DNA methylation and immunohistochemical analysis of the S100A4 calcium binding protein in human prostate cancer

BACKGROUND The role of DNA methylation in the transcriptional regulation of S100A4 is unknown in human prostate cancer. METHODS Critical CpG sites within intron 1 of S100A4 were sequenced in DNA obtained from prostatic adenocarcinoma, non‐malignant epithelium, and prostate cancer cell lines. S100A4 protein expression was assessed by immunohistochemistry and Western blotting. RESULTS Methylation was seen in all cases of cancer, non‐malignant epithelium, and in prostate cancer cell lines, but was absent in all cases of blood DNA. S100A4 immunoexpression was absent in all cases of malignant and non‐malignant epithelium, while strong–moderate expression was seen in the stroma and lymphocytes. Western blotting showed absent S100A4 expression in LNCaP and Du145 cells and low levels in PC‐3 cells. CONCLUSIONS S100A4 protein is not expressed in benign or malignant prostatic epithelium nor in LNCaP and Du145 cells. The mechanism underlying absent S100A4 expression in prostatic epithelium and cell lines may involve methylation. Prostate 67: 341–347, 2007. © 2007 Wiley‐Liss, Inc.