Effect of G-radiation and scanning proton beam on the morphofunctional characteristics of rat sarcoma M-1

Today proton therapy (PT) is the most advanced radiation therapy. Due to precise delivery of charged particles to a target, proton therapy destroys cancer cells, the risk of damaging surrounding tissues is very low. At present, physical properties of proton beams are understood, however their biological effectiveness needs further study. Effectiveness of radiotherapy depends on radiosensitivity of cancer cells. There are several factors that can determine radiosensitivity of tumor cells. One of them, mutant form of tumor-suppressor p53-gene (mt p53), makes possible determining tumor radiosensitivity, predicts the development and outcome of a disease. The mutant p53-gene occurs in tumor cells of more than 50% of cancer patients. However, there is no much information on its role in sensitivity of tumor cells to PT. The paper presents results of the study of effects of photon radiation with 60Co and proton beams on morphology and function of mt p53 positive sarcoma M-1 cells. Methods of study included: p53 immune-histochemical staining, proliferatiing cells nuclear antigen (PCNA), endothelium marker CD31, and determining mitotic and apoptotic indexes. The cells were exposed to gamma-radiation or to proton beams, radiation doses in the tests was the same. The study findings are the following: effectiveness of g-positive therapy estimated by the level of mitotic and of repopulating activity of irradiated neoplastic cells, induction of abnormal mitotic figures and apoptosis differs from the effectiveness of proton therapy; antitumor effect of proton therapy is more pronounced as compared with the effect of gamma-therapy. Relative biological effectiveness, RBE, of protons estimated by reduction of PCNA-positive fraction of tumor cells, increase in the number of abnormal mitotic figures and induced apoptosis was 1.3; 1.4 и 1.6 respectively.