Objective:To identify the androgen-responsive genes in prostate and screen the molecular targets for further studying human prostate cancer. Methods:The potential androgen-responsive gene pituitary tumor transforming gene 1 (PTTG1) was selected which had been previously screened by cDNA microarray in rat prostate and its mRNA level was detected by Northern blot in the castrated rat prostate with and without replacement of Mibolerone. Immunohistochemistry was performed to determine the expression and location of PTTG1 in human prostate tissues. Then human androgen-dependent prostate cancer cells LNCaP were used as a model to study the regulation of PTTG1 by Mibolerone. Results: PTTG1 mRNA was hardly detectable in the prostate of 7-day castrated rats, while it was up-regulated dramatically in the prostate of 7-day castrated rats treated with Mibolerone for 2 days. It was showed that high expression of PTTG1 was localized to the epithelial cells of human prostate cancer but not to the stromal cells with Immunohistochemistry. Northern blot analysis indicated that LNCaP cells treated with 0.1 nmol/L Mibolerone for 2 days led to the high PTTG1 mRNA expression. The basic expression of PTTG1 in human androgen-independent prostate cancer cell lines PC3 or DU145 was even higher than that in the human androgen-dependent prostate cancer cells LNCaP treated with Mibolerone. Conclusion: Androgen can up-regulate the PTTG1 expression in castrated rat prostate and human prostate cancer cell LNCaP. It suggests that PTTG1 is potential to play an important role in human prostate cancer progression.