Sensitivity to ionizing radiation in Saos-2 cells transfected with mutant p53 genes depends on the mutation position

We have constructed an in vitro system to examine how p53 mutants affect radiosensitivity. Mutations of p53 were made using in vitro mutagenesis, and mutant cDNAs were introduced into the human osteosarcoma cell line, Saos-2, which is devoid of endogenous p53. For wild type p53, both the expression plasmid and a regulation plasmid (LacSwitch system) were transfected into the cells. The radiosensitivities of clones of mutant p53 and wild type p53 were examined. Transformants of wild type p53 had increased radiosensitivity. The induction of wild type p53 protein by addition of IPTG did not significantly increase radiosensitivity. A mutation at codon 123 also increased radiosensitivity. Mutations at codons 143, 175, and 273 did not alter radiosensitivity.