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Rodent PSP94 Gene Expression Is More Specific to the Dorsolateral Prostate and Less Sensitive to Androgen Ablation than Probasin¹

Department of Surgery (Y.I., T.O., J.L.C., J.W.X.), Microbiology and Immunology (J. K.) and Pathology (M.M., J.K.), University of Western Ontario, London, Ontario, Canada N6A 4G5; Department of Anatomy, Hong Kong Chinese University (F.L.C.), Hong Kong, China; and Department of Urology, Nagasaki University School of Medicine (Y.I., T.O., H.S.), Nagasaki 852-8501, Japan

Address all correspondence and requests for reprints to: Jim W. Xuan, Urology Research Laboratory, London Health Sciences Center, 375 South Street, London, Ontario, Canada N6A 4G5. E-mail: jim.xuan{at}lhsc.on.ca

To date, the rodent ventral prostate (VP) has been the focus of many studies on androgen action, less attention has been directed to the lateral prostate (LP) and the dorsal prostate (DP). The rodent VP has no clear homologous counterpart in the human prostate. The rodent LP and DP is the only prostate lobe comparable to the peripheral zone of the human prostate, where hormone-induced prostate cancer mainly occurs. To explore its utility for prostate targeting, we have studied the gene expression of PSP94 with rat probasin (rPB), a gene commonly used for prostate targeting in prostate cancer research and a gene typically responsive to androgen regulation. Firstly, we demonstrated PSP94 gene transcription being more specific to the LP and DP lobes than rPB, where rPB RNA was detected in the LP and DP and other lobes at different levels. Secondly, we found that PSP94 gene transcription decreased relatively slowly in response to androgen deprivation but recovered rapidly in response to testosterone replacement after complete ablation of PSP94 transcription. In the VP, gene transcripts of rPB were specifically responsive to androgen deprivation; however, they responded relatively slowly in the LP and DP. RNase protection experiments indicated that the slow response was not due to abnormal persistence of PSP94 messenger RNA specifically in the DP and LP lobes in comparison with rPB. Thirdly, Western blot analysis revealed that both PSP94 and rPB expression is specific to the LP and DP at the protein level, exhibiting slow responses to testosterone replacement after castration. We conclude that PSP94 gene expression at the transcriptional level is more specific to the LP and DP than rPB and thus less sensitive to androgen ablation. This may have clinical implications for strategies to target the prostate in cancer therapy.