Diagnostic biomarkers of prostate cancer.

Diagnostic tissue biomarkers for prostate cancer (PC) include basal cell markers and α-methylacyl-coenzyme A-racemase (AMACR), often used in combination. Their sensitivity and specificity are not perfect and there is a need for additional diagnostic biomarkers for PC in cases that are difficult to diagnose on routine stained sections. This study investigated the diagnostic accuracy of three novel tissue biomarkers for PC found through a search in the Human Protein Atlas database ( www.proteinatlas.com ): somatic cytochrome c (CYCS), intestinal cell kinase (ICK) and inhibitor of nuclear factor-κB kinase subunit beta (IKBKB), and compared the results with AMACR. A tissue microarray was constructed from 40 consecutive radical prostatectomy (RP) specimens including benign prostatic tissue, atrophy, high-grade prostatic intraepithelial neoplasia (HGPIN) and PC. Immunoreactivity was scored based on staining intensity and extent. Real-time polymerase chain reaction (PCR) was performed on malignant and benign frozen tissue samples from 32 RP specimens. All four biomarkers showed a stronger expression in PC and HGPIN than in benign tissue (p < 0.001). The highest diagnostic accuracy for PC was achieved with ICK and AMACR at 97%. The area under the curve for CYCS, ICK, IKBKB and AMACR was 0.859, 0.997, 0.865 and 0.983, respectively. The presence of mRNA transcripts of the genes was confirmed by real-time PCR in benign and malignant prostatic tissue. AMACR is an accurate diagnostic tissue marker for PC. However, in some PCs AMACR is false negative and a panel of CYCS, ICK and IKBKB may serve as ancillary diagnostic tool.