title: Ras inhibits endoplasmic reticulum stress in human cancer cells with amplified Myc.
abstract: In neuroblastoma LAN-1 cells harboring an amplified MycN gene, disruption of cooperation between Ras and MycN proteins by the Ras inhibitor farnesylthiosalicylic acid (FTS, Salirasib) reportedly arrests cell growth. Our aim was to establish whether this is a general phenomenon. We examined the effects of FTS on gene-expression profiles, growth and death of NCIH929 myeloma cells and K562 leukemia cells, which-like LAN-1 cells-exhibit Myc gene amplification and harbor active Ras. Under specified conditions, FTS reduced Ras and Myc and induced cell growth arrest and death in all Myc-amplified cell lines but not in SHEP, a neuroblastoma cell line without Myc gene amplification. Gene-expression analysis revealed a common pattern of FTS-induced endoplasmic reticulum (ER) stress, known as the unfolded protein response (UPR), in Myc-amplified cells, but not in SHEP. Thus, Ras negatively regulates ER stress in cells with amplified Myc. ER stress was also inducible by dominant-negative (DN)-Ras or shRNA to Ras isoforms, all of which induced an increase in BIP (the master regulator of ER stress) and its downstream targets Nrf2 and eIF2alpha, both regulated by active p-PERK. FTS also induced an increase in p-PERK, while small interfering RNA to PERK reduced Nrf2 and ATF4 and rescued cells from FTS-induced death. BIP and its downstream targets were also increased by inhibitors of MAPK p38 and MEK. Ras, acting through MAPK p38 and MEK, negatively regulates the ER stress cascades BIP/PERK/Nrf2 and eIF2alpha/ATF4/ATF3. These findings can explain the Ras-dependent protection of Myc-amplified cells from ER stress-associated death.
authors.affiliation: Department of Neurobiology, The George S. Wise Faculty of Life Sciences, Tel-Aviv University, Tel-Aviv, Israel.
authors.forename: Shira
authors.initials: S
authors.lastname: Yaari-Stark
authors.forename: Maayan
authors.initials: M
authors.lastname: Shaked
authors.forename: Yael
authors.initials: Y
authors.lastname: Nevo-Caspi
authors.forename: Jasmine
authors.initials: J
authors.lastname: Jacob-Hircsh
authors.forename: Ron
authors.initials: R
authors.lastname: Shamir
authors.forename: Gideon
authors.initials: G
authors.lastname: Rechavi
authors.forename: Yoel
authors.initials: Y
authors.lastname: Kloog
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D004721:Endoplasmic Reticulum / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005204:Farnesol / Q000031:analogs & derivatives* / Q000494:pharmacology; D005784:Gene Amplification; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D020014:K562 Cells; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D000071447:N-Myc Proto-Oncogene Protein; D051267:NF-E2-Related Factor 2 / Q000378:metabolism; D009447:Neuroblastoma; D009687:Nuclear Proteins / Q000235:genetics*; D015513:Oncogene Proteins / Q000235:genetics*; D034741:RNA, Small Interfering / Q000378:metabolism; D012459:Salicylates / Q000494:pharmacology*; D014157:Transcription Factors / Q000378:metabolism; D056811:Unfolded Protein Response / Q000187:drug effects / Q000235:genetics; D019892:eIF-2 Kinase / Q000378:metabolism; D018631:ras Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D000970:Antineoplastic Agents; D004791:Enzyme Inhibitors; D005204:Farnesol; D020929:Mitogen-Activated Protein Kinase Kinases; D000071447:N-Myc Proto-Oncogene Protein; D051267:NF-E2-Related Factor 2; D009687:Nuclear Proteins; D015513:Oncogene Proteins; D034741:RNA, Small Interfering; D012459:Salicylates; D014157:Transcription Factors; D019892:eIF-2 Kinase; D018631:ras Proteins; C459801:MYCN protein, human; C495635:NFE2L2 protein, human; C093323:farnesylthiosalicylic acid; C101003:ELF2 protein, human