Classification of PTEN germline non-truncating variants: a new approach to interpretation.

BACKGROUND: PTEN hamartoma tumour syndrome (PHTS) encompasses distinct syndromes, including Cowden syndrome resulting from PTEN pathogenic variants. Missense variants account for 30% of PHTS cases, but their classification remains challenging. To address these difficulties, guidelines were published by the Clinical Genome Resource PTEN Variant Curation Expert Panel. METHODS: Between 2010 and 2020, the Bergonie Institute reference laboratory identified 76 different non-truncating PTEN variants in 166 patients, 17 of which have not previously been reported. Variants were initially classified following the current guidelines. Subsequently, a new classification method was developed based on four main criteria: functional exploration, phenotypic features and familial segregation, in silico modelling, and allelic frequency. RESULTS: This new method of classification is more discriminative and reclassifies 25 variants, including 8 variants of unknown significance. CONCLUSION: This report proposes a revision of the current PTEN variant classification criteria which at present rely on functional tests evaluating only the phosphatase activity of PTEN and apply a particularly stringent clinical PHTS score.The classification of non-truncating variants of PTEN is facilitated by taking into consideration protein stability for variants with intact phosphatase activity, clinical and segregation criteria adapted to the phenotypic variability of PHTS and by specifying the allelic frequency of variants in the general population. This novel method of classification remains to be validated in a prospective cohort.

Fine mapping of RNA isoform diversity using an innovative targeted long-read RNA sequencing protocol with novel dedicated bioinformatics pipeline.

BACKGROUND: Solving the structure of mRNA transcripts is a major challenge for both research and molecular diagnostic purposes. Current approaches based on short-read RNA sequencing and RT-PCR techniques cannot fully explore the complexity of transcript structure. The emergence of third-generation long-read sequencing addresses this problem by solving this sequence directly. However, genes with low expression levels are difficult to study with the whole transcriptome sequencing approach. To fix this technical limitation, we propose a novel method to capture transcripts of a gene panel using a targeted enrichment approach suitable for Pacific Biosciences and Oxford Nanopore Technologies platforms. RESULTS: We designed a set of probes to capture transcripts of a panel of genes involved in hereditary breast and ovarian cancer syndrome. We present SOSTAR (iSofOrmS annoTAtoR), a versatile pipeline to assemble, quantify and annotate isoforms from long read sequencing using a new tool specially designed for this application. The significant enrichment of transcripts by our capture protocol, together with the SOSTAR annotation, allowed the identification of 1,231 unique transcripts within the gene panel from the eight patients sequenced. The structure of these transcripts was annotated with a resolution of one base relative to a reference transcript. All major alternative splicing events of the BRCA1 and BRCA2 genes described in the literature were found. Complex splicing events such as pseudoexons were correctly annotated. SOSTAR enabled the identification of abnormal transcripts in the positive controls. In addition, a case of unexplained inheritance in a family with a history of breast and ovarian cancer was solved by identifying an SVA retrotransposon in intron 13 of the BRCA1 gene. CONCLUSIONS: We have validated a new protocol for the enrichment of transcripts of interest using probes adapted to the ONT and PacBio platforms. This protocol allows a complete description of the alternative structures of transcripts, the estimation of their expression and the identification of aberrant transcripts in a single experiment. This proof-of-concept opens new possibilities for RNA structure exploration in both research and molecular diagnostics.

Factors Influencing Adherence to the Risk Management Program for Women With a Genetic Predisposition to Breast Cancer: Real-World Data from a French Multicenter Program.

BACKGROUND: Risk management programs targeting women with genetic predispositions to breast cancer (BC), eg, BRCA1 and BRCA2, are effective assuming full adherence with the program protocol. However, high risk to BC in women and equal access to care may not result in high and uniform adherence with the program. OBJECTIVE: To elucidate factors influencing adherence with screening program in women with genetic predispositions to BC. MATERIAL AND METHODS: We retrieved data from a multicenter pathogenic-related BC surveillance program across 4 French regions. We used multilevel logistic modeling to analyze factors of adherence with the program, with "on-time" or postponed screening as the dependent variable. RESULTS: Seven hundred and seventy-eight participants were followed for a 4.7-year median. We observed 2796 annual screening rounds and 5.4% postponed rounds with a 6-month margin. Women with prevalent BC and carriers of BRCA1 and BRCA2 mutations did not have on-time annual screenings any more than women low cancer risk. Better adherence was observed with screenings after the 2nd round, with higher total number of rounds. Having one or more recalls was significantly associated with worse adherence. No contextual factors affected adherence. Furthermore, postponed rounds increased between 2018 and 2020 compared to 2015 and 2017. CONCLUSION: Having a higher BC risk status does not result in better adherence to the risk management program. However, factors directly related to screening rounds reduced postponements. Future research should address the benefits of screening-related organizational factors that contribute to adherence improvement.

Clinical factors associated with prolonged response and survival under olaparib as maintenance therapy in BRCA mutated ovarian cancers.

OBJECTIVE: To investigate clinical factors associated with prolonged progression-free survival (PFS) and overall survival (OS) in relapsing epithelial ovarian cancer (EOC) patients with BRCA mutations and receiving olaparib as maintenance therapy in daily practice. METHODS: Multicenter (8 hospitals) European retrospective study of relapsing EOC patients having germline or somatic mutations of BRCA1/BRCA2 genes and treated with olaparib as maintenance therapy after platinum-based chemotherapy. RESULTS: One hundred and fifteen patients were included. Median age was 54 years. There were 90 BRCA1 carriers, 24 BRCA2 carriers and one patient had germline mutation of BRCA1 and BRCA2. Six patients had somatic mutations (all BRCA1) and 109 had germline mutations. Ninety percent had serous carcinomas and were platinum-sensitive. Following ultimate platinum-based chemotherapy, 69% of the patients had normalization of CA-125 levels and 87% had RECIST objective responses, either partial (53%) or complete (34%). After a median follow-up of 21 months, median PFS was 12.7 months and median OS was 35.4 months. In multivariate analysis, factors associated with prolonged PFS under olaparib were: platinum-free interval (PFI) ≥ 12 months, RECIST complete response (CR) or partial response (PR) and normalization of CA-125 upon ultimate platinum-based chemotherapy. Factors associated with prolonged OS were PFI ≥ 12 months, CR and normalization of CA-125. CONCLUSIONS: Platinum-free interval ≥ 12 months, complete response and normalized CA-125 levels after ultimate platinum-based chemotherapy are associated with prolonged PFS and OS in relapsing BRCA1/BRCA2 mutated ovarian cancer patients who received olaparib as maintenance therapy.

TUMOSPEC: A Nation-Wide Study of Hereditary Breast and Ovarian Cancer Families with a Predicted Pathogenic Variant Identified through Multigene Panel Testing.

Assessment of age-dependent cancer risk for carriers of a predicted pathogenic variant (PPV) is often hampered by biases in data collection, with a frequent under-representation of cancer-free PPV carriers. TUMOSPEC was designed to estimate the cumulative risk of cancer for carriers of a PPV in a gene that is usually tested in a hereditary breast and ovarian cancer context. Index cases are enrolled consecutively among patients who undergo genetic testing as part of their care plan in France. First- and second-degree relatives and cousins of PPV carriers are invited to participate whether they are affected by cancer or not, and genotyped for the familial PPV. Clinical, family and epidemiological data are collected, and all data including sequencing data are centralized at the coordinating centre. The three-year feasibility study included 4431 prospective index cases, with 19.1% of them carrying a PPV. When invited by the coordinating centre, 65.3% of the relatives of index cases (5.7 relatives per family, on average) accepted the invitation to participate. The study logistics were well adapted to clinical and laboratory constraints, and collaboration between partners (clinicians, biologists, coordinating centre and participants) was smooth. Hence, TUMOSPEC is being pursued, with the aim of optimizing clinical management guidelines specific to each gene.

Insertion of Alu elements at a PTEN hotspot in Cowden syndrome.

Cowden syndrome (CS) is an inherited autosomal dominant disorder associated with germline pathogenic variants of the PTEN tumor suppressor gene. Its phenotypical expression is highly variable and the existence of patients with a CS suggestive phenotype without pathogenic PTEN variant may be related to genetic heterogeneity. In order to explore this hypothesis through the detection of potentially deleterious variants enabling us to identify a new candidate gene, we performed whole-exome sequencing (WES) in a series of 22 CS patients without detectable PTEN pathogenic variant using conventional methods for mutation screening. We failed to identify a novel candidate gene, but interestingly in two patients WES revealed the presence of two distinct, previously undescribed Alu insertions with the same break points in exon 5. These insertions were not found in a series of 35 breast carcinomas that showed a loss of PTEN expression without a detectable alteration of this gene. This study reveals the presence of a PTEN Alu insertion hotspot involved in CS, and suggests that undetected PTEN pathogenic variants could contribute to CS.