title: Effect of a combination of S-1 and gemcitabine on cell cycle regulation in pancreatic cancer cell lines.
abstract: In a previous study, we showed that a combination of an oral fluoropyrimidine anticancer agent (S-1) and gemcitabine (GEM) had synergistic effects on cell growth and cell cycle arrest in the pancreatic cancer cell line MIA PaCa-2. Therefore, we conducted further mechanistic studies using the pancreatic cancer cell lines MIA PaCa-2 and SUIT-2. The combined effect of S-1 and GEM in SUIT-2 cells was evaluated using an 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, and the effects of S-1, GEM and S-1 plus GEM on cell cycle regulation were assessed using flow cytometry. We also examined the expression of several cell cycle regulatory proteins in both MIA PaCa-2 and SUIT-2 cells by western blotting. Classical isobolographic analysis of the MTT assay results showed that the combination of S-1 and GEM had a synergistic effect in SUIT-2 cells, and flow cytometric analysis of the cell cycle showed that the combination of S-1 plus GEM induced S-phase arrest to a greater degree than did either S-1 or GEM alone. Also, the combination of S-1 and GEM resulted in the downregulation of cyclin D1 expression and upregulation of cyclin A, p21 and p27 expression levels. Treatment of MIA PaCa-2 and SUIT-2 cells with a combination of both drugs also led to the increased phosphorylation of checkpoint kinase 1. Combined treatment with S-1 and GEM resulted in more prolonged S-phase arrest than with either treatment alone. This difference is shown to be potentially due to the higher levels of phosphorylated checkpoint kinase 1 in pancreatic cancer cell lines treated with the two agents.
authors.affiliation: Division of Research, BioMedical Laboratory, Kitasato Institute Hospital, Tokyo, Japan.
authors.forename: Yoshihito
authors.initials: Y
authors.lastname: Morimoto
authors.forename: Osamu
authors.initials: O
authors.lastname: Takeuchi
authors.forename: Asako
authors.initials: A
authors.lastname: Takizawa
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Yoneyama
authors.forename: Fumiki
authors.initials: F
authors.lastname: Asanuma
authors.forename: Yukio
authors.initials: Y
authors.lastname: Suzuki
authors.forename: Koichiro
authors.initials: K
authors.lastname: Atsuda
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Yamada
mesh_terms: D000971:Antineoplastic Combined Chemotherapy Protocols / Q000008:administration & dosage / Q000494:pharmacology* / Q000627:therapeutic use; D015153:Blotting, Western; D002453:Cell Cycle / Q000187:drug effects*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D016213:Cyclins / Q000096:biosynthesis; D003841:Deoxycytidine / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000494:pharmacology / Q000627:therapeutic use; D004338:Drug Combinations; D004357:Drug Synergism; D006801:Humans; D008297:Male; D010094:Oxonic Acid / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use; D010190:Pancreatic Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology*; D016196:S Phase / Q000187:drug effects; D005641:Tegafur / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use; D000093542:Gemcitabine
chemical_list: D016213:Cyclins; D004338:Drug Combinations; D003841:Deoxycytidine; C079198:S 1 (combination); D005641:Tegafur; D010094:Oxonic Acid; D000093542:Gemcitabine