The Effects Of Low Dose Radiation On Tumor Apoptosis, Cell Cycle And Changes Of Apoptosis-Related Protein Bcl-2 In The Tumor-Bearing-Mice

Objective Many experiments and human organism research demonstrated that low dose radiation(LDR) could induce adaptation response of animal and human organism, increase organized immune function and anti-tumor ability. LDR dose little to the isolated tumor cell. LDR's anti-tumor ability dose not aim at and kill tumor cell directly, but by increasing organized whole defensive function. In the condition of organized higher immune function caused by LDR, the study to changes in cell,molecular even gene level of tumor could provide evidence of clinical application for LDR. Bcl-2 oncogene is closely in relation to the apoptosis of cell, which could provide survival signal for cell. So the objective of our experiment is to study the effect of low dose radiation on tumor apoptosis ^ cell cycle and changes of apoptosis-related protein bcl-2 in the tumor-bearing-mice.Methods Kunming stain male mice were implanted the S180 sarcoma cell in the left hint inguen subcutaneously as an experimental in situ animal model. 7 days after implantation , the mice were given 75mGy whole-body y-ray radiation. In the followed 24 hour and 48 hour, all mice were sacrificed to measure the tumor volume, and tumor cell apoptosis^cell cycle was analyzed by flow cytometry in some tumor tissue, the expression of apoptosis-related protein bcl-2 and the apoptosis of tumor cell were observed by immunohistochemistry and electron microscope in the other tumor tissue.Result Compared with the sham-irradiation groups, in the followed 48 hour the tumor growth was significantly slowed down after low dose radiation (P<0. 05) . At 24 hour after radiation the tumor cells were arrested in Gl phase(P<0. 001) , S phase cells decreased significantly(P<0. 01) with no changes of G2/M phase cell and cell apoptosis. Bcl-2 protein is abundant but decreased(P<0. 05). At 48 hour after LDR, the percentage of S phase cell and apoptosis of tumor cells increased significantly(P<0. 01), the percentage of G2/M phase cell decreased significantly (P<0. 01), the percentage of GO/G1 phase cell and expression of bcl-2 protein showed no changes compared with sham-irradiation. Some apoptosis bodies and the picture of apoptosis body phagocytosed by macrophage were found by electron microscope.Conclusion Low dose radiation could slow down the growth of tumor in the tumor-bearing-mice and cause a Gl-phase arrest of tumor cells. LDR increases the apoptosis of tumor cells through the lower levels of apoptosis-related protein bcl-2. The organized immune function and anti-tumor ability was markedly increased after low dose radiation. Respectively LDR provides sensitive G2/M phase and S phase cells for radiotherapy and chemiotherapy, which increases the treatment of radiotherapy and chemiotherapy. Correspondingly LDR induces the organized adaptation response and alleviates the toxicity of ray and chemical drugs. In the result LDR decreases the injury of normal tissue caused by radiotherapy and chemiotherapy. All these study support the combined treatment of radiotherapy chemiotherapy and LDR. It not only proves the LDR's anti-tumor ability, but also provides practical evidence of clinical application to the combined treatment of radiotherapy,chemiotherapy and LDR .