[Down-regulated PTTG1 expression promotes the senescence of human prostate cancer LNCaP-AI].

OBJECTIVE: To investigate the effect of the down-regulated expression of pituitary tumor-transforming gene 1 (PTTG1) on the senescence of human castration-resistant prostate cancer LNCaP-AI cells. METHODS: Human castration-resistant prostate cancer LNCaP-AI cells were induced in vitro and transfected with siRNA targeting PTTG1 (the siRNA-PTTG1 group), the reagent lip3000 only (the mock group) or siRNA negative control vector (the NC group). All the cells were cultured in fetal bovine serum (FBS) or charcoal-stripped bovine serum (CSS) and counted with the cell counting chamber. The senescence characteristics of the transfected LNCaP-AI cells were examined by senescence-associated ß-galactosidase (SA-ß-Gal) staining, and the expressions of the senescence-related ß-galactosidase-1-like proteins (Glb1), the cyclin-dependent kinase inhibitors p-21CIP1 and p-27Kip1, and the chromatin-regulating heterochromatin protein 1γ (HP1γ) were detected by Western blot. RESULTS: The expression of PTTG1 in the human prostate cancer LNCaP-AI cells was significantly reduced in the siRNA-PTTG1 group compared with those in the mock and NC groups (0.21 ± 0.01 vs 0.56 ± 0.02 and 0.61 ± 0.02, P < 0.05). Culture with FBS markedly increased while that with CSS decreased the number of LNCaP-AI cells transfected with siRNA, but both FBS and CSS enhanced the proliferation of the LNCaP-AI cells in the mock and NC groups. SA-ß-Gal staining revealed that reducing the expression of PTTG1 induced a remarkably higher positive rate of the LNCaP-AI cells in the siRNA-PTTG1 than in the mock and NC groups (ï¼»63.5 ± 2.35ï¼½% vs ï¼»11.3 ± 1.24ï¼½% and ï¼»12.4 ± 1.15ï¼½%, P < 0.05). The siRNA-PTTG1 group, in comparison with the mock and NC groups, showed a significantly down-regulated expression of PTTG1 (0.21 ± 0.01 vs 0.56 ± 0.02 and 0.61 ± 0.02, P < 0.05), but up-regulated expressions of p-21CIP1 (0.32 ± 0.03 vs 0.20 ± 0.02 and 0.21 ± 0.03, P < 0.05), p-27Kip1 (0.38 ± 0.02 vs 0.20 ± 0.03 and 0.22 ± 0.01, P < 0.05), Glb1 (0.24 ± 0.01 vs 0.13 ± 0.01 and 0.15 ± 0.01, P < 0.05), and HP1γ (0.41 ± 0.01 vs 0.26 ± 0.01 and 0.27 ± 0.02, P < 0.05) in the LNCaP-AI cells. CONCLUSIONS: Down-regulated expression of PTTG1 induces senescence of human castration-resistant prostate cancer LNCaP-AI cells.

[Downregulation of PTTG1 expression inhibits the proliferation and invasiveness and promotes the apoptosis of human prostate cancer LNCaP-AI cells].

OBJECTIVE: To investigate the effects of down-regulation of PTTG1 expression on the proliferation, invasiveness and apoptosis of androgen-independent human prostate cancer LNCaP-AI cells and their sensitivity to androgen antagonists. METHODS: Human prostate cancer LNCaP-AI cells were transfected with siRNA targeting the PTTG1 gene using the Lipofectamine 2000 transfection reagent. The proliferation, invasiveness and apoptosis of the cells were detected by MTT, Transwell assay and flow cytometry, respectively. The protein expressions of PTTG1, p-Akt, and p-ERK were determined by Western blot and the mRNA expression of PTTG1 measured by agarose gel electrophoresis. RESULTS: The siRNA expression vector markedly down-regulated the expression of PTTG1, which effectively suppressed the proliferation of the LNCaP-AI cells, with the inhibition rates of (19.47 ± 2.12), (24.01 ± 2.13) and (48.02 ± 2.22)% at 24, 48 and 72 hours, respectively, after transfection, with statistically significant differences among the three groups (P <0.05). The number of the cells passing through the polycarbonate film was remarkably decreased at 24, 48 and 72 hours (74.67 ± 9.85, 56.44 ± 8.66 and 37.33 ± 6.14) as compared with the baseline (111.11 ± 13.47) (P <0.01), while the apoptosis rate of the cells was significantly increased at 24, 48 and 72 hours (18.32 ± 0.94), (19.94 ± 1.30) and (21.73 ± 1.88)% in comparison with the baseline (ï¼»2.17 ± 0.49ï¼½%)， (P <0.05). PTTG1 siRNA combined with androgen antagonist flumatide exhibited even more significant effects in inhibiting the proliferation and promoting the apoptosis of the LNCaP-AI cells than either used alone, and in a flumatide dose-dependent manner. The inhibition and apoptosis rates of the LNCaP-AI cells treated with 50 nmol/L flumatide were (27.13 ± 3.52) and (3.94 ± 0.48)%, and those treated with siRNA + 50 nmol/L flumatide were (67.51 ± 5.13) and (19.93 ± 1.72)%, respectively, both with statistically significant differences between the two groups (P <0.05). The inhibition and apoptosis rates of the cells treated with 100 nmol/L flumatide were (43.72 ± 3.90) and (5.33 ± 0.66)%, and those treated with siRNA + 100 nmol/L flumatide were (73.19 ± 4.78) and (23.43 ± 1.76)%, respectively, both with statistically significant differences between the two groups (P <0.05). CONCLUSIONS: The siRNA expression vector can down-regulate the expression of PTTG1, which can inhibit the proliferation and invasiveness of LNCaP-AI cells, promote their apoptosis, and increase their sensibility to androgen antagonists. Suppressing the expression of PTTG1 may enhance the effect of androgen-deprivation therapy on advanced prostate cancer.

[Expression of pituitary tumor-transforming gene 1 during the development of androgen-independent prostate cancer].

OBJECTIVE: To explore the expression of pituitary tumor transforming gene 1 (PTTG1) during the transformation of prostate cancer from androgen-dependent (ADPC) to androgen-independent (AIPC). METHODS: We established an AIPC cell model LNCaP-AI by culturing the androgen-dependent LNCaP cell line in the hormone-deprived medium for over 3 months. The cell model was verified and the PTTG1 expression in the LNCaP cells was detected by Western blot and RT-PCR during hormone deprivation. RESULTS: The AIPC cell model LNCaP-AI was successfully established. The PTTG1 expression was gradually increased in the LNCaP cells with the prolonged time of hormone deprivation and the expressions of matrix metalloproteinases MMP-2 and -9 were elevated at the same time. CONCLUSIONS: The expression of PTTG1 is increased gradually in AIPC, which may be a target of gene therapy for advanced prostate cancer.