Consanguinity Protecting Effect Against Breast Cancer among Tunisian Women: Analysis of BRCA1 Haplotypes.

The purpose of this study is to assess the effect of consanguinity on breast cancer incidence in Tunisia. We conducted a case-control study to evaluate the involvement of heterozygote and homozygote haplotypes of BRCA1 gene SNPs according to consanguinity among 40 cases of familial breast cancer, 46 cases with sporadic breast cancer and 34 healthy controls. We showed significant difference in consanguinity rate between breast cancer patients versus healthy controls P = 0.001. Distribution of homozygous BRCA1 haplotypes among healthy women versus breast cancer patients was significantly different; p=0.02. Parental consanguinity seems to protect against breast cancer in the Tunisian population.

MicroRNAs expression in triple negative vs non triple negative breast cancer in Tunisia: interaction with clinical outcome.

INTRODUCTION: MicroRNAs are small, non coding regulatory molecules containing approximately 21 to 25 nucleotides. They function as controllers of expression at post transcriptional levels of most human protein-coding genes and play an essential role in cell signaling pathways. The objective of the present study is to evaluate the expression profile of the following micro-RNAs: miR-10b, miR-17, miR-21, miR-34a, miR-146a, miR-148a and miR-182, and to determine their possible interaction in triple-negative and non triple-negative primary breast cancers based on clinical outcome. METHODS: 60 triple-negative and non triple-negative breast cancer cases, along with their corresponding normal samples were investigated in relation to the expression of the seven studied miRNAs using qPCR Syber Green. RESULTS: We observed that miR-21, miR-146a and miR-182 were significantly over expressed in triple negative breast cancer. Moreover, miR-10b, miR-21 and miR-182 were significantly associated to lymph node metastases occurrence in triple negative breast carcinoma while only miR-10b was associated with grade III in non triple negative breast cancer cases. Almost all the analyzed microRNAs were strongly associated with patients' genico-obstetric history in non triple negative breast cancer cases except for miR-34a. All the studied microRNAs were strongly correlated with the use of the contraceptive pills in non triple negative breast cancer groups. The additive effect of hormonal factors in triple negative breast cancer cases showed an association with all the studied miRs except for miR-34 and miR-146a. CONCLUSION: The studied microRNAs are strongly influenced by environmental factors especially with hormonal patients' history. Moreover, miR-10b, miR-21 and miR-182 could be defined as biomarkers in breast cancer to predict both lymph node metastases and grade III occurrence.

Wild-type genotypes of BRCA1 gene SNPs combined with micro-RNA over-expression in mammary tissue leading to familial breast cancer with an increased risk of distant metastases' occurrence.

Germ line deleterious mutations of BRCA1 gene are not the unique factor that could inactivate BRCA1 protein which leads to familial breast cancer onset with distant metastases' occurrence. The present research explores the role that could be assigned to BRCA1 SNPs to inactivate BRCA1 protein and therefore to the occurrence of familial breast cancer with an increased risk of distant metastases' occurrence. The presence or the absence of BRCA1 protein was first analyzed by applying the immunohistochemistry technique to the tumors with sporadic and familial breast cancer. Then, a case-control study was conducted including 40 patients with familial breast cancer, 46 ones with sporadic breast cancer and 34 healthy controls based on the genotyping of nine BRCA1 SNPs (c.442.58delT, c.2082C>T, c.2311T>C, c.2612C>T, c.3113A>G, c.3119G>A, c.3548A>G, c.4308T>C and 4837A>G) via direct sequencing. Finally, the functional role that could be assigned to these SNPs was focused upon. miRbase site was used as a bioinformatics tool to predict potential micro-RNAs (miRs) targeting SNPs that are associated with familial breast cancer according to the results of this research. These predicted miRs were confirmed by Q-PCR analysis and correlated with BRCA1 protein expression among patients along with potential distant metastases. Clinical outcome showed that distant metastasis concerned 45 % of familial breast cancer patients and 19.5 % with sporadic breast cancer. Analysis of BRCA1 protein expression revealed a negative staining among 46.6 % of familial breast cancer patients and only 16.6 % within sporadic breast cancer ones. The association of four variants was identified within BRCA1 gene (c.442.58 delT, c.2311T>C, c.2612C>T and c.4308T>C) to familial breast cancer across their wild genotypes. miR-1179 was selected as potential miR that targets the region of BRCA1 mRNA containing the c.2311T>C variant within the TT genotype. The expression of miR-1179 was significantly associated with familial breast cancer patients without BRCA1 deleterious mutations compared to those with sporadic breast cancer according to TT genotype along with BRCA1 negative staining and according to the occurrence of distant metastases. Combination between TT genotype of c.2311T>C and miR-1179 over-expression could generate a lack of BRCA1 protein leading to a high risk of familial breast cancer with distant metastases.

Thymidylate synthase polymorphism in sporadic colorectal and gastric cancer in Tunisian population: a predictive role in 5-fluorouracil based chemotherapy treatment.

In our study, we investigate the possible association of thymidylate synthase polymorphism, 28 bp tandem repeat in 5'-UTR (transcription enhancer element) with susceptibility of colorectal and gastric cancer in Tunisian population. Because thymidylate synthase provides an effective prediction of chemotherapy treatment based on 5-fluorouracil, our interest in this study was focused on finding an eventual interaction between thymidylate synthase polymorphism and treatment of sporadic colorectal and gastric cancer. Whole blood was collected into EDTA tube, after centrifugation for 15 min, the buffy coat was isolated, and genotyping of TS 5'-UTR polymorphism was carried by polymerase chain reaction method using appropriate primers. Determination of the different genotypes was done directly on the stained agarose gel. Our finding showed that the 5'tandem repeat polymorphism of the thymidylate synthase gene is associated with risk of colorectal cancer; thus, LL (3R/3R) genotype is significantly high in patients with colorectal cancer compared to controls (P = 0.002; OR 2.7; 95 % CI 1.4-5.2). In addition, we found a positive association between SL (2R/3R) genotype in the thymidylate synthase 5'-UTR and gastric cancer risk (P = 0.015; OR 4.46; 95 % CI 1.08-19.64). Furthermore, we found a correlation of thymidylate synthase polymorphism with the fluorouracil-based therapy regimes and also with preoperatory radiation in patients with colorectal cancer. Thymidylate synthase is associated with risk of colorectal cancer but not with gastric cancer; however, heterozygous SL (2R/3R) polymorphism is associated with risk of gastric cancer; moreover, the 5' tandem repeat polymorphism of thymidylate synthase gene was an independent predictor of the clinical treatment.

Genetic variability of the P120' surface protein gene of Mycoplasma hominis isolates recovered from Tunisian patients with uro-genital and infertility disorders.

BACKGROUND: Among the surface antigens of Mycoplasma hominis, the P120' protein was previously shown to elicit a subtle antibody response and appears to be relatively conserved. To get better insight into the evolution of this protein, we analysed the genetic variability of its surface exposed region in 27 M. hominis isolates recovered from the genital tract of Tunisian patients with infertility disorders. METHODS: All specimens were processed for culture and PCR amplification of the N-terminal surface exposed region of p120' gene. PCR products were sequenced to evaluate the genetic variability, to test for adaptive selection, and to infer the phylogenetic relationship of the M. hominis isolates. RESULTS: Sequence analysis showed a total of 25 single nucleotide polymorphisms distributed through 23 polymorphic sites, yielding 13 haplotypes. All but one mutation were confined within three distinct regions. Analysis of the amino acid-based phylogenetic tree showed a predominant group of 17 closely related isolates while the remaining appear to have significantly diverged. CONCLUSION: By analysing a larger sample of M. hominis recovered from patients with urogenital infections, we show here that the P120' protein undergoes substantial level of genetic variability at its surface exposed region.