E2F activity is biphasically regulated by androgens in LNCaP cells.
Androgens exert a peculiar biphasic dose-dependent influence on the proliferation of LNCaP cells, a widely used model to study androgen effects on prostate cancer cells. Low concentrations of androgen stimulate proliferation, but high concentrations inhibit proliferation and induce strong expression of differentiation markers. In order to gain more insight into the molecular mechanisms that underlie these changes we studied the influence of a wide concentration range of the synthetic androgen R1881 on several cell cycle- and differentiation-related parameters. Low concentrations (0.1 nM), known to promote LNCaP cell proliferation, induce an increase of Retinoblastoma protein phosphorylation, accompanied by an increase of E2F-1 protein levels and E2F activity and by increased expression of the E2F-target gene products E2F-1 and cyclin A. High concentrations of R1881 (10 nM) induce strong expression of the differentiation marker prostate-specific antigen. Retinoblastoma protein is largely hypophosphorylated, resulting in low E2F activity and low concentrations of E2F-1 and cyclin A mRNA. Finally, there is a strong increase of p27(KIP1) protein, but not of p27(KIP1) mRNA. These results indicate that the biphasic dose response of LNCaP proliferation to androgen is closely reflected in Rb phosphorylation, E2F activity and p27(KIP1) protein expression.
Hofman
K
K
Laboratory for Experimental Medicine and Endocrinology, Catholic University of Leuven, Leuven, B-3000, Belgium.
Swinnen
J V
JV
Verhoeven
G
G
Heyns
W
W
D000728:Androgens / Q000378:metabolism* / Q000494:pharmacology; D015153:Blotting, Western; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D002455:Cell Division / Q000187:drug effects; D019925:Cyclin A / Q000378:metabolism; D050760:Cyclin-Dependent Kinase Inhibitor p27; D004268:DNA-Binding Proteins; D004305:Dose-Response Relationship, Drug; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; D004791:Enzyme Inhibitors / Q000378:metabolism; D017930:Genes, Reporter / Q000187:drug effects; D006801:Humans; D008297:Male; D015741:Metribolone / Q000494:pharmacology; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011471:Prostatic Neoplasms / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D016160:Retinoblastoma Protein / Q000378:metabolism; D056465:Retinoblastoma-Binding Protein 1; D050680:Transcription Factor DP1; D014157:Transcription Factors / Q000378:metabolism*; D014162:Transfection; D014407:Tumor Cells, Cultured; D025521:Tumor Suppressor Proteins
D000728:Androgens; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D019925:Cyclin A; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; C493753:E2F1 protein, human; D004791:Enzyme Inhibitors; D008869:Microtubule-Associated Proteins; D012333:RNA, Messenger; D016160:Retinoblastoma Protein; D056465:Retinoblastoma-Binding Protein 1; D050680:Transcription Factor DP1; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; D015741:Metribolone