(526d) Mechanistic Characterization of Homologous Recombination in BRCA2 Mutant Cancers

The American Cancer Society estimates that over 40,000 women will die from either breast cancer or ovarian cancer in the United States in 2022 [1]. Mutations in the tumor suppressor genes, BRCA1 and BRCA2, lead to lifetime risks of 50-80% and 30-50% for developing breast and ovarian cancer, respectively [2]. BRCA mutations impair homologous recombination (HR), an important mechanism for repairing double-strand breaks (DSBs) in DNA. Cancer cells with BRCA mutations have deficient levels of the BRCA2 protein, but HR is still achieved through a RAD52-dependent backup pathway. We have developed a novel biochemical assay which detects DNA strand invasion and exchange (key steps in HR), and we plan to use this assay to probe the importance of various nuclear proteins in HR. The assay was designed with dual-labeled complementary oligonucleotides using a fluorophore and a black hole quencher (BHQ). Labeling the oligonucleotides in this way allows us to monitor which oligonucleotides are annealed to one strand or another. We will use this biochemical assay to identify the nuclear proteins that are both sufficient and essential to perform the RAD52-dependent HR pathway. To further verify the importance of the proteins highlighted with these experiments, we will analyze RAD51 focus formation, and how it is affected by small interfering RNA (siRNA) elimination of each candidate protein. The possible implications of this study’s results include the establishment of a potential gold-standard, novel biochemical assay, and the development of new therapeutic strategies for BRCA2-mutant cancers.

References

[1] American Cancer Society, “About Breast Cancer”, [Online]. Available: https://www.cancer.org/content/dam/CRC/PDF/Public/8577.00.pdf

[2] R. Roy, J. Chun, and S. N. Powell, “BRCA1 and BRCA2: different roles in a common pathway of genome protection,” Nature reviews. Cancer, vol. 12, no. 1, p. 68, Jan. 2012, doi: 10.1038/NRC3181.