Evaluation of TP53 Pro72Arg and MDM2 SNP285–SNP309 polymorphisms in an Italian cohort of LFS suggestive patients lacking identifiable TP53 germline mutations

Whole exome sequencing identified a novel POT1 variant as a candidate pathogenic allele underlying a Li-Fraumeni-like family

BACKGROUND

Li-Fraumeni syndrome (LFS) and Li-Fraumeni-like (LFL) syndrome are rare hereditary diseases characterized by predisposition to a diverse spectrum of cancer types, primarily sarcoma. The pathogenic variants underlying the majority of LFL cases remain to be explored.

METHODS

We performed whole-exome sequencing (WES) on 13 core members of a large LFL family with highly aggregated incidences of cancers, including cases with sarcoma, non-small cell lung cancer and cardiac angiosarcoma, and conducted a comprehensive literature review of candidate gene associations in LFS/LFL syndromes or sarcoma to identify potential pathogenic germline variants.

RESULTS

No germline variants in the best-known LFL/LFS-associated gene TP53 were detected. Of all the genes associated with LFS/LFL or sarcoma that we have surveyed, we identified a novel p.P35L germline variant in POT1 (protection of telomeres 1). Germline and somatic alterations in POT1 have been implicated in a series of familial cancers, including angiosarcoma, glioma, melanoma and colorectal cancer. This particular variant is located in the telomere-binding OB1 domain, which is important in maintaining the proper telomere length, and showed high conservation across different POT1 orthologues. No record of the variant was found in any of the 1000 genomes, ExAC, gnomAD, dpSNP and COSMIC databases. Prediction algorithms and in silico structural analysis suggested completely disrupted protein structure and function of POT1 in the presence of this mutation.

CONCLUSIONS

Leveraging WES, we identified a novel germline risk allele, p.P35L in POT1, that likely predisposes to LFL syndrome. Our results support the routine testing of POT1 and other LFL/LFS-associated genes in the risk populations to enable early cancer diagnosis, prevention and intervention.

Cumulative risk of skin cancer in patients with Li-Fraumeni syndrome

Li-Fraumeni syndrome (LFS) is an inherited cancer syndrome, characterized by an early onset of various types of cancers. LFS is associated with a germline mutation in the TP53 gene. The risk of developing skin cancer in patients with LFS is unknown. To evaluate the cumulative risk of skin cancer in patients with LFS and to compare this risk to the general Dutch population. In this retrospective cohort study, all proven TP53 mutation carriers in the Netherlands Cancer Institute were included from their first visit to the Institute until June 2017. Medical charts and pathology reviews cross-referenced with PALGA, the nationwide network and registry of histo- and cytopathology were used to identify incident skin cancers. Cumulative risks were calculated by Kaplan-Meier analysis. Seventy-one patients (59% female) from 33 families were included. Ten patients (14%) developed a total of 19 skin cancers at a median age of 41 (25-65) years. The cumulative risk of skin cancer is 10.4% (95% CI 4.4-23.5%) at age 40, 25.2% (95% CI 12.3-47.6%) at age 60, and a at age 70 this risk is 44.6% (95% CI 22.9-73.9%). The cumulative risks of melanoma and basal cell carcinoma at age 70 are increased compared to the general Dutch population, namely 12.6% (95% CI 3.6-38.4%) and 34.6% (95% CI 15.4-66.2%), respectively. Patients with LFS have an increased risk of developing skin cancer. A dermatological consultation may be considered at least once in individuals with LFS to raise awareness for skin cancer and inform about risk factors.

Review: Ewing Sarcoma Predisposition

Ewing sarcoma is a rare tumor developed in bone and soft tissues of children and teenagers. This entity is biologically led by a chromosomal translocation, typically including EWS and FLI1 genes. Little is known about Ewing sarcoma predisposition, although the role of environmental factors, ethnicity and certain polymorphisms on Ewing sarcoma susceptibility has been studied during the last few years. Its prevalence among cancer predisposition syndromes has also been thoroughly examined. This review summarizes the available evidence on predisposing factors involved in Ewing sarcoma susceptibility. On the basis of these data, an integrated approach of the most influential factors on Ewing sarcoma predisposition is proposed.

Tumor Syndromes That Include Bone Tumors: An Update

Tumor syndromes, including bone neoplasias, are genetic predisposing conditions characterized by the development of a pattern of malignancies within a family at an early age of onset. Occurrence of bilateral, multifocal, or metachronous neoplasias and specific histopathologic findings suggest a genetic predisposition syndrome. Additional clinical features not related to the neoplasia can be a hallmark of specific genetic syndromes. Mostly, those diseases have an autosomal dominant pattern of inheritance with variable percentage of penetrance. Some syndromic disorders with an increased tumor risk may show an autosomal recessive transmission or are related to somatic mosaicism. Many genetic tumor syndromes are known. This update is specifically focused on syndromes predisposing to osteosarcoma and chondrosarcoma.