Effect of AR-V7 on endocrine therapy resistance of prostate cancer / 中国病理生理杂志

ABSTRACT

AIM:To explore the effect of androgen receptor splice variant 7 ( AR-V7 ) on endocrine therapy resistance of prostate cancer cells and the resistance mechanisms .METHODS:Four prostate cancer cell lines were trans-fected with AR-V7 siRNA ( siAR-V7) using Lipofectamine 2000 kit, and the transfected cells were named as PC 3-siAR-V7, DU145-siAR-V7, LNCaP-siAR-V7 and ArCaP-siAR-V7 cells.The prostate cancer cells transfected with negative con-trol ( NC) siRNA served as negative controls .The expression of AR-V7 at mRNA and protein levels was detected by real-time PCR and Western blot , respectively .The cell viability and cell migration rate were measured by MTT assay and Tran-swell method, respectively.The promoter activity of AR and the protein levels of targeted prostate-specific antigen (PSA) and FK506-binding protein 5 (FKBP5) were monitored by luciferase reporter gene assay and Western blot , respectively. The bicalutamide-resistant cell line, LNCaP-DR, was constructed, and the subcellular localization of AR and AR-V7 pro-teins in LNCaP, LNCaP-siAR-V7 and LNCaP-DR cells was observed by the method of immunofluorescence .The protein in-teraction of AR-V7 and heat shock protein 90 ( HSP90) was determined by co-immunoprecipitation .RESULTS:The mR-NA level of AR-V7 in the 4 prostate cancer cell lines was significantly higher than that in normal prostate epithelial cell line RWPE-1 (P<0.05).The AR-V7 level, cell viability and cell migration rate in the cells transfected with siAR-V7 were notablely lowered compared with the NC siRNA-transfected cells (P<0.05).The cell viability was gradually decreased following with the increase in bicalutamide dose , and down-regulation of AR-V7 expression significantly enhanced the sensi-tivity to bicalutamide (P<0.05).Down-regulation of AR-V7 expression significantly inhibited AR promoter activity and reduced the protein levels of PSA and FKBP5 (P<0.05).The results of immunofluorescence observation showed that most AR and AR-V7 were mainly located in the nucleus , a few AR was located in the cytoplasm , and down-regulation of AR-V7 expression inhibited AR nuclear transport .AR was entirely located in the nucleus and the protein levels of AR-V7 was sig-nificantly increased in the bicalutamide-resistant cells .The interaction of endogenous AR-V7 with HSP90 was found in the prostate cancer cells .CONCLUSION: High AR-V7 level is found in the prostate cancer cells , and down-regulation of AR-V7 expression inhibits the cell viability and migration .High AR-V7 level is related to the bicalutamide resistance .The possible mechanism is that AR nuclear transport is mediated by the interaction of AR -V7 with HSP90 to activate AR signal pathway and regulate targeted gene transcriptional activity , thus resulting in drug resistance .