Tumor-specific promoters can induce high-efficiency and specific expression of exogenous genes in tumor cells. At present, commonly used promoters include alpha-fetoprotein promoter, carcinoembryonic antigen promoter,prostate specific antigen promoter,human telomerase reverse transcriptase promoter and multidrug resistance gene promoter and etc. Dual promoters, enhancer, regulatory element and other physical or chem-ical factors could be used to reconstruct or modify promoters to increase the expression and location of exogenous genes in tumor cells. Tumor-specific promoters play an important role in cancer gene targeted therapy by cou-pling with suicide gene, anti- oncogene, antiseuse nucleic acid, apoptosis gene and RNA interference.

Objective To compare the effects of two head holders on the setup errors during head and neck neoplasms radiotherapy.Methods Totally 30 patients were divided into groups A and B randomly and equally.Group A applied TypeSTM Extension for setup,and group B used Type-S Overlay Board,with thermoplastic film applied to fixation.Varian23IX image guided linear accelerator was involved in the therapy,and the patients underwent CBCT-guided therapy once a week in 6 weeks.The setup errors at left-right,head-foot and anterior-posterior directions were obtained by bone registration and manual checking.Results The absolute setup error at anterior-posterior direction of group A,was (2.31 ± 1.35) mm,which was significantly higher than (1.88±1.79) mm of group B (P=0.032).There were no obvious differences between the setup errors of group A and those of group B (P＞0.05),and the weekly absolute errors of group A were not statistically different from those of group B (P＞0.05).Conclusion There are no significant differences between the effects of the two head holders on the setup errors during head and neck neoplasms radiotherapy,and proper head holder can be selected according to clinical requirements.