To clarify the biological effects of space environment, especially space radiations, a proposal of "Rad Gene" was performed as the first life science experiment with two human lymphoblastoid cell lines bearing wild-type p53 gene (wtp53) and mutated p53 gene (mp53) in an International Space Station (ISS) for 133 days. We scheduled four projects: (1) DNA damage induced by space radiations including the high linear energy transfer (LET) particles was detected as a track of γH2AX foci in the nuclei of these frozen cells. (2) To examine the biological effects of microgravity and space radiations on gene and protein expression of p53-dependent regulated genes, these cells were grown under microgravity and 1 gravity in ISS, and on ground for 8 days and analyzed by DNA and protein arrays. (3) p53-Dependent regulated genes were analyzed in the cultured cells after spaceflight at frozen state exposed to space radiations. (4) To clarify the effects of space radiations on the radio-adaptive response, the space flown cells at frozen state were cultured, and then exposed to challenging X-ray-irradiation. All of the radio-adaptive responses of cell killing, apoptosis, chromosomal aberrations and mutations were found only in wtp53 cells, but not in the mp53 cells.