Two Novel Monoclonal Antibodies Against Human CD133-2: Distinct Epitopes and Agonist Activity to Enhance Growth of CD133 Expression CellsIn Vitro

Human AC133 antigen, also called CD133, is a unique transmembrane glycoprotein encoded by the PROM1 gene. It was initially suggested as a cell surface marker for hematopoietic stem/progenitor cells and has also been identified recently as a cancer stem cell marker in brain, colorectal, and prostate cancers. AC133 has two isoforms, one is AC133-1 and the other is AC133-2. Whether the two isoforms are functionally redundant or serve distinct functions remains unclear. In order to further explore the physiological and pathological functions of CD133-2, we generated two mouse antihuman CD133-2 monoclonal antibodies (clones 6B3 and 9G4). Then, we carefully characterized the biological functions of these monoclonal antibodies (MAbs) and showed that 6B3 and 9G4 bound to two epitopes of CD133, which are different from that recognized by the commercially available anti-CD133 MAb (AC141). These two MAbs could be used in cell immunostaining, Western blot, and immunohistochemical staining. We have further shown that MAb 6B3 enhances the growth of human myelogenous leukemic cell line U937 and human colon adenocarcinoma cell line SW480, suggesting a functional role of CD133 in these cells. Taken together as a useful tool, these two antibodies might be of great value for further exploration of the expression and function of CD133.