Expression of macrophage inhibitory cytokine-1 in prostate cancer bone metastases induces osteoclast activation and weight loss.
BACKGROUND
Macrophage inhibitory cytokine-1 (MIC-1) belongs to the bone morphogenic protein/transforming growth factor-beta (BMP/TGF-beta) superfamily. Serum MIC-1 concentrations are elevated in patients with advanced prostate cancer. The effects of MIC-1 on prostate cancer bone metastases are unknown.


METHODS
In vitro effects of MIC-1 on osteoblast differentiation and activity were analyzed with alkaline phosphatase and mineralization assays; osteoclast numbers were counted microscopically. MIC-1 effects on TLR9 expression were studied with Western blotting. Human Du-145 prostate cancer cells were stably transfected with a cDNA encoding for mature MIC-1 or with an empty vector. The in vivo growth characteristics of the characterized cells were studied with the intra-tibial model of bone metastasis. Tumor associated bone changes were viewed with X-rays, histology, and histomorphometry. Bone formation was assayed by measuring serum PINP.


RESULTS
MIC-1 induced osteoblast differentiation and activity and osteoclast formation in vitro. These effects were independent of TLR9 expression, which was promoted by MIC-1. Both MIC-1 and control tumors induced mixed sclerotic/lytic bone lesions, but MIC-1 increased the osteolytic component of tumors. Osteoclast formation at the tumor-bone interface was significantly higher in the MIC-1 tumors, whereas bone formation was significantly higher in the control mice. At sacrifice, the mice bearing MIC-1 tumors were significantly lighter with significantly smaller tumors.


CONCLUSIONS
MIC-1 up-regulates TLR9 expression in various cells. MIC-1 stimulates both osteoblast and osteoclast differentiation in vitro, independently of TLR9. MIC-1 over-expressing prostate cancer cells that grow in bone induce osteoclast formation and cachexia.
Wakchoure
Savita
S
Division of Hematology-Oncology, Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama 35294-3300, USA.
Swain
Telisha Millender
TM
Hentunen
Teuvo A
TA
Bauskin
Asne R
AR
Brown
David A
DA
Breit
Samuel N
SN
Vuopala
Katri S
KS
Harris
Kevin W
KW
Selander
Katri S
KS
D000818:Animals; D001859:Bone Neoplasms / Q000235:genetics / Q000473:pathology / Q000556:secondary*; D002460:Cell Line; D045744:Cell Line, Tumor; D015972:Gene Expression Regulation, Neoplastic; D055436:Growth Differentiation Factor 15 / Q000235:genetics*; D006801:Humans; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D009362:Neoplasm Metastasis / Q000235:genetics*; D010006:Osteoblasts / Q000502:physiology; D010010:Osteoclasts / Q000502:physiology*; D011471:Prostatic Neoplasms / Q000473:pathology*; D051217:Toll-Like Receptor 9 / Q000172:deficiency / Q000235:genetics; D015431:Weight Loss / Q000235:genetics*
C526140:GDF15 protein, human; D055436:Growth Differentiation Factor 15; C495370:Tlr9 protein, mouse; D051217:Toll-Like Receptor 9