CpG methylation of promoter region inactivates E-cadherin gene in renal cell carcinoma

CpG methylation in the promoter region has been shown to be important in th e regulation of genes implicated in malignant transformation. The present s tudy was designed to test the hypothesis that CpG methylation of the promot er region of the E-cadherin gene may inactivate its expression in renal cel l carcinoma, To test this hypothesis, five kidney cancer cell lines and 34 microdissected renal cell carcinoma samples were analyzed for gene and prot ein expression by reverse transcription-polymerase chain reaction and immun ohistochemistry, respectively. CpG methylation in the promoter regions of t he E-cadherin gene was analyzed by the sodium bisulfite genome sequencing t echnique. Our results show that all normal renal tissue expressed the E-cad herin gene and protein. Of the renal cancer tissues analyzed, 67% (23 of 34 ) lacked E-cadherin expression, with an associated increase in methylation, compared with normal tissue. E-cadherin gene promoter was methylated in al l renal cancer cell lines and was accompanied by a loss of E-cadherin gene and protein expression. The treatment of renal cancer cell lines with the d emethylating agent 5-aza-2'-deoxycytidine restored E-cadherin mRNA expressi on in all renal cancer cell lines. This is the first report that shows inac tivation of the E-cadherin gene and protein in renal cell carcinoma through CpG hypermethylation in the promoter region of this gene. The results of t hese experiments may contribute to an understanding of the role of E-cadher in inactivation in renal cell carcinoma. (C) 2001 Wiley-Liss, Inc.