Activity of CEP-9722, a poly (ADP-ribose) polymerase inhibitor, in urothelial carcinoma correlates inversely with homologous recombination repair response to DNA damage.
As loss of DNA-repair proteins is common in urothelial carcinoma (UC), a rationale can be made to evaluate the activity of poly (ADP-ribose) polymerase (PARP) inhibitors to exploit synthetic lethality. We aimed to preclinically evaluate a PARP inhibitor, CEP-9722, and its active metabolite, CEP-8983, in UC. The activity of CEP-8983 was evaluated using a 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay against human UC cell lines. Flow cytometry, COMET assay, and western blot were performed to assess apoptosis, DNA damage, and DNA-repair proteins, respectively. RT4 xenografts received placebo or CEP-9722 (100 or 200 mg/kg/day) orally. Xenografts were subjected to immunohistochemistry for apoptosis [cleaved caspase (cc)-3] and angiogenesis (CD31). CEP-8983 (1 μmol/l) reduced the viability of RT4 and T24 cells by 20%, but did not reduce the viability of 5637 and TCC-SUP cells. Apoptosis and necrosis occurred in 9.7 and 9.1% of RT4 and 5637 cells, respectively. RT4 cells showed greater DNA damage compared with 5637 cells. Increased DNA damage occurred with combination versus CEP-8983 or cisplatin alone in RT4 and 5637 cells. T24 and RT4 showed the least RAD51 foci 8 h following radiation, whereas TCC-SUP and 5637 robustly induced RAD51 foci. CEP-9722 showed dose-dependent antitumor activity in RT4 xenografts; 200 mg/kg daily was better than control (P=0.04) and 100 mg/kg was not (P=0.26). Immunohistochemistry of xenografts showed a significant increase in cc-3 and decrease in CD31 with both doses (P<0.05). Biomarker-driven evaluation of PARP inhibitors in UC is justified as the activity of CEP-9722 correlated inversely with homologous recombination repair response to DNA damage.
Departments of aUrology bImmunology, Baylor College of Medicine, Houston, Texas cDepartment of Medicine, Division of Hematology-Oncology dDepartment of Radiation Oncology, University of Alabama, Birmingham (UAB) Comprehensive Cancer Center, Birmingham, Alabama, USA.
Weiguo
W
Jian
Hua-Guo
HG
Xu
Jianfeng
J
Chen
Zhi-Xiang
ZX
Xu
Jonathan M
JM
Levitt
Jennifer A
JA
Stanley
Eddy S
ES
Yang
Seth P
SP
Lerner
Guru
G
Sonpavde
D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D002227:Carbazoles / Q000494:pharmacology*; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D002945:Cisplatin / Q000494:pharmacology; D004249:DNA Damage / Q000187:drug effects*; D019008:Drug Resistance, Neoplasm; D004357:Drug Synergism; D064593:Heterografts; D006801:Humans; D008819:Mice, Nude; D009336:Necrosis; D010797:Phthalimides / Q000494:pharmacology*; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D011355:Prodrugs / Q000494:pharmacology*; D051135:Rad51 Recombinase / Q000235:genetics / Q000378:metabolism; D059767:Recombinational DNA Repair / Q000187:drug effects*; D014571:Urologic Neoplasms / Q000235:genetics / Q000473:pathology*
D000970:Antineoplastic Agents; C523456:CEP 8983; C000597465:CEP-9722; D002227:Carbazoles; D010797:Phthalimides; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D011355:Prodrugs; C495153:RAD51 protein, human; D051135:Rad51 Recombinase; D002945:Cisplatin