BRCA buccal immunoassay predicts BRCA1 and BRCA2 mutations

Approximately 4% of unaffected, reproductive age women have a significant family history for heritable breast or ovarian cancer. While, BRCA1 and BRCA2 (BRCA) mutation analysis may prove useful in the clinical management of such individuals, such testing is prohibitively expensive. We have developed a rapid, noninvasive. and inexpensive, assay capable of identifying BRCA mutations in buccal cells. Objective: To determine the predictive value of the BRCA buccal immunoassay in the detection BRCA gene mutations. Methods: Buccal cells and peripheral blood were collected from 11 individuals, identified with a greater than 40% risk of carrying a BRCA mutation. To detect protein truncations which are associated with 90% of BRCA mutations, buccal cells were evaluated for BRCA immunoreactivity. Specifically, a qualitative, immunohistochemical comparison using antibodies directed against the amino and carboxy ends of either BRCA proteins, was performed. The presence of diminished immunoreactivity (total or diminished anti-carboxy reactivity relative to anti-amino reactivity) was scored as predictive for mutation. This analysis was compared to the results of BRCA ONA analysis. Results: Of the 11 individuals identified, six were found to have a BRCA1 mutation, two were found to have a BRCA2 mutation, and three were found to carry no mutations at all. The BRCA buccal immunoassay correctly predicted the presence of all eight mutations. Of the three individuals without BRCA mutations, immunoassay correctly predicted no mutation for BRCA1 in all three, while correctly predicting the absence of a BRCA2 mutation in 2 of three individuals. Conclusions: The positive and negative predictive values for this assay were 89% and 100% respectively, suggesting great promise as an inexpensive screen for BRCA mutations.