title: E1a promotes c-Myc-dependent replicative stress: implications in glioblastoma radiosensitization.
abstract: The E1a gene from adenovirus is known to be a potent inducer of chemo/radiosensitivity in a wide range of tumors. However, the molecular bases of its radiosensitizer properties are still poorly understood. In an attempt to study this effect, U87MG cells, derived from a radio-resistant tumor as glioblastoma, where infected with lentivirus carrying E1a gene developing an acute sensitivity to ionizing radiation. The induction of radiosensitivity correlated with a marked G 2/M phase accumulation and a potent apoptotic response. Our findings demonstrate that c-Myc plays a pivotal role in E1a-associated radiosensitivity through the induction of a replicative stress situation, as our data support by genetic approaches, based in interference and overexpression in U87MG cells. In fact, we present evidence showing that Chk1 is a novel transcriptional target of E1a gene through the effect exerted by this adenoviral protein onto c-Myc. Moreover, c-Myc upregulation also explains the marked phosphorylation of H2AX associated to E1a expression in the absence of DNA damage. Indeed, all these observations were applicable to other experimental models, such as T98G, LN-405 and A172, rendering the same pattern in terms of radiosensitivity, cell cycle distribution, upregulation of Chk1, c-Myc, and phosphorylation pattern of H2AX. In summary, our data propose a novel mechanism to explain how E1a mediates radiosensitivity through the signaling axis E1a→c-Myc→ replicative stress situation. This novel mechanism of E1a-mediated radiosensitivity could be the key to open new possibilities in the current therapy of glioblastoma.
authors.affiliation: Laboratorio de Oncología Molecular; Centro Regional de Investigaciones Biomédicas; Universidad de Castilla-La Mancha/PCyTA/ Unidad de Biomédicina UCLM-CSIC; Albacete, Spain.
authors.forename: María Llanos
authors.initials: ML
authors.lastname: Valero
authors.affiliation: Laboratorio de Oncología Molecular; Centro Regional de Investigaciones Biomédicas; Universidad de Castilla-La Mancha/PCyTA/ Unidad de Biomédicina UCLM-CSIC; Albacete, Spain.
authors.forename: Francisco Jose
authors.initials: FJ
authors.lastname: Cimas
authors.affiliation: Laboratorio de Oncología Molecular; Centro Regional de Investigaciones Biomédicas; Universidad de Castilla-La Mancha/PCyTA/ Unidad de Biomédicina UCLM-CSIC; Albacete, Spain.
authors.forename: Laura
authors.initials: L
authors.lastname: Arias
authors.affiliation: Laboratorio de Oncología Molecular; Centro Regional de Investigaciones Biomédicas; Universidad de Castilla-La Mancha/PCyTA/ Unidad de Biomédicina UCLM-CSIC; Albacete, Spain.
authors.forename: Pedro
authors.initials: P
authors.lastname: Melgar-Rojas
authors.affiliation: Laboratorio de Oncología Molecular; Centro Regional de Investigaciones Biomédicas; Universidad de Castilla-La Mancha/PCyTA/ Unidad de Biomédicina UCLM-CSIC; Albacete, Spain.
authors.forename: Elena
authors.initials: E
authors.lastname: García
authors.affiliation: Laboratorio de Oncología Molecular; Centro Regional de Investigaciones Biomédicas; Universidad de Castilla-La Mancha/PCyTA/ Unidad de Biomédicina UCLM-CSIC; Albacete, Spain.
authors.forename: Juan Luis
authors.initials: JL
authors.lastname: Callejas-Valera
authors.affiliation: Laboratorio de Oncología Molecular; Centro Regional de Investigaciones Biomédicas; Universidad de Castilla-La Mancha/PCyTA/ Unidad de Biomédicina UCLM-CSIC; Albacete, Spain.
authors.forename: Jesús
authors.initials: J
authors.lastname: García-Cano
authors.affiliation: Laboratorio de Oncología Molecular; Centro Regional de Investigaciones Biomédicas; Universidad de Castilla-La Mancha/PCyTA/ Unidad de Biomédicina UCLM-CSIC; Albacete, Spain.
authors.forename: Leticia
authors.initials: L
authors.lastname: Serrano-Oviedo
authors.affiliation: Laboratorio de Oncología Molecular; Centro Regional de Investigaciones Biomédicas; Universidad de Castilla-La Mancha/PCyTA/ Unidad de Biomédicina UCLM-CSIC; Albacete, Spain.
authors.forename: Miguel Ángel
authors.initials: MÁ
authors.lastname: de la Cruz-Morcillo
authors.affiliation: Department of Biochemistry; School of Medicine;Biomedical Research Institute of Madrid CSIC/UAM; Madrid, Spain.
authors.forename: Isabel
authors.initials: I
authors.lastname: Sánchez-Pérez
authors.affiliation: Laboratorio de Oncología Molecular; Centro Regional de Investigaciones Biomédicas; Universidad de Castilla-La Mancha/PCyTA/ Unidad de Biomédicina UCLM-CSIC; Albacete, Spain.
authors.forename: Ricardo
authors.initials: R
authors.lastname: Sánchez-Prieto
mesh_terms: D017500:Adenovirus E1A Proteins / Q000008:administration & dosage / Q000235:genetics*; D045744:Cell Line, Tumor; D004261:DNA Replication / Q000235:genetics; D005909:Glioblastoma / Q000235:genetics / Q000473:pathology / Q000532:radiotherapy*; D006801:Humans; D016086:Lentivirus / Q000235:genetics; D016271:Proto-Oncogene Proteins c-myc / Q000096:biosynthesis / Q000235:genetics*; D011836:Radiation Tolerance / Q000187:drug effects / Q000235:genetics*; D013312:Stress, Physiological / Q000235:genetics
chemical_list: D017500:Adenovirus E1A Proteins; C489427:MYC protein, human; D016271:Proto-Oncogene Proteins c-myc
keywords: Chk1; E1a; c-Myc; glioblastoma; radiosensitivity; replicative stress