[Androgen receptor silencing by shRNA inhibits human prostate cancer xenograft growth in nude mice].

OBJECTIVE

To investigate the inhibitory effect of silencing androgen receptor (AR) gene by AR short-hairpin RNA (shRNA) on the growth of human prostate cancer xenograft in nude mice.

METHODS

Human 22RV1 prostate cancer cells were inoculated subcutaneously into nude mice to establish xenograft models of human prostate cancer. Meanwhile, a short-hairpin RNA that was capable of suppressing the expression of AR was constructed and then recombinant plasmids producing AR shRNA were prepared in a large number. The tumor-bearing mice were randomly divided into 2 groups: the control group and the experimental group. When the tumor volume grew to about 300 mm(3), the plasmids prepared previously were injected into the tail veins of the mice once at the dose of 2 μg/g in the experimental group, whereas the mice in the control group was injected with the same amount of saline as control. The tumor volumes were monitored every other day until 14 days after the treatment.At the endpoint,the mice were sacrificed and the tumors were excised, weighed, fixed in buffered-formalin, and embedded in paraffin for the immunohistochemical analysis of AR,Ki-67 (a marker of proliferative cell) levels and apoptotic cell labeling by TUNEL (terminal deoxynucleotidyl transterase-mediated dUTP nick end labeling) assay. A semiquantitative immunohistochemical scoring system, HSCORE system, was used to evaluate the expression of AR and proliferative index/Ki-67 labeling index (PI/Ki-67 LI) and apoptotic index (AI) were used to assess the cell proliferation and cell apoptosis, respectively.

RESULTS

Compared with the control group, the treatment induced an evident inhibitory effect on the tumor growth in the nude mice with prostate cancer. At the endpoint, the tumor volume of (1 199.56±86.48) mm(3) in the experimental group was significantly smaller than that of (1 742.02±98.16) mm3 in the control group (P=0.002). The tumor weight of (1 006.2±79.1) mg in the experimental group significantly decreased compared with that of (1 383.4±74.8) mg in the control group (P=0.005). The AR HSCORE,PI and AI in the experimental group were 25.8±6.7, (26.0±3.1)%, (55.6±7.9)%, respectively, and those in the control group were 268.8± 18.7, (87.6±7.9)%, (27.2±3.9)%, respectively. There were significant differences between the two groups (all P<0.01).

CONCLUSION

AR shRNA could be injected intravenously to suppress the expression of AR in vivo and hence inhibit the growth of human prostate cancer xenograft in nude mice.