Screening of BRCA1 mutation using immunohistochemical staining with C-terminal and N-terminal antibodies in familial ovarian cancers

We examined the subcellular Localization of BRCA1 proteins using immunohist ochemical staining with C-terminal (GLK-2 antibody) and N-terminal (Ab-2 an tibody) monoclonal antibodies in 44 familial ovarian cancers. Among these, 24 cases were associated with 13 independent germ-Line mutations of BRCA1, and loss of heterozygosity (LOH) at one or more BRCA1 microsatellite marker s was found in all 21 informative tumors tested. With GLK-2 antibody, cytop lasmic staining was observed in 15 of 16 tumors (93.8%) with mutation in ex on 11, and BRCA1 staining was absent in 8 of 8 tumors (100%) with mutation in exons other than exon 11, When immunohistochemical staining was performe d with Ab-2 antibody, both nuclear and cytoplasmic staining were observed i n 14 of 16 tumors (87.5%) with mutation in exon 11, interestingly, nuclear staining was observed in 3 of 3 tumors (100%) with mutation downstream of e xon 11, even though no staining was detected in 5 of 5 tumors (100%) with m utation upstream of exon 11, On the other hand, in familial ovarian cancers without BRCA1 mutations, nuclear staining or both nuclear and cytoplasmic staining was observed in 18 of 20 specimens (90%) and 20 of 20 specimens (1 00%) with GLK-2 antibody and with Ab-2 antibody, respectively. These result s suggest that an immunohistochemical assay in combination with employing t he C-terminal and the N-terminal antibodies appears to have potential as a reliable and useful technique for the screening of BRCA1 mutations, at leas t to predict the status of mutation, upstream or downstream of exon 11.