RB loss sensitizes cells to replication-associated DNA damage after PARP inhibition by trapping

Area of Science:

• Molecular Biology
• Cancer Biology
• Epigenetics

Background:

• The retinoblastoma tumor suppressor protein (RB) is crucial for maintaining genome stability through interactions with epigenetic modifiers.
• Disruption of RB function is implicated in various cancers, affecting transcriptional regulation, DNA repair, and genome integrity.

Purpose of the Study:

• To investigate how RB loss impacts epigenetic regulation and genome stability.
• To identify epigenetic vulnerabilities in RB-deficient cancer cells that can be therapeutically exploited.

Main Methods:

• An imaging-based screen was employed to identify epigenetic inhibitors affecting RB-deficient cells.
• Poly(ADP-ribose)ylation (PARylation) levels and poly(ADP-ribose) polymerase (PARP) trapping were assessed.
• Cell viability and DNA damage were measured in response to RB status and PARP inhibition.

Main Results:

• RB-deficient cells exhibit elevated replication-dependent PARylation.
• Inhibiting PARylation by trapping PARP enzymes on chromatin leads to unresolved replication stress and mitotic defects in RB-deficient cells.
• This sensitivity to PARP inhibitors is conserved and reversed by RB re-expression.

Conclusions:

• RB loss creates a dependency on PARylation, making RB-deficient cells vulnerable to PARP inhibitors.
• Targeting PARP1 and PARP2 represents a potential therapeutic strategy for RB-deficient cancers.