Constitutional BRCA1 and MGMT Methylation Are Significant Risk Factors for Triple-Negative Breast Cancer and High-Grade Serous Ovarian Cancer in Saudi Women

Breast cancer (BC) and ovarian cancer (OC) are rapidly increasing in Saudi Arabia. BRCA1 and MGMT epimutations have been linked to a higher risk of these malignancies. The present research investigated the impact of these epimutations on the prevalence of BC and OC among Saudi women. DNA methylation was evaluated using methylation-specific PCR, whereas mRNA expression levels were assessed using qRT-PCR. We evaluated white blood cell (WBC)–BRCA1 methylation in 1958 Saudi women (908 BC patients, 223 OC patients, and 827 controls). MGMT methylation was determined in 1534 of the 1958 women (700 BC patients, 223 OC patients, and 611 controls). BRCA1 methylation was detected in 8.6% of the controls and 11% of the BC patients. This epimutation was linked to 13.8% of the early-onset BC patients (p = 0.003) and 20% of the triple-negative breast cancer (TNBC) patients (p = 0.0001). BRCA1 methylation was also detected in 14% of the OC patients (p = 0.011), 19.4% of patients aged <55 years (p = 0.0007), and 23.4% of high-grade serous ovarian cancer (HGSOC) patients. In contrast, the BRCA1 mutation was detected in 24% of the OC patients, 27.4% of patients aged ≥55 years, and 26.7% of the HGSOC patients. However, MGMT methylation was detected in 10% of the controls and 17.4% of the BC patients (p = 0.0003). This epimutation was linked to 26.4% of the late-onset BC patients (p = 0.0001) and 11% of the TNBC patients. MGMT methylation was also found in 15.2% of the OC patients (p = 0.034) and 19.1% of HGSOC patients (p = 0.054). Furthermore, 36% of the BRCA1-methylated patients and 34.5% of the MGMT-methylated patients had a family history of cancer, including breast and ovarian cancer. Notably, BRCA1 and MGMT mRNA levels were greater in the WBC RNA of the BC patients and cancer-free methylation carriers than in that of the OC patients. Our data indicate that BRCA1 and MGMT epimutations significantly contribute to the development of breast cancer and ovarian cancer in Saudi cancer patients. These blood-based biomarkers could help identify female patients at high risk of developing TNBC and HGSOC at an early age.