Bystander Effects Induced by the Monolayer and Three Dimensional Cultures Exposed to Ionizing Radiation

Radiation-induced bystander effect (RIBE) was first reported by Nagasawa et al. [1] showed that exposure to very low doses of alpha particles initiated sister chromatid exchange in more cells than that could have been hit by an alpha particle as estimated. Thereafter, different biological endpoints, such as chromosomal aberration, sister chromatid exchange, mutation, apoptosis and changes in the expression of genes and proteins, have been exploited to investigate the lesions in cells that not being directly exposed to ionizing radiation but either sharing medium with or being in contact with directly irradiated samples [2-7]. RIBE has been reported in a variety of cell types induced by both low-LET X or γ-rays and high-LET α-particles, which is of great interest in radiotherapy using X-ray radiation or high-LET heavy ions because of RIBE-related cell killing and carcinogenesis in neighboring normal cells [1,3,4].