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Small molecule nitroalkenes inhibit RAD51-mediated homologous recombination and amplify triple-negative breast cancer cell killing by DNA-directed therapies
Preprint   Open access

Small molecule nitroalkenes inhibit RAD51-mediated homologous recombination and amplify triple-negative breast cancer cell killing by DNA-directed therapies

Lisa Hong, Dennis C. Braden, Yaoning Zhao, John J. Skoko, Fei Chang, Steven R. Woodcock, Crystall Uvalle, Allison Casey, Katherine Wood, Sonia R. Salvatore, …
bioRxiv
Cold Spring Harbor Laboratory
08/14/2023
DOI: 10.1101/2023.08.11.552990
PMCID: PMC10462009
PMID: 37645906
url
https://doi.org/10.1101/2023.08.11.552990View
Preprint (Author's original)This preprint has not been evaluated by subject experts through peer review. Preprints may undergo extensive changes and/or become peer-reviewed journal articles. Open Access

Abstract

Nitro fatty acids (NO 2 -FAs) are endogenously generated lipid signaling mediators from metabolic and inflammatory reactions between conjugated diene fatty acids and nitric oxide or nitrite-derived reactive species. NO 2 -FAs undergo reversible Michael addition with hyperreactive protein cysteine thiolates to induce posttranslational protein modifications that can impact protein function. Herein, we report a novel mechanism of action of natural and non-natural nitroalkenes structurally similar to ( E ) 10-nitro-octadec-9-enoic acid (CP-6), recently de-risked by preclinical Investigational New Drug-enabling studies and Phase 1 and Phase 2 clinical trials and found to induce DNA damage in a TNBC xenograft by inhibiting homologous-recombination (HR)-mediated repair of DNA double-strand breaks (DSB). CP-6 specifically targets Cys319, essential in RAD51-controlled HR-mediated DNA DSB repair in cells. A nitroalkene library screen identified two structurally different nitroalkenes, a non-natural fatty acid [( E ) 8-nitro- nonadec-7-enoic acid (CP-8)] and a dicarboxylate ester [dimethyl ( E )nitro-oct-4-enedioate (CP- 23)] superior to CP-6 in TNBC cells killing, synergism with three different inhibitors of the poly ADP-ribose polymerase (PARP) and γ-IR. CP-8 and CP-23 effectively inhibited γ-IR-induced RAD51 foci formation and HR in a GFP-reported assay but did not affect benign human epithelial cells or cell cycle phases. In vivo, CP-8 and CP-23’s efficacies diverged as only CP-8 showed promising anticancer activities alone and combined with the PARP inhibitor talazoparib in an HR-proficient TNBC mouse model. As preliminary preclinical toxicology analysis also suggests CP-8 as safe, our data endorse CP-8 as a novel anticancer molecule for treating cancers sensitive to homologous recombination-mediated DNA repair inhibitors.

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