title: Novel tubulin-polymerization inhibitor derived from thalidomide directly induces apoptosis in human multiple myeloma cells: possible anti-myeloma mechanism of thalidomide.
abstract: To ascertain the exact anti-myeloma mechanism of thalidomide in vivo, we performed structural development studies of thalidomide, and obtained various analogues with specific molecular properties. Among these derivatives, we found that a new thalidomide analogue, 2-(2,6-diisopropylphenyl)-5-hydroxy-1H-isoindole-1,3-dione (5HPP-33) had the most potent anti-myeloma effect and tubulin-polymerization-inhibiting activity. 5HPP-33 directly inhibited the growth and survival of various myeloma cell lines (RPMI8226, U266, and IM9) in a dose-dependent manner with IC50 of 1-10 microM. In contrast, thalidomide itself did not inhibit cellular growth of RPMI8226 cells. Cultivation with 10 microM 5HPP-33 induced G2/M phase cell cycle arrest, followed by apoptosis of myeloma cells. Treatment with 5HPP-33 induced caspase-3 activity and PARP cleavage. A tubulin polymerization assay using microtubule protein from porcine brain revealed that 5HPP-33 showed potent tubulin-polymerization-inhibiting activity with IC50 of 8.1 microM, comparable to that of the known tubulin-polymerization inhibitor, rhizoxin. Moreover, its activity was more potent than that of a known thalidomide metabolite, 5-hydroxythalidomide. Notably, the structural requirement for its activity was critical, as other analogues and derivatives of 5HPP-33 showed only slight tubulin-polymerization-inhibiting activity. Our data suggest that 5HPP-33 is a promising candidates for a therapeutic agent of multiple myeloma. In addition, these results suggest that the tubulin-polymerization inhibiting activity of thalidomide might be a possible mechanism for inducing the apoptosis of myeloma cells by thalidomide.
authors.affiliation: Division of Hematology, Department of Internal Medicine, Keio University School of Medicine, Tokyo, Japan.
authors.forename: Toyotaka
authors.initials: T
authors.lastname: Iguchi
authors.forename: Tomomi
authors.initials: T
authors.lastname: Yachide-Noguchi
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Hashimoto
authors.forename: Sawako
authors.initials: S
authors.lastname: Nakazato
authors.forename: Morihiko
authors.initials: M
authors.lastname: Sagawa
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Ikeda
authors.forename: Masahiro
authors.initials: M
authors.lastname: Kizaki
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D053148:Caspase 3 / Q000378:metabolism; D002455:Cell Division / Q000187:drug effects; D045744:Cell Line, Tumor; D004354:Drug Screening Assays, Antitumor; D016195:G2 Phase / Q000187:drug effects; D006801:Humans; D054833:Isoindoles / Q000737:chemistry / Q000494:pharmacology*; D009101:Multiple Myeloma / Q000201:enzymology / Q000473:pathology*; D013792:Thalidomide / Q000737:chemistry / Q000494:pharmacology*; D013997:Time Factors; D050257:Tubulin Modulators / Q000737:chemistry / Q000494:pharmacology*
chemical_list: C501339:2-(2,6-diisopropylphenyl)-5-hydroxy-1H-isoindole-1,3-dione; D000970:Antineoplastic Agents; D054833:Isoindoles; D050257:Tubulin Modulators; D013792:Thalidomide; D053148:Caspase 3