Telomere length in peripheral blood cells of germline TP53 mutation carriers is shorter than that of normal individuals of corresponding age

Interactions between the DNA Damage Response and the Telomere Complex in Carcinogenesis: A Hypothesis

Contrary to what was once thought, direct cancer originating from normal stem cells seems to be extremely rare. This is consistent with a preneoplastic period of telomere length reduction/damage in committed cells that becomes stabilized in transformation. Multiple observations suggest that telomere damage is an obligatory step preceding its stabilization. During tissue turnover, the telomeres of cells undergoing differentiation can be damaged as a consequence of defective DNA repair caused by endogenous or exogenous agents. This may result in the emergence of new mechanism of telomere maintenance which is the final outcome of DNA damage and the initial signal that triggers malignant transformation. Instead, transformation of stem cells is directly induced by primary derangement of telomere maintenance mechanisms. The newly modified telomere complex may promote survival of cancer stem cells, independently of telomere maintenance. An inherent resistance of stem cells to transformation may be linked to specific, robust mechanisms that help maintain telomere integrity.

Targeted Therapy with PI3K, PARP, and WEE1 Inhibitors and Radiotherapy in HPV Positive and Negative Tonsillar Squamous Cell Carcinoma Cell Lines Reveals Synergy while Effects with APR-246 Are Limited

Human papillomavirus positive (HPV⁺) tonsillar and base of tongue cancer (TSCC/BOTSCC) is rising in incidence, but chemoradiotherapy is not curative for all. Therefore, targeted therapy with PI3K (BYL719), PARP (BMN-673), and WEE1 (MK-1775) inhibitors alone or combined was pursued with or without 10 Gy and their effects were analyzed by viability, proliferation, and cytotoxicity assays on the TSCC/BOTSCC cell lines HPV⁺ UPCI-SCC-154 and HPV^- UT-SCC-60A. Effective single drug/10 Gy combinations were validated on additional TSCC lines. Finally, APR-246 was assessed on several TSCC/BOTSCC cell lines. BYL719, BMN-673, and MK-1775 treatments induced dose dependent responses in HPV⁺ UPCI-SCC-154 and HPV^- UT-SCC-60A and when combined with 10 Gy, synergistic effects were disclosed, as was also the case upon validation. Using BYL719/BMN-673, BYL719/MK-1775, or BMN-673/MK-1775 combinations on HPV⁺ UPCI-SCC-154 and HPV^- UT-SCC-60A also induced synergy compared to single drug administrations, but adding 10 Gy to these synergistic drug combinations had no further major effects. Low APR-246 concentrations had limited usefulness. To conclude, synergistic effects were disclosed when complementing single BYL719 BMN-673 and MK-1775 administrations with 10 Gy or when combining the inhibitors, while adding 10 Gy to the latter did not further enhance their already additive/synergistic effects. APR-246 was suboptimal in the present context.

Inhibiting the Priming for Cancer in Li-Fraumeni Syndrome

Simple Summary

Li-Fraumeni Syndrome (LFS) is a rare cancer pre-disposition syndrome associated with a germline mutation in the TP53 tumour suppressor gene. People with LFS have a 90% chance of suffering one or more cancers in their lifetime. No treatments exist to reduce this cancer risk. This paper reviews the evidence for how cancers start in people with LFS and proposes that a series of commonly used non-cancer drugs, including metformin and aspirin, can help reduce that lifetime risk of cancer.

Abstract

The concept of the pre-cancerous niche applies the ‘seed and soil’ theory of metastasis to the initial process of carcinogenesis. TP53 is at the nexus of this process and, in the context of Li-Fraumeni Syndrome (LFS), is a key determinant of the conditions in which cancers are formed and progress. Important factors in the creation of the pre-cancerous niche include disrupted tissue homeostasis, cellular metabolism and chronic inflammation. While druggability of TP53 remains a challenge, there is evidence that drug re-purposing may be able to address aspects of pre-cancerous niche formation and thereby reduce the risk of cancer in individuals with LFS.

[Combination of tumors of different histogenesis in pediatric neurosurgery]

Multiple gliomas are determined by synchronous two or more tumors located in different brain regions. It is important to distinguish multiple primary tumors and metastatic brain lesion. In the first case, tumor spread can`t be explained by dissemination along the cerebrospinal fluid pathways, commissural fibers or local metastases. Multiple primary tumors with different histological structures are called bidermal neoplasms. Surgery is preferred in these patients with severe symptoms. The purpose of surgery is maximum resection of tumor. Follow-up may be advisable for small tumors without clinical manifestations. Treatment of multiple gliomas includes surgery, radiotherapy and chemotherapy. Multiple tumor process in children is much more severe compared to a single neoplasia that requires neurological and neuroimaging control and determines treatment strategy. The authors report 3 children with multicentric gliomas, discuss the various aspects of diagnosis and treatment of multiple gliomas and formulate the recommendations for the treatment based on own clinical experience and literature data.

Li-Fraumeni syndrome heterogeneity

Clinical variability is commonly seen in Li-Fraumeni syndrome. Phenotypic heterogeneity is present among different families affected by the same pathogenic variant in TP53 gene and among members of the same family. However, causes of this huge clinical spectrum have not been studied in depth. TP53 type mutation, polymorphic variants in TP53 gene or in TP53-related genes, copy number variations in particular regions, and/or epigenetic deregulation of TP53 expression might be responsible for clinical heterogeneity. In this review, recent advances in the understanding of genetic and epigenetic aspects influencing Li-Fraumeni phenotype are discussed.

Association of 17q24.2-q24.3 deletions with recognizable phenotype and short telomeres

Microdeletions of 17q24.2-q24.3 have been described in several patients with developmental and speech delay, growth retardation, and other features. The relatively large size and limited overlap of the deletions complicate the genotype-phenotype correlation. We identified a girl with intellectual disability, growth retardation, dysmorphic features, and a de novo 2.8 Mb long deletion of 17q24.2-q24.3. Her phenotype was strikingly similar to one previously described boy with Dubowitz syndrome (MIM 223370) and a de novo 3.9 Mb long deletion encompassing the deletion of our patient. In addition, both patients had the shortest telomeres among normal age-matched controls. Our review of all 17q24.2-q24.3 deletion patients revealed additional remarkable phenotypic features shared by the patients, some of which have consequences for their management. Proposed novel genotype-phenotype correlations based on new literature information on the region include the role of PSMD12 and BPTF, the genes recently associated with syndromic neurodevelopmental disorders, and a possible role of the complex topologically associated domain structure of the region, which may explain some of the phenotypic discrepancies observed between patients with similar but not identical deletions. Nevertheless, although different diagnoses including the Dubowitz, Nijmegen breakage (MIM 251260), Silver-Russell (MIM 180860), or Myhre (MIM 139210) syndromes were originally considered in the 17q24.2-q24.3 deletion patients, they clearly belong to one diagnostic entity defined by their deletions and characterized especially by developmental delay, specific facial dysmorphism, abnormalities of extremities and other phenotypes, and possibly also short telomere length.

Genes, Proteins, and Biological Pathways Preventing Chromothripsis

The highly complex structural genome variations chromothripsis, chromoanasynthesis, and chromoplexy are subsumed under the term chromoanagenesis, which means chromosome rebirth. Precipitated by numerous DNA double-strand breaks, they differ in number of and distances between breakpoints, associated copy number variations, order and orientation of segments, and flanking sequences at joining points. Results from patients with the autosomal dominant cancer susceptibility disorder Li-Fraumeni syndrome implicated somatic TP53 mutations in chromothripsis. TP53 participates in the G2/M phase checkpoint, halting cell cycling after premature chromosome compaction during the second half of the S phase, thus preventing chromosome shattering. By experimental TP53 ablation and micronucleus induction, one or a few isolated chromosomes underwent desynchronized replication and chromothripsis. Secondly, chromothripsis occurred after experimental induction of telomere crisis after which dicentric chromosomes sustained TREX1-mediated resolution of chromosome bridges and kataegis. Third, DNA polymerase Polθ-dependent chromothripsis has been documented. Finally, a family with chromothripsis after L1 element-dependent retrotransposition and Alu/Alu homologous recombination has been reported. Human chromosomal instability syndromes share defects in responses to DNA double-strand breaks, characteristic cell cycle perturbations, elevated rates of micronucleus formation, premature chromosome compaction, and apoptosis. They are also associated with elevated susceptibility to malignant disease, such as medulloblastomas and gliomas in ataxia-telangiectasia, leukemia and lymphoma in Bloom syndrome, and osteosarcoma and soft tissue sarcoma in Werner syndrome. The latter syndrome is characterized by a premature aging-like progressive decline of mesenchymal tissues. In all thus far studied cases, constitutional chromothripsis occurred in the male germline and male patients with defects in the double-strand break response genes ATM, MRE11, BLM, LIG4, WRN, and Ku70 show impaired fertility. Conceivably, chromothripsis may, in a stochastic rather than deterministic way, be implicated in germline structural variation, malignant disease, premature aging, genome mosaicism in somatic tissues, and male infertility.

Inherited TP53 Mutations and the Li-Fraumeni Syndrome

Li-Fraumeni syndrome (LFS) is a complex hereditary cancer predisposition disorder associated with early-onset cancers in diverse tissues of origin. Germline TP53 mutations are identified in 75% of patients with classic LFS. The lifetime likelihood of a TP53 mutation carrier developing cancer approaches 75% in males and almost 100% in females. Several genetic modifiers have been implicated to account for the phenotypic variability within and across LFS families; however, efforts to develop predictive algorithms of age of onset and type of cancers in individual patients have not yet found clinical use. Although it is not possible to prevent cancers from forming in LFS patients, novel protocols have been developed for surveillance for early tumor detection, leading to improvements in survival. Comprehensive studies of the genome and epigenome in LFS families in the context of germline TP53 mutations is anticipated to shed light on this intriguing, yet devastating, disease and to transform the clinical management of patients.

Genetic anticipation in BRCA1/BRCA2 families after controlling for ascertainment bias and cohort effect

BACKGROUND

Genetic anticipation, the earlier onset of disease in successive generations, has been reported in hereditary breast and ovarian cancer syndrome (HBOC), but little is known about its underlying mechanisms. Ascertainment bias has been suggested as a reason in previous studies. Likewise, cohort effect, which may be caused by environmental factors, can be misinterpreted as genetic anticipation.

METHODS

The authors reviewed the pedigrees of 176 kindreds, segregating those with deleterious mutations in breast cancer genes 1 and 2 (BRCA1/BRCA2) who had at least 2 consecutive generations of the same cancer (breast or ovarian). By using mutation probabilities as analytical weights in weighted random-effect models, generational differences in the age at onset of breast/ovarian cancer were calculated. The analyses were further controlled for ascertainment bias by excluding probands and adjusting for birth-cohort effect in the anticipation models.

RESULTS

The mean age at the onset of breast cancer for the probands' generation was 41.9 years, which was 6.8 years and 9.8 years earlier than the parents' and grandparents' generations, respectively. The anticipation effect for breast cancer remained significant after excluding the probands. There was a birth-cohort effect: patients who were born in 1930s and 1940s had breast cancer 5.0 years and 7.6 years earlier than patients who were born before 1920. The difference in breast cancer age of onset across generations was no longer significant after adjusting for birth-cohort effect.

CONCLUSIONS

The observed anticipation effect was driven mainly by a decrease in age of onset across birth cohorts, underscoring the need for risk-reducing interventions that target changing environmental/lifestyle factors in BRCA1/BRCA2 carriers. Cancer 2016;122:1913-20. © 2016 American Cancer Society.

Connecting molecular pathways to hereditary cancer risk syndromes

An understanding of the genetic causes and molecular pathways of hereditary cancer syndromes has historically informed our knowledge and treatment of all types of cancers. For this review, we focus on three rare syndromes and their associated genetic mutations including BAP1, TP53, and SDHx (SDHA, SDHB, SDHC, SDHD, SDHAF2). BAP1 encodes an enzyme that catalyzes the removal of ubiquitin from protein substrates, and germline mutations of BAP1 cause a novel cancer syndrome characterized by high incidence of benign atypical melanocytic tumors, uveal melanomas, cutaneous melanomas, malignant mesotheliomas, and potentially other cancers. TP53 mutations cause Li-Fraumeni syndrome (LFS), a highly penetrant cancer syndrome associated with multiple tumors including but not limited to sarcomas, breast cancers, brain tumors, and adrenocortical carcinomas. Genomic modifiers for tumor risk and genotype-phenotype correlations in LFS are beginning to be identified. SDH is a mitochondrial enzyme complex involved in the tricarboxylic acid (TCA) cycle, and germline SDHx mutations lead to increased succinate with subsequent paragangliomas, pheochromocytomas, renal cell carcinomas (RCCs), gastrointestinal stromal tumors (GISTs), and other rarer cancers. In all of these syndromes, the molecular pathways have informed our understanding of tumor risk and successful early tumor surveillance and screening programs.

Primed for cancer: Li Fraumeni Syndrome and the pre-cancerous niche

The complex relationship between tumour and stroma is still being elucidated but it is clear that cancer is a disease of more than just malignant cells. However, the dominant focus of our current understanding of Li Fraumeni Syndrome (LFS) remains on the function of p53 as ‘guardian of the genome’. Recent evidence shows that the TP53 gene is at the nexus of a wider range of functions, including aspects of cellular metabolism, aging and immunity. Incorporating this broader picture of the role of TP53 together with our understanding of the role of the host microenvironment in cancer initiation and progression gives a more nuanced picture of LFS. Furthermore, there is clinical evidence to suggest that the host environment in healthy individuals with LFS already includes some of the features of a ‘pre-cancerous niche’ that makes cancer initiation more likely. It is suggested, finally, that there are pharmacological interventions capable of altering this pre-cancerous niche, thus potentially reducing the cancer risk in individuals with LFS.

Mutational Status of CDKN2A and TP53 Genes in Laryngeal Squamous Cell Carcinoma

Laryngeal squamous cell carcinoma (LSCC) is the second most common tumour of the head and neck. It is characterized by frequent aberrations in two cell-cycle regulators--CDKN2A and TP53. However, LSCC has been often studied as a part of the group of head and neck cancers and not as an individual entity. In the current study we aimed to examine mutation status of CDKN2A and TP53 genes in 108 LSCC patients. DNA was extracted from fresh-frozen tumour tissues; exons 1-3 of CDKN2A and exons 5-8 of TP53 were screened for mutations by direct sequencing. Genetic aberrations in CDKN2A were found in 16 (14.2%) and those in TP53--in 56/108 (51.9%) tumours. Seven mutations (two insertions, three deletions, one missense and one silent) detected in CDKN2A were not described previously. Also, we found seven novel deletions and a novel indel in TP53. No significant associations with clinical features were found. However, TP53 mutations were predominantly observed in smokers with advanced stage tumours. Screening for genetic aberrations in a defined group of LSCC contributes to the knowledge about laryngeal carcinogenesis. Further investigations are required to confirm the observed trends in associations with clinical features.

A pathogenic mosaic TP53 mutation in two germ layers detected by next generation sequencing

Background

Li-Fraumeni syndrome is caused by germline TP53 mutations and is clinically characterized by a predisposition to a range of cancers, most commonly sarcoma, brain tumours and leukemia. Pathogenic mosaic TP53 mutations have only rarely been described.

Methods and Findings

We describe a 2 years old child presenting with three separate cancers over a 6 month period; two soft tissue mesenchymal tumors and an aggressive metastatic neuroblastoma. As conventional testing of blood DNA by Sanger sequencing for mutations in TP53, ALK, and SDH was negative, whole exome sequencing of the blood DNA of the patient and both parents was performed to screen more widely for cancer predisposing mutations. In the patient's but not the parents' DNA we found a c.743 G>A, p.Arg248Gln (CCDS11118.1) TP53 mutation in 3–20% of sequencing reads, a level that would not generally be detectable by Sanger sequencing. Homozygosity for this mutation was detected in all tumor samples analyzed, and germline mosaicism was demonstrated by analysis of the child's newborn blood spot DNA. The occurrence of separate tumors derived from different germ layers suggests that this de novo mutation occurred early in embryogenesis, prior to gastrulation.

Conclusion

The case demonstrates pathogenic mosaicim, detected by next generation deep sequencing, that arose in the early stages of embryogenesis.

Li-Fraumeni syndrome: cancer risk assessment and clinical management

Carriers of germline mutations in the TP53 gene, encoding the cell-cycle regulator and tumour suppressor p53, have a markedly increased risk of cancer-related morbidity and mortality during both childhood and adulthood, and thus require appropriate and effective cancer risk management. However, the predisposition of such patients to multiorgan tumorigenesis presents a specific challenge for cancer risk management programmes. Herein, we review the clinical implications of germline mutations in TP53 and the evidence for cancer screening and prevention strategies in individuals carrying such mutations, as well as examining the potential psychosocial implications of lifelong management for a ubiquitous cancer risk. In addition, we propose an evidence-based framework for the clinical management of TP53 mutation carriers and provide a platform for addressing the management of other cancer predisposition syndromes that can affect multiple organs.

p53 and hereditary cancer

The roles of p53 as "guardian of the genome" are extensive, encompassing regulation of the cell cycle, DNA repair, apoptosis, cellular metabolism, and senescence - ultimately steering cells through a balance of death and proliferation. The majority of sporadic cancers exhibit loss of p53 activity due to mutations or deletions of TP53, and alterations in its signaling pathway. Germline TP53 mutations have been identified in a group of families exhibiting a rare but highly penetrant familial cancer syndrome, called the Li-Fraumeni syndrome (LFS). Between 60-80% of 'classic' LFS families carry mutant Trp53. The most frequent cancers observed are premenopausal breast cancer, bone and soft-tissue sarcomas, adrenal cortical carcinomas, and brain tumors. Penetrance is nearly 100% by age 70. Although TP53 is currently the only validated susceptibility locus recognized for LFS, recent studies have focused on the identification of genetic modifiers that may explain the wide phenotypic variability observed in LFS patients. Analyses of single nucleotide polymorphisms (SNPs), genome-wide copy number and telomere length have provided greater insight into the potential genetic modifiers of LFS. Moreover, the study of Trp53 mutant heterozygous mouse models has elucidated novel functions of p53, and offers insight into the mechanisms governing tumorigenesis in LFS. The key findings outlined in this chapter provide an overview of the molecular basis of LFS and the role of p53 in this unique heritable cancer syndrome.

Telomere length and genetic anticipation in Lynch syndrome

Telomere length variation has been associated with increased risk of several types of tumors, and telomere shortening, with genetic anticipation in a number of genetic diseases including hereditary cancer syndromes. No conclusive studies have been performed for Lynch syndrome, a hereditary colorectal cancer syndrome caused by germline mutations in the DNA mismatch repair genes. Here we evaluate telomere length in Lynch syndrome, both as a cancer risk factor and as a mechanism associated with anticipation in the age of cancer onset observed in successive generations of Lynch syndrome families. Leukocyte telomere length was measured in 244 mismatch repair gene mutation carriers from 96 Lynch syndrome families and in 234 controls using a monochrome multiplex quantitative PCR method. Cancer-affected mutation carriers showed significantly shorter telomeres than cancer-free mutation carriers. In addition, cancer-affected carriers showed the most pronounced shortening of telomere length with age, compared with unaffected carriers. The anticipation in the age of cancer onset observed in successive generations was not associated with telomere shortening, although, interestingly, all mother-son pairs showed telomere shortening. In conclusion, cancer-affected mismatch repair gene mutation carriers have distinct telomere-length pattern and dynamics. However, anticipation in the age of onset is not explained by telomere shortening. Pending further study, our findings suggest that telomere attrition might explain the previously reported dependence of cancer risk on the parent-of-origin of mismatch repair gene mutations.

Li Fraumeni syndrome, cancer and senescence: a new hypothesis

Li Fraumeni Syndrome (LFS) is a rare autosomal dominant hereditary cancer syndrome characterized by germline mutations in the TP53 tumour suppressor gene. Sufferers are prone to early onset cancers, particularly sarcomas, adrenocortical carcinoma and breast cancer. Cells from LFS sufferers are known to exhibit telomere dysfunction, genomic instability and spontaneous immortalisation. It is hypothesized that these facets of the LFS host are evidence that the host environment is "primed" for carcinogenesis over and above the lack of p53 tumour suppressor function. Further, it is hypothesized that the host presents an ideal environment for "two compartment tumour metabolism" to take place. Evidence from recent studies supports this new view of LFS and suggests that disrupting certain features of the host environment may markedly reduce the incidence of cancer in LFS sufferers.

Connecting molecular pathways to hereditary cancer risk syndromes

An understanding of the genetic causes and molecular pathways of hereditary cancer syndromes has historically informed our knowledge and treatment of all types of cancers. For this review, we focus on three rare syndromes and their associated genetic mutations including BAP1, TP53, and SDHx (SDHA, SDHB, SDHC, SDHD, SDHAF2). BAP1 encodes an enzyme that catalyzes the removal of ubiquitin from protein substrates, and germline mutations of BAP1 cause a novel cancer syndrome characterized by high incidence of benign atypical melanocytic tumors, uveal melanomas, cutaneous melanomas, malignant mesotheliomas, and potentially other cancers. TP53 mutations cause Li-Fraumeni syndrome (LFS), a highly penetrant cancer syndrome associated with multiple tumors including but not limited to sarcomas, breast cancers, brain tumors, and adrenocortical carcinomas. Genomic modifiers for tumor risk and genotype-phenotype correlations in LFS are beginning to be identified. SDH is a mitochondrial enzyme complex involved in the tricarboxylic acid (TCA) cycle, and germline SDHx mutations lead to increased succinate with subsequent paragangliomas, pheochromocytomas, renal cell carcinomas (RCCs), gastrointestinal stromal tumors (GISTs), and other rarer cancers. In all of these syndromes, the molecular pathways have informed our understanding of tumor risk and successful early tumor surveillance and screening programs.

Number of rare germline CNVs and TP53 mutation types

Background

The Li-Fraumeni syndrome (LFS), an inherited rare cancer predisposition syndrome characterized by a variety of early-onset tumors, is caused by different highly penetrant germline mutations in the TP53 gene; each separate mutation has dissimilar functional and phenotypic effects, which partially clarifies the reported heterogeneity between LFS families. Increases in copy number variation (CNV) have been reported in TP53 mutated individuals, and are also postulated to contribute to LFS phenotypic variability. The Brazilian p.R337H TP53 mutation has particular functional and regulatory properties that differ from most other common LFS TP53 mutations, by conferring a strikingly milder phenotype.

Methods

We compared the CNV profiles of controls, and LFS individuals carrying either p.R337H or DNA binding domain (DBD) TP53 mutations by high resolution array-CGH.

Results

Although we did not find any significant difference in the frequency of CNVs between LFS patients and controls, our data indicated an increased proportion of rare CNVs per genome in patients carrying DBD mutations compared to both controls (p=0.0002***) and p.R337H (0.0156*) mutants.

Conclusions

The larger accumulation of rare CNVs in DBD mutants may contribute to the reported anticipation and severity of the syndrome; likewise the fact that p.R337H individuals do not present the same magnitude of rare CNV accumulation may also explain the maintenance of this mutation at relatively high frequency in some populations.

Correlation of telomere length shortening with TP53 somatic mutations, polymorphisms and allelic loss in breast tumors and esophageal cancer

Genomic instability caused by telomere erosion is an important mechanism of tumorigenesis. p53 plays a key role in cellular senescence and/or apoptosis associated with telomere erosion which positions p53 as a guard against tumorigenesis. The present study was undertaken to investigate the potential interactions between p53 functional mutations, polymorphisms, allelic loss and telomere erosion in 126 breast tumor patients and 68 esophageal cancer patients. Telomere length (TL) was measured by real-time quantitative PCR. Somatic mutations, polymorphisms and allelic loss in the TP53 gene were detected by direct sequencing of both tumor and normal tissue samples. Our results showed that telomeres were significantly shorter in tumors with somatic p53 mutations compared with tumors with wild-type p53 in both breast tumors (P=0.007) and esophageal cancer (P=0.001). Telomeres of patients with minor genotype CC of rs12951053 and GG of rs1042522 were significantly shorter compared to patients with other genotypes of this single nucleotide polymorphism in esophageal cancer tissue. Furthermore, TP53 allelic loss was detected and significantly associated with somatic mutations in both types of tumor tissues. These findings suggest that somatic p53 mutations, rs12951053 genotype CC and rs1042522 genotype GG contribute to erosion of telomeres, and TP53 allelic loss may be one of the representations of chromosomal instability caused by telomere erosion combined with somatic p53 mutations. These results support that the TP53 gene has a strong interaction with TL erosion in tumorigenesis.

Li-Fraumeni syndrome: report of a clinical research workshop and creation of a research consortium

Li-Fraumeni syndrome (LFS) is a rare dominantly inherited cancer predisposition syndrome that was first described in 1969. In most families, it is caused by germline mutations in the TP53 gene and is characterized by early onset of multiple specific cancers and very high lifetime cumulative cancer risk. Despite significant progress in understanding the molecular biology of TP53, the optimal clinical management of this syndrome is poorly defined. We convened a workshop on November 2, 2010, at the National Institutes of Health in Bethesda, Maryland, bringing together clinicians and scientists, as well as individuals from families with LFS, to review the state of the science, address clinical management issues, stimulate collaborative research, and engage the LFS family community. This workshop also led to the creation of the Li-Fraumeni Exploration (LiFE) Research Consortium.

Anticipation in lynch syndrome: where we are where we go

Lynch syndrome (LS) is the most common form of inherited predisposition to develop cancer mainly in the colon and endometrium but also in other organ sites. Germline mutations in DNA mismatch repair (MMR) gene cause the transmission of the syndrome in an autosomal dominant manner. The management of LS patients is complicated by the large variation in age at cancer diagnosis which requires these patients to be enrolled in surveillance protocol starting as early as in their second decade of life. Several environmental and genetic factors have been proposed to explain this phenotypic heterogeneity, but the molecular mechanisms remain unknown. Although the presence of genetic anticipation in Lynch syndrome has been suspected since 15 years, only recently the phenomenon has been increasingly reported to be present in different cancer genetic syndromes including LS. While the biological basis of earlier cancer onset in successive generations remains poorly known, recent findings point to telomere dynamics as a mechanism significantly contributing to genetic anticipation in Lynch syndrome and in other familial cancers. In this review, we summarize the clinical and molecular features of Lynch syndrome, with a particular focus on the latest studies that have investigated the molecular mechanisms of genetic anticipation.

Genome sequencing of pediatric medulloblastoma links catastrophic DNA rearrangements with TP53 mutations

Genomic rearrangements are thought to occur progressively during tumor development. Recent findings, however, suggest an alternative mechanism, involving massive chromosome rearrangements in a one-step catastrophic event termed chromothripsis. We report the whole-genome sequencing-based analysis of a Sonic-Hedgehog medulloblastoma (SHH-MB) brain tumor from a patient with a germline TP53 mutation (Li-Fraumeni syndrome), uncovering massive, complex chromosome rearrangements. Integrating TP53 status with microarray and deep sequencing-based DNA rearrangement data in additional patients reveals a striking association between TP53 mutation and chromothripsis in SHH-MBs. Analysis of additional tumor entities substantiates a link between TP53 mutation and chromothripsis, and indicates a context-specific role for p53 in catastrophic DNA rearrangements. Among these, we observed a strong association between somatic TP53 mutations and chromothripsis in acute myeloid leukemia. These findings connect p53 status and chromothripsis in specific tumor types, providing a genetic basis for understanding particularly aggressive subtypes of cancer.

Li-fraumeni syndrome

Li-Fraumeni syndrome (LFS) is a classic cancer predisposition disorder that is commonly associated with germline mutations of the p53 tumor suppressor gene. Examination of the wide spectrum of adult-onset and childhood cancers and the distribution of p53 mutations has led to a greater understanding of cancer genotype-phenotype correlations. However, the complex LFS phenotype is not readily explained by the simple identification of germline p53 mutations in affected individuals. Recent work has identified genetic events that modify the LFS phenotype. These include intragenic polymorphisms, mutations/polymorphisms of genes in the p53 regulatory pathway, as well as more global events such as aberrant copy number variation and telomere attrition. These genetic events may, in part, explain the breadth of tumor histiotypes within and across LFS families, the apparent accelerated age of onset within families, and the range of clinical outcomes among affected family members. This review will examine the clinical and genetic definitions of LFS and offer insight into how lessons learned from the study of this rare disorder may inform similar questions in other familial cancer syndromes.

Genetic anticipation is associated with telomere shortening in hereditary breast cancer

There is increasing evidence suggesting that short telomeres and subsequent genomic instability contribute to malignant transformation. Telomere shortening has been described as a mechanism to explain genetic anticipation in dyskeratosis congenita and Li-Fraumeni syndrome. Since genetic anticipation has been observed in familial breast cancer, we aimed to study telomere length in familial breast cancer patients and hypothesized that genetic defects causing this disease would affect telomere maintenance resulting in shortened telomeres. Here, we first investigated age anticipation in mother-daughter pairs with breast cancer in 623 breast cancer families, classified as BRCA1, BRCA2, and BRCAX. Moreover, we analyzed telomere length in DNA from peripheral blood leukocytes by quantitative PCR in a set of 198 hereditary breast cancer patients, and compared them with 267 control samples and 71 sporadic breast cancer patients. Changes in telomere length in mother-daughter pairs from breast cancer families and controls were also evaluated to address differences through generations. We demonstrated that short telomeres characterize hereditary but not sporadic breast cancer. We have defined a group of BRCAX families with short telomeres, suggesting that telomere maintenance genes might be susceptibility genes for breast cancer. Significantly, we described that progressive telomere shortening is associated with earlier onset of breast cancer in successive generations of affected families. Our results provide evidence that telomere shortening is associated with earlier age of cancer onset in successive generations, suggesting that it might be a mechanism of genetic anticipation in hereditary breast cancer.

The fact that accelerated telomere shortening accompanies different premature aging syndromes and seems to be associated with increased risk of cancer development prompted us to analyze the role of telomere length in hereditary breast cancer. In this study we found that telomeres of peripheral blood cells from familial breast cancer patients were significantly shorter than those from the control population. Women carrying a mutation in BRCA1 or BRCA2 genes, and a subset of BRCAX families, were characterized by short telomeres. We also demonstrated that genetic anticipation, the successive earlier age of onset of cancer, in these families was associated with a decrease of the telomere length in affected daughters compared to their mothers. This is the first study suggesting that telomere shortening may contribute to anticipation in breast cancer families and that analysis of telomere length in hereditary breast cancer may affect the design of surveillance programs for affected families.

Biochemical and imaging surveillance in germline TP53 mutation carriers with Li-Fraumeni syndrome: a prospective observational study

BACKGROUND

Individuals with Li-Fraumeni syndrome have a high lifetime risk of developing cancer. We assessed the feasibility and potential clinical effect of a comprehensive surveillance protocol in asymptomatic TP53 mutation carriers in families with this syndrome.

METHODS

We implemented a clinical surveillance protocol, using frequent biochemical and imaging studies, for asymptomatic TP53 mutation carriers on Jan 1, 2004, and did a prospective observational study of members of eight families with Li-Fraumeni syndrome who either chose to undergo surveillance or chose not to undergo surveillance. The primary outcome measure was detection of new cancers. The secondary outcome measure was overall survival.

FINDINGS

As of Nov 1, 2010, 33 TP53 mutation carriers were identified, 18 of whom underwent surveillance. The surveillance protocol detected ten asymptomatic tumours in seven patients, including small, high-grade tumours and low-grade or premalignant tumours. All seven mutation carriers were alive after a median follow-up of 24 months (IQR 22-65 months). 12 high-grade, high-stage tumours developed in 10 individuals in the non-surveillance group, two of whom (20%) were alive at the end of follow-up (p=0·0417 for comparison with survival in the surveillance group). 3-year overall survival was 100% in the surveillance group and 21% (95% CI 4-48%) in the non-surveillance group (p=0·0155).

INTERPRETATION

Our findings show the feasibility of a clinical surveillance protocol for the detection of asymptomatic neoplasms in individuals with germline TP53 mutations. This strategy offers a management option for affected individuals, and its benefits lend support to the use of early genetic testing of at-risk individuals and families.

FUNDING

Canadian Cancer Society Research Institute, Canadian Institutes of Health Research, SickKids Foundation, and Soccer for Hope.

Analysis of telomere dynamics in peripheral blood cells from patients with Lynch syndrome

BACKGROUND

In patients with Lynch syndrome, germline mutations in DNA mismatch repair (MMR) genes cause a high risk of developing a broad spectrum of cancers. To date, the management of patients with Lynch syndrome has represented a major challenge because of large variations in age at cancer onset. Several factors, including genetic anticipation, have been proposed to explain this phenotypic heterogeneity, but the molecular mechanisms remain unknown. Telomere shortening is a common event in tumorigenesis and also has been observed in different familial cancers. In this study, the authors investigated the possibility of a relation between telomere length and cancer onset in patients with Lynch syndrome.

METHODS

The mean telomere length was measured using quantitative polymerase chain reaction in peripheral blood samples from a control group of 50 individuals, from 31 unaffected mutation carriers, and from 43 affected patients, and the results were correlated with both gene mutation and cancer occurrence. In affected patients, telomere attrition was correlated with age at cancer onset. In all patients, a t test was used to assess the linearity of the regression.

RESULTS

A significant correlation between telomere length and age was observed in both affected and unaffected mutation carriers (P = .0016 and P = .004, respectively) and in mutS homolog 2 (MSH2) mutation carriers (P = .0002) but not in mutL homolog 1 (MLH1) mutation carriers. Telomere attrition was correlated significantly with age at onset in MSH2 carriers (P = .004), whereas an opposite trend toward longer telomeres in patients with delayed onset was observed in MLH1 carriers.

CONCLUSIONS

The current data suggested that telomere dynamics differ between MLH1 and MSH2 mutation carriers. It is possible that subtle, gene-specific mechanisms can be linked to cancer onset and anticipation in patients with Lynch syndrome.

An evolutionary review of human telomere biology: the thrifty telomere hypothesis and notes on potential adaptive paternal effects

Telomeres, repetitive DNA sequences found at the ends of linear chromosomes, play a role in regulating cellular proliferation, and shorten with increasing age in proliferating human tissues. The rate of age-related shortening of telomeres is highest early in life and decreases with age. Shortened telomeres are thought to limit the proliferation of cells and are associated with increased morbidity and mortality. Although natural selection is widely assumed to operate against long telomeres because they entail increased cancer risk, the evidence for this is mixed. Instead, here it is proposed that telomere length is primarily limited by energetic constraints. Cell proliferation is energetically expensive, so shorter telomeres should lead to a thrifty phenotype. Shorter telomeres are proposed to restrain adaptive immunity as an energy saving mechanism. Such a limited immune system, however, might also result in chronic infections, inflammatory stress, premature aging, and death--a more "disposable soma." With an increased reproductive lifespan, the fitness costs of premature aging are higher and longer telomeres will be favored by selection. Telomeres exhibit a paternal effect whereby the offspring of older fathers have longer telomeres due to increased telomere lengths of sperm with age. This paternal effect is proposed to be an adaptive signal of the expected age of male reproduction in the environment offspring are born into. The offspring of lineages of older fathers will tend to have longer, and thereby less thrifty, telomeres, better preparing them for an environment with higher expected ages at reproduction.

Shorter telomere length in peripheral blood cells associated with migraine in women

OBJECTIVE

To evaluate relative telomere length of female migraine patients.

BACKGROUND

Migraine is a debilitating disorder affecting 6-28% of the population. Studies on the mechanisms of migraine have demonstrated genetic causes but the pathophysiology and subcellular effects of the disease remain poorly understood. Shortened telomere length is associated with age-related or chronic diseases, and induced stresses. Migraine attacks may impart significant stress on cellular function, thus this study investigates a correlation between shortening of telomeres and migraine.

METHODS

Relative telomere length was measured using a previously described quantitative polymerase chain reaction method. A regression analysis was performed to assess differences in mean relative telomere length between migraine patients and healthy controls.

RESULTS

The leukocyte telomeres of a cohort of 142 Caucasian female migraine subjects aged 18-77 years and 143 matched 17-77-year-old healthy control Caucasian women were examined. A significantly shorter relative telomere length was observed in the migraine group compared with the control group after adjusting for age and body mass index (P = .001). In addition, age of onset was observed to associate with the loss of relative telomere length, especially at early age of onset (<17 years old). No association was observed between relative telomere length and the severity and frequency of migraine attacks and the duration of migraine.

CONCLUSION

Telomeres are shorter in migraine patients and there is more variation in telomere length in migraine patients.

Tumor protein 53 mutations and inherited cancer: beyond Li-Fraumeni syndrome

PURPOSE OF REVIEW

Germline TP53 (tumor protein 53) mutations are the molecular basis of a complex cancer predisposition syndrome, the Li-Fraumeni syndrome. The present review discusses the diversity of tumor patterns in TP53 mutation carriers, focusing on molecular factors that may explain familial and individual differences, such as genotype/phenotype correlations, genetic modifiers and genetic anticipation.

RECENT FINDINGS

Initially identified 20 years ago, germline TP53 mutations appear to be associated with an extremely diverse range of cancers. Although no other gene has been found in Li-Fraumeni syndrome, recent results show that the functional effects of particular mutations, polymorphisms in TP53 or in regulators such as MDM2 (murine double minute 2), variations in DNA copy number and variations in telomere length, have a strong impact on individual risk and on tumor patterns. Furthermore, recent studies in large cohorts suggest that TP53 germline mutations may occur in up to 1: 5000 individuals.

SUMMARY

Germline TP53 mutations may be responsible for a large fraction (15-20%) of all inherited cancers. Although mutations are detectable by sequencing, counseling and follow-up remain problematic due to the wide variations in disease presentation. Elucidating the molecular mechanisms underlying the predisposition caused by TP53 deficiency may help to develop better, evidence-based and personalized clinical protocols.

Familial small cell carcinoma of the ovary

Ovarian tumors have a low incidence in childhood, accounting for 1% of malignancies within the ages of 0-17 years. Small cell carcinoma of the ovary is a rare histology and historically has a poor prognosis. We report a case of an 11-year-old female diagnosed with small cell carcinoma of the ovary and hypercalcemia (SCCOHT). There was a strong family history of the disease, a reduction in the age of onset in the proband, and the absence of BRCA mutations. This case suggests the phenomenon of genetic anticipation in an ovarian cancer.

An effect from anticipation also in hereditary nonpolyposis colorectal cancer families without identified mutations

Optimal prevention of hereditary cancer is central and requires initiation of surveillance programmes and/or prophylactic measures at a safe age. Anticipation, expressed as an earlier age at onset in successive generations, has been demonstrated in hereditary nonpolyposis colorectal cancer (HNPCC). We specifically addressed anticipation in phenotypic HNPCC families without disease-predisposing mismatch repair (MMR) defects since risk estimates and age at onset are particularly difficult to determine in this cohort. The national Danish HNPCC register was used to identify families who fulfilled the Amsterdam criteria for HNPCC and showed normal MMR function and/or lack of disease-predisposing MMR gene mutation. In total, 319 cancers from 212 parent-child pairs in 99 families were identified. A paired t-test and a bivariate statistical model were used to assess anticipation. Both methods demonstrated an effect from anticipation with cancer diagnosed mean 11.4 years (t-test, p<0.0001) and mean 5.9 (bivariate model, p=0.02) years earlier in children than in parents. This observation suggests that anticipation may apply also to families without identified mutations and serves as a reminder to initiate surveillance programmes at young age also in HNPCC families with undefined genetic causes.

Chinese tea consumption is associated with longer telomere length in elderly Chinese men

Environmental and lifestyle factors that affect oxidative stress and inflammation may influence telomere length (TL). There are limited data to relate the effect of dietary components on TL. The present study examined the association between food groups and TL in a sample of elderly Chinese. In a sample of 2006 Chinese (976 men and 1030 women) aged 65 years and over, TL was measured by quantitative real-time PCR and daily intake of food groups was assessed by a validated FFQ. Linear regression and analysis of covariance were used to examine the association between food group intake and TL, with adjustment for demographic and lifestyle factors. In men, only Chinese tea consumption was significantly associated with TL after adjustment for demographics and lifestyle factors (P = 0·002). Mean difference in TL for those in the highest quartile of Chinese tea consumption (>3 cups/d or >750 ml/d) as compared with those in the lowest quartile of Chinese tea consumption ( ≤ 0·28 cups/d or ≤ 70 ml/d) was 0·46 kb, corresponding to approximately a difference of 5 years of life. In women, intake of fats and oils was borderline and negatively associated with TL after adjustment for demographic and lifestyle factors (P = 0·037). In conclusion, Chinese tea consumption was positively associated with TL in elderly Chinese men.

The TP53 gene promoter is not methylated in families suggestive of Li-Fraumeni syndrome with no germline TP53 mutations

Germline TP53 mutations are found in only 70% of families with the Li-Fraumeni syndrome (LFS), and with an even lower frequency in families suggestive of LFS but not meeting clinical criteria of the syndrome. Despite intense efforts, to date, no other genes have been associated with the disorder in a significant number of TP53 mutation-negative families. A search for defects in TP53 other than heterozygous missense mutations showed that neither intron variants nor sequence variants in the TP53 promoter are frequent in LFS, and multiexon deletions have been found to be responsible for LFS only in several cases. Another cancer predisposition syndrome, hereditary non-polyposis colon cancer, has been associated with epigenetic silencing of one allele of the MLH1 or MSH2 genes. This prompted us to test the methylation of the TP53 gene promoter in a set of 14 families suggestive of LFS using bisulphite sequencing of three DNA fragments from the 5' region of the gene. We found no detectable methylation at any of the CG dinucleotides tested. Thus, epigenetic silencing of the TP53 promoter is not a frequent cause of the disorder in families suggestive of LFS but with no germline mutations in the coding part of the gene.

TP53 germline mutations in Portugal and genetic modifiers of age at cancer onset

The Li-Fraumeni syndrome (LFS) is a rare, autosomal dominant disease caused by TP53 germline mutations. This study aimed to characterize the TP53 mutational spectrum in patients suspected to have LFS in Portugal and to evaluate the influence of the MDM2-SNP309 and TP53-72Arg variants and of telomere length on age of tumor onset. Probands were primarily selected using the classical LFS criteria (two cases) or the more sensitive Chompret Li-Fraumeni-like (LFL) criteria (13 cases), but 12 additional patients that did not comply with those LFS or LFL criteria were included in the analysis based on clinical suspicion (LFS suspects). Nine of the 27 probands (33.3%) presented germline TP53 mutations, two of them occurring de novo and two of them being novel. Three of the nine TP53 mutations were found in families that did not comply with any of the commonly used criteria for TP53 testing, leaving room to recommend the use of less stringent criteria. An association was found between the presence of the TP53-72Arg (but not the MDM2-SNP309) variant and earlier age of onset in TP53 carriers. A negative correlation between telomere length and age of cancer onset was found in patients with germline TP53 mutation, whereas no such correlation was found in controls or in patients with wild-type TP53.

Role for genetic anticipation in Lynch syndrome

PURPOSE

Anticipation (ie, an earlier age at onset in successive generations) is linked to repeat expansion in neurodegenerative syndromes, whereas its role in hereditary cancer is unclear. We assessed anticipation in Lynch syndrome (hereditary nonpolyposis colorectal cancer [HNPCC]), in which DNA mismatch repair (MMR) defects cause early and accelerated tumor development with a broad tumor spectrum.

PATIENTS AND METHODS

In the population-based Danish HNPCC registry, 407 MMR gene mutation carriers who had developed cancer associated with Lynch syndrome, were identified. These individuals formed 290 parent-child pairs in which age at the first cancer diagnosis was assessed. A paired t-test and a specifically developed bivariate model were used to assess a possible role of anticipation.

RESULTS

Both methods revealed anticipation with children developing cancer mean 9.8 years (P < .001) earlier than parents using the paired t-test and 5.5 years (P < .001) earlier using the bivariate model. Birth cohort effects were excluded since anticipation with 7.2 years earlier age at onset was identified also in the oldest cohort, in which the children were observed until they were older than 80 years. The effect remained when cancers diagnosed at surveillance were excluded, applied to maternal as well as paternal inheritance, and was independent of the MMR gene mutated.

CONCLUSION

The effect from anticipation demonstrated in this large, population-based Lynch syndrome cohort underscores the need to initiate surveillance programs at young age. It should also stimulate research into the genetic mechanisms that determine age at onset and whether the genetic instability that characterizes Lynch syndrome can be linked to anticipation.

Risk stratification in cancer predisposition syndromes: lessons learned from novel molecular developments in Li-Fraumeni syndrome

Germ-line mutations in specific genes predispose family members to cancer. Prediction of the exact tumor type and timing of cancer initiation is fundamental to the development of management strategies for these individuals. Recent advances in our understanding of the general processes that control cancer initiation may enable us to tailor more precise risk stratification. This, in turn, will lead to more effective early detection strategies, which would result in more favorable clinical outcomes. In this review, we highlight the steps and methods used to reach this futuristic model.

Telomere length inheritance and aging

Telomere shortening accompanies human aging, and premature aging syndromes are often associated with short telomeres. These two observations are central to the hypothesis that telomere length directly influences longevity. If true, genetically determined mechanisms of telomere length homeostasis should significantly contribute to variations of longevity in the human population. On the other hand, telomere shortening is also observed in the course of many aging-associated disorders but determining whether it is a cause or a consequence is not an easy task. Here, we review the most relevant experimental and descriptive data relating telomere length, as a quantitative trait, to aging and longevity.