BRCA1 and BRCA2 tumor suppressors protect against endogenous acetaldehyde toxicity.

Eliana M.c Tacconi ,Peter Bouwman,Gijs Zonderland,Alejandra Bruna,Manuela Porru,Johanna Michl,Irene Sechi,Madalena Tarsounas,Xianning Lai,Mélanie Rogier,Sophie Badie,Cecilia Folio,Annamaria Biroccio,Joannie Hui,Jos Jonkers,Nelson L.s Tang ,Ankita Sati Batra ,Verónica Matía ,Oscar M Rueda ,Bernardo Reina-San-Martín ,Anderson J Ryan

doi:10.15252/emmm.201607446

Abstract

Maintenance of genome integrity requires the functional interplay between Fanconi anemia (FA) and homologous recombination (HR) repair pathways. Endogenous acetaldehyde, a product of cellular metabolism, is a potent source of DNA damage, particularly toxic to cells and mice lacking the FA protein FANCD2. Here, we investigate whether HR‐compromised cells are sensitive to acetaldehyde, similarly to FANCD2‐deficient cells. We demonstrate that inactivation of HR factors BRCA1, BRCA2, or RAD51 hypersensitizes cells to acetaldehyde treatment, in spite of the FA pathway being functional. Aldehyde dehydrogenases (ALDHs) play key roles in endogenous acetaldehyde detoxification, and their chemical inhibition leads to cellular acetaldehyde accumulation. We find that disulfiram (Antabuse), an ALDH2 inhibitor in widespread clinical use for the treatment of alcoholism, selectively eliminates BRCA1/2‐deficient cells. Consistently, Aldh2 gene inactivation suppresses proliferation of HR‐deficient mouse embryonic fibroblasts (MEFs) and human fibroblasts. Hypersensitivity of cells lacking BRCA2 to acetaldehyde stems from accumulation of toxic replication‐associated DNA damage, leading to checkpoint activation, G2/M arrest, and cell death. Acetaldehyde‐arrested replication forks require BRCA2 and FANCD2 for protection against MRE11‐dependent degradation. Importantly, acetaldehyde specifically inhibits in vivo the growth of BRCA1/2‐deficient tumors and ex vivo in patient‐derived tumor xenograft cells (PDTCs), including those that are resistant to poly (ADP‐ribose) polymerase (PARP) inhibitors. The work presented here therefore identifies acetaldehyde metabolism as a potential therapeutic target for the selective elimination of BRCA1/2‐deficient cells and tumors.

Highlights

BRCA1 and BRCA2 germ line mutations increase breast and ovarian cancer susceptibility in heterozygous carriers (Roy et al, 2012)
Acetaldehyde caused a significant reduction in survival of DLD1 cells lacking BRCA2 using clonogenic assays, in which olaparib and cisplatin were used as controls (Appendix Fig S1A–C)
Recent work reported that mice deficient in both Fanconi anemia (FA) DNA repair pathway (Fancd2À/À) and acetaldehyde catabolism (Aldh2À/À) showed developmental aberrations upon exposure to ethanol and increased leukemia occurrence (Langevin et al, 2011)

Summary

Introduction

BRCA1 and BRCA2 germ line mutations increase breast and ovarian cancer susceptibility in heterozygous carriers (Roy et al, 2012). In response to DNA damage induced by exogenous agents (e.g., ionizing radiation), they initiate HR reactions for double-strand break (DSB) repair and in response to replication stress they act to protect and restart replication forks stalled at sites of DNA damage. In both settings, BRCA1 and BRCA2 promote loading of RAD51 recombinase onto single-stranded DNA generated at DSBs and stalled replication forks. ICLs represent one of the most deleterious types of DNA damage, known to obstruct both

Methods

Results

Conclusion