Germline TP53 Variants Research Articles

Cancer incidence, patterns, and genotype-phenotype associations in individuals with pathogenic or likely pathogenic germline TP53 variants: an observational cohort study.

Li-Fraumeni syndrome, caused primarily by pathogenic or likely pathogenic germline TP53 variants, is a rare, variably penetrant, cancer predisposition syndrome with very high risks of cancer starting in childhood, including the risk of multiple primary malignancies over an individual's lifespan. We aimed to characterise and quantify cancer incidence, patterns, and genotype-phenotype associations in individuals with pathogenic or likely pathogenic germline TP53 variants. This observational cohort study was done in 480 carriers of pathogenic or likely pathogenic germline TP53 variants enrolled in the National Cancer Institute's referral-based longitudinal Li-Fraumeni syndrome study between Aug 1, 2011, and March 24, 2020. Data on personal and family history of cancer were obtained through study questionnaires and validated by medical records. Variants were categorised on the basis of both loss-of-function (LOF) and dominant-negative effect (DNE) properties. Cancer incidence associated with Li-Fraumeni syndrome was compared with that of the general population using the Surveillance, Epidemiology, and End Results (SEER) 1975-2017 registry. Cancer incidence was evaluated with family-clustered Cox regression models and competing risk methods. This study is registered with ClinicalTrials.gov, NCT01443468. Individuals with Li-Fraumeni syndrome had a nearly 24 times higher incidence of any cancer than the general population (standardised incidence ratio 23·9; 95% CI 21·9-26·0), with the highest comparative incidence from childhood to 30 years of age. The overall cancer incidence remained 10·3 (95% CI 7·9-13·2) times higher than that of the general population after age 50 years. In women, when considering breast cancer as a competing risk, the probability of a first diagnosis of a non-breast cancer malignancy was substantially lower than that of any first cancer (24·4% [95% CI 19·6-30·5] vs 50·4% [43·5-56·5] by age 33·7 years). Overall, DNE_LOF and notDNE_LOF variants were associated with earlier age at first and second cancer compared with notDNE_notLOF and DNE_notLOF variants. The time interval from first to second cancer was shorter among carriers whose first cancer diagnoses were later in life. Multiple cancers were diagnosed within a short timeframe in some individuals, regardless of the order of cancer occurrence. This study adds granularity to the understanding of cancer incidence and patterns in individuals with pathogenic or likely pathogenic germline TP53 variants. Integration of age range-specific cancer incidence estimates, cancer-free survival by functional variant group, the potential impact of risk-reducing mastectomy on female cancer incidence, and data on subsequent malignancies will be important for the development of strategies to optimise cancer screening and management for these individuals. Intramural Research Program, Division of Cancer Epidemiology and Genetics, National Institutes of Health.

Suspected clonal hematopoiesis as a natural functional assay of TP53 germline variant pathogenicity

PurposeSome variants identified by multigene panel testing of DNA from blood present with low variant allele fraction (VAF), often a manifestation of clonal hematopoiesis. Research has shown that the proportion of variants with low VAF is especially high in TP53, the Li-Fraumeni syndrome gene. Based on the hypothesis that variants with low VAF are positively selected as drivers of clonal hematopoiesis, we investigated the use of VAF as a predictor of TP53 germline variant pathogenicity. MethodsWe used data from 260,681 TP53 variants identified at 2 laboratories to compare the distribution of pathogenic and benign variants at different VAF intervals. ResultsLikelihood ratios toward pathogenicity associated with a VAF < 26% equated to the American College of Medical Genetics/Association of Molecular Pathology strong strength level and were applicable for 1 in 5 variants of unknown significance. ConclusionIn conclusion, detection of variants with low VAF in blood can be considered an in vivo functional assay to aid assessment of TP53 variant pathogenicity.

Quantification of Discordant Variant Interpretations in a Large Family-Based Study of Li-Fraumeni Syndrome.

The use of the American College of Medical Genetics and Genomics and the Association for Molecular Pathology guidelines has improved germline variant classification concordance, but discrepancies persist, sometimes directly affecting medical management. We evaluated variant discordance between and within families with germline TP53 variants in the National Cancer Institute's Li-Fraumeni syndrome longitudinal cohort study. Germline TP53 genetic testing results were obtained from 421 individuals in 140 families. A discordant test result was defined as a report of pathogenicity that differed between two clinical testing laboratories, between a testing laboratory and the ClinVar database, or between either the laboratory or ClinVar database and variant classification by internal study review. There were 141 variants in 140 families (one family had two different TP53 variants). Fifty-four families had discordant interpretations (54 of 140, 39%). Sixteen families had discordant classifications leading to clinically important differences in medical management (16 of 140, 11%). Interfamilial discordance was observed between four families (two different variants). Intrafamilial discordance was observed within six families. One family experienced both intrafamilial and interfamilial discordance. This large single-gene study found discordant germline TP53 variant interpretations in 39% of families studied; 11% had a variant with the potential to significantly affect medical management. This finding is especially concerning in patients with Li-Fraumeni syndrome because of their exceedingly high risks of multiple cancers and intensive cancer screening and risk-reducing recommendations. Centralized data sharing, gene-specific variant curation guidelines, and provider education for consistent variant interpretation are essential for optimal patient care.

Analysis of the Li-Fraumeni Spectrum Based on an International Germline TP53 Variant Data Set

Li-Fraumeni syndrome is a cancer predisposition syndrome that is associated with a high, lifelong risk of a broad spectrum of cancers that is caused by pathogenic TP53 germline variants. A definition that reflects the broad phenotypic spectrum that has evolved since the gene discovery is lacking, and mechanisms leading to phenotypic differences remain largely unknown. To define the phenotypic spectrum of Li-Fraumeni syndrome and conduct phenotype-genotype associations across the phenotypic spectrum. We analyzed and classified the germline variant data set of the International Agency for Research on Cancer TP53 database that contains data on a cohort of 3034 persons from 1282 families reported in the scientific literature since 1990. We defined the term Li-Fraumeni spectrum to encompass (1) phenotypic Li-Fraumeni syndrome, defined by the absence of a pathogenic/likely pathogenic TP53 variant in persons/families meeting clinical Li-Fraumeni syndrome criteria; (2) Li-Fraumeni syndrome, defined by the presence of a pathogenic/likely pathogenic TP53 variant in persons/families meeting Li-Fraumeni syndrome testing criteria; (3) attenuated Li-Fraumeni syndrome, defined by the presence of a pathogenic/likely pathogenic TP53 variant in a person/family with cancer who does not meet Li-Fraumeni syndrome testing criteria; and (4) incidental Li-Fraumeni syndrome, defined by the presence of a pathogenic/likely pathogenic TP53 variant in a person/family without a history of cancer. Data analysis occurred from November 2020 to March 2021. Differences in variant distribution and cancer characteristics in patients with a germline TP53 variant who met vs did not meet Li-Fraumeni syndrome testing criteria. Tumor spectra showed significant differences, with more early adrenal (n = 166, 6.5% vs n = 0), brain (n = 360, 14.17% vs n = 57, 7.46%), connective tissue (n = 303, 11.92% vs n = 56, 7.33%), and bone tumors (n = 279, 10.98% vs n = 3, 0.39%) in patients who met Li-Fraumeni syndrome genetic testing criteria (n = 2139). Carriers who did not meet Li-Fraumeni syndrome genetic testing criteria (n = 678) had more breast (n = 292, 38.22% vs n = 700, 27.55%) and other cancers, 45% of them occurring after age 45 years. Hotspot variants were present in both groups. Several variants were exclusively found in patients with Li-Fraumeni syndrome, while others where exclusively found in patients with attenuated Li-Fraumeni syndrome. In patients who met Li-Fraumeni syndrome genetic testing criteria, most TP53 variants were classified as pathogenic/likely pathogenic (1757 of 2139, 82.2%), whereas 40.4% (404 of 678) of TP53 variants identified in patients who did not meet the Li-Fraumeni syndrome genetic testing criteria were classified as variants of uncertain significance, conflicting results, likely benign, benign, or unknown. The findings of this cohort study suggest that this new classification, Li-Fraumeni spectrum, is a step toward understanding the factors that lead to phenotypic differences and may serve as a model for other cancer predisposition syndromes.

Molecular profiling of osteosarcoma in children and adolescents from different age groups using a next-generation sequencing panel

Osteosarcoma (OS) is a malignant bone tumor, with a peak of incidence in the second decade of life and possibly associated with the presence of germline mutations. Besides, clinicians have pointed to a second, rarer group of patients that develops OS before 10 years old. Here we access, through next-generation sequencing (NGS) strategy, the genetic alterations present in OS and blood samples from patients diagnosed before and during the second decade of life. A custom NGS panel, designed for the main alterations described in childhood and adolescence neoplasms, named Oncomine Childhood Cancer Research Assay (OCCRA©), was used. Of all 84 OS samples investigated, 42 (50%) presented some somatic variant, with TP53, MYC, CDK4, RB1 and PDGFRA genes harboring the most observed genetic variants. MYC CNVs were more frequent in tumors from patients diagnosed before 10 years old (X21= 5.18, p = 0.023). Additionally, patients diagnosed during the second decade of life presented a higher percentage of somatic and germline variants. Germline variants in TP53 and RB1 were found in 5 of the 11 (45.5%) patients analyzed. Clinical variables and tumor histopathological characteristics were also collected and correlated with our molecular findings.

Clinical and molecular characterization of patients fulfilling Chompret criteria for Li-Fraumeni syndrome in Southern Brazil.

Li-Fraumeni syndrome (LFS) is an autosomal dominant cancer predisposition syndrome caused by pathogenic germline variants in the TP53 gene, characterized by a predisposition to the development of a broad spectrum of tumors at an early age. The core tumors related to LFS are bone and soft tissue sarcomas, premenopausal breast cancer, brain tumors, adrenocortical carcinomas (ACC), and leukemias. The revised Chompret criteria has been widely used to establish clinical suspicion and support TP53 germline variant testing and LFS diagnosis. Information on TP53 germline pathogenic variant (PV) prevalence when using Chompret criteria in South America and especially in Brazil is scarce. Therefore, the aim of this study was to characterize patients that fulfilled these specific criteria in southern Brazil, a region known for its high population frequency of a founder TP53 variant c.1010G>A (p.Arg337His), as known as R337H. TP53 germline testing of 191 cancer-affected and independent probands with LFS phenotype identified a heterozygous pathogenic/likely pathogenic variant in 26 (13.6%) probands, both in the DNA binding domain (group A) and in the oligomerization domain (group B) of the gene. Of the 26 carriers, 18 (69.23%) were R337H heterozygotes. Median age at diagnosis of the first tumor in groups A and B differed significantly in this cohort: 22 and 2 years, respectively (P = 0.009). The present study shows the clinical heterogeneity of LFS, highlights particularities of the R337H variant and underscores the need for larger collaborative studies to better define LFS prevalence, clinical spectrum and penetrance of different germline TP53 pathogenic variants.

An updated quantitative model to classify missense variants in the TP53 gene: A novel multifactorial strategy.

Multigene panel testing has led to an increase in the number of variants of uncertain significance identified in the TP53 gene, associated with Li-Fraumeni syndrome. We previously developed a quantitative model for predicting the pathogenicity of P53 missense variants based on the combination of calibrated bioinformatic information and somatic to germline ratio. Here, we extended this quantitative model for the classification of P53 predicted missense variants by adding new pieces of evidence (personal and family history parameters, loss-of-function results, population allele frequency, healthy individual status by age 60, and breast tumor pathology). We also annotated which missense variants might have an effect on splicing based on bioinformatic predictions. This updated model plus annotation led to the classification of 805 variants into a clinically relevant class, which correlated well with existing ClinVar classifications, and resolved a large number of conflicting and uncertain classifications. We propose this model as a reliable approach to TP53 germline variant classification and emphasize its use in contributing to optimize TP53-specific ACMG/AMP guidelines.

Paired Tumor-Normal Sequencing Provides Insights Into the TP53-Related Cancer Spectrum in Patients With Li-Fraumeni Syndrome.

Genetic testing for Li-Fraumeni syndrome (LFS) is performed by using blood specimens from patients selected based on phenotype-dependent guidelines. This approach is problematic for understanding the LFS clinical spectrum because patients with nonclassical presentations are missed, clonal hematopoiesis-related somatic blood alterations cannot be distinguished from germline variants, and unrelated tumors cannot be differentiated from those driven by germline TP53 defects. To provide insights into the LFS-related cancer spectrum, we analyzed paired tumor-blood DNA sequencing results in 17 922 patients with cancer and distinguished clonal hematopoiesis-related, mosaic, and germline TP53 variants. Loss of heterozygosity and TP53 mutational status were assessed in tumors, followed by immunohistochemistry for p53 expression on a subset to identify those lacking biallelic TP53 inactivation. Pathogenic/likely pathogenic TP53 variants were identified in 50 patients, 12 (24.0%) of which were clonal hematopoiesis related and 4 (8.0%) of which were mosaic. Twelve (35.3%) of 34 patients with germline TP53 variants did not meet LFS testing criteria. Loss of heterozygosity of germline TP53 variant was observed in 96.0% (95% confidence interval [CI] = 79.7% to 99.9%) of core LFS spectrum-type tumors vs 45.5% (95% CI = 16.8% to 76.6%) of other tumors and 91.3% (95% CI = 72.0% to 98.9%) of tumors from patients who met LFS testing criteria vs 61.5% (95% CI = 31.6% to 86.1%) of tumors from patients who did not. Tumors retaining the wild-type TP53 allele exhibited wild-type p53 expression. Our results indicate that some TP53 variants identified in blood-only sequencing are not germline and a substantial proportion of patients with LFS are missed based on current testing guidelines. Additionally, a subset of tumors from patients with LFS do not have biallelic TP53 inactivation and may represent cancers unrelated to their germline TP53 defect.

TP53 Germline Variations Influence the Predisposition and Prognosis of Acute Lymphoblastic Leukemia in Children

Germline TP53 mutations is the genetic basis of Li-Fraumeni syndrome (LFS), a highly penetrant cancer predisposition condition. Recent reports of germline TP53 variants in children with hypodiploid acute lymphoblastic leukemia (ALL) suggest that childhood leukemia is another manifestation of LFS. However, the pattern, prevalence, and clinical relevance of pathogenic variants in TP53 in childhood ALL remain unknown.To comprehensively characterize genetic variants in TP53 in childhood ALL, we performed targeted sequencing of TP53 coding regions in 3858 children from the Children's Oncology Group front-line ALL clinical trials (COG AALL0232 and P9900). In total, 49 different non-silent coding rare TP53 variants were identifiedin 77 (2.0%) patients sequenced, including 40 missense, 1 nonsense, 6 frameshift, and 2 inframe deletion variants. To determine which TP53 variants are potentially pathogenic and related to ALL risk, we examined their experimentally-validated p53 transcriptional activity, bioinformatically-predicted damaging effects on TP53 function, and also the variant frequency in non-ALL populations. Twenty-two TP53 variants were classified as ALL risk-related (VAR), including 7 protein-truncating and 15 missense variants, all of which were either absent or exceedingly rare in non-ALL populations (i.e., allele frequency < 0.006% in the ExAC dataset). Fourteen missense VAR reside in the p53 core DNA-binding domain, with two affecting residues essential for DNA contact and seven located at residues that are important for the overall architecture of the DNA-binding surface. The 27 remaining TP53 variants were classified as “variants of unknown significance” (VUS). Together, of 3858 children in this ALL cohort, 26 (0.67%) patients had a predicted VAR and 51 (1.3%) had a VUS in the TP53 gene.We next evaluated the association of germline TP53 variants with patient demographics and ALL tumor genetic characteristics. Children with a TP53 VAR were significantly older at diagnosis (P < 0.0001), and had significantly lower leukocyte count at presentation than those with a VUS or wild-type (WT) genotype (P= 0.006). Of 26 patients carrying a germline TP53 VAR, 17 (65.4%) exhibited hypodiploidy in ALL blasts (mostly low hypoploidy or masked hypoploidy). In contrast, hypodiploid ALL was only present in 3.9% and 1.2% of children with TP53 VUS or WT genotype, respectively. The prevalence of TP53 VAR did not differ by genetic ancestry (P= 0.9). We also examined the relationship between germline TP53 variants and treatment outcomes of ALL therapy. In the COG AALL0232 cohort, the presence of a TP53 VAR was associated with a significantly lower event free survival (EFS) and overall survival (OS) compared to patients without a risk variant (hazard ratio [HR] of 2.84, P= 0.0007 for EFS; and HR of 3.13, P= 0.003 for OS). In multivariate analyses, TP53 VAR remained prognostic after adjusting for ancestry, age, leukocyte count at diagnosis, and minimal residual disease at the end of remission induction therapy (HR of 3.36, P= 0.0002 for EFS; HR of 2.88, P= 0.007 for OS). Importantly, there was a markedly higher risk of second cancers among patients with TP53 VARs compared to those with TP53 VUS or WT TP53: 5-year cumulative incidence of 25.1% vs. 0.7%, P= 5.4 × 10-11. In the COG P9900 cohort, only 4 patients harbored TP53 VAR, of whom 3 cases experienced adverse events (one patient each with ALL relapse, second cancer, or death in remission), and both EFS and OS were significantly worse than patients with TP53 VUS or WT genotype (HR of 7.14, P= 0.0008 for EFS; HR of 14.19, P= 1.1 x 10-5 for OS). Taken together, 14 of 26 patients with a TP53 VAR experienced adverse events, with 5 ALL relapses (36% of all events) and 5 second cancers (36%). This pattern of adverse events was dramatically different from those in patients with WT TP53 or VUS, for whom ALL relapse accounted for 75% of all events with only 4% as second cancers (P= 1.2 × 10-7). In fact, even within hypodiploid ALL patients who experienced adverse events, the frequency of second cancer was significantly higher in those with a TP53 VAR than those without (50% vs 5%, P= 0.01), further suggesting that germline TP53 variation was the underlying cause of second cancers in these cases.In conclusion, our findings identified germline TP53 variants as an important determinant of ALL predisposition and adverse treatment outcomes, particularly the risk of second malignant neoplasms. DisclosuresBorowitz:Beckman Coulter: Honoraria; Becton-Dickinson Biosciences: Research Funding; HTG Molecular: Honoraria. Mullighan:Loxo Oncology: Research Funding; Amgen: Consultancy. Hunger:Jazz Pharmaceuticals: Honoraria; Novartis: Consultancy; Erytech Pharmaceuticals: Consultancy; Amgen: Consultancy, Equity Ownership.

Utility of interim blood tests for cancer screening in Li-Fraumeni syndrome.

Comprehensive annual screening reduces cancer-related mortality in Li-Fraumeni syndrome (LFS), a cancer-prone disorder caused by pathogenic germline TP53 variants. Blood tests at months 4 and 8 between annual screening are recommended but their effectiveness in early cancer detection has not been established. Interim blood counts and inflammatory biomarkers were evaluated in 132 individuals with LFS (112 adults, 87 female, median age 36years [range 3-68], median follow-up 37months [range 2-70]) and test abnormalities were observed in 225 (35%). Thirteen cancers in 12 individuals were diagnosed between annual screenings but only one cancer (colorectal adenocarcinoma) was diagnosed due to an abnormal interim blood test. Fisher's exact test and generalized estimating equation models found no statistical associations between cancer diagnoses and any test abnormality. Four- and 8-monthly interim screening blood tests may not be of independent benefit for cancer detection in LFS, but annual cancer screening and personalized follow-up remain essential.

Characteristics of Li-Fraumeni Syndrome in Japan; A Review Study by the Special Committee of JSHT.

Li‐Fraumeni syndrome (LFS) is a hereditary cancer predisposition syndrome, and the majority of patients with LFS have been identified with germline variants in the p53 tumor suppressor (TP53) gene. In the past three decades, considerable case reports of TP53 germline variants have been published in Japan. To the best of our knowledge, there have been no large‐scale studies of Japanese patients with LFS. In this study, we aimed to identify Japanese patients with TP53 germline variants and to reveal the characteristics of LFS in Japan. We collected reported cases by reviewing the medical literature and cases diagnosed at the institutions of the authors. We identified 68 individuals from 48 families with TP53 germline pathogenic or likely pathogenic variants. Of the 48 families, 35 (72.9%) had missense variants, most of which were located within the DNA‐binding loop. A total of 128 tumors were identified in the 68 affected individuals. The 128 tumor sites were as follows: breast, 25; bones, 16; brain, 12; hematological, 11; soft tissues, 10; stomach, 10; lung, 10; colorectum, 10; adrenal gland, 9; liver, 4; and others, 11. Unique phenotype patterns of LFS were shown in Japan in comparison with those in a large national LFS cohort study in France. Above all, a higher frequency of patients with stomach cancer was observed in Japanese TP53 germline variant carriers. These results may provide useful information for the clinical management of LFS in Japan.

Abstract PS16-12: Double heterozygous pathogenic variants prevalence in a cohort of hereditary breast cancer patients

Abstract Significant progress has been made in the identification of inherited genetic factors underlying hereditary cancers. Inherited pathogenic variants in cancer predisposition genes that confer moderate to high risk of breast cancer (BC) are found in 10% of BC cases. Pathogenic variants in BRCA1 and BRCA2 genes are the underlying alterations in hereditary BC. Women with a pathogenic variant in BRCA1 or BRCA2 are at substantially higher risk of developing breast, ovarian and pancreatic cancers and represent 25-28% of hereditary BC cases. The gold standard for molecular diagnosis of a hereditary cancer syndrome is aNext Generation Sequencing (NGS) panel that includes all genes known to confer moderate to high-risk for BC (TP53, PTEN, CHEK2, ATM, PALB2 STK11, RAD51C and BRIP1). Identifying who is eligible to perform genetic testing remains a challenge but presently age at the time of tumor diagnosis, family history and disease stage are still the best predictors. The identification of a germline pathogenic variant enables appropriate genetic counseling, risk-reducing interventions. The detection of variants in BRCA1, BRCA2 and PALB2 may also determine treatment options in patients with advanced or metastatic disease. The known non-BRCA1/2-associated hereditary BC comprise a heterogeneous group of tumors, for most of which the prevalence of histologic and immunohistochemical (IHQ) phenotypes are yet to be identified while triple-negative BC is the most prevalent in BRCA1 carriers. The co-occurence of more than one germline pathogenic variant in BC genes is a rare event and it may affect cancer risk and penetrance is still unknown. Only a few reports on cases and series of double mutation carriers have been described in BRCA1, BRCA2, PALB2, CHEK2, BLM or NBN. In this series case we report patients with double heterozygous (DH) mutation in BC, their age at diagnosis, presence of second neoplasia and cancer phenotype in moderate and high penetrance genes on germline panels. Considering this scenario, we performed an active search among the 2651 women from the Hereditary Cancer Registry at Hospital Sirio-Libanes, São Paulo, Brazil, between January 2013 and June 2020. We have included 229 patients with a histopathological confirmation of a BC who have tested positive for pathogenic/likely pathogenic variant. Of these, 4,3% (10/229) women were identified with DH mutation in high and moderate penetrance genes in BC (table 1). All patients carried a germline pathogenic variant in at least one high-penetrance gene. A total of 7 cases (7/10) carried at least one BRCA1/2 pathogenic variant. Two women (2/10) included had developed bilateral BC. The occurrence of a second primary cancer was described in three patients (3/10). The median age at first BC diagnosis was 36,7 years old. Two BC were found to be triple negative, five cases were of Luminal subtype and one was HER2+. The age at diagnosis is similar to most hereditary BC related to those developed by BRCA1 and TP53 germline variant carriers. In this case series there is no evidence of additive effect on the risk of tumor development. Larger series of DH mutation carriers are needed to estimate the risk in double heterozygous populations and to determine whether the presence of DH have a synergistic interaction or additive effect on cancer risk. Table1 - Breast Cancer double variantsBreast Cancer double VariantsGeneVariantAge of Breast Cancer onset IHQ statusBilateral BCOther prymary neoplasia (age)BRCA1c.5266dupC36 yoER- PR- HER2 +YesPancreas (40), Lung (53)TP53c.1010G&amp;gt;ABRCA1c.4165.4166delAG32yoN/ANoBreast (37), Skin (50)PALB2c.1240C&amp;gt;TBRCA1c.5266dupC33yoER - RP- HER2 -NoNoATMc.6729_6730delAABRCA1c.3748G&amp;gt;T33yoER- PR -HER2-NoNoRECQL4c.1568_1573delinsCCCCCBRCA2c.2516dupA49yoER+ PR+ HER2 -NoNoPMS2c.2182_2184delinsGBRCA2c.8960del32yoER+ PR+ HER2-NoNoATMc.901+1G&amp;gt;ABRCA1c.1687C&amp;gt;T38yoER+NoBreast Cancer (58)NBNc.1142delC PR +MUTYHc.536A&amp;gt;G Her2-TP53c.1010G&amp;gt;A35yoN/ANoNoMUTYHc.1187G&amp;gt;AATMc.4906C&amp;gt;T42yoER+NoNoTP53c.1010G&amp;gt;APR+HER2-PALB2c.2711G&amp;gt;A37yoER+yesNoCHEK2c.319+2T&amp;gt;APR+HER2-BRCA2c.8960del32yoER+ PR+ HER2-NoNo Citation Format: Thais Megid, Maria Isabel Achatz, Janina Pontes Pisani, Mariana Cartaxo. Double heterozygous pathogenic variants prevalence in a cohort of hereditary breast cancer patients [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS16-12.

Circulating TP53 mutations are associated with early tumor progression and poor survival in pancreatic cancer patients treated with FOLFIRINOX.

Background:Biomarkers predicting treatment response may be used to stratify pancreatic ductal adenocarcinoma (PDAC) patients for therapy. The aim of this study was to identify circulating tumor DNA (ctDNA) mutations that associate with tumor progression during FOLFIRINOX chemotherapy, and overall survival (OS).Methods:Circulating cell-free DNA was analyzed with a 57 gene next-generation sequencing panel using plasma samples of 48 PDAC patients of all disease stages. Patients received FOLFIRINOX as initial treatment. Chemotherapy response was determined on CT scans as disease control (n = 30) or progressive disease (n = 18) within eight cycles of FOLFIRINOX, based on RECIST 1.1 criteria.Results:Detection of a TP53 ctDNA mutation before start of FOLFIRINOX [odds ratio (OR) 10.51, 95% confidence interval (CI) 1.40–79.14] and the presence of a homozygous TP53 Pro72Arg germline variant (OR 6.98, 95% CI 1.31–37.30) were predictors of early tumor progression during FOLFIRINOX in multivariable analysis. Five patients presented with the combination of a TP53 ctDNA mutation before start of FOLFIRINOX and the homozygous Pro72Arg variant. All five patients showed progression during FOLFIRINOX. The combination of the TP53 mutation and TP53 germline variant was associated with shorter survival (median OS 4.4 months, 95% CI 2.6–6.2 months) compared with patients without any TP53 alterations (median OS 13.0 months, 95% CI 8.6–17.4 months).Conclusion:The combination of a TP53 ctDNA mutation before start of FOLFIRINOX and a homozygous TP53 Pro72Arg variant is a promising biomarker, associated with early tumor progression during FOLFIRINOX and poor OS. The results of this exploratory study need to be validated in an independent cohort.

Specifications of the ACMG/AMP variant interpretation guidelines for germline TP53 variants.

Germline pathogenic variants in TP53 are associated with Li-Fraumeni syndrome, a cancer predisposition disorder inherited in an autosomal dominant pattern associated with a high risk of malignancy, including early-onset breast cancers, sarcomas, adrenocortical carcinomas, and brain tumors. Intense cancer surveillance for individuals with TP53 germline pathogenic variants is associated with reduced cancer-related mortality. Accurate and consistent classification of germline variants across clinical and research laboratories is important to ensure appropriate cancer surveillance recommendations. Here, we describe the work performed by the Clinical Genome Resource TP53 Variant Curation Expert Panel (ClinGen TP53 VCEP) focused on specifying the American College of Medical Genetics and Genomics and the Association for Molecular Pathology (ACMG/AMP) guidelines for germline variant classification to the TP53 gene. Specifications were developed for 20 ACMG/AMP criteria, while nine were deemed not applicable. The original strength level for the 10 criteria was also adjusted due to current evidence. Use of TP53-specific guidelines and sharing of clinical data amongexperts and clinical laboratories led to a decrease in variants of uncertain significance from 28% to 12% compared with the original guidelines. The ClinGen TP53 VCEP recommends the use of these TP53-specific ACMG/AMP guidelines as the standard strategy for TP53 germline variant classification.

Germline EGFR variants are over-represented in adolescents and young adults (AYA) with adrenocortical carcinoma.

Adrenocortical Carcinoma (ACC) is a rare endocrine tumor with poor overall prognosis and 1.5-fold overrepresentation in females. In children, ACC is associated with inherited cancer syndromes with 50-80% of childhood-ACC associated with TP53 germline variants. ACC in adolescents and young adults (AYA) is rarely due to germline TP53, IGF2, PRKAR1A and MEN1 variants. We analyzed exome sequencing data from 21 children (<15y), 32 AYA (15-39y), and 60 adults (>39y) with ACC, and retained all pathogenic, likely pathogenic, and highly prioritized variants of uncertain significance. We engineered a stable lentiviral-mutant ACC cell line, harboring an EGFR variant (p.Asp1080Asn) from a 21-year-old female without germline-TP53-variant and with aggressive ACC. We found that 4.8% of the children (P = 0.004) and 6.2% of AYA (P < 0.0001), all-female participants, harbored germline EGFR variants, compared to only 0.3% of the control group. Expanding our analysis to the RTK-RAS-MAPK pathway, we found that the RTK genes have the highest number of highly prioritized germline variants in these individuals amongst all three arms of this pathway. We showed EGFR mutant cells migrate faster and are characterized by a stem-like phenotype compared to wild type cells. While EGFR inhibitors did not affect the stemness of mutant cells, Sunitinib, a multireceptor tyrosine kinase inhibitor, significantly reduced their stem-like behavior. Our data suggest that EGFR could be a novel underlying germline predisposition factor for ACC, especially in the Childhood-AYA (C-AYA) population. Further clinical validation can improve precision oncology management of this disease, which is known to have limited therapeutic options.

Germline TP53 Testing in Breast Cancers: Why, When and How?

Simple SummaryTP53 variants detected in blood represent a main genetic cause of breast cancers occurring before 31 years of age. TP53 being included in most of the cancer gene panels, patients with breast cancer are offered germline TP53 testing, independently of the age of tumour onset and familial history. Interpretation of TP53 variants is remarkably complex, and detection of a germline disease-causing TP53 variant in a breast cancer patient has drastic medical consequences: radiotherapy contributing to the development of subsequent tumours should be, if possible, avoided. In her family, variant carriers should be offered annual follow-up, including whole-body MRI. Therefore, we consider that, in breast cancer patients, germline TP53 testing should be performed before treatment and that the decision of TP53 testing should not be systematic but based on the age of tumour onset, type of breast cancer, personal and familial history of cancer.Germline TP53 variants represent a main genetic cause of breast cancers before 31 years of age. Development of cancer multi-gene panels has resulted in an exponential increase of germline TP53 testing in breast cancer patients. Interpretation of TP53 variants, which are mostly missense, is complex and requires excluding clonal haematopoiesis and circulating tumour DNA. In breast cancer patients harbouring germline disease-causing TP53 variants, radiotherapy contributing to the development of subsequent tumours should be, if possible, avoided and, within families, annual follow-up including whole-body MRI should be offered to carriers. We consider that, in breast cancer patients, germline TP53 testing should be performed before treatment and offered systematically only to patients with: (i) invasive breast carcinoma or ductal carcinoma in situ (DCIS) before 31; or (ii) bilateral or multifocal or HER2+ invasive breast carcinoma/DCIS or phyllode tumour before 36; or (iii) invasive breast carcinoma before 46 and another TP53 core tumour (breast cancer, soft-tissue sarcoma, osteosarcoma, central nervous system tumour, adrenocortical carcinoma); or (iv) invasive breast carcinoma before 46 and one first- or second-degree relative with a TP53 core tumour before 56. In contrast, women presenting with breast cancer after 46, without suggestive personal or familial history, should not be tested for TP53.

RARE-52. RB1 GENE DELETIONS ARE THE NOVEL MECHANISM OF CHOROID PLEXUS TUMORS (CPT) ONCOGENESIS

BACKGROUNDCPTs are known to be rare TP53-dependent neoplasms, while major molecular alterations underlying tumor progression, especially in TP53-wild type cases, are still unclear.METHODS18 primary CPT, including 16 choroid plexus carcinomas (CPC) and two atypical choroid plexus papillomas (CPP), were evaluated for copy number status of 87 major oncogenes and tumor suppressor genes by nCounter Cancer CNV assay by Nanostring and TP53 and RB1 by MLPA. Germline TP53 nucleotide substitutions were analyzed by Sanger sequencing.RESULTSPathogenic germline TP53 variants were present in 4 cases confirming Li-Fraumeni syndrome (LFS). Two patients have somatic TP53 substitutions. Only one patient with LFS harbored somatic TP53 deletion. In 7 patients, heterozygous deletions of RB1 involving from 3 exons to the whole coding sequence detected by MLPA were discovered. All these findings were validated by nCounter CNV assay. Additionally, four patients have WT1 deletions, two patients – BRCA2, and in 1 case - NF1, concomitant with RB1 deletions in 3 cases. Interestingly, in one patient who faced a progression of CPP to CPC germline, RB1 deletion was detected, and in both subsequent tumors, the length of the deleted region progressively increased. Notably, that RB1 deletions are mostly mutually exclusive to TP53 substitutions. 3 of 4 patients with RB1 deletions having follow-up period >1 year faced with tumor-related adverse events.CONCLUSIONSSomatic or uncommon germline RB1 heterozygous deletions have been unraveled as a novel mechanism of aggressive CPT and could be implemented in prognosis definition schemes.

Identification and functional characterization of new missense SNPs in the coding region of the TP53 gene

Infrequent and rare genetic variants in the human population vastly outnumber common ones. Although they may contribute significantly to the genetic basis of a disease, these seldom-encountered variants may also be miss-identified as pathogenic if no correct references are available. Somatic and germline TP53 variants are associated with multiple neoplastic diseases, and thus have come to serve as a paradigm for genetic analyses in this setting. We searched 14 independent, globally distributed datasets and recovered TP53 SNPs from 202,767 cancer-free individuals. In our analyses, 19 new missense TP53 SNPs, including five novel variants specific to the Asian population, were recurrently identified in multiple datasets. Using a combination of in silico, functional, structural, and genetic approaches, we showed that none of these variants displayed loss of function compared to the normal TP53 gene. In addition, classification using ACMG criteria suggested that they are all benign. Considered together, our data reveal that the TP53 coding region shows far more polymorphism than previously thought and present high ethnic diversity. They furthermore underline the importance of correctly assessing novel variants in all variant-calling pipelines associated with genetic diagnoses for cancer.

Nearly Half of TP53 Germline Variants Predicted To Be Pathogenic in Patients With Osteosarcoma Are De Novo: A Report From the Children's Oncology Group.

To ascertain the prevalence of recurrent de novo variants among 240 pediatric patients with osteosarcoma (OS; age < 20 years) unselected for family history of cancer. The identification of de novo variants was implemented in 2 phases. In the first, we identified genes with a rare (minor allele frequency < 0.01) de novo variant in > 1 of the 95 case-parent trios examined by whole-exome sequencing (WES) who passed quality control measures. In phase 2, 145 additional patients with OS were evaluated by targeted sequencing to identify rare de novo variants in genes nominated from phase 1. Recurrent rare variants identified from phase 1 and 2 were verified as either de novo or inherited by Sanger sequencing of affected patients and their parents. Categorical and continuous data were analyzed using Fisher exact test and t tests, respectively. Among 95 case-parent trios who underwent WES, we observed 61 de novo variants in 60 genes among 47 patients, with TP53 identified as the only gene with a pathogenic or likely pathogenic (P/LP) de novo variant in more than one case-parent trio. Among all 240 patients with OS, 13 (5.4%) harbored a P/LP TP53 germline variant, of which 6 (46.2%) were confirmed to be de novo. Apart from TP53, we did not observe any other recurrent de novo P/LP variants in the case-parent trios, suggesting that new mutations in other genes are not a frequent cause of pediatric OS. That nearly half of P/LP TP53 variants in our sample were de novo suggests universal screening for germline TP53 P/LP variants among pediatric patients with OS should be considered.

Time to first treatment and P53 dysfunction in chronic lymphocytic leukaemia: results of the O-CLL1 study in early stage patients

Chronic lymphocytic leukaemia (CLL) is characterised by a heterogeneous clinical course. Such heterogeneity is associated with a number of markers, including TP53 gene inactivation. While TP53 gene alterations determine resistance to chemotherapy, it is not clear whether they can influence early disease progression. To clarify this issue, TP53 mutations and deletions of the corresponding locus [del(17p)] were evaluated in 469 cases from the O-CLL1 observational study that recruited a cohort of clinically and molecularly characterised Binet stage A patients. Twenty-four cases harboured somatic TP53 mutations [accompanied by del(17p) in 9 cases], 2 patients had del(17p) only, and 5 patients had TP53 germ-line variants. While del(17p) with or without TP53 mutations was capable of significantly predicting the time to first treatment, a reliable measure of disease progression, TP53 mutations were not. This was true for cases with high or low variant allele frequency. The lack of predictive ability was independent of the functional features of the mutant P53 protein in terms of transactivation and dominant negative potential. TP53 mutations alone were more frequent in patients with mutated IGHV genes, whereas del(17p) was associated with the presence of adverse prognostic factors, including CD38 positivity, unmutated-IGHV gene status, and NOTCH1 mutations.