| Silencing of the pi-class glutathione S-transferase (GSTP1) gene, by CpG island hypermethylation, is the most common genetic alteration in human prostate cancer. LNCaP human prostate cancer cells, which carry hypermethylated CpG island alleles, are devoid of GSTP1 polypeptides. To ascertain the effects of GSTP1 expression on the regulation of other genes in LNCaP cells, we have used filter and glass cDNA microarray experiments containing 4,324 and 16,128 genes, respectively, to profile the transcriptomes of LNCaP cells and LNCaP cells transfected with GSTP1 cDNA. Among several candidate genes exhibiting altered expression in the GSTP1-expressing LNCaP cells, and further verified by quantitative RT-PCR and Northern blot, proteolipid protein 2 (PLP2), encoding a putative integral membrane protein which has been postulated to play a role in cell differentiation in the intestinal epithelium, has emerged.; In an attempt to detail the PLP2 protein expression patterns amongst the assayed cell lines, Western blotting and immunohistochemistry were carried out. There appeared to be no identifiable PLP2 expression in any of the GSTP1-transfected LNCaP cells. Using methylation specific PCR it was determined that the PLP2 promoter is hypermethylated in the transfected cells uncovering a possible novel function for GSTP1 in regulating gene expression in prostate cells. |
