title: The influence of the oncogene N-ras on cell cycle delay in a human melanoma cell line with reduced radioresistance.
abstract: In a previous study we found that transfection of a human melanoma cell line with the oncogene N-ras led to increased radiosensitivity as measured by clonogenic assays. Since a shift in radiosensitivity is often correlated with altered G2/M delay, we investigated whether this was also the case in this oncogene containing melanoma cell line (IGRras). A human melanoma cell line, stably transfected with mutated N-ras, and its parental cell line transfected with the neomycin phosphotransferase gene only (IGRneo), were irradiated with 5 Gy and cell cycle distribution was measured at hourly time intervals by DNA staining with propidium iodide. Next, the effect of ionising radiation on the duration of the S-phase was determined by pulse labelling cells with BrdUrd before irradiation. Both cell lines showed a radiation induced G2/M delay, which was most prolonged for the ras transfected cell line. After 5 Gy, the S-phase duration was unaltered, although the shape of the relative movement (RM) curves was slightly different. No G1 delay was observed in either cell line. Ras transfection in a melanoma cell line leads to prolonged G2/M delay after radiotherapy. This prolongation is associated with increased radiosensitivity and not with radioresistance. These data throw doubt on the use of oncogene expression or G2/M delay as predictors of radiosensitivity.
authors.affiliation: Department of Clinical Oncology, University Hospital Leiden, 2300 RC Leiden, The Netherlands.
authors.forename: J
authors.initials: J
authors.lastname: Pomp
authors.forename: I J
authors.initials: IJ
authors.lastname: Ouwerkerk
authors.forename: C
authors.initials: C
authors.lastname: Hoogstraten
authors.forename: J
authors.initials: J
authors.lastname: Wondergem
authors.forename: J
authors.initials: J
authors.lastname: Davelaar
authors.forename: J W
authors.initials: JW
authors.lastname: Leer
authors.forename: P I
authors.initials: PI
authors.lastname: Schrier
mesh_terms: D002453:Cell Cycle / Q000502:physiology* / Q000528:radiation effects; D002455:Cell Division / Q000528:radiation effects; D016195:G2 Phase; D017930:Genes, Reporter; D011905:Genes, ras; D006801:Humans; D019868:Kanamycin Kinase / Q000032:analysis; D008545:Melanoma / Q000473:pathology*; D008938:Mitosis; D016296:Mutagenesis; D011836:Radiation Tolerance; D016196:S Phase; D014162:Transfection; D014407:Tumor Cells, Cultured
chemical_list: D019868:Kanamycin Kinase