Abstract
To compare gene expression with time in murine NIH/PG13Luc cells exposed to low dose-rate radiation (LDR) and middle dose-rate radiation (MDR), total 10 genes including p53-dependent genes (CyclinG1, p21, Ephx1), extra-cellular-matrix related-genes (Tnc, Col1a2, Fbln5) and cell-cycle related-genes (Mapk9, Rbl1, Mcm6, Cdc2A) were selected based on the result of the previous microarray analyses. p53-dependent genes (CyclinG1, p21, Ephx1) were up-regulated at more than 15 mGy/hr. The early and late responses of p53-dependent genes were confirmed by using a high dose-rate radiation (HDR) (1.1 Gy/min). On the other hand, extra-cellular matrix related-genes (Tnc, Col1a2, Fbln5) were up-regulated at a dose rate higher than 1 mGy/hr. The expressions of extra-cellular matrix related-genes were not up-regulated on early response, but were up-regulated on late responses by exposure to HDR. Expressions of Tnc and Col1a2 increased by only adding human rTGF-β1. And Tgfb1 increased by irradiation. Expressions of cell cycle related-genes (Rbl1, Mcm6, Cdc2A) were down-regulated at 15 and 60 mGy/hr, but not at 1.1 Gy/min. These results indicate that the up- and down- regulation pathways for p53-independent genes are different from those for p53-dependent genes induced by LDR and MDR. (This study was supported by a grant from Aomori prefecture, Japan)
