Abstract: Objective To investigate the expression pattern of CD133 and ALDH1 in colorectal cancer cells line Colo205 cultured
in serum-free medium (SFM) containing recombinant human epidermal growth factor (EGF) and basic fibroblast growth factor
(bFGF). Methods Colo205 cells were cultured in serum-free medium (SFM) containing human recombinant EGF and bFGF or
in serum-supplemented medium (SSM). The expression of CD133 was analyzed in both groups, and CD133+ and CD133- cells
sorted from the SFM group using flow cytometry and observed microscopically for their growth status. The expression of
CD133 and ALDH1 in CD133+ cells and CD133- cells was detected by immunofluorescence assay. CD133+ cells and CD133- cells
were then injected subcutaneously into NOD/SCID mice and the expression of ALDH1 in the tumor tissues was detected by
immunohistochemistry. Results The cells in SFM group showed a significantly higher percentage of CD133+ cells than those in
SSM group (P<0.05). In SFM, CD133+ cells were capable of forming tumor spheres while CD133- cells could not; CD133+cells
strongly expressed CD133 and ALDH1 and CD133- cells did not. In mice, tumors generated by CD133+ cells, but not by CD133-
cells, positively expressed ALDH1. Conclusion CD133+ Colo205 colorectal cancer cells in SFM containing human recombinant
EGF and bFGF can form tumor spheres and strongly express ALDH1. ALDH1 may be one of the candidate markers of
colorectal cancer stem cells.