CD133, originally known as AC133. CD133 is a glycoprotein also known in humans and rodents as Prominin 1 (PROM1). Currently the function of CD133 is unknown. It is a member of pentaspan transmembrane glycoproteins (5-transmembrane, 5-TM), which specifically localize to cellular protrusions.
CD133 is expressed in hematopoietic stem cells, endothelial progenitor cells, glioblastoma, neuronal and glial stem cells, various pediatric brain tumors, as well as adult kidney, mammary glands, trachea, salivary glands, placenta, digestive tract, testes, and some other cell types.
Recent studies in brain tumors have identified a CD133+ cell population thought to be a cancer stem cell population, which is rare, undergoes self-renewal and differentiation, and can propagate tumors when injected into immune-compromised mice. However, subsequent studies have indicated the difficulty in isolating pure CSC populations.