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Persistent double strand break accumulation does not precede cell death in an Olaparib-sensitive BRCA-deficient

Natalia Soledad Paviolo1, María Belén de la Vega1, María Florencia Pansa2,3

  • 1Fundación Instituto Leloir-Instituto de Investigaciones Bioquímicas de Buenos Aires. Buenos Aires, Argentina.

Genetics and Molecular Biology
|January 14, 2020
PubMed

Insights

Poly (ADP)-ribosyl) polymerase inhibitors (PARPi) kill BRCA-mutated cancer cells. In BRCA-deficient cells, PARPi-induced cell death is not caused by unrepaired double-strand breaks, but by aberrant DSB resolution leading to chromosome aberrations.

Area of Science:

  • Molecular Biology
  • Genetics
  • Cancer Research

Background:

  • Poly (ADP)-ribosyl) polymerase inhibitors (PARPi) are effective against cancers with BRCA1/BRCA2 mutations.
  • PARPi efficacy is thought to stem from unrepaired DNA double-strand breaks (DSBs) in homologous recombination-deficient cells.

Purpose of the Study:

  • To investigate the precise mechanism of cell death induction by PARPi in BRCA-deficient cells.
  • To determine if persistent DSB accumulation is the primary driver of PARPi-mediated cell death.

Main Methods:

  • Development of an isogenic cell line model for BRCA depletion.
  • Assessment of PARPi treatment effects on cell death, replication stress markers (phosphorylated-H2AX, 53BP1 foci), and genomic instability.
  • Analysis of DSB accumulation and resolution pathways.

Main Results:

  • BRCA depletion induced PARPi-triggered cell death, replication stress, and genomic instability.
  • Persistent DSB accumulation was not observed in PARPi-treated BRCA-depleted cells.
  • Cell death correlated with rapid, aberrant DSB resolution via error-prone pathways, causing chromosomal aberrations.

Conclusions:

  • In this model, PARPi-induced cell death in BRCA-deficient cells is not driven by unrepaired DSBs.
  • Aberrant DSB resolution and subsequent chromosome aberrations appear to be key triggers for genomic instability and cell death.

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