Abstract LB-441: Mutation in SLX4 gen in a multiple case breast cancer family

Fanconi Anemia (FA) is a genetically heterogeneous, rare autosomal recessive disorder characterized by development abnormalities, bone marrow failure, and childhood cancers. Over the past few years, a common genetic basis for FA and breast and/or ovarian cancer susceptibility has been uncovered. In particular, BRCA2 (FANCD1), BRIP1 (also known as BACH1 and FANCJ), PALB2 (FANCN), and RAD51C germ-line mutations have been found to lead both to FA (when biallelic) and to increased breast and/or ovarian cancer risk (when monoallelic). Recently, two studies demonstrated that biallelic germ-line mutations in SLX4, which encodes an endonuclease, cause a previously unknown FA subtype (FA-P). Therefore, SLX4 should be considered a bona fide candidate gene for breast cancer susceptibility, as suggested in both studies. We have screened 347 non-BRCA1/BRCA2 index cases from multiple case breast and/or ovarian cancer families for point mutations in the SLX4 gene. The whole coding sequence and flanking intronic regions were analyzed using High Resolution Melting (HRM) analysis followed by direct sequencing of abnormal melting curve samples. An SLX4 missense change in c.1114C>T (p.Arg372Trp) was detected in a family with four cases of breast cancer in two generations. This mutation segregates with disease within the family and is not present in the dbSNP (build 34). Polyphen-2 and SIFT in silico analysis tools predict a deleterious effect on protein structure and multiple alignment within orthologous proteins suggests a high degree of conservation. Previous studies in FA patients have identified two different splicing mutations (c.1163+2T>A and c.1163+3dupT) that cause in frame exon 5 skipping. The resulting protein (p.Arg317_Phe387del) lacks two repeated UBZ4 domains known to interact with other endonucleases, mismatch repair proteins, and ubiquitin. It has been suggested that UBZ4 may be involved in targeting SLX4 to sites of DNA damage by binding to ubiquitinated proteins. The missense change we have found introduces a highly hydrophobic amino acid within the same region, which could affect the folding of the UBZ4 domain or disrupt a specific protein-protein interaction. Our study supports a role for SLX4 in breast cancer susceptibility. Further studies performed in larger cohorts will be necessary to determine the prevalence of SLX4 mutations among breast cancer risk factors. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr LB-441. doi:1538-7445.AM2012-LB-441