Genetic analyses of DNA repair pathway associated genes implicate new candidate cancer predisposing genes in ancestrally defined ovarian cancer cases.

Not all familial ovarian cancer (OC) cases are explained by pathogenic germline variants in known risk genes. A candidate gene approach involving DNA repair pathway genes was applied to identify rare recurring pathogenic variants in familial OC cases not associated with known OC risk genes from a population exhibiting genetic drift. Whole exome sequencing (WES) data of 15 OC cases from 13 families tested negative for pathogenic variants in known OC risk genes were investigated for candidate variants in 468 DNA repair pathway genes. Filtering and prioritization criteria were applied to WES data to select top candidates for further analyses. Candidates were genotyped in ancestry defined study groups of 214 familial and 998 sporadic OC or breast cancer (BC) cases and 1025 population-matched controls and screened for additional carriers in 605 population-matched OC cases. The candidate genes were also analyzed in WES data from 937 familial or sporadic OC cases of diverse ancestries. Top candidate variants in ERCC5, EXO1, FANCC, NEIL1 and NTHL1 were identified in 5/13 (39%) OC families. Collectively, candidate variants were identified in 7/435 (1.6%) sporadic OC cases and 1/566 (0.2%) sporadic BC cases versus 1/1025 (0.1%) controls. Additional carriers were identified in 6/605 (0.9%) OC cases. Tumour DNA from ERCC5, NEIL1 and NTHL1 variant carriers exhibited loss of the wild-type allele. Carriers of various candidate variants in these genes were identified in 31/937 (3.3%) OC cases of diverse ancestries versus 0-0.004% in cancer-free controls. The strategy of applying a candidate gene approach in a population exhibiting genetic drift identified new candidate OC predisposition variants in DNA repair pathway genes.

Germline pathogenic variants in patients with early-onset neuroendocrine neoplasms.

Neuroendocrine neoplasms (NENs) are a rare group of cancers with heterogeneous behaviour and mostly of unknown aetiology. Excluding some infrequent hereditary cancer syndromes, the extent and clinical significance of mutations in other cancer predisposing genes (CPGs) are not known. We aimed to investigate the frequency of pathogenic and likely germline pathogenic variants (GPVs) in known CPGs in young adults with NEN and the clinical and molecular characteristics of these patients. We recruited 108 patients with lung or digestive NEN diagnosed between 18 and 50 years and performed targeted sequencing of 113 CPGs on germline DNA. For some patients, tumour features such as loss of heterozygosity (LOH), tumour mutation burden and microsatellite instability were evaluated. GPVs were detected in 17 patients (15.7%). Median age, sex, stage at diagnosis, family history of NENs or any personal history of neoplasm were similar between patients with or without GPVs. GPV carriers had more gastric (P = 0.084), functioning NEN (P = 0.041), positive family history of cancer (P = 0.015) and exclusively well-differentiated histology. Genes affected were mostly involved in DNA repair (CHEK2, ERCC2, ERCC3, XPC, MSH6, POLE and SLX4), with most GPVs found in MUTYH (four cases). LOH was performed in eight tumours and detected only in an SLX4-positive case. Overall, our findings indicate a role of inherited genetic alterations, particularly in DNA repair genes, in NEN carcinogenesis in young adults. These patients more often had a family history of cancer and functioning NENs.

The Genetic and Molecular Analyses of RAD51C and RAD51D Identifies Rare Variants Implicated in Hereditary Ovarian Cancer from a Genetically Unique Population.

To identify candidate variants in RAD51C and RAD51D ovarian cancer (OC) predisposing genes by investigating French Canadians (FC) exhibiting unique genetic architecture. Candidates were identified by whole exome sequencing analysis of 17 OC families and 53 early-onset OC cases. Carrier frequencies were determined by the genetic analysis of 100 OC or HBOC families, 438 sporadic OC cases and 1025 controls. Variants of unknown function were assayed for their biological impact and/or cellular sensitivity to olaparib. RAD51C c.414G>C;p.Leu138Phe and c.705G>T;p.Lys235Asn and RAD51D c.137C>G;p.Ser46Cys, c.620C>T;p.Ser207Leu and c.694C>T;p.Arg232Ter were identified in 17.6% of families and 11.3% of early-onset cases. The highest carrier frequency was observed in OC families (1/44, 2.3%) and sporadic cases (15/438, 3.4%) harbouring RAD51D c.620C>T versus controls (1/1025, 0.1%). Carriers of c.620C>T (n = 7), c.705G>T (n = 2) and c.137C>G (n = 1) were identified in another 538 FC OC cases. RAD51C c.705G>T affected splicing by skipping exon four, while RAD51D p.Ser46Cys affected protein stability and conferred olaparib sensitivity. Genetic and functional assays implicate RAD51C c.705G>T and RAD51D c.137C>G as likely pathogenic variants in OC. The high carrier frequency of RAD51D c.620C>T in FC OC cases validates previous findings. Our findings further support the role of RAD51C and RAD51D in hereditary OC.

Germline Structural Variations in Cancer Predisposition Genes.

In addition to single nucleotide variations and small-scale indels, structural variations (SVs) also contribute to the genetic diversity of the genome. SVs, such as deletions, duplications, amplifications, or inversions may also affect coding regions of cancer-predisposing genes. These rearrangements may abrogate the open reading frame of these genes or adversely affect their expression and may thus act as germline mutations in hereditary cancer syndromes. With the capacity of disrupting the function of tumor suppressors, structural variations confer an increased risk of cancer and account for a remarkable fraction of heritability. The development of sequencing techniques enables the discovery of a constantly growing number of SVs of various types in cancer predisposition genes (CPGs). Here, we provide a comprehensive review of the landscape of germline SV types, detection methods, pathomechanisms, and frequency in CPGs, focusing on the two most common cancer syndromes: hereditary breast- and ovarian cancer and gastrointestinal cancers. Current knowledge about the possible molecular mechanisms driving to SVs is also summarized.

[Pregnancy-preserving and maternal-fetal management in a patient with rare large cell neuroendocrine carcinoma of the uterine cervix].

OBJECTIVE: To explore the strategy of pregnancy-preserving and maternal- fetal management in patients with primary gynecologic neuroendocrine tumors (gNETs) during pregnancy. METHODS: We performed whole genome sequencing (WGS) for analyzing maternal and fetal somatic and germline single nucleotide variations (SNVs) and small insertions and deletions (InDels) for a 29-year-old pregnant woman diagnosed with stage IB2 large cell neuroendocrine carcinoma (LCNEC) and adenocarcinoma in the cervix. A systematic literature review was performed to explore the strategies for treatment of such rare histological type while maintaining pregnancy. RESULTS: Global case analysis of cervical NETs during pregnancy suggested that negative lymph node metastasis and an early FIGO stage were potentially associated with a good prognosis of the patients. In the case presented herein, a pregnancy-preserving strategy was adopted and favorable maternal-fetal outcomes were achieved after neoadjuvant chemotherapy, radical surgery and postoperative systemic chemotherapy. At 35+5 weeks, the fetus was delivered by caesarian section, and the patient has by now had a disease-free survival of 19 months postoperatively. WGS analysis revealed 6 missense somatic pathogenic mutations in two cancer tissues of the patient, and among them KARS and VEGFA were related with targeted therapy. Five pathogenic germline variants were detected in the patient and her son, suggesting the necessity of a long-term follow-up schedule including precise genetic counselling for both the mother and the child. CONCLUSIONS: Although gNETs in pregnancy are rare and highly risky, pregnancy-preserving managements of gNETs can still be considered and favorable maternalfetal outcomes are possible with proper assessment of the clinical indications and implementation of multimodal treatments. Precise treatment and follow-up strategies based on the results of WGS for risk-reducing intervention of cancer recurrence or occurrence can potentially benefit the patient and the neonate.

Pregnancy-preserving and maternal-fetal management in a patient with rare large cell neuroendocrine carcinoma of the uterine cervix / 南方医科大学学报

OBJECTIVE@#To explore the strategy of pregnancy-preserving and maternal- fetal management in patients with primary gynecologic neuroendocrine tumors (gNETs) during pregnancy.@*METHODS@#We performed whole genome sequencing (WGS) for analyzing maternal and fetal somatic and germline single nucleotide variations (SNVs) and small insertions and deletions (InDels) for a 29-year-old pregnant woman diagnosed with stage IB2 large cell neuroendocrine carcinoma (LCNEC) and adenocarcinoma in the cervix. A systematic literature review was performed to explore the strategies for treatment of such rare histological type while maintaining pregnancy.@*RESULTS@#Global case analysis of cervical NETs during pregnancy suggested that negative lymph node metastasis and an early FIGO stage were potentially associated with a good prognosis of the patients. In the case presented herein, a pregnancy-preserving strategy was adopted and favorable maternal-fetal outcomes were achieved after neoadjuvant chemotherapy, radical surgery and postoperative systemic chemotherapy. At 35@*CONCLUSIONS@#Although gNETs in pregnancy are rare and highly risky, pregnancy-preserving managements of gNETs can still be considered and favorable maternalfetal outcomes are possible with proper assessment of the clinical indications and implementation of multimodal treatments. Precise treatment and follow-up strategies based on the results of WGS for risk-reducing intervention of cancer recurrence or occurrence can potentially benefit the patient and the neonate.

From Targeting Somatic Mutations to Finding Inherited Cancer Predispositions: The Other Side of the Coin.

The expanding use of tumor genome analysis by next generation sequencing to drive target therapies has led to increased germline findings in genes predisposing to hereditary cancer. These putative germline findings obtained from theranostic analyses, such as BRCA1/2 gene testing, large panels, whole-exome, or whole-genome sequencing, need to be managed carefully and in an anticipated way with the patient. Before the genetic analysis of a tumor, specific information should be given to patients, who should be aware that the results may have extra-therapeutic medical issues for themselves and relatives. We previously published a list of 36 actionable genes predisposing to cancer for which informing the patient is recommended prior to pangenomic germline analysis because of available screening or preventive strategies. Here, we report clinical practice considerations and schemes for managing germline findings in tumor analyses, including written informed consent and a multidisciplinary approach involving an oncologist, molecular biologist/pathologist, and geneticist in case of germline findings. A somatic result showing a deleterious mutation in a known predisposing gene in a patient who has consented to this purpose should result in referral to a geneticist who is part of the multidisciplinary team. At any time of the somatic analysis process, the patient may have access to a geneticist consultation if additional information is required. This framework will optimally manage both personalized theranostic issues and specific preventive strategies for individuals and relatives; it will also simplify and accelerate the process of genetic testing.

Identification of candidate cancer predisposing variants by performing whole-exome sequencing on index patients from BRCA1 and BRCA2-negative breast cancer families.

BACKGROUND: In the majority of familial breast cancer (BC) families, the etiology of the disease remains unresolved. To identify missing BC heritability resulting from relatively rare variants (minor allele frequency ≤ 1%), we have performed whole exome sequencing followed by variant analysis in a virtual panel of 492 cancer-associated genes on BC patients from BRCA1 and BRCA2 negative families with elevated BC risk. METHODS: BC patients from 54 BRCA1 and BRCA2-negative families with elevated BC risk and 120 matched controls were considered for germline DNA whole exome sequencing. Rare variants identified in the exome and in a virtual panel of cancer-associated genes [492 genes associated with different types of (hereditary) cancer] were compared between BC patients and controls. Nonsense, frame-shift indels and splice-site variants (strong protein-damaging variants, called PDAVs later on) observed in BC patients within the genes of the panel, which we estimated to possess the highest probability to predispose to BC, were further validated using an alternative sequencing procedure. RESULTS: Exome- and cancer-associated gene panel-wide variant analysis show that there is no significant difference in the average number of rare variants found in BC patients compared to controls. However, the genes in the cancer-associated gene panel with nonsense variants were more than two-fold over-represented in women with BC and commonly involved in the DNA double-strand break repair process. Approximately 44% (24 of 54) of BC patients harbored 31 PDAVs, of which 11 were novel. These variants were found in genes associated with known or suspected BC predisposition (PALB2, BARD1, CHEK2, RAD51C and FANCA) or in predisposing genes linked to other cancer types but not well-studied in the context of familial BC (EXO1, RECQL4, CCNH, MUS81, TDP1, DCLRE1A, DCLRE1C, PDE11A and RINT1) and genes associated with different hereditary syndromes but not yet clearly associated with familial cancer syndromes (ABCC11, BBS10, CD96, CYP1A1, DHCR7, DNAH11, ESCO2, FLT4, HPS6, MYH8, NME8 and TTC8). Exome-wide, only a few genes appeared to be enriched for PDAVs in the familial BC patients compared to controls. CONCLUSIONS: We have identified a series of novel candidate BC predisposition variants/genes. These variants/genes should be further investigated in larger cohorts/case-control studies. Other studies including co-segregation analyses in affected families, locus-specific loss of heterozygosity and functional studies should shed further light on their relevance for BC risk.

Update on genetic predisposition to colorectal cancer and polyposis.

The present article summarizes recent developments in the characterization of genetic predisposition to colorectal cancer (CRC). The main themes covered include new hereditary CRC and polyposis syndromes, non-CRC hereditary cancer genes found mutated in CRC patients, strategies used to identify novel causal genes, and review of candidate genes that have been proposed to predispose to CRC and/or colonic polyposis. We provide an overview of newly described genes and syndromes associated with predisposition to CRC and polyposis, including: polymerase proofreading-associated polyposis, NTHL1-associated polyposis, mismatch repair gene biallelic inactivation-related adenomatous polyposis (including MSH3- and MLH3-associated polyposes), GREM1-associated mixed polyposis, RNF43-associated serrated polyposis, and RPS20 mutations as a rare cause of hereditary nonpolyposis CRC. The implementation of next generation sequencing approaches for genetic testing has exposed the presence of pathogenic germline variants in genes associated with hereditary cancer syndromes not traditionally linked to CRC, which may have an impact on genetic testing, counseling and surveillance. The identification of new hereditary CRC and polyposis genes has not deemed an easy endeavor, even though known CRC-related genes explain a small proportion of the estimated familial risk. Whole-genome sequencing may offer a technology for increasing this proportion, particularly if applied on pedigree data allowing linkage type of analysis. The final section critically surveys the large number of candidate genes that have been recently proposed for CRC predisposition.

Searching for new breast cancer-associated genes. ABRAXAS1 gene mutations in the group of BRCA1-negative patients.

In the present study, we analysed the association of mutations of a BRCA1-associated gene, ABRAXAS1, with the risk of development of breast cancer (BC) in BRCA1-negative women from North-Central Poland. A hundred women with consecutively diagnosed BC and 100 women belonging to the control group were screened for new mutations predisposing to breast cancer. The first step was a test carried out in order to find one of the three Polish founder mutations in the BRCA1 gene. In 96 BRCA1-negative patients two missense variants: c.422C>T and c.1042G>A as well as two intronic variants: IVS3-34G>A, IVS3-44T>C were detected in the ABRAXAS1 gene. The c.422C>T mutation was detected in one of 96 women diagnosed with breast cancer (1.04%); it was not associated with increased risk of disease in this group, compared to the controls (p = 0.49), but the odds ratio was 3.314; 95% CI: 0.122-75.352. IVS3-44T>C was found more frequently in the control group (15/93) than in the tested group (1/85), OR 0.062; 95% CI: 0.008-0.480, p = 0.007, which may suggest protective properties of this variant against tumorigenicity. The data obtained from the present study suggest the necessity for further research to be conducted on the ABRAXAS1 gene in relation to hereditary predisposition to breast cancer.