BMI1 and neoplasm: ALDH-positive HBL-100 and SKBR3 cells showed increased expression of the putative stem cell marker proteins Nanog and BMI1 but not Sox2 and Oct4, see Figure 1D. Besides regulating cell proliferation and survival, Notch and PI3K/Akt signaling are important pathways that mediate radiation resistance in tumor cells [25,26].