PROM1 and cancer: Concerning the epithelial compartment, we further identified 4 epithelial subpopulations in 5,533 tumor cells: cancer stem cells (CSCs) (Lgr5+ and Prom1+) and cycling progenitor cells (CPs) (Prom1+ and Ccnd1+), summarized as stem cell compartment (STEM), since CP still expressed stem cell marker genes.