Relationship between mutation of BRCA1 and susceptibility to early onset of breast cancer

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To detect the prevalence of Breast Cancer Susceptibility Gene 1 (BRCA1) mutations and single nucleotide polymorphism (SNP) among young patients with breast cancer and to study the relationship between BRCA1 gene mutation and susceptibility to breast cancer. 30 samples of breast cancer tissue were collected from female patients with breast cancer diagnosed when they were aged < or = 35 5 of which had at least one first-degree relative affected with breast cancer. Genomic DNA was extracted from the breast cancer tissues. The PCR products were amplified in the coding sequence of exon 2, 11C, 11F, 11L, 11I, 16, and 20 by using polymerase chain reaction. Then the PCR products were analyzed using DNA direct sequencing. The sequence was compared with the DNA Star-MagAlign software. A total of 14 sequence variations in BRCA1 gene were identified, including 3 frameshift mutations (cDNA2639, 2640delTA, 3343 delG, and 3398delT) and 11 spot mutations (cDNA 2570 C > T, cDNA 2620 A > T, 1473 A > G, 1561 C > T, 1594G > A, 2206 A > G, 2227 T > C, 2659 C > A, 2806T > C, 3307 A > G, and 3375 G > A). Three patients with these mutations had a family history of breast cancer. The mutation frequency of BRCA1 was 10% (3/30). No mutation was found in the exons 16 and 20. Patients with breast cancer aged < or = 35 have BRCA1 mutations located in the exon 11 mainly. The mutation frequency of the breast cancer patients aged < or = 35 with breast cancer family history is higher than those without family history. Three frameshift mutation sites may be related to early onset of breast cancer.