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Updated: Sep 19, 2025
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Assessment of Global DNA Double-Strand End Resection using BrdU-DNA Labeling coupled with Cell Cycle Discrimination Imaging
Published on: April 28, 2021
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BRCA2 reversion mutation-independent resistance to PARP inhibition through impaired DNA prereplication complex
Kyrie Pappas1, Matteo Ferrari2, Perianne Smith3
1Human Oncology and Pathogenesis Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065.
Summary
Poly(ADP-ribose) polymerase inhibitors (PARPi) resistance in prostate cancer is linked to the DNA prereplication complex. Targeting this complex may restore PARPi sensitivity in BRCA-mutant tumors.
Area of Science:
- Oncology
- Molecular Biology
- Genetics
Background:
- Polymeric adenosine diphosphate ribose (poly(ADP-ribose) polymerase inhibitors (PARPi) are approved for BRCA-mutant metastatic castration-resistant prostate cancer.
- Understanding PARPi resistance mechanisms, including upfront resistance and relapse due to reversion mutations, is crucial.
- The role of the DNA prereplication complex (pre-RC) in PARPi sensitivity remains unclear.
Purpose of the Study:
- To identify genomic factors conferring PARPi resistance in BRCA-mutant prostate cancer, independent of reversion mutations.
- To elucidate the mechanistic link between the pre-RC and PARPi sensitivity.
- To explore therapeutic strategies for overcoming PARPi resistance.
Main Methods:
- Genome-wide CRISPR screen in murine Brca2-mutant prostate organoids.
- Genetic manipulation of pre-RC components (Cdt1, Cdc6, Dbf4) and geminin.
- Assessment of sensitivity to olaparib and AZD5305.
- Analysis of DNA damage resolution and replication fork stability.
- Evaluation of pre-RC gene copy number alterations in human CRPC tumors.
Main Results:
- Depletion of pre-RC components (Cdt1, Cdc6, Dbf4) conferred resistance to PARPi (olaparib, AZD5305).
- Knockdown of geminin restored PARPi sensitivity in Brca2-mutant, Cdc6-depleted cells.
- ~50% of castration-resistant prostate cancer (CRPC) tumors show copy number loss in pre-RC genes, particularly CDT1.
- Impaired pre-RC activity led to faster resolution of DNA damage and protected replication forks.
- A CDT1/geminin inhibitor (AF615) restored sensitivity to AZD5305.
Conclusions:
- The DNA prereplication complex is a critical determinant of PARPi sensitivity in BRCA-mutant prostate cancer.
- Impaired pre-RC function allows cancer cells to evade replication stress induced by PARPi.
- Targeting the CDT1/geminin complex offers a potential strategy to re-sensitize tumors to PARPi therapy.
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