Tumor Suppressor Gene Mutations in Iraqi Women with Breast Cancer and Their Relatives

Abstract

Background: Breast cancer is characterized by various malignant tumors arise from breast tissues,age, genetic factors,diet and environmental factors,reproductive and hormonal factors, some types of benign breast disease andsocio-economic factors are factors correlated to an enlarged risk of breast cancer.Tumor suppressor genes are genes whose loss of roleresults in the elevation of malignancy. Aim of the Study: The present study was conducted to verify the tumor suppressor gene mutations in breast cancer women and their relatives. Material and Methods: Three groups of samples were included. The first consisted of 100 blocks of formalinfixed, paraffinembedded(FFPE) breast cancer tissuesof women(group 1). The second contained blood samples of 46 breast cancerwomen(group 2). The third comprised blood samples of46 apparently healthy women who were relatives to the breast cancer patients of group two(group 3). The ages of patients of samples tissue were 46.78±11.5 years, while for samples of blood patients were 47.34±11.18 years. The ages of the healthy relatives were 40.79±9.84 years. Five tumor suppressor gene mutations were examined.BRCA1 185delAG, BRCA1 5382insC and BRCA2 6174delT mutations were evaluated by mutagenically separated polymerase chain reaction, while CHEK2 1100delC and Tp53 exon 7 mutations were analyzed by RFLP. Results: The amplification of BRCA1gene for185 delAG mutation revealed amplicons of 335 bp for the wild type and 354 bp for the mutant gene, whereas for 5382 insC mutation exhibited 2 amplicons of sizes 271 bp for the wild type and 295 bp for the mutant gene. The analysis of BRCA26174 delT mutation indicated 2 amplicons of 151 bp for the wild type and 171 bp for the mutant gene. Tp53 exon 7 mutation analysis highlighted an amplicon of 125 bp size. Digestion of thisamplicon with the Hae III enzyme resulted in 2 fragments with sizes of 83 bp and 42 bp for the wild type. CHEK2 1100 delC mutation evaluation showed an amplicon of 116 bp size. Digestion of this amplicon with Sca I enzyme exhibited 2 fragments with sizes of 92 bp and 24 bpfor the wild type. Data analysis demonstrated that 27 (27%) out of the 100 enrolled breast cancer patients of tissue samples have mutations in tumor suppressor genes, 11 (23.9%) out of 46enrolled breast cancer patients of blood samples have such mutations, while 8 (17.4%) out of 46 relatives have these mutations. Nine (9%) patients of group1 were indicated to have BRCA1 185delAGmutation, while 4 (8.7%) and 3 (6.5%)women from groups 2 and3 exhibited the same mutationrespectively. BRCA15382insC mutation was identified in 7 (7%), 3 (6.5%) and 1 (2.2%) women of groups 1, 2 and 3 respectively. The BRCA2 6174delT mutation was observed in 5 (6%), 2 (4.3%) and 2 (4.3%)women of groups 1,2 and 3 respectively. Three (3%) patients of group1, 1 (2.2%) and 1 (2.2%) women from groups 2 and 3 were found to have CHEK2 1100delC respectively. Tp53exon 7 mutation was evident in 2 (2%), 1 (2.2%) and 1 (2.2%) women of groups 1, 2 and 3 respectively. No patient had more than one mutation. Conclusions: About one quarter of the investigated breast cancer patients have mutations in their tumor suppressor genes and 17% of their relatives have such mutations. Most of breast cancer patients enrolled in this study are sporadic not familial breast cancer.