Effects of Combined Exposure to Carbon Ions and Protons on the Pool of MCF-7 Breast Cancer Stem Cells In Vitro.

We studied the effects of single and combined action of protons and carbon ions C on the pool of MCF-7 human breast cancer stem cells. Single irradiation with a beam of protons or carbon ions had no significant effects on the relative number of cancer stem cells (CSC). The effects of combined irradiation in a total equieffective dose of 4 Gy depended on the sequence of exposure to ionizing radiations: the relative number of CSC did not change after irradiation with carbon ions and then with protons, but increased in the case of the reverse sequence.