title: The AC133 epitope, but not the CD133 protein, is lost upon cancer stem cell differentiation.
abstract: Colon cancer stem cells (CSC) can be identified with AC133, an antibody that detects an epitope on CD133. However, recent evidence suggests that expression of CD133 is not restricted to CSCs, but is also expressed on differentiated tumor cells. Intriguingly, we observed that detection of the AC133 epitope on the cell surface decreased upon differentiation of CSC in a manner that correlated with loss of clonogenicity. However, this event did not coincide with a change in CD133 promoter activity, mRNA, splice variant, protein expression, or even cell surface expression of CD133. In contrast, we noted that with CSC differentiation, a change occured in CD133 glycosylation. Thus, AC133 may detect a glycosylated epitope, or differential glycosylation may cause CD133 to be retained inside the cell. We found that AC133 could effectively detect CD133 glycosylation mutants or bacterially expressed unglycosylated CD133. Moreover, cell surface biotinylation experiments revealed that differentially glycosylated CD133 could be detected on the membrane of differentiated tumor cells. Taken together, our results argue that CD133 is a cell surface molecule that is expressed on both CSC and differentiated tumor cells, but is probably differentially folded as a result of differential glycosylation to mask specific epitopes. In summary, we conclude that AC133 can be used to detect cancer stem cells, but that results from the use of this antibody should be interpreted with caution.
authors.affiliation: Laboratory for Experimental Oncology and Radiobiology, Center for Experimental and Molecular Medicine, and Department of Pathology, Academic Medical Center, 1105AZ Amsterdam, the Netherlands.
authors.forename: Kristel
authors.initials: K
authors.lastname: Kemper
authors.forename: Martin R
authors.initials: MR
authors.lastname: Sprick
authors.forename: Martijn
authors.initials: M
authors.lastname: de Bree
authors.forename: Alessandro
authors.initials: A
authors.lastname: Scopelliti
authors.forename: Louis
authors.initials: L
authors.lastname: Vermeulen
authors.forename: Maarten
authors.initials: M
authors.lastname: Hoek
authors.forename: Jurrit
authors.initials: J
authors.lastname: Zeilstra
authors.forename: Steven T
authors.initials: ST
authors.lastname: Pals
authors.forename: Huseyin
authors.initials: H
authors.lastname: Mehmet
authors.forename: Giorgio
authors.initials: G
authors.lastname: Stassi
authors.forename: Jan Paul
authors.initials: JP
authors.lastname: Medema
mesh_terms: D000071916:AC133 Antigen; D000818:Animals; D015703:Antigens, CD / Q000096:biosynthesis / Q000235:genetics / Q000276:immunology*; D002454:Cell Differentiation; D003110:Colonic Neoplasms / Q000235:genetics / Q000276:immunology* / Q000378:metabolism / Q000473:pathology*; D015536:Down-Regulation; D000939:Epitopes / Q000276:immunology; D015972:Gene Expression Regulation, Neoplastic; D006023:Glycoproteins / Q000096:biosynthesis / Q000235:genetics / Q000276:immunology*; D006031:Glycosylation; D006801:Humans; D051379:Mice; D016688:Mice, Inbred NOD; D016513:Mice, SCID; D014411:Neoplastic Stem Cells; D010455:Peptides / Q000235:genetics / Q000276:immunology*; D011401:Promoter Regions, Genetic; D020033:Protein Isoforms; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D014407:Tumor Cells, Cultured
chemical_list: D000071916:AC133 Antigen; D015703:Antigens, CD; D000939:Epitopes; D006023:Glycoproteins; C000606023:PROM1 protein, human; D010455:Peptides; C000606024:Prom1 protein, mouse; D020033:Protein Isoforms; D012333:RNA, Messenger