Molecular Identification of BRCA1&BRCA2 Mutations in Unselected Breast Cancer Patients in Tumor Treatment & Cancer Research Center (TTCRC) - Shendi, River Nile State - Sudan

Abstract

Abstract Background: Breast cancer is the most commonly diagnosed cancer in women worldwide. Up to every eighth woman will develop it during lifetime. Most cases are sporadic, but an estimated (7%) are due to dominantly inherited predisposition, with germline mutations in BRCA1 and BRCA2, predisposing genes. Objectives: The objectives of this study were to determine the role of BRAC1/BRCA2 mutations in breast cancer patients attending Tumor Treatment and Cancer Research Center in Shendi using Sanger Sequencing, to identify the most clinical risk factors and also histological types associated with positive BRCA1&BRCA2 mutations. Design and setting: The study is a cross sectional, hospital based study. The patient’s group size was (52) patients age (30-71) years from Tumor Treatment & Cancer Research Center in Shendi. The control sample size was (30) healthy women matched with their age. (52) Unselected females diagnosed with breast cancer during the period December 2013 to January 2015 and (30) healthy one as control, were interviewed face to face using a validated questionnaire. In addition to their demographic characteristics and risk factors a blood samples (3-5 ml) was taken from each patient and control, genomic DNA was extracted from peripheral blood. Polymerase chain reaction was used for the analysis of exons 11 (two fragments) and 20 of BRCA1 and exon 11(one fragment) of BRCA2. PCR products with specific bands were sending for sequencing at Macrogen - Korea. All data were analyzed using different bioinformatics programs and Statistical Package for the Social Sciences (SPSS Inc.) version 20. Results: The study results found that; invasive ductal carcinoma was seen to be the most histological types 21(45.7%) within age (51-60) years and there was a highly significant statistical correlation linkage between IDC and cancer grade II; (P 0.000). Moreover non- hereditary breast cancer (sporadic) type was revealed to be the most presented 29 (55.8%) compared to hereditary one, second degree relatives was observed to be the most type of cancer occurrence among hereditary types 16 (69.6%) and the breast cancer was the most common malignant cancer type diagnosed among patient’s family relatives17 (73.9%). Results revealed presence of three types of mutations all were presented in BRCA1 in a total of 11 (21.2%) in patients and 8 (26.7%) of control. Two were novel, one of them was point mutation in exon 20 in which (G >A 160980) and was appeared in (8) of each patient and control with frequency (15.4%) and (26.7%) respectively. The second was a missense occurred in exon 11 (S768T) and was appeared in three patients with frequency (5.8%). the third one was silent mutation (rs16940) presented also in exon 11 (L771L) and also was appeared in two patients with frequency (3.8%). There was no mutation presented in BRCA2. Moreover, BRCA1 was found to play a role in both types (hereditary and sporadic) with frequency of (54.5 %( and (45.5 %( respectively. In regards to risk factors associated with mutations, there was statistically significant difference with mutation and tribal / ethnicity (Jaalia) (P= 0.047). But there were no statistically significant differences among mutated patients in related to age (P= 0.233), parity (P= 0.855), family history (P= 0.438), age at menarche (P= 0.775), obesity (P= 0.625), oral contraceptive (P= 0.327), exposure to radiation (P= 0.666) and menopause (P= 0.989). On the other hand, the results fount that; there was strong relation between the breast cancer mutation and the invasive ductal carcinoma histological type in comparison with others, 11(100%), but there was no statistically significant value observed (P= 0.611). Results of the study performed found that; breast cancer mutations were shown to be more occurring with cancer grade II 6 (54.5%), at the same time there was no statistical significant differences seen. Finally, the results indicated that; breast cancer mutations were observed to be more associated with ER, PR, and HER-2 receptors negative with frequency )54.5%(, )63.6%(, and )90.9%( respectively. There was no statistical significant differences related to ER and PR receptors, but there was statistically significant relation with HER-2 was observed. Conclusions: BRCA1 mutations are responsible for a significant proportion of both types of breast cancer in the study population, BRCA2 was not contributed to hereditary breast cancer in this study, and Ethnicity plays a role as risk factor for mutation inheritance.

Key word: BRCA1, BRCA2, Hereditary, Sporadic, Ethnic, TTCRT, Shendi