To confirm whether the AKT/mTOR/p70S6K signalling pathway is involved in the lethal effects caused by carbon ion and X-ray irradiation, the radioresistant triple-negative breast cancer cell line MDA-MB-231 and the more sensitive MCF-7 (ER+/PR−/HER2−) cancer cell line were used to detect cell proliferation, cell colony formation, cell cycle distribution, DNA damage, cell apoptosis and Akt/mTOR/p70S6K signalling pathway activity in both cell lines at 48 h after exposure to two different types of radiation. This evidence concerns the gene RPS6KB1 and cancer.