No mutations in the BACH1 gene in BRCA1 and BRCA2 negative breast‐cancer families linked to 17q22

Abstract

Dear Sir,At least 10% of all breast cancer is estimated to result from an inherited predisposition. 1 Mutations in 2 genes, BRCA1 and BRCA2, have been shown to confer a very high risk for breast and ovarian cancer. 2 A significant proportion of familial cases, however, cannot be attributed to BRCA1 or BRCA2 mutations, 3,4 and additional breast cancer susceptibility gene(s) may account for a fraction of high-risk families. Recently, it was suggested that a novel protein, BACH1, a member of the DEAH helicase family could be one such gene. 5 BACH1 maps to 17q22 and consists of 20 exons, spanning over 180 kb of genomic sequence. It encodes a 130 kDa polypeptide that binds directly to BRCT repeats of BRCA1 and interferes with normal double-strand break repair in a manner that was dependent on the BRCA1 binding. 5 Furthermore, 2 germ-line missense mutations were detected in 65 individuals with breast cancer (1 in familial and 1 with early-onset breast cancer) lacking mutations in both BRCA1 and BRCA2. None of them occurred in any of 200 normal controls. We have evaluated a putative contribution of this locus to breast cancer susceptibility by analyzing 197 breast cancer families in which we did not detect BRCA1 and BRCA2 mutations ( Table I). The exon 11 of BRCA1 was screened on genomic DNA using PTT and the remaining exons were analyzed using SSCP, CDGE or direct sequencing. 4,6 The BRCA2 gene was screened by PTT using genomic DNA for exon 10 and 11 and using RNA for all other exons, or the entire gene was screened using direct sequencing of genomic DNA. 4,7 High-risk breast cancer families were identified and collected through the Cancer Counseling Clinic at the Karolinska Hospital. The families were selected if 2 or more close relatives were affected with breast cancer, and if the proband was counseled a 2-4 times increased risk for the disease compared to the normal population. Blood samples were obtained from the affected and unaffected family members with informed consent. Linkage analysis involved 285 members of 102 breast cancer families, including 245 breast cancer patients. The average age at diagnosis in the patients was 54.7 years old, ranging between 30-72. Nine of the families were breast-ovarian cancer families. Additional 95 patients with a family history of breast cancer, negative for BRCA1 and BRCA2 mutations, were selected to be screened for mutations in the BACH1 gene. Control females were mothers of Swedish patients with IgA deficiency ascertained as described previously 8 and apparently unrelated blood donors drawn from the Swedish population.Genotyping was carried out using 19 fluorescent-labeled microsatellite markers on chromosome 17 (D17S1308; D17S1845; D17S1810; D17S1298; D17S1832; D17S974; D17S1303; D17S969; D17S921; D17S122; D17S1294; D17S1293; D17S1299; D17S809; D17S1290; D17S31B11; D17S1301; D17S784; D17S928), including 3 markers flanking the BACH1 gene (underlined). The amplified fragments were analyzed on an ABI377 automated sequencer (Applera, USA), together with internal size standar...

Fanconi anaemia genes and susceptibility to cancer

“…Several subsequent studies screened the BRIP1 coding sequence in large numbers of BRCA1/2 negative familial breast cancer families from populations in Northern Europe (Luo et al, 2002;Karppinen et al, 2003;Vahteristo et al, 2006), North America (Rutter et al, 2003) and Australia (Lewis et al, 2005). This resulted in the detection of one frameshift mutation and several missense mutations, none of which segregated with breast cancer in the families.…”

Further evidence for the contribution of the BRCA1-interacting protein-terminal helicase 1 (BRIP1) gene in breast cancer susceptibility

“…Previous studies have analyzed potential associations between BRIP1 variants and breast cancer risk, either by mutation analysis or by genotyping, to select single nucleotide polymorphisms (SNPs) within the gene (Lei and Vorechovsky, 2003;Rutter et al, 2003;Sigurdson et al, 2004;Lewis et al, 2005;Garcia-Closas et al, 2006;Vahteristo et al, 2006). Although the rs2048718 (5ꞌ-untranslated region, UTR), rs4988345 (exon 15), and rs4986764 (exon 18) polymorphisms have been previously examined in the context of breast cancer, these genetic association studies have failed to produce consistent results (Luo et al, 2002;Lei and Vorechovsky, 2003;Song et al, 2007;Pabalan et al, 2013). Furthermore, several important SNPs, such as rs2048718, rs4986764, rs4986763, rs11079454, and rs7213430, have not been included in previous studies.…”

BACH1 517C→T transition impairs protein translocation to nucleus: A role in breast cancer susceptibility?

“…Three samples with both germline and tumor DNA were available and were analysed by PCR-SSCP as described previously. 10 The rare 517T allele was retained in tumors of all 3 cases and no obvious allelic imbalance or loss of heterozygosity was observed in any of these samples (data not shown).…”

“…However, a follow-up study reported no mutations in the germline of 29 multiple-case breast cancer families with positive nonparametric linkage scores to short tandem repeats flanking the BACH1 locus at 17q and of 95 unrelated individuals with familial breast cancer who had no detectable mutation in BRCA1 and BRCA2. 10 The latter study reported a 517C3 T transition on 5 of 1,586 chromosomes in the Swedish population (allelic frequency 0.3%), leading to a substitution of arginine (R) 173 for cysteine (C) in a putative nuclear localization sequence (NLS) of BACH1. 10 NLS is a short peptide sequence necessary and sufficient for nuclear localization of a protein, 11 and single amino acid substitution involving critical residues in NLS has been shown to impair the nuclear localization.…”

“…10 The latter study reported a 517C3 T transition on 5 of 1,586 chromosomes in the Swedish population (allelic frequency 0.3%), leading to a substitution of arginine (R) 173 for cysteine (C) in a putative nuclear localization sequence (NLS) of BACH1. 10 NLS is a short peptide sequence necessary and sufficient for nuclear localization of a protein, 11 and single amino acid substitution involving critical residues in NLS has been shown to impair the nuclear localization. 12 Deletion of arginine or lysine in the NLS of BLM resulted in an even distribution of the EGFP-BLM fusion protein in the cytoplasm and nucleus, whereas a substitution with a nonbasic amino acid reduced the nuclear localization of the fusion protein.…”