An effective epigenetic-PARP inhibitor combination therapy for breast and ovarian cancers independent of BRCA mutations

Nicholas Pulliam, Fang Fang, Ali R. Ozes, Jessica Tang, Adeoluwa Adewuyi, Harold Keer, John Lyons, Stephen B. Baylin, Daniela Matei, Harikrishna Nakshatri, Feyruz V. Rassool, Kathy D. Miller, Kenneth P. Nephew*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

77 Scopus citations


Purpose: PARP inhibitors (PARPi) are primarily effective against BRCA1/2-mutated breast and ovarian cancers, but resistance due to reversion of mutated BRCA1/2 and other mechanisms is common. Based on previous reports demonstrating a functional role for DNMT1 in DNA repair and our previous studies demonstrating an ability of DNA methyltransferase inhibitor (DNMTi) to resensitize tumors to primary therapies, we hypothesized that combining a DNMTi with PARPi would sensitize PARPi-resistant breast and ovarian cancers to PARPi therapy, independent of BRCA status. Experimental Design: Breast and ovarian cancer cell lines (BRCA-wild-type/mutant) were treated with PARPi talazoparib and DNMTi guadecitabine. Effects on cell survival, ROS accumulation, and cAMP levels were examined. In vivo, mice bearing either BRCA-proficient breast or ovarian cancer cells were treated with talazoparib and guadecitabine, alone or in combination. Tumor progression, gene expression, and overall survival were analyzed. Results: Combination of guadecitabine and talazoparib syner-gized to enhance PARPi efficacy, irrespective of BRCA mutation status. Coadministration of guadecitabine with talazoparib increased accumulation of ROS, promoted PARP activation, and further sensitized, in a cAMP/PKA-dependent manner, breast and ovarian cancer cells to PARPi. In addition, DNMTi enhanced PARP "trapping" by talazoparib. Guadecitabine plus talazoparib decreased xenograft tumor growth and increased overall survival in BRCA-proficient high-grade serous ovarian and triple-negative breast cancer models. Conclusions: The novel combination of the next-generation DNMTi guadecitabine and the first-in-class PARPi talazoparib inhibited breast and ovarian cancers harboring either wild-type– or mutant-BRCA, supporting further clinical exploration of this drug combination in PARPi-resistant cancers.

Original languageEnglish (US)
Pages (from-to)3163-3175
Number of pages13
JournalClinical Cancer Research
Issue number13
StatePublished - Jul 1 2018

ASJC Scopus subject areas

  • Oncology
  • Cancer Research


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