PO-205 Functional characterisation of BRIP1/FANCJ in tumour suppression and therapy response

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Introduction The helicase BRIP1 is critically required for genomic maintenance, and BRIP1 helicase deficient germline variants are associated with Fanconi Anaemia (bi-allelic) and various cancers (mono-allelic), in particular ovarian and breast cancer. Cellular based assays and biochemical studies have elucidated the function of BRIP1 in replication stress responses, including interaction partners and enzymatic substrate specificity. However, functional characterisation of BRIP1 for these processes in vivo are largely unexplored, including the importance of BRIP1 as a tumour suppressor for breast cancer, and therapy responses. This project aims to elucidate the functional roles of BRIP1 as a tumour suppressor for breast cancer and in therapy responses. Material and methods We have developed breast tissue-specific knockout mice for BRIP1, and will monitor the development of breast tumours. In addition, we have developed mice deficient for BRIP1 helicase activity (K52R) to further investigate the functional role of BRIP1 as a tumour suppressor. In addition, we will use the mouse models for intervention studies, testing known and novel therapies for BRIP1 deficient breast cancer. Moreover, we will investigate BRIP1 germline variants identified in high-risk breast cancer families by large scale sequencing efforts. This comprehensive list of patient derived mutations will be introduced endogenously in a primary epithelial cell line using a CRISPR-CAS9 approach. To monitor the effect on BRIP1 activity, these cell lines will be tested in cancer relevant functional assays for which BRIP1 deficient cells are known to have a phenotype. Results and discussions This project is at an early stage, and we will present our preliminary data from our BRIP1 mouse models, and from our in vitro CRISPR assay for testing BRIP1 gene variants of uncertain significance (VUS). Conclusion This project is expected to yield novel insight into the regulation of critical genomic stability pathways and provide important knowledge for developing improved germ line variant risk prediction and treatment opportunities for patients.