Specific gene expression by extremely low-dose ionizing radiation which related to enhance proliferation of normal human diploid cells

Abstract

We demonstrated that X-ray irradiation at low doses of between 2 and 5 cGy stimulated proliferation of a normal human diploid. At low doses of between 2 and 5 cGy, ERK1/2 was phosphorylated as efficiently as at higher doses between 50 and 100 cGy of X-rays, while the p53 protein level was not increased by doses below 50 cGy. On the other hand, the p53 protein was efficiently accumulated at higher doses of X-ray more than 100 cGy. ERK1/2 was phosphorylated by doses over 50 cGy with increasing doses. We found that activated ERK1/2 augmented phosphorylation of the Elk-1 protein. Furthermore, over expression of ERK2 in NCI-H1299, and human lung carcinoma cells, potentiated enhanced proliferation, while down-regulation of ERK2 using the anti-sense ERK2 gene abrogated the stimulative effect of low-dose irradiation. These results indicate that a limited range of low-dose ionizing radiation differentially activate ERK1/2 kinases, which causes enhanced proliferation of cells receiving very low doses of ionizing radiation.