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.

Hereditary breast cancer accounts for 3-8% of all breast cancers, with mutations in the BRCA1 and BRCA2 genes responsible for up to 30% of these. To investigate the prevalence of BRCA1 and BRCA2 gene mutations in breast cancer patients with affected relatives in Tunisia, we studied 36 patients who had at least one first degree relative with breast and/or ovarian cancer Thirtyfour 34 patients were suggestive of the BRCA1 mutation and two were suggestive of the BRCA2 mutation, based on the presence of male breast cancer detected in their corresponding pedigrees. Four mutations in BRCA1 were detected, including a novel frame-shift mutation (c.211dupA) in two unrelated patients and three other frameshift mutations -c.4041delAG, c.2551delG and c.5266dupC. Our study is the first to describe the c.5266dupC mutation in a non-Jewish Ashkenazi population. Two frameshift mutations (c.1309del4 and c.5682insA) were observed in BRCA2. Nineteen percent (7/36) of the familial cases had deleterious mutations of the BRCA1 or BRCA2 genes. Almost all patients with deleterious mutations of BRCA1 reported a family history of breast and/or ovarian cancer in the index case or in their relatives. Our data are the first to contribute to information on the mutation spectrum of BRCA genes in Tunisia, and we give a recommendation for improving clinical genetic testing policy.

BackgroundInterleukin-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.MethodsWe 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.ResultsA 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.ConclusionOur 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.

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 9 10 -3 ) and rs2981582 (A vs. G allele: OR = 1.55, P = 3 9 10 -6 ) of FGFR2 gene; the rs8051542 of the TNRC9 gene (T vs. C allele: OR = 1.40, P = 4 9 10 -4 ); the rs889312 of the MAP3K1 gene (C vs. A allele: OR = 1.33, P = 3 9 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 9 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 9 10 -3 ; OR = 3.57, P = 6 9 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 9 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.

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