Human osteocalcin and bone sialoprotein mediating osteomimicry of prostate cancer cells: role of cAMP-dependent protein kinase A signaling pathway.
Osteocalcin and bone sialoprotein are the most abundant noncollagenous bone matrix proteins expressed by osteoblasts. Surprisingly, osteocalcin and bone sialoprotein are also expressed by malignant but not normal prostate epithelial cells. The purpose of this study is to investigate how osteocalcin and bone sialoprotein expression is regulated in prostate cancer cells. Our investigation revealed that (a) human osteocalcin and bone sialoprotein promoter activities in an androgen-independent prostate cancer cell line of LNCaP lineage, C4-2B, were markedly enhanced 7- to 12-fold in a concentration-dependent manner by conditioned medium collected from prostate cancer and bone stromal cells. (b) Deletion analysis of human osteocalcin and bone sialoprotein promoter regions identified cyclic AMP (cAMP)-responsive elements (CRE) as the critical determinants for conditioned medium-mediated osteocalcin and bone sialoprotein gene expression in prostate cancer cells. Consistent with these results, the protein kinase A (PKA) pathway activators forskolin and dibutyryl cAMP and the PKA pathway inhibitor H-89, respectively, increased or repressed human osteocalcin and bone sialoprotein promoter activities. (c) Electrophoretic mobility shift assay showed that conditioned medium-mediated stimulation of human osteocalcin and bone sialoprotein promoter activities occurs through increased interaction between CRE and CRE-binding protein. (d) Conditioned medium was found to induce human osteocalcin and bone sialoprotein promoter activities via increased CRE/CRE-binding protein interaction in a cell background-dependent manner, with marked stimulation in selected prostate cancer but not bone stromal cells. Collectively, these results suggest that osteocalcin and bone sialoprotein expression is coordinated and regulated through cAMP-dependent PKA signaling, which may define the molecular basis of the osteomimicry exhibited by prostate cancer cells.
Huang
Wen-Chin
WC
Molecular Urology and Therapeutics Program, Department of Urology and Winship Cancer Institute, Emory University School of Medicine, Atlanta, GA 30322, USA.
Xie
Zhihui
Z
Konaka
Hiroyuki
H
Sodek
Jaro
J
Zhau
Haiyen E
HE
Chung
Leland W K
LW
D001483:Base Sequence; D050882:CREB-Binding Protein; D045744:Cell Line, Tumor; D017077:Culture Media, Conditioned; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D058574:Integrin-Binding Sialoprotein; D008297:Male; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000378:metabolism; D015675:Osteocalcin / Q000096:biosynthesis* / Q000235:genetics; D011401:Promoter Regions, Genetic; D011471:Prostatic Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D012795:Sialoglycoproteins / Q000096:biosynthesis* / Q000235:genetics; D015398:Signal Transduction / Q000502:physiology; D015534:Trans-Activators / Q000378:metabolism
D017077:Culture Media, Conditioned; C546871:IBSP protein, human; D058574:Integrin-Binding Sialoprotein; D009687:Nuclear Proteins; D012333:RNA, Messenger; D012795:Sialoglycoproteins; D015534:Trans-Activators; D015675:Osteocalcin; D050882:CREB-Binding Protein; C494363:CREBBP protein, human; D017868:Cyclic AMP-Dependent Protein Kinases