CD133, also known as PROM1 (prominin-1) or AC133, belongs to the prominin family. CD133 is a transmembrane glycoprotein with an NH2-terminal extracellular domain, five transmembrane loops and a cytoplasmic tail. The expression of CD133 has been reported in hematopoietic stem cells, endothelial progenitor cells, neuronal and glial stem cells, suggesting the potential role of CD133 as a cell surface marker of adult stem cells. CD133 has also been reported as a marker of cancer stem cells in various human tumors. CD133 is a highly glycosylated protein with an apparent molecular weight of 115-120 kDa. After the treatment of the lysates with glycosidase, CD133 shifted to a protein with an apparent molecular weight of 80-90 kDa (PMID: 23150174; 20068153).