Anti-apoptotic role of S100A8 in X-ray irradiated keratinocytes

Background: Ionizing radiation is used to treat a lot of cancers, however, it also produced unwanted side effect on normal tissues, such as radiodermatitis. We previously established an animal model for radiodermatitis, and identified many of radiation-induced genes by cDNA microarray. Of the candidates, we chose S100A8 gene for a further study. Objective: The aim of this study is to investigate the functional rote of S100A8 in Xray irradiated keratinocytes. Methods: RT-PCR and immunohistochemistry were performed to demonstrate the S100A8 induction by X-ray irradiation. HaCaT keratinocytes were transduced with the recombinant adenovirus expressing GFP-S100A8, and then effects on cell cycle and apoptosis were analyzed using flow cytometry and Western blot. Results: X-ray irradiation markedly induced S100A8 expression in the hyperplastic epidermis of mouse. Overexpression of S100A8 by adenoviral. transduction led to the enhancement of cell proliferation in the absence and/or presence of X-ray irradiation, as compared with Ad/GFP control group. Furthermore, overexpression of S100A8 significantly protected the X-ray-induced apoptosis. Conclusion: These results suggest that S100A8 have an anti-apoptotic role in X-ray irradiated keratinocytes. (C) 2008 Japanese Society for Investigative Dermatology. Published by Elsevier Ireland Ltd. All rights reserved.