Yoon, A. J., Shen, J., Wu, H-C., Angelopoulos, C., Singer, R. S., Chen, R. and Santella, R. M. Expression of Activated Checkpoint Kinase 2 and Histone 2AX in Exfoliative Oral Cells after Exposure to Ionizing Radiation. Radiat. Res. 171, 771–775 (2009).

γ-H2AX (activated histone 2AX) and pChk2 (activated checkpoint kinase 2), which are DNA damage response molecules, are produced in irradiated cells and may be signature molecules of radiation exposure. We investigated their use as potential biomarkers to identify individuals exposed to ionizing radiation. We collected exfoliated oral epithelial cell samples from 100 healthy individuals undergoing routine dental radiographic examination (2.34 cGy) both before and after the radiograph using a non-invasive technique. The expression levels of pChk2 and γ-H2AX in oral cells were assessed by immunohistochemical assay. Both biomarkers showed statistically significant increases in levels of expression after the radiation exposure (P < 0.001). This suggests that pChk2 and γ-H2AX may serve as sensitive indicators of low-dose radiation exposure.