The comparison of cell-killing effect on tumor cell between low-dose-rate beta-irradiation of P-32 and gamma-irradiation of Co-60

Objectives To elucidate the radiobiological mechanism underlying low-dose-rate irradiation effects on tumor cell-killing thorough the comparison of radiobiological characteristics between low- and high-dose-rate irradiations.

Methods HeLa cells were exposed to low-dose-rate β-irradiation of ³²P or high-dose-rate γ-irradiation of ⁶⁰Co. Cell response-patterns were compared between two types of radiations, focusing on the relation of different type of radiation to radiation-induced reproductive cell death(senescence) and necrotic cell death evaluated by X-gal senescence staining and typan blue excluded method, respectively.

Results Data showed that there is a different cell-killing pattern in HeLa cells between the radiation of ³²P at dose-rate 0.375cGy/min and that of ⁶⁰Co at dose-rate of 206cGy/min by the time of 72h post-radiation. In exposure to ³²P, more HeLa cells go to reproductive cell death, being eliminated by apoptosis, than to ⁶⁰Co. X-gal staining showed that senescent cell ratio in HeLa cells after exposure of ³²P was higher than ⁶⁰Co witch caused more necrotic cell death.

Conclusions There is more reproductive and less necrotic cell death contributing to total cell death in HeLa cells by radiation of ³²P than by ⁶⁰Co. Understanding the underlying mechanism of radiobiology in different radiation is helpful in radiotherapy of malignant tumor by choosing a more reasonable and effective procedure of treatment.