OBJECTIVETo examine the association between CD133 expression and invasion of gastric cancer, and to elucidate whether CD133 can promote the invasion and metastasis of gastric cancer via epithelial-mesenchymal transition (EMT).

METHODSThe CD133(+) and CD133(-) KATO-III( cells were sorted by magnetic activated cell sorting (MACS). The invasion ability was detected by Transwell method. RT-PCR and Western blot were used to detect the expression of EMT-related factors in KATO-III( cells before and after CD133 was knocked out by siRNA method. The expressions of CD133 and EMT-related proteins of cancer and adjacent normal tissues in 50 patients with gastric cancer were detected by Western blot, and correlations among protein expressions were also analyzed.

RESULTSAs compared to CD133(-) cells, the number of broken-membrane cells was significantly higher (67.7±10.5 vs. 13.3±6.8, P=0.001) and the invasion ability was stronger (P<0.05) in CD133(+) cells, while the mRNA expression levels of Snail and N-cadherin were significantly higher in CD133(+) cells (0.311±0.015 vs. 0.223±0.016, P=0.040; 0.581±0.020 vs. 0.270±0.018,P=0.004), and the protein expression levels of Snail and N-cadherin were significantly higher in CD133(+) cells as well (0.513±0.015 vs. 0.179±0.023, P=0.030; 0.538±0.028 vs. 0.202±0.032, P=0.020), but E-cadherin mRNA and protein levels were significantly lower in CD133(+) cells (0.231±0.009 vs. 0.460±0.015, P=0.040; 0.426±0.030 vs. 0.748±0.027, P=0.040). After CD133 knock-out, the expressions of Snail and N-cadherin were down-regulated (P<0.05) and the expression of E-cadherin was up-regulated (P<0.05). As compared to normal mucosal tissues, the protein expression levels of Snail, N-cadherin and CD133 in gastric cancer tissues were significantly higher(0.635±0.119 vs. 0.485±0.116, P=0.029; 0.599±0.114 vs. 0.259±0.108, P=0.020; 0.754±0.154 vs. 0.329±0.134, P=0.001), while the protein expression of E-cadherin in gastric cancer tissues was lower (0.378±0.123 vs. 0.752±0.156, P=0.003). The protein expressions of Snail and N-cadherin were positively correlated with CD133 expression (r=0.278, P=0.048; r=0.406, P=0.003) and the protein expression of E-cadherin was negatively correlated with CD133 expression (r=-0.504, P=0.000).

CONCLUSIONCD133(+) cells in primary lesion of gastric cancer have relatively higher invasion ability, which may promote the metastasis of gastric cancer via up-regulation of EMT-related factors.