[Radiosensitization by double suicide gene system in ACC-2 cell]

To investigate the radiosensitization by prodrug and CD-TK double suicide gene therapy system in adenoid cystic carcinoma cells (ACC-2).

The eukaryotic expression plasmids pIRES-CD and pIRES-TK were introduced into ACC-2 cells by electroporation. Then ACC-2 cells stably expressing CD and TK gene were obtained by 10-day positive selection with 400 micro g/mL G418 . The total RNA was extracted and the expression of the CD and TK gene in transfected ACC-2 cells was identified by RT-PCR. The positive transfected ACC-2 cells were treated with radiotherapy of different dose (0,2,4,6,8,10 Gy) and prodrug system in aerobic and anoxic condition. Then cell clone formation assay was used to study the radiosensitization by CD-TK double suicide gene therapy and prodrug system in ACC-2.The data was analyzed by multiple factor ANOVA using SPSS11.5 software package.

RT-PCR analysis demonstrated that CD and TK genes were effectively expressed in ACC-2 cells. With the increased of X-ray dose, the colony forming rate dropped significantly after radiotherapy. In aerobic condition, the survival fraction of group ACC-2/CD-TK+prodrug were significantly lower than that of group ACC-2 and group ACC-2/CD-TK with the same dose (P<0.05). In anoxic condition, the survival fraction of group ACC-2/CD-TK+pro-drug was significantly lower than that of experimental group ACC-2 and group ACC-2/CD-TK with the same dose (P<0.05). The colony forming rate in aerobic condition was significantly lower than that in anoxic condition of the same cell group and dose.

The radiosensitivity and the killing effect of X ray to ACC-2 cells can be increased by CD-TK double suicide gene therapy and the prodrug system.