort, 24 (5%) carriers of (predicted) deleterious variants in the studied genes and no constitutional PTPRJ epimutations were identified. Assessment of allele frequencies in controls compared with familial/early-onset patients with CRC showed association with increased nonpolyposis CRC risk of disruptive variants in RPS20, IL12RB1, POLE2, MRE11 and POT1, and of FAN1 c.149T>G (p.Met50Arg). Lack of association was demonstrated for LIMK2, PTPN12, LRP6, PTPRJ, POLQ, BLM, MCM9 and FOCAD variants. Additional studies are required to provide conclusive evidence for SEMA4A, WIF1, HNRNPA0 c.-110G>C, and FOCAD large deletions.

A Germline Mutation in the POT1 Gene Is a Candidate for Familial Non-Medullary Thyroid Cancer

Non-medullary thyroid cancer (NMTC) is a common endocrine malignancy with a genetic basis that has yet to be unequivocally established. In a recent whole-genome sequencing study of five families with occurrence of NMTCs, we shortlisted promising variants with the help of bioinformatics tools. Here, we report in silico analyses and in vitro experiments on a novel germline variant (p.V29L) in the highly conserved oligonucleotide/oligosaccharide binding domain of the Protection of Telomeres 1 (POT1) gene in one of the families. The results showed a reduction in telomere-bound POT1 levels in the mutant protein as compared to its wild-type counterpart. HEK293T cells carrying POT1 p.V29L showed increased telomere length in comparison to wild-type cells, suggesting that the mutation causes telomere dysfunction and may play a role in predisposition to NMTC in this family. While one germline mutation in POT1 has already been reported in a melanoma-prone family with prevalence of thyroid cancers, we report the first of such mutations in a family affected solely by NMTCs, thus expanding current knowledge on shelterin complex-associated cancers.

Insights into Genetic Susceptibility to Melanoma by Gene Panel Testing: Potential Pathogenic Variants in ACD, ATM, BAP1, and POT1

The contribution of recently established or candidate susceptibility genes to melanoma missing heritability has yet to be determined. Multigene panel testing could increase diagnostic yield and better define the role of candidate genes. We characterized 273 CDKN2A/ARF and CDK4-negative probands through a custom-designed targeted gene panel that included CDKN2A/ARF, CDK4, ACD, BAP1, MITF, POT1, TERF2IP, ATM, and PALB2. Co-segregation, loss of heterozygosity (LOH)/protein expression analysis, and splicing characterization were performed to improve variant classification. We identified 16 (5.9%) pathogenic and likely pathogenic variants in established high/medium penetrance cutaneous melanoma susceptibility genes (BAP1, POT1, ACD, MITF, and TERF2IP), including two novel variants in BAP1 and 4 in POT1. We also found four deleterious and five likely deleterious variants in ATM (3.3%). Thus, including potentially deleterious variants in ATM increased the diagnostic yield to about 9%. Inclusion of rare variants of uncertain significance would increase the overall detection yield to 14%. At least 10% of melanoma missing heritability may be explained through panel testing in our population. To our knowledge, this is the highest frequency of putative ATM deleterious variants reported in melanoma families, suggesting a possible role in melanoma susceptibility, which needs further investigation.

Lack of Mutations in POT1 Gene in Selected Families with Familial Non-Medullary Thyroid Cancer

To date, the genes involved in familial non-medullary thyroid cancer (FNMTC) remain poorly understood, with the exception of syndromic cases of FNMTC. It has been proposed that germline mutations in telomere-related genes, such as POT1, described in familial melanoma might also predispose individuals to thyroid cancer, requiring further research. We aimed to identify germline mutations in POT1 in selected FNMTC families (with at least three affected members) without a history of other cancers or other features, and to describe the clinical characteristics of these families. Sequencing of the 5'UTR and coding regions of POT1 was performed in seven affected people (index cases) from seven families with FNMTC. In addition, we performed whole-exome sequencing (WES) of DNA from 10 affected individuals belonging to four of these families. We did not find germline variants of interest in POT1 by Sanger sequencing or WES. We neither found putative causative mutations in genes previously described as candidate genes for FNMTC in the 4 families studied by WES. In our study, no germline potentially pathogenic mutations were detected in POT1, minimizing the possibilities that this gene could be substantially involved in non-syndromic FNMTC.

The enigma of excessively long telomeres in cancer: lessons learned from rare human POT1 variants

The discovery that rare POT1 variants are associated with extremely long telomeres and increased cancer predisposition has provided a framework to revisit the relationship between telomere length and cancer development. Telomere shortening is linked with increased risk for cancer. However, over the past decade, there is increasing evidence to show that extremely long telomeres caused by mutations in shelterin components (POT1, TPP1, and RAP1) also display an increased risk of cancer. Here, we will review current knowledge on germline mutations of POT1 identified from cancer-prone families. In particular, we will discuss some common features presented by the mutations through structure-function studies. We will further provide an overview of how POT1 mutations affect telomere length regulation and tumorigenesis.

POT1 mutation spectrum in tumour types commonly diagnosed among POT1-associated hereditary cancer syndrome families

BACKGROUND

The shelterin complex is composed of six proteins that protect and regulate telomere length, including protection of telomeres 1 (POT1). Germline POT1 mutations are associated with an autosomal dominant familial cancer syndrome presenting with diverse malignancies, including glioma, angiosarcoma, colorectal cancer and melanoma. Although somatic POT1 mutations promote telomere elongation and genome instability in chronic lymphocytic leukaemia, the contribution of POT1 mutations to development of other sporadic cancers is largely unexplored.

METHODS

We performed logistic regression, adjusted for tumour mutational burden, to identify associations between POT1 mutation frequency and tumour type in 62 368 tumours undergoing next-generation sequencing.

RESULTS

A total of 1834 tumours harboured a non-benign mutation of POT1 (2.94%), of which 128 harboured a mutation previously reported to confer familial cancer risk in the setting of germline POT1 deficiency. Angiosarcoma was 11 times more likely than other tumours to harbour a POT1 mutation (p=1.4×10^-20), and 65% of POT1-mutated angiosarcoma had >1 mutations in POT1. Malignant gliomas were 1.7 times less likely to harbour a POT1 mutation (p=1.2×10^-3) than other tumour types. Colorectal cancer was 1.2 times less likely to harbour a POT1 mutation (p=0.012), while melanoma showed no differences in POT1 mutation frequency versus other tumours (p=0.67).

CONCLUSIONS

These results confirm a role for shelterin dysfunction in angiosarcoma development but suggest that gliomas arising in the context of germline POT1 deficiency activate a telomere-lengthening mechanism that is uncommon in gliomagenesis.

Melanoma-Bearing Libechov Minipig (MeLiM): The Unique Swine Model of Hereditary Metastatic Melanoma

National cancer databases document that melanoma is the most aggressive and deadly cutaneous malignancy with worldwide increasing incidence in the Caucasian population. Around 10% of melanomas occur in families. Several germline mutations were identified that might help to indicate individuals at risk for preventive interventions and early disease detection. More than 50% of sporadic melanomas carry mutations in Ras/Raf/mitogen-activated protein kinase (MAPK/MEK) pathway, which may represent aims of novel targeted therapies. Despite advances in targeted therapies and immunotherapies, the outcomes in metastatic tumor are still unsatisfactory. Here, we review animal models that help our understanding of melanoma development and treatment, including non-vertebrate, mouse, swine, and other mammal models, with an emphasis on those with spontaneously developing melanoma. Special attention is paid to the melanoma-bearing Libechov minipig (MeLiM). This original swine model of hereditary metastatic melanoma enables studying biological processes underlying melanoma progression, as well as spontaneous regression. Current histological, immunohistochemical, biochemical, genetic, hematological, immunological, and skin microbiome findings in the MeLiM model are summarized, together with development of new therapeutic approaches based on tumor devitalization. The ongoing study of molecular and immunological base of spontaneous regression in MeLiM model has potential to bring new knowledge of clinical importance.

Long telomeres and cancer risk: the price of cellular immortality

The distribution of telomere length in humans is broad, but it has finite upper and lower boundaries. Growing evidence shows that there are disease processes that are caused by both short and long telomere length extremes. The genetic basis of these short and long telomere syndromes may be linked to mutations in the same genes, such as the telomerase reverse transcriptase (TERT), but through differential effects on telomere length. Short telomere syndromes have a predominant degenerative phenotype marked by organ failure that most commonly manifests as pulmonary fibrosis and are associated with a relatively low cancer incidence. In contrast, insights from studies of cancer-prone families as well as genome-wide association studies (GWAS) have identified both rare and common variants that lengthen telomeres as being strongly associated with cancer risk. We have hypothesized that these cancers represent a long telomere syndrome that is associated with a high penetrance of cutaneous melanoma and chronic lymphocytic leukemia. In this Review, we will synthesize the clinical and human genetic observations with data from mouse models to define the role of telomeres in cancer etiology and biology.