Significance of CD133 as a cancer stem cell markers focusing on the tumorigenicity of pancreatic cancer cell lines

PURPOSE The cancer stem cell hypothesis states that the capacity of a cancer to grow and propagate is dependent on a small subset of cells. To determine the significances of the cancer stem cell markers CD133, CD44, and CD24 using a comparative analysis with a focus on tumorigenicity. METHODS Four pancreatic cancer cell lines, Capan-1, Mia-PACA-2, Panc-1, and SNU-410 were analyzed for the expressions of CD133, CD44, and CD24 by flow cytometry. The tumorigenicity was compared using tumor volumes and numbers of tumors formed/numbers of injection in nonobese diabetic severe combined deficiency mice. Fluorescence-activated cell sorting (FACS) analysis was used to confirm that xenograft explants originated from human pancreatic cancer cells. RESULTS CD133 was positive in only Capan-1, CD44 positive in all, CD24 partially positive in Panc-1. After injecting 2 × 10(6) cells, all mice administered Capan-1 or Mia-Paca-2 developed tumors, 3 of 5 administered Panc-1 developed tumors, but no mouse administered SNU-410 developed any tumors. The volumes of Capan-1 tumors were seven times larger than those of Mia-Paca-2 tumors. When 2 × 10(5) or 2 × 10(4) of Capan-1 or Mia-Paca-2 was injected, tumors developed in all Capan-1 treated mice, but not in Mia-Paca-2 treated mice. Furthermore, xenograft explants of Capan-1 expressed CD133+CD44+ and Capan-1 injected mice developed lung metastasis. FACS analysis showed that xenograft explants originated from human pancreatic cancer cell lines. CONCLUSION CD133 positive cells have higher tumorigenic and metastatic potential than CD44 and CD24 positive cells, which suggests that CD133 might be a meaningful cell surface marker of pancreatic cancer stem cells.