Background. To detect the changes of biological characteristics in gastric cancer cells interfered by CD133-specific small interfering RNA (siRNA). Methods. First to select the siRNA which has the strongest interference effect among 3 siRNAs (i.e., siRNA1, siRNA2, and siRNA3) in KATO-III cells by RT-PCR and Western blotting assays. Then, CD133+ cells were sorted out from KATO-III cells using an immunomagnetic bead sorting method and transfected with the selected siRNA. Furthermore, the proliferating characteristics, the antichemotherapeutic assessment, Transwell invasion assay, monoclonal sphere formation assay, and subcutaneous transplanted tumor formation assay in nude mice were investigated. Results. siRNA3 showed the strongest interference effect in KATO-III cells. As compared to the uninterfered control group, the CD133+ cells treated by siRNA3 showed significant decreases in the abilities of proliferation, invasion, clone sphere formation, and resistance to antitumour drugs as well as the weight and size of the transplanted tumor, which was nearly similar to that of CD133？ cells. Additionally, the protein expression level of the EMT factor E-cadherin increased while those of EMT-related Snail and N-cadherin decreased in CD133+ cells interfered by siRNA3. Conclusion. Inhibition of CD133 gene expression reduces the abilities of gastric cancer cells in proliferation, invasion, clonal sphere formation, and chemoresistance as well as tumor formation in nude mice. 1. Introduction Gastric cancer (GC) is characterized by high incidences of recurrence and metastasis and low chemosensitivity, whose 5-year survival rate remains less than 24% [1]. Presently, the mechanisms of GC development and progression, invasion and metastasis, and recurrence are not fully understood. In accordance with the hypothesis of tumor-initiating cells (TICs) [2], TICs have the potential of self-renewing, active proliferation, high tumorigenicity, and multidifferentiation; TICs are also the primary cells resistant to radiochemotherapy [3]. Evidence shows that CD133+ cells act as TICs in a variety of solid tumors [4–7]. The CD133 expression level in GC tissues is significantly higher than that in the adjacent normal tissues. A higher CD133+ expression level is indicative of the deeper infiltration, later TNM stage, more lymph node metastases, and shorter survival time [8–10]. Several studies sorted the CD133+ cell subgroup from GC cells and further study of their biological characteristics shows that CD133+ cells have significantly higher abilities of proliferation, monoclonal
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