Alpha-methylacyl-CoA racemase (AMACR) expression in normal prostatic glands and high-grade prostatic intraepithelial neoplasia (HGPIN): association with diagnosis of prostate cancer.

BACKGROUND

Alpha-methylacyl-CoA racemase (AMACR) is strongly expressed in prostate cancer with variable expression in high-grade prostatic intraepithelial neoplasia (HGPIN) and low expression in normal prostate. We examined whether AMACR expression in HGPIN and normal tissue was associated with subsequent diagnosis of cancer or proximity to a cancer focus.

METHODS

Needle core biopsies from 45 patients with isolated HGPIN, 12 radical prostatectomy (RP) specimens with prostatic carcinoma and 6 cystoprostatectomies without prostatic carcinoma were immunostained for AMACR. Among patients with HGPIN, 23 (cases) showed cancer on a later biopsy and 22 (controls) had no cancer with at least 3 consecutive negative biopsies.

RESULTS

In the biopsy set, the mean AMACR expression per gland in the normal compartment of the cases (0.29) was significantly higher than the controls (0.21) (P = 0.0006). In the RP set, normal glands near a cancer focus had higher mean AMACR expression than those that were distant (P = 0.0006). There was no difference within the HGPIN compartment between cases and controls in the biopsies, or between near and distant glands in the RP set. Mean AMACR staining of normal glands in the cystoprostatectomy specimens was significantly lower than in normal glands in close proximity to a cancer focus.

CONCLUSIONS

Higher expression of AMACR in normal glands near a focus of cancer, as well as in the subjects eventually showing cancer, suggests a possible field effect in prostatic carcinogenesis. AMACR expression in normal glands therefore might be a useful predictor for repeat biopsy outcomes or as an intermediate endpoint in chemoprevention studies.