The expression of osteoclastogenesis-associated factors and osteoblast response to osteolytic prostate cancer cells.
BACKGROUND
Prostate cancer (PCa) has a propensity to metastasize to bone. Tumor cells replace bone marrow and can elicit an osteoblastic, osteolytic, or mixed bone response. Our objective was to elucidate the mechanisms and key factors involved in promoting osteoclastogenesis in PCa bone metastasis.


METHODS
We cultured osteoblast-like MC3T3-E1 cells with conditioned medium (CM) from PC-3 and C4-2B cells. MC3T3-E1 mineralization decreased in the presence of PC-3 CM, whereas C4-2B CM had no effect on mineralization. Using oligo arrays and validating by real-time PCR, we observed a decrease in the expression of mineralization-associated genes in MC3T3-E1 cells grown in the presence of PC-3 CM. In addition, PC-3 CM induced the expression of osteoclastogenesis-associated genes IGFBP-5, IL-6, MCP-1, and RANKL while decreasing OPG expression in MC3T3-E1 cells. Furthermore, CM from MC3T3-E1 cells cultured in the presence of PC-3 CM, in association with soluble RANKL, increased osteoclastogenesis in RAW 264.7 cells. Investigation of PCa metastases and xenografts by immunohistochemistry revealed that the osteoclastic factor IL-6 was expressed in the majority of PCa bone metastases and to a lesser extent in PCa soft tissue metastases. In vitro it was determined that soluble IL-6R (sIL-6R) was necessary for IL-6 to inhibit mineralization in MC3T3-E1 cells.


RESULTS
PC-3 cells inhibit osteoblast activity and induce osteoblasts to produce osteoclastic factors that promote osteoclastogenesis, and one of these factors, IL-6, is highly expressed in PCa bone metastases.


CONCLUSIONS
IL-6 may have an important role in promoting osteoclastogenesis in PCa bone metastasis through its' interaction with sIL-6R.
Department of Urology, University of Washington, Seattle, Washington 98195, USA. cmorriss@u.washington.edu
Colm
C
Morrissey
Janice S
JS
Lai
Lisha G
LG
Brown
Ya-Chun
YC
Wang
Martine P
MP
Roudier
Ilsa M
IM
Coleman
Roman
R
Gulati
Funda
F
Vakar-Lopez
Lawrence D
LD
True
Eva
E
Corey
Peter S
PS
Nelson
Robert L
RL
Vessella
D000818:Animals; D001859:Bone Neoplasms / Q000378:metabolism* / Q000556:secondary; D002113:Calcification, Physiologic / Q000187:drug effects / Q000235:genetics; D045744:Cell Line, Tumor; D017077:Culture Media, Conditioned / Q000494:pharmacology; D019085:Fluorescent Antibody Technique, Direct; D015870:Gene Expression / Q000187:drug effects; D020869:Gene Expression Profiling; D006801:Humans; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D008297:Male; D051379:Mice; D016513:Mice, SCID; D020411:Oligonucleotide Array Sequence Analysis; D010006:Osteoblasts / Q000378:metabolism* / Q000473:pathology; D010010:Osteoclasts / Q000378:metabolism* / Q000473:pathology; D010014:Osteolysis / Q000378:metabolism*; D011471:Prostatic Neoplasms / Q000378:metabolism* / Q000473:pathology; D013977:Tibia / Q000378:metabolism / Q000473:pathology; D046888:Tissue Array Analysis; D023041:Xenograft Model Antitumor Assays
D017077:Culture Media, Conditioned