Updated project metadata. We demonstrate for the first time that under hypoxic conditions, A431 epithelial carcinoma cells exhibit increased viability when exposed to low-dose γ-irradiation, indicating that radiotherapy can promote tumor cell survival when oxygen supply is limited. When assessed using iTRAQ quantitative proteomics and Western blotting, irradiated tumor cells were observed to significantly up-regulate the expression of calcium-binding proteins CALM1, CALU and RCN1, suggesting important roles for these mediators in promoting tumor cell survival during hypoxia.