ABSTRACT
Radiotherapy is necessary for 70％ of malignant tumor patients. Local recurrence and metastasis are primary failure models, where radioresistance is one of important factors. It is critical to establish radioresistant tumor cell lines for understanding the mechanism of radioresistance. According to single radiation, fractioned radiation and the compound radiation method, four representative radiation models are classified: conventional radiation, repeated radiation, gradient radiation and other radiation. These different radiation models have difference in total dose and radiation model as well as the biological characteristics. Superior to other three models, the gradient fractioned irradiation model increase fractioned doses gradually along with the enhancement of radioresistance, which favorably balances the fractioned doses and the time of irradiated cells approaching to exponential growth phase. Clinically relevant radioresistant cell line ( CRR) with a genotype in consistent with its parental cells is an important research direction on tumor radioresistance.