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PARP1 is activated at telomeres upon G4 stabilization: possible target for telomere-based therapy

E Salvati1, M Scarsella, M Porru

  • 1Experimental Chemotherapy Laboratory, Regina Elena Cancer Institute, Rome, Italy.

Oncogene
|August 31, 2010
PubMed

Insights

New cancer therapies target telomeres by stabilizing G-quadruplex DNA with RHPS4, activating PARP1. Inhibiting PARP1 or combining with TOPO1 inhibitors halts tumor growth and improves survival.

Area of Science:

  • Oncology
  • Molecular Biology
  • Genetics

Background:

  • Telomere maintenance is crucial for cancer cell proliferation.
  • Targeting telomeres offers a strategy for selective cancer therapy.
  • G-quadruplex DNA stabilizers are emerging as anti-cancer agents.

Purpose of the Study:

  • To investigate the mechanism of action of RHPS4, a G-quadruplex stabilizer.
  • To explore the role of poly-adenosine diphosphate (ADP) ribose polymerase I (PARP1) in response to telomere uncapping.
  • To evaluate combination therapies involving PARP1 inhibition and TOPO1 inhibition for cancer treatment.

Main Methods:

  • Pharmacological stabilization of telomeric G-quadruplex DNA using RHPS4.
  • Assessment of PARP1 recruitment and activation at telomeres.
  • Inhibition of PARP1 using selective inhibitors and small interfering RNAs (siRNAs).
  • Evaluation of DNA damage, chromosome abnormalities, and tumor cell growth inhibition in vitro and in vivo (xenografts).
  • Combination therapy with a topoisomerase 1 (TOPO1) inhibitor.

Main Results:

  • RHPS4-induced telomere uncapping recruits and activates PARP1, leading to ADP-ribose polymer formation.
  • PARP1 knockdown prevents repair of RHPS4-induced telomere breaks, causing chromosome abnormalities and inhibiting tumor growth.
  • Combination therapy with a TOPO1 inhibitor resulted in complete tumor regression, increased survival, and cure in mice.
  • Treatment demonstrated efficacy even when initiated late in tumor progression.

Conclusions:

  • Uncapped telomeres trigger a PARP1-dependent DNA damage response.
  • PARP1 inhibition is a viable strategy to enhance telomere-based cancer therapy.
  • A multi-component approach combining G-quadruplex ligands, PARP inhibitors, and TOPO1 inhibitors shows significant therapeutic potential.

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