AIMTo determine the effects of the functional domain of saposin C (neurotrophic peptide [NP]) on androgen receptor (AR) expression and transcriptional activity.

METHODSWe constructed DNA vectors expressing NP or a chimeric peptide of the viral TAT transduction domain and NP (TAT-NP) using gene cloning technology. The effects of ectopic expression of NP or TAT-NP on cell growth were examined by 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay. Reverse transcription-polymerase chain reaction (RT-PCR), Western blot, transient transfection and reporter gene assays were used to determine the effects of NP on AR expression and activation.

RESULTSNP stimulated proliferation of androgen responsive LNCaP cells in the absence of androgens. RT-PCR and Western blot analyses showed that ectopic expression of NP resulted in induction of AR gene expression, and that the NP-stimulated expression of AR could be synergistically enhanced in the presence of androgens. Furthermore, reporter gene assay results showed that NP could enhance AR transactivation by increasing androgen-inducible gene reporter activity.

CONCLUSIONWe provided evidence that ectopic expression of saposin C-originated NP could upregulate AR gene expression and activate the AR transcriptional function in an androgen-independent manner in prostate cancer cells.

Cell Division ; Cell Line, Tumor ; DNA, Neoplasm ; genetics ; Gene Expression Regulation, Neoplastic ; Genetic Vectors ; Humans ; Kinetics ; Male ; Nerve Growth Factors ; genetics ; Pancreatic Neoplasms ; genetics ; pathology ; RNA, Messenger ; genetics ; Receptors, Androgen ; genetics ; Restriction Mapping ; Reverse Transcriptase Polymerase Chain Reaction ; Saposins ; metabolism ; Transcription, Genetic ; Up-Regulation

AIMTo further uncover the possible mechanism of quercetin-mediated inhibitory effect on prostate cancer cells.

METHODSThe cell extracts treated with quercetin or without treatment were used for checking protein expression levels of c-Jun and cAMP response element binding protein (CREB)-binding protein (CBP) by Western blotting assay. Regulatory effects of c-Jun and CBP on the function of androgen receptor (AR) were examined by cotransfection experiment. Finally, a physical interaction of c-Jun and the AR was investigated by coimmunoprecipitation.

RESULTSQuercetin dramatically induced the protein expression of c-Jun which in turn inhibited the AR function. Meanwhile, quercetin had no detectable effect on CBP expression, and the results of transient transfection demonstrated that the ectopic CBP stimulated the transcriptional activity of AR, whereas CBP-mediated stimulation could be attenuated by quercetin. Furthermore, physical interaction of c-Jun and the AR was confirmed by coimmunoprecipitation result.

CONCLUSIONOverexpression of c-Jun induced by quercetin had inhibitory effect on the function of AR protein, and increased CBP expression did not reverse the inhibition by quercetin. Together, quercetin-mediated inhibition on the AR function might be not by competition with limited amount of CBP in the cell, but through a direct association of c-Jun and the AR.

Antineoplastic Agents, Phytogenic ; pharmacology ; CREB-Binding Protein ; genetics ; metabolism ; physiology ; Cell Line, Tumor ; Humans ; Immunoprecipitation ; Male ; Prostatic Neoplasms ; metabolism ; pathology ; Protein Binding ; drug effects ; Proto-Oncogene Proteins c-jun ; genetics ; metabolism ; physiology ; Quercetin ; pharmacology ; Receptors, Androgen ; genetics ; physiology ; Transfection