Maria Isabel Achatz

TP53 mutations in human cancers: functional selection and impact on cancer prognosis and outcomes

A large amount of data is available on the functional impact of missense mutations in TP53 and on mutation patterns in many different cancers. New data on mutant p53 protein function, cancer phenotype and prognosis have recently been integrated in the International Agency for Research on Cancer TP53 database (http://www-p53.iarc.fr/). Based on these data, we summarize here current knowledge on the respective roles of mutagenesis and biological selection of mutations with specific functional characteristic in shaping the patterns and phenotypes of mutations observed in human cancers. The main conclusion is that intrinsic mutagenicity rates, loss of transactivation activities, and to a lesser extent, dominant-negative activities are the main driving forces that determine TP53 mutation patterns and influence tumor phenotype. In contrast, current experimental data on the acquisition of oncogenic activities (gain of function) by p53 mutants are too scarce and heterogenous to assess whether this property has an impact on tumor development and outcome. In the case of inherited TP53 mutations causing Li–Fraumeni and related syndromes, the age at onset of some tumor types is in direct relation with the degree of loss of transactivation capacity of missense mutations. Finally, studies on large case series demonstrate that TP53 mutations are independent markers of bad prognosis in breast and several other cancers, and that the exact type and position of the mutation influences disease outcome. Further studies are needed to determine how TP53 haplotypes or loss of alleles interact with mutations to modulate their impact on cancer development and prognosis.

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.

Detailed haplotype analysis at the TP53 locus in p.R337H mutation carriers in the population of Southern Brazil: evidence for a founder effect

Due to patterns of migration, selection, and population expansion, founder effects are common among humans. In Southern Brazil, a recurrent TP53 mutation, p.R337H, is detected in families with cancer predisposition. We have used whole locus resequencing and high‐density single nucleotide polymorphism (SNP) genotyping to refine TP53 locus haplotype definitions. Haplotyping of 12 unrelated p.R337H carriers using a set of 29 tag SNPs, revealed that all subjects carried the same haplotype, and presence of the mutation on this haplotype was confirmed by allele‐specific PCR. The probability that this haplotype occurs independently in all index cases was of 3.1×10−9, demonstrating a founder effect. Analysis of the patterns of 103 tumors diagnosed in 12 families showed that the presence of p.R337H is associated with multiple cancers of the Li‐Fraumeni Syndrome (LFS) spectrum, with relatively low penetrance before the age of 30 but a lifetime risk comparable to classical LFS. The p.R337H families are mostly distributed along a road axis historically known as the main route used by merchants of Portuguese origin in the XVIII and XIX century. This historical circumstance and the relatively low penetrance before the age of 30 may have contributed to the maintenance of this pathogenic mutation in a large, open population. Hum Mutat 30:1–8, 2009.

Detection of R337H, a germline TP53 mutation predisposing to multiple cancers, in asymptomatic women participating in a breast cancer screening program in Southern Brazil.

Germline TP53 mutations predispose to a rare familial cancer syndrome, the Li-Fraumeni Syndrome (LFS), characterized by the early onset of multiple cancers including childhood adrenocortical carcinomas, sarcomas and brain tumors, and breast and colon cancer in young adults. An identical germline mutation at codon 337 in TP53 (R337H) has been shown to be causally related to an increased risk of multiple cancers in unrelated subjects with familial cancer risk in Southern Brazil. Here we have assessed the prevalence of R337H in 750 healthy women participating in a community-based breast cancer screening program in the area of Porto Alegre. The mutant was detected in two participants (0.3%) who were fourth-degree relatives and reported a familial history of cancer at multiple sites that did not match classical criteria for LFS and its variants. Testing in additional family members detected the mutation in three subjects, one of whom developed breast cancer at the age of 36. These findings indicate that R337H may be a low penetrance mutant which predisposes to multiple cancers and occurs in the population of Southern Brazil at a frequency 10-20 times higher than other TP53 mutants commonly associated with LFS.

Gastric cancer in individuals with Li-Fraumeni syndrome

Purpose: Li-Fraumeni syndrome is a rare hereditary cancer syndrome associated with germline mutations in the TP53 gene. Although sarcomas, brain tumors, leukemias, breast and adrenal cortical carcinomas are typically recognized as Li-Fraumeni syndrome-associated tumors, the occurrence of gastrointestinal neoplasms has not been fully evaluated. In this analysis, we investigated the frequency and characteristics of gastric cancer in Li-Fraumeni syndrome.Methods: Pedigrees and medical records of 62 TP53 mutation-positive families were retrospectively reviewed from the Dana-Farber/National Cancer Institute Li-Fraumeni syndrome registry. We identified subjects with gastric cancer documented either by pathology report or death certificate and performed pathology review of the available specimens.Results: Among 62 TP53 mutation-positive families, there were 429 cancer-affected individuals. Gastric cancer was the diagnosis in the lineages of 21 (4.9%) subjects from 14 families (22.6%). The mean and median ages at gastric cancer diagnosis were 43 and 36 years, respectively (range: 24–74 years), significantly younger compared with the median age at diagnosis in the general population based on Surveillance Epidemiology and End Results data (71 years). Five (8.1%) families reported two or more cases of gastric cancer, and six (9.7%) families had cases of both colorectal and gastric cancers. No association was seen between phenotype and type/location of the TP53 mutations. Pathology review of the available tumors revealed both intestinal and diffuse histologies.Conclusions: Early-onset gastric cancer seems to be a component of Li-Fraumeni syndrome, suggesting the need for early and regular endoscopic screening in individuals with germline TP53 mutations, particularly among those with a family history of gastric cancer.

TP53 PIN3 and MDM2 SNP309 polymorphisms as genetic modifiers in the Li–Fraumeni syndrome: impact on age at first diagnosis

Background: Li–Fraumeni and Li–Fraumeni-like syndromes (LFS/LFL), characterised by the development of multiple early onset cancers with heterogeneous tumour patterns, are associated with germline TP53 mutations. Polymorphisms in the TP53 pathway (TP53 PEX4 at codon 72, rs1042522; MDM2 SNP309, rs2279744) have modifier effects on germline TP53 mutations that may account for the individual and familial diversity of tumour patterns. Methods and results: Four polymorphisms were analysed in a series of 135 Brazilian LFS/LFL cancer patients (32 TP53 mutation carriers and 103 wild-type subjects). We report for the first time that another polymorphism in the TP53 gene, TP53 PIN3 (rs17878362), has a strong modifier effect on germline TP53 mutations. This polymorphism, which consists of a 16 bp duplication in intron 3 (A1, non-duplicated allele; A2, duplicated allele), is associated with a difference of 19.0 years in the mean age at the first diagnosis in TP53 mutation carriers (n = 25, A1A1: 28.0 years; n = 7, A1A2: 47.0 years; p = 0.01). In addition, cancer occurrence before the age of 35 years is exclusively observed in A1A1 homozygotes. In this series, the effect of TP53 PEX4 and MDM2 SNP309 on age at diagnosis was similar to the one reported in other series and was smaller than the one of TP53 PIN3 (TP53 PIN3: difference of 19.0 years; TP53 PEX4: 8.3 years; MDM2 SNP309: 12.5 years). Conclusion: These results suggest that TP53 PIN3 is another polymorphism in the TP53 pathway that may have a modifier effect on germline TP53 mutations and may contribute to the phenotypic diversity of germline TP53 mutations associated with LFS/LFL patients.

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.

Highly prevalent TP53 mutation predisposing to many cancers in the Brazilian population: a case for newborn screening?

The unusually high population frequency of a germline TP53 mutation (R337H) predisposing to early cancer has led to mass newborn testing for this mutation in the State of Paraná, southern Brazil. Newborn screening for inherited cancer risk is complex and controversial. In this paper, we discuss the justifications for this screening by considering the medical and scientific evidence for this mutation. R337H has been identified in Brazilian families with Li-Fraumeni or related syndromes predisposing to cancers in childhood (ie, brain, renal, and adrenocortical carcinomas), adolescence (ie, soft tissue and bone sarcomas), and young adulthood (ie, breast cancer). R337H has also been detected in children with adrenocortical carcinoma without a documented family history of cancer. The mutation is estimated to occur in about 0.3% of the population in southern Brazil and is associated with increased cancer risk throughout life. Cancer patterns in families positive for R337H suggest strong genetic modifying effects, making it difficult to predict individual risk. Because protocols for cancer-risk management in Li-Fraumeni or related syndromes are debatable, extreme care should prevail in predictive testing of children for R337H. A detailed assessment of the risks, benefits, and costs is needed to ensure that medical, social, and ethical justifications for newborn screening are met.

Comprehensive Analysis of BRCA1, BRCA2 and TP53 Germline Mutation and Tumor Characterization: A Portrait of Early-Onset Breast Cancer in Brazil

Germline mutations in BRCA1, BRCA2 and TP53 genes have been identified as one of the most important disease-causing issues in young breast cancer patients worldwide. The specific defective biological processes that trigger germline mutation-associated and -negative tumors remain unclear. To delineate an initial portrait of Brazilian early-onset breast cancer, we performed an investigation combining both germline and tumor analysis. Germline screening of the BRCA1, BRCA2, CHEK2 (c.1100delC) and TP53 genes was performed in 54 unrelated patients <35 y; their tumors were investigated with respect to transcriptional and genomic profiles as well as hormonal receptors and HER2 expression/amplification. Germline mutations were detected in 12 out of 54 patients (22%) [7 in BRCA1 (13%), 4 in BRCA2 (7%) and one in TP53 (2%) gene]. A cancer familial history was present in 31.4% of the unrelated patients, from them 43.7% were carriers for germline mutation (37.5% in BRCA1 and in 6.2% in the BRCA2 genes). Fifty percent of the unrelated patients with hormone receptor-negative tumors carried BRCA1 mutations, percentage increasing to 83% in cases with familial history of cancer. Over-representation of DNA damage-, cellular and cell cycle-related processes was detected in the up-regulated genes of BRCA1/2-associated tumors, whereas cell and embryo development-related processes were over-represented in the up-regulated genes of BRCA1/2-negative tumors, suggesting distinct mechanisms driving the tumorigenesis. An initial portrait of the early-onset breast cancer patients in Brazil was generated pointing out that hormone receptor-negative tumors and positive familial history are two major risk factors for detection of a BRCA1 germline mutation. Additionally, the data revealed molecular factors that potentially trigger the tumor development in young patients.

Cancer screening recommendations for individuals with Li-Fraumeni syndrome

Li-Fraumeni syndrome (LFS) is an autosomal dominantly inherited condition caused by germline mutations of the TP53 tumor suppressor gene encoding p53, a transcription factor triggered as a protective cellular mechanism against different stressors. Loss of p53 function renders affected individuals highly susceptible to a broad range of solid and hematologic cancers. It has recently become evident that children and adults with LFS benefit from intensive surveillance aimed at early tumor detection. In October 2016, the American Association for Cancer Research held a meeting of international LFS experts to evaluate the current knowledge on LFS and propose consensus surveillance recommendations. Herein, we briefly summarize clinical and genetic aspects of this aggressive cancer predisposition syndrome. In addition, the expert panel concludes that there are sufficient existing data to recommend that all patients with LFS be offered cancer surveillance as soon as the clinical or molecular LFS diagnosis is established. Specifically, the panel recommends adoption of a modified version of the “Toronto protocol” that includes a combination of physical exams, blood tests, and imaging. The panel also recommends that further research be promoted to explore the feasibility and effectiveness of these risk-adapted surveillance and cancer prevention strategies while addressing the psychosocial needs of individuals and families with LFS. Clin Cancer Res; 23(11); e38–e45. ©2017 AACR. See all articles in the online-only CCR Pediatric Oncology Series.