Osgood Christy L, Tantawy Mohammed N, Maloney Nichole, Madaj Zachary B, Peck Anderson, Boguslawski Elissa, Jess Jennifer, Buck Jason, Winn Mary E, Manning H Charles, Grohar Patrick J
Division of Pediatric Hematology/Oncology, Vanderbilt University School of Medicine, Nashville, TN, USA.
Vanderbilt University Institute of Imaging Science, USA.
Sci Rep. 2016 Sep 27;6:33926. doi: 10.1038/srep33926.
Ewing sarcoma is a bone and soft-tissue tumor that depends on the activity of the EWS-FLI1 transcription factor for cell survival. Although a number of compounds have been shown to inhibit EWS-FLI1 in vitro, a clinical EWS-FLI1-directed therapy has not been achieved. One problem plaguing drug development efforts is the lack of a suitable, non-invasive, pharmacodynamic marker of EWS-FLI1 activity. Here we show that F-FLT PET (F- 3'-deoxy-3'-fluorothymidine positron emission tomography) reflects EWS-FLI1 activity in Ewing sarcoma cells both in vitro and in vivo. F-FLT is transported into the cell by ENT1 and ENT2, where it is phosphorylated by TK1 and trapped intracellularly. In this report, we show that silencing of EWS-FLI1 with either siRNA or small-molecule EWS-FLI1 inhibitors suppressed the expression of ENT1, ENT2, and TK1 and thus decreased F-FLT PET activity. This effect was not through a generalized loss in viability or metabolic suppression, as there was no suppression of F-FDG PET activity and no suppression with chemotherapy. These results provide the basis for the clinical translation of F-FLT as a companion biomarker of EWS-FLI1 activity and a novel diagnostic imaging approach for Ewing sarcoma.
尤因肉瘤是一种骨和软组织肿瘤，其细胞存活依赖于EWS-FLI1转录因子的活性。尽管已有多种化合物在体外显示出可抑制EWS-FLI1，但尚未实现针对EWS-FLI1的临床治疗。困扰药物研发工作的一个问题是缺乏合适的、非侵入性的EWS-FLI1活性药效学标志物。在此，我们表明F-FLT PET（F-3'-脱氧-3'-氟胸苷正电子发射断层扫描）在体外和体内均能反映尤因肉瘤细胞中的EWS-FLI1活性。F-FLT通过ENT1和ENT2转运进入细胞，在细胞内被TK1磷酸化并滞留。在本报告中，我们表明用siRNA或小分子EWS-FLI1抑制剂沉默EWS-FLI1可抑制ENT1、ENT2和TK1的表达，从而降低F-FLT PET活性。这种效应并非通过普遍的活力丧失或代谢抑制，因为F-FDG PET活性未受抑制，化疗也未产生抑制作用。这些结果为F-FLT作为EWS-FLI1活性的伴随生物标志物进行临床转化以及作为尤因肉瘤的一种新型诊断成像方法提供了依据。
