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

Genetic testing for hereditary cancer syndromes in Tunisian patients: Impact on health system

INTRODUCTION

Cancer management in Africa faces diverse challenges due to limited resources, health system challenges, and other matters. Identifying hereditary cancer syndromic cases is crucial to improve clinical management and preventive care in these settings. This study aims to explore the clinicopathological features and genetic factors associated with hereditary cancer in Tunisia, a North African country with a rising cancer burden MATERIALS AND METHODS: Clinicopathological features and personal/family history of cancer were explored in 521 patients. Genetic analysis using Sanger and next-generation sequencing was performed for a set of patients RESULTS: Hereditary breast and ovarian cancer syndrome was the most frequent cluster in which 36 BRCA mutations were identified. We described a subgroup of patients with likely ''breast cancer-only syndrome'' among this cluster. Two cases of Li-Fraumeni syndrome with distinct TP53 mutations namely c.638G>A and c.733G>A have been identified. Genetic investigation also allowed the identification of a new BLM homozygous mutation (c.3254dupT) in one patient with multiple primary cancers. Phenotype-genotype correlation suggests the diagnosis of Bloom syndrome. A recurrent MUTYH mutation (c.1143_1144dup) was identified in three patients with different phenotypes CONCLUSION: Our study calls for comprehensive genetic education and the implementation of genetic screening in Tunisia and other African countries health systems, to reduce the burden of hereditary diseases and improve cancer outcomes in resource-stratified settings.

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.

The role of TP53 pathogenic variants in early-onset HER2-positive breast cancer

Breast cancer is the most frequent event in Li-Fraumeni syndrome associated with germline TP53 variants. Some studies have shown that breast cancers in women with Li-Fraumeni syndrome are commonly HER2-positive, suggesting that HER2 amplification or over-expression in a young woman may be a useful criterion to test for germline variants in the TP53 gene. We assessed the prevalence of germline TP53 variants by Sanger sequencing or next-generation sequencing in 149 women with HER2-positive breast cancer diagnosed until age 40. The pattern of HER2 amplification was evaluated with dual-probe FISH in a subset of breast carcinomas from patients with germline TP53 variants as compared with those of noncarriers. Among 149 women tested, three presented a deleterious TP53 germline variant (2%), with one patient diagnosed at age 31 and the other two with bilateral breast cancer at ages 29/33 and 28/32, respectively. Three of the 36 patients (8.3%) with the first breast cancer diagnosed at age 31 or younger presented a pathogenic TP53 variant. Additionally, all TP53 deleterious variant carriers had a first degree relative diagnosed with different early-onset cancers (frequently not belonging to the Li-Fraumeni syndrome tumor spectrum) diagnosed at age 45 or younger. Higher levels of HER2 amplification were found in breast carcinomas of TP53 pathogenic variant carriers than in those of noncarriers. Deleterious germline TP53 variants account for a small proportion of early-onset HER2-positive breast cancers, but these seem to have higher HER2 amplification ratios. All TP53 pathogenic variant carriers found in this study had the first breast carcinoma diagnosed at age 31 or younger and a first-degree relative with early-onset cancer. Further studies are needed to clarify if HER2 status in early-onset breast cancer patients, in combination with other personal and/or familial cancer history, is useful to update the TP53 testing criteria.

p53 signaling pathway polymorphisms, cancer risk and tumor phenotype in TP53 R337H mutation carriers

Li-Fraumeni and Li-Fraumeni-like syndrome (LFS/LFL) are clinically heterogeneous cancer predisposition syndromes characterized by diagnosis of early-onset and often multiple cancers with variable tumor patterns and incomplete penetrance. To date, the genetic modifiers described in LFS/LFL have been shown to map to either TP53 or its main negative regulator, MDM2. Additionally, all studies were focused on families with different TP53 germline mutations. Hence, in this study we explored the effect of the most studied polymorphisms of p53 pathway genes on clinical manifestations of individuals carrying the founder TP53 mutation R337H (n = 136) and controls (n = 186). Cancer-affected carriers had been diagnosed either with adrenocortical carcinoma (ACC, n = 29) or breast cancer (BC, n = 43). Allelic discrimation using TaqMan assay was used for genotyping MDM2 SNP 309 (rs2279744) as well as MDM4 (rs1563828) and USP7 (rs1529916) polymorphisms. We found significantly higher MDM2 SNP 309 GG genotype and G allele frequencies in the LFS cohort than in controls. Furthermore, median age at first diagnosis was earlier in MDM2 SNP309 GG carriers when compared to other genotypes for both cancers (ACC: age 1 vs. 2 years; BC: age 35 vs. 43 years, respectively), although not statistically different. The allelic and genotypic frequencies for all SNPs did not differ between cancer affected and unaffected carriers, neither between patients with ACC or BC. In conclusion, our results suggest that MDM2 SNP 309 may contribute to the LFL phenotype and also to an earlier age at diagnosis of ACC and BC cancer in carriers of the R337H founder mutation.

Contribution of de novo and mosaic TP53 mutations to Li-Fraumeni syndrome

Background

Development of tumours such as adrenocortical carcinomas (ACC), choroid plexus tumours (CPT) or female breast cancers before age 31 or multiple primary cancers belonging to the Li-Fraumeni (LFS) spectrum is, independently of the familial history, highly suggestive of a germline TP53 mutation. The aim of this study was to determine the contribution of de novo and mosaic mutations to LFS.

Methods and results

Among 328 unrelated patients harbouring a germline TP53 mutation identified by Sanger sequencing and/or QMPSF, we could show that the mutations had occurred de novo in 40 cases, without detectable parental age effect. Sanger sequencing revealed two mosaic mutations in a child with ACC and in an unaffected father of a child with medulloblastoma. Re-analysis of blood DNA by next-generation sequencing, performed at a depth above 500X, from 108 patients suggestive of LFS without detectable TP53 mutations, allowed us to identify 6 additional cases of mosaic TP53 mutations, in 2/49 children with ACC, 2/21 children with CPT, in 1/31 women with breast cancer before age 31 and in a patient who developed an osteosarcoma at age 12, a breast carcinoma and a breast sarcoma at age 35.

Conclusions

This study performed on a large series of TP53 mutation carriers allows estimating the contribution to LFS of de novo mutations to at least 14% (48/336) and suggests that approximately one-fifth of these de novo mutations occur during embryonic development. Considering the medical impact of TP53 mutation identification, medical laboratories in charge of TP53 testing should ensure the detection of mosaic mutations.

The Inherited p53 Mutation in the Brazilian Population

A common criticism of studying rare diseases is the often-limited relevance of the findings to human health. Here, we review ∼15 years of research into an unusual germline TP53 mutation (p.R337H) that began with its detection in children with adrenocortical carcinoma (ACC), a remarkably rare childhood cancer that is associated with poor prognosis. We have come to learn that the p.R337H mutation exists at a very high frequency in Southern and Southeastern Brazil, occurring in one of 375 individuals within a total population of ∼100 million. Moreover, it has been determined that carriers of this founder mutation display variable tumor susceptibility, ranging from isolated cases of pediatric ACC to Li-Fraumeni or Li-Fraumeni-like (LFL) syndromes, thus representing a significant medical issue for this country. Studying the biochemical and molecular consequences of this mutation on p53 tumor-suppressor activity, as well as the putative additional genetic alterations that cooperate with this mutation, is advancing our understanding of how p53 functions in tumor suppression in general. These studies, which originated with a rare childhood tumor, are providing important information for guiding genetic counselors and physicians in treating their patients and are already providing clinical benefit.

Implementation of next-generation sequencing for molecular diagnosis of hereditary breast and ovarian cancer highlights its genetic heterogeneity

Molecular diagnosis of hereditary breast and ovarian cancer (HBOC) by standard methodologies has been limited to the BRCA1 and BRCA2 genes. With the recent development of new sequencing methodologies, the speed and efficiency of DNA testing have dramatically improved. The aim of this work was to validate the use of next-generation sequencing (NGS) for the detection of BRCA1/BRCA2 point mutations in a diagnostic setting and to study the role of other genes associated with HBOC in Portuguese families. A cohort of 94 high-risk families was included in the study, and they were initially screened for the two common founder mutations with variant-specific methods. Fourteen index patients were shown to carry the Portuguese founder mutation BRCA2 c.156_157insAlu, and the remaining 80 were analyzed in parallel by Sanger sequencing for the BRCA1/BRCA2 genes and by NGS for a panel of 17 genes that have been described as involved in predisposition to breast and/or ovarian cancer. A total of 506 variants in the BRCA1/BRCA2 genes were detected by both methodologies, with a 100 % concordance between them. This strategy allowed the detection of a total of 39 deleterious mutations in the 94 index patients, namely 10 in BRCA1 (25.6 %), 21 in BRCA2 (53.8 %), four in PALB2 (10.3 %), two in ATM (5.1 %), one in CHEK2 (2.6 %), and one in TP53 (2.6 %), with 20.5 % of the deleterious mutations being found in genes other than BRCA1/BRCA2. These results demonstrate the efficiency of NGS for the detection of BRCA1/BRCA2 point mutations and highlight the genetic heterogeneity of HBOC.

Germline TP53 Mutations in Patients With Early-Onset Colorectal Cancer in the Colon Cancer Family Registry

IMPORTANCE

Li-Fraumeni syndrome, usually characterized by germline TP53 mutations, is associated with markedly elevated lifetime risks of multiple cancers, and has been linked to an increased risk of early-onset colorectal cancer.

OBJECTIVE

To examine the frequency of germline TP53 alterations in patients with early-onset colorectal cancer.

DESIGN, SETTING, AND PARTICIPANTS

This was a multicenter cross-sectional cohort study of individuals recruited to the Colon Cancer Family Registry (CCFR) from 1998 through 2007 (genetic testing data updated as of January 2015). Both population-based and clinic-based patients in the United States, Canada, Australia, and New Zealand were recruited to the CCFR. Demographic information, clinical history, and family history data were obtained at enrollment. Biospecimens were collected from consenting probands and families, including microsatellite instability and DNA mismatch repair immunohistochemistry results. A total of a 510 individuals diagnosed as having colorectal cancer at age 40 years or younger and lacking a known hereditary cancer syndrome were identified from the CCFR as being potentially eligible. Fifty-three participants were excluded owing to subsequent identification of germline mutations in DNA mismatch repair genes (n = 47) or biallelic MUTYH mutations (n = 6).

INTERVENTIONS

Germline sequencing of the TP53 gene was performed. Identified TP53 alterations were assessed for pathogenicity using literature and international mutation database searches and in silico prediction models.

MAIN OUTCOMES AND MEASURES

Frequency of nonsynonymous germline TP53 alterations.

RESULTS

Among 457 eligible participants (314, population-based; 143, clinic-based; median age at diagnosis, 36 years [range, 15-40 years]), 6 (1.3%; 95% CI, 0.5%-2.8%) carried germline missense TP53 alterations, none of whom met clinical criteria for Li-Fraumeni syndrome. Four of the identified TP53 alterations have been previously described in the literature in probands with clinical features of Li-Fraumeni syndrome, and 2 were novel alterations.

CONCLUSIONS AND RELEVANCE

In a large cohort of patients with early-onset colorectal cancer, germline TP53 mutations were detected at a frequency comparable with the published prevalence of germline APC mutations in colorectal cancer. With the increasing use of multigene next-generation sequencing panels in hereditary cancer risk assessment, clinicians will be faced with the challenge of interpreting the biologic and clinical significance of germline TP53 mutations in families whose phenotypes are atypical for Li-Fraumeni syndrome.

Ancestry of the Brazilian TP53 c.1010G>A (p.Arg337His, R337H) Founder Mutation: Clues from Haplotyping of Short Tandem Repeats on Chromosome 17p

Rare germline mutations in TP53 (17p13.1) cause a highly penetrant predisposition to a specific spectrum of early cancers, defining the Li-Fraumeni Syndrome (LFS). A germline mutation at codon 337 (p.Arg337His, c1010G>A) is found in about 0.3% of the population of Southern Brazil. This mutation is associated with partially penetrant LFS traits and is found in the germline of patients with early cancers of the LFS spectrum unselected for familial history. To characterize the extended haplotypes carrying the mutation, we have genotyped 9 short tandem repeats on chromosome 17p in 12 trios of Brazilian p.Arg337His carriers. Results confirm that all share a common ancestor haplotype of Caucasian/Portuguese-Iberic origin, distant in about 72–84 generations (2000 years assuming a 25 years intergenerational distance) and thus pre-dating European migration to Brazil. So far, the founder p.Arg337His haplotype has not been detected outside Brazil, with the exception of two residents of Portugal, one of them of Brazilian origin. On the other hand, increased meiotic recombination in p.Arg337His carriers may account for higher than expected haplotype diversity. Further studies comparing haplotypes in populations of Brazil and of other areas of Portuguese migration are needed to understand the historical context of this mutation in Brazil.

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.

The Brazilian founder mutation TP53 p.R337H is uncommon in Portuguese women diagnosed with breast cancer

Since the first studies reporting the TP53 p.R337H mutation as founder mutation in Southern and Southeastern Brazil, there has been controversy on its origin. Preliminary analysis of a small subset of Brazilian mutation carriers revealed that the haplotype incided on a Caucasian background. The vast majority of carriers identified today reside in Brazil or, if identified in other countries, are Brazilian immigrants. To our knowledge, the only two exceptions of carriers without a recognizable link with Brazil are two European families, from Portugal and Germany. Haplotype analysis in the Portuguese family revealed the same haplotype identified in Brazilian individuals, but in the German family, a distinct haplotype was found. Knowing that a significant proportion of women with breast cancer (BC) in Southern Brazil are p.R337H carriers, we analyzed p.R337H in a Portuguese cohort of women diagnosed with this disease. Median age at diagnosis among the first 573 patients tested was 60 years and 100 (17.4%) patients had been diagnosed at or under the age of 45 years. Mutation screening failed to identify the mutation in the 573 patients tested. These results are in contrast with the mutation frequency observed in a study including 815 BC-affected women from Brazil, in which carrier frequencies of 12.1 and 5.1% in pre- and postmenopausal women were observed, respectively. These findings suggest that the Brazilian founder mutation p.R337H, the most frequent germline TP53 mutation reported to date, is not a common germline alteration in Portuguese women diagnosed with BC.

A concurrent episode of two neoplasms in a toddler-age child

Childhood neoplasms are relatively rare and represent only about 1- 2% of the total incidence of neoplasms in United States. Concurrent episode of childhood cancer is uncommon and usually related to a cancer genetic syndrome. Li Fraumeni Syndrome refers to an autosomal dominant condition that is manifested by the development of certain cancers in early childhood and an increased lifetime risk for developing multiple primary cancers including sarcoma, breast cancer, leukemia, bone cancer, and others. We report a case of a 21-month-old girl who was found to have orbital embryonal rhabdomyosarcoma and adrenocortical tumor concurrently.