Role of Androgen Receptor in Progression of LNCaP Prostate Cancer Cells from G(1) to S Phase

BACKGROUND: The androgen receptor (AR) plays a critical role in the proliferation of prostate cancer cells. However, its mechanism of action in proliferation remains unknown. An understanding of the mechanism of AR action in proliferation may lead to the development of effective strategies for the treatment of prostate cancer. METHODOLOGY/PRINCIPAL FINDINGS: In this study we report that pulse treatment of synchronized LNCaP cells with Casodex, an AR-antagonist, for 4 hours in mid-G(1) phase was sufficient to prevent cells from entering S phase. Since the assembly of pre-replication complex (pre-RC) in G(1) is required for the progression of cells from G(1) to S phase, the effect of Casodex during mid-G(1) suggested that the role of AR in proliferation might be to regulate the assembly of pre-RC. To test this possibility, we investigated the interaction between AR and Cdc6, an essential component of pre-RC in LNCaP cells. AR co-localized and co-immunoprecipitated with Cdc6, and Casodex treatment disrupted this interaction. AR-immunoprecipitate (AR-IP) also contained cyclin E and cyclin A, which play a critical role in pre-RC assembly and cell cycle entry into S phase, and DNA polymerase-α, PCNA, and ribonucleotide reductase, which are essential for the initiation of DNA synthesis. In addition, in cells in S phase, AR co-sedimented with components of the DNA replication machinery of cells that entered S phase. CONCLUSIONS/SIGNIFICANCE: Together, these observations suggest a novel role of AR as a component of the pre-RC to exert control over progression of LNCaP cells from G(1) to S phase through a mechanism that is independent of its role as a transcription factor.