Objective: To 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).
Methods: The 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.
Results: As 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).
Conclusion: CD133(+) 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.