Germline TP53 Mutations Research Articles

Correlation between choroid plexus carcinoma and Li-Fraumeni syndrome: implications of TP53 mutations and management strategies-a case-based narrative review.

Choroid plexus carcinomas (CPCs) are rare, aggressive grade 3 tumors of the central nervous system associated with Li-Fraumeni syndrome (LFS) in a notable percentage of cases due to TP53 germline mutations. Understanding the correlation between CPCs and LFS is crucial for tailored management strategies. However, distinguishing CPCs from benign choroid plexus papillomas (CPPs) remains challenging, relying largely on histologic features. This study aimed to explore the association between CPCs and LFS, emphasizing the impact of TP53 mutations on diagnosis, treatment, and clinical outcomes. Scientific databases such as PubMed, Scopus, and Web of Science were systematically searched up to January 2024 using keywords related to CPCs, LFS, TP53 mutation, and central nervous system tumors. Selection criteria included studies investigating the link between CPCs and LFS, their management approaches, and genetic implications of TP53 mutations. Ten relevant studies were selected for analysis after screening titles, abstracts, and full-text articles. Data extraction focused on clinical, genetic, and management factors related to CPCs associated with LFS. The review highlighted the strong association (36%) between CPCs and LFS, primarily due to TP53 germline mutations. Studies emphasized the need for genetic testing in patients with CPCs, especially in pediatric cases, to identify LFS implications. Furthermore, the impact of TP53 mutations on treatment strategies was emphasized, recommending irradiation-sparing therapies due to inferior survival rates associated with radiotherapy in LFS patients with CPCs. Cases illustrated the challenges in diagnosing CPCs and the importance of immunohistochemistry and genetic testing for TP53 mutations. CPCs pose challenges in diagnosis and management, particularly in distinguishing them from benign tumors. The association with LFS, often due to TP53 germline mutations, underscores the importance of genetic testing for early detection and tailored treatment strategies. Irradiation-sparing therapies are recommended for LFS-associated CPCs to mitigate the risk of secondary malignancies. Comprehensive profiling of CPC patients, especially in pediatric cases, is crucial for early detection and management of potential secondary cancers associated with LFS.

Laser interstitial thermal therapy as a radiation-sparing approach for central nervous system tumors in children with cancer predisposition syndromes: report of a child with Li-Fraumeni syndrome. Illustrative case.

Ionizing radiation and alkylating chemotherapies increase secondary malignancy risk in patients with cancer predisposition syndromes (CPSs), such as Li-Fraumeni syndrome. Laser interstitial thermal therapy (LITT) is a minimally invasive ablation technique that has not been associated with mutagenic risks. We describe the case of a child with LFS and a history of treated choroid plexus carcinoma (CPC) who developed a second primary glial tumor that was safely treated with magnetic resonance imaging (MRI)-guided LITT. A 4-year-old male with left parietal World Health Organization grade III CPC associated with a TP53 germline mutation was evaluated. The patient underwent neoadjuvant platinum-based chemotherapy before near-total resection, followed by 131I-8H9 immunotherapy and 30 fractions of 54-Gy proton radiotherapy. He remained without evidence of disease for 2 years before developing a slow-growing mass adjacent to the left frontal ventricular horn. Stereotactic biopsy revealed a glial neoplasm. Given the nonsuperficial location and focality of the lesion, MRI-guided LITT was performed for ablative therapy. There were no complications, and 2 years of surveillance revealed continued retraction of the ablated tumor focus and no subsequent disease. Alternatives to mutagenic therapies for brain tumors should be explored for patients with CPS. LITT paired with imaging surveillance is a logical strategy to ensure durable outcomes and mitigate treatment-related secondary neoplasms.

LFSPROShiny: An Interactive R/Shiny App for Prediction and Visualization of Cancer Risks in Families With Deleterious Germline TP53 Mutations.

LFSPRO is an R library that implements risk prediction models for Li-Fraumeni syndrome (LFS), a genetic disorder characterized by deleterious germline mutations in the TP53 gene. To facilitate the use of these models in clinics, we developed LFSPROShiny, an interactive R/Shiny interface of LFSPRO that allows genetic counselors (GCs) to perform risk predictions without any programming components and further visualize the risk profiles of their patients to aid the decision-making process. LFSPROShiny implements two models that have been validated on multiple LFS patient cohorts: a competing risk model that predicts cancer-specific risks for the first primary and a recurrent-event model that predicts the risk of a second primary tumor. Starting with a visualization template, we keep regular contact with GCs, who ran LFSPROShiny in their counseling sessions, to collect feedback and discuss potential improvement. On receiving the family history as input, LFSPROShiny renders the family into a pedigree and displays the risk estimates of the family members in a tabular format. The software offers interactive overlaid side-by-side bar charts for visualization of the patients' cancer risks relative to the general population. We walk through a detailed example to illustrate how GCs can run LFSPROShiny in clinics from data preparation to downstream analyses and interpretation of results with an emphasis on the utilities that LFSPROShiny provides to aid decision making. Since December 2021, we have applied LFSPROShiny to over 100 families from counseling sessions at the MD Anderson Cancer Center. Our study suggests that software tools with easy-to-use interfaces are crucial for the dissemination of risk prediction models in clinical settings, hence serving as a guideline for future development of similar models.

Pediatric Adrenocortical Carcinoma: The Nuts and Bolts of Diagnosis and Treatment and Avenues for Future Discovery.

Adrenocortical tumors (ACTs) are infrequent neoplasms in children and adolescents and are typically associated with clinical symptoms reflective of androgen overproduction. Pediatric ACTs typically occur in the context of a germline TP53 mutation, can be cured when diagnosed at an early stage, but are difficult to treat when advanced or associated with concurrent TP53 and ATRX alterations. Recent work has demonstrated DNA methylation patterns suggestive of prognostic significance. While current treatment standards rely heavily upon surgical resection, chemotherapy, and hormonal modulation, small cohort studies suggest promise for multi-tyrosine kinases targeting anti-angiogenic pathways or immunomodulatory therapies. Future work will focus on novel risk stratification algorithms and combination therapies intended to mitigate toxicity for patients with perceived low-risk disease while intensifying therapy or accelerating discoveries aimed at improving survival for patients with difficult-to-treat disease.

Low prevalence of germline TP53 and PALB2 mutations in unselected cohort of breast cancer patients from Brunei Darussalam

Background: Breast cancer is the most frequent malignancy affecting women worldwide. The majority of breast cancer occurs sporadically, with only 5-10% being caused by inheritance of susceptibility genes. In Brunei Darussalam, breast cancer is the leading cause of cancer in women. The prevalence and clinical relevance of breast cancer susceptibility genes in Brunei breast cancer patients is unknown. We investigated the prevalence and clinical relevance of germline TP53 and PALB2 genes, recognised to confer a high and moderate risk respectively, in the development of breast cancer in an unselected cohort of Brunei breast cancer patients. Methods: Genomic DNA was extracted from peripheral blood samples of 54 unselected Brunei breast cancer patients. The DNA samples were sequenced for germline BRCA1, BRCA2, TP53, and PALB2 variants using targeted panel sequencing on a Hi-Plex NGS platform. Identified variants were analysed for their pathogenicity classification based on clinical/population/mutation databases, in-silico data, and available functional data analysis. Chi-square test was used to determine the association between TP53 codon 72 and response to chemotherapy in Brunei breast cancer patients. Results: We identified two TP53 and five PALB2 missense variants in our study population. Five of the identified variants were classified as variants of uncertain significance (one in TP53 and four in PALB2) giving a prevalence of TP53 and PALB2 variant of uncertain significance carriers at 1.9% and 9.3%, respectively. No pathogenic TP53 and PALB2 mutation was identified in this study suggesting the rarity of these genes in breast cancer.TP53 codon 72 had no association with Brunei breast cancer patients’ response to chemotherapy supporting the benign characteristic of the variant P72R. Conclusions: Our current findings suggest that the contribution of germline TP53 and PALB2 genes in unselected Brunei breast cancer patients is rare, and a larger number of participants will be required to confirm this finding.

Updated Results of the Phase I BALLI-01 Trial of UCART22 Process 2 (P2), an Anti-CD22 Allogeneic CAR-T Cell Product Manufactured By Cellectis Biologics, in Patients with Relapsed or Refractory (R/R) CD22+ B-Cell Acute Lymphoblastic Leukemia (B-ALL)

Introduction: UCART22 is a genetically modified allogeneic T-cell product manufactured from healthy donor cells. Donor-derived T-cells are transduced using a lentiviral vector to express the anti-CD22 chimeric antigen receptor (CAR) and are further modified using Cellectis' TALEN ® technology to disrupt the T-cell receptor alpha constant ( TRAC) and CD52 genes to minimize risk of graft-vs-host disease (GvHD) and allow use of an anti-CD52 antibody for lymphodepletion (LD). Preliminary results from patients treated with UCART22 manufactured by a CMO (Process 1 (P1)) showed that UCART22 was well-tolerated and meaningful responses were achieved at the highest dose level (DL 3; 5 x 10 6 cells/kg). The fludarabine, cyclophosphamide, and alemtuzumab (FCA) LD regimen was also shown to extend host lymphocyte suppression and improve UCART22 expansion versus fludarabine and cyclophosphamide (FC) alone (Boissel N, et al. EHA 2023). We now report updated results from the BALLI-01 study that includes the first patients treated with UCART22 Process 2 (P2) manufactured by Cellectis Biologics. Methods: The primary endpoints are safety, tolerability, and determining the MTD/RP2D of UCART22. Additional endpoints are anti-leukemic activity and expansion of UCART22. Eligibility criteria include age 15‒70y, B-ALL blast CD22 expression ≥ 70%, and ≥ 2 prior treatment regimens. After FCA (F 30 mg/m 2 × 3d, C 0.5g/m 2 × 3d, A 20 mg/d × 3d) LD regimen, pts received a single infusion of UCART22-P2. In vitro comparability assays suggested that UCART22 P2 was more potent than UCART22 P1, so dose escalation with UCART22 P2 started at DL2 (1 x 10 6 cells/kg) compared to the highest studied dose DL3 (5 x 10 6 cells/kg) with UCART22 P1. Results: As of 01 July 2023, 3 pts were enrolled into the first UCART22 P2 cohort at DL2. Pt 1 is a 17yo female with B-ALL with a hypodiploid karyotype and a germline TP53 mutation whose disease had previously failed to respond to multiagent chemotherapy, blinatumomab (blina), inotuzumab (ino), venetoclax (ven), allogeneic hematopoietic stem cell transplantation (HSCT), and autologous CD19 CAR T-cell therapy (CAR19) x2. Pt 2 is a 68yo female with Ph-negative B-ALL who relapsed with CD19-low disease after multiagent chemotherapy, ino, and blina. Pt 3 is a 27yo male with B-ALL with an ABL2 fusion who had failed multiagent chemotherapy, ino, blina, TKIs, and an experimental autologous CAR19. UCART22 P2 administered after the FCA LD regimen was well tolerated. No DLTs or ICANS were observed. Cytokine release syndrome (CRS) occurred in 2/3 (67%) pts, with one G1 that resolved without treatment and one G2 that resolved after tocilizumab x1. There was one G5 sepsis SAE at D40 considered related to UCART22 P2 and FCA LD in Pt 1. Responses were assessed beginning on D28. Up to FC/FCA-DL3 with 18 pts treated with UCART22 P1, 1 CR, 4 CRi, and 2 morphologic leukemia-free states (MLFS) were observed, with 3 responses occurring out of 6 (50%) patients treated with FCA-DL3 (previously reported, EHA 2023). For UCART22 P2, FCA-DL2, 2/3 pts (67%) responded: Pt 2 achieved an MRD neg CR lasting over 84 days after UCART22 infusion; Pt 1 achieved an MRD negative MLFS up to D40. Pt 3 was refractory to treatment, however this pt received bridging therapy with dasatinib for his ABL2 fusion, and on Day -1, only 47% of the leukemic cells expressed CD22 (down from 88% at screening). UCART22 P2 expansion was observed by flow cytometry in peripheral blood with peak of 79 cells/μl in Pt 1 and 225 cells/μl in Pt 2, both at D11, with predominantly CD8 cells expanding. Inflammatory markers such as ferritin, IFN-γ, TNF-α and IL-6 levels increased more than 3-fold, correlating with UCART22 P2 expansion and CRS. Summary : In vitro comparability studies indicated that UCART22 P2 was more potent than UCART22 P1, and this was suggested clinically, as there was a 67% response rate at DL2 with UCART22 P2 compared to 50% at DL3 with UCART22 P1. Use of UCART22 P2 did not lead to any grade ≥3 CRS, and no DLTs or ICANS was observed. UCART22 P2 expansion was seen in the two responders, which closely correlated with CRS and changes in inflammatory markers. These data support the safety and preliminary efficacy of UCART22 P2 in this poor-risk R/R B-ALL population. The study continues to enroll pts treated with UCART22 P2 at dose level 2i (2.5 x 10 6 cells/kg), and updated data will be presented.

NCOG-38. UNDERSTANDING GLIOMA IN LI-FRAUMENI SYNDROME: HIGHLIGHTING THE VALUE OF SCREENING AND GENE SEQUENCING

Abstract Li-Fraumeni Syndrome (LFS) is a rare autosomal dominant disorder characterized by a germline mutation in the TP53 gene that confers an increased risk of developing cancers, including brain tumors. There is continued need to understand how LFS diagnosis impacts clinical management and outcomes of gliomas. We report the clinical course of two patients from our Neuro-Oncology. Patient 1 is a male who was diagnosed with a low-grade astrocytoma, IDH1 mutant at age 20 status post gross total resection. Given radiographic concern for tumor progression, he underwent re-resection 8 years later. Pathology showed gliosis with TP53-mutant cells. Next-generation sequencing (NGS) was positive a germline TP53 mutation, consistent with LFS. He is currently in surveillance 12 years after diagnosis without need for radiation or chemotherapy. Patient 2 is a female who was diagnosed with glioblastoma, IDH wildtype, MGMT promoter unmethylated at age 40. She was asymptomatic at the time of diagnosis as the tumor was found during routine screening. She underwent gross total resection, radiation with concurrent and adjuvant temozolomide. She is now 5 years from last treatment without recurrence. These cases illustrate the clinical spectrum of glioma in LFS. Both patients have had prolonged periods of survival without progression, even accounting for respective tumor type. Patient 1 was only diagnosed with LFS after radiographic concerns for progression. Using NGS to diagnosis LFS was clinically important, as previous reports have shown greater propensity for malignant transformation of low-grade glioma in LFS. Patient 2 was diagnosed with glioblastoma during screening and has had no recurrence. This highlights the value of early diagnosis and treatment of gliomas in patients with LFS, even if asymptomatic at discovery. Further research is needed to understand the clinical spectrum of glioma in LFS and to optimize the care of this unique patient population.

Mutational Landscape and In-Silico Analysis of TP53, PIK3CA, and PTEN in Patients with Breast Cancer from Khyber Pakhtunkhwa.

Herein, we report the mutational spectrum of three breast cancer candidate genes (TP53, PIK3CA, and PTEN) using WES for identifying potential biomarkers. The WES data were thoroughly analyzed using SAMtools for variant calling and identification of the mutations. Various bioinformatic tools (SIFT, PolyPhen-2, Mutation Taster, ISPRED-SEQ, SAAFEQ-SEQ, ConSurf, PROCHECK etc.) were used to determine the pathogenicity and nature of the SNVs. Selected interaction site (IS) mutations were visualized in PyMOL after building 3D structures in Swiss-Model. Ramachandran plots were generated by using the PROCHECK server. The selected IS mutations were subjected to molecular dynamic simulation (MDS) studies using Gromacs 4.5. STRING and GeneMANIA were used for the prediction of gene-gene interactions and pathways. Our results revealed that the luminal A molecular subtype of the breast cancer was most common, whereas a high percentage of was Her2 negatives. Moreover, the somatic mutations were more common as compared to the germline mutations in TP53, PIK3CA, and PTEN. 20% of the identified mutations are reported for the first time from Khyber Pakhtunkhwa. In the enrolled cohort, 23 mutations were nonsynonymous SNVs. The frequency of mutations was the highest in PIK3CA, followed by TP53 and PTEN. A total of 13 mutations were found to be highly pathogenic. Four novel mutations were identified on PIK3CA and one each on PTEN and TP53. SAAFEQ-SEQ predicted the destabilizing effect for all mutations. ISPRED-SEQ predicted 9 IS mutations (6 on TP53 and 3 on PIK3CA), whereas no IS mutation was predicted on PTEN. The TP53 IS mutations were TP53R43H, TP53Y73X, TP53K93Q, TP53K93R, TP53D149E, and TP53Q199X; whereas for PIK3CA, the IS mutations were PIK3CAL156V, PIK3CAM610K, and PIK3CAH1047R. Analysis from the ConSurf Web server revealed five SNVs with a highly conserved status (conservation score 9) across TP53 and PTEN. TP53P33R was found predominant in the grade 3 tumors, whereas PTENp.C65S was distributed on ER+, ER-, PR+, PR-, Her2+, and Her2- patients. TP53p.P33R mutation was found to be recurring in the 14/19 (73.6%) patients and, therefore, can be considered as a potential biomarker. Finally, these mutations were studied in the context of their potential association with different hormonal and social factors.

Advances in translational research of the rare cancer type adrenocortical carcinoma.

Adrenocortical carcinoma is a rare malignancy with an annual worldwide incidence of 1-2 cases per 1 million and a 5-year survival rate of <60%. Although adrenocortical carcinoma is rare, such rare cancers account for approximately onethird of patients diagnosed with cancer annually. In the past decade, there have been considerable advances in understanding the molecular basis of adrenocortical carcinoma. The genetic events associated with adrenocortical carcinoma in adults are distinct from those of paediatric cases, which are often associated with germline or somatic TP53 mutations and have a better prognosis. In adult primary adrenocortical carcinoma, the main somatic genetic alterations occur in genes that encode proteins involved in the WNT-β-catenin pathway, cell cycle and p53 apoptosis pathway, chromatin remodelling and telomere maintenance pathway, cAMP-protein kinase A (PKA) pathway or DNA transcription and RNA translation pathways. Recently, integrated molecular studies of adrenocortical carcinomas, which have characterized somatic mutationsand the methylome as well as gene and microRNA expression profiles, have led to a molecular classification of these tumours that can predict prognosis and have helped to identify new therapeutic targets. In this Review, we summarize these recent translational research advances in adrenocortical carcinoma, which it is hoped could lead to improved patient diagnosis, treatment and outcome.

Transactivation by partial function P53 family mutants is increased by the presence of G-quadruplexes at a promoter site

The effect of mutations in the P53 family of transcription factors on their biological functions, including partial or complete loss of transcriptional activity, has been confirmed several times. At present, P53 family proteins showing partial loss of activity appear to be promising potential candidates for the development of novel therapeutic strategies which could restore their transcriptional activity. In this context, it is important to employ tools to precisely monitor their activity; in relation to this, non-canonical DNA secondary structures in promoters including G-quadruplexes (G4s) were shown to influence the activity of transcription factors. Here, we used a defined yeast assay to evaluate the impact of differently modeled G4 forming sequences on a panel of partial function P53 family mutant proteins. Specifically, a 22-mer G4 prone sequence (derived from the KSHV virus) and five derivatives that progressively mutate characteristic guanine stretches were placed upstream of a minimal promoter, adjacent to a P53 response element in otherwise isogenic yeast luciferase reporter strains. The transactivation ability of cancer-associated P53 (TA-P53α: A161T, R213L, N235S, V272L, R282W, R283C, R337C, R337H, and G360V) or Ectodermal Dyplasia syndromes-related P63 mutant proteins (ΔN-P63α: G134D, G134V and inR155) were tested. Our results show that the presence of G4 forming sequences can increase the transactivation ability of partial function P53 family proteins. These observations are pointing to the importance of DNA structural characteristics for accurate classification of P53 family proteins functionality in the context of the wide variety of TP53 and TP63 germline and somatic mutations.

SAT274 Multilocus Imprinting Disorder Due To Genome-wide Paternal Uniparental Disomy Associated With Adrenocortical Tumors

Abstract Disclosure: E.M. Pinto: None. E. Lalli: None. G. Wu: None. R. Ribeiro: None. G. Zambetti: None. Pediatric adrenocortical tumor (ACT) is an uncommon malignancy frequently associated with Li-Fraumeni syndrome, a familial cancer predisposition disorder caused by germline mutations in the tumor suppressor TP53. ACT is also associated with other genetic constitutional disorders, such as Beckwith-Wiedemann syndrome (BWS) which results from the deregulation of a gene cluster on chromosome 11p15. We report here the identification of three pediatric patients with ACT and additional tumors, two of which received a clinical diagnosis of BWS. Family histories of these two probands include multiple unsuccessful pregnancies. All patients have wild-type TP53 sequence and no evidence for germline chromosome 11p15 alterations. Molecular analyses by whole genome sequencing revealed genome-wide copy neutral loss of heterozygosity (cnLOH) in all tumors. Microsatellite STR and MS-MLPA confirmed genome-wide cnLOH with the selective loss of all maternal chromosomes and duplication of paternal chromosomes in each tumor. Analysis of skin fibroblasts showed mosaic paternal uniparental disomy with partial LOH for all chromosomes, while no LOH was detected in blood DNA. The most prominent clinical feature of genome-wide cnLOH is an unbalanced monoallelic and parent-of-origin specific expression of imprinted genes known as multilocus imprinting disorder (MID). MID has been associated with maternal-effect variants that alter the maintenance of methylation at germline-derived differentially methylated regions (DMRs) in early embryogenesis. In addition, causative trans-acting factors in imprinting disorders, including the subcortical maternal complex (SCMC), have the potential to affect multiple DMRs across the genome, resulting in a multilocus imprinting disorder. Our study identifies three pediatric patients who developed ACT and other tumors that have undergone genome wide cnLOH that specifically selected against all maternal chromosomes. None of three patients presented with germline alterations in TP53 or 11p15, typical of pediatric ACT. WGS data revealed a germline mutation (p.M573T) in the histone methyltransferase NSD1 in the mother of patient #2. NSD1 mutations are reportedly associated with recurrent miscarriages, tissue overgrowth and increased cancer risk. Alterations in other epigenetic regulators, such as SETD1B (p.R226C), a component of a histone methyltransferase complex and TNRC18 (p.P454L), that enables chromatin binding activity were observed in both mother and child in each family. Further analysis of maternal-effect variants associated with abnormal pregnancies and MID will be important for understanding the mechanisms underlying genome-wide cnLOH. Our results support the molecular testing of multiple loci in atypical clinical presentations of patients with pediatric ACT. Presentation: Saturday, June 17, 2023

FRI256 The Clinical Impacts Of Bi-allelic Germline Pathogenic Variant In TP53 In Two Patients With Li-Fraumeni Syndrome

Abstract Disclosure: V. Petry: None. D. Cohn: None. R.R. Oppenheimer: None. M.D. Estevez-Diz: None. A. Latronico: None. B.B. Mendonca: None. M.Q. Almeida: None. M.C. Fragoso: None. Background: Li-Fraumeni syndrome is an autosomal dominant cancer predisposition due to a heterozygous germline TP53 mutation. This mutation is related to different types of cancer; mainly adrenocortical carcinomas (ACC), soft tissues and bone sarcomas, breast cancer, choroid plexus carcinoma and leukemias at early ages. Although little is known about the impact of this TP53 variant in the homozygous form. Methods: We described the clinical presentation and the follow-up of 2 patients with a TP53 (p.R337H) homozygous pathogenic variant inherited from their parents. Case 1: A two year old patient presented with a headache, vomiting and nuchal stiffness, and was taken to the ER where she had a CNS CT scan. The CT scan revealed a mass located at left intraventricular region She then had surgery to remove the tumor and the histological finding confirmed the diagnosis of choroid plexus carcinoma. She underwent adjuvant systemic chemotherapy Headstart III protocol. This was the first case of cancer within this family. The child was seen by a medical geneticist and a genetic test revealed a homozygous pathogenic variant (p.R337H) in TP53. Afterwards her parents were tested and both were heterozygous for the p.R337H mutation. The patient is now 4 years old and free of oncologic disease. Case 2: A 9 months old female patient presented with Cushing´s syndrome and heterosexual precocious puberty. The MRI revealed a right adrenal tumor and she underwent laparoscopic adrenalectomy. Oral hydrocortisone was initiated postoperatively as glucocorticoid replacement therapy and was gradually tapered off over 6 months. Both parents of the patient were heterozygous for the p.R337H mutation in TP53 and they reported several cases of cancer within the family. The patient inherited both mutated alleles TP53 p.R337H. She had normal puberty development and she reached the target height. The patient did not develop further neoplasms during long-term follow-up (23 years). Conclusions: We described 2 cases with a biallelic pathogenic variant in TP53 (p.R337H) who were diagnosed with cancer at early ages and who did not develop further neoplasms during the follow-up period. There is a previous case description in the literature of a patient with a homozygous p.R337H mutation in TP53 who developed ACC at an early age and he did not develop other neoplasms during 8 years of follow-up. These two cases draw your attention to the early age for the development of choroid plexus carcinoma and adrenocortical tumors as well as the published case by Giacomazzi et al. Whether the bi-allelic pattern of the TP53 variant influences the tumor’s behavior remains unclear, there are potentially broad implications for clinical surveillance and genetic counseling for patients and their families. Presentation: Friday, June 16, 2023

Clinical Features of Li-Fraumeni Syndrome in Korea.

Li-Fraumeni syndrome (LFS) is a hereditary disorder caused by germline mutation in TP53. Owing to the rarity of LFS, data on its clinical features are limited. This study aimed to evaluate the clinical characteristics and prognosis of Korean patients with LFS. Patients who underwent genetic counseling and confirmed with germline TP53 mutation in the National Cancer Center in Korea between 2011 and 2022 were retrospectively reviewed. Data on family history with pedigree, types of mutation, clinical features, and prognosis were collected. Fourteen patients with LFS were included in this study. The median age at diagnosis of the first tumor was 32 years. Missense and nonsense mutations were observed in 13 and one patients, respectively. The repeated mutations were p.Arg273His, p.Ala138Val, and pPro190Leu. The sister with breast cancer harbored the same mutation of p.Ala138Val. Seven patients had multiple primary cancers. Breast cancer was most frequently observed, and other types of tumor included sarcoma, thyroid cancer, pancreatic cancer, brain tumor, adrenocortical carcinoma, ovarian cancer, endometrial cancer, colon cancer, vaginal cancer, skin cancer, and leukemia. The median follow-up period was 51.5 months. Two and four patients showed local recurrence and distant metastasis, respectively. Two patients died of leukemia and pancreatic cancer 3 and 23 months after diagnosis, respectively. This study provides information on different characteristics of patients with LFS, including types of mutation, types of cancer, and prognostic outcomes. For more appropriate management of these patients, proper genetic screening and multidisciplinary discussion are required.

Risk-reducing salpingo-oophorectomy among Chinese women at increased risk of breast and ovarian cancer

BackgroundRisk-reducing salpingo-oophorectomy (RRSO) is recommended for women at increased risk of breast and ovarian cancer. We launched a prospective study of women receiving RRSO, including those with mutations in genes beyond BRCA1/2.Patients and methods80 women were enrolled for RRSO with sectioning and extensively examining the fimbriae (SEE-FIM) protocol between October 2016 and June 2022. The majority of participants had inherited susceptibility gene mutations or a family history suggesting ovarian cancer risk, while patients with isolated metastatic high-grade serous cancer of unknown origin were also included.ResultsOverall, two patients had isolated metastatic high-grade serous cancer with unknown origin, and four patients had family histories but refused to take genetic tests. The rest 74 patients harbored deleterious susceptible gene, including 43 (58.1%) with BRCA1 mutation, and 26 (35.1%) with BRCA2 mutation, respectively. Other mutated genes included ATM (1), BRIP1(1), PALB2(1), MLH1(1) and TP53 (1) in each patient. Among the 74 mutation carriers, three (4.1%) cancers were recognized, one (1.4%) was found to have serous tubal intraepithelial carcinoma (STIC), and five patients (6.8%) was diagnosed with serous tubal intraepithelial lesions (STILs). P53 signature was recognized in 24 patients (32.4%). For other genes, MLH1 mutation carrier had endometrial atypical hyperplasia and p53 signature in fallopian tubes. The germline TP53 mutation carrier had STIC in the surgical specimens. Evidence for precursor escape was also recognized in our cohort.ConclusionOur study demonstrated clinic-pathological findings of patients at increased risk of breast and ovarian cancer, and expand the clinical application of SEE-FIM protocol.

Emerging insights into ethnic-specific TP53 germline variants.

The recent expansion of human genomics repositories has facilitated the discovery of novel TP53 variants in populations of different ethnic origins. Interpreting TP53 variants is a major clinical challenge because they are functionally diverse, confer highly variable predisposition to cancer (including elusive low-penetrance alleles), and interact with genetic modifiers that alter tumor susceptibility. Here, we discuss how a cancer risk continuum may relate to germline TP53 mutations on the basis of our current review of genotype-phenotype studies and an integrative analysis combining functional and sequencing datasets. Our study reveals that each ancestry contains a distinct TP53 variant landscape defined by enriched ethnic-specific alleles. In particular, the discovery and characterization of suspected low-penetrance ethnic-specific variants with unique functional consequences, including P47S (African), G334R (Ashkenazi Jewish), and rs78378222 (Icelandic), may provide new insights in terms of managing cancer risk and the efficacy of therapy. Additionally, our analysis highlights infrequent variants linked to milder cancer phenotypes in various published reports that may be underdiagnosed and require further investigation, including D49H in East Asians and R181H in Europeans. Overall, the sequencing and projected functions of TP53 variants arising within ethnic populations and their interplay with modifiers, as well as the emergence of CRISPR screens and AI tools, are now rapidly improving our understanding of the cancer susceptibility spectrum, leading toward more accurate and personalized cancer risk assessments.

RARE-06. DISSECTING CELLULAR DIFFERENTIATION HETEROGENEITY IN CHOROID PLEXUS CARCINOMA PATHOGENESIS

Abstract Choroid plexus (CP) neoplasms are rare, predominantly pediatric, brain tumors ranging from benign CP papilloma to aggressive CP carcinoma (CPC) associated with poor survival. Survivors often experience devastating side effects from current treatment strategies. There is an urgent need for safer, more effective therapies for CPC. A subset of human CPC exhibits abnormal NOTCH activity, whereas mutations of tumor suppressor gene TP53 are detected in &amp;gt;50% of CPC and are associated with increased genetic tumor instability and worse prognosis. CPC is one hallmark of Li-Fraumeni syndrome (LFS), a rare genetic disorder associated with germline TP53 mutations. Human CP tumors also frequently display aberrant expression of transcriptional regulators of roof plate/CP differentiation, including LIM homeodomain transcription factors LMX1A, and SRY-Box Transcription Factor 2 (SOX2). To investigate the role of transcriptional regulation in CP tumorigenesis, animal models were developed driven by molecular defects commonly found in CP tumors in humans. Accordingly, sustained NOTCH and Sonic Hedgehog (SHH) activation or combined deletion of Rb1 and Trp53 tumor suppressors led to malignant CP tumors with characteristics of CPC in humans. NOTCH-driven CP tumors arose from monociliated roof plate progenitors and exhibited increased levels of Lmx1a, Lmx1b, and Sox2. In contrast, their expression was significantly reduced, while OTX2 levels were markedly increased in Rb1/Trp53-deficient CPC. Consistently, single-cell transcriptomics data show a proliferative Otx2+ tumor bulk and a small Lmx1a+/Sox2+ population in Rb1/Trp53-deficient CPC. Importantly, deletion of Sox2 in Lmx1a+ progenitors blocked NOTCH-driven CP tumor and reduced Lmx1a/b expression. Thus, LMX1A and SOX2 expression marks tumor-initiating cells, while OTX2 labels differentiated tumor cells in CPC. Together, our studies revealed intra- and inter-tumoral heterogeneity in CPC driven by distinct oncogenic signals. Knowledge of the molecular and cellular basis of heterogeneity in CP tumor development may facilitate the development of innovative diagnostic and therapeutic strategies in CPC.

First report of ELUCIDATOR study: A prospective observational multicenter study on resistance mechanisms in patients with early disease progression during osimertinib.

3032 Background: Osimertinib (Osi) is the key standard therapy for patients (pts) with chemo-naive advanced non-small cell lung cancer (NSCLC) harboring sensitizing epidermal growth factor receptor ( EGFR) mutations. However, many of cases treated with Osi experience the disease progression (PD). Therefore, understanding first-line osimertinib resistance mechanisms is essential for future therapeutic strategies. Here, we addressed the underlying mechanisms of resistance to Osi using paired plasma DNA samples and particularly focused on early PD (PD within 6 months) cases. Methods: This trial is the multicenter prospective research, and we prospectively collected plasma DNA samples prior Osi treatment and at PD. Next-generation sequencing (NGS) implemented with the molecular barcoding method was performed to analyze gene mutations in 197 cancer-associated genes. Then using these ct-DNA, we analyzed the Osi resistance by ultra-sensitive NGS. In this interim analysis, we specially analyze the early PD (PD within 6 months) cases. Results: One hundred eighty-eight pts were enrolled between May 2019 and January 2021. Among these pts, 125 (66%) pts were female, 96 (51%) were EGFR exon 19 deletion mutation, and 109 (58%) were never smoker. Seventy-eight pts experienced PD and 36 pts experienced early PD at interim analysis. Baseline shedders, patients with plasma positivity for EGFR-activating mutation were more frequently observed in early PD pts than non-PD (86.1% vs 63.4%, p = 0.009). Early PD patients had significantly more co-occurring gene mutations along with EGFR mutations than non-early PD patients (2.89±1.49 vs 1.97±1.37, p = 0.002). Most notably, 3 among 36 early PD pts and 8 among 78 PD pts had significant reduction of plasma EGFR mutant allele frequency at PD than that at baseline. Among those, 1 had germline BRCA1 mutation and 1 had BRINP3 mutation in 3 early PD pts, and 1 had germline BRCA2 mutation, and 1 had germline TP53 mutation in 5 PD pts excluding early PD pts. Co-occurring TP53 mutations were not relevant to early PD in this study cohort. Conclusions: Germline mutations in BRCA1/2, TP53 and BRINP3 may confer early and unprecedented resistance to Osi monotherapy. Plasma-based serial comprehensive gene profiling may help predict and identify patients unlikely to benefit from Osi treatment, though further study is warranted. Clinical trial information: jRCTs031180051 .

Lessons learnt from the clinico-genomic profiling of families with Li Fraumeni syndrome at a tertiary care centre in North India.

Li Fraumeni syndrome (LFS) is an inherited cancer predisposition syndrome due to TP53 gene mutation. There is sparse literature on LFS in the Indian population. We conducted a retrospective study of patients diagnosed with LFS and their family members, registered at our Medical Oncology Department between September 2015 and 2022. 9 LFS families consisted of 29 patients diagnosed currently or historically with malignancies including 9 index cases and 20 first or second-degree relatives. Of these 29 patients, 7 (24.1%) patients developed their first malignancy before the age of 18 years, 15 (51.7%) were diagnosed between 18and and 60 years, and 7 (24.1%) were diagnosed at age more than 60 years. A total of 31 cancers occurred among the families, including 2 index cases who had metachronous malignancies. Each family had a median of three cancers (range 2-5); sarcoma (n = 12, 38.7% of total cancers) and breast cancer (n = 6, 19.3% of total cancers) being the commonest malignancies. Germline TP53 mutations were documented among 11 patients with cancers and 6 asymptomatic carriers. Of these nine mutations, the most common types were missense (n = 6, 66.6%) and nonsense (n = 2, 22.2%), and the commonest aberration was replacement of arginine with histidine (n = 4, 44.4%). Eight (88.8%) families met either classical or Chompret's diagnostic criteria and two (22.2%) satisfied both. Two (22.2%) families fit the diagnostic criteria prior to onset of malignancy in the index cases but were untested till the index cases presented to us. Four mutation carriers from three families are undergoing screening as per the Toronto protocol. No new malignancies have been detected so far during the mean surveillance duration of 14 months. The diagnosis of LFS has socio-economic implications for patients and their families. Delay in genetic testing misses out a crucial window wherein asymptomatic carriers could initiate surveillance in a timely fashion. Greater awareness on LFS and genetic testing in Indian patients is warranted for better management of this hereditary condition.

171MO Inflammatory profiling of individuals with germline TP53 mutations (gTP53m) and its relationship to subsequent cancer development

Individuals with gTP53m have nearly 24 times higher incidence of any cancer than the general population, of which breast cancer (BC) comes first. Beside prophylactic mastectomy, no preventative measures are currently available. Nothing or very little is known regarding the role of immune and inflammatory factors. We aimed to search for predictors of the development of new subsequent cancers (NSC) among inflammatory and immune cytokines, in patients (pts) with gTP53m from the prospective LIFSCREEN MRI screening trial (NCT01464086). All pts with gTP53m who entered the LIFSCREEN trial at Gustave Roussy 11/2011 - 12/2014, with frozen serum samples available were eligible. We analysed inflammatory cytokines and chemokines on samples collected sequentially at accrual month (M) 0 and at M12 using multiplex immunoassay of serum analytes (Bio-Plex Pro™ 40-plex, Bio-Rad). Primary objective was potential associations between M0 and M12 biomarkers and the incidence of any NSC. We used Wilcoxon-Mann Whitney tests and logistic regressions. Among 107 pts, 42 had serum stored and were eligible. Median age 35.5 (7-67), 67% females. Median follow-up 100 months (95% CI 83-117). 24 pts (57%) had already had cancer before entering the study, of which 7 BC. 11 NSC were diagnosed. At M0, a Th1-like profile (high serum IL-2 (>2 pg/ml) (p=0.03; overall) and CXCL9 levels (>50 pg/ml) (p=0.01; without history of cancers)) was associated with the incidence of NSC. In logistic regression, the Th1 CXCL9 and CXCL10 chemokines were associated with a higher probability of NSC (p=0.03 and 0.04, respectively). At M12, high levels of the follicular T helper cell CXCL13 (>25 pg/ml) chemokine were protective against NSC (p=0.04). Individuals with a significant drop between M0 and M12 of neutrophil and T cell-chemoattracting factors (such as CXCL1 and IFNg/CXCL16 respectively) did not develop cancer. This exploratory study identifies a disbalance between Th1 and TFH soluble markers in Li Fraumeni deemed to experience additional neoplasia among pts carrying gTP53m. These findings warrant further validation and could be actionable for cancer interception.

163P Long-term assessment of secondary malignancies (2ndM) in women with breast cancer (BC) and germline TP53 mutations (gTP53m) treated with radiation therapy (RT)

163P Long-term assessment of secondary malignancies (2ndM) in women with breast cancer (BC) and germline TP53 mutations (gTP53m) treated with radiation therapy (RT)