SFRP5 and nonpapillary renal cell carcinoma: A study on the role of SFRP-5 and its epigenetic regulation in RCC cell lines Caki1, Caki2, ACHN, A498, and a tissue microarray consisting of 12 ccRCCs and matched adjacent tissues revealed dense methylation of SFRP-5 promoter in all RCC cell lines and ccRCC tissue samples whereas the same region in normal kidney tissue was mostly unmethylated.