title: Basis for dosing time-dependent change in the anti-tumor effect of imatinib in mice.
abstract: Because a variety of receptor tyrosine kinases are involved in the mechanism of tumor progression, the development of a clinically useful tyrosine kinase inhibitor is expected as a therapeutic agent for the treatment of malignant cancers. Imatinib mesylate, known as Gleevec or STI-571, is a molecule that inhibits the function of various receptors with tyrosine kinase activity, such as Abl, the bcr-abl chimeric product, KIT, and platelet-derived growth factor (PDGF) receptors. In this study, we investigated the influence of dosing time on the ability of imatinib to inhibit tumor growth in mice. Tumor-bearing mice were housed under standardized light/dark cycle conditions (lights on at 07:00 h, off at 19:00 h) with food and water ad libitum. The growth of tumor cells implanted in mice was more severely inhibited by the administration of imatinib (50 mg/kg, i.p.) in the early light phase than when it was administered in the early dark phase. The dosing time-dependency of anti-tumor effects was parallel to that of imatinib-induced anti-angiogenic effect. The inhibitory effect of imatinib on tyrosine kinase activity of PDGF receptors, but not of KIT and Abl, varied according to its administration time. The dosing time-dependency of imatinib-induced inhibition of PDGF receptor activity was closely related to that of its anti-tumor effects. Our results suggest that the anti-tumor efficacy of imatinib is enhanced by administering the drug when PDGF receptor activity was increased. The potent therapeutic efficacy of the drug could be expected by optimizing the dosing schedule.
authors.affiliation: Pharmaceutics, Division of Clinical Pharmacy, Department of Medico-Pharmaceutical Sciences, Faculty of Pharmaceutical Sciences, Kyushu University, 3-1-1 Maidashi, Fukuoka, Japan.
authors.forename: Hiroo
authors.initials: H
authors.lastname: Nakagawa
authors.forename: Takako
authors.initials: T
authors.lastname: Takiguchi
authors.forename: Mariko
authors.initials: M
authors.lastname: Nakamura
authors.forename: Atsuko
authors.initials: A
authors.lastname: Furuyama
authors.forename: Satoru
authors.initials: S
authors.lastname: Koyanagi
authors.forename: Hironori
authors.initials: H
authors.lastname: Aramaki
authors.forename: Shun
authors.initials: S
authors.lastname: Higuchi
authors.forename: Shigehiro
authors.initials: S
authors.lastname: Ohdo
mesh_terms: D020533:Angiogenesis Inhibitors / Q000008:administration & dosage / Q000627:therapeutic use; D000818:Animals; D001549:Benzamides; D045744:Cell Line, Tumor; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D000068877:Imatinib Mesylate; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D009389:Neovascularization, Pathologic / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D010879:Piperazines / Q000008:administration & dosage / Q000627:therapeutic use; D011743:Pyrimidines / Q000008:administration & dosage / Q000627:therapeutic use; D012510:Sarcoma 180 / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology
chemical_list: D020533:Angiogenesis Inhibitors; D001549:Benzamides; D010879:Piperazines; D011743:Pyrimidines; D000068877:Imatinib Mesylate