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Cancer Biother Radiopharm. 2017 Feb;32(1):9-15. doi: 10.1089/cbr.2016.2133. Epub 2017 Jan 24.

PARP-1 Expression Quantified by [18F]FluorThanatrace: A Biomarker of Response to PARP Inhibition Adjuvant to Radiation Therapy.

Author information

1
1 Division of Nuclear Medicine and Clinical Molecular Imaging, Department of Radiology, University of Pennsylvania Perelman School of Medicine , Philadelphia, Pennsylvania.
2
2 Department of Radiation Oncology, University of Pennsylvania Perelman School of Medicine , Philadelphia, Pennsylvania.

Abstract

INTRODUCTION:

Poly (ADP-ribose) polymerase 1 (PARP-1) is the major target of clinical PARP inhibitors and is a potential predictive biomarker for response to therapy. Due to the limited success of PARP inhibitors as monotherapy, investigators have shifted the clinical role of PARP inhibitors to the adjuvant setting. In this study, we evaluate the radiotracer [18F]FluorThanatrace ([18F]FTT) as a marker of PARP expression in vitro and the associated biological implications of PARP-1 expression in PARP inhibitor treatment adjuvant to radiation therapy.

MATERIALS AND METHODS:

SNU-251 (BRCA1-mutant) and SKOV3 (BRCA1-WT) cell lines were evaluated in vitro by using the radiotracer [18F]FTT. Pharmacological binding assays were performed at baseline and were correlated with PARP-1 protein expression measured by Western blot protein analysis. Cell viability and clonogenic assays were used to characterize in vitro cytotoxicity for treatments, including: PARP inhibitors alone, radiation alone, and PARP inhibitor adjuvant to radiation. Western blot protein analysis was used to assess response to treatment by using γH2AX to measure DNA damage and PAR to measure the catalytic inhibition of PARP.

RESULTS:

[18F]FTT was capable of measuring PARP-1 protein expression in vitro and corresponded to Western blot protein analysis at baseline. The addition of a PARP inhibitor enhanced radiation effects in both cell lines; however, a greater synergy was observed in the SNU-251 cell line that expresses a BRCA1 mutation and homologous recombination deficiency. Western blot protein analysis showed that the addition of a PARP inhibitor adjuvant to radiation increases DNA damage in both cell lines and reduces PARP enzymatic activity as measured by PAR.

CONCLUSIONS:

In this work, we found that PARP-1 expression positively corresponds in vitro to the response of PARP inhibitors in combination with radiation therapy in ovarian cancer.

KEYWORDS:

BRCA1; DNA damage; PARP inhibitor; PARP-1; ovarian cancer

PMID:
28118040
PMCID:
PMC5312613
DOI:
10.1089/cbr.2016.2133
[Indexed for MEDLINE]
Free PMC Article

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