title: The Ras radiation resistance pathway.
abstract: The critical pathways determining the resistance of tumor cells to ionizing radiation are poorly defined. Because the ras oncogene, a gene activated in many human cancers treated with radiotherapy, can induce increased radioresistance, we have asked which Ras effector pathways are significant in conferring a survival advantage to tumor cells. The phosphoinositide-3-kinase (PI3K) inhibitor LY294002 radiosensitized cells bearing mutant ras oncogenes, but the survival of cells with wild-type ras was not affected. Inhibition of the PI3K downstream target p70S6K by rapamycin, the Raf-MEK-MAPK pathway with PD98059, or the Ras-MEK kinase-p38 pathway with SB203580 had no effect on radiation survival in cells with oncogenic ras. Expression of active PI3K in cells with wild-type ras resulted in increased radiation resistance that could be inhibited by LY294002. These experiments have indicated the importance of PI3K in mediating enhanced radioresistance and have implicated PI3K as a potential target for specific radiosensitization of tumors.
authors.affiliation: Department of Radiation Oncology, University of Pennsylvania, 195 John Morgan Building, 3620 Hamilton Walk, Philadelphia, PA 19104, USA.
authors.forename: A K
authors.initials: AK
authors.lastname: Gupta
authors.forename: V J
authors.initials: VJ
authors.lastname: Bakanauskas
authors.forename: G J
authors.initials: GJ
authors.lastname: Cerniglia
authors.forename: Y
authors.initials: Y
authors.lastname: Cheng
authors.forename: E J
authors.initials: EJ
authors.lastname: Bernhard
authors.forename: R J
authors.initials: RJ
authors.lastname: Muschel
authors.forename: W G
authors.initials: WG
authors.lastname: McKenna
mesh_terms: D000818:Animals; D002867:Chromones / Q000494:pharmacology; D004790:Enzyme Induction; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D011905:Genes, ras; D006801:Humans; D020935:MAP Kinase Signaling System / Q000502:physiology*; D009025:Morpholines / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011836:Radiation Tolerance / Q000502:physiology*; D051381:Rats; D014407:Tumor Cells, Cultured; D018631:ras Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*
chemical_list: D002867:Chromones; D004791:Enzyme Inhibitors; D005419:Flavonoids; D009025:Morpholines; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D018631:ras Proteins; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one