Regulation of Osteoblast Differentiation: A Novel Function for Fibroblast Growth Factor 8 (original) (raw)
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Actions of fibroblast growth factor-8 in bone cells in vitro
AJP: Endocrinology and Metabolism, 2009
The fibroblast growth factors (FGFs) are a group of at least 25 structurally related peptides that are involved in many biological processes. Some FGFs are active in bone, including FGF-1, FGF-2, and FGF-18, and recent evidence indicates that FGF-8 is osteogenic, particularly in mesenchymal stem cells. In the current study, we found that FGF-8 was expressed in rat primary osteoblasts and in osteoblastic UMR-106 and MC3T3-E1 cells. Both FGF-8a and FGF-8b potently stimulated the proliferation of osteoblastic cells, whereas they inhibited the formation of mineralized bone nodules in long-term cultures of osteoblasts and reduced the levels of osteoblast differentiation markers, osteocalcin, and bone sialoprotein. FGF-8a induced the phosphorylation of p42/p44 mitogen-activated protein kinase (MAPK) in osteoblastic cells; however, its mitogenic actions were not blocked by either the MAPK kinase (MEK) inhibitor U-0126 or the PI 3-kinase (PI3K) inhibitor LY-294002. Interestingly, FGF-8a, un...
FGF-8 is involved in bone metastasis of prostate cancer
International Journal of Cancer, 2008
Prostate cancer is the most common malignancy of men in Western countries. Patients with advanced prostate cancer suffer from incurable bone metastases. Recent data indicate that interactions between prostate cancer cells, osteoblasts, osteoclasts and the bone matrix are essential in the formation of bone metastases. FGF-8 is widely overexpressed in prostate cancer. Recently, FGF-8 has been found to affect both osteoblast and osteoclast differentiation. The aim of this study was to examine the role of FGF-8 in bone metastasis of prostate cancer. Immunohistochemistry was used to analyse FGF-8 expression in clinical samples of prostate cancer bone metastases. The functional significance of FGF-8 in growth of bone metastasis and formation of bone lesions was verified by using intratibial inoculations of FGF-8 or mock transfected PC-3 prostate cancer cells in nude mice. Intratibial tumors and bone lesions were analysed with X-ray, micro-CT and detailed histomorphometry using image analysis software and with immunostaining for osteocalcin and cathepsin K. Immunohistochemical analysis of tissue microarray of bone metastases of human prostate cancer showed that 76% of human bone metastasis samples (n 5 25 from 11 patients) were positive for FGF-8. FGF-8 increased the growth of intratibial tumors and local formation of lytic and sclerotic lesions of bone. These results demonstrate that FGF-8 is expressed at a high frequency in bone metastases of human prostate cancer and that expression of FGF-8 in PC-3 prostate cancer cells increases their growth as intratibial tumors and modulates formation of bone lesions in an in vivo model of prostate cancer bone metastasis. '
PLOS ONE, 2017
Fibroblast growth factors (FGFs) and their receptors (FGFRs) have been implicated in promoting breast cancer growth and progression. While the autocrine effects of FGFR activation in tumor cells have been extensively studied, little is known about the effects of tumor cell-derived FGFs on cells in the microenvironment. Because FGF signaling has been implicated in the regulation of bone formation and osteoclast differentiation, we hypothesized that tumor cell-derived FGFs are capable of modulating osteoclast function and contributing to growth of metastatic lesions in the bone. Initial studies examining FGFR expression during osteoclast differentiation revealed increased expression of FGFR1 in osteoclasts during differentiation. Therefore, studies were performed to determine whether tumor cell-derived FGFs are capable of promoting osteoclast differentiation and activity. Using both non-transformed and transformed cell lines, we demonstrate that breast cancer cells express a number of FGF ligands that are known to activate FGFR1. Furthermore our results demonstrate that inhibition of FGFR activity using the clinically relevant inhibitor BGJ398 leads to reduced osteoclast differentiation and activity in vitro. Treatment of mice injected with tumor cells into the femurs with BGJ398 leads to reduced osteoclast activity and bone destruction. Together, these studies demonstrate that tumor cell-derived FGFs enhance osteoclast function and contribute to the formation of metastatic lesions in breast cancer.
Cancer Research, 1996
Tumors occasionally stimulate bone formation and cause osteoblastic metastases. Although this occurs most frequently in widespread prostate cancer, human prostate cancer cells are difficult to grow in culture without changing their phenotype, and the few available prostatic cancer lines do not increase bone formation in vivo. To identify tumor-derived osteoblast-stimulatory factors, we studied a long-established human tu mor cell line derived from human amnion that has, in the past, been reported to cause bone formation in vivo when inoculated into nude mice. Tumor cells were inoculated into nude mice and induced extensive new bone formation. To characterize osteoblast growth factors produced by these tumor cells, solid tumor was isolated from the mice and extracted at neutral pH. Biological activity, assessed by stimulation of proliferation of MG-63osteoblast-like cells,was usedto monitorpurificationafterhepa rin-Sepharose column chromatography, Mono-S, and C4 reverse-phase high-performance liquid chromatography. An extended amino-terminal
Fibroblast growth factors signaling in bone metastasis
Endocrine-Related Cancer, 2020
Many solid tumors metastasize to bone, but only prostate cancer has bone as a single, dominant metastatic site. Recently, the FGF axis has been implicated in cancer progression in some tumors and mounting evidence indicate that it mediates prostate cancer bone metastases. The FGF axis has an important role in bone biology and mediates cell-to-cell communication. Therefore, we discuss here basic concepts of bone biology, FGF signaling axis, and FGF axis function in adult bone, to integrate these concepts in our current understanding of the role of FGF axis in bone metastases.
Effects of Human Tumor Cell Lines on Local New Bone Formation In Vivo
Calcified Tissue International, 1997
Although some tumors cause osteolytic lesions, there are some that stimulate new bone formation. This is an important phenomenon because the responsible mechanisms probably represent an aberration of normal physiological bone formation, and identifying the factors involved in the process may lead to new therapies for various bone diseases. To clarify our understanding of the potential mechanism responsible, we compared and quantitated the extent of new bone formation stimulated by human tumors (HeLa, Hep-2, AV-3, FL, WISH and KB), some of which have osteogenic activity in vivo [2]. Tumor cells were injected over the calvaria of nude mice to examine formation of new bone. The tumor cells produced three histologically distinct patterns of new bone growth: (1) WISH and KB stimulated appositional bone growth adjacent to periosteal bone surfaces; (2) HeLa and Hep2 induced new bone growth over calvarial surface even when distant from the tumor mass; (3) FL stimulated bone formation adjacent to periosteum as well as ectopic bone formation in sites distant from bone. All tumors except AV3 induced mean new bone thickness >100 m, and Hep-2 cells produced bone 330 m thick. PCR and Northern blot analysis of mRNA isolated from cultured tumor cells revealed that all cell lines expressed mRNA for TGF, (fibroblast growth factor) FGF-1, FGF-2, and IGF-I, and most cell lines produced mRNA for PDGF. Only FL expressed large amounts of mRNA for BMP2. In serum-free conditioned media from Hep2 and HeLa cells purified by heparin affinity chromatography, we have identified FGF-1, FGF-2, and PDGF by immunodetection with specific antibodies. Our results show that new bone growth caused by these tumors is likely due to the production of bone growth factors by the tumor cells, and that the overall effects on bone may be due to several factors working in concert.
Regulation of osteoblast and osteoclast functions by FGF-6
Journal of Cellular Physiology, 2010
Fibroblast growth factor-6 (FGF-6) is known to be the key ligand for fibroblast growth factor receptor 4 (FGFR4) during muscle regeneration but its role in bone has yet to be verified. FGFR signaling is known to be important in the initiation and regulation of osteogenesis, so in this study the actions of FGF-6 on human osteoblasts and osteoclasts were investigated. Human primary osteoblasts (hOB) were used to study the effect of FGF-6 on proliferation (by ATP quantification), signal transduction (by ERK and AKT phosphorylation), differentiation (by alkaline phosphatase activity, APA), and mineralization (by calcein staining). To study FGF-6 activity on osteoclast differentiation, human bone marrow cells were used and tartrate-resistant acid phosphatase (TRAP) multinucleated cells together with actin filaments arrangements were quantified. Human primary mature osteoclasts were used to evaluate the effect of FGF-6 on osteoclast reabsorbing activity by reabsorbed pit measurements. FGF-6 >10 À9 M as FGF-2 10 À7 M induced hOB proliferation mediated by pERK together with a reduction in APA and reduced mineralization of the treated cells. Moreover FGF-6 increased the formation of TRAP-positive multinucleated cells in a dose-dependent manner (maximal effect at 10 À8 M). FGF-6-treated cells showed also a greater percentage of cells that formed typical osteoclast sealing zones. Mature osteoclasts cultured on dentine slice increased the area of reabsorption with a maximal effect of FGF-6 at 10 À12 M. FGF-6 may be considered a regulator of bone metabolism as shown by its activity on both osteoblasts and osteoclasts.
Molecular and Cellular Endocrinology, 2011
Estrogen is involved in the development and progression of breast cancer. Here we investigated the effect of fibroblast growth factor (FGF)-8 on breast cancer cell proliferation caused by estrogen using human breast cancer MCF-7 cells. MCF-7 cells express estrogen receptor (ER)a, ERb, FGF receptors, and Smad signaling molecules. Estradiol stimulated MCF-7 cell proliferation in a concentration-responsive manner, whereas BSA-bound estradiol had a weak effect on MCF-7 cell mitosis compared with the effect of free estradiol. It is notable that estrogen-induced cell proliferation was enhanced in the presence of FGF-8 and that the combined effects were reversed in the presence of an FGF-receptor kinase inhibitor or an ER antagonist. It was also revealed that FGF-8 increased the expression levels of ERa, ERb and aromatase mRNAs, while estradiol reduced the expression levels of ERs, aromatase and steroid sulfatase in MCF-7 cells. FGF-8-induced phosphorylation of FGF receptors was augmented by estradiol, which was reversed by an ER antagonist. FGF-8-induced activation of MAPKs and AKT signaling was also upregulated in the presence of estrogen. On the other hand, FGF-8 suppressed BMP-7 actions that are linked to mitotic inhibition by activating the cell cycle regulator cdc2. FGF-8 was revealed to inhibit BMP receptor actions including Id-1 promoter activity and Smad1/5/8 phosphorylation by suppressing expression of BMP type-II receptors and by increasing expression of inhibitory Smads. Collectively, the results indicate that FGF-8 acts to facilitate cell proliferation by upregulating endogenous estrogenic actions as well as by suppressing BMP receptor signaling in ER-expressing breast cancer cells.
Osteoblast-Derived TGF-β1 Stimulates IL-8 Release Through AP-1 and NF-κB in Human Cancer Cells
Journal of Bone and Mineral Research, 2008
Introduction: The bone marrow microenvironment is further enriched by growth factors released during osteoclastic bone resorption. It has been reported that the chemokine interleukin (IL)-8 is a potent and direct activator of osteoclastic differentiation and bone resorption. However, the effect of bone-derived growth factors on the IL-8 production in human cancer cells and the promotion of osteoclastogenesis are largely unknown. The aim of this study was to investigate whether osteoblast-derived TGF-1 is associated with osteolytic bone diseases. Materials and Methods: IL-8 mRNA levels were measured using RT-PCR analysis. MAPK phosphorylation was examined using the Western blot method. siRNA was used to inhibit the expression of TGF-1, BMP-2, and IGF-1. DNA affinity protein-binding assay and chromatin immunoprecipitation assays were used to study in vitro and in vivo binding of c-fos, c-jun, p65, and p50 to the IL-8 promoter. A transient transfection protocol was used to examine IL-8, NF-B, and activator protein (AP)-1 activity. Results: Osteoblast conditioned medium (OBCM) induced activation of IL-8, AP-1, and NF-B promoter in human cancer cells. Osteoblasts were transfected with TGF-1, BMP-2, or IGF-1 small interfering RNA, and the medium was collected after 48 h. TGF-1 but not BMP-2 or IGF-1 siRNA inhibited OBCM-induced IL-8 release in human cancer cells. In addition, TGF-1 also directly induced IL-8 release in human cancer cells. Activation of AP-1 and NF-B DNA-protein binding and MAPKs after TGF-1 treatment was shown, and TGF-1-induced IL-8 promoter activity was inhibited by the specific inhibitors of MAPK cascades. Conclusions: In this study, we provide evidence to show that the osteoblasts release growth factors, including TGF-1, BMP-2, and IGF-1. TGF-1 is the major contributor to the activation of extracellular signal-related kinase (ERK), p38, and c-Jun N-terminal kinase (JNK), leading to the activation of AP-1 and NF-B on the IL-8 promoter and initiation of IL-8 mRNA and protein release, thereby promoting osteoclastogenesis.
Vascular endothelial growth factor acts as an osteolytic factor in breast cancer metastases to bone
The Women's Oncology Review, 2005
Vascular endothelial growth factor (VEGF) is a proangiogenic cytokine that is expressed highly in many solid tumours often correlating with a poor prognosis. In this study, we investigated the expression of VEGF and its receptors in bone metastases from primary human breast tumours and further characterised its effects on osteoclasts in vitro. Breast cancer metastases to bone were immunohistochemically stained for VEGF, its receptors VEGFR1 and 2 (vascular endothelial growth factor receptor 1 and 2), demonstrating that breast cancer metastases express VEGF strongly and that surrounding osteoclasts express both VEGFR1 and VEGFR2. RAW 264.7 cells (mouse monocyte cell line) and human peripheral blood mononuclear cells (PBMCs) were cultured with VEGF, RANKL and M-CSF. VEGF and RANKL together induced differentiation of multinucleated, tartrate-resistant acid phophatase (TRAP)-positive cells in similar numbers to M-CSF and RANKL. The PBMCs were also able to significantly stimulate resorption of mineralised matrix after treatment with M-CSF with RANKL and VEGF with RANKL. We have shown that VEGF in the presence of RANKL supports PBMC differentiation into osteoclast-like cells, able to resorb substrate. Vascular endothelial growth factor may therefore play a role in physiological bone resorption and in pathological situations. Consequently, VEGF signalling may be a therapeutic target for osteoclast inhibition in conditions such as tumour osteolysis.