Correlation of Clinical and Pathological Parameters with the Diversity and Genetic Evolution of Breast Cancer in Senegalese Women

Aims: The purpose of this study was to assess the hypothesis that genetic diversity of breast cancer is related to clinical and pathological tumors characteristics.
Study Design: Representative sequences of mitochondrial Cytochrome b gene of cancerous tissues were analyzed to determinate diversity and genetic evolution of breast tumors in Senegalese women.
Place and Duration of Study: Department of biology Animal (University Cheikh Anta Diop), laboratory of molecular biology (IRD-CBGP), 2011-2013.
Methodology: Genetic diversity of breast tumors in 57 Senegalese patients was estimated by analyzing sequences of the Cytochrome b mitochondrial coding gene. The Cytochrome b sequences from cancerous tissues were aligned using BioEdit version 7.0.8. Number of polymorphic sites, parsimony informative sites, the rate of transitions/transversions and the nucleotide frequency were calculated using MEGA 5.05. Genetic distance (d) was calculated with MEGA 5 using the Kimura 2-parameter (K2P) model. The index of genetic differentiation (Fst) used to describe the distribution of the genetic diversity between sub-groups was calculated with the software DnaSP version 10.5.01. The significance level (P-value) was 0.05.
Results: Analyses have revealed a high score of haplotype (Hd=0.991+/-0.008) and nucleotide diversity (Pi=0.15650+/-0.01326). Statistical correlations have shown a positive association between the risk factors (age of the patients, appearance of the first menstruation beyond 12 years, number of gestation) and nucleotide diversity of tumors (P<0.0001). Statistical analyses based on t-test showed a positive association between age, date of onset of the first menstruation and nucleotide diversity (Pi), between healthy and cancerous tissues for each patient (P<0.0001).
Conclusion: Our results have shown an important genetic diversity in breast tumors. A strong genetic differentiation was noted depending on the number of gestations.