Expression and initial promoter characterization of PCAN1 in retinal tissue and prostate cell lines.

Prostate cancer is the most frequently diagnosed neoplasia in men and one of the leading causes of cancer-related deaths in men over 60. In an effort to understand the molecular events leading to prostate cancer, we have identified PCAN1 (prostate cancer gene 1) (also known as GDEP), a gene that is highly expressed in prostate epithelial tissue and frequently mutated in prostate tumors. Here we demonstrate its expression in neural retina, and retinoblastoma cell culture but not retinal pigment epithelial cell culture. We further characterize PCAN1 expression in the prostate cell lines RWPE1, RWPE2, and LnCAP FGC. We demonstrate an increase in expression when the cells are grown in the presence of Matrigel, an artificial extracellular basement membrane. Expression was time dependent, with expression observed on d 6 and little or no expression on d 12. Testosterone was not found to increase PCAN1 expression in this culture system. In addition, normal prostate epithelial cells co-cultured with normal prostate stromal cells did not exhibit PCAN1 expression at any time. To definitively locate the transcription initiation sites, we performed restriction-ligase-mediated 5' RACE, to selectively amplify only mRNA with a 5' cap. An initial characterization of the sequence upstream of the initiation sites determined six possible binding sites for the prostate specific regulatory protein NKX3.1 and four potential binding sites for the PPAR/RXR heterodimer that is involved in the control of cell differentiation and apoptosis.