Germline TP53 Pathogenic Variants Research Articles

Functional evaluation of germline TP53 variants identified in Brazilian families at-risk for Li–Fraumeni syndrome

Germline TP53 pathogenic variants can lead to a cancer susceptibility syndrome known as Li–Fraumeni (LFS). Variants affecting its activity can drive tumorigenesis altering p53 pathways and their identification is crucial for assessing individual risk. This study explored the functional impact of TP53 missense variants on its transcription factor activity. We selected seven TP53 missense variants (c.129G > C, c.320A > G, c.417G > T, c.460G > A, c,522G > T, c.589G > A and c.997C > T) identified in Brazilian families at-risk for LFS. Variants were created through site-directed mutagenesis and transfected into SK-OV-3 cells to assess their transcription activation capabilities. Variants K139N and V197M displayed significantly reduced transactivation activity in a TP53-dependent luciferase reporter assay. Additionally, K139N negatively impacted CDKN1A and MDM2 expression and had a limited effect on GADD45A and PMAIP1 upon irradiation-induced DNA damage. Variant V197M demonstrated functional impact in all target genes evaluated and loss of Ser15 phosphorylation. K139N and V197M variants presented a reduction of p21 levels after irradiation. Our data show that K139N and V197M negatively impact p53 functions, supporting their classification as pathogenic variants. This underscores the significance of conducting functional studies on germline TP53 missense variants classified as variants of uncertain significance to ensure proper management of LFS-related cancer risks.

HGG-19. H3- AND IDH-WILDTYPE DIFFUSE PAEDIATRIC-TYPE HIGH-GRADE GLIOMA WITHMYCN-AMPLIFICATION: AN INDICATION CRITERION FOR LI-FRAUMENI SYNDROME TESTING

Abstract BACKGROUND: In the current World Health Organization (WHO) Classification of Tumors of the Central Nervous System (CNS) (5th edition), the introduction of a molecular layer to the integrated diagnosis not only helps to characterize and prognosticate paediatric CNS tumors but the molecular alteration may predict a potential therapeutic option with a targeted agent. Furthermore, certain gene alterations may be a presage of germline alterations or cancer predisposition syndromes, portending significant implications to the index patients and their families. We report a 5-year-old boy diagnosed with non-metastatic left hemispheric H3-wildtype and IDH-wildtype diffuse paediatric-type high-grade glioma with MYCN-amplification, who was subsequently found to have Li-Fraumeni syndrome. He presented with a 3-day history of facial asymmetry, unsteady gait and right sided weakness. There was no family history of malignancy. Initial MRI revealed a restricting and enhancing solid cystic lesion (5.9 x 4.3 x 5.8cm) in the left frontal-temporal-parietal region. Tumor debulking was performed. Histopathological examination by the local pathologist revealed features of high-grade glioma. Second pathology review with next generation sequencing confirmed H3-wildtype and IDH-wildtype diffuse paediatric-type high-grade glioma with MYCN-amplification and TP53 p.Y103* mutation. He was started on focal radiotherapy and oral temozolomide but succumbed to local and metastatic progressive disease. After genetic counselling, his DNA extracted from blood was sent for targeted exome sequencing and germline mutation of TP53 was demonstrated. Cascade screening of the family members were negative of TP53 mutation. Guerrini-Rousseau et al reported that 57% (n=7) of H3-wildtype and IDH-wildtype diffuse paediatric-type high-grade glioma with MYCN-amplification harboured germline TP53 pathogenic variants. This case further highlights the importance of screening of Li-Fraumeni syndrome in patient with H3-wildtype and IDH-wildtype diffuse paediatric-type high-grade glioma with MYCN-amplification even in the absence of a family history.

TP53 germline pathogenic variant frequency in anaplastic rhabdomyosarcoma: A Children's Oncology Group report.

Rhabdomyosarcoma (RMS) is a well-described cancer in Li-Fraumeni syndrome, resulting from germline TP53 pathogenic variants (PVs). RMS exhibiting anaplasia (anRMS) are associated with a high rate of germline TP53 PVs. This study provides updated estimates of the prevalence of TP53 germline PVs in RMS (3%) and anRMS (11%) from a large cohort (n=239) enrolled in five Children's Oncology Group (COG) clinical trials. Although the prevalence of germline TP53 PVs in patients with anRMS in this series is much lower than previously reported, this prevalence remains elevated. Germline evaluation for TP53 PVs should be strongly considered in patients with anRMS.

Abstract P3-05-12: A matched cohort study of the prognosis of early breast cancer in patients with Li-Fraumeni syndrome

Abstract Background: Patients with germline TP53 pathogenic variants (Li-Fraumeni syndrome - LFS) have an increased risk of breast cancer, which is the most common type of cancer in premenopausal women with LFS. These women are also at risk of other second malignancies, including radiotherapy-induced malignancies. On the other hand, little is known about the prognosis of breast cancer in patients with LFS or if the disease behavior differs from non-hereditary BC. The objective of this study was to characterize the phenotype and prognosis of early BC in patients with LFS compared to a matched cohort of patients without germline pathogenic variants (PV) related to BC. Methods: This retrospective study evaluated patients with early BC treated in an academic cancer center from Dec 1999 to Mar 2022. The LFS cohort included consecutive patients with BC who harbored a PV or likely PV of TP53. The matched control cohort (2:1) included patients with BC with no germline PV in a panel test. Primary endpoint was disease-free survival (DFS). Since LFS is associated with an increased risk of new primary malignancies, only locoregional and distant BC recurrence were considered as events in the DFS analysis. Secondary endpoints included response to systemic therapy, sites of recurrence, and breast cancer-related deaths. Results: Forty-six patients with LFS were evaluated; the control cohort included 91 matched patients. In the LFS cohort, 14 different PV or likely PV were identified, with TP53 p.R337H being the most common (n=32). Median age was 40 years in both groups. In the LFS cohort, 35% of the pts had HER2-positive BC compared to 21% in the control cohort. Primary tumors greater than 5 cm were observed in 15% of pts in the LFS cohort and 25% of pts in the control cohort. Positive lymph nodes were observed in 11% and 14%, respectively. Among 15 pts with LFS who received neoadjuvant chemotherapy, all (100%) had a response, with 5 (33%) complete responses. Thirty-five patients in the control group received neoadjuvant chemotherapy: 83% responded, with 11 (31%) presenting a complete response. With a median follow-up of 43 months, 5-year DFS rates were 82.6% (95% CI 65.1 – 91.9%) in the LFS cohort and 91.5% (95% CI 79.1 – 96.6%) in the control cohort (P=0.427). Rates and sites of recurrence, new primary BC, and deaths are detailed in the table. Conclusions: In addition to a higher risk of new primary breast cancer, LFS patients with early breast cancer had numerically higher rates of locoregional and distant recurrence in comparison with a matched cohort. Nevertheless, further studies are required to understand if these differences are due to tumor behavior particularities or to differences in therapeutic management. Recurrence and death events Citation Format: Vanessa Petry, Renata Colombo Bonadio, Daniela Jafet, Roberta Campos, Luiz Senna, Allyne Cagnacci, Laura Testa, Maria Candida Villares Fragoso, Maria del Pilar Estevez Diz. A matched cohort study of the prognosis of early breast cancer in patients with Li-Fraumeni syndrome [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P3-05-12.

A matched case-control study of the prognosis of early breast cancer in patients with Li-Fraumeni syndrome (BREAST TP53)

IntroductionBreast cancer (BC) is the most common type of cancer in premenopausal women with germline TP53 pathogenic variants (mTP53) (Li Fraumeni syndrome - LFS). However, little is known about the BC prognosis in these patients. This study analyzed the BC-related oncologic outcomes of patients with LFS. MethodsWe evaluated a cohort of LFS patients with BC in comparison with a control cohort of BC patients with no pathogenic variant in a hereditary cancer panel. The primary endpoint was recurrence-free survival (RFS). Due to the risk of second malignancies in LFS, only locoregional and distant recurrences were considered events for RFS. Secondary endpoints included rates of contralateral BC, overall survival (OS), and breast cancer-specific survival (BCSS). ResultsForty-one patients were evaluated in the mTP53 group and 82 in the control group. Median age at BC diagnosis was 40 and 41 years, respectively. The mTP53 group received less adjuvant radiotherapy than the control group (63.4% vs 93.9%, P < 0.001). Other relevant baseline characteristics and treatment received were similar between groups. 5y-RFS rates were 79.4% in the mTP53 versus 93.6% in the control group (HR 2.43, 95%CI 0.74–8.01, P = 0.143); and were not impacted by the use of adjuvant radiotherapy. 5y-BCSS rates were 92.2% and 98.6%, respectively (HR 1.87, IC95% 0.25–13.48, P = 0.534). ConclusionsOur results showed no statistically significant difference in BC-related RFS and BCSS between patients with mTP53 and a control group with no pathogenic variant. Larger multicentric studies are warranted to confirm these results.

Germline TP53 mutations undergo copy number gain years prior to tumor diagnosis

Li-Fraumeni syndrome (LFS) is a hereditary cancer predisposition syndrome associated with germline TP53 pathogenic variants. Here, we perform whole-genome sequence (WGS) analysis of tumors from 22 patients with TP53 germline pathogenic variants. We observe somatic mutations affecting Wnt, PI3K/AKT signaling, epigenetic modifiers and homologous recombination genes as well as mutational signatures associated with prior chemotherapy. We identify near-ubiquitous early loss of heterozygosity of TP53, with gain of the mutant allele. This occurs earlier in these tumors compared to tumors with somatic TP53 mutations, suggesting the timing of this mark may distinguish germline from somatic TP53 mutations. Phylogenetic trees of tumor evolution, reconstructed from bulk and multi-region WGS, reveal that LFS tumors exhibit comparatively limited heterogeneity. Overall, our study delineates early copy number gains of mutant TP53 as a characteristic mutational process in LFS tumorigenesis, likely arising years prior to tumor diagnosis.

Inherited TP53 Variants and Risk of Prostate Cancer

BackgroundInherited germline TP53 pathogenic and likely pathogenic variants (gTP53) cause autosomal dominant multicancer predisposition including Li-Fraumeni syndrome (LFS). However, there is no known association of prostate cancer with gTP53. ObjectiveTo determine whether gTP53 predisposes to prostate cancer. Design, setting, and participantsThis multi-institutional retrospective study characterizes prostate cancer incidence in a cohort of LFS males and gTP53 prevalence in a prostate cancer cohort. Outcome measurements and statistical analysisWe evaluated the spectrum of gTP53 variants and clinical features associated with prostate cancer. Results and limitationsWe identified 31 prostate cancer cases among 163 adult LFS males, including 26 of 54 aged ≥50 yr. Among 117 LFS males without prostate cancer at the time of genetic testing, six were diagnosed with prostate cancer over a median (interquartile range [IQR]) of 3.0 (1.3–7.2) yr of follow-up, a 25-fold increased risk (95% confidence interval [CI] 9.2–55; p < 0.0001). We identified gTP53 in 38 of 6850 males (0.6%) in the prostate cancer cohort, a relative risk 9.1-fold higher than that of population controls (95% CI 6.2–14; p < 0.0001; gnomAD). We observed hotspots at the sites of attenuated variants not associated with classic LFS. Two-thirds of available gTP53 prostate tumors had somatic inactivation of the second TP53 allele. Among gTP53 prostate cancer cases in this study, the median age at diagnosis was 56 (IQR: 51–62) yr, 44% had Gleason ≥8 tumors, and 29% had advanced disease at diagnosis. ConclusionsComplementary analyses of prostate cancer incidence in LFS males and gTP53 prevalence in prostate cancer cohorts suggest that gTP53 predisposes to aggressive prostate cancer. Prostate cancer should be considered as part of LFS screening protocols and TP53 considered in germline prostate cancer susceptibility testing. Patient summaryInherited pathogenic variants in the TP53 gene are likely to predispose men to aggressive prostate cancer.

Medical guidelines for Li\u2013Fraumeni syndrome 2019, version 1.1

Li–Fraumeni syndrome (LFS) is a hereditary tumor that exhibits autosomal dominant inheritance. LFS develops in individuals with a pathogenic germline variant of the cancer-suppressor gene, TP53 (individuals with TP53 pathogenic variant). The number of individuals with TP53 pathogenic variant among the general population is said to be 1 in 500 to 20,000. Meanwhile, it is found in 1.6% (median value, range of 0–6.7%) of patients with pediatric cancer and 0.2% of adult patients with cancer. LFS is diagnosed by the presence of germline TP53 pathogenic variants. However, patients can still be diagnosed with LFS even in the absence of a TP53 pathogenic variant if the familial history of cancers fit the classic LFS diagnostic criteria. It is recommended that TP53 genetic testing be promptly performed if LFS is suspected. Chompret criteria are widely used for the TP53 genetic test. However, as there are a certain number of cases of LFS that do not fit the criteria, if LFS is suspected, TP53 genetic testing should be performed regardless of the criteria. The probability of individuals with TP53 pathogenic variant developing cancer in their lifetime (penetrance) is 75% for men and almost 100% for women. The LFS core tumors (breast cancer, osteosarcoma, soft tissue sarcoma, brain tumor, and adrenocortical cancer) constitute the majority of cases; however, various types of cancers, such as hematological malignancy, epithelial cancer, and pediatric cancers, such as neuroblastoma, can also develop. Furthermore, approximately half of the cases develop simultaneous or metachronous multiple cancers. The types of TP53 pathogenic variants and factors that modify the functions of TP53 have an impact on the clinical presentation, although there are currently no definitive findings. There is currently no cancer preventive agent for individuals with TP53 pathogenic variant. Surgical treatments, such as risk-reducing bilateral mastectomy warrant further investigation. Theoretically, exposure to radiation could induce the onset of secondary cancer; therefore, imaging and treatments that use radiation should be avoided as much as possible. As a method to follow-up LFS, routine cancer surveillance comprising whole-body MRI scan, brain MRI scan, breast MRI scan, and abdominal ultrasonography (US) should be performed immediately after the diagnosis. However, the effectiveness of this surveillance is unknown, and there are problems, such as adverse events associated with a high rate of false positives, overdiagnosis, and sedation used during imaging as well as negative psychological impact. The detection rate of cancer through cancer surveillance is extremely high. Many cases are detected at an early stage, and treatments are low intensity; thus, cancer surveillance could contribute to an improvement in QOL, or at least, a reduction in complications associated with treatment. With the widespread use of genomic medicine, the diagnosis of LFS is unavoidable, and a comprehensive medical care system for LFS is necessary. Therefore, clinical trials that verify the feasibility and effectiveness of the program, comprising LFS registry, genetic counseling, and cancer surveillance, need to be prepared.

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.

Prevalence of germline TP53 variants among early-onset breast cancer patients from Polish population

BackgroundThe objective of this study was to determine spectrum and prevalence of germline mutations in TP53 gene among Polish women with early-onset breast cancer (BC), which has not been determined until now.MethodsA cohort of 100 females with BC diagnosed ≤ 30 years of age and with a positive family history of cancer was used as a discovery cohort. 1880 women with BC ≤ 45 years old and a control group of 2000 healthy women were genotyped as a replication phase of this study.ResultsFour heterozygous pathogenic missense mutations were detected in a group of 100 patients with early-onset breast cancer. On the basis of software prediction and available literature data, all these variants were defined as pathogenic. None of these TP53 variants were detected among 1880 breast cancer patients and 2000 healthy controls. No large mutations were found among early-onset cases using MLPA reaction.ConclusionGermline pathogenic TP53 variants were found in 4% early-onset Polish BC patients. No founder mutations were identified in Polish population. To improve the treatment and surveillance screening, the search for germline TP53 pathogenic variants is recommended for all female BC cases diagnosed ≤ 30 years old.

Pilot Study Assessing Tolerability and Metabolic Effects of Metformin in Patients With Li-Fraumeni Syndrome.

Li-Fraumeni syndrome (LFS) is a highly penetrant autosomal dominant cancer predisposition disorder caused by germline TP53 pathogenic variants. Patients with LFS have increased oxidative phosphorylation capacity in skeletal muscle and oxidative stress in blood. Metformin inhibits oxidative phosphorylation, reducing available energy for cancer cell proliferation and decreasing production of reactive oxygen species that cause DNA damage. Thus, metformin may provide pharmacologic risk reduction for cancer in patients with LFS, but its safety in nondiabetic patients with germline TP53 pathogenic variants has not been documented. This study assessed safety and tolerability of metformin in nondiabetic LFS patients and measured changes in metabolic profiles. Adult patients with LFS and germline TP53 variant received 14 weeks of metformin. Blood samples were obtained for measurement of serum insulin-like growth factor-1, insulin, and insulin-like growth factor binding protein 3. Hepatic mitochondrial function was assessed with fasting exhaled CO2 after ingestion of 13C-labeled methionine. Changes in serum metabolome were measured. All statistical tests were 2-sided. We enrolled 26 participants: 20 females and 6 males. The most common adverse events were diarrhea (50.0%) and nausea (46.2%). Lactic acidosis did not occur, and there were no changes in fasting glucose. Cumulative mean 13C exhalation was statistically significantly suppressed by metformin (P = .001). Mean levels of insulin-like growth factor binding protein 3 and insulin-like growth factor-1 were statistically significantly lowered (P = .02). Lipid metabolites and branched-chain amino acids accumulated. Metformin was safe and tolerable in patients with LFS. It suppressed hepatic mitochondrial function as expected in these individuals. This study adds to the rationale for development of a pharmacologic risk-reduction clinical trial of metformin in LFS.

Suggested application of HER2+ breast tumor phenotype for germline TP53 variant classification within ACMG/AMP guidelines.

Early onset breast cancer is the most common malignancy in women with Li-Fraumeni syndrome, caused by germline TP53 pathogenic variants. It has repeatedly been suggested that breast tumors from TP53 carriers are more likely to be HER2+ than those of noncarriers, but this information has not been incorporated into variant interpretation models for TP53. Breast tumor pathology is already being used quantitatively for assessing pathogenicity of germline variants in other genes, and it has been suggested that this type of evidence can be incorporated into current American College of Medical Genetics and Genomics/Association for Molecular Pathology (ACMG/AMP) guidelines for germline variant classification. Here, by reviewing published data and using internal datasets separated by different age groups, we investigated if breast tumor HER2+ status has utility as a predictor of TP53 germline variant pathogenicity, considering age at diagnosis. Overall, our results showed that the identification of HER2+ breast tumors diagnosed before the age of 40 can be conservatively incorporated into the current TP53-specific ACMG/AMP PP4 criterion, following a point system detailed in this manuscript. Further larger studies will be needed to reassess the value of HER2+ breast tumors diagnosed at a later age.

MIR605 rs2043556 is associated with the occurrence of multiple primary tumors in TP53 p.(Arg337His) mutation carriers

Li-Fraumeni and Li-Fraumeni-like (LFS/LFL) Syndrome are cancer predisposition syndromes caused by germline pathogenic variants in TP53 and are associated with an increased risk of multiple early-onset cancers. In Southern and Southeastern Brazil, a germline founder variant with partial penetrance located in the oligomerization domain of TP53, c.1010G>A p.(Arg337His, commonly known as R337H), has been detected in 0.3% of the general population. Recently, the functional MIR605 variant rs2043556 (A>G) has been identified as a novel LFS phenotype modifier in families with germline TP53 DNA binding variants. In this study, our goal was to verify MIR605 rs2043556 allele frequencies and further explore its possible effects on the phenotype of 238 Brazilian individuals carrying TP53 p.(Arg337His). The MIR605 rs2043556 G allele was detected in 136 (57.1%) individuals, including 25 homozygotes (10.5%), and although it had been previously associated with an earlier mean age of tumor onset, this effect was not observed in this study (p = 0.8). However, in p.(Arg337His) mutation carriers, the GG genotype was significantly associated with the occurrence of multiple primary tumors (p = 0.005). We provide further evidence of MIR605 rs2043556 G allele's effect as a phenotype modulator in carriers of germline TP53 pathogenic variants.

Radiotherapy-induced malignancies in breast cancer patients with TP53 pathogenic germline variants (Li-Fraumeni syndrome).

The risk of radiotherapy-induced malignancies (RIMs) is a concern when treating Li-Fraumeni syndrome (LFS) or Li-Fraumeni Like (LFL) patients. However, the type of TP53 pathogenic germline variant may possibly influence this risk. TP53 p.R337H mutation is particularly prevalent in Brazil. We aimed to evaluate the outcomes of patients with pathogenic TP53 variants treated for localized breast cancer in a Brazilian cohort. We evaluated retrospectively a cohort of patients with germline TP53 pathogenic variants treated for localized breast cancer between December 1999 and October 2017. All patients were followed by the Hereditary Cancer Group of an academic cancer center. Our primary objective was to evaluate the occurrence of RIMs after adjuvant radiotherapy. Sixteen patients were evaluated; 10 (62.5%) had a germline TP53 p.R337H pathogenic variant. Median age was 39.8years. Thirteen patients had invasive ductal carcinoma: 8 (61.5%) were hormone receptor-positive; 6 (46.1%), human epithelial growth factor receptor 2 (HER2)-amplified. Three patients had ductal carcinoma in situ. Most patients (N = 12/16, 75%) received adjuvant radiotherapy. After a median follow-up of 52.5months, 2 patients (2/12, 16.6%) had RIMs. One had a fibrosarcoma and the other, a low-grade leiomyosarcoma. In the group treated with radiotherapy, one distant recurrence was diagnosed (1/12), and no loco-regional recurrence occurred. Among 4 patients who did not receive radiotherapy, 2 presented with loco-regional recurrence. In this cohort of patients with LFS enriched in TP53 p.R337H pathogenic variant, the incidence of RIMs after treatment of localized breast cancer was lower than previous literature. Nevertheless, rates of RIMs were still alarming. Early molecular diagnosis and careful evaluation of treatment risks and benefits are essential for these patients.

Functional characterization of novel germline TP53 variants in Swedish families.

Pathogenic germline TP53 variants predispose to a wide range of early onset cancers, often recognized as the Li-Fraumeni syndrome (LFS). They are also identified in 1% of families with hereditary breast cancer (HrBC) that do not fulfill the criteria for LFS. In this study, we present a total of 24 different TP53 variants identified in 31 Swedish families with LFS or HrBC. Ten of these variants, nine exonic and one splice, have previously not been described as germline pathogenic variants. The nine exonic variants were functionally characterized and demonstrated partial transactivation activity compared to wild-type p53. Some show nuclear localization similar to wild-type p53 while others possess cytoplasmic or perinuclear localization. The four frameshift variants (W91Gfs*32, L111 Wfs*12, S227 Lfs*20 and S240Kfs*25) had negligible, while F134 L and T231del had low level of p53 activity. The L111 Wfs*12 and T231del variants are also deficient for induction of apoptosis. The missense variant R110C retain p53 effects and the nonsense E349* shows at least partial transcription factor activity but has reduced ability to trigger apoptosis. This is the first functional characterization of novel germline TP53 pathogenic or likely pathogenic variants in the Swedish cohort as an attempt to understand its association with LFS and HrBC, respectively.

P53 major hotspot variants are associated with poorer prognostic features in hereditary cancer patients

TP53 pathogenic germline variation is associated with the multi-cancer predisposition Li–Fraumeni syndrome (LFS). Next-generation sequencing and multigene panel testing are highlighting variability in the clinical presentation of patients with TP53 positive results. We aimed to investigate if the p53 variants considered as major hotspots at both germline and somatic levels (p.Arg175His, p.Gly245Asp, p.Gly245Ser, p.Arg248Gln, p.Arg248Trp, p.Arg273Cys, p.Arg273His, and p.Arg282Trp) were associated with poorer prognostic features compared to other pathogenic missense variants in the DNA-binding domain. To do so, we assessed clinical features from 1025 carriers of germline TP53 pathogenic variants (749 probands and 276 relatives) from three independent datasets (IARC TP53 Database, Ambry Single Gene Testing, and Ambry Multigene Panel Testing). We observed that, compared to carriers of non-hotspot germline variants, individuals that carried a hotspot germline variant were more likely to present with a Classic LFS phenotype, earlier age of first breast cancer onset, and shorter time to diagnosis to any cancer. Further studies with larger datasets addressing differences in cancer phenotypes by genotype are thus needed to replicate our findings and consider variant effect and position, towards future personalized clinical management of pathogenic variant carriers.

Breast cancer in patients with germline TP53 pathogenic variants have typical tumour characteristics: the Cohort study of TP53 carrier early onset breast cancer (COPE study).

Germline TP53 pathogenic variants are rare but associated with a high risk of cancer; they are often identified in the context of clinically diagnosed Li–Fraumeni syndrome predisposing to a range of young onset cancers including sarcomas and breast cancer. The study aim was to conduct a detailed morphological review and immuno‐phenotyping of breast cancer arising in carriers of a germline TP53 pathogenic variant. We compared breast cancers from five defined groups: (1) TP53 carriers with breast cancer (n = 59), (2) early onset HER2‐amplified breast cancer, no germline pathogenic variant in BRCA1/2 or TP53 (n = 55), (3) BRCA1 pathogenic variant carriers (n = 60); (4) BRCA2 pathogenic variant carriers (n = 61) and (5) young onset breast cancer with no known germline pathogenic variant (n = 98). Pathologists assessed a pre‐agreed set of morphological characteristics using light microscopy. Immunohistochemistry (IHC) for HER2, ER, PR, p53, integrin alpha v beta 6 (αvβ6) integrin, α‐smooth muscle actin (α‐SMA) and pSMAD2/3 was performed on tissue microarrays of invasive carcinoma. We confirmed a previously reported high prevalence of HER2‐amplified, ductal no special type invasive breast carcinoma amongst known TP53 germline pathogenic variant carriers 20 of 36 (56%). Furthermore we observed a high frequency of densely sclerotic tumour stroma in cancers from TP53 carriers (29/36, 80.6%) when compared with non‐carriers, 50.9% (28/55), 34.7% (50/144), 41.4% (65/157), 43.8% (95/217) in groups 2–5 respectively. The majority of germline TP53 gene carrier breast tumours had a high intensity of integrin αvβ6, α‐SMA and pSMAD2/3 expression in the majority of cancer cells. In conclusion, aggressive HER2 positive breast cancers with densely sclerotic stroma are common in germline TP53 carriers. High levels of αvβ6 integrin, α‐SMA and pSMAD2/3 expression suggest that the dense stromal phenotype may be driven by upregulated transforming growth factor beta signalling.

Cost-effectiveness of early cancer surveillance for patients with Li-Fraumeni syndrome.

Patients with germline TP53 pathogenic variants (Li-Fraumeni syndrome [LFS]) are at extremely high lifetime risk of developing cancer. Recent data suggest that tumor surveillance for patients with LFS may improve survival through early cancer detection. The objective of this study was to assess the cost-effectiveness of a cancer surveillance strategy for patients with LFS compared with those whose tumors present clinically. A Markov decision analytic model was developed from a third-party payer perspective to estimate cost-effectiveness of routine cancer surveillance over a patient's lifetime. The model consisted of four possible health states: no cancer, cancer, post-cancer survivorship, and death. Model outcomes were costs (2015 United States Dollars [USD]), effectiveness (life years [LY] gained), and incremental cost-effectiveness ratio (ICER; change in cost/LY gained). One-way sensitivity analyses and probabilistic sensitivity analyses examined parameter uncertainty. The model showed a mean cost of $46496 and $117102 and yielded 23 and 27 LY for the nonsurveillance and surveillance strategies, respectively. The ICER for early cancer surveillance versus no surveillance was $17125 per additional LY gained. At the commonly accepted willingness to pay threshold of $100000/life-year gained, surveillance had a 98% probability of being the most cost-effective strategy for early cancer detection in this high-risk population. Presymptomatic cancer surveillance is cost-effective for patients with germline pathogenic variants in TP53. Lack of insurance coverage or reimbursement in this population may have significant consequences and leads to undetected cancers presenting in later stages of disease with worse clinical outcomes.

Rare TP53 variant associated with Li-Fraumeni syndrome exhibits variable penetrance in a Saudi family

Li-Fraumeni syndrome (LFS) is an inherited, autosomal-dominant condition that predisposes individuals to a wide-spectrum of tumors at an early age. Approximately 70% of families with classic LFS have pathogenic variants in the tumor suppressor gene TP53 that disrupt protein function or stability. While more than 70% of pathogenic variants in TP53 are missense variants, the vast majority occur very infrequently, and thus their clinical significance is uncertain or conflicting. Here, we report an extremely rare TP53 missense variant, c.799C > T (p.Arg267Trp), identified in a 2-year-old Saudi proband diagnosed with choroid plexus carcinoma (CPC) and six of his first- and second-degree relatives. CPC is frequently found in families with LFS, and this is the first detailed report of a family with this variant. Intriguingly, the proband’s father is homozygous for TP53 c.799C > T and phenotypically normal at 39 years of age. While loss of TP53 heterozygosity is often observed in tumors from individuals with LFS, homozygous germline TP53 pathogenic variants are rare. Based on our analysis of this single family, we hypothesize that TP53 c.799C > T has low or variable penetrance for LFS, with predisposition to the development of CPC. The observations from this family have furthered our understanding of the phenotypic variability that may be caused by one variant of TP53, even in the same family, and suggest that other factors (genetic and/or environmental) may play a role in mechanism of disease manifestation in LFS.

Abstract PD1-06: Mosaic TP53 variants in women with breast cancer

Abstract Background: Germline TP53 pathogenic variants are indicative of Li-Fraumeni syndrome (LFS), a dominantly inherited hereditary cancer syndrome with high lifetime risks for female breast and other cancers. Genetic testing for LFS may reveal mosaicism, indicating a variant is present in some, but not all, of the cells tested. While these findings may represent a true constitutional event, mosaicism for TP53 variants also has been reported as a somatic event in lymphoblastoid cells from individuals with hematologic malignancy, previous chemotherapy exposure, or due to age-related clonal hematopoietic expansion. Understanding if a mosaic variant is constitutional can influence the patient's management and impact familial risk assessment. We present clinical history and follow-up testing from a series of female breast cancer patients with blood or oral rinse testing revealing a mosaic TP53 pathogenic or likely pathogenic variant (collectively, PV). Methods: We retrospectively reviewed clinical history and genetic testing results to identify women with a personal history of breast cancer and mosaicism for one or more TP53 PV identified on multi-gene hereditary cancer testing at our clinical diagnostic laboratory. Descriptive statistics were employed. Results: Forty-eight women with breast cancer were identified as having a mosaic TP53 PV, defined as an allelic fraction of &amp;lt;35%. Mean age at first breast cancer diagnosis was 49.2 years. Twenty children of 13 women with mosaic TP53 PV pursued targeted testing; none were positive for their mother's TP53 PV. Six of the 48 women (16.7%) pursued cultured fibroblast testing for the mosaic TP53 PV. In five, the PV was not found in fibroblasts. All five were diagnosed with breast cancer &amp;gt;40 years of age and three had other primary cancer diagnoses, including one with sarcoma. In one patient with early-onset and HER2-positive breast cancer, testing of fibroblasts also identified mosaicism for the TP53 PV, indicating constitutional mosaicism. Conclusions: For individuals with a mosaic TP53 PV, identification of the variant in a second tissue is necessary to confirm constitutional mosaicism and heightened risk for other LFS-associated cancers. In this series, additional testing confirmed one of six patients with mosaic TP53 PV pursuing fibroblast testing to have constitutional mosaicism. This individual's breast cancer was HER2-positive and her age at diagnosis was younger than those whose mosaic PV was not identified in fibroblasts. Additional follow-up testing data are needed to understand whether confirmatory testing in a second tissue is indicated for any breast cancer patient with a mosaic TP53 PV, or would be most likely to reveal constitutional mosaicism in individuals whose breast cancers are HER2-positive or early-onset. Citation Format: Mester JL, Postula K, Bissonnette J, Klein RT, Hruska K. Mosaic TP53 variants in women with breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr PD1-06.