Abstract PR02: Small molecules that specifically inhibit the D-loop activity of RAD51

RAD51 plays a central role in homologous recombination (HR), which maintains genome integrity. RAD51 is commonly overexpressed in cancer cells relative to normal tissue and is considered a therapeutic target in oncology. One potential challenge for targeting RAD51 pharmacologically is that it mediates functions in both double-strand DNA break (DSB) repair and stabilization of stalled replication forks.In order to distinguish compound-mediated effects on these RAD51 functions, we developed a novel class of RAD51 inhibitors. In contrast to many previously reported RAD51 inhibitors, we sought to develop compounds that do not inhibit RAD51's ability to bind single-stranded DNA (ssDNA). Instead, these compounds prevent RAD51-ssDNA nucleoprotein filaments from invading into homologous double-stranded DNA templates and forming D-loops. Our initial lead compound RI(dl)-1 (an abbreviation for RAD51 inhibitor of D-loop formation #1) is capable of blocking RAD51-mediated D-loop formation in biochemical assays, using concentrations that do not prevent RAD51 binding to ssDNA. An analog of this compound, termed RI(dl)-2, provides even better inhibition of RAD51's D-loop activity in biochemical systems (IC50 15.8 µM). RI(dl)-2 reduces HR activity in cells in dose ranges that do not stimulate single strand annealing (SSA) activity, which distinguishes it more generalized RAD51 inhibitors. RI(dl)-2 also sensitizes several cancer cell lines to radiation-induced death.We now present the r...
Source: Molecular Cancer Research - Category: Cancer & Oncology Authors: Tags: Homologous Recombination Defects: Oral Presentations - Proffered Abstracts Source Type: research