Alpha-methylacyl-CoA racemase as an androgen-independent growth modifier in prostate cancer.
Alpha-methylacyl-CoA racemase (AMACR) is an enzyme involved in beta-oxidation of branched-chain fatty acids and bile acid intermediates. Recent work has identified AMACR as a new diagnostic marker for prostate cancer (PCa). The data from the present study suggest that AMACR is also functionally important for the growth of PCa cells. Overexpressed AMACR from both clinical tissues and PCa cell lines is wild type by sequence analysis and functionally active by enzymatic assay. Correspondingly, enzyme activity of AMACR increases approximately 4-fold in PCa in comparison with adjacent normal prostate. Small interference RNA (siRNA) against AMACR, but not the control inverted siRNA, reduced the expression of AMACR and significantly impaired proliferation of the androgen-responsive PCa cell line LAPC-4. No effect was observed in HeLaS3 cells, which express AMACR at a low level. Cell cycle analyses revealed a G(2)-M cell cycle arrest in LAPC-4 cells treated with siRNA compared with mock treatment or control inverted siRNA. Expression of a siRNA-resistant form of AMACR in LAPC-4 cells protects the cells from growth arrest after AMACR-specific siRNA treatment. Data from Western blotting and luciferase-based reporter assays suggest that the function and expression of AMACR are independent of androgen receptor-mediated signaling. Moreover, simultaneous inhibition of both the AMACR pathway by siRNA and androgen signaling by means of androgen withdrawal or antiandrogen suppressed the growth of LAPC-4 cells to a greater extent than either treatment alone. Taken together, these data suggest that AMACR is essential for optimal growth of PCa cells in vitro and that this enzyme has the potential to be a complementary target with androgen ablation in PCa treatment.
Zha
Shan
S
Brady Urological Institute, Johns Hopkins Medical Institutions, 600 North Wolfe Street, Baltimore, MD 21287, USA.
Ferdinandusse
Sacha
S
Denis
Simone
S
Wanders
Ronald J
RJ
Ewing
Charles M
CM
Luo
Jun
J
De Marzo
Angelo M
AM
Isaacs
William B
WB
D000726:Androgen Antagonists / Q000494:pharmacology; D000728:Androgens / Q000502:physiology; D000813:Anilides / Q000494:pharmacology; D002455:Cell Division / Q000502:physiology; D045744:Cell Line, Tumor; D006801:Humans; D008297:Male; D015741:Metribolone / Q000494:pharmacology; D009376:Neoplasms, Hormone-Dependent / Q000201:enzymology / Q000473:pathology; D009570:Nitriles; D011471:Prostatic Neoplasms / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D034741:RNA, Small Interfering / Q000235:genetics; D019998:Racemases and Epimerases / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D011944:Receptors, Androgen / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology; D045165:Testosterone Congeners / Q000494:pharmacology; D014105:Tosyl Compounds; D014162:Transfection
D000726:Androgen Antagonists; D000728:Androgens; D000813:Anilides; D009570:Nitriles; D034741:RNA, Small Interfering; D011944:Receptors, Androgen; D045165:Testosterone Congeners; D014105:Tosyl Compounds; D015741:Metribolone; C053541:bicalutamide; D019998:Racemases and Epimerases; C108352:alpha-methylacyl-CoA racemase