proteins

2024-07-11 | 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.

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2023-10-12 | Modified iPOND revealed the role of mutant p53 in promoting helicase function and telomere maintenance

The G-rich DNA, such as telomere, tends to form G-quadruplex (G4) structure, which slows down the replication fork progression, induces replication stress, and becomes the chromosome fragile sites.Here we described a molecular strategy that cells developed to overcome the DNA replication stress via DNA helicase regulation.The p53N236S (p53S) mutation has been found in the Werner syndrome mouse embryo fibroblast (MEFs) escaped from senescence, could be the driving force for cell escaping senescence.We revealed that the p53S could transcriptionally up-regulate DNA helicases expression, including Wrn, Blm, Timeless, Ddx, Mcm, Gins, Fanc, as well as telomere specific proteins Terf1, Pot1, through which p53S promoted the unwinding of G4 structures, and protected the cells from DNA replication stress induced by G4 stabilizer.By modified iPOND (isolation of proteins on nascent DNA) assay and telomere assay, we demonstrated that the p53S could promote the recruitment of those helicases to the DNA replication forks, facilitated the maintenance of telomere, and prevent the telomere dysfunction induced by G4 stabilizer.Interestingly, we did not observe the function of promoting G4 resolving and facilitating telomere lengthening in the cells with Li-Fraumeni Syndrome mutation-p53R172H (p53H), which suggests that this is the specific gain of function for p53S.Together our data suggest that the p53S could gain the new function of releasing the replication stress via regulating the helicase function and G4 structure, which benefits telomere lengthening.This strategy could be applied to the treatment of diseases caused by telomere replication stress.

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2023-01-07 | Joint estimation and imputation of variant functional effects using high throughput assay data

Deep mutational scanning assays enable the functional assessment of variants in high throughput. Phenotypic measurements from these assays are broadly concordant with clinical outcomes but are prone to noise at the individual variant level. We develop a framework to exploit related measurements within and across experimental assays to jointly estimate variant impact. Drawing from a large corpus of deep mutational scanning data, we collectively estimate the mean functional effect per AA residue position within each gene, normalize observed functional effects by substitution type, and make estimates for individual allelic variants with a pipeline called FUSE (Functional Substitution Estimation). FUSE improves the correlation of functional screening datasets covering the same variants, better separates estimated functional impacts for known pathogenic and benign variants (ClinVar BRCA1, p=2.24×10-51), and increases the number of variants for which predictions can be made (2,741 to 10,347) by inferring additional variant effects for substitutions not experimentally screened. For UK Biobank patients who carry a rare variant in TP53, FUSE significantly improves the separation of patients who develop cancer syndromes from those without cancer (p=1.77×10-6). These approaches promise to improve estimates of variant impact and broaden the utility of screening data generated from functional assays.

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2020-02-10 | Alternative Mechanisms of p53 Action During the Unfolded Protein Response

The tumor suppressor protein p53 orchestrates cellular responses to a vast number of stresses, with DNA damage and oncogenic activation being some of the best described. The capacity of p53 to control cellular events such as cell cycle progression, DNA repair, and apoptosis, to mention some, has been mostly linked to its role as a transcription factor. However, how p53 integrates different signaling cascades to promote a particular pathway remains an open question. One way to broaden its capacity to respond to different stimuli is by the expression of isoforms that can modulate the activities of the full-length protein. One of these isoforms is p47 (p53/47, Δ40p53, p53ΔN40), an alternative translation initiation variant whose expression is specifically induced by the PERK kinase during the Unfolded Protein Response (UPR) following Endoplasmic Reticulum stress. Despite the increasing knowledge on the p53 pathway, its activity when the translation machinery is globally suppressed during the UPR remains poorly understood. Here, we focus on the expression of p47 and we propose that the alternative initiation of p53 mRNA translation offers a unique condition-dependent mechanism to differentiate p53 activity to control cell homeostasis during the UPR. We also discuss how the manipulation of these processes may influence cancer cell physiology in light of therapeutic approaches.

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2016-09-10 | Peptides and peptidomimetics in the p53/MDM2/MDM4 circuitry - a patent review

Restoration of the p53 tumor suppressor function is an attractive anticancer strategy. Despite the development of several therapeutics targeting the two main p53 negative regulators, MDM2 and MDM4, no one has yet reached clinical application. In the past, several efforts have been employed to develop more specific and efficient compounds that can improve and/or overcome some of the features related to small molecule compounds (SMC). Peptides and peptidomimetics are emerging as attractive molecules given their increased selectivity, reduced toxicity and reduced tendency to develop tumor-resistance compared to SMC. Area covered: This article reviews publications and patents (publicly available up to April 2016) for peptides and derivatives aimed to reactivate the oncosuppressive function of p53, with a particular focus on inhibitors of MDM2/MDM4. Emphasis is placed on the efficacy of these compounds compared to the p53-reactivating small molecules developed so far. Expert opinion: A number of promising peptides for p53 reactivation in cancer therapy have been developed. These compounds appear to possess improved features compared to SMC, especially for their ability to simultaneously target the MDM2/MDM4 inhibitors, and their increased specificity.

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small molecules

2026-08-01 | Future Trends in Cancer Prevention and Interception in Cancer Predisposition Syndromes: Leveraging Insights From High-Risk Populations.

Cancer predisposition syndromes (CPS), arising from germline pathogenic variants in cancer predisposition genes (CPGs), are increasingly recognized as major contributors to pediatric and adult malignancies. Recent genomic advances have significantly enhanced the diagnosis, surveillance, and management of CPS, providing a unique framework for cancer prevention and interception of pre-malignant lesions. Increased utilization of comprehensive germline and tumor-normal sequencing has improved diagnostic precision, allowing early identification of at-risk individuals, including those with and without a family history of cancer. Integration of genome and long-read sequencing technologies further increases diagnostic yield by detecting structural and noncoding variants. Early diagnosis strategies, such as newborn screening, have demonstrated clinical utility and cost-effectiveness in population studies, such as the TP53 R337H variant newborn screening in Brazil. Evidence-based surveillance protocols, supported by outcome data, have led to earlier tumor detection and improved survival. Novel 'liquid biopsy' approaches offer minimally invasive tools for surveillance, with the potential to detect malignancies prior to radiologic findings. Beyond early detection, emerging strategies aim to intercept tumor development. Medical prevention strategies such as metformin in Li-Fraumeni syndrome and aspirin in Lynch syndrome show promise in modifying cancer risk. Immunoprevention, particularly neoantigen-targeted vaccines in mismatch repair-deficient tumors, is an evolving frontier with preliminary evidence of immunogenicity and safety. Together, these advances represent a paradigm shift in CPS management, offering a model for precision cancer prevention. Continued international collaboration, longitudinal studies, and health economic evaluations will be critical to translating these innovations into clinical and public health practice.

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2026-04-21 | Multi-omics analysis reveals the key role of STIL in Li-Fraumeni syndrome and osteosarcoma.

Li-Fraumeni syndrome (LFS), driven by germline TP53 mutations, confers a markedly elevated risk of osteosarcoma (OS), yet the mechanisms beyond TP53 remain insufficiently defined. By integrating multi-omics analyses and in vitro validation, we identify SCL-interrupting locus (STIL) as a pivotal hub linking LFS to OS progression. We reveal that STIL negatively regulates p53 protein stability in a manner independent of TP53 mutation status, indicating that STIL can promote tumorigenesis by dampening p53 pathway activity and stability. Importantly, STIL displays genetic-context-dependent oncogenicity: it supports stemness across OS models, but more strongly drives invasion and metastatic potential in TP53-mutant backgrounds. Specifically, STIL is highly expressed in a population of high-stemness malignant cells (Pro-OSCs), where it maintains stemness and promotes bone destruction by activating PTN-NCL and FN1-CD44 pathways, while simultaneously remodeling the immune microenvironment via MIF and APP signaling to evade immune surveillance. Additionally, WEE1 inhibitors may represent a targeted vulnerability in STIL-high OS. In summary, the relationship between TP53 and STIL is not a simple linear upstream-downstream cascade, but reflects a highly context-dependent regulatory dynamic. STIL exerts oncogenic effects by regulating p53 stability and driving a "stemness-invasive" phenotype in the context of TP53 mutations. This also provides novel biomarkers and intervention targets for precision therapy.

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2026-04-03 | Abstract 2886: Microbiota-driven modulation of tumor growth in Li-Fraumeni Syndrome: Evidence for bile acids as a key mediator

Abstract Li-Fraumeni Syndrome (LFS) is caused by a germline mutation in TP53, which greatly increases the risk of earlier onset malignancies. Microbial communities can regulate the host inflammation and metabolism, linking them to p53 biology. However, we do not fully understand how gut microbiome contributes to this risk. In this study, we looked at how depleting microbiota impacts tumor development in a mouse model of LFS. Trp53R172H/WT (LFS) mice and their wildtype (WT) littermates received a broad-spectrum antibiotic cocktail to deplete the gut microbiota. After four days of treatment, mice were injected subcutaneously with MC38 colon adenocarcinoma cells and continued the antibiotic treatment until study endpoint. LFS mice that received antibiotics developed significantly smaller tumors compared to untreated LFS controls, while the tumor growth in WT mice did not change. This suggests that microbial activity promotes tumor growth in mutant p53 mice. To interrogate if microbial metabolites, rather than live organisms, caused this effect, we transferred filtered fecal matter from LFS mice to WT recipients. These filtrates increased tumor size, showing that soluble microbial products can mimic the tumor-promoting effect. Faecal filtrate was analyzed with LC-MS and untreated LFS mice showed higher levels of fecal bile acids compared to WT animals. The presence of these bile acids also positively correlated with subcutaneous tumor mass, and antibiotic treatment reduced bile acid presence. We observed increased NF-κB levels in the intestines of untreated LFS mice. ELISAs further confirmed elevated intestinal pro-inflammatory cytokines expression, including IL-6, TNF-α, IFN-γ, and IL-17A, which decreased after microbiota depletion. In addition to these intestinal changes, untreated LFS mice had higher total levels of circulating plasma pro-inflammatory cytokines, which slightly decreased after antibiotic treatment. FITC-dextran assays demonstrated increased gut permeability in untreated LFS mice, returning to normal after treatment with antibiotics. Mutant p53 has been reported to enhance the mevalonate pathway, leading to increased cholesterol synthesis and an expanded pool of primary bile acids. These bile acids can then be converted by gut microbiota into secondary bile acids that have known inflammatory and NF-κB-activating effects. This combined metabolic and microbial pathway may explain the elevated bile acids and inflammatory signaling seen in LFS mice. Taken together, these data broaden the current understanding of LFS biology by revealing that tumor susceptibility is shaped not only by cell-intrinsic mutant p53 functions but also by microbiota-driven metabolic and inflammatory cues. This integrated view opens new avenues for therapeutic intervention beyond traditional surveillance-based care. Citation Format: Noel W. Ong, Camilla Giovino, Nicholas Fischer, Paula Rosanna Quaglietta, Ashby Kissoondoyal, David Malkin. Microbiota-driven modulation of tumor growth in Li-Fraumeni Syndrome: Evidence for bile acids as a key mediator [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 2886.

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2026-04-03 | Abstract 3282: Metabolic reprogramming in Li-Fraumeni Syndrome underlies the pre-cancer niche and cancer predisposition

Abstract Li-Fraumeni Syndrome (LFS) is a hereditary cancer predisposition syndrome associated with germline mutations in TP53 (mutp53). Mutp53 abrogates normal tumor-suppressive functions, including DNA repair, metabolism, and apoptosis. The accumulation of these effects, along with clonal expansion of metabolically reprogrammed cells, can enhance cell survival and adaptation to stress conditions, priming a pre-cancerous niche. We hypothesize that germline TP53 mutations alter metabolism to promote a pre-cancerous primed state. Moreover, metabolic interventions can reverse this state to reduce cancer onset in LFS. LFS (Trp53+/R172H) mice and wild-type (WT) littermates were followed across four age cohorts (60, 120, 210, 300 days) and treated with metformin-supplemented drinking water (1mg/mL) or left untreated. At endpoint, plasma, muscle, liver, kidney, spleen, thymus, and brain tissues were collected. Flow cytometry immune profiling was performed on spleen and thymus. All tissues were analyzed by LC-MS/MS untargeted proteomics and Seahorse metabolic assays. All statistics were performed in R. Splenic lymphocyte proportions did not differ between LFS and WT mice across development, however we did observe significantly different metabolic states (p<0.05). LFS mice expressed significantly higher metabolism-associated functional exhaustion markers KLRG1 and PD1 on NK cells and CD4+ T cells, respectively. Metformin treatment rescued this phenotype by significantly reduced PD1 expression on exhausted T cells (CD4+, CD8+, and CD4+CD8+ double-positive; p<0.05) in LFS mice. Tissue proteomics revealed key metabolic and developmental pathway differences in LFS mice, and the effect of longitudinal metformin on the pre-cancer niche. These pathways are being further validated through in vitro assays with patient-derived cells to help delineate the role of various cell types in LFS pre-cancer priming. We demonstrated that metabolic reprogramming occurs systemically in LFS to promote a cancer-primed state. Moreover, treatment with a metabolic modulator can aid in rescuing these changes, suggesting potential a potential cancer interception or treatment for LFS patients to revert the cancer priming phenotype. Citation Format: Paula Rosanna Quaglietta, Ashby Kissoondoyal, Noel Wei Yang Ong, Nicholas Fischer, David Malkin, . Metabolic reprogramming in Li-Fraumeni Syndrome underlies the pre-cancer niche and cancer predisposition [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 3282.

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2026-04-03 | Abstract 3329: Wnt signalling variants as modifiers of cancer susceptibility in Li-Fraumeni syndrome

Abstract Li-Fraumeni Syndrome (LFS) is a hereditary cancer predisposition syndrome associated with germline TP53 mutations, leading to a significantly increased lifetime cancer risk. Individuals with LFS display striking clinical heterogeneity, including variation in tumour onset, aggressiveness, and metastasis, highlighting the need to better understand genetic modifiers and their influence on cancer susceptibility. Recent work from our lab suggests that variation in Wnt signalling may be contributing to this clinical diversity. The Wnt pathway regulates many cellular processes, including proliferation, differentiation, and stemness. When hyperactivated, it can promote oncogenesis by stabilizing β-catenin levels, activating transcriptional programs that support tumour initiation and progression. Whole-genome sequencing on a large, multi-institutional cohort of LFS patients has identified Wnt-pathway variants that appear to decrease cancer risk and are associated with improved survival. These variants are predicted to dampen β-catenin signalling, pointing toward a novel mechanism that may act to counterbalance TP53-driven oncogenesis. To further investigate the differences contributing to heterogeneity in LFS, we are developing a proteomic atlas of patient-derived dermal fibroblasts, representing a range of clinical presentations: wild-type (n=5), clinically unaffected LFS carriers (n=7), and LFS individuals with known malignancies (n=6). Baseline protein expression was quantified using mass spectrometry, and Wnt-related proteins were identified for further testing. To explore the functional mechanisms of these variants, siRNA-mediated knockdowns will be used to examine how short-term reductions in Wnt expression affect cancer-associated cell phenotypes. Preliminary analyses have identified that LFS fibroblasts demonstrate increased expression of Wnt receptors compared to wild-type, suggesting a baseline priming towards Wnt activation. Gene set enrichment analysis demonstrated an enrichment of β-catenin, Lef1, and Myc transcriptional programs in LFS cells, consistent with a strongly activated Wnt signalling state. Together, these findings support hyperactive Wnt signalling as a defining feature of the LFS cellular environment and a contributing factor to TP53-driven oncogenesis. By integrating proteomic profiling with functional variant validation, this work examines how Wnt-modifying variants contribute to the tumorigenic environment in LFS. The results of this study will help us to better understand the biological heterogeneity seen among LFS patients and lay the groundwork for future research into Wnt modifiers as therapeutic interventions. Beyond the scope of this project, the LFS fibroblast proteomic atlas may act as a novel resource for the LFS and TP53 research communities, providing unbiased quantification of proteins across different clinical outcomes. Citation Format: Madeleine Driscoll, Paula R. Quaglietta, David Malkin, . Wnt signalling variants as modifiers of cancer susceptibility in Li-Fraumeni syndrome [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 3329.

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gene therapies

2026-02-06 | Ultra-deep duplex sequencing reveals unique features of somatic evolution in the normal tissues of a family with Li-Fraumeni syndrome.

Li-Fraumeni Syndrome (LFS) is caused by germline pathogenic variants in TP53 which predispose carriers to early onset cancer across multiple tissues. While genomically profiling those cancers has revealed factors contributing to their formation, little is understood about how LFS impacts clonal evolution in healthy tissues preceding cancer. Here, we use ultra-deep duplex sequencing (mean ~15,000× depth) to investigate somatic mutation and selection in a family carrying the germline TP53 p.R181H pathogenic variant and a cohort of non-carrier controls. In blood samples, the germline variant was associated with more mutations in a panel designed to capture genomewide mutagenesis, and with reduced positive selection on somatic TP53 mutations, despite confounding by chemotherapy treatment in one individual. DNMT3A and TET2 mutations were positively selected and GATA2 mutations were negatively selected across the cohort, independent of the p.R181H status. Extensive multi-tissue sampling of 22 non-cancerous and 6 cancerous samples was also performed at autopsy in one individual with LFS who succumbed to esophageal cancer. Cross-tissue analysis revealed excess mutations in sun-exposed skin, esophagus and chronically-inflamed stomach tissue, and highly parallel emergence of mutations in the p.R248 hotspot of TP53 across most (18/28) tissue samples. Most somatic TP53 mutations in LFS that could be assessed for phase arose on the chromosomal copy lacking the p.R181H variant. Our study reveals how the germline p.R181H variant reshapes baseline somatic mutation and selection in normal tissues and highlights the importance of understanding early somatic evolution in LFS prior to cancer development and treatment.

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2026-01-01 | High-Penetrance Susceptibility Genes in Hereditary Breast Cancer Syndromes: An Updated Review on Clinical Approach

Breast cancer remains the most prevalent malignancy worldwide, ranking second in terms of cancer-related mortality. While exposure to modifiable risk factors, variations in screening efficacy, and inaccessibility to early-stage diagnosis contrast, an increased focus has been directed toward the study of its genetic profiles; particularly those attributed to germline pathogenic variants. This narrative review aims to present the major hereditary cancer syndromes associated with an increased breast cancer risk, and to highlight the evidence-based genotype-specific screening and treatment protocols. We examined current published literature and synthesized evidence from randomized controlled trials, observational studies and current clinical guidelines. The significance of genetic testing in breast cancer extends beyond prognostic, diagnostic and risk-assessment utility, with major contributions in therapeutic decision-making. Well-defined criteria for genetic testing are established, encompassing age, familial clustering of cancer, or tumor subtype. The most prevalent hereditary cancer syndrome is the Hereditary Breast and Ovarian Cancer (HBOC) syndrome, driven by mutations in the BRCA1, BRCA2, and PALB2 genes, while other syndromes, less prevalent but with an increased risk of breast cancer development, like Li-Fraumeni syndrome and Peutz-Jeghers syndrome, arise from mutations in tumor suppressor genes. Despite the contrast in penetrance and risk profiles between the two categories, surveillance should be initiated at early ages, across all syndromes. The therapeutic approach is based on PARP (poly-(adenosine diphosphate–ribose) polymerase (PARP)) inhibitors for BRCA1/2 and PALB2 carriers, while in cases with TP53 mutations, radiotherapy is contraindicated, due to the risk of radiation-induced secondary malignancies. Germline pathogenic variant testing in high-penetrance susceptibility genes serves as the cornerstone of personalized, risk-stratified breast cancer management, enabling prevention, surveillance, and case-specific therapeutic decision-making. The broader integration of multigene panel testing and genetic counselling into routine cancer care remains a fundamental step toward optimizing outcomes across hereditary breast cancer syndromes.

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2025-09-25 | Abstract B039: Exploring the early genetic determinants of tumor risk in Li-Fraumeni Syndrome

Abstract Background Li-Fraumeni Syndrome (LFS), caused by germline pathogenic variants in the TP53 tumor suppressor gene, is a highly penetrant cancer predisposition syndrome with lifetime cancer risk approaching 100%. Surveillance protocols have led to improved survival, and it is optimal to identify patients before tumor development. LFS exhibits broad phenotypic heterogeneity in age of onset and tumor subtype, likely related to other germline genetic/epigenetic variants and early acquired somatic variants. We have previously shown that loss of heterozygosity (LOH) and mutant TP53 copy gain arise years before tumor diagnosis (Light N, 2023). Hypothesis TP53 LOH and other somatic cancer driver mutations arise prenatally, with further clonal evolution after birth, and dictate the postnatal tumor risk in LFS. Aims Explore prenatal cancer driver mutations and their postnatal clonal evolution to define tumor risk in LFS. Methods We have recruited 20 children with LFS and collected their clinical history. Their archived Newborn Screening Dried Blood Spots (DBS), and those from 5 healthy controls, will be sequenced (leukocyte genomic DNA and cell-free DNA) using a deep, comprehensive cancer gene panel (905 genes) and Whole Genome Sequencing. Sequencing data will be analyzed using our established bioinformatic pipeline. We will focus on TP53 LOH and established cancer driver mutations seen in tumors associated with LFS, accompanied by global mutational landscape analysis. These findings will be compared to sequencing data from matched postnatal germline and tumor samples, accessible through our previous genomic studies. Results 25 participants have been enrolled in our study: 5 controls and 20 children with LFS, of which 65% (13/20) are female. 55% (11/20) have had a prior malignancy, one each of osteosarcoma, CNS sarcoma, and low grade glioma, two each of acute lymphoblastic leukemia, rhabdomyosarcoma and adrenocortical carcinoma, and four with astrocytoma. 15% (3/20) have a history of two prior malignancies. 35% (7/20) have had paired tumor/germline sequencing through the KiCS (Kids Cancer Sequencing) Program or the SickKids LFS registry. DNA extraction is currently underway for the first 10 DBS samples from patients with LFS, followed by DNA sequencing and analysis. Impact The data will provide critical insights into the prenatal origin of cancer and the unique clonal evolution related to cancer development. Our study has the potential to impact surveillance practices and discover new links between prenatally acquired mutations and pediatric cancers, which may reveal novel approaches for early therapeutic interception and prevention. Citation Format: Laura Raiti, Tanvi Anandampillai, Anita Villani, Adam Shlien, David Malkin, Yiming Wang. Exploring the early genetic determinants of tumor risk in Li-Fraumeni Syndrome [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Discovery and Innovation in Pediatric Cancer— From Biology to Breakthrough Therapies; 2025 Sep 25-28; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2025;85(18_Suppl_2):Abstract nr B039.

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2025-06-26 | p53 prophylactic therapy for cancer prevention.

Germline mutations in the tumor suppressor TP53 lead to cancer predisposition, as seen in Li-Fraumeni syndrome (LFS). Currently, no strategies exist to delay or prevent cancer development in this population. Our work is based on the hypothesis that modulating wild-type p53 levels could serve as a prophylactic approach to mitigate cancer risk. By introducing a third copy of Trp53, either constitutively or in an inducible manner in adulthood, we demonstrate that tumor development is delayed, and mice live longer without observable side effects in both the Eu-myc lymphoma and LFS models. Mechanistically, Trp53 loss of heterozygosity is reduced in the LFS model, accompanied by an enhanced p53 transcriptional response. Our findings therefore provide genetic evidence supporting this approach, which could be leveraged to identify compounds that modulate p53 levels and benefit LFS carriers and other cancer-prone populations with reduced p53 activity.

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2025-05-28 | Use of AlphaFold 2 to predict stabilizing mutations for the R337H variant in the tetramerization domain of TP53.

e15118 Background: TP53 mutations occur in nearly 50% of human cancers, profoundly affecting protein structure and function. The R337H variant is the most common germline mutation in TP53, associated with Li-Fraumeni syndrome. Unlike most TP53 mutations, which occur in the DNA-binding domain (DBD, residues 102–292), R337H is uniquely located in the alpha helix of the tetramerization (TET) domain (residues 325–355). This mutation destabilizing the protein tetramer and impairing p53’s tumor-suppressor function. Leveraging AlphaFold 2 (AF2), we aimed to identify stabilizing mutations that could restore function to the R337H variant. Methods: AF2 was used to generate structural predictions of wild-type and mutated TP53 variants as implemented in ColabFold. RMSD values (Å) were calculated using PyMOL version 2.6.1. PyMOL's alignment algorithms (align, super, and cealign) were applied to quantify deviations in both the DBD and TET domains. Mutations were considered stabilizing if they showed agreement across all alignment algorithms and achieved ≥40% reduction in RMSD. To validate AF2's predictive capability, we analyzed the pathological mutation R249S in the DBD and its known compensatory mutation H168R, which has been experimentally demonstrated to stabilize p53 function. For R337H, we systematically introduced amino acid substitutions across all positions in the TET domain (residues 325–355), generating 589 double-mutant variants (R337H plus one additional substitution). Results: AF2 accurately predicted stabilization of R249S by H168R, with RMSD reductions utilizing the super alignment method in the DBD from 1.3 Å to 0.4 Å (68.2%) and in the TET domain from 10.8 Å to 5.2 Å (51.5%), with similar results with the align and CEalign methods. For the R337H germline variant, the RMSD of the TET domain using the super, align, and cealign methods was 10.6 Å, 11.8 Å, and 12.5 Å, respectively. Among 589 double-mutant variants, five substitutions: A347W, E336C, E339I, E343T, and E349D, reduced TET RMSD by ≥40% across all alignment methods. A347W reduced RMSD from 10.6 Å to 6.2 Å (41.9%), from 11.8 Å to 5.0 Å (57.7%), and from 12.5 Å to 6.1 Å (51.1%) in the super, align, and cealign methods, respectively. Similarly, E336C reduced RMSD from 10.6 Å to 5.4 Å (48.9%), from 11.8 Å to 5.5 Å (53.7%), and from 12.5 Å to 7.5 Å (40.2%). Comparable reductions were observed for E339I, E343T, and E349D. RMSD deviations in the DBD domain remained low ( < 1.5 Å across methods) for all analyzed variants, with no destabilizing effects observed Conclusions: AlphaFold 2 predicts five stabilizing mutations for the R337H germline variant which stabilize the TET domain while preserving the integrity of the DNA-binding domain. These findings provide candidates for experimental validation and clinical application. Gene editing techniques such as CRISPR-CAS9 are especially favored due to lack of functional TP53 interference.

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antibodies

2026-02-26 | Exceptional Response to a Single Dose of Pembrolizumab as Salvage Therapy for Metastatic Adrenocortical Carcinoma.

A 19-year-old woman presented with severe hypertension, hypokalemia, and clinical signs of Cushing syndrome (CS). Computed tomography imaging revealed a large left adrenal mass encasing a major vessel, a left renal lesion, a right ovarian teratoma, and multiple pulmonary micronodules. 18F-fluorodeoxyglucose positron emission tomography (18-FDG-PET) showed hypermetabolism in the adrenal mass, lung nodules, and teratoma. Biochemical work-up confirmed adrenocorticotropin-independent CS and elevated adrenal androgens, consistent with metastatic, unresectable adrenocortical carcinoma. The patient was started on mitotane and metyrapone, followed by 8 cycles of etoposide-doxorubicin-cisplatin plus mitotane. Despite treatment, the disease progressed. Adrenal biopsy revealed high tumor-infiltrating lymphocytes, low tumor mutation burden, low programmed death-ligand 1 expression, and microsatellite stability. Germline testing identified a TP53 pathogenic variant, confirming Li-Fraumeni syndrome. A single dose of pembrolizumab was administered as salvage therapy but led to grade 3 immune-related hepatitis and prolonged hospitalization, requiring cessation of both pembrolizumab and mitotane. Remarkably, a follow-up scan 3 months later showed 60% regression of the adrenal mass, stable renal and ovarian lesions, and resolution of lung nodules. The patient underwent complete surgical resection, achieving full remission. More than 1 year later, she remains disease free.

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2026-01-07 | Clinical Features and Treatment Strategies of Li-Fraumeni Syndrome Patients With Inherited TP53 Mutations.

Li-Fraumeni syndrome is a rare autosomal dominant disorder caused by a pathogenic mutation of the tumor suppressor gene TP53. This disease starts at an early age and has been shown to be associated with multiple tumors. The study aims to discuss the clinical and genetic characteristics of Li-Fraumeni syndrome (LFS) and to provide therapeutic experience of LFS. We conducted a retrospective analysis of the clinicopathologic features, family history, treatment and follow-up in five LFS patients with germline TP53 (NCBI Gene: 7157, HGNC: 11998, OMIM: 191170) pathogenic/likely pathogenic (P/LP) variants. This research had been approved by the ethics committee and implemented. Our study involved five LFS patients with germline TP53 P/LP variants, including thyroid cancer, ovarian melanoma, colon cancer, fibrosarcoma, and lung cancer. Among this group of patients, the age at which tumors first appeared was between 24 and 53 years old. Three patients had a family history of tumors, and the other two were probands in the family. Traditional chemotherapy has limited effectiveness in clinical practice and may increase the risk of tumor development. However, immune checkpoint inhibitors (ICIs) have shown unexpected efficacy in patients with high programmed cell death ligand-1 (PD-L1) expression. Next-generation sequencing (NGS) and PD-L1 detection may provide more potential targets for LFS patients to achieve better therapeutic outcomes. In addition, we have added a new TP53 frameshift mutation spectrum, namely c.642_643delTA (p.H214Qfs*7), which belongs to the pathogenic variant. This mutant has not been described in the existing literature. Patients with LFS may be potential beneficiaries of immune checkpoint inhibitors and targeted therapies.

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2025-11-05 | Melanoma of the Choroid and Ciliary Body in Children: Remission of Metastatic Melanoma of the Choroid After Treatment With Chemotherapy and Immune Checkpoint Inhibition.

Uveal melanoma is the most common malignant primary intraocular tumor in adults, associated with high mortality. Pediatric uveal melanoma generally has a more favorable course. However, when metastasis occurs, therapeutic options are limited. Clinical presentation, treatment, and outcome of children with uveal melanoma diagnosed in Germany and Austria between 2013 and 2024 were analyzed. Since 2013, 12 children were diagnosed with uveal melanoma in Germany and Austria-nine in the choroid, three in the ciliary body, and iris. Treatment comprised enucleation (five patients), external beam radiation with protons (two patients), ocular brachytherapy (four patients), and endoresection (one patient). Two patients developed metastasis. A 17-year-old male with liver metastasis died 30 months after diagnosis. A 3-year-old male with metastatic choroidal melanoma presented with metastasis 6 months after enucleation. Chemotherapy followed by nivolumab and ipilimumab led to a complete response. However, immunotherapy caused insulin-dependent diabetes mellitus. Genetic testing revealed a pathogenic constitutional TP53 variant, confirming Li-Fraumeni syndrome (LFS). At 24 months after diagnosis of metastatic disease, he remains in complete response. This report underscores the rarity and diverse presentation of pediatric choroidal melanoma. Diagnosis of LFS in one patient highlights the importance of genetic testing for tumor predisposition and personalized approaches in managing rare pediatric tumors.

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2025-06-24 | Neoantigenic properties of TP53 variants modify cancer risk in individuals with Li-Fraumeni syndrome

STRUCTURED ABSTRACT Importance Li-Fraumeni Syndrome (LFS) is an heterogenous cancer predisposition caused by pathogenic TP53 variants, characterized by a lifelong high risk of a broad spectrum of cancers. At least certain pathogenic TP53 variants have been shown be immunogenic in a somatic context. Whether neoantigenicity contributes to the heterogeneity of LFS is unknown. Objective To analyze the correlations between predicted neoantigenic properties of pathogenic TP53 missense variants and LFS patterns. Design Association study between predicted MHC-I presentation scores for TP53 hotspot variants, LFS presentation and individual HLA-I genotyping in carriers of TP53 germline pathogenic variants using data from mutation databases and clinical registries. Setting MHC-I presentation scores were generated for the set of nonameric neo-peptides surrounding each TP53 missense variant against 145 different HLA-I using NetMHCpan 4.1 and the Allele Frequency Net Database. Genotype-phenotype data were leveraged from the public TP53 database (germline dataset, n=3,446; https://tp53.isb-cgc.org/ ) and two independent LFS clinical registries (n=339). Individual correlations between HLA-I genotyping, TP53 missense variants and phenotypes were investigated in a group of 173 subjects with LFS. Participants Individuals with LFS enrolled in LFS-registries in France and Germany were included. Main outcomes and measures A predicted neoantigenic score (PNS) was calculated for each variant. Correlations with median age at first cancer, and cancer type were analyzed. Results Among 709 carriers of frequent TP53 pathogenic variants, PNS was strongly correlated with median age at first cancer (range 18-43 years, p=0.01319, R=0.69). Compared to carriers of low PNS (<1) variants, carriers of high PNS (>2) variants showed delayed median age at first diagnosis (34 [CI95%, 29-40] vs. 25 years [CI95%, 22-27]), fewer sarcomas (osteosarcoma [RR 0.29, p-adj = 0.02]; soft-tissue [RR 0.41, p-adj = 0.02]), and more cancer types typically not associated with LFS [RR 1.61, p-adj = 0.02]. Conclusion and Relevance MHC-I neoantigenic properties of TP53 variants modify cancer risk and spectrum in carriers of pathogenic TP53 variants, suggesting that individual variant-specific immune response may contribute to the heterogenous presentation of LFS.

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2024-11-25 | Long-term survival in a patient with Li-Fraumeni syndrome-associated giant cell glioblastoma treated with nivolumab: illustrative case.

Li-Fraumeni syndrome (LFS) is characterized by p53 germline mutations and a high predisposition to cancers including glioblastoma (GBM), the most common and aggressive primary malignant brain tumor in adults. Despite current therapies, the 5-year survival rate is 5%-10%. The authors report a case with a durable long-term response to immunotherapy with checkpoint inhibition in a patient with LFS-associated GBM. An 18-year-old female presented after a syncopal episode and left leg weakness and was found to have a right frontal tumor. She underwent gross-total resection of the tumor (grade IV giant cell GBM IDH-wildtype, MGMT unmethylated, associated with a p53 germline mutation), radiation, and chemotherapy. On later imaging, increased enhancement was demonstrated, which raised concerns for tumor recurrence, and she underwent stereotactic radiosurgery followed by lomustine and procarbazine. These agents were later replaced with bevacizumab after a second resection, negative for recurrent glioma. Subsequently, nivolumab was added, given concerns for tumor progression, and the patient showed improvement within 5 months. The patient has continued nivolumab monotherapy and has had progression-free survival for more than 7 years. Despite advances in treatment, the median survival of patients with GBM is only 15 months. This case highlights the potential of immunotherapy with PD-L1 checkpoint inhibition in improving outcomes for LFS-associated GBM patients. https://thejns.org/doi/10.3171/CASE24539.

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2025-06-19 | Allergic Reaction to a Bovine-Derived Dural Graft without Eosinophilic Meningitis : A Case Report and Literature Review.

Bovine-derived dural substitutes are commonly used in cranial and spinal duraplasty. Although they are generally well tolerated, allergic reactions have been reported-almost all presented with eosinophilic meningitis. A 7-year-old girl with Li-Fraumeni syndrome and diffuse pediatric glioma underwent a third salvage resection in which a bovine collagen dural onlay was placed. Ten days post operatively, she developed fever, lethargy, and a subcutaneous scalp fluid collection. Cultures and imaging were negative for infection; cerebrospinal fluid (CSF) revealed pleocytosis (elevated white blood cells and protein) without eosinophilia. High-dose dexamethasone produced transient clinical and radiographic improvement, but fever and fluid re accumulated whenever steroids were tapered. Given the steroid dependence and persistently negative infectious work-up, the graft was explanted. Pathology demonstrated a foreign-body giant cell reaction without eosinophils, and the patient's symptoms resolved permanently after removal. This report documents the first pediatric case of bovinederived dural graft hypersensitivity without eosinophilic meningitis. Clinicians should consider graft-related allergy in children who develop recurrent fluid collections and fevers after duraplasty-even when CSF eosinophils are absent and cultures remain negative and should recognize that definitive treatment may require graft removal rather than prolonged steroid therapy.

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2024-10-23 | Osteosarcoma patient with Li-Fraumeni syndrome: the first case report in Vietnam.

Li-Fraumeni syndrome (LFS) is a hereditary disorder characterized by an increased risk of developing multiple early-onset cancers, primarily due to germline TP53 mutations. Women and men with this mutation face lifetime cancer risks of 90% and 70%, respectively. This report describes the first documented case of LFS with clinical information in Vietnam involving a 9-year-old child diagnosed with osteosarcoma who had multiple first- and second-degree relatives with cancer. Whole-genome sequencing (WGS) revealed a heterozygous, pathogenic, autosomal dominant TP53 variant NM_000546.6:c.733G>A (p.Gly245Ser) and a translocation in the 3'UTR of the ATMIN gene with unknown pathogenicity in both the patient and her mother. Sanger sequencing confirmed the presence of the TP53 c.733G>A mutation, which was subsequently detected in extended family members. Of the 17 family members invited for testing, only 8, none of whom currently have cancer, agreed to participate: all tested negative for the mutation. This case highlights the importance of genetic testing for the early detection and management of cancers in LFS patients. It also underscores significant barriers to genetic screening in Vietnam, including limited access and the psychosocial consequences of testing, which emphasize the need for improved genetic counseling and surveillance strategies that are tailored to local contexts.

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2024-09-30 | Case Report: Pathological fracture in a Li-Fraumeni osteosarcoma patient: "Capasquelet'' femoral reconstruction and tumor vascular analysis with endomucin immunofluorescence multiplexing

We describe the case report of an Osteosarcoma patient, with a Li-Fraumeni Syndrome, presenting with a pathological femoral fracture. The patient was treated with a multidisciplinary approach associating neoadjuvant and adjuvant chemotherapy with excisional surgery. The femoral reconstruction consisted of a ``Capasquelet'' reconstruction combining an induced membrane and a vascularized fibula allograft allowing a good functional result with an early weight-bearing. We managed to complete our histological analysis in this patient, in order to evaluate the tumor vascularization. Indeed, using the syngeneic osteosarcoma MOS-J mouse model, we highlighted previously that CD31+/\ensuremath{\alpha}-SMA+ vessels may be indicators of vasculature normalization and therefore may be used as specific markers of a good therapeutic response. Thus, we search for its interest in this specific case as preliminary work. The aim was to assess the feasibility and technical validity of the vascularization analysis of a human osteosarcoma tumor specimen. Therefore, we propose an immunohistochemistry methodology with multiplexed immunofluorescence to assess the vascularization as a promising marker in human osteosarcoma tissue.

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2024-06-11 | 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.

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2024-06-01 | Marrow-ablative consolidation chemotherapy (HDCT) to decrease the development of choroid plexus carcinoma (CPC) specific relapse in high-risk TP53-mutated (germline or somatic) young children with newly diagnosed CPC.

2088 Background: Choroid plexus carcinomas (CPC) are highly malignant, early childhood cancers in which the loss of TP53 function is a central element of their development and defines unfavorable disease. To date, CPC-free survival rates have remained poor; recent data from St. Jude including complete TP53 mutation status, yielded CPC-free survival of only 29% with a non-marrow-ablative chemotherapy strategy. The rarity of CPC has constrained the ability to explore the role of HDCT with autologous hematopoietic progenitor cell rescue (AuHPCR). Previously reported results of the "Head Start" (HS) HDCT approach showed some promise of cure, but were limited by small patient numbers, short follow-up and incomplete TP53 mutation data. Consequently, the role of HDCT and AuHPCR in TP53-mutated CPC remains unclear. Methods: We have analyzed data on TP53 status, therapy, treatment responses, CPC-free and overall survivals (OS) and second cancers from the largest cohort of such patients, all who received initial therapy with the intent/consideration of undergoing consolidative HDCT. Results: Twenty-seven children with CPC (median age, 16 months) received HS-like induction chemotherapy regimens or ICE with the intent of utilizing consolidative HDCT. Twenty-three of 27 completed HDCT consolidation; the remaining 4 patients did not proceed with HDCT due to parental choice. Somatic or germline TP53 mutations were identified in 17 patients, while 4 patients exhibited TP53 wild type (TP53wt); TP53 status remains untested or unavailable in 6 patients. Five-year CPC-free survival and OS for the entire cohort were 47.8% and 44.4%. CPC-free survival for those with TP53 germline mutations (n=12) was 66%, for those with somatic tumor TP53 mutations (n=5) was 40% and for those with confirmed TP53wt (n=4) was 50%. The 5-year CPC-free survival for all 23 patients who underwent HDCT and AuHPCR was 52%, comprising 3/4 TP53wt patients, 10/12 TP53 germline mutated patients and all 5 TP53 somatic tumor mutated patients. Notably, all six survivors with TP53 mutations had undergone HDCT with AuHPCR, and all but one avoided irradiation. Eight out of 12 patients with documented genotypic (TP53 germline mutated) Li-Fraumeni Cancer Predisposition Syndrome (LFS) developed second malignancies. Conclusions: Our data indicate that HDCT with AuHPCR consolidation is associated with improved CPC-free survival compared with historical reports in young children with high-risk TP53 mutated CPC. However, the ultimate development of second cancers substantially affects outcomes for those with LFS, irrespective of HDCT treatment. These data justify the inclusion of HDCT and AuHPCR in the prospective international trial under development for young children with newly diagnosed TP53 mutated CPC.

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