STEAP1 and pachyonychia congenita: The STEAP1 mRNA was highly expressed in the prostate and kidney but low in the brain, bladder, stomach, and testis, as shown in Figure 1A. Then, we evaluated the STEAP1 mRNA and protein expression in normal prostate tissues, prostatic intraepithelial neoplasia (PIN), prostate cancer (PC), and prostate cancer cell lines.