The synchronized positive feedback genetic circuit also has an obvious radiosensitizing effect (TCD50 is 6.16 Gy in A549/pfos-iNOS/TK group, 14.33 Gy in A549/pfos-TK/GFP group, and 15.6 Gy in untransfected A549 group, and SER in A549/pfos-iNOS/TK group and in A549/pfos-TK/GFP group was 2.53 and 1.09, resp., indicating that tumor tissue in A549/pfos-iNOS/TK group was most sensitive to radiation and the synchronized positive feedback genetic circuit greatly increased radiosensitivity of tumor tissue). The gene discussed is NOS2; the disease is neoplasm.