Down-regulating ribonuclease inhibitor enhances metastasis of bladder cancer cells through regulating epithelial–mesenchymal transition and ILK signaling pathway

• RI siRNA changes cell proliferation, morphology, cytoskeleton.
• RI siRNA affects cell migration, invasion and adhesion.
• RI siRNA influences the expression of proteins associated with EMT in vitro.
• RI expression is related to EMT and metastasis in clinical human bladder cancer.
• RI siRNA promotes metastasis through regulating EMT and ILK signaling pathway.

Accumulating evidences implicate that ribonuclease inhibitor (RI) plays a suppressing role in cancer development. However, the mechanisms underlying antitumor of RI remain largely unknown. Epithelial–mesenchymal transition (EMT) is regarded as a key event in tumor progression. The reports have demonstrated that EMT was implicated in metastasis of bladder cancer. Therefore, we suppose that RI might involve regulating EMT of bladder cancer. Here bladder cancer T24 cells were transfected with pGensil-1-siRNA-RI vectors. HE staining, living cell observation, Phalloidine-FITC staining of microfilament, cell adhesion, scratch migration, and Matrigel invasion were examined respectively. RI expression and colocalization with ILK were detected using confocal microscope. Proteins associated with EMT were determined with Western blotting and immunohistochemistry in vivo and in vitro. Effects of RI expression on tumor growth, metastasis and EMT related proteins in BALB/C nude mouse and clinical human bladder cancer specimens were valued with histological, immunohistochemical and immunofluorescent examination respectively. We demonstrated that down-regulating RI increased cell proliferation, migration and invasion, changed cell morphology and adhesion, and rearranged cytoskeleton by inducing EMT and ILK signaling pathway in bladder cancer cells. In addition, we showed that down-regulating RI promoted tumorigenesis and metastasis of bladder cancer in vivo. Finally, we found that bladder cancer with invasive capability had higher Vimentin, Snail, Slug and Twist as well as lower E-cadherin and RI expression in clinical human specimens. Our results suggest that RI could play a novel role in inhibiting metastasis of bladder through regulating EMT and ILK signaling pathway.

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