Genome-Wide Association Studies (GWAS) breast cancer susceptibility loci in Arabs: susceptibility and prognostic implications in Tunisians

Genome-wide Association Studies (GWAS) revealed novel genetic markers for breast cancer susceptibility. But little is known about the risk factors and molecular events associated with breast cancer in Arab Population. Therefore, we designed a broad study to investigate the susceptibility and prognostic implications of the GWAS breast cancer loci in the Tunisian population. In a cohort of 640 unrelated patients with breast cancer and 371 healthy control subjects, we characterized the variation of 9 single nucleotide polymorphisms (SNPs), namely rs1219648, rs2981582; rs8051542, rs12443621, and rs3803662; rs889312; rs3817198; rs13387042 and rs13281615. Only 5 out of 9 GWAS breast cancer loci were found to be significantly associated with breast cancer in Tunisians: The rs1219648 (G vs. A allele: OR = 1.36, P = 1 × 10(−3)) and rs2981582 (A vs. G allele: OR = 1.55, P = 3 × 10(−6)) of FGFR2 gene; the rs8051542 of the TNRC9 gene (T vs. C allele: OR = 1.40, P = 4 × 10(−4)); the rs889312 of the MAP3K1 gene (C vs. A allele: OR = 1.33, P = 3 × 10(−3)) and the rs13281615 located on 8q24 (G vs. A allele: OR = 1.21, P = 0.03). Homozygous variant genotypes of rs2981582 were strongly related to lymph node negative breast cancer (OR = 3.33, P = 6 × 10(−7)) and the minor allele of rs2981582 was associated with increased risk of ER+ tumors (OR = 1.57, P = 0.02; OR = 2.15, P = 0.001, for heterozygous and homozygous variant genotypes, respectively) and increased risk of distant metastasis development (OR = 2.30, P = 4 × 10(−3); OR = 3.57, P = 6 × 10(−5), for heterozygous and homozygous variant genotypes, respectively) in a dose dependent manner. The association for rs8051542 was stronger for high-grade SBR tumors (OR = 2.54, P = 2 × 10(−4)). GG genotype of rs13387042 on 2q35 showed a significant association with the risk of developing distant metastasis (OR = 1.94, P = 0.02). The G allele of rs1219648 in FGFR2 and the A allele of rs13387042 on 2q35 indicated a better prognosis by showing a significantly higher overall survival rates (P = 0.013 and P = 0.005, respectively). In conclusion, GWAS breast cancer FGFR2, TNRC9, MAP3K1, and 8q24 loci are associated with an increased risk of breast cancer and genetic variation in FGFR2 gene may predict the aggressiveness of breast cancer in Tunisians. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s10549-012-2202-6) contains supplementary material, which is available to authorized users

Hereditary breast cancer in Middle Eastern and North African (MENA) populations: identification of novel, recurrent and founder BRCA1 mutations in the Tunisian population

Germ-line mutations in BRCA1 breast cancer susceptibility gene account for a large proportion of hereditary breast cancer families and show considerable ethnic and geographical variations. The contribution of BRCA1 mutations to hereditary breast cancer has not yet been thoroughly investigated in Middle Eastern and North African populations. In this study, 16 Tunisian high-risk breast cancer families were screened for germline mutations in the entire BRCA1 coding region and exon–intron boundaries using direct sequencing. Six families were found to carry BRCA1 mutations with a prevalence of 37.5%. Four different deleterious mutations were detected. Three truncating mutations were previously described: c.798_799delTT (916 delTT), c.3331_3334delCAAG (3450 delCAAG), c.5266dupC (5382 insC) and one splice site mutation which seems to be specific to the Tunisian population: c.212 + 2insG (IVS5 + 2insG). We also identified 15 variants of unknown clinical significance. The c.798_799delTT mutation occurred at an 18% frequency and was shared by three apparently unrelated families. Analyzing five microsatellite markers in and flanking the BRCA1 locus showed a common haplotype associated with this mutation. This suggests that the c.798_799delTT mutation is a Tunisian founder mutation. Our findings indicate that the Tunisian population has a spectrum of prevalent BRCA1 mutations, some of which appear as recurrent and founding mutations

Genetic analysis of hereditary multiple exostoses in Tunisian families: a novel frame-shift mutation in the EXT1 gene

International audienceHereditary multiple exostoses (HME) is an autosomal dominant orthopaedic disorder most frequently caused by mutations in the EXT1 gene. The aim of the present study is to determine the underlying molecular defect of HME in two multigenerational Tunisian families with 21 affected members and to examine the degree of intrafamilial variability. Linkage analysis was performed using three microsatellite markers encompassing the EXT1 locus and mutation screening was carried out by direct sequencing. In family 1, evidence for linkage to EXT1 was obtained on the basis of a maximum LOD score of 4.26 at theta = 0.00 with D8S1694 marker. Sequencing of the EXT1 revealed a heterozygous G > T transversion (c.1019G > T) in exon 2, leading to a missense mutation at the codon 340 (p.Arg340Leu). In family 2 we identified a novel heterozygous 1 bp deletion in the exon 1 (c.529\₅31delA) leading to a premature codon stop and truncated EXT1 protein expression (p.Lys177LysfsX15). This mutation was associated with the evidence of an intrafamilial clinical variability and considered to be a novel disease-causing mutation in the EXT1 gene. These findings provide additional support for the involvement of EXT1 gene in the HME disease

Combined effects of <it>IL-8 </it>and <it>CXCR2 </it>gene polymorphisms on breast cancer susceptibility and aggressiveness

Abstract Background Interleukin-8 (IL-8/CXCL-8) is a prototype of the ELR+CXC chemokines that play an important role in the promotion and progression of many human cancers including breast cancer. We have recently showed the implication of polymorphism (-251) T/A of IL-8 gene in the susceptibility and prognosis of breast carcinoma. IL-8 acts through its CXCR1 and CXCR2 receptors. CXCR2, expressed on the endothelial cells, is the receptor involved in mediating the angiogenic effects of ELR+CXC chemokines and in particular IL-8. In the current study, we investigated the susceptibility and prognostic implications of the genetic variation in CXCR2 in breast carcinoma. We also confirmed the implication of IL-8 (-251) T/A polymorphism in a larger cohort. Finally, we combined the IL-8 and CXCR2 variant alleles and analyzed their effects in breast cancer risk and prognosis. Methods We used the allele-specific polymerase chain reaction to characterize the variation of IL-8 and CXCR2 for 409 unrelated Tunisian patients with breast carcinoma and 301 healthy control subjects. To estimate the relative risks, Odds ratios and 95% confidence intervals were calculated using unconditional logistic regression after adjusting for the known risk factors for breast cancer. Associations of the genetic marker with the rates of breast carcinoma-specific overall survival and disease-free survival were assessed using univariate and multivariate analyses. Results A highly significant association was found between the homozygous CXCR2 (+ 1208) TT genotype (adjusted OR = 2.89; P = 0.008) and breast carcinoma. A significantly increased risk of breast carcinoma was associated with IL-8 (-251) A allele (adjusted OR = 1.86; P = 0.001). The presence of two higher risk genotypes (the TA and TT in IL-8, and the TT in CXCR2) significantly increased the risk of developing breast carcinoma (adjusted OR = 4.15; P = 0.0004). The CXCR2 (+ 1208) T allele manifested a significant association with an aggressive phenotype of breast carcinoma as defined by a large tumor size, a high histological grade, and auxiliary's lymph node metastasis. A significant association between the IL-8 (-251) A allele and the aggressive form of breast carcinoma was also found. Moreover, the presence of the IL-8 (-251) A and/or the CXCR2 (+ 1208) T allele showed a significant association with a decreased overall survival and disease-free survival in breast carcinoma patients. Conclusion Our results indicated that the polymorphisms in IL-8 and CXCR2 genes are associated with increased breast cancer risk, as well as disease progress, supporting our hypothesis for IL-8 and ELR+CXC chemokine receptor (CXCR2) involvement in breast cancer pathogenesis.</p

Contribution of BRCA1 5382insC mutation in triple negative breast cancer in Tunisia

Abstract Background Triple negative breast cancer (TNBC) has been classified as a disease subgroup defined by the lack of expression of estrogen and progesterone receptors as well as the absence of the human epidermal growth factor receptor-2 (HER2) overexpression. Germline mutations in the BRCA1 gene have been associated with TNBC. Approximately 70% of breast cancers arising in BRCA1 mutation carriers and up to 23% of breast cancers in BRCA2 carriers display a triple negative phenotype. However, the contribution and the frequency of BRCA1 mutations in individuals with TNBC, not specifically selected for age at diagnosis or enriched family history of breast/ovarian cancer, have not been investigated in the Tunisian population and are to be established. The aim of the present study was to assess the contribution and the prevalence of recurrent BRCA1 germline mutation (5382inC) in Tunisian women with TNBC unselected for family history or age at onset. Methods For BRCA1 5382inC mutation detection, the exon 20 coding region and exon–intron boundaries of BRCA1 was analyzed using direct DNA sequencing. A total of 33 DNA samples from Tunisian women diagnosed with TNBC and unselected for family history or age at onset were analyzed. Results The 5382inC mutation was identified in 2 out of 33 women with TNBC with an overall prevalence of 6% (2/33). The detection rate of the 5382inC mutation among TNBC women with family history of breast cancer was 25% (2/8). The two 5382inC mutation carriers were postmenopausal and diagnosed at the age of 50 and 57. When stratified by age, the frequency of BRCA1 mutation in patients diagnosed at age ≥ 50 years was 8.7% (2/23). Conclusions Our results confirm a noticeable contribution of BRCA1 5382inC mutation in TNBC development in Tunisia and further indicate that screening for 5382insC mutation in the BRCA1 gene is of interest in genetic testing in our population. Additionally, our data highlight that receptor triple negativity could be an effective selection criterion for BRCA1 genetic test in our population and should therefore be considered in genetic testing guidelines in Tunisia

E-cadherin genetic variants predict survival outcome in breast cancer patients

Abstract Background E-cadherin is a major component of adherens junctions that regulates cell shape and maintains tissue integrity. A complete loss or any decrease in cell surface expression of E-cadherin will interfere with the cell-to-cell junctions’ strength and leads to cell detachment and escape from the primary tumor site. In this prospective study, three functional single nucleotide polymorphisms (−347G/GA, rs5030625; −160C/A, rs16260; +54C/T, rs1801026), were found to modulate E-cadherin expression. Methods 577 DNA samples from breast cancer (BC) cases were genotyped by polymerase chain reaction-restriction fragment length polymorphism (PCR–RFLP). Results We detected no significant correlations between each polymorphism and the clinical parameters of the patients whereas the GACC haplotype was significantly associated with low SBR grading. Overall survival analysis showed that both −347G/G and +54C/C wild (wt) genotypes had a significantly worse effect compared to the other genotypes (non-wt). Moreover, carrying simultaneously both the −347 and +54 wt genotypes confers a significantly higher risk of death. However, with metastatic recurrence, the death-rate was null in patients carrying the non-wt genotypes, and attained 37% in those carrying the wt genotype. A multivariate analysis showed that these two polymorphisms are independent prognostic factors for overall survival in BC patients. Conclusions Our results support the fact that E-cadherin genetic variants control disease severity and progression and could be a marker of disease outcome. These findings could be useful in selecting patients that should be monitored differently