title: Expression of kinase suppressor of Ras1 enhances cisplatin-induced extracellular signal-regulated kinase activation and cisplatin sensitivity.
abstract: Kinase suppressor of Ras1 (KSR1) interacts with several mitogen-activated protein (MAP) kinase pathway components, including Raf, MAP/extracellular signal-regulated kinase (ERK) kinase (MEK), and ERK, and acts as a positive regulator of the Ras signaling cascade. Previous studies have shown that exposure of cells to the anticancer agent cisplatin (cis-diamminedichloroplatinum, CDDP) is associated with changes in multiple signal transduction pathways, including c-Jun-NH2-kinase, ERK, and p38 pathways. Moreover, ERK activation has been linked to changes in cell survival following CDDP treatment. In this report, we have examined the effects of KSR1 expression on the sensitivity of cells to CDDP-induced apoptosis. Loss of KSR1 expression in mouse embryo fibroblasts (MEFs) derived from KSR1 knockout mice (KSR-/- MEF) is associated with decreased CDDP-induced ERK activation and increased resistance to CDDP-induced apoptosis compared with wild-type MEFs (KSR+/+ MEF). Furthermore, transduction of KSR-/- MEFs and MCF-7 breast cancer cells with wild-type KSR1 resulted in enhanced ERK activation following CDDP exposure and increased sensitivity to CDDP. In addition, inhibition of ERK activation by exposing MEFs to the MEK1/2-specific inhibitors PD98059 and U0126 protected both KSR+/+ and KSR-/- MEFs cells from CDDP-induced apoptosis. These results indicate that KSR1-mediated regulation of ERK activity represents a novel determinant of CDDP sensitivity of cancer cells.
authors.affiliation: Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, Nebraska 68198-6805, USA.
authors.forename: Min
authors.initials: M
authors.lastname: Kim
authors.forename: Ying
authors.initials: Y
authors.lastname: Yan
authors.forename: Robert L
authors.initials: RL
authors.lastname: Kortum
authors.forename: Scott M
authors.initials: SM
authors.lastname: Stoeger
authors.forename: Magdalene K
authors.initials: MK
authors.lastname: Sgagias
authors.forename: Kwangmoon
authors.initials: K
authors.lastname: Lee
authors.forename: Robert E
authors.initials: RE
authors.lastname: Lewis
authors.forename: Kenneth H
authors.initials: KH
authors.lastname: Cowan
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001943:Breast Neoplasms / Q000188:drug therapy / Q000201:enzymology / Q000473:pathology; D045744:Cell Line, Tumor; D002945:Cisplatin / Q000494:pharmacology*; D004354:Drug Screening Assays, Antitumor; D004622:Embryo, Mammalian; D004789:Enzyme Activation / Q000187:drug effects; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D006801:Humans; D020935:MAP Kinase Signaling System / Q000187:drug effects; D051379:Mice; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011494:Protein Kinases / Q000096:biosynthesis* / Q000172:deficiency / Q000235:genetics
chemical_list: D011494:Protein Kinases; C097199:KSR-1 protein kinase; D020929:Mitogen-Activated Protein Kinase Kinases; D002945:Cisplatin