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Breast Cancer Research and Treatment

, Volume 134, Issue 2, pp 511–517 | Cite as

Inhibition of BRCT(BRCA1)-phosphoprotein interaction enhances the cytotoxic effect of olaparib in breast cancer cells: a proof of concept study for synthetic lethal therapeutic option

  • Ziyan Yuan Pessetto
  • Ying Yan
  • Tadayoshi Bessho
  • Amarnath NatarajanEmail author
Preclinical Study

Abstract

Synthetic lethal therapeutic strategy using poly(adenosine diphosphate [ADP]-ribose) polymerase (PARP) inhibitor olaparib in carriers of BRCA1 or BRCA2 mutation has shown promise in clinical settings. Since <5 % of patients are BRCA1 or BRCA2 mutation carriers, small molecules that functionally mimic BRCA1 or BRCA2 mutations will extend the synthetic lethal therapeutic option for non-mutation carriers. Here we provide proof of principle for this strategy using a BRCA1 inhibitor peptide 2 that targets the BRCT(BRCA1)-phosphoprotein interaction and mimics the M177R/K BRCA1 mutation. Reciprocal immunoprecipitation and immunoblotting of BRCA1 and Abraxas was used to demonstrate inhibitor 2 targets BRCT(BRCA1)-Abraxas interface. Immunostaining of γH2AX, cell cycle analysis and homologous recombination (HR) assays were conducted to confirm that inhibitor 2 functionally mimics a chemosensitizing BRCA1 mutation. The concept of synthetic lethal therapeutic strategy with the BRCA1 inhibitor 2 and the PARP inhibitor Olaparib was explored in HeLa, MDA-MB-231, and HCC1937 cell lines. The results show that inhibition of BRCA1 by 2 sensitizes HeLa and MDA-MB-231 cells but not HCC1937 to Olaparib mediated growth inhibition and apoptosis. These results provide the basis for developing high affinity BRCT(BRCA1) inhibitors as adjuvants to treat sporadic breast and ovarian cancers.

Keywords

Synthetic lethal therapeutic strategy BRCA1 inhibitor Abraxas Chemosensitization Olaparib and IR 

Abbreviations

PARP

Poly(adenosine diphosphate [ADP]-ribose) polymerase

IP

Immunoprecipitation

IB

Immunoblotting

HR

Homologous recombination

IR

Ionizing Radiation

Notes

Acknowledgments

This study was supported by NIH R01CA127239. We thank the UNMC flow cytometry and confocal laser scanning microscopy core facilities.

Conflict of interest

The authors have no conflict of interest.

Supplementary material

10549_2012_2079_MOESM1_ESM.docx (25 kb)
Supplementary material 1 (DOCX 25 kb)

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Copyright information

© Springer Science+Business Media, LLC. 2012

Authors and Affiliations

  • Ziyan Yuan Pessetto
    • 1
  • Ying Yan
    • 1
  • Tadayoshi Bessho
    • 1
  • Amarnath Natarajan
    • 1
    • 2
    • 3
    Email author
  1. 1.Eppley Institute for Cancer ResearchUniversity of Nebraska Medical CenterOmahaUSA
  2. 2.Department of Pharmaceutical SciencesUniversity of Nebraska Medical CenterOmahaUSA
  3. 3.Department of Genetics Cell Biology and AnatomyUniversity of Nebraska Medical CenterOmahaUSA

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