Surgically resected human tumors reveal the biological significance of the gastric cancer stem cell markers CD44 and CD26

Cancer tissue is maintained by relatively small populations of cancer stem cells (CSCs), which are involved in chemotherapy resistance, recurrence and metastasis. As tumor tissues are comprised of various cells, studies of human clinical samples are important for the characterization of CSCs. In the present study, an expression profiling study was performed in which an anti-cell surface marker antibody-based array platform, a flow cytometry-based cell separation technique and a tumorigenicity analysis in immunodeficient animals were utilized. These approaches revealed that the markers cluster of differentiation (CD)44 and CD26 facilitated the fractionation of surgically resected human gastric cancer (GC) cells into the following subset populations with distinct tumorigenic potentials: Highly tumorigenic CD26(+)CD44(+) cells (6/6 mice formed tumors), moderately tumorigenic CD26(+)CD44(-) cells (5/6 mice formed tumors), and weakly or non-tumorigenic CD26(-)CD44(-) cells (2/6 mice formed tumors). Furthermore, exposure to 5-fluorouracil significantly increased the proportion of CD26(+) cells in vitro. The present study demonstrated that the combined expression of CD26 and CD44 presents a potential marker of human GC stem cells.