title: Blockade of the phosphatidylinositol-3-kinase-Akt signaling pathway enhances the induction of apoptosis by microtubule-destabilizing agents in tumor cells in which the pathway is constitutively activated.
abstract: Constitutive activation of the phosphatidylinositol-3-kinase (PI3K)-Akt signaling pathway is associated with the neoplastic phenotype in many human tumor cell types. Given the antiapoptotic role of this pathway, we examined whether its specific blockade might sensitize human tumor cells to the induction of apoptosis by various anticancer drugs. Although specific blockade of the PI3K-Akt pathway alone with inhibitors such as LY294002 did not induce cell death, it resulted in marked and selective enhancement of the induction of apoptosis by microtubule-destabilizing agents such as vincristine. This effect was apparent only in tumor cells in which the PI3K-Akt pathway is constitutively activated. Blockade of the PI3K-Akt pathway induced the activation of glycogen synthase kinase-3beta, which phosphorylates microtubule-associated proteins such as tau and thereby reduces their ability to bind and stabilize microtubules. The consequent destabilization of microtubules induced by the inhibition of PI3K-Akt signaling appeared to increase their sensitivity to low concentrations of microtubule-destabilizing agents that alone do not lead to the disruption of cytoplasmic microtubules in tumor cells. Such a synergistic effect on microtubule integrity was not apparent for stable microtubules in the neurites of neuronal cells. These results suggest that the administration of a combination of a PI3K-Akt pathway inhibitor and a microtubule-destabilizing agent is a potential chemotherapeutic strategy for the treatment of tumor cells in which this signaling pathway is constitutively activated.
authors.affiliation: Laboratory of Cell Regulation, Department of Pharmaceutical Sciences, Graduate School of Biomedical Sciences, Nagasaki University, 1-14 Bunkyo-machi, Nagasaki 852-8521, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Fujiwara
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Hosokawa
authors.forename: Kazushi
authors.initials: K
authors.lastname: Watanabe
authors.forename: Susumu
authors.initials: S
authors.lastname: Tanimura
authors.forename: Kei-ichi
authors.initials: K
authors.lastname: Ozaki
authors.forename: Michiaki
authors.initials: M
authors.lastname: Kohno
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D002450:Cell Communication; D002454:Cell Differentiation / Q000187:drug effects; D002867:Chromones / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D006801:Humans; D008870:Microtubules / Q000187:drug effects*; D009025:Morpholines / Q000494:pharmacology; D009369:Neoplasms / Q000188:drug therapy* / Q000378:metabolism; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors*; D015398:Signal Transduction / Q000187:drug effects; D014404:Tubulin / Q000378:metabolism; D050257:Tubulin Modulators / Q000494:pharmacology*; D014407:Tumor Cells, Cultured / Q000187:drug effects; D014750:Vincristine / Q000494:pharmacology
chemical_list: D000970:Antineoplastic Agents; D002867:Chromones; D004791:Enzyme Inhibitors; D009025:Morpholines; D000081082:Phosphoinositide-3 Kinase Inhibitors; D014404:Tubulin; D050257:Tubulin Modulators; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D014750:Vincristine; C494918:AKT1 protein, human; D051057:Proto-Oncogene Proteins c-akt