BACKGROUNDLung cancer cell lines A549 and NCI-H446 with different radiosensitivity to ionizing radiation (IR) have different MDM2 gene expression status, which may contribute to the radioresistance of cells. The aim of this study is to use small interfering RNA (siRNA) targeting MDM2 to investigate the influence of MDM2 gene silencing on radioresponse of A549 cell.

METHODSPlasmid targeting MDM2 was constructed with pPUR/U6 vector and oligonucleotide designed according to the sequence of effective antisense oligonucleotides and principles of siRNA design. A549 cells were transfected by Lipofectamine™ 2000. MDM2 expression in A549 cells was detected by RT-PCR and Western blot. Radiation-mediated cell killing was detected by flow cytometry.

RESULTSTwo out of three siRNA plasmids were constructed successfully. siRNA transfection resulted in downregulaton of MDM2 expression of A549 cells on mRNA and protein levels. After treated with siRNA, radiation-mediated cell killing of A549 cells was significantly increased (P < 0.01).

CONCLUSIONSThe results support the hypothesis that MDM2 gene is a candidate for radioresistance in A549 cells. siRNA targeting to MDM2 can enhance the radiation-mediated cell killing of A549 cells.