Mutation screening of BRCA1, BRCA2 and CHEK2*1100delC in Slovak HBOC families

Background

Germline mutations in BRCA1 and BRCA2 genes account for most of the hereditary breast and ovarian cancers (HBOC). Recently, other low-penetrance candidate genes involved in breast cancer susceptibility, CHEK2 and ATM, have emerged. We have initiated mutation screening of suspected HBOC families to improve health care for affected individuals and their asymptomatic relatives in the Slovak Republic.

Methods

We performed a mutational analysis of the entire coding region of the BRCA1 gene in 110 suspected HBOC families from all parts of Slovakia. DNA from peripheral blood lymphocytes was analyzed by the combination of a single-strand conformation polymorphism (SSCP), heteroduplex analysis (HDA), protein truncation test and direct DNA sequencing. Initial screening of the first 16 BRCA2 exons in 40 HBOC families was performed using SSCP and HDA. To investigate the presence of the CHEK2*1100delC variant, DNA from 65 selected patients was screened by denaturing high-performance liquid chromatography.

Results

To date, we have detected eight previously described mutations (185delAG, C39R, C61G, 962del4, L1013X, 2072del4, 3819del5, 5382insC) and one novel BRCA1 deletion (2057delCAGTGAAGAG) in DNA samples of 16 HBOC families. Initial screening for germline mutations in BRCA2 revealed one recurrent mutation, 6696delTC, in the very large HBOC kindred. Out of 67 asymptomatic relatives from families with the identified BRCA1 or BRCA2 mutations, 31 were found to be mutation carriers. These individuals are included in the Special Program of Preventive Health Care. Mutation analysis has also identified 17 different polymorphisms or unclassified sequence variants scattered through the BRCA1 and BRCA2 genes in 48 patients from the analyzed collection of HBOC families. From these, the most frequent alterations were L771L, E1038G and K1183R, presented in 11, 10 and nine patients, respectively. We have not detected any 1100delC variant of the CHEK2 gene in 65 tested HBOC patients.

Conclusion

In order to identify patients and families predisposed to hereditary breast and ovarian cancer, we searched for germline mutations in two major breast and ovarian cancer susceptibility genes, BRCA1 and BRCA2. Screening of the whole coding sequence of the BRCA1 gene and the first 16 exons of BRCA2 in selected families has identified the spectrum of mutations previously reported in HBOC families of different ethnic or geographic origin. In addition, we found the novel BRCA1 mutation 2057del10, detected in a very high-risk family characterized by different types of cancer (breast and ovarian cancer, male breast cancer, lung cancer, colorectal cancer and testicular cancer). The first results from a small collection of 65 patients did not confirm the correlation between the CHEK2*1100delC variant and breast cancer in these cases, according to the fact that none of the tested DNA was found to be positive. Although the screening of BRCA2 gene needs to be completed, the achieved results represent the first molecular characterization of Slovak HBOC families.