Objective: The interstitial implantation of radioactive 125I seeds is an effective therapy for primary or metastatic cancers.However, one part of this treatment has shown poor reaction to radioactive 125I seeds.Clarifications on radiobiological mechanisms involved in the therapy of radioactive 125I seeds may be beneficial to improve curative effects.Methods: We established a new in vitro model to estimate the biological effects of 125I seeds on cancer cells by using a transwell insert.125I seeds were placed on cell culture plates,and the cells were seeded in a transwell chamber.These materials were then used to evaluate the effects of 125I seeds on the motility of cancer cells.The materials were also used for cell proliferation assay and western blot analysis.