PROM1 and cancer: These highly tumorigenic and metastatic tumor cells, called tumor repopulating cells, because they appear to be distinct from conventional surface stem cell marker selected cancer stem cells or tumor‐initiating cells, express similar levels of cancer stem marker CD133 as the parental melanoma cells but are >100‐fold more efficient in generating tumors and melanoma metastasis in the lung of wild‐type mice (Liu et al., 2012).