Effect of silencing Annexin A2 gene expression by siRNA on radiosensitivity of nasopharyngeal carcinoma cells

Objective To investigate the effect of silencing Annexin A2 gene expression by small interfering RNA (siRNA) on the radiosensitivity of nasopharyngeal carcinoma cells CNE-2 (R743) . Methods siRNA targeting the Annexin A2 gene was chemically synthesized and transfected into R743 cells by HiPerFect. The mRNA and protein levels of Annexin A2 before and after transfection were measured by RT-PCR and Western blot, respectively. The change in radiosensitivity of R743 cells was analyzed by colonyforming assay. Cell cycle distribution and apoptosis after X-ray irradiation were analyzed using flow cytometry and terminal deoxynucleotidyl transferase dUTP nick end labeling assay, respectively. Results The results from RT-PCR and Western blot showed that the expression of Annexin A2 was down-regulated after transfection. The colony-forming assay indicated that the D0, Dq, and SF2 in transfected cells were significantly lower than those in untransfected cells with radiation alone and in cells transfected with control siRNA. The sensitization enhancement ratios (D0 ratios) of transfected cells relative to untransfected and control siRNA transfected cells were 1.30 and 1.27, respectively. After X-ray irradiation, the proportion of cells in G2/M phase was significantly higher in the transfected cells than in untransfected and control siRNA transfected cells (32.46% vs. 9.17% and 9.42%, respectively; P=0.000 and 0.000). The apoptosis rate was also significantly higher in the transfected cells than in the untransfected and control siRNA transfected cells (35.20% vs. 10.87% and 11.33%, respectively; P=0.000 and 0.000) . Conclusions Silencing Annexin A2 gene expression by siRNA can increase the radiosensitivity of R743 cells, which may be associated with DNA damage repair and change in cell cycle distribution. Key words: RNA interference; Annexin A2 gene; Cell line, nasopharyngeal neplasms; Radiosensitivity