Identification of CD200+ colorectal cancer stem cells and their gene expression profile.

CD200 is a cell surface glycoprotein that has been implicated in a variety of human cancer cells. It has been proposed as a cancer stem cell (CSC) marker in colon cancer and is closely related to tumor immunosuppression. However, there is little functional data supporting its role as a true CSC marker, and the mechanism by which CD200 contributes to colorectal cancer has not been elucidated. In the present study, CD200+ and CD200- COLO 205 colorectal cancer cells were sorted out by flow cytometry, and colonosphere formation and Transwell migration assays were performed. Affymetrix Human U133 Plus2.0 arrays were used to screen the gene expression profiles of CD200+ and CD200- colorectal cancer cells. The results suggest that there are differentially expressed genes between the two subpopulations, including several important genes that function in cell proliferation, metastasis, apoptosis and the immune response. Pathway analysis revealed that the Wnt, MAPK and calcium signaling pathways were differentially expressed between CD200+ and CD200- cells. Moreover, several key genes upregulated in CD200+ cells were also highly overexpressed in CD44+CD133+ colorectal stem cells compared to the CD44-CD133- fraction of the same cell line. In the present study, we showed for the first time a correlation between CD200 expression and the Wnt signaling pathway in colon cancer cells.