Osteoblasts can stimulate prostate cancer growth and transcriptionally down-regulate PSA expression in cell line models☆

Received 17 August 2009; received in revised form 24 September 2009; accepted 29 September 2009. published online 10 May 2010.
Corrected Proof

Abstract

Introduction

To investigate the effect of bone environment on cellular proliferation, mature prostate-specific antigen (PSA) production and secretion, and PSA transcriptional regulation of prostate cancer cells.

Materials and methods

Androgen-independent C4-2 prostate cancer cells were co-cultured with various osteoblastic cells in a transwell system. Proliferation was measured via cell counting and MTT assay. Lactate and PSA were determined in the conditioned media (CM). Transcriptional activity of the full-length PSA promoter (6.1 kilobases) and of 3 deletion constructs was determined via luciferase reporter assay upon exposure to CM from various osteoblastic cell lines.

Results

Osteoblastic bone cells and CM, but not control cells (fibroblast) or CM, reproducibly stimulated the proliferation of C4-2 cells. The co-culture system, PSA production by C4-2 cells transiently decreased when in co-culture with osteoblastic, but not with control cells. After abundant prostate cell proliferation, the secreted PSA levels rose exponentially. Addition of CM from osteoblastic cells, but not control cells, consistently decreased (about 3-fold) the transcriptional activity of the PSA promoter in C4-2 cells. Deletion construct analysis of the PSA promoter revealed that the transcriptional down-regulation is dually controlled by elements close to the TATA and upstream androgen responsive (AREIII) components.

Conclusions

The osteoblastic environment stimulates prostate cancer cell proliferation but reduces PSA production initially. The mechanism of PSA down-regulation is transcriptional, most likely in response to soluble factors present in the osteoblastic bone stromal cell CM. Transcriptional down-regulation appears to be mediated by elements near both the TATA box and the AREIII component.

Keywords: Osteoblast, Prostate neoplasm, Prostate-specific antigen, Metastasis, Stromal-epithelial interaction

a Department of Urology, University of Minnesota, Minneapolis, MN 55455, USA

b Molecular Urology and Therapeutics Program, Department of Urology, University of Virginia, Charlottesville, VA 22904, USA

c Department of Urology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA

d Department of Urology, University of Pittsburgh, Pittsburgh, PA 15260, USA

e Emory Winship Cancer Institute, Atlanta, GA 30322, USA

f Department of Cell Biology, University of Delaware, Newark, DE 19716, USA

g Department of Urology, Indiana University, Indianapolis, IN 46202, USA

Corresponding author. Tel.: 612-625-6401; fax: 612-6260428

☆ This work was supported in part by NIH grants CA63341 and CA63863.

1 Y.L. and R.A.S. contributed equally to this work.

2 K.S.K. was financially supported by an AFUD scholarship and NIH T32 training grant.

PII: S1078-1439(09)00297-X

doi:10.1016/j.urolonc.2009.09.016