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.