Early-onset diagnosis is an eligibility criterion for
BRCA1
and
BRCA2
(
BRCA
) testing in sporadic breast cancer patients. Limited family structure has been proposed as a predictor of
BRCA
mutation ...status in this group of patients. An overwhelming amount of data supports a strong association between
BRCA1
mutations and triple-negative breast cancer (TNBC). Here, we analyze the feasibility of using limited family structure and TNBC as predictors of BRCA mutation status in early-onset breast cancer patients attending genetic counseling units. We have conducted the study in a cohort of sporadic early-onset (≤35 years) breast cancer patients (
N
= 341) previously selected for
BRCA
genetic testing in Academic Hereditary Cancer Clinics from Spain. A retrospective review of medical records available at the time of risk assessment allowed us classifying patients according to family structure and TNBC. In addition, BRCAPRO score was calculated for all patients. Association between categorical variables was investigated using the Fisher’s exact test. Binary Logistic Regression Analysis was used for multivariate analysis. Limited family structure (OR 3.61,
p
= 0.013) and TNBC (OR 3.14,
p
= 0.013) were independent predictors of
BRCA
mutation status. Mutation prevalence in the subgroup of patients with at least one positive predictor was 14 %, whereas it dropped to 3 % in non-TNBCs with adequate family history (OR 5.31, 95 % CI 1.38–23.89,
p
= 0.006). BRCAPRO correctly discerned between limited and adequate family structures. Limited family structure and TNBC are feasible predictors of
BRCA
mutation status in sporadic early-onset (≤35 years) breast cancer patients attending genetic counseling units. The low prevalence of mutations observed in non-TNBCs with adequate family structure suggests that this subgroup of patients might be excluded from genetic testing.
RAD51C and RAD51D are involved in DNA repair by homologous recombination. Germline pathogenic variants (PVs) in these genes are associated with an increased risk of ovarian and breast cancer. ...Understanding the homologous recombination deficiency (HRD) status of tumors from patients with germline PVs in RAD51C/D could guide therapeutic decision-making and improve survival.
To characterize the clinical and tumor characteristics of germline RAD51C/D PV carriers, including the evaluation of HRD status.
This retrospective cohort study included 91 index patients plus 90 relatives carrying germline RAD51C/D PV (n = 181) in Spanish hospitals from January 1, 2014, to December 31, 2021. Genomic and functional HRD biomarkers were assessed in untreated breast and ovarian tumor samples (n = 45) from June 2022 to February 2023.
Clinical and pathologic characteristics were assessed using descriptive statistics. Genomic HRD by genomic instability scores, functional HRD by RAD51, and gene-specific loss of heterozygosity were analyzed. Associations between HRD status and tumor subtype, age at diagnosis, and gene-specific loss of heterozygosity in RAD51C/D were investigated using logistic regression or the t test.
A total of 9507 index patients were reviewed, and 91 patients (1.0%) were found to carry a PV in RAD51C/D; 90 family members with a germline PV in RAD51C/D were also included. A total of 157 of carriers (86.7%) were women and 181 (55.8%) had received a diagnosis of cancer, mainly breast cancer or ovarian cancer. The most prevalent PVs were c.1026+5_1026+7del (11 of 56 19.6%) and c.709C>T (9 of 56 16.1%) in RAD51C and c.694C>T (20 of 35 57.1%) in RAD51D. In untreated breast cancer and ovarian cancer, the prevalence of functional and genomic HRD was 55.2% (16 of 29) and 61.1% (11 of 18) for RAD51C, respectively, and 66.7% (6 of 9) and 90.0% (9 of 10) for RAD51D. The concordance between HRD biomarkers was 91%. Tumors with the same PV displayed contrasting HRD status, and age at diagnosis did not correlate with the occurrence of HRD. All breast cancers retaining the wild-type allele were estrogen receptor positive and lacked HRD.
In this cohort study of germline RAD51C/D breast cancer and ovarian cancer, less than 70% of tumors displayed functional HRD, and half of those that did not display HRD were explained by retention of the wild-type allele, which was more frequent among estrogen receptor-positive breast cancers. Understanding which tumors are associated with RAD51C/D and HRD is key to identify patients who can benefit from targeted therapies, such as PARP (poly adenosine diphosphate-ribose polymerase) inhibitors.
CHEK2 variants are associated with intermediate breast cancer risk, among other cancers. We aimed to comprehensively describe CHEK2 variants in a Spanish hereditary cancer (HC) cohort and adjust the ...American College of Medical Genetics and Genomics and the Association for Molecular Pathology (ACMG‐AMP) guidelines for their classification. First, three CHEK2 frequent variants were screened in a retrospective Hereditary Breast and Ovarian Cancer cohort of 516 patients. After, the whole CHEK2 coding region was analyzed by next‐generation sequencing in 1848 prospective patients with HC suspicion. We refined ACMG‐AMP criteria and applied different combined rules to classify CHEK2 variants and define risk alleles. We identified 10 CHEK2 null variants, 6 missense variants with discordant interpretation in ClinVar database, and 35 additional variants of unknown significance. Twelve variants were classified as (likely)‐pathogenic; two can also be considered “established risk‐alleles” and one as “likely risk‐allele.” The prevalence of (likely)‐pathogenic variants in the HC cohort was 0.8% (1.3% in breast cancer patients and 1.0% in hereditary nonpolyposis colorectal cancer patients). Here, we provide ACMG adjustment guidelines to classify CHEK2 variants. We hope that this study would be useful for variant classification of other genes with low effect variants.
Comprehensive analysis of CHEK2 variants found in 2346 hereditary cancer patients and adjustment of the American College of Medical Genetics and Genomics and the Association for Molecular Pathology (ACMG‐AMP) guidelines for their classification.
RNA analyses are a potent tool to identify spliceogenic effects of DNA variants, although they are time-consuming and cannot always be performed. We present splicing assays of 20 variants that ...represent a variety of mutation types in 10 hereditary cancer genes and attempt to incorporate these results into American College of Medical Genetics and Genomics (ACMG) classification guidelines. Sixteen single-nucleotide variants, 3 exon duplications, and 1 single-exon deletion were selected and prioritized by in silico algorithms. RNA was extracted from short-term lymphocyte cultures to perform RT-PCR and Sanger sequencing, and allele-specific expression was assessed whenever possible. Aberrant transcripts were detected in 14 variants (70%). Variant interpretation was difficult, especially comparing old classification standards to generic ACMG guidelines and a proposal was devised to weigh functional analyses at RNA level. According to the ACMG guidelines, only 12 variants were reclassified as pathogenic/likely pathogenic because the other two variants did not gather enough evidence. This study highlights the importance of RNA studies to improve variant classification. However, it also indicates the challenge of incorporating these results into generic ACMG guidelines and the need to refine these criteria gene specifically. Nevertheless, 60% of variants were reclassified, thus improving genetic counseling and surveillance for carriers of these variants.
To evaluate the association between a previously published 313 variant-based breast cancer (BC) polygenic risk score (PRS
) and contralateral breast cancer (CBC) risk, in BRCA1 and BRCA2 pathogenic ...variant heterozygotes.
We included women of European ancestry with a prevalent first primary invasive BC (BRCA1 = 6,591 with 1,402 prevalent CBC cases; BRCA2 = 4,208 with 647 prevalent CBC cases) from the Consortium of Investigators of Modifiers of BRCA1/2 (CIMBA), a large international retrospective series. Cox regression analysis was performed to assess the association between overall and ER-specific PRS
and CBC risk.
For BRCA1 heterozygotes the estrogen receptor (ER)-negative PRS
showed the largest association with CBC risk, hazard ratio (HR) per SD = 1.12, 95% confidence interval (CI) (1.06-1.18), C-index = 0.53; for BRCA2 heterozygotes, this was the ER-positive PRS
, HR = 1.15, 95% CI (1.07-1.25), C-index = 0.57. Adjusting for family history, age at diagnosis, treatment, or pathological characteristics for the first BC did not change association effect sizes. For women developing first BC < age 40 years, the cumulative PRS
5th and 95th percentile 10-year CBC risks were 22% and 32% for BRCA1 and 13% and 23% for BRCA2 heterozygotes, respectively.
The PRS
can be used to refine individual CBC risks for BRCA1/2 heterozygotes of European ancestry, however the PRS
needs to be considered in the context of a multifactorial risk model to evaluate whether it might influence clinical decision-making.
Large genomic rearrangements are estimated to account for approximately 5-10% of all disease-causing mutations in BRCA1 and BRCA2 genes in patients with hereditary breast and ovarian cancer syndrome ...(HBOC). We use MRC-Holland Multiplex Ligation-dependent Probe Amplification (MLPA) to screen for such rearrangements in patients with HBOC and as a first step in our genetic testing workflow. The technique was applied to a set of 310 independent patients and detected eight different copy number alterations, corresponding to 2.6% of the studied samples. MLPA was also found to identify point mutations located in probe sequences. As commercial MLPA tests are not suitable for determining the specific breakpoints or for defining the exact extent of rearrangements, we applied a set of different complementary techniques to characterize these genetic alterations with greater precision. Long-range PCR amplification, RNA analysis, SNP-array chips, non-commercial MLPA probes, and FISH analysis were used to fully define the extent and mechanism of each alteration. In BRCA1, six rearrangements were characterized: deletion of E22, duplication of E9-E24, deletion of E16-E23, deletion of E1-E13, deletion of E1-E2 and duplication of E1-E2. In BRCA2, we studied a deletion of E15-E16 and a deletion of E1-E24. To the best of our knowledge, this is the most comprehensive study of the nature and underlying molecular causes of these mutational events in the BRCA1/2 genes.
Comprehensive genetic testing of the breast cancer susceptibility genes
BRCA1
and
BRCA2
identified approximately 16% of variants of unknown significance (VUS), a significant proportion of which could ...affect the correct splicing of the genes. Our aim is to establish a workflow for classifying VUS in these complex genes, the first stage of which is splicing analysis. We used a combined approach consisting of five in silico splicing prediction programs and RT-PCR analysis for a set of 26 variants not previously studied at the mRNA level and six variants that had already been studied, four of which were used as positive controls as they were found to affect the splicing of these genes and the other two were used as negative controls. We identified a splicing defect in 8 of the 26 newly studied variants and ruled out splicing alteration in the remaining 18 variants. The results for the four positive and the two negative control variants were consistent with results presented in the literature. Our results strongly suggest that the combination of RNA analysis and in silico programs is an important step towards the classification of VUS. The results revealed a very high correlation between experimental data and in silico programs when using tools for predicting acceptor/donor sites but a lower correlation in the case of tools for identifying ESE elements.
Introduction - Actionable somatic molecular alterations are found in 15% to 20% of NSCLC in Europe. NSCLC is a tumor observed in patients with germline TP53 variants causing Li-Fraumeni syndrome ...(LFS), but its somatic molecular profile is unknown. Methods - Retrospective study of clinical and molecular profiles of patients with NSCLC and germline TP53 variants. Results - Among 22 patients with NSCLC and LFS (n = 23 lung tumors), 64% were women, median age was 51 years, 84% were nonsmokers, 73% had adenocarcinoma histological subtype, and 84% were diagnosed with advanced-stage disease. These patients harbored 16 distinct germline TP53 variants; the most common was p.R158H (5/22; three in the same family). Personal and family histories of cancer were reported in 71% and 90% of patients, respectively. In most cases (87%, 13/15), lung cancer was diagnosed with a late onset. Of the 21 tumors analyzed, somatic oncogenic driver mutations were found in 19 of 21 (90%), EGFR mutations in 18 (exon 19 deletion in 12 cases, L858R in three cases, and G719A, exon 20 insertion, and missing mutation subtype, each with one case), and ROS1 fusion in one case. A PI3KCA mutation was concurrently detected at diagnosis in three EGFR exon 19-deleted tumors (3/12). The median overall survival was 37.3 months in 14 patients treated with EGFR inhibitors; seven developed resistance, five (71%) acquired EGFR-T790M mutation, and one had SCLC transformation. Conclusions - Driver oncogenic alterations were observed in 90% of the LFS tumors, mainly EGFR mutations; one ROS1 fusion was also observed. The germline TP53 variants and lung cancer carcinogenesis driven by oncogenic processes need further evaluation.
The clinical spectrum of germline mismatch repair (MMR) gene variants continues increasing, encompassing Lynch syndrome, Constitutional MMR Deficiency (CMMRD), and the recently reported
MSH3
...-associated polyposis. Genetic diagnosis of these hereditary cancer syndromes is often hampered by the presence of variants of unknown significance (VUS) and overlapping phenotypes. Two
PMS2
VUS, c.2149G>A (p.V717M) and c.2444C>T (p.S815L), were identified in trans in one individual diagnosed with early-onset colorectal cancer (CRC) who belonged to a family fulfilling clinical criteria for hereditary cancer. Clinico-pathological data, multifactorial likelihood calculations and functional analyses were used to refine their clinical significance. Likelihood analysis based on cosegregation and tumor data classified the c.2444C>T variant as pathogenic, which was supported by impaired MMR activity associated with diminished protein expression in functional assays. Conversely, the c.2149G>A variant displayed MMR proficiency and protein stability. These results, in addition to the conserved PMS2 expression in normal tissues and the absence of germline microsatellite instability (gMSI) in the biallelic carrier ruled out a CMMRD diagnosis. The use of comprehensive strategies, including functional and clinico-pathological information, is mandatory to improve the clinical interpretation of naturally occurring MMR variants. This is critical for appropriate clinical management of cancer syndromes associated to MMR gene mutations.
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