Abstract
Purpose: As a foundation for improving cancer radiation treatment, we have been trying to find novel proteins involved in radio-resistance. In this study, we performed proteomic analysis to search for nuclear proteins of which expression levels differ pre- and post-X-ray irradiation. We focused on clarification of the involvement of aldolase A, one of the candidate proteins identified by the analysis, in radio-resistance.
Methods: Fluorescent two-dimensional differential gel electrophoresis (2-D DIGE) was performed to identify proteins that show concentration changes after exposure to X-rays (5Gy) in a nuclear fraction of HeLa cells. Expression of aldolase A in HeLa and UVr-1 cells was suppressed using its specific siRNAs, and the sensitivity of the suppressed cells to X-ray-induced cell death was analyzed by colony survival assay.
Results and discussion: Twenty-four hours after X-ray irradiation of HeLa cells, expression levels of 6 proteins were increased in the nuclear fraction; these proteins included aldolase A, a glycolytic enzyme commonly localized in cytosol. When expression of aldolase A was suppressed by its specific siRNA, sensitization of the suppressed cells to X-ray induced cell death was observed. In addition, expression of aldolase A was higher in a derivative radio-resistant cell line, UVr-1 , than in its parental cell line, RSa. These findings suggest that high levels of aldolase A confer radio-resistance and that aldolase A may play other roles in addition to its role in glycolysis. It is also suggested that suppression of aldolase A expression before irradiation may improve the efficiency of anti-cancer radiation therapy.
