This ability of breast CICs to retain self-renewal capacity after fractionated radiation was in agreement with our previous studies reporting that fractionated radiation of U87MG xenographs in nude mice increased the Ki-67 labeling index of glioma CICs and increased the ratio of CICs/non-tumorigenic cells in tumors 72 h after the last radiation dose [13]. The gene discussed is MKI67; the disease is central nervous system cancer.