title: RAS transformation requires CUX1-dependent repair of oxidative DNA damage.
abstract: The Cut homeobox 1 (CUX1) gene is a target of loss-of-heterozygosity in many cancers, yet elevated CUX1 expression is frequently observed and is associated with shorter disease-free survival. The dual role of CUX1 in cancer is illustrated by the fact that most cell lines with CUX1 LOH display amplification of the remaining allele, suggesting that decreased CUX1 expression facilitates tumor development while increased CUX1 expression is needed in tumorigenic cells. Indeed, CUX1 was found in a genome-wide RNAi screen to identify synthetic lethal interactions with oncogenic RAS. Here we show that CUX1 functions in base excision repair as an ancillary factor for the 8-oxoG-DNA glycosylase, OGG1. Single cell gel electrophoresis (comet assay) reveals that Cux1⁺/⁻ MEFs are haploinsufficient for the repair of oxidative DNA damage, whereas elevated CUX1 levels accelerate DNA repair. In vitro base excision repair assays with purified components demonstrate that CUX1 directly stimulates OGG1's enzymatic activity. Elevated reactive oxygen species (ROS) levels in cells with sustained RAS pathway activation can cause cellular senescence. We show that elevated expression of either CUX1 or OGG1 prevents RAS-induced senescence in primary cells, and that CUX1 knockdown is synthetic lethal with oncogenic RAS in human cancer cells. Elevated CUX1 expression in a transgenic mouse model enables the emergence of mammary tumors with spontaneous activating Kras mutations. We confirmed cooperation between Kras(G12V) and CUX1 in a lung tumor model. Cancer cells can overcome the antiproliferative effects of excessive DNA damage by inactivating a DNA damage response pathway such as ATM or p53 signaling. Our findings reveal an alternate mechanism to allow sustained proliferation in RAS-transformed cells through increased DNA base excision repair capability. The heightened dependency of RAS-transformed cells on base excision repair may provide a therapeutic window that could be exploited with drugs that specifically target this pathway.
authors.affiliation: Goodman Cancer Centre, McGill University, Montreal, Quebec, Canada.
authors.forename: Zubaidah M
authors.initials: ZM
authors.lastname: Ramdzan
authors.affiliation: Goodman Cancer Centre, McGill University, Montreal, Quebec, Canada; Department of Biochemistry, McGill University, Montreal, Quebec, Canada.
authors.forename: Charles
authors.initials: C
authors.lastname: Vadnais
authors.affiliation: Goodman Cancer Centre, McGill University, Montreal, Quebec, Canada.
authors.forename: Ranjana
authors.initials: R
authors.lastname: Pal
authors.affiliation: Goodman Cancer Centre, McGill University, Montreal, Quebec, Canada; Department of Biology, McGill University, Montreal, Quebec, Canada.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Vandal
authors.affiliation: Goodman Cancer Centre, McGill University, Montreal, Quebec, Canada; Department of Biochemistry, McGill University, Montreal, Quebec, Canada.
authors.forename: Chantal
authors.initials: C
authors.lastname: Cadieux
authors.affiliation: Goodman Cancer Centre, McGill University, Montreal, Quebec, Canada.
authors.forename: Lam
authors.initials: L
authors.lastname: Leduy
authors.affiliation: Goodman Cancer Centre, McGill University, Montreal, Quebec, Canada; Department of Biochemistry, McGill University, Montreal, Quebec, Canada.
authors.forename: Sayeh
authors.initials: S
authors.lastname: Davoudi
authors.affiliation: Goodman Cancer Centre, McGill University, Montreal, Quebec, Canada; Department of Biochemistry, McGill University, Montreal, Quebec, Canada.
authors.forename: Laura
authors.initials: L
authors.lastname: Hulea
authors.affiliation: Goodman Cancer Centre, McGill University, Montreal, Quebec, Canada; Department of Biochemistry, McGill University, Montreal, Quebec, Canada.
authors.forename: Lu
authors.initials: L
authors.lastname: Yao
authors.affiliation: BC Cancer Agency, Centre for Translational and Applied Genomics, Vancouver, British Columbia, Canada.
authors.forename: Anthony N
authors.initials: AN
authors.lastname: Karnezis
authors.affiliation: Département de Pathologie et Microbiologie, Faculté de Médecine Vétérinaire, Université de Montréal, St-Hyacinthe, Quebec, Canada.
authors.forename: Marilène
authors.initials: M
authors.lastname: Paquet
authors.affiliation: Goodman Cancer Centre, McGill University, Montreal, Quebec, Canada; Department of Biology, McGill University, Montreal, Quebec, Canada.
authors.forename: David
authors.initials: D
authors.lastname: Dankort
authors.affiliation: Goodman Cancer Centre, McGill University, Montreal, Quebec, Canada; Department of Biochemistry, McGill University, Montreal, Quebec, Canada; Department of Medicine, McGill University, Montreal, Quebec, Canada; Department of Oncology McGill University, Montreal, Quebec, Canada.
authors.forename: Alain
authors.initials: A
authors.lastname: Nepveu
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D002471:Cell Transformation, Neoplastic / Q000235:genetics; D002478:Cells, Cultured; D016922:Cellular Senescence / Q000235:genetics; D004249:DNA Damage; D004260:DNA Repair / Q000502:physiology*; D011905:Genes, ras / Q000502:physiology*; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D008325:Mammary Neoplasms, Experimental / Q000235:genetics; D008822:Mice, Transgenic; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D018384:Oxidative Stress; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D014157:Transcription Factors
chemical_list: C080632:CUX1 protein, human; C000624101:Cux1 protein, mouse; D018398:Homeodomain Proteins; D009687:Nuclear Proteins; D012097:Repressor Proteins; D014157:Transcription Factors