Germline variant affecting p53ß isoforms predisposes to familial cancer.

Germline and somatic TP53 variants play a crucial role during tumorigenesis. However, genetic variations that solely affect the alternatively spliced p53 isoforms, p53ß and p53γ, are not fully considered in the molecular diagnosis of Li-Fraumeni syndrome and cancer. In our search for additional cancer predisposing variants, we identify a heterozygous stop-lost variant affecting the p53ß isoforms (p.*342Serext*17) in four families suspected of an autosomal dominant cancer syndrome with colorectal, breast and papillary thyroid cancers. The stop-lost variant leads to the 17 amino-acid extension of the p53ß isoforms, which increases oligomerization to canonical p53α and dysregulates the expression of p53's transcriptional targets. Our study reveals the capacity of p53ß mutants to influence p53 signalling and contribute to the susceptibility of different cancer types. These findings underscore the significance of p53 isoforms and the necessity of comprehensive investigation into the entire TP53 gene in understanding cancer predisposition.

Characterizing Lung Cancer in Li-Fraumeni Syndrome.

This cohort study describes lung cancer incidence, diagnosis, and outcome in individuals with Li-Fraumeni syndrome.

Patterns of Growth of Tumors in Li-Fraumeni Syndrome by Imaging: A Case Series.

Although tumors of Li-Fraumeni syndrome (LFS) have a premalignant or dormant phase that could be exploited by early imaging detection, this has been underevaluated in the literature. We present a case series of patients with LFS followed by imaging over time to highlight patterns of growth of tumors and hotspots of missed tumors in this population. Clinical and imaging features were available for 29 tumors of 24 carriers of a germline TP53 pathogenic variant, developed between 1999 and 2023 were retrospectively reviewed in a single tertiary pediatric center. Imaging characteristics of tumors were evaluated with MRI, CT, and radiographs. Local invasion, time interval for developing primary cancer, and/or recurrent disease and metastasis, and factors that delayed the tumor diagnosis were assessed. In patients with multiple tumors the median time intervals for development of first, second, and third primary cancers were 45.9, 79.8, and 28.1 months, respectively. Hotspots of missed tumors included superficial soft tissues, areas close to bones, on the scalp, in tissues around the adrenal region and in small hypodense lesions on brain CT. In conclusion, the pattern of growth of tumors is variable and erratic in LFS patients with some tumors presenting with a dormant pattern.

Cell-free DNA from germline TP53 mutation carriers reflect cancer-like fragmentation patterns.

Germline pathogenic TP53 variants predispose individuals to a high lifetime risk of developing multiple cancers and are the hallmark feature of Li-Fraumeni syndrome (LFS). Our group has previously shown that LFS patients harbor shorter plasma cell-free DNA fragmentation; independent of cancer status. To understand the functional underpinning of cfDNA fragmentation in LFS, we conducted a fragmentomic analysis of 199 cfDNA samples from 82 TP53 mutation carriers and 30 healthy TP53-wildtype controls. We find that LFS individuals exhibit an increased prevalence of A/T nucleotides at fragment ends, dysregulated nucleosome positioning at p53 binding sites, and loci-specific changes in chromatin accessibility at development-associated transcription factor binding sites and at cancer-associated open chromatin regions. Machine learning classification resulted in robust differentiation between TP53 mutant versus wildtype cfDNA samples (AUC-ROC = 0.710-1.000) and intra-patient longitudinal analysis of ctDNA fragmentation signal enabled early cancer detection. These results suggest that cfDNA fragmentation may be a useful diagnostic tool in LFS patients and provides an important baseline for cancer early detection.

Case report: TP53 c.848G>A germline mutation as a possible screening target at initial diagnosis for acute lymphoblastic leukemia.

BACKGROUD: Li-Fraumeni syndrome is a hereditary tumor syndrome characterized by an elevated risk of malignancy, particularly acute lymphoblastic leukemia (ALL), which can be caused by the heterozygous germline mutation. TP53 gene germline mutation is considered a potential risk factor and crucial prognostic parameter for acute leukemia development and diagnosis, but rarely occurs in adults, and its specific pathogenic significance in acute leukemia is unclear. CASE PRESENTATION: We describes a case of a 45-year-old woman diagnosed with ALL. Whole-exome sequencing approach identified one of the TP53 germline mutations from her bone marrow sample with possible pathogenic significance, c.848G>A (p.Arg283His) heterozygous missense mutation located on exon 8, which was further verified in her hair, oral mucous and nail samples. Family pedigree screening revealed that the same TP53 genetic variant was present in the patient's father and non-donor son, whereas not in the donor. Digital PCR observed that this point mutation frequency dropped post-transplantation but remained low during maintenance therapy when the patient was leukemia-free. CONCLUSION: This suspected Li-Fraumeni syndrome case report with a likely pathogenic heterozygous TP53 variant expands the cancer genetic spectrum. Screening her family members for mutations facilitates identifying the optimal relative donor and avoids unnecessary treatment by monitoring TP53 germline mutations for minimal residual disease following hematopoietic stem cell transplantation. Its potential roles in hematological malignant tumor development and clinical pathogenic implications necessitate further probing.

Selective pressures of platinum compounds shape the evolution of therapy-related myeloid neoplasms.

Therapy-related myeloid neoplasms (t-MN) arise as a complication of chemo- and/or radiotherapy. Although t-MN can occur both in adult and childhood cancer survivors, the mechanisms driving therapy-related leukemogenesis likely vary across different ages. Chemotherapy is thought to induce driver mutations in children, whereas in adults pre-existing mutant clones are selected by the exposure. However, selective pressures induced by chemotherapy early in life are less well studied. Here, we use single-cell whole genome sequencing and phylogenetic inference to show that the founding cell of t-MN in children starts expanding after cessation of platinum exposure. In patients with Li-Fraumeni syndrome, characterized by a germline TP53 mutation, we find that the t-MN already expands during treatment, suggesting that platinum-induced growth inhibition is TP53-dependent. Our results demonstrate that germline aberrations can interact with treatment exposures in inducing t-MN, which is important for the development of more targeted, patient-specific treatment regimens and follow-up.

Case series of Li-Fraumeni syndrome: carcinogenic mechanisms in breast cancer with TP53 pathogenic variant carriers.

BACKGROUND: Li-Fraumeni syndrome (LFS), a hereditary condition attributed to TP53 pathogenic variants,(PV), is associated with high risks for various malignant tumors, including breast cancer. Notably, individuals harboring TP53 PVs are more likely (67-83%) to develop HER2 + breast cancer than noncarriers (16-25%). In this retrospective study, we evaluated the associations between TP53 variants and breast cancer phenotype. METHODS: We conducted a retrospective review of the medical records of patients with LFS treated at a single institution and reviewed the literature on TP53 functions and the mechanisms underlying HER2 + breast cancer development in LFS. RESULTS: We analyzed data for 10 patients with LFS from 8 families. The median age at the onset of the first tumor was 35.5 years. Only case 2 met the classic criteria; this patient harbored a nonsense variant, whereas the other patients carried missense variants. We observed that 9 of 10 patients developed breast cancer. Immunohistochemical analyses revealed that 40% of breast cancers in patients with LFS were HR - /HER2 + . The median age at the onset of breast cancer was slightly younger in HR - /HER2 + tumors than in HR + /HER2 - tumors (31 years and 35.5 years, respectively). CONCLUSIONS: The occurrence of HER2 + breast cancer subtype was 40% in our LFS case series, which is greater than that in the general population (16-25%). Some TP53 PVs may facilitate HER2-derived oncogenesis in breast cancer. However, further studies with larger sample sizes are warranted to clarify the oncogenic mechanisms underlying each subtype of breast cancer in TP53 PV carriers.

Li-Fraumeni Syndrome: Imaging Features and Guidelines.

Li-Fraumeni syndrome (LFS) is a rare autosomal dominant familial cancer syndrome caused by germline mutations of the tumor protein p53 gene (TP53), which encodes the p53 transcription factor, also known as the "guardian of the genome." The most common types of cancer found in families with LFS include sarcomas, leukemia, breast malignancies, brain tumors, and adrenocortical cancers. Osteosarcoma and rhabdomyosarcoma are the most common sarcomas. Patients with LFS are at increased risk of developing early-onset gastric and colon cancers. They are also at increased risk for several other cancers involving the thyroid, lungs, ovaries, and skin. The lifetime risk of cancer in individuals with LFS is greater than 70% in males and greater than 90% in females. Some patients with LFS develop multiple primary cancers during their lifetime, and guidelines have been established for screening these patients. Whole-body MRI is the preferred modality for annual screening of these patients. The management guidelines for patients with LFS vary, as these individuals are more susceptible to developing radiation-induced cancers-for example, women with LFS and breast cancer are treated with total mastectomy instead of lumpectomy with radiation to the breast. The authors review the role of imaging, imaging guidelines, and imaging features of tumors in the setting of LFS. ©RSNA, 2024 Supplemental material is available for this article.

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.

TP53 p.R337H Germline Variant among Women at Risk of Hereditary Breast Cancer in a Public Health System of Midwest Brazil.

Despite the high prevalence of TP53 pathogenic variants (PV) carriers in the South and Southeast regions of Brazil, germline genetic testing for hereditary breast cancer (HBC) is not available in the Brazilian public health system, and the prevalence of Li-Fraumeni syndrome (LFS) is not well established in other regions of Brazil. We assessed the occurrence of TP53 p.R337H carriers among women treated for breast cancer (BC) between January 2021 and January 2022 at public hospitals of Brasilia, DF, Brazil. A total of 180 patients who met at least one of the NCCN criteria for HBC underwent germline testing; 44.4% performed out-of-pocket germline multigene panel testing, and 55.6% were tested for the p.R337H variant by allelic discrimination PCR. The median age at BC diagnosis was 43.5 years, 93% had invasive ductal carcinoma, 50% had estrogen receptor-positive/HER2 negative tumors, and 41% and 11% were diagnosed respectively at stage III and IV. Two patients (1.11%) harbored the p.R337H variant, and cascade family testing identified 20 additional carriers. The TP53 p.R337H detection rate was lower than that reported in other studies from south/southeast Brazil. Nonetheless, identifying TP53 PV carriers through genetic testing in the Brazilian public health system could guide cancer treatment and prevention.

Diagnostic and Practical Challenges in Applying National Comprehensive Cancer Network Guidelines for Suspected Pathogenic TP53 Mosaicism.

Benefits and limitations in using NCCN guidelines to distinguish TP53 CH from mosaic LFS.

Efficacy and Safety of Immune Checkpoint Blockade in Patients With Li-Fraumeni Syndrome.

A case series evaluating efficacy and safety of immune checkpoint blockade in Li-Fraumeni syndrome.

Molecular insights into TP53 mutation (p. Arg267Trp) and its connection to Choroid Plexus Carcinomas and Li-Fraumeni Syndrome.

BACKGROUND: Choroid plexus carcinomas (CPCs) are rare malignant tumors primarily affecting pediatric patients and often co-occur with Li-Fraumeni Syndrome (LFS), an inherited predisposition to early-onset malignancies in multiple organ systems. LFS is closely linked to TP53 mutations, with germline TP53 gene mutations present in approximately 75% of Li-Fraumeni syndrome families and 25% of Li-Fraumeni-like syndrome families. Individuals with TP53 mutations also have an elevated probability of carrying mutations in BRCA1 and BRCA2 genes. OBJECTIVE: To investigate the structural and functional implications of the TP53: 799C > T, p. (Arg267Trp) missense mutation, initially identified in a Saudi family, and understand its impact on TP53 functionality and related intermolecular interactions. METHODS: Computational analyses were conducted to examine the structural modifications resulting from the TP53: 799C > T, p. (Arg267Trp) mutation. These analyses focused on the mutation's impact on hydrogen bonding, ionic interactions, and the specific interaction with Cell Cycle and Apoptosis Regulator 2 (CCAR2), as annotated in UniProt. RESULTS: The study revealed that the native Arg267 residue is critical for a salt bridge interaction with glutamic acid at position 258. The mutation-induced charge alteration has the potential to disrupt this ionic bonding. Additionally, the mutation is located within an amino acid region crucial for interaction with CCAR2. The altered properties of the amino acid within this domain may affect its functionality and disrupt this interaction, thereby impacting the regulation of catalytic enzyme activity. CONCLUSIONS: Our findings highlight the intricate intermolecular interactions governing TP53 functionality. The TP53: 799C > T, p. (Arg267Trp) mutation causes structural modifications that potentially disrupt critical ionic bonds and protein interactions, offering valuable insights for the development of targeted mutants with distinct functional attributes. These insights could inform therapeutic strategies for conditions associated with TP53 mutations.

Cost-effectiveness of the McGill interactive pediatric oncogenetic guidelines in identifying Li-Fraumeni syndrome in female patients with osteosarcoma.

BACKGROUND: Li-Fraumeni syndrome (LFS) is a penetrant cancer predisposition syndrome (CPS) associated with the development of many tumor types in young people including osteosarcoma and breast cancer (BC). The McGill Interactive Pediatric OncoGenetic Guidelines (MIPOGG) decision-support tool provides a standardized approach to identify patients at risk of CPSs. METHODS: We conducted a cost-utility analysis, from the healthcare payer perspective, to compare MIPOGG-guided, physician-guided, and universal genetic testing strategies to detect LFS in female patients diagnosed at an age of less than 18 years with osteosarcoma. We developed a decision tree and discrete-event simulation model to simulate the clinical and cost outcomes of the three genetic referral strategies on a cohort of female children diagnosed with osteosarcoma, especially focused on BC as subsequent cancer. Outcomes included BC incidence, quality-adjusted life-years (QALYs), healthcare costs, and incremental cost-utility ratios (ICURs). We conducted probabilistic and scenario analyses to assess the uncertainty surrounding model parameters. RESULTS: Compared to the physician-guided testing, the MIPOGG-guided strategy was marginally more expensive by $105 (-$516; $743), but slightly more effective by 0.003 (-0.04; 0.045) QALYs. Compared to MIPOGG, the universal testing strategy was $1333 ($732; $1953) more costly and associated with 0.011 (-0.043; 0.064) additional QALYs. The ICUR for the MIPOGG strategy was $33,947/QALY when compared to the physician strategy; the ICUR for universal testing strategy was $118,631/QALY when compared to the MIPOGG strategy. DISCUSSION: This study provides evidence for clinical and policy decision-making on the cost-effectiveness of genetic referral strategies to identify LFS in the setting of osteosarcoma. MIPOGG-guided strategy was most likely to be cost-effective at a willingness-to-pay threshold value of $50,000/QALY.

miR-34a is a tumor suppressor in zebrafish and its expression levels impact metabolism, hematopoiesis and DNA damage.

Li-Fraumeni syndrome is caused by inherited TP53 tumor suppressor gene mutations. MicroRNA miR-34a is a p53 target and modifier gene. Interestingly, miR-34 triple-null mice exhibit normal p53 responses and no overt cancer development, but the lack of miR-34 promotes tumorigenesis in cancer-susceptible backgrounds. miR-34 genes are highly conserved and syntenic between zebrafish and humans. Zebrafish miR-34a and miR-34b/c have similar expression timing in development, but miR-34a is more abundant. DNA damage by camptothecin led to p53-dependent induction of miR-34 genes, while miR-34a mutants were adult-viable and had normal DNA damage-induced apoptosis. Nevertheless, miR-34a-/- compound mutants with a gain-of-function tp53R217H/ R217H or tp53-/- mutants were more cancer-prone than tp53 mutants alone, confirming the tumor-suppressive function of miR-34a. Through transcriptomic comparisons at 28 hours post-fertilization (hpf), we characterized DNA damage-induced transcription, and at 8, 28 and 72 hpf we determined potential miR-34a-regulated genes. At 72 hpf, loss of miR-34a enhanced erythrocyte levels and up-regulated myb-positive hematopoietic stem cells. Overexpression of miR-34a suppressed its reporter mRNA, but not p53 target induction, and sensitized injected embryos to camptothecin but not to γ-irradiation.

Identification of TP53 germline variants in pediatric patients undergoing tumor testing: strategy and prevalence.

BACKGROUND: TP53 alterations are common in certain pediatric cancers, making identification of putative germline variants through tumor genomic profiling crucial for disease management. METHODS: We analyzed TP53 alterations in 3123 tumors from 2788 pediatric patients sequenced using tumor-only or tumor-normal paired panels. Germline confirmatory testing was performed when indicated. Somatic and germline variants were classified based on published guidelines. RESULTS: In 248 tumors from 222 patients, 284 tier 1/2 TP53 sequence and small copy number variants were detected. Following germline classification, 86.6% of 142 unique variants were pathogenic or likely pathogenic. Confirmatory testing on 118 patients revealed germline TP53 variants in 28 of them (23 pathogenic or likely pathogenic and 5 of uncertain significance), suggesting a minimum Li-Fraumeni syndrome incidence of 0.8% (23/2788) in this cohort, 10.4% (23/222) in patients with TP53 variant-carrying tumors, and 19.5% (23/118) with available normal samples. About 25% (7/28) of patients with germline TP53 variants did not meet Li-Fraumeni syndrome diagnostic or testing criteria, while 20.9% (28/134) with confirmed or inferred somatic origins did. TP53 biallelic inactivation occurred in 75% of germline carrier tumors and was also prevalent in other groups, causing an elevated tumor-observed variant allelic fraction. Somatic evidence, however, including low variant allele fraction correctly identified only 27.8% (25/90) of patients with confirmed somatic TP53 variants. CONCLUSION: The high incidence and variable phenotype of Li-Fraumeni syndrome in this cohort highlights the importance of assessing germline status of TP53 variants identified in all pediatric tumors. Without clear somatic evidence, distinguishing somatic from germline origins is challenging. Classifying germline and somatic variants should follow appropriate guidelines.

Mutant p53 reactivation restricts the protumorigenic consequences of wild type p53 loss of heterozygosity in Li-Fraumeni syndrome patient-derived fibroblasts.

The p53 tumor suppressor, encoded by the TP53 gene, serves as a major barrier against malignant transformation. Patients with Li-Fraumeni syndrome (LFS) inherit a mutated TP53 allele from one parent and a wild-type TP53 allele from the other. Subsequently, the wild-type allele is lost and only the mutant TP53 allele remains. This process, which is termed loss of heterozygosity (LOH), results in only mutant p53 protein expression. We used primary dermal fibroblasts from LFS patients carrying the hotspot p53 gain-of-function pathogenic variant, R248Q to study the LOH process and characterize alterations in various pathways before and after LOH. We previously described the derivation of mutant p53 reactivating peptides, designated pCAPs (p53 Conformation Activating Peptides). In this study, we tested the effect of lead peptide pCAP-250 on LOH and on its associated cellular changes. We report that treatment of LFS fibroblasts with pCAP-250 prevents the accumulation of mutant p53 protein, inhibits LOH, and alleviates its cellular consequences. Furthermore, prolonged treatment with pCAP-250 significantly reduces DNA damage and restores long-term genomic stability. pCAPs may thus be contemplated as a potential preventive treatment to prevent or delay early onset cancer in carriers of mutant p53.

Clinical management of TP53 mosaic variants found on germline genetic testing.

BACKGROUND: Germline heterozygous TP53 pathogenic variants (PVs) cause Li Fraumeni Syndrome (LFS, OMIM#151623). TP53 PVs at lower-than-expected variant allele frequencies (VAF) may reflect postzygotic mosaicism (PZM) or clonal hematopoiesis (CH); however, no guidelines exist for workup and clinical management. PATIENTS AND METHODS: Retrospective analysis of probands who presented to an academic cancer genetics program with a TP53 PV result on germline genetic testing. RESULTS: Twenty-one of 125 unrelated probands (17 %) were found to harbor a TP53 PV with VAF<30 % or a designation of "mosaic". A diagnosis of PZM was made in nine (43 %) due to a clinical phenotype consistent with LFS with (n = 8) or without (n = 1) positive ancillary tissue testing. Twelve patients (57 %) were diagnosed with presumed CH (pCH) due to a diagnosis of a myeloproliferative neoplasm, negative ancillary tissue testing, clinical phenotype not meeting LFS criteria, no cancer, and/or no first cancer age<50. Of the 19 patients with biological offspring, nine had either partial or complete offspring testing, all negative. CONCLUSIONS: Determining the etiology of low VAF TP53 PVs requires ancillary tissue testing and incorporation of clinical phenotype. Discerning PZM versus CH is important to provide optimal care and follow-up.

Validating Risk Prediction Models for Multiple Primaries and Competing Cancer Outcomes in Families With Li-Fraumeni Syndrome Using Clinically Ascertained Data.

PURPOSE: There exists a barrier between developing and disseminating risk prediction models in clinical settings. We hypothesize that this barrier may be lifted by demonstrating the utility of these models using incomplete data that are collected in real clinical sessions, as compared with the commonly used research cohorts that are meticulously collected. MATERIALS AND METHODS: Genetic counselors (GCs) collect family history when patients (ie, probands) come to MD Anderson Cancer Center for risk assessment of Li-Fraumeni syndrome, a genetic disorder characterized by deleterious germline mutations in the TP53 gene. Our clinical counseling-based (CCB) cohort consists of 3,297 individuals across 124 families (522 cases of single primary cancer and 125 cases of multiple primary cancers). We applied our software suite LFSPRO to make risk predictions and assessed performance in discrimination using AUC and in calibration using observed/expected (O/E) ratio. RESULTS: For prediction of deleterious TP53 mutations, we achieved an AUC of 0.78 (95% CI, 0.71 to 0.85) and an O/E ratio of 1.66 (95% CI, 1.53 to 1.80). Using the LFSPRO.MPC model to predict the onset of the second cancer, we obtained an AUC of 0.70 (95% CI, 0.58 to 0.82). Using the LFSPRO.CS model to predict the onset of different cancer types as the first primary, we achieved AUCs between 0.70 and 0.83 for sarcoma, breast cancer, or other cancers combined. CONCLUSION: We describe a study that fills in the critical gap in knowledge for the utility of risk prediction models. Using a CCB cohort, our previously validated models have demonstrated good performance and outperformed the standard clinical criteria. Our study suggests that better risk counseling may be achieved by GCs using these already-developed mathematical models.