Computationally-designed aptamers targeting RAD51-BRCA2 interaction impair homologous recombination and induce synthetic lethality.

The interaction between RAD51 and BRCA2 plays a key role in homologous recombination (HR), a critical DNA repair mechanism essential for the survival of cancer cells. Disrupting this interaction increases the sensitivity of cancer cells to chemotherapeutic agents. Here, we employed in silico methods to design aptamers-customized single-stranded oligonucleotides-specifically engineered to bind RAD51. These aptamers were developed with the aim of selectively modulating RAD51's nuclear recruitment and its role in DNA repair processes. The leading candidate displays high affinity for RAD51, competing with BRCA2 for the same interaction site in vitro, as confirmed through biolayer interferometry (BLI) and fluorescence lifetime imaging microscopy (FLIM). In pancreatic cancer cells, we show that the aptamer impairs HR by altering the stress-induced nuclear localization of RAD51 and BRCA2, thereby reducing DNA repair efficiency and promoting the accumulation of DNA damage. Notably, when combined with the PARP inhibitor olaparib, the aptamer triggers synthetic lethality (SL) in a dose-dependent manner, an effect that is also preserved in 3D spheroid models. Our study showcases an aptamer-based approach for selectively targeting protein interactions within DNA repair pathways, introducing a promising avenue for SL-based treatments applicable to a wide range of cancers.