Effect of the insulin-like growth factor I receptor on ionizing radiation-induced cell death in mouse embryo fibroblasts.
We have investigated the effect of the insulin-like growth factor I receptor (IGF-IR) on ionizing radiation (IR)-induced cell death using the following two mouse embryo fibroblast cell lines: (i) R- cells with a null mutation of the IGF-IR gene, therefore expressing no endogenous IGF-IR; (ii) R+ cells derived from R- cells, a stable transfectant overexpressing the human IGF-IR. Numbers of R- cells began to detach from dishes and float into the medium about 48 h after 10 Gy of X-irradiation. Internucleosomal DNA fragmentation detected by agarose gel electrophoresis, which is characteristic of apoptosis, was observed in the floating R- cells, but not in the attached cells. Unexpectedly, morphological analysis of the floating cells 72 h after irradiation revealed that only about half of them showed apoptotic death and the rest showed a nonapoptotic, presumably necrotic, one. On the other hand, R+ cells retained more than 90% viability even 4 days after irradiation, and very few floating cells were observed. The G2 arrest was induced in both cell lines following irradiation and G2/M fractions similarly returned to normal levels by around 20 h after irradiation, indicating that the cell death which appeared thereafter in R- cells is mediated through mitosis. Significant induction of p53 following irradiation was not detected by Western blot analysis in either R- or R+ cells. Collectively, these results demonstrate that signal transduction pathways originating from the IGF-IR may be involved in preventing IR-induced apoptosis and necrosis without affecting cell cycle arrest or p53 pathways.
Nakamura
S
S
Faculty of Dentistry, Tokyo Medical and Dental University, Yushima 1-5-45, Bunkyo-ku, Tokyo, 113, Japan.
Watanabe
H
H
Miura
M
M
Sasaki
T
T
D000818:Animals; D017209:Apoptosis / Q000528:radiation effects; D002448:Cell Adhesion / Q000528:radiation effects; D016923:Cell Death / Q000502:physiology / Q000528:radiation effects*; D002455:Cell Division / Q000528:radiation effects; D002470:Cell Survival / Q000528:radiation effects; D053938:DNA Fragmentation; D004307:Dose-Response Relationship, Radiation; D004622:Embryo, Mammalian; D005347:Fibroblasts / Q000166:cytology / Q000502:physiology / Q000528:radiation effects; D006801:Humans; D051379:Mice; D017526:Receptor, IGF Type 1 / Q000096:biosynthesis / Q000502:physiology*; D011994:Recombinant Proteins / Q000096:biosynthesis; D013997:Time Factors; D014162:Transfection; D016159:Tumor Suppressor Protein p53 / Q000096:biosynthesis; D014965:X-Rays
D011994:Recombinant Proteins; D016159:Tumor Suppressor Protein p53; D017526:Receptor, IGF Type 1