Identification of candidate cancer predisposing variants by performing whole-exome sequencing on index patients from BRCA1 and BRCA2-negative breast cancer families
BMC CANCER
Authors: Shahi, Rajendra Bahadur; De Brakeleer, Sylvia; Caljon, Ben; Pauwels, Ingrid; Bonduelle, Maryse; Joris, Sofie; Fontaine, Christel; Vanhoeij, Marian; Van Dooren, Sonia; Teugels, Erik; De Greve, Jacques
Abstract
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 frequency1%), 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.
Pharmacogenetic predictors of severe peripheral neuropathy in colon cancer patients treated with oxaliplatin-based adjuvant chemotherapy: a GEMCAD group study
ANNALS OF ONCOLOGY
Authors: Custodio, A.; Moreno-Rubio, J.; Aparicio, J.; Gallego-Plazas, J.; Yaya, R.; Maurel, J.; Higuera, O.; Burgos, E.; Ramos, D.; Calatrava, A.; Andrada, E.; Lopez, R.; Moreno, V.; Madero, R.; Cejas, P.; Feliu, J.
Abstract
The combined analysis of the CCNH rs2230641 and the ABCG2 rs3114018 SNPs independently predict the development of severe oxaliplatin-induced peripheral neuropathy in early-stage colon cancer patients treated with oxaliplatin-based adjuvant chemotherapy. This pharmacogenetic approach might improve the stratification of patients, enabling specific dosing strategies and the assessment of potential neuroprotective therapies.Oxaliplatin-based chemotherapy (CT), widely used as adjuvant therapy for stage III and selected high-risk stage II colon cancer (CC) patients, is often associated with cumulative peripheral neuropathy. Our aim is to identify single-nucleotide polymorphisms (SNPs) in genes involved in oxaliplatin metabolism, DNA repair mechanisms, cell cycle control, detoxification or excretion pathways to predict severe (grade 2-3) oxaliplatin-induced peripheral neuropathy (OXPN) among CC patients treated with oxaliplatin and fluoropyrimidine-based adjuvant CT. Genomic DNA was extracted from formalin-fixed-paraffin-embedded peritumoral samples from 206 high-risk stage II and stage III CC patients receiving oxaliplatin-based adjuvant CT from January 2004 to December 2009. Genotyping was carried out for 34 SNPs in 15 genes using MassARRAY (SEQUENOM) technology. A total of 181 stage II-III CC patients treated with the same CT regimens were enrolled as a validation set. The rs2230641 cyclin H (CCNH) rs2230641 C/C [odd ratio (OR) = 5.03, 95% confidence interval (CI) 1.061-2.41, P = 0.042] and the ATP-binding cassette subfamily G, member 2 (ABCG2) rs3114018 A/A genotypes (OR = 2.67; 95% CI 0.95-4.41; P = 0.059) were associated with a higher risk of severe OXPN. In addition, patients harboring the combination of CCNH C/C and/or the ABCG2 rs3114018 A/A genotypes had a higher risk of grade 2-3 OXPN than those with the CCNH any T and ABCG2 any C genotypes (37.73% versus 19.42%; OR = 2.46; 95% CI 1.19-5.07; P = 0.014) in the logistic regression analysis using age, gender, adjuvant CT regimen and cumulative dose of oxaliplatin as covariates. The ability to predict severe OXPN of this combined analysis was independently validated in the second cohort (58% versus 33.33%; OR = 2.99; 95% CI 1.45-6.13; P = 0.002). Our results suggest that SNPs in CCNH and ABCG2 can modulate the development of severe OXPN among stage II-III CC patients who received oxaliplatin-based CT, thus enabling the individualization of adjuvant treatment.