BRCA1 Promoter Methylation and Clinicopathological Characteristics in Sporadic Breast Cancer Patients in Indonesia

Abstract

Objective: The aim of this study was to investigate the BRCA1 promoter methylation and clinicopathological characteristics in sporadic breast cancer patients in Indonesia. Methods: In this cohort study, we selected 90 patients with stage I-III who had definitive surgery at our institution in 2011-2014. Demographic and clinical data regarding pathological stage, breast cancer treatment, outcome etc. were collected from the medical records. Twelve patients had incomplete information on follow up and 18 samples had insufficient tissues for the experiment. Sixty patients with adequate cancer tissues and complete follow up record were analyzed, only 56 patients were analyzed because 4 samples mRNA expression could not be detected. The Mann–Whitney U tests for non-normally distributed groups were used to compare the levels expression of BRCA1 mRNA between methylated and non-methylated samples. Chi-square tests were used to compare methylation status, BRCA1 mRNA expression and clinicopathological characteristics. P value < 0.05 was considered as statistically significant correlation. Data analysis was held by using the GraphPad PRISM 7 (GraphPad Software Inc., USA). Results: DNA and RNA were isolated from primary tumor tissues of 56 breast cancer patients. BRCA1 promoter methylation was detected in 48 of 56 patients (85%). Level of BRCA1 mRNA expression was associated with decreased methylation level in the BRCA1 promoter regions suggesting the role of epigenetic silencing. However, there was no statistically significant association among methylation levels, BRCA1 mRNA transcript level with clinicopathological factors. Conclusion: To our knowledge, this is the first study investigating methylation status and level of BRCA1 mRNA transcripts among breast cancer patients in Indonesia. We found that the prevalence of BRCA1 promoter methylation is higher than other studies from different populations. However, further investigation involving larger number of patients is required.

Keywords: Breast cancer; BRCA1; DNA methylation; BRCA1 promoter methylation; gene expression.

Figure 1

Number of Selected Specimens for Analysis

Figure 2

Location of Methylation-Specific Primers (MF-MR) and Unmethylation-Specific Primers (UF-UR) in BRCA1 Sequence (NCBI Accession Number: NG_005905.2)

Figure 3

Location of BRCA1 Forward and Reverse Primers in BRCA1 mRNA Sequence (NCBI Accession Number: NM_007294.3)

Figure 4

Electrophoresis of Amplification Products Specific Promoter Region BRCA1 from Bisulfite-Treated DNA in Human Tumor Tissue. Each line consists amplification products from methylated (U), 75bp or unmethylated (M), 86bp primer

Figure 5

The Relationship between BRCA1 Promoter Methylation and mRNA Transcript Levels. Lines note median expression value, p-value represents Mann-Whitney test.