PROBLEM TO BE SOLVED: To provide a method for selective removal of undifferentiated cells remaining in a cell population differentiated from a stem cell.SOLUTION: The present invention provides an agent for killing undifferentiated cells and/or cells responsible for tumorigenesis, the agent comprising a virus vector that includes a promoter of a nucleic acid encoding an essential factor for the replication or assembly of at least one virus, and the promoter being replaced with a promoter of a gene specifically expressed in cancer cells or undifferentiated cells. The present invention also provides an agent for killing undifferentiated cells and/or cells responsible for tumorigenesis, the agent comprising an expression vector containing a nucleic acid encoding a cytotoxic factor under the control of a promoter of a gene specifically expressed in cancer cells or undifferentiated cells. The present invention further provides a method for producing a differentiated cell with a reduced tumorigenic risk, the method comprising contacting the agent to a cell population differentiated from a stem cell to kill undifferentiated cells and/or cells responsible for tumorigenesis remaining in the cell population.SELECTED DRAWING: Figure 6【課題】幹細胞から分化誘導された細胞集団に残存する未分化細胞の選択的除去方法の提供。【解決手段】少なくとも１つのウイルスの複製又はアッセンブリに必須の因子をコードする核酸のプロモーターが癌細胞又は未分化細胞で特異的に発現する遺伝子のプロモーターで置換されているウイルスベクターを含有してなる、未分化細胞及び／又は腫瘍化の原因となる細胞の殺傷剤。癌細胞又は未分化細胞で特異的に発現する遺伝子のプロモーターの制御下にある細胞毒性因子をコードする核酸を含む発現ベクターを含有してなる、未分化細胞及び／又は腫瘍化の原因となる細胞の殺傷剤。さらに、幹細胞から分化誘導された細胞集団に上記薬剤を接触させることにより、該細胞集団内に残存する未分化細胞及び／又は腫瘍化の原因となる細胞を殺傷する、腫瘍化リスクの低減された分化細胞の製造方法。【選択図】図６
