Dickkopf-1 (DKK-1) stimulated prostate cancer growth and metastasis and inhibited bone formation in osteoblastic bone metastases.
BACKGROUND
Osteoblastic bone metastasis is the predominant phenotype observed in prostate cancer patients and is associated with high patient mortality and morbidity. However, the mechanisms determining the development of this phenotype are not well understood. Prostate cancer cells secrete several osteogenic factors including Wnt proteins, which are not only osteoinductive but also oncogenic. Therefore, the purpose of the study was to investigate the contribution of the Wnt signaling pathway in prostate cancer growth, incidence of bone metastases, and osteoblastic phenotype of bone metastases. The strategy involved overexpressing the Wnt antagonist, DKK-1, in the mixed osteoblastic and osteolytic Ace-1 prostate cancer cells.


METHODS
Ace-1 prostate cancer cells stably expressing human DKK-1 or empty vector were established and transduced with lentiviral yellow fluorescent protein (YFP)-luciferase (Luc). The Ace-1/vector(YFP-LUC) and Ace-1/DKK-1(YFP-LUC) cells were injected subcutaneously, intratibially, or in the left cardiac ventricle in athymic mice.


RESULTS
Unexpectedly, DKK-1 significantly increased Ace-1 subcutaneous tumor mass and the incidence of bone metastases after intracardiac injection of Ace-1 cells. DKK-1 increased Ace-1 tumor growth associated with increased phospho46 c-Jun amino-terminal kinase by the Wnt noncanonical pathway. As expected, DKK-1 decreased the Ace-1 osteoblastic phenotype of bone metastases, as confirmed by radiographic, histopathologic, and microcomputed tomographic analysis. DKK-1 decreased osteoblastic activity via the Wnt canonical pathway evidenced by an inhibition of T-cell factor activity in murine osteoblast precursor ST2 cells.


CONCLUSIONS
The present study showed that DKK-1 is a potent inhibitor of bone growth in prostate cancer-induced osteoblastic metastases.
M.D. Anderson Cancer Center, University of Texas, Houston, Texas, USA.
Nanda K
NK
Thudi
Chelsea K
CK
Martin
Sridhar
S
Murahari
Sherry T
ST
Shu
Lisa G
LG
Lanigan
Jillian L
JL
Werbeck
Evan T
ET
Keller
Laurie K
LK
McCauley
Joseph J
JJ
Pinzone
Thomas J
TJ
Rosol
D000818:Animals; D001859:Bone Neoplasms / Q000378:metabolism / Q000556:secondary*; D048708:Cell Growth Processes / Q000502:physiology; D045744:Cell Line, Tumor; D004285:Dogs; D006651:Histocytochemistry; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D008297:Male; D051379:Mice; D008819:Mice, Nude; D010012:Osteogenesis / Q000502:physiology; D011471:Prostatic Neoplasms / Q000378:metabolism / Q000473:pathology*; D015398:Signal Transduction; D018709:Statistics, Nonparametric; D014057:Tomography, X-Ray Computed; D051153:Wnt Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*
C501126:DKK1 protein, human; D036341:Intercellular Signaling Peptides and Proteins; D051153:Wnt Proteins