Linker region of the BRCA2 protein increases chemoresistance to cisplatin: Screen for the characterization of cancer-associated variants

The BRCA2 (Breast Cancer Type 2, early onset) gene and protein are essential for maintaining genomic integrity. Mutations in this gene can contribute to the onset of breast cancer. BRCA1 and BRCA2 sequencing are a fundamental part of the treatment plan for patients with a family tree indicative of a familial breast cancer syndrome. The Helen F. Graham Cancer Center's Ruth Ann Minner High-Risk Family Registry contains vital data on cancer patients, many of whom carry novel variants in the BRCA2 gene. Most of these variants are classified as "variants of unknown significance" and two of them are located in an uncharacterized linker region of the BRCA2 protein. These variants could possibly change the function of the full-length protein and thus predispose a carrier to cancer. The current study used expression plasmids containing both the wild type sequence and a number of variants of unknown significance found in the Breast Cancer Information Core. These were used in a functional assay for BRCA2 performed on expression-positive clones of the T47D cell line. The functional assay consisted of testing the survival capacity of these clones against that of the untransfected T47D cells when treated with varying concentrations of the DNA crosslinker cisplatin. A potential role for the linker region of the BRCA2 protein in resistance to chemotherapeutics is demonstrated in this work.