Furthermore, both the phosphorylation level and the total expression level of the Akt/mTOR/p70S6K pathway decreased greatly after exposure to carbon ions at all doses employed compared with those after X-ray exposure in MDA-MB-231 cells (Figs 5C and E), which has been proven to be related to the radiation sensitivity of carbon ions in SHG44 and HeLa cells and a mouse squamous carcinoma cell line [14, 25]. This evidence concerns the gene RPS6KB1 and squamous cell carcinoma.