Ovarian cancer BRCA1 mutation detection: Protein truncation test (PTT) outperforms single strand conformation polymorphism analysis (SSCP)

Recent studies have shown that the BRCA1 tumor suppressor gene plays a role in the develops ment of both hereditary and sporadic ovarian cancer. Since several different mechanisms may give rise to tumor gene defects, a better understanding of these mechanisms may identify BRCA1 as an attractive ther apeutic target in ovarian cancer. Sequencing this large gene is not practic al on a population-wide basis. The optimal screening strategy is yet to be determined. The purpose of our study is to compare two common screening tec hniques: the protein truncation test (PTT) and single strand conformational polymorphism analysis (SSCP). Ninety-four patients with epithelial ovarian cancer and available snap-frozen tissue were screened for BRCA1 mutations by both PTT (five individual PCR reactions with complete translation of the product in the TNT System (Promega, Madison, WI)) and SSCP (41 individual PCR reactions covering the entire coding sequence). All abnormal results we re confirmed by sequencing. A paired peripheral blood DNA sample was utiliz ed to determine if the sequence abnormality was a germline mutation. Twenty , three mutations in BRCA1 were found in 22 patients (14 germline, eight so matic, one unknown) including four novel mutations: E489X, 3558delT, 3871de lGTCT, del exon 7-10. Although the predictive value of a negative test was close for the two methods (PTT 99.1%, SSCP 99.8%), the comparison of positi ve predictive value overwhelmingly favored PTT (100.0%, vs. 26.4%, respecti vely). The specificity for PTT was 100.0% while the sensitivity was 82.6%. While for SSCP, the specificity was 99.0% and the sensitivity was only 60.9 %. The concordance rate for the two screening tests was 88.9%. Only SSCP ca n detect missense mutations. PTT is a superior screening test for truncatin g BRCA1 mutations that are expected to be of clinical significance. Hum Mut at 18:337-344, 2001. (C) 2001 Wiley-Liss, Inc.