Consistent TP53 mutations in BRCA1 and sporadic basal-like breast tumors, while infrequent in luminal BRCA1 tumors.

Abstract

Abstract Abstract #4070 Breast tumors with a germline mutation of BRCA1 (BRCA1 tumors) and Basal-Like Carcinoma (BLC) have been shown to be associated with a high rate of TP53 mutations. Because it has also been shown that BRCA1 tumors frequently display a basal-like phenotype, we sought to determine whether TP53 mutations were correlated to the hereditary BRCA1 mutated status or to the particular histological type of these tumors. We first explored the status of the TP53 gene in a series of 28 BRCA1 BLCs using immunohistochemistry, direct sequencing of the coding sequence, and functional assay in yeast (FASAY), and compared it to the status of TP53 in 27 series of sporadic (non hereditary) BLCs. With this sensitive approach, TP53 was found consistently mutated in BRCA1 (28/28) and sporadic (26/27) BLCs. However, mutation spectrum was different, in particular with a much higher rate of insertion/deletion in BRCA1 BLCs (12/27) than in the sporadic group (2/25). Secondly, we analyzed the incidence of TP53 mutations in 10 BRCA1 luminal tumors, using the same strategy. Surprisingly, only 3 of these 10 tumors were mutated, a frequency similar to that found in matched sporadic luminal tumors. In conclusion, TP53 mutation is a mandatory event in BRCA1 or sporadic BLCs, but not a common feature of BRCA1 luminal tumors. Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 4070.