Expression and prognostic significance of a comprehensive epithelial-mesenchymal transition gene set in renal cell carcinoma.

PURPOSE: Epithelial-mesenchymal transition enhances tumor cell motility and has a critical role in invasion and metastasis in a number of carcinomas. A set of transcription factors acts as a master regulator of the epithelial-mesenchymal transition process. To our knowledge it is unknown whether epithelial-mesenchymal transition is important for clear cell renal cell carcinoma progression. Therefore, we comprehensively assessed mRNA levels of epithelial-mesenchymal transition associated genes in renal cell carcinoma as well as their prognostic relevance. MATERIALS AND METHODS: We determined the expression of a set of 46 epithelial-mesenchymal transition related genes by oligonucleotide microarray and gene set enrichment analyses using RNA from 14 samples each of normal kidneys, and G1 and G3 primary renal cell carcinomas. Expression of select epithelial-mesenchymal transition genes was validated by real-time polymerase chain reaction in normal kidneys, primary renal cell carcinomas and metastases in an independent cohort of 112 patients. Results were combined with followup data for survival analysis. RESULTS: The epithelial-mesenchymal transition gene set was preferentially expressed in primary renal cell carcinoma compared to normal tissue (false discovery rate 0.01). No difference was found between G1 and G3 tumors. Quantitative reverse transcriptase-polymerase chain reaction revealed down-regulation of critical epithelial-mesenchymal transition genes such as CDH2 and ZEB1 in metastases, suggesting epithelial-mesenchymal transition reversal during metastasis. Kaplan-Meier analysis demonstrated a better outcome in patients with low CXCR4, vimentin, fibronectin and TWIST1 mRNA levels. Multivariate analyses revealed that CXCR4 and VIM up-regulation represents an independent prognostic marker for poor cancer specific survival in patients with renal cell carcinoma. CONCLUSIONS: Taken together, our data provide strong evidence that epithelial-mesenchymal transition occurs in renal cell carcinoma. Thus, interference with epithelial-mesenchymal transition in renal cell carcinoma might represent a future therapeutic option.