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The mRNA for alpha-methylacyl CoA racemase (AMACR or P504S) has recently been shown by means of high-troughput gene expression profiling to be overexpressed in prostate carcinomas (PCa) as compared with benign and normal prostate epithelial cells. In the meantime several immunohistochemical studies have reported the usefulness of anti-AMACR/P504S for detecting prostate cancer in the full range of prostate specimens encountered in surgical pathology, e.g. needle biopsies, transurethral resection of prostate chips, or postatectomies and it is believed to become at least a standard adjunctive stain for atypical prostate biopsies. The enzyme is involved in the conversion of R-stereoisomers of branched-chain fatty acids to S-stereoisomers (racemization), therefore linking it to dietary risk factors for prostate cancer. Its precise role, if any, in prostate carcinogenesis remains to be elucidated. We tested the feasability/usefulness of real-time RT-PCR for specific and sensitive detection of AMACR transcripts to aid in the discrimination between malignant and benign lesions in prostatic tissues. Total RNA was isolated from snap-frozen chips of 28 cases of BPH and from 43 cases of frozen sections of prostatectomies. The latter were analyzed by an uropathologist (J.K.) to contain at least 50% malignant epithelia. Relative quantification of AMACR transcripts was performed on the LightCycler instrument using hybridization probes for detection and porphobilinogen deaminase transcripts (PBGD) for normalization. Normalized AMACR transcript levels from 41 of 43 PCa cases were increased 28-fold on average when compared to 28 cases of BPH, where only two cases displayed detectable levels of AMACR expression. This amounts to 95,3% sensitivity and 92,9% specificity which is comparable to data obatined by immmunohistochemistry. AMACR expression levels among PCa cases were not statistically associated with tumor and lymphnode stage, grading, surgical margins, and Gleason score, respectively. The present study demonstrates the usefulness of quantitative AMACR RNA transcript detection in prostatic tissues as an alternative to immunological staining techniques. Since the latter ones clearly dominate in routine laboratory use, PCR-based detection of AMACR might be a suitable future tool for detecting and monitoring prostate cancer patients. It may also be applicable to smallest amounts of needle biopsies.

[Proc Amer Assoc Cancer Res, Volume 46, 2005]