ERG and prostate cancer: Many of the prostate cancer markers are also expressed by non-prostatic cell types, for example, AMACR in kidney tubule cells [27], CRISP3 in the secretory epithelium of male genital tract [28], ERG mRNA and protein in endothelial cells (although ERG fusion is specific to prostate cancer) [29], HPN in epididymis and seminal vesicle (The Human Protein Atlas, http://www.proteinatlas.org), AGR2 in the urothelium and kidney tubule cells (The Human Protein Atlas and unpublished data).