title: ERK1/2 signaling plays an important role in topoisomerase II poison-induced G2/M checkpoint activation.
abstract: Topo II poisons, which target topoisomerase II (topo II) to generate enzyme mediated DNA damage, have been commonly used for anti-cancer treatment. While clinical evidence demonstrate a capability of topo II poisons in inducing apoptosis in cancer cells, accumulating evidence also show that topo II poison treatment frequently results in cell cycle arrest in cancer cells, which was associated with subsequent resistance to these treatments. Results in this report indicate that treatment of MCF-7 and T47D breast cancer cells with topo II poisons resulted in an increased phosphorylation of extracellular signal-regulated kinase 1 and 2 (ERK1/2) and an subsequent induction of G2/M cell cycle arrest. Furthermore, inhibition of ERK1/2 activation using specific inhibitors markedly attenuated the topo II poison-induced G2/M arrest and diminished the topo II poison-induced activation of ATR and Chk1 kinases. Moreover, decreased expression of ATR by specific shRNA diminished topo II poison-induced G2/M arrest but had no effect on topo II poison-induced ERK1/2 activation. In contrast, inhibition of ERK1/2 signaling had little, if any, effect on topo II poison-induced ATM activation. In addition, ATM inhibition by either incubation of cells with ATM specific inhibitor or transfection of cells with ATM specific siRNA did not block topo II poison-induced G2/M arrest. Ultimately, inhibition of ERK1/2 signaling greatly enhanced topo II poison-induced apoptosis. These results implicate a critical role for ERK1/2 signaling in the activation of G2/M checkpoint response following topo II poison treatment, which protects cells from topo II poison-induced apoptosis.
authors.affiliation: Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, Nebraska, United States of America.
authors.forename: Ryan H
authors.initials: RH
authors.lastname: Kolb
authors.forename: Patrick M
authors.initials: PM
authors.lastname: Greer
authors.forename: Phu T
authors.initials: PT
authors.lastname: Cao
authors.forename: Kenneth H
authors.initials: KH
authors.lastname: Cowan
authors.forename: Ying
authors.initials: Y
authors.lastname: Yan
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D064007:Ataxia Telangiectasia Mutated Proteins; D018797:Cell Cycle Proteins / Q000378:metabolism; D004249:DNA Damage / Q000187:drug effects*; D004317:Doxorubicin / Q000494:pharmacology; D005047:Etoposide / Q000494:pharmacology; D059565:G2 Phase Cell Cycle Checkpoints / Q000187:drug effects / Q000502:physiology*; D005822:Genetic Vectors / Q000235:genetics; D006801:Humans; D015151:Immunoblotting; D047468:Immunoprecipitation; D007211:Indoles; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology*; D061986:MCF-7 Cells; D010766:Phosphorylation / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D012190:Retroviridae; D059005:Topoisomerase II Inhibitors / Q000494:pharmacology*; D014162:Transfection
chemical_list: D018797:Cell Cycle Proteins; D007211:Indoles; D034741:RNA, Small Interfering; D059005:Topoisomerase II Inhibitors; C007293:DAPI; D005047:Etoposide; D004317:Doxorubicin; C576597:ATR protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases