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Journal of bone and mineral research: the official journal of the American Society for Bone and Mineral Research 11/2012; 27(11):2238-41. · 6.04 Impact Factor
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Tara C Brennan-Speranza,
Holger Henneicke,
Sylvia J Gasparini,
Katharina I Blankenstein,
Uta Heinevetter,
Victoria C Cogger,
Dmitri Svistounov,
Yaqing Zhang,
Gregory J Cooney,
Frank Buttgereit,
Colin R Dunstan,
Caren Gundberg, Hong Zhou,
Markus J Seibel
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ABSTRACT: Long-term glucocorticoid treatment is associated with numerous adverse outcomes, including weight gain, insulin resistance, and diabetes; however, the pathogenesis of these side effects remains obscure. Glucocorticoids also suppress osteoblast function, including osteocalcin synthesis. Osteocalcin is an osteoblast-specific peptide that is reported to be involved in normal murine fuel metabolism. We now demonstrate that osteoblasts play a pivotal role in the pathogenesis of glucocorticoid-induced dysmetabolism. Osteoblast-targeted disruption of glucocorticoid signaling significantly attenuated the suppression of osteocalcin synthesis and prevented the development of insulin resistance, glucose intolerance, and abnormal weight gain in corticosterone-treated mice. Nearly identical effects were observed in glucocorticoid-treated animals following heterotopic (hepatic) expression of both carboxylated and uncarboxylated osteocalcin through gene therapy, which additionally led to a reduction in hepatic lipid deposition and improved phosphorylation of the insulin receptor. These data suggest that the effects of exogenous high-dose glucocorticoids on insulin target tissues and systemic energy metabolism are mediated, at least in part, through the skeleton.
The Journal of clinical investigation 10/2012; · 15.39 Impact Factor
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Holger Henneicke,
Markus Herrmann,
Robert Kalak,
Tara C Brennan-Speranza,
Uta Heinevetter,
Nicky Bertollo,
Robert E Day,
Dörte Huscher,
Frank Buttgereit,
Colin R Dunstan,
Markus J Seibel, Hong Zhou
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ABSTRACT: The pathogenesis of glucocorticoid-induced osteoporosis remains ill defined. In this study, we examined the role of the osteoblast in mediating the effects of exogenous glucocorticoids on cortical and trabecular bone, employing the Col2.3-11βHSD2 transgenic mouse model of osteoblast-targeted disruption of glucocorticoid signalling.
Eight week-old male transgenic (tg) and wild-type (WT) mice (n=20-23/group) were treated with either 1.5 mg corticosterone (CS) or placebo for 4 weeks. Serum tartrate-resistant acid phosphatase 5b (TRAP5b) and osteocalcin (OCN) were measured throughout the study. Tibiae and lumbar vertebrae were analysed by micro-CT and histomorphometry at endpoint.
CS suppressed serum OCN levels in WT and tg mice, although they remained higher in tg animals at all time points (p<0.05). Serum TRAP5b levels increased in WT mice only. The effect of CS on cortical bone differed by site: At the endosteal surface, exposure to CS significantly increased bone resorption and reduced bone formation, resulting in a larger bone marrow cavity cross-sectional area (p<0.01). In contrast, at the pericortical surface bone resorption was significantly decreased accompanied with a significant increase in pericortical cross-sectional area (p<0.05) while bone formation remained unaffected. Vertebral cortical thickness and area were reduced in CS treatment mice. Tg mice were partially protected from the effects of exogenous CS, both on a cellular and structural level. At the CS doses used in this study, trabecular bone remained largely unaffected.
Endocortical osteoblasts appear to be particularly sensitive to the detrimental actions of exogenous glucocorticoids. The increase in tibial pericortical cross-sectional area and the according changes in pericortical circumference suggest an anabolic bone response to GC treatment at this site. The protection of tg mice from these effects indicates that both catabolic and anabolic action of glucocorticoids are, at least in part, mediated by osteoblasts.
Bone 06/2011; 49(4):733-42. · 4.02 Impact Factor
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ABSTRACT: Vitamin D is considered as an important determinant of bone turnover as well as cancer growth. Using a murine model of bone metastasis, we investigated the effect of vitamin D deficiency on prostate cancer cell growth in bone.
Three-week-old male nude mice were fed either normal chow (control) or a diet deficient in vitamin D. The latter diet resulted in severe hypovitaminosis D within 6 weeks. At this point of time, 5 × 10(4) cells of the prostate cancer cell line, PC-3, were injected either into the bone marrow (tibia) or subcutaneously into soft tissues. Osteoprotegerin (OPG) was co-administered in subgroups of mice to suppress bone remodeling. Osteolytic lesions were monitored by serial X-ray, while soft tissue tumor growth was measured by caliper. All tissues were analyzed by micro-CT and histology at endpoint.
Bone turnover was significantly accelerated in vitamin D deficient compared to vitamin D sufficient mice from week 6 onwards. Intra-tibially implanted PC-3 cells resulted in mixed osteolytic and osteosclerotic lesion. At endpoint, osteolytic and osteosclerotic lesion areas, total tumor area, and tumor mitotic activity were all significantly increased in vitamin D deficient mice compared to controls. Regardless of diet, OPG reduced bone turnover, total tumor, and osteosclerotic area as well as tumor mitotic activity, while promoting cell apoptosis. In contrast, vitamin D deficiency did not alter tumor growth in soft tissues.
Vitamin D deficiency stimulates prostate cancer growth in bone through modulating the bone microenvironment.
The Prostate 06/2011; 71(9):1012-21. · 3.48 Impact Factor
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ABSTRACT: Metastasis of cancer to bone is one of the most significant causes of morbidity and often indicates poor prognosis particularly
for breast cancer, prostate cancer, and lung cancer patients. Animal models are important tools to investigate the pathogenesis
of, and develop novel treatment strategies for, bone metastases in humans. The ideal animal model of bone metastatic human
cancer would reproduce the genetic and phenotypic changes that occur with human cancers.
05/2011: pages 83-91;
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Ulla Simanainen,
Anita Lampinen,
Holger Henneicke,
Tara C Brennan,
Uta Heinevetter,
D Tim Harwood,
Keely McNamara,
Markus Herrmann,
Markus J Seibel,
David J Handelsman, Hong Zhou
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ABSTRACT: Glucocorticoids influence prostate development and pathology, yet the underlying mechanisms including possible direct glucocorticoid effect on the prostate are not well characterized.
We evaluated the expression of the glucocorticoid receptor (GR) together with the effects of supraphysiological glucocorticoid (corticosterone) on mouse prostate morphology and epithelial proliferation. Mature male mice were treated by weekly subdermal implantation of depot pellets containing either 1.5 mg corticosterone or placebo providing steady-state release for 4 weeks.
Corticosterone treatment significantly increased dorsolateral and anterior prostate weights as well as prostate epithelial cell proliferation while epithelial apoptosis remained low upon corticosterone treatment. Histological analysis of the anterior lobe demonstrated abnormal, highly disorganized luminal epithelium with frequent formation of bridge-like structures lined by continuous layer of basal cells not observed following placebo treatment. Molecular analysis revealed corticosterone-induced increase in expression of stromal growth factor Fgf10 which, together with prominent stromal GR expression, suggest that glucocorticoid modify stromal-to-epithelial signaling in the mouse prostate. The mitogenic effects were prostate specific and not mediated by systemic effects on testosterone production suggesting that corticosterone effects were primarily mediated via prostate GR expression.
These data demonstrate that murine prostate is significantly and directly influenced by corticosterone treatment via aberrant stromal-to-epithelial growth factor signaling.
The Prostate 02/2011; 71(3):289-97. · 3.48 Impact Factor
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ABSTRACT: Elevated follicle-stimulating hormone (FSH) activity is proposed to directly cause bone loss independent of estradiol deficiency in aging women. Using transgenic female mice expressing human FSH (TgFSH), we now reveal that TgFSH dose-dependently increased bone mass, markedly elevating tibial and vertebral trabecular bone volume. Furthermore, TgFSH stimulated a striking accrual of bone mass in hypogonadal mice lacking endogenous FSH and luteinizing hormone (LH) function, showing that FSH-induced bone mass occurred independently of background LH or estradiol levels. Higher TgFSH levels increased osteoblast surfaces in trabecular bone and stimulated de novo bone formation, filling marrow spaces with woven rather than lamellar bone, reflective of a strong anabolic stimulus. Trabecular bone volume correlated positively with ovarian-derived serum inhibin A or testosterone levels in TgFSH mice, and ovariectomy abolished TgFSH-induced bone formation, proving that FSH effects on bone require an ovary-dependent pathway. No detectable FSH receptor mRNA in mouse bone or cultured osteoblasts or osteoclasts indicated that FSH did not directly stimulate bone. Therefore, contrary to proposed FSH-induced bone loss, our findings demonstrate that FSH has dose-dependent anabolic effects on bone via an ovary-dependent mechanism, which is independent of LH activity, and does not involve direct FSH actions on bone cells.
Proceedings of the National Academy of Sciences 12/2010; 107(52):22629-34. · 9.68 Impact Factor
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ABSTRACT: Breast cancer metastases to bone are common in advanced stage disease. We have recently demonstrated that vitamin D deficiency enhances breast cancer growth in an osteolytic mouse model of breast cancer metastasis. In this study, we examined the effects of vitamin D deficiency on tumor growth in an osteosclerotic model of intra-skeletal breast cancer in mice.
The effects of 1,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)] on proliferation and apoptosis of MCF-7 breast cancer cells, and changes in the expression of genes within the vitamin D metabolic pathway (VDR, 1α- and 24-hydroxylase) were examined in vitro. MCF-7 breast cancer cells were injected intra-tibially into vitamin D deficient and vitamin D sufficient mice co-treated with and without osteoprotegerin (OPG). The development of tumor-related lesions was monitored via serial X-ray analysis. Tumor burden and indices of proliferation and apoptosis were determined by histology along with markers of bone turnover and serum intact PTH levels.
In vitro, MCF-7 cells expressed critical genes for vitamin D signalling and metabolism. Treatment with 1,25(OH)(2)D(3) inhibited cell growth and proliferation, and increased apoptosis. In vivo, osteosclerotic lesions developed faster and were larger at endpoint in the tibiae of vitamin D deficient mice compared to vitamin D sufficient mice (1.49±0.08 mm(2) versus 1.68±0.15 mm(2), P<0.05). Tumor area was increased by 55.8% in vitamin D deficient mice (0.81±0.13 mm(2) versus 0.52±0.11 mm(2) in vitamin D sufficient mice). OPG treatment inhibited bone turnover and caused an increase in PTH levels, while tumor burden was reduced by 90.4% in vitamin D sufficient mice and by 92.6% in vitamin D deficient mice. Tumor mitotic activity was increased in the tibiae of vitamin D deficient mice and apoptosis was decreased, consistent with faster growth.
Vitamin D deficiency enhances both the growth of tumors and the tumor-induced osteosclerotic changes in the tibiae of mice following intratibial implantation of MCF-7 cells. Enhancement of tumor growth appears dependent on increased bone resorption rather than increased bone formation induced by these tumors.
Bone 10/2010; 47(4):795-803. · 4.02 Impact Factor
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Arthritis & Rheumatism 10/2010; 63(1):1-9. · 7.87 Impact Factor
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ABSTRACT: Klinefelter syndrome is the most common chromosomal aneuploidy in men (XXY karyotype, 1 in 600 live births) and results in testicular (infertility and androgen deficiency) and nontesticular (cognitive impairment and osteoporosis) deficits. The extent to which skeletal changes are due to testosterone deficiency or arise directly from gene overdosage cannot be determined easily in humans. To answer this, we generated XXY mice through a four-generation breeding scheme. Eight intact XXY and 9 XY littermate controls and 8 castrated XXY mice and 8 castrated XY littermate controls were euthanized at 1 year of age. Castration occurred 6 months prior to killing. A third group of 9 XXY and 11 XY littermates were castrated and simultaneously implanted with a 1-cm Silastic testosterone capsule 8 weeks prior to sacrifice. Tibias were harvested from all three groups and examined by micro-computed tomography and histomorphometry. Blood testosterone concentration was assayed by radioimmunoassay. Compared with intact XY controls, intact androgen-deficient XXY mice had lower bone volume (6.8% +/- 1.2% versus 8.8% +/- 1.7%, mean +/- SD, p = .01) and thinner trabeculae (50 +/- 4 µm versus 57 +/- 5 µm, p = .007). Trabecular separation (270 +/- 20 µm versus 270 +/- 20 µm) or osteoclast number relative to bone surface (2.4 +/- 1.0/mm2 versus 2.7 +/- 1.5/mm2) did not differ significantly. Testosterone-replaced XXY mice continued to show lower bone volume (5.5% +/- 2.4% versus 8.1% +/- 3.5%, p = .026). They also exhibited greater trabecular separation (380 +/- 69 µm versus 324 +/- 62 µm, p = .040) but equivalent blood testosterone concentrations (6.3 +/- 1.8 ng/mL versus 8.2 +/- 4.2 ng/mL, p = .28) compared with testosterone-replaced XY littermates. In contrast, castration alone drastically decreased bone volume (p < .001), trabecular thickness (p = .05), and trabecular separation (p < .01) to such a great extent that differences between XXY and XY mice were undetectable. In conclusion, XXY mice replicate many features of human Klinefelter syndrome and therefore are a useful model for studying bone. Testosterone deficiency does not explain the bone phenotype because testosterone-replaced XXY mice show reduced bone volume despite similar blood testosterone levels.
Journal of bone and mineral research: the official journal of the American Society for Bone and Mineral Research 04/2010; 25(10):2148-54. · 6.04 Impact Factor
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ABSTRACT: Glucocorticoids at pharmacological doses have been shown to interfere with fracture repair. The role of endogenous glucocorticoids in fracture healing is not well understood. We examined whether endogenous glucocorticoids affect bone healing in an in vivo model of cortical defect repair.
Experiments were performed using a well characterised mouse model in which intracellular glucocorticoid signalling was disrupted in osteoblasts through transgenic overexpression of 11beta-hydroxysteroid-dehydrogenase type 2 (11beta-HSD2) under the control of a collagen type I promoter (Col2.3-11beta-HSD2). Unicortical bone defects (ø 0.8mm) were created in the tibiae of 7-week-old male transgenic mice and their wild-type littermates. Repair was assessed via histomorphometry, immunohistochemistry and microcomputed tomography (micro-CT) analysis at 1-3 weeks after defect creation.
At week 1, micro-CT images of the defect demonstrated formation of mineralized intramembranous bone which increased in volume and density by week 2. At week 3, healing of the defect was nearly complete in all animals. Analysis by histomorphometry and micro-CT revealed that repair of the bony defect was similar in Col2.3-11beta-HSD2 transgenic animals and their wild-type littermates at all time-points.
Disrupting endogenous glucocorticoid signalling in mature osteoblasts did not affect intramembranous fracture healing in a tibia defect repair model. It remains to be shown whether glucocorticoid signalling has a role in endochondral fracture healing.
Steroids 03/2010; 75(3):282-6. · 2.83 Impact Factor
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ABSTRACT: Vitamin D exerts antiproliferative, prodifferentiation, and proapoptotic effects on nonclassic target tissues such as breast. Blood levels of 25-hydroxyvitamin D [25(OH)D], the most sensitive indicator of vitamin D status, are inversely correlated with breast cancer risk; however, a causal relationship between vitamin D deficiency and breast cancer growth in bone has not been assessed. We examined the effect of vitamin D deficiency on the intraskeletal growth of the human breast cancer cell line MDA-MB-231-TxSA in a murine model of malignant bone lesions. Subsets of mice were treated concurrently with osteoprotegerin (OPG) to abrogate bone resorption. Outcomes were assessed by repeated radiographic and end-point micro-computed tomography and histologic analyses. Mice weaned onto a vitamin D-free diet developed vitamin D deficiency within 4 weeks [mean +/- SE serum 25(OH)D: 11.5 +/- 0.5 nmol/L], which was sustained throughout the study and was associated with secondary hyperparathyroidism and accelerated bone turnover. Osteolytic lesions appeared earlier and were significantly larger in vitamin D-deficient than in vitamin D-sufficient mice after 2 weeks (radiographic osteolysis: +121.5%; histologic tumor area: +314%; P < 0.05). Although OPG treatment reduced the size of radiographic osteolyses and tumor area in both groups, tumors remained larger in OPG-treated vitamin D-deficient compared with OPG-treated vitamin D-sufficient mice (0.53 +/- 0.05 mm(2) versus 0.19 +/- 0.05 mm2; P < 0.05). We conclude that vitamin D deficiency promotes the growth of human breast cancer cells in the bones of nude mice. These effects are partly mediated through secondary changes in the bone microenvironment, along with direct effects of vitamin D on tumor growth.
Cancer Research 02/2010; 70(5):1835-44. · 7.86 Impact Factor
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ABSTRACT: Glucocorticoids exert both anabolic and catabolic effects on bone. Previously, we reported that endogenous glucocorticoids control mesenchymal lineage commitment and osteoblastogenesis through regulation of Wnt signaling in osteoblasts. Here, we investigated the effects of glucocorticoids on Wnt expression in mature osteoblasts. Mature osteoblasts and their immature progenitors were separately isolated from Col2.3-GFP transgenic mice in which mature osteoblasts are identifiable through GFP expression. mRNA levels of Wnt2, Wnt2b, Wnt4, Wnt5a, Wnt10b, and Wnt11 were 4- to 12-fold higher in osteoblasts compared to their progenitors (P < 0.05). Expression of Wnt7b and Wnt10b in osteoblasts was modulated by corticosterone (CS), in a biphasic fashion with 3- to 3.5-fold upregulation at 10 nM CS (P < 0.01) and 50% downregulation at 100 nM CS (P < 0.05). CS 100 nM also increased expression of the Wnt inhibitors sFRP-1 and DKK-1 two- to threefold (P < 0.05). We conclude that the contrasting anabolic and catabolic effects of glucocorticoids on bone are, at least in part, mediated through the regulation of Wnt expression and its inhibitors in mature osteoblasts.
Calcified Tissue International 10/2009; 85(6):538-45. · 2.38 Impact Factor
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ABSTRACT: Endogenous glucocorticoids (GCs) modulate numerous biologic systems involved in the initiation and maintenance of arthritis. Bone cells play a critical role in the progression of arthritis, and some of the effects of GCs on inflammation may be mediated via these cells. The aim of this study was to investigate the impact of osteoblast-targeted disruption of GC signaling on joint inflammation, cartilage damage, and bone metabolism in the K/BxN mouse serum transfer model of autoimmune arthritis.
Intracellular GC signaling was disrupted in osteoblasts through transgenic overexpression of 11beta-hydroxysteroid dehydrogenase type 2 under the control of a type I collagen promoter. Arthritis was induced in 5-week-old male transgenic mice and their wild-type (WT) littermates, and paw swelling was assessed daily until the mice were killed. The mice were examined by histology, histomorphometry, and microfocal computed tomography, and serum was analyzed for cytokines, adrenocorticotropic hormone, and corticosterone.
Acute arthritis developed in both transgenic and WT mice treated with K/BxN mouse serum. However, the arthritis and local inflammatory activity were significantly attenuated in transgenic mice, as judged by clinical and histologic indices of inflammation and cartilage damage. Bone turnover and bone volume remained unchanged in arthritic transgenic mice, while WT mice exhibited stimulated bone resorption, suppressed osteoblast activity, and significantly reduced bone volume, compatible with the known effects of active inflammation on bone. Circulating levels of proinflammatory cytokines tended to be lower in arthritic transgenic mice than in control transgenic mice.
Disruption of GC signaling in osteoblasts significantly attenuates K/BxN mouse serum-induced autoimmune arthritis in mice. These data suggest that osteoblasts modulate the immune-mediated inflammatory response via a GC-dependent pathway.
Arthritis & Rheumatism 07/2009; 60(7):1998-2007. · 7.87 Impact Factor
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ABSTRACT: The role of endogenous glucocorticosteroids (GC) in bone development is ill-defined. Using the Col2.3-11betaHSD2 transgenic (tg) mouse model, we examined the effect of osteoblast-targeted disruption of intracellular GC signalling on bone growth and strength, and its modulation by factors such as age, gender and skeletal site. Tibiae and L3 vertebrae of 3 and 7-week-old, male and female wild type (WT) mice and their tg, age and sex matched littermates were analysed by micro-CT and mechanical testing. Data were analysed separately for 3 and 7-week-old mice by 2-way ANOVA using genotype (WT, tg), gender and their interactions as factors. Transgenic mice were characterised by lower bone volume, lower trabecular number and higher trabecular separation in tibial trabecular bone, as well as lower tibial cortical bone area and periosteal and endosteal perimeters. These changes resulted in a marked decrease in mechanical bone strength and stiffness in sexually mature, 7-week-old mice. In the tibia, the observed transgene effect was present in 3 and 7-week-old animals, indicating that the biological effect of disrupted GC signalling was independent of sexual maturity. This was not the case for the vertebral bones, where significant differences between tg and WT mice were seen in 7 but not in 3-week-old animals, suggesting that the effects of the transgene at this site may be modulated by age and/or changes in circulating sex hormone levels. Taken together, our results demonstrate that endogenous glucocorticoids may be required for normal bone growth but that their effect on bone structure and strength varies according to the skeletal site and sexual maturity of the animals.
Bone 05/2009; 45(1):61-7. · 4.02 Impact Factor
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ABSTRACT: Glucocorticoids are important regulators of bone cell differentiation and mesenchymal lineage commitment. Using a cell-specific approach of osteoblast-targeted transgenic disruption of intracellular glucocorticoid signaling, we discovered a novel molecular pathway by which glucocorticoids, mainly through the mature osteoblast, regulate the cellular mechanisms that govern cranial skeleton development. Embryonic and neonatal transgenic mice revealed a distinct phenotype characterized by hypoplasia and osteopenia of the cranial skeleton; disorganized frontal, parietal and interparietal bones; increased suture patency; ectopic differentiation of cartilage in the sagittal suture; and disturbed postnatal removal of parietal cartilage. Concurrently, expression of Mmp14, an enzyme essential for calvarial cartilage removal, was markedly reduced in parietal bone and cartilage of transgenic animals. Expression of Wnt9a and Wnt10b was significantly reduced in osteoblasts with disrupted glucocorticoid signaling, and accumulation of beta-catenin, the upstream regulator of Mmp14 expression, was decreased in osteoblasts, chondrocytes and mesenchymal progenitors of transgenic mice. Supracalvarial injection of Wnt3a protein rescued the transgenic cranial phenotype. These results define novel roles for glucocorticoids in skeletal development and delineate how osteoblasts--under steroid hormone control--orchestrate the intricate process of intramembranous bone formation by directing mesenchymal cell commitment towards osteoblastic differentiation while simultaneously initiating and controlling cartilage dissolution in the postnatal mouse.
Development 03/2009; 136(3):427-36. · 6.60 Impact Factor
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Annals of the rheumatic diseases 10/2008; 67(9):1201-3. · 8.11 Impact Factor
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ABSTRACT: Lineage commitment of mesenchymal progenitor cells is still poorly understood. Here we demonstrate that Wnt signaling by osteoblasts is essential for mesenchymal progenitor cells to differentiate away from a default adipogenic into an osteoblastic lineage. Dominant adipogenesis and reduced osteoblastogenesis were observed in calvarial cell cultures from transgenic mice characterized by osteoblast-targeted disruption of glucocorticoid signaling. This phenotypic shift in mesenchymal progenitor cell commitment was associated with reciprocal regulation of early adipogenic and osteoblastogenic transcription factors and with a reduction in Wnt7b and Wnt10b mRNA and beta-catenin protein levels in transgenic versus non-transgenic cultures. Transwell co-culture of transgenic mesenchymal progenitor cells with wild type osteoblasts restored commitment to the osteoblast lineage. This effect was blocked by adding sFRP1, a Wnt inhibitor, to the co-culture. Treatment of transgenic cultures with Wnt3a resulted in stimulation of osteoblastogenesis and suppression of adipogenesis. Our findings suggest a novel cellular mechanism in bone cell biology in which osteoblasts exert direct control over the lineage commitment of their mesenchymal progenitor through Wnt signaling. This glucocorticoid-dependent forward control function indicates a central role for osteoblasts in the regulation of early osteoblastogenesis.
Journal of Biological Chemistry 02/2008; 283(4):1936-45. · 4.77 Impact Factor
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ABSTRACT: Osteosclerotic metastases account for 20% of breast cancer metastases with the remainder osteolytic or mixed. In mouse models, osteolytic metastases are dependent on bone resorption for their growth. However, whether the growth of osteosclerotic bone metastases depends on osteoclast or osteoblast actions is uncertain. In this study, we investigate the effects of high and low bone resorption on tumour growth in a mouse model of osteosclerotic metastasis. We implanted human breast cancer, MCF-7, cells into the tibiae of mice. Low and high levels of bone resorption were induced by osteoprotegerin (OPG) treatment or calcium deficient diet respectively. We demonstrate that OPG treatment significantly reduces tumour area compared to vehicle (0.42 +/- 0.06 vs. 1.27 +/- 0.16 mm2, P < 0.01) in association with complete inhibition of osteoclast differentiation. In contrast, low calcium diet increases tumour area compared to normal diet (0.90 +/- 0.30 vs. 0.58 +/- 0.20 mm2, P < 0.05) in association with increased osteoclast numbers (84.44 +/- 5.18 vs. 71.11 +/- 3.56 per mm2 bone lesion area, P < 0.05). Osteoblast surfaces and new woven bone formation were similarly increased within the tumour boundaries in all treatment groups. Tumour growth in this model of osteosclerotic metastasis is dependent on ongoing bone resorption, as has been observed in osteolytic models. Bone resorption, rather than bone formation, apparently mediates this effect as osteoblast surfaces in the tumour mass were unchanged by treatments. Treatment of breast cancer patients through correction of calcium deficiency and/or with anti-resorptive agents such as OPG, may improve patient outcomes in the adjuvant as well as palliative settings.
Clinical and Experimental Metastasis 01/2008; 25(5):559-67. · 3.52 Impact Factor
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ABSTRACT: The skeleton is a major site of breast cancer metastases. High bone turnover increases risk of disease progression and death. However, there is no direct evidence that high bone turnover is causally associated with the establishment and progression of metastases. In this study, we investigate the effects of high bone turnover in a model of breast cancer growth in bone. Female nude mice commenced a diet containing normal (0.6%; 'Normal-Ca') or low (0.1%; 'Low-Ca') calcium content. Mice were concurrently treated with vehicle or osteoprotegerin (1 mg/kg/d s.c; n = 16 per group). Three days later (day 0), 50,000 Tx-SA cells (variant of MDA-MB-231 cells) were implanted by intratibial injection. On day 0, mice receiving Low-Ca had increased serum parathyroid hormone (PTH) and tartrate-resistant acid phosphatase 5b levels, indicating secondary hyperparathyroidism and high bone turnover, which was maintained until day 17. Osteoprotegerin increased serum PTH but profoundly reduced bone resorption. On day 17, in mice receiving Low-Ca alone, lytic lesion area, tumor area, and cancer cell proliferation increased by 43%, 24%, and 24%, respectively, compared with mice receiving Normal Ca (P < 0.01). Osteoprotegerin treatment completely inhibited lytic lesions, reduced tumor area, decreased cancer cell proliferation, and increased cancer cell apoptosis. Increased bone turnover, due to dietary calcium deficiency, promotes tumor growth in bone, independent of the action of PTH. Breast cancer patients frequently have low dietary calcium intake and high bone turnover. Treatment to correct calcium insufficiency and/or treatment with antiresorptive agents, such as osteoprotegerin, may be of benefit in the adjuvant as well as palliative setting.
Cancer Research 11/2007; 67(19):9542-8. · 7.86 Impact Factor
