Identification of point mutations and large rearrangements in the BRCA1 gene in 667 Turkish unselected ovarian cancer patients

Abstract

Objective The aim of this study was to evaluate the prevalence and spectrum of a known founder mutation, 5382insC and large genomic rearrangements (LGRs) in BRCA1 in ovarian cancer patients in Turkey. The additional aim was to determine the genetic testing strategy in Turkish breast/ovarian cancer family. Methods Six hundred and sixty-seven ovarian cancer patients from five large geographical regions in Turkey, 61 of which had family history of breast/ovarian cancer, were tested for the mutation 5382insC by mutagenically separated polymerase chain reaction and direct sequencing of the entire coding sequence and the splicing sites. Additionally, multiplex ligation-dependent probe amplification (MLPA) was performed for large mutational scanning of BRCA1 gene in unselected ovarian cancer. Results In this study, BRCA1 point mutations were observed in 1% of all patients and 9.8% of familial cases: 5382insC, unique novel missense variant-G1748S and unclassified splice site variant IVS20 + 5A > T. 5382insC was observed in two patients. However, G1748S, previously unreported, was found in four patients and thus led to the conclusion that this mutation may be unique to Turkey. A splice site variant, IVS20 + 5A > T, was detected in three patients, with two of them including G1748S and IVS20 + 5A > T, together. Using MLPA, six different distinct LGRs in BRCA1 were observed: the deletion of E1A-1B-2, E11, E17-19, E18 and E18-19 and duplication of E5-9. The prevalence of LGRs in this study was 40.9% among patients with family history. The deletion of E1A-1B-2 was the common mutation, and patients with this deletion were referred to us from four different geographical regions in Turkey. Therefore, it was hypothesized that this deletion covering E1-2 is common in Turkey. Conclusion LGRs in BRCA1 were strongly associated with positive family history among the Turkish population. On the basis of these findings, it can be recommended that a low-cost screening for LGRs in BRCA1 may be the first-line mutation detection method in families with strong breast/ovarian cancer history in Turkey.