Sequencing tests assaying panels of genes or whole exomes are widely available for cancer risk evaluation. However, methods for classification of variants resulting from this testing are not well ...studied. We evaluated the ability of a variant-classification methodology based on American College of Medical Genetics and Genomics (ACMG) guidelines to define the rate of mutations and variants of uncertain significance (VUS) in 180 medically relevant genes, including all ACMG-designated reportable cancer and non-cancer-associated genes, in individuals who met guidelines for hereditary cancer risk evaluation. We performed whole-exome sequencing in 404 individuals in 253 families and classified 1,640 variants. Potentially clinically actionable (likely pathogenic LP or pathogenic P) versus nonactionable (VUS, likely benign, or benign) calls were 95% concordant with locus-specific databases and Clinvar. LP or P mutations were identified in 12 of 25 breast cancer susceptibility genes in 26 families without identified BRCA1/2 mutations (11%). Evaluation of 84 additional genes associated with autosomal-dominant cancer susceptibility identified LP or P mutations in only two additional families (0.8%). However, individuals from 10 of 253 families (3.9%) had incidental LP or P mutations in 32 non-cancer-associated genes, and 9% of individuals were monoallelic carriers of a rare LP or P mutation in 39 genes associated with autosomal-recessive cancer susceptibility. Furthermore, 95% of individuals had at least one VUS. In summary, these data support the clinical utility of ACMG variant-classification guidelines. Additionally, evaluation of extended panels of cancer-associated genes in breast/ovarian cancer families leads to only an incremental clinical benefit but substantially increases the complexity of the results.
Cancer Genomics and Inherited Risk STADLER, Zsofia K; SCHRADER, Kasmintan A; VIJAI, Joseph ...
Journal of clinical oncology,
03/2014, Letnik:
32, Številka:
7
Journal Article
Recenzirano
Odprti dostop
Next-generation sequencing (NGS) has enabled whole-exome and whole-genome sequencing of tumors for causative mutations, allowing for more accurate targeting of therapies. In the process of sequencing ...the tumor, comparisons to the germline genome may identify variants associated with susceptibility to cancer as well as other hereditary diseases. Already, the combination of massively parallel sequencing and selective capture approaches has facilitated efficient simultaneous genetic analysis (multiplex testing) of large numbers of candidate genes. As the field of oncology incorporates NGS approaches into tumor and germline analyses, it has become clear that the ability to achieve high-throughput genotyping surpasses our current ability to interpret and appropriately apply the vast amounts of data generated from such technologies. A review of the current state of knowledge of rare and common genetic variants associated with cancer risk or treatment outcome reveals significant progress, as well as a number of challenges associated with the clinical translation of these discoveries. The combined efforts of oncologists, genetic counselors, and cancer geneticists will be required to drive the paradigm shift toward personalized or precision medicine and to ensure the incorporation of NGS technologies into the practice of preventive oncology.
Recent studies have identified mutation signatures of homologous recombination deficiency (HRD) in over 20% of breast cancers, as well as pancreatic, ovarian, and gastric cancers. There is an urgent ...need to understand the clinical implications of HRD signatures. Whereas
mutations confer sensitivity to platinum-based chemotherapies, it is not yet clear whether mutation signatures can independently predict platinum response.
In this observational study, we sequenced tumor whole genomes (100× depth) and matched normals (60×) of 93 advanced-stage breast cancers (33 platinum-treated). We computed a published metric called HRDetect, independently trained to predict
status, and assessed its capacity to predict outcomes on platinum-based chemotherapies. Clinical endpoints were overall survival (OS), total duration on platinum-based therapy (TDT), and radiographic evidence of clinical improvement (CI).
HRDetect predicted
status with an area under the curve (AUC) of 0.94 and optimal threshold of 0.7. Elevated HRDetect was also significantly associated with CI on platinum-based therapy (AUC = 0.89;
= 0.006) with the same optimal threshold, even after adjusting for
mutation status and treatment timing. HRDetect scores over 0.7 were associated with a 3-month extended median TDT (
= 0.0003) and 1.3-year extended median OS (
= 0.04).
Our findings not only independently validate HRDetect, but also provide the first evidence of its association with platinum response in advanced breast cancer. We demonstrate that HRD mutation signatures may offer clinically relevant information independently of
mutation status and hope this work will guide the development of clinical trials.
.
Somatic alterations of the lymphoid transcription factor gene PAX5 (also known as BSAP) are a hallmark of B cell precursor acute lymphoblastic leukemia (B-ALL), but inherited mutations of PAX5 have ...not previously been described. Here we report a new heterozygous germline variant, c.547G>A (p.Gly183Ser), affecting the octapeptide domain of PAX5 that was found to segregate with disease in two unrelated kindreds with autosomal dominant B-ALL. Leukemic cells from all affected individuals in both families exhibited 9p deletion, with loss of heterozygosity and retention of the mutant PAX5 allele at 9p13. Two additional sporadic ALL cases with 9p loss harbored somatic PAX5 substitutions affecting Gly183. Functional and gene expression analysis of the PAX5 mutation demonstrated that it had significantly reduced transcriptional activity. These data extend the role of PAX5 alterations in the pathogenesis of pre-B cell ALL and implicate PAX5 in a new syndrome of susceptibility to pre-B cell neoplasia.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Tumor genetic sequencing identifies potentially targetable genetic alterations with therapeutic implications. Analysis has concentrated on detecting tumor-specific variants, but recognition of ...germline variants may prove valuable as well.
To estimate the burden of germline variants identified through routine clinical tumor sequencing.
Patients with advanced cancer diagnoses eligible for studies of targeted agents at Memorial Sloan Kettering Cancer Center are offered tumor-normal sequencing with MSK-IMPACT, a 341-gene panel. We surveyed the germline variants seen in 187 overlapping genes with Mendelian disease associations in 1566 patients who had undergone tumor profiling between March and October 2014.
The number of presumed pathogenic germline variants (PPGVs) and variants of uncertain significance per person in 187 genes associated with single-gene disorders and the proportions of individuals with PPGVs in clinically relevant gene subsets, in genes consistent with known tumor phenotypes, and in genes with evidence of second somatic hits in their tumors.
The mean age of the 1566 patients was 58 years, and 54% were women. Presumed pathogenic germline variants in known Mendelian disease-associated genes were identified in 246 of 1566 patients (15.7%; 95% CI, 14.0%-17.6%), including 198 individuals with mutations in genes associated with cancer susceptibility. Germline findings in cancer susceptibility genes were concordant with the individual's cancer type in only 81 of 198 cases (40.9%; 95% CI, 34.3%-47.9%). In individuals with PPGVs retained in the tumor, somatic alteration of the other allele was seen in 39 of 182 cases (21.4%; 95% CI, 16.1%-28.0%), of which 13 cases did not show a known correlation of the germline mutation and a known syndrome. Mutations in non-cancer-related Mendelian disease genes were seen in 55 of 1566 cases (3.5%; 95% CI, 27.1%-45.4%). Almost every individual had more than 1 variant of uncertain significance (1565 of 1566 patients; 99.9%; 95% CI, 99.6%-99.9%).
Germline variants are common in individuals undergoing tumor-normal sequencing and may reveal otherwise unsuspected syndromic associations.
Dyskeratosis congenita (DC) is a heterogeneous inherited bone marrow failure and cancer predisposition syndrome in which germline mutations in telomere biology genes account for approximately ...one-half of known families. Hoyeraal Hreidarsson syndrome (HH) is a clinically severe variant of DC in which patients also have cerebellar hypoplasia and may present with severe immunodeficiency and enteropathy. We discovered a germline autosomal recessive mutation in RTEL1, a helicase with critical telomeric functions, in two unrelated families of Ashkenazi Jewish (AJ) ancestry. The affected individuals in these families are homozygous for the same mutation, R1264H, which affects three isoforms of RTEL1. Each parent was a heterozygous carrier of one mutant allele. Patient-derived cell lines revealed evidence of telomere dysfunction, including significantly decreased telomere length, telomere length heterogeneity, and the presence of extra-chromosomal circular telomeric DNA. In addition, RTEL1 mutant cells exhibited enhanced sensitivity to the interstrand cross-linking agent mitomycin C. The molecular data and the patterns of inheritance are consistent with a hypomorphic mutation in RTEL1 as the underlying basis of the clinical and cellular phenotypes. This study further implicates RTEL1 in the etiology of DC/HH and immunodeficiency, and identifies the first known homozygous autosomal recessive disease-associated mutation in RTEL1.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Germline structural variants (SVs) are challenging to resolve by conventional genetic testing assays. Long-read sequencing has improved the global characterization of SVs, but its sensitivity at ...cancer susceptibility loci has not been reported. Nanopore long-read genome sequencing was performed for nineteen individuals with pathogenic copy number alterations in BRCA1, BRCA2, CHEK2 and PALB2 identified by prior clinical testing. Fourteen variants, which spanned single exons to whole genes and included a tandem duplication, were accurately represented. Defining the precise breakpoints of SVs in BRCA1 and CHEK2 revealed unforeseen allelic heterogeneity and informed the mechanisms underlying the formation of recurrent deletions. Integrating read-based and statistical phasing further helped define extended haplotypes associated with founder alleles. Long-read sequencing is a sensitive method for characterizing private, recurrent and founder SVs underlying breast cancer susceptibility. Our findings demonstrate the potential for nanopore sequencing as a powerful genetic testing assay in the hereditary cancer setting.
The variant curation guidelines published in 2015 by the American College of Medical Genetics and Genomics and the Association for Molecular Pathology (ACMG/AMP) provided the genetics community with ...a framework to assess variant pathogenicity; however, these rules are not gene specific. Germline pathogenic variants in the CDH1 gene cause hereditary diffuse gastric cancer and lobular breast cancer, a clinically challenging cancer predisposition syndrome that often requires a multidisciplinary team of experts to be properly managed. Given this challenge, the Clinical Genome Resource (ClinGen) Hereditary Cancer Domain prioritized the development of the CDH1 variant curation expert panel (VCEP) to develop and implement rules for CDH1 variant classifications. Here, we describe the CDH1 specifications of the ACMG/AMP guidelines, which were developed and validated after a systematic evaluation of variants obtained from a cohort of clinical laboratory data encompassing ∼827,000 CDH1 sequenced alleles. Comparing previously reported germline variants that were classified using the 2015 ACMG/AMP guidelines to the CDH1 VCEP recommendations resulted in reduced variants of uncertain significance and facilitated resolution of variants with conflicted assertions in ClinVar. The ClinGen CDH1 VCEP recommends the use of these CDH1‐specific guidelines for the assessment and classification of variants identified in this clinically actionable gene.
Germline pathogenic variants in the CDH1 gene cause hereditary diffuse gastric cancer and lobular breast cancer. The ClinGen CDH1 Expert Panel developed and implemented rules for CDH1 variant curation, providing the genetic community with a gene‐specific framework for the classification of variants identified in this clinically actionable gene. Overall, the Expert Panel specifications resulted in reduced variants of uncertain significance and facilitated resolution of variants with conflicted assertions in ClinVar.
Cancer is a disease of the genome, in which mutations in particular genes and pathways give rise to tissue-specific genotype-phenotype correlations. In tumors associated with hereditary cancer ...syndromes, a person is generally born with the first mutation relevant to the development of their cancer. In this chapter we will discuss the genes that have been associated with germline mutations that confer a moderate to high risk for ovarian carcinoma.
Background
Multi‐gene panel testing is replacing single‐gene testing for patients with suspected hereditary cancer syndromes. The detection of a hereditary cancer syndrome allows tested individuals ...to initiate enhanced primary and secondary prevention efforts—where available—with a view to reduce disease burden. Current policy prevents testing programmes from communicating genetic test results with potentially affected family members, yet it is well documented that tested individuals face multiple challenges in initiating such discussions with relatives.
Objective
In response to this challenge, we sought patient recommendations about how to improve genetic risk communication to enhance interfamilial discussions about primary and secondary disease prevention.
Design
We conducted 25 semi‐structured interviews with individuals who received genetic testing through British Columbia’s Hereditary Cancer Program between 2017 and 2018. Interviews were professionally transcribed and analysed using a constant comparative approach.
Results
Participants described difficulty engaging in conversations with relatives who were resistant to receiving genetic risk information, when communicating with younger relatives and where participants reported strained familial relationships. Participants recommended that testing facilities provide a summary of results and implications and that resources be made available to prepare patients for challenging discussions with family members.
Discussion
Our study demonstrates that individuals undergoing genetic testing for suspected hereditary cancer syndromes would benefit from additional supportive resources alongside genetic counselling. Providing this on‐going support will enhance the accurate and transparent communication of risk to facilitate the uptake of cascade testing and enhanced prevention strategies.
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