Snail1 expression in colorectal cancer and its correlation with clinical and pathological parameters

Background: Snail1 is a transcription regulator of E-cadherin. The loss of E-cadherin seems to be a crucial step in the process of Epithelial-mesenchymal transition (EMT). EMT initiates invasion and proliferation in many tumours. Overexpression of Snail1 is known to be associated with poor outcome in several solid tumours. The aim of this study was to analyse its expression profile and prognostic significance in colorectal cancer. Methods: Tissue microarrays (TMA) containing paraffin-embedded primary colorectal cancer (CRC) tissue samples from 251 patients were used in this study. The expression of Snail1 and E-cadherin was assessed by immunohistochemistry in different tumour compartments, corresponding lymph node metastases and normal colonic mucosa. Intensity of staining was classified according to the Remmele score (standardized scoring system) as well as the semiquantitative score established by Blechschmidt et al. Results: Snail1 expression was observed in 76% of the CRC. Loss of E-cadherin was noted in 87% of the CRC. Snail1 positive tumours were significantly correlated with Snail1 positive lymph node metastases (p=0.03). There was no significant correlation between loss of E-cadherin and Snail1 expression, or between N-stage or grading and Snail1 expression. Kaplan-Meier survival analysis identified no prognostic impact of Snail1 expression on overall survival. Conclusion: Snail1 expression was detectable in most of the CRC but showed no significant association with E-cadherin loss, clinical pathological characteristics or overall survival. The observed loss of E-cadherin could be explained by effects of other important EMT pathways, such as the Wnt-signalling cascade.