Objective: Purification and characterization of cancer stem cells (CSCs) can lead to the identification of targets for therapeutic interventions of cancer. With regard to gastric cancer, studies have not yet defined and characterized CSCs.
Methods: The expression of the cell surface markers CD44 and CD24 was examined in gastric cell lines AGS and gastric cancer tissues from five patients with fluorescence-activated cell sorting analysis (FACS). The tumorigenic properties, self-renewal, and differentiated progeny in the two distinct cell populations CD44+CD24+ and CD44-CD24- were identified in vivo serial transplantation and in vitro culture. Real-time RT-PCR was used to assess the expression of sonic hedgehog (SHH), patched 1 (PTCH1), and GLI3 signaling molecules in CD44+CD24+ and CD44-CD24- cells.
Results: As few as 200 CD44+CD24+ cells injected in NOD-SCID mice were able to generate tumors in 50% of mice (6 of 12), while tumors did not form in mice until at least 10,000 CD44-CD24- cells were injected, where only one of 12 mice formed a tumor, further verifying that CD44+CD24+ gastric cancer cells have the capacity to both self-renew and produce differentiated progeny. Moreover, SHH, PTCH1, and GLI3 mRNA expression increased significantly in the CD44+CD24+ subpopulation when compared with the CD44-CD24- subpopulation.
Conclusions: These studies strongly suggest that the CD44+CD24+ subpopulation of human gastric cancer cell lines, AGS, is gastric cancer stem cells.