Expression of Snail in Upper Urinary Tract Urothelial Carcinoma: Prognostic Significance and Implications for Tumor Invasion

Purpose: There are few molecular markers known to predict upper urinary tract urothelial carcinomas (UTUC) prognosis. Snail, which contributes to epithelial-mesenchymal transition (EMT), has been documented in cancer progression, but not clear yet in UTUC. We therefore addressed the expression and biological significance of Snail in UTUC.

Experimental Design: To elucidate the biological significance of Snail in UTUC, we examined the immunohistochemical expression of snail in UTUC and analyzed its clinical significance in 150 patients with UTUC. Biological effects of Snail in EMT and invasion were evaluated by using small interfering RNA (siRNA) specific for Snail in urothelial carcinoma cell lines and the Matrigel invasion assay.

Results: Nuclear Snail staining was very weak in superficial UTUC. In contrast, strong Snail staining was observed in many of the nucleus of invasive UTUC. Snail expression was significantly higher in the high tumor stage, high grade, and in tumors showing lymphovascular invasion (LVI). Multivariate Cox regression analysis revealed that elevated Snail expression was a significant and an independent prognostic predictor of recurrence-free survival and cancer-specific survival. Patients with positive LVI and high Snail expression showed the worse outcome. Targeting of Snail mRNA expression in UMUC-3 cells with Snail-specific siRNA downregulated the mRNA expression of Snail, Vimentin, MMP2, and MMP9. Furthermore, the cells with siRNA for Snail showed decreased invasion activity in comparison with the cells transfected with a nontargeting siRNA.

Conclusion: Snail-induced EMT represents a clinically relevant mechanism of UTUC progression and an attractive target for the treatment of patients with UTUC.