Radiosensitizing Effect of IUdR Combined with Co-60 γ Radiation on Malignant Glioma Spheroids

Abstract

Glioma is recognized as one of the most common tumors in the central nervous system. This tumor is resistant to all usual treatments. Because of the anatomical positions of this tumor, the surgery, as a treatment modality, is not possible in all cases. Even in the cases suitable for the surgery, because of the indistinct boundaries of this tumor and normal cells, complete elimination of the tumor is impossible. Glioma cells are also resistant to cytotoxic drugs. So, chemotherapy, as another treatment modality has no effect on this tumor. Sufficient radiation doses to kill the tumor cancer cells are not endurable for normal cells. Therefore, investigators are looking for new approaches to treat this malignant disease. One of the approaches is to use radiosensitizers in combination with the radiotherapy. IUdR is a halogenated pyrimidine which its radiosensitizing effect has been proved. In this research we have studied the effect of IUdR combined with ⁶⁰Co γ radiation for two sizes of Glioma spheroids (100 and 300μm). The spheroid diameters were measured and analyzed to evaluate the level of radiation damages. Our results showed that the combination of IUdR with the ⁶⁰Co γ radiation can increase the radiation damage in both sizes of Glioma spheroids. The induced radiation damage in the greater spheroids was less than the lesser ones. This may be explained by the more hypoxic cells normally existed in greater spheroids. In addition, in greater spheroids more cells are in the G0 phase of the cell cycle and cannot uptake IUdR, so they will not be affected by the sensitizing effect of this radiosensitizer.