Low-dose Radiation Induces Antitumor Effects and Erythrocyte System Hormesis

Objective: Low dose radiation may stimulate the growth and development of animals, increase life span,enhance fertility, and downgrade the incidence of tumor occurrence.The aim of this study was to investigate theantitumor effect and hormesis in an erythrocyte system induced by low-dose radiation.
Methods: Kunming strainmale mice were subcutaneously implanted with S180 sarcoma cells in the right inguen as an experimental in situanimal model. Six hours before implantation, the mice were given 75mGy whole body X-ray radiation. Tumorgrowth was observed 5 days later, and the tumor volume was calculated every other day. Fifteen days later, all micewere killed to measure the tumor weight, and to observe necrotic areas and tumor-infiltration-lymphoreticularcells (TILs). At the same time, erythrocyte immune function and the level of 2,3-diphosphoglyceric acid (2,3-DPG) were determined. Immunohistochemical staining was used to detect the expression of EPO and VEGFR oftumor tissues.
Results: The mice pre-exposed to low dose radiation had a lower tumor formation rate than thosewithout low dose radiation (P < 0.05). The tumor growth slowed down significantly in mice pre-exposed to lowdose radiation; the average tumor weight in mice pre-exposed to low dose radiation was lighter too (P < 0.05).The tumor necrosis areas were larger and TILs were more in the radiation group than those of the group withoutradiation. The erythrocyte immune function, the level of 2,3-DPG in the low dose radiation group were higherthan those of the group without radiation (P < 0.05). After irradiation the expression of EPO of tumor tissuesin LDR group decreased with time. LDR-24h, LDR-48h and LDR-72h groups were all statistically significantlydifferent from sham-irradiation group. The expression of VEGFR also decreased, and LDR-24h group was thelowest (P < 0.05).
Conclusion: Low dose radiation could markedly increase the anti-tumor ability of the organismand improve the erythrocyte immune function and the ability of carrying O2. Low-dose total body irradiation,within a certain period of time, can decrease the expression of hypoxia factor EPO and VEGFR, which mayimprove the situation of tumor hypoxia and radiosensitivity of tumor itself.