title: Does metabolic radiolabeling stimulate the stress response? Gene expression profiling reveals differential cellular responses to internal beta vs. external gamma radiation.
abstract: DNA microarray analyses were used to investigate the effect of cell-incorporated 35S-methionine on human colorectal carcinoma cells. This beta-radiation-induced gene expression profile was compared with that induced by external gamma-radiation. The extent of DNA fragmentation was used as a biomarker to determine the external gamma dose that was bioequivalent to that received by cells incubated in medium containing 35S-methionine. Studies showed that 35S-methionine at 100 microCi/mL induced a much more robust transcriptional response than gamma-radiation (2000 cGy) when evaluated 2 h after the labeling or irradiation period. The cellular response to internal beta-radiation was greater not only with respect to the number of genes induced, but also with respect to the level of gene induction. Not surprisingly, the induced genes overlapped with the set of gamma-responsive genes. However, a distinct beta-gene induction profile that included a large number of cell adhesion proteins was also observed. Taken together, these studies demonstrate that metabolic incorporation of a low energy beta-emitter, such as 35S-methionine, can globally influence a diverse set of cellular activities that can, in turn, affect the outcome of many experiments by altering the cell cycle, metabolic, signaling, or redox status (set point) of the cell. Additional studies of the mechanism of beta-induced proliferation arrest and cell death and of the significance of its differential gene induction/repression profile in comparison to pulsed gamma-irradiation may lead to new insights into the ways in which ionizing radiation can interact with cells.
authors.affiliation: Department of Biochemistry and Molecular Biology, The George Washington University Medical Center, 2300 Eye St., N.W., Washington, DC 20037, USA.
authors.forename: Nicholas F
authors.initials: NF
authors.lastname: Marko
authors.forename: Paul B
authors.initials: PB
authors.lastname: Dieffenbach
authors.forename: Gai
authors.initials: G
authors.lastname: Yan
authors.forename: Susan
authors.initials: S
authors.lastname: Ceryak
authors.forename: Roger W
authors.initials: RW
authors.lastname: Howell
authors.forename: Timothy A
authors.initials: TA
authors.lastname: McCaffrey
authors.forename: Valerie W
authors.initials: VW
authors.lastname: Hu
mesh_terms: D001610:Beta Particles; D016203:CDC2 Protein Kinase / Q000378:metabolism; D016000:Cluster Analysis; D004249:DNA Damage; D005720:Gamma Rays; D015870:Gene Expression / Q000528:radiation effects*; D020869:Gene Expression Profiling; D020868:Gene Silencing; D006801:Humans; D007700:Kinetics; D008715:Methionine / Q000032:analysis; D020411:Oligonucleotide Array Sequence Analysis; D011829:Radiation Dosage; D011849:Radioactive Tracers; D013462:Sulfur Radioisotopes; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D015854:Up-Regulation
chemical_list: D011849:Radioactive Tracers; D013462:Sulfur Radioisotopes; D016159:Tumor Suppressor Protein p53; D008715:Methionine; D016203:CDC2 Protein Kinase