CD133(+) cells had higher in聽vivo tumor-forming ability than CD133(鈭? cells, and in culture, they progressively differentiated into CD133(鈭? cells, but not vice-versa. On the other hand, CD133(鈭? cells were more resistant to 5-fluorouracil (FU) treatment than CD133(+) cells, and it was found to be dependent on the higher expression of 脽1-integrins, and consequently, higher ability to bind collagen. Disruption of the 脽1-integrin function abrogated the chemoresistance.
From the present results, we concluded that colorectal cancer CD133(+) cells, although showing some features of CSCs, are not more resistant to 5-FU than CD133(鈭? cells. Therefore, definite conclusions can not be drawn yet, but it is strongly suggestive that CD133 should not be used as a single CSC marker of colorectal cancer.