| Three genes ( IGFBP 1 , IGFBP 3 , and COL1A1 ) showed promoter methylation in tumor DNA but were unmethylated in normal cell DNA . ^^^ The IGFBP 1 , IGFBP 3 , and COL1A1 gene promoter regions were found to be frequently methylated in primary renal cell tumors , and further study will provide insight into the biology of the disease and facilitate translational studies in renal cancer . . ^^^ |