Pronounced gene expression of NOTCH pathway components (i.e., DLL1, JAG1, HES1, NOTCH1, and NOTCH2) was found in the human pituitary tumor SP (28) while other candidate TSC populations (i.e., human tumorspheres and CD133+ cell populations) showed increased expression of DLL1, JAG2, NOTCH1, and NOTCH4 (25, 26). This evidence concerns the gene DLL1 and pituitary tumor.