title: The novel thymidylate synthase inhibitor trifluorothymidine (TFT) and TRAIL synergistically eradicate non-small cell lung cancer cells.
abstract: OBJECTIVE
  TRAIL, a tumor selective anticancer agent, may be used for the treatment of non-small cell lung cancer (NSCLC). However, TRAIL resistance is frequently encountered. Here, the combined use of TRAIL with trifluorothymidine (TFT), a thymidylate synthase inhibitor, was examined for sensitizing NSCLC cells to TRAIL.
  
  
  METHODS
  Interactions between TRAIL and TFT were studied in NSCLC cells using growth inhibition and apoptosis assays. Western blotting and flow cytometry were used to investigate underlying mechanisms.
  
  
  RESULTS
  The combined treatment of TFT and TRAIL showed synergistic cytotoxicity in A549, H292, H322 and H460 cells. For synergistic activity, the sequence of administration was important; TFT treatment followed by TRAIL exposure did not show sensitization. Combined TFT and TRAIL treatment for 24 h followed by 48 h of TFT alone was synergistic in all cell lines, with combination index values below 0.9. The treatments affected cell cycle progression, with TRAIL inducing a G1 arrest and TFT, a G2/M arrest. TFT activated Chk2 and reduced Cdc25c levels known to cause G2/M arrest. TRAIL-induced caspase-dependent apoptosis was enhanced by TFT, whereas TFT alone mainly induced caspase-independent death. TFT increased the expression of p53 and p21/WAF1, and p53 was involved in the increase of TRAIL-R2 surface expression. TFT also caused downregulation of cFLIP and XIAP and increased Bax expression.
  
  
  CONCLUSIONS
  TFT enhances TRAIL-induced apoptosis in NSCLC cells by sensitizing the apoptotic machinery at different levels in the TRAIL pathway. Our findings suggest a possible therapeutic benefit of the combined use of TFT and TRAIL in NSCLC.
authors.affiliation: Department of Medical Oncology, University Medical Center Groningen, University of Groningen, Hanzeplein 1, 9713 GZ, Groningen, The Netherlands.
authors.forename: Kaamar
authors.initials: K
authors.lastname: Azijli
authors.forename: Ingrid A M
authors.initials: IA
authors.lastname: van Roosmalen
authors.forename: Jorn
authors.initials: J
authors.lastname: Smit
authors.forename: Saravanan
authors.initials: S
authors.lastname: Pillai
authors.forename: Masakazu
authors.initials: M
authors.lastname: Fukushima
authors.forename: Steven
authors.initials: S
authors.lastname: de Jong
authors.forename: Godefridus J
authors.initials: GJ
authors.lastname: Peters
authors.forename: Irene V
authors.initials: IV
authors.lastname: Bijnsdorp
authors.forename: Frank A E
authors.initials: FA
authors.lastname: Kruyt
mesh_terms: D000963:Antimetabolites / Q000008:administration & dosage / Q000494:pharmacology; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D002289:Carcinoma, Non-Small-Cell Lung / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D020169:Caspases / Q000378:metabolism; D002401:Cathepsin B / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects; D016923:Cell Death / Q000187:drug effects; D045744:Cell Line, Tumor; D004357:Drug Synergism; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000008:administration & dosage / Q000494:pharmacology*; D013940:Thymidylate Synthase / Q000037:antagonists & inhibitors; D014271:Trifluridine / Q000008:administration & dosage / Q000494:pharmacology*
chemical_list: D000963:Antimetabolites; D034741:RNA, Small Interfering; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D013940:Thymidylate Synthase; D020169:Caspases; D002401:Cathepsin B; D014271:Trifluridine