Clinical consequences of BRCA2 hypomorphism

Strategies for early detection and detailed characterization of oral lesions and head and neck squamous cell carcinoma in Fanconi anemia patients

Fanconi Anemia (FA) is an inherited disorder associated with profound DNA repair defects, marked by failure to thrive, congenital malformations, progressive bone marrow failure (BMF), and an increased susceptibility to cancer. Clinical manifestations of FA vary widely, with BMF and clonal evolution predominantly affecting younger individuals, while adults are more frequently presenting with solid tumors. Individuals with FA are at a 500-fold increased risk of developing head and neck squamous cell carcinoma (HNSCC), which tends to appear at a median age of 30 years, often at advanced stages with only a 57 % two-year survival rate. The DNA repair deficiency prohibits the use of cisplatin and radiation therapy, limiting the treatment options for FA patients. Given the critical importance of early HNSCC detection in FA patients, innovative and less invasive diagnostic techniques are needed. This review discusses the role of brush biopsy-based cytology combined with molecular and morphometric analyses, as well as next-generation sequencing. Cytology alone demonstrated significant potential for detecting high-grade oral epithelial dysplasia and early-stage HNSCC, achieving sensitivities and specificities of 97.7 % and 84.5 %, respectively. Such techniques allow for stringent surveillance of the oral cavity in FA patients, essential given the aggressive nature of HNSCC in FA and the limited treatment options. In the absence of oral mucosal lesions, a six-month follow-up is recommended. For oral lesions persisting beyond three weeks, diagnostic evaluation is warranted, with clinical follow-up every three months for low-grade dysplasia and treatment of high-grade dysplasia. Integrating modern diagnostic tools within a comprehensive screening framework, alongside patient participation, is essential for personalized care, improved surveillance, and developing preventive measures to enhance FA patient care.

Understanding the genetic epidemiology of hereditary breast cancer in India using whole genome data from 1029 healthy individuals

Breast cancer is the most highly reported cancer in India. Genetic testing could help tackle the increasing cancer burden by enabling carriers obtain early diagnosis through increased surveillance, and help guide treatment. However, accurate interpretation of variant pathogenicity must be established in a population-specific manner to ensure effective use of genetic testing. Here we query IndiGen data obtained from sequencing 1029 Indian individuals, and perform variant classification of all reported BRCA variants using gold-standard ACMG & AMP guidelines to establish disease epidemiology. To address the high number of VUS variants thus obtained, we further utilize the brca-NOVUS ML tool to obtain pathogenicity predictions in a manner close to ACMG guidelines at scale. Through the manual application of ACMG & AMP guidelines, we determined the genetic prevalence to be the following: 1 in 342 carriers of BRCA1, and 1 in 256 carriers of BRCA2 pathogenic/likely pathogenic variants bear a significant lifetime risk of developing breast / ovarian cancer in India. The high population prevalence and unique variant landscape emphasizes a need for population-scale studies of causative variants to enable effective screening. We advise cautious clinical interpretation, given incomplete penetrance and other complex factors that result in cancer disease. To the best of our knowledge, this is the first and most comprehensive population-scale genetic epidemiological study of BRCA-linked breast cancer variants reported from India.

The other side of the coin: protein deubiquitination by Ubiquitin-Specific Protease 1 in cancer progression and therapy

Reversible protein ubiquitination is a crucial factor in cellular homeostasis, with Ubiquitin-Specific Protease 1 (USP1) serving as a key deubiquitinase involved in DNA damage response (DDR) and repair mechanisms in cancer. While ubiquitin ligases have been extensively studied, research on the reverse process of ubiquitination, particularly the mechanisms involving USP1, remains relatively limited. USP1 is overexpressed in various cancers, influencing tumor initiation and progression by regulating multiple associated proteins. Inhibiting USP1 effectively suppresses tumor proliferation and migration and may help overcome resistance to cisplatin and PARP inhibitors. As a potential synthetic lethal target, USP1 demonstrates significant research potential. This review highlights the biological mechanisms of USP1 in cancer progression, the signaling pathways it regulates, and the latest advancements in USP1 inhibitors, while also analyzing the opportunities and challenges of targeting USP1. By adopting the perspective of "the other side of the coin," this review aims to underscore the crucial yet often overlooked role of the deubiquitinase USP1, contrasting it with the extensively studied ubiquitin ligases, and emphasizing its therapeutic potential in cancer treatment.

Prognostic significance of mutation type and chromosome fragility in Fanconi anemia

Fanconi anemia (FA) is a rare genetic disease characterized by high phenotypic and genotypic heterogeneity, and extreme chromosome fragility. To better understand the natural history of FA, identify genetic risk and prognostic factors, and develop novel therapeutic strategies, the Spanish Registry of Patients with FA collects data on clinical features, chromosome fragility, genetic subtypes, and DNA sequencing with informed consent of participating individuals. In this article, we describe the clinical evolution of 227 patients followed up for up to 30 years, for whom our data indicate a cumulative cancer incidence of 86% by age 50. We found that patients with lower chromosome fragility had a milder malformation spectrum and better outcomes in terms of later-onset hematologic impairment, less severe bone marrow failure, and lower cancer risk. We also found that outcomes were better for patients with mutations leading to mutant FANCA protein expression (genetic hypomorphism) than for patients lacking this protein. Likewise, prognosis was consistently better for patients with biallelic mutations in FANCD2 (mainly hypomorphic mutations) than for patients with biallelic mutations in FANCA and FANCG, with the lack of the mutant protein in patients with biallelic mutations in FANCG contributing to their poorer outcomes. Our results regarding the clinical impact of chromosome fragility and genetic hypomorphism suggest that mutant FA proteins retain residual activity. This finding should encourage the development of novel therapeutic strategies aimed at partially or fully enhancing mutant FA function, thereby preventing or delaying bone marrow failure and cancer in patients with FA. Clinical Trial Registration number: NCT06490510.

Finding significance: New perspectives in variant classification of the RAD51 regulators, BRCA2 and beyond

For many individuals harboring a variant of uncertain functional significance (VUS) in a homologous recombination (HR) gene, their risk of developing breast and ovarian cancer is unknown. Integral to the process of HR are BRCA1 and regulators of the central HR protein, RAD51, including BRCA2, PALB2, RAD51C and RAD51D. Due to advancements in sequencing technology and the continued expansion of cancer screening panels, the number of VUS identified in these genes has risen significantly. Standard practices for variant classification utilize different types of predictive, population, phenotypic, allelic and functional evidence. While variant analysis is improving, there remains a struggle to keep up with demand. Understanding the effects of an HR variant can aid in preventative care and is critical for developing an effective cancer treatment plan. In this review, we discuss current perspectives in the classification of variants in the breast and ovarian cancer genes BRCA1, BRCA2, PALB2, RAD51C and RAD51D.

BRCA2 Haploinsufficiency in Telomere Maintenance

Our previous studies showed an association between monoallelic BRCA2 germline mutations and dysfunctional telomeres in epithelial mammary cell lines and increased risk of breast cancer diagnosis for women with BRCA2 999del5 germline mutation and short telomeres in blood cells. In the current study, we analyzed telomere dysfunction in lymphoid cell lines from five BRCA2 999del5 mutation carriers and three Fanconi Anemia D1 patients by fluorescence in situ hybridization (FISH). Metaphase chromosomes were harvested from ten lymphoid cell lines of different BRCA2 genotype origin and analyzed for telomere loss (TL), multitelomeric signals (MTS), interstitial telomere signals (ITS) and extra chromosomal telomere signals (ECTS). TL, ITS and ECTS were separately found to be significantly increased gradually between the BRCA2^+/+, BRCA2^+/- and BRCA2^-/- lymphoid cell lines. MTS were found to be significantly increased between the BRCA2^+/+ and the BRCA2^+/- heterozygous (p < 0.0001) and the BRCA2^-/- lymphoid cell lines (p < 0.0001) but not between the BRCA2 mutated genotypes. Dysfunctional telomeres were found to be significantly increased in a stepwise manner between the BRCA2 genotypes indicating an effect of BRCA2 haploinsufficiency on telomere maintenance.