Sander Effron Samuel, Makvandi Mehran, Lin Lilie, Xu Kuiying, Li Shihong, Lee Hsiaoju, Hou Catherine, Pryma Daniel A, Koch Cameron, Mach Robert H
1 Division of Nuclear Medicine and Clinical Molecular Imaging, Department of Radiology, University of Pennsylvania Perelman School of Medicine , Philadelphia, Pennsylvania.
2 Department of Radiation Oncology, University of Pennsylvania Perelman School of Medicine , Philadelphia, Pennsylvania.
Cancer Biother Radiopharm. 2017 Feb;32(1):9-15. doi: 10.1089/cbr.2016.2133. Epub 2017 Jan 24.
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 [F]FluorThanatrace ([F]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.
SNU-251 (BRCA1-mutant) and SKOV3 (BRCA1-WT) cell lines were evaluated in vitro by using the radiotracer [F]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.
[F]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.
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.
聚（ADP - 核糖）聚合酶1（PARP - 1）是临床PARP抑制剂的主要靶点，也是治疗反应的潜在预测生物标志物。由于PARP抑制剂作为单一疗法的成效有限，研究人员已将PARP抑制剂的临床作用转向辅助治疗领域。在本研究中，我们评估放射性示踪剂[F]氟塔纳特拉（[F]FTT）作为体外PARP表达的标志物，以及PARP - 1表达在放疗辅助PARP抑制剂治疗中的相关生物学意义。
使用放射性示踪剂[F]FTT在体外评估SNU - 251（BRCA1突变型）和SKOV3（BRCA1野生型）细胞系。在基线时进行药理学结合试验，并与通过蛋白质免疫印迹分析测量的PARP - 1蛋白表达相关联。细胞活力和克隆形成试验用于表征包括以下治疗的体外细胞毒性：单独使用PARP抑制剂、单独使用放疗以及放疗辅助PARP抑制剂。蛋白质免疫印迹分析用于通过使用γH2AX测量DNA损伤和使用PAR测量PARP的催化抑制来评估治疗反应。
[F]FTT能够在体外测量PARP - 1蛋白表达，并且在基线时与蛋白质免疫印迹分析结果相符。添加PARP抑制剂增强了两种细胞系的放疗效果；然而，在表达BRCA1突变和同源重组缺陷的SNU - 251细胞系中观察到了更大的协同作用。蛋白质免疫印迹分析表明，放疗辅助添加PARP抑制剂会增加两种细胞系中的DNA损伤，并降低通过PAR测量的PARP酶活性。
在本研究中，我们发现PARP - 1表达在体外与PARP抑制剂联合放疗治疗卵巢癌的反应呈正相关。
