Improvements to external stents to render incompetent venous valves competent are disclosed. According to the present invention, there is enabled a screening of a novel anticancer agent which allows a more efficient therapy for a cancer, wherein the agent is an agent capable of enhancing the sensitivity of a cell to an anticancer agent comprising a DNA-damaging factor or an agent having a DNA-damaging action. Different foam molds can be used to form differently shaped front surfaces on the foam component. All the turn portions of the turn portion group protrude from the same slot of the stator core.