Experimental Study Of APE1 RNA Interference Enhancing The Sensitivity Of Radiotherapy In Osteosarcoma

Osteosarcoma is malignant primary tumor of bone with poor prognosis which usually occurs in the second and third decade of life. Radiotherapy is one of the most commonly used clinical treatments for tumors, but some tumors are resistant to routine photon ray, for example X-ray andγ-ray. It is necessary to seek a new ray to treat tumors effectively, and neutron ray may be a promising option. In addition, cancer cells outside the immediate field of radiation exposure or that have metastasized to distant sites are not destroyed. Therefore, it has become an important issue in radiation oncology to seek for measures to decrease local radiation dose and increase anti-tumor effect. Gene-therapy in combination with radiotherapy is one of the most important developments.The human apurinic/apyrimidinic endonuclease(APE1), redox factor-1, plays a crucial role to protect against cell death due to ROS and possess anti-apoptosis effect. So we suppose that Ape1 may contribute to the resistance to radiotherapy. RNA interference (RNAi) may be an optimized molecular biological means with following important features: high stability, high efficiency, and high specificity. Hence, it may become a new means of tumor gene therapy. One strategy for tumor gene therapy is to inhibit expression of DNA damage and repair gene APE1, selectively enhance sensitivity of radiotherapy in osteosarcoma cells with the purpose of eliminating tumor cell rapidly and effectively.We apply MMT assay,clone formation assay and alkaline comet assay to detect cell survival rate,the ability of clone formation and single brand break of DNA, and detect cell apoptosis via flow cytometer, analysis the radiobiological reaction of osteosarcoma. Using RNAi technology, we knock down the Ape1 expression in the osteosarcoma cell and explore its antitumor effect in combination with 252Cf neutron ray radiotherapy. As establishing tumor-bearing nude mice model, we can plot the tumor growth curves, observe the APE1 expression and intratumor microvessel density (MVD) by immunohistochemistry and detect apoptosis by terminal dUTP nickend labeling (TUNEL) technique.Objective1. To explore the radiosensitization of 252Cf neutron-ray and 192Ir-ray in HOS cells.