title: Tetrahydrouridine inhibits cell proliferation through cell cycle regulation regardless of cytidine deaminase expression levels.
abstract: Tetrahydrouridine (THU) is a well characterized and potent inhibitor of cytidine deaminase (CDA). Highly expressed CDA catalyzes and inactivates cytidine analogues, ultimately contributing to increased gemcitabine resistance. Therefore, a combination therapy of THU and gemcitabine is considered to be a potential and promising treatment for tumors with highly expressed CDA. In this study, we found that THU has an alternative mechanism for inhibiting cell growth which is independent of CDA expression. Three different carcinoma cell lines (MIAPaCa-2, H441, and H1299) exhibited decreased cell proliferation after sole administration of THU, while being unaffected by knocking down CDA. To investigate the mechanism of THU-induced cell growth inhibition, cell cycle analysis using flow cytometry was performed. This analysis revealed that THU caused an increased rate of G1-phase occurrence while S-phase occurrence was diminished. Similarly, Ki-67 staining further supported that THU reduces cell proliferation. We also found that THU regulates cell cycle progression at the G1/S checkpoint by suppressing E2F1. As a result, a combination regimen of THU and gemcitabine might be a more effective therapy than previously believed for pancreatic carcinoma since THU works as a CDA inhibitor, as well as an inhibitor of cell growth in some types of pancreatic carcinoma cells.
authors.affiliation: Department of Molecular Cell Biology, Institute of DNA Medicine, The Jikei University School of Medicine, Tokyo, Japan. funamizujikei@yahoo.co.jp
authors.forename: Naotake
authors.initials: N
authors.lastname: Funamizu
authors.forename: Curtis Ray
authors.initials: CR
authors.lastname: Lacy
authors.forename: Kaori
authors.initials: K
authors.lastname: Fujita
authors.forename: Kenei
authors.initials: K
authors.lastname: Furukawa
authors.forename: Takeyuki
authors.initials: T
authors.lastname: Misawa
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Yanaga
authors.forename: Yoshinobu
authors.initials: Y
authors.lastname: Manome
mesh_terms: D059447:Cell Cycle Checkpoints / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects*; D003564:Cytidine Deaminase / Q000037:antagonists & inhibitors* / Q000096:biosynthesis; D003841:Deoxycytidine / Q000008:administration & dosage / Q000031:analogs & derivatives; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy; D010190:Pancreatic Neoplasms / Q000188:drug therapy; D013767:Tetrahydrouridine / Q000008:administration & dosage / Q000494:pharmacology*; D000093542:Gemcitabine
chemical_list: D004791:Enzyme Inhibitors; D003841:Deoxycytidine; D013767:Tetrahydrouridine; D003564:Cytidine Deaminase; D000093542:Gemcitabine