Genistein inhibits osteolytic bone metastasis and enhances bone mineral in nude mice

In this study, the effective activity of genistein on osteolytic bone metastasis and bone mineral was investigated. Female BALB/c-nu/nu mice were injected with estrogen receptor-negative human breast cancer cells, MDA-MB-231, into left cardiac ventricle to form osteolytic bone metastases, and administered genistein subcutaneously after radiologically small but defined osteolytic metastases had been observed (protocol 1), simultaneously with cancer cells inoculation (protocol 2) and prophylactically 7 days before inoculation of cancer cells (protocol 3). In all protocols, genistein (10mg/kg/day) markedly reduced the number and volume of osteolytic bone metastases assessed by radiography and the number of osteoclasts. Furthermore, histomorphometrical analysis revealed that genistein markedly increased trabecular area (Tb.Ar%), trabecular thickness (Tb.Th) and trabecular number (Tb.N), and decreased trabecular separation (Tb.Sp). These results thus demonstrate that genistein could inhibit osteolytic bone metastases, suppress bone resorption, increase bone mass and improve bone microstructure in bone metastases of breast cancer.     

The role of osteoclastic activity in prostate cancer skeletal metastases

Metastasis of prostate cancer to bone is a common complication of progressive prostate cancer. Skeletal metastases are often associated with severe pain and thus demand therapeutic interventions. Although often characterized as osteoblastic, prostate cancer skeletal metastases usually have an underlying osteoclastic component. Advances in osteoclast biology and pathophysiology have led toward defining putative therapeutic targets to attack tumor-induced osteolysis. Several factors have been found to be important in tumor-induced promotion of osteoclast activity. One key factor is the protein receptor activator of nuclear factor-kappa B ligand (RANKL), which is required to induce osteoclastogenesis. RANKL is produced by prostate cancer bone metastases, enabling these metastases to induce osteolysis through osteoclast activation. Another factor, osteoprotegerin, is a soluble decoy receptor for RANKL and inhibits RANKL-induced osteoclastogenesis. Osteoprotegerin has been shown in murine models to inhibit tumor-induced osteolysis. In addition to RANKL, parathyroid hormone-related protein and interleukin-6 are produced by prostate cancer cells and can promote osteoclastogenesis. Finally, matrix metalloproteinases (MMPs) are secreted by prostate cancer cells and promote osteolysis primarily through degradation of the nonmineralized bone matrix. MMP inhibitors have been shown to diminish tumor establishment in bone in murine models. Thus, many factors derived from prostate cancer metastases can promote osteolysis, and these factors may serve as therapeutic targets. The importance of osteoclasts in the establishment and progression of skeletal metastases has led to clinical evaluation of therapeutic agents to target them for slowing metastatic progression. Bisphosphonates are a class of compounds that decrease osteoclast life span by promoting their apoptosis. The bisphosphonate pamidronate has proven clinical efficacy for relieving bone pain associated with breast cancer metastases and has a promising outlook for prostate cancer metastases. Another bisphosphonate, zoledronic acid, appears to directly target prostate cancer cells in addition to diminishing osteoclast activity at the metastatic site. In addition to bisphosphonates, other novel therapies based on studies that delineate mechanisms of skeletal metastases establishment and progression will be developed in the near future.     

Harmine, a β-carboline alkaloid, inhibits osteoclast differentiation and bone resorption in vitro and in vivo

Bone homeostasis is controlled by the balance between osteoblastic bone formation and osteoclastic bone resorption. Excessive bone resorption is involved in the pathogenesis of bone-related disorders such as osteoporosis, arthritis and periodontitis. To obtain new antiresorptive agents, we searched for natural compounds that can inhibit osteoclast differentiation and function. We found that harmine, a β-carboline alkaloid, inhibited multinucleated osteoclast formation induced by receptor activator of nuclear factor-κB ligand (RANKL) in RAW264.7 cells. Similar results were obtained in cultures of bone marrow macrophages supplemented with macrophage colony-stimulating factor and RANKL, as well as in cocultures of bone marrow cells and osteoblastic UAMS-32 cells in the presence of vitamin D(3) and prostaglandin E(2). Furthermore, harmine prevented RANKL-induced bone resorption in both cell and bone tissue cultures. Treatment with harmine (10 mg/kg/day) also prevented bone loss in ovariectomized osteoporosis model mice. Structure-activity relationship studies showed that the C3-C4 double bond and 7-methoxy group of harmine are important for its inhibitory activity on osteoclast differentiation. In mechanistic studies, we found that harmine inhibited the RANKL-induced expression of c-Fos and subsequent expression of nuclear factor of activated T cells (NFAT) c1, which is a master regulator of osteoclastogenesis. However, harmine did not affect early signaling molecules such as ERK, p38 MAPK and IκBα. These results indicate that harmine inhibits osteoclast formation via downregulation of c-Fos and NFATc1 induced by RANKL and represses bone resorption. These novel findings may be useful for the treatment of bone-destructive diseases.     

Effects of the phytoestrogen coumestrol on RANK-ligand-induced differentiation of osteoclasts

Phytoestrogens, which have structural similarity to 17beta-estradiol, have been reported to act as agonists/antagonists of estrogen in animals and humans. Estrogen is known to have an important role in maintaining bone mass, because the concentration of serum estrogen decreases after menopause and the estrogen deficiency causes bone loss. In this study, we investigated the effects of coumestrol and other phytoestrogens on osteoclast differentiation using estrogen receptor alpha-transfected RAW264.7 (RAW264.7-ERalpha) cells. When the cells were cultured with the receptor activator of nuclear factor kappa B-ligand (RANKL), both formation of tartrate-resistant acid phosphatase (TRAP) positive multinucleated cells and TRAP activity were increased compared with control cells that were cultured in the absence of RANKL. Coumestrol decreased RANKL-induced formation of TRAP-positive multinucleated cells and TRAP activity dose-dependently. RANKL-stimulated RAW264.7-ERalpha cells formed resorption pits on calcium phosphate films and the pit formation was inhibited by coumestrol in a dose-dependent manner. RT-PCR analyses revealed that coumestrol (10 microM) decreased mRNA levels of calcitonin receptor (CTR) and matrix metalloproteinase-9 (MMP9) in RANKL-treated cells. In addition, pretreatment of coumestrol decreased RANKL-induced phosphorylation of extracellular signal-regulated kinases/p44/42 (ERK1/2). These results suggest that coumestrol has an inhibitory effect on the differentiation of osteoclasts, at least partially via ERK1/2 pathway.     

Osteoblast protects osteoclast devoid of sodium-dependent vitamin C transporters from oxidative cytotoxicity of ascorbic acid

The view that ascorbic acid indirectly benefits osteoclastogenesis through expression of receptor activator of nuclear factor-kappaB (NF-kappaB) ligand (RANKL) by osteoblasts is prevailing. In this study, we have examined the direct effect of ascorbic acid on osteoclastogenesis in cultured mouse osteoclasts differentiated from bone marrow precursors. The absence of alkaline phosphatase and osteoblastic marker genes validated the usefulness of isolation procedures. Sustained exposure to ascorbic acid, but not to dehydroascorbic acid, significantly reduced the number of multinucleated cells positive to tartrate-resistant acid phosphatase (TRAP) staining. In cultured osteoclasts, mRNA expression was seen for glucose transporter-1 involved in membrane transport of dehydroascorbic acid, but not for sodium-dependent vitamin C transporters-1 and -2 that are both responsible for the transport of ascorbic acid. The inhibition by ascorbic acid was completely prevented by catalase, while ascorbic acid or hydrogen peroxide drastically increased the number of cells stained with propidium iodide and the generation of reactive oxygen species, in addition to inducing mitochondrial membrane depolarization in cultured osteoclasts. In pre-osteoclastic cell line RAW264.7 cells, ascorbic acid similarly inhibited the formation of TRAP-positive multinucleated cells, with a significant decrease in RANKL-induced NF-kappaB transactivation. Moreover, co-culture with osteoblastic MC3T3-E1 cells significantly prevented the ascorbic acid-induced decrease in the number of TRAP-positive multinucleated cells in RAW264.7 cells. These results suggest that ascorbic acid may play a dual repulsive role in osteoclastogenesis toward bone remodeling through the direct cytotoxicity mediated by oxidative stress to osteoclasts, in addition to the indirect trophism mediated by RANKL from osteoblasts.     

桦木酸抗乳腺癌的作用机制研究进展

乳腺癌是影响全球女性的最常见恶性肿瘤之一,化疗药物的耐药性已成为乳腺癌治疗中最常见的挑战之一。桦木酸是一种天然存在的三萜类化合物,具有多种药理作用。桦木酸能通过抑制乳腺癌肿瘤细胞增殖和生长、促使肿瘤细胞凋亡、抑制肿瘤细胞侵袭和转移、抑制炎症反应以及与其他药物协同抗肿瘤等多个作用机制发挥抗乳腺癌的作用,因此综述了桦木酸抗乳腺癌的作用机制,以期为桦木酸的临床使用提供参考。     

Paeonol inhibits RANKL-induced osteoclastogenesis by inhibiting ERK, p38 and NF-kappaB pathway

Numerous studies have indicated that inflammatory cytokines play a major role in osteoclastogenesis, leading to the bone resorption that is frequently associated with osteoporosis. Paeonol (2'-hydroxy-4'-methoxyacetophenone), the main active compound of the traditionally used Chinese herb Paeonia lactiflora Pallas, has anti-inflammatory activity. Here we found that paeonol markedly inhibited the receptor activator of nuclear factor kappa B ligand (RANKL) plus macrophage colony stimulating factor (M-CSF)-induced osteoclastic differentiation from bone marrow stromal cells and RAW264.7 macrophage cells. In addition, in an assay of osteoclast activity on substrate plates, paeonol significantly decreased the resorption activity of mature osteoclasts. Treatment of RAW264.7 macrophages with RANKL induced extracellular signal-regulated kinases (ERK), p38 and c-Jun N-terminal kinase (JNK) phosphorylation. However, RANKL-induced ERK, p38 but not JNK phosphorylation was attenuated by paeonol. Furthermore, RANKL-mediated increase of IkappaBalpha phosphorylation, p65 phosphorylation at Ser(536), kappaB-luciferase activity and NF-kappaB binding activity was inhibited by paeonol. In addition, paeonol also prevented the bone loss inducing by ovariectomy in vivo. Our data suggest that paeonol inhibits osteoclastogenesis from bone marrow stromal cells and macrophage cells via attenuated of RANKL-induced ERK, p38 and NF-kappaB activation, which in turn protect bone loss from ovariectomy.     

磷脂酰肌醇-3-激酶/丝苏氨酸蛋白激酶信号通路参与核因子-κB受体活化因子配体诱导的MDA-MB-231乳腺癌细胞迁移

目的探讨磷脂酰肌醇-3-激酶/丝苏氨酸蛋白激酶(PI3K/Akt)信号通路在核因子-κB受体活化因子配体(RANKL)诱导的乳腺癌细胞迁移中的作用。方法 Transwell法测定RANKL刺激后MDA-MB-231细胞迁移能力的改变。蛋白印迹法检测MDA-MB-231细胞表面RANK蛋白的表达及RANKL刺激后pAkt及Akt的表达;检测数据用x珚±s表示,采用SPSS 16.0软件进行t检验。结果 MDA-MB-231细胞表达RANK蛋白,RANKL诱导MDA-MB-231细胞迁移能力增强,RANKL的圈套受体骨保护素(OPG)可阻断RANKL诱导的细胞迁移(P<0.01)。RANKL刺激后MDA-MB-231细胞p-Akt表达升高,PI3K抑制剂LY294002抑制RANKL诱导的细胞迁移(P<0.01)。结论 PI3K/Akt信号通路参与RANKL诱导的乳腺癌细胞MDA-MB-231迁移。     

WSS25, a sulfated polysaccharide,inhibits RANKL-induced mouse osteoclast formation by blocking SMAD/ID1 signaling

Aim:

WSS25 is a sulfated polysaccharide extracted from the rhizome of Gastrodia elata BI, which has been found to bind to bone morphogenetic protein 2 (BMP-2) in hepatocellular cancer cells. Since BMP-2 may regulate both osteoclasts and osteoblasts, here we investigated the effects of WSS25 on osteoclastogenesis in vitro and bone loss in ovariectomized mice.

Methods:

RAW264.7 cells or mouse bone marrow macrophages (BMMs) were treated with RANKL to induce osteoclastogenesis, which was assessed using TRAP staining, actin ring formation and pit formation assays, as well as bone resorption assay. Cell viability was detected with MTT assay. The mRNA levels of osteoclastogenesis-related genetic markers (TRAP, NFATc1, MMP-9 and cathepsin K) were detected using RT-PCR, while the protein levels of p-Smad1/5/8 and Id1 were measure with Western blotting. WSS25 was administered to ovariectomized mice (100 mg·kg⁻¹·d⁻¹, po) for 3 months. After the mice were euthanized, total bone mineral density and cortical bone density were measured.

Results:

In RAW264.7 cells and BMMs, WSS25 (2.5, 5, 10 μg/mL) did not affect the cell viability, but dose-dependently inhibited RANKL-induced osteoclastogenesis. Furthermore, WSS25 potently suppressed RANKL-induced expression of TRAP, NFATc1, MMP-9 and cathepsin K in RAW264.7 cells. Treatment of RAW264.7 cells with RANKL increased BMP-2 expression, Smad1/5/8 phosphorylation and Id1 expression, which triggered osteoclast differentiation, whereas co-treatment with WSS25 or the endogenous BMP-2 antagonist noggin suppressed the BMP-2/Smad/Id1 signaling pathway. In RAW264.7 cells, knockdown of Id1 attenuated RANKL-induced osteoclast differentiation, which was partially rescued by Id1 overexpression. In conformity to the in vitro experiments, chronic administration of WSS25 significantly reduced the bone loss in ovariectomized mice.

Conclusion:

WSS25 inhibits RANKL-induced osteoclast formation in RAW264.7 cells and BMMs by blocking the BMP-2/Smad/Id1 signaling pathway. WSS25 administration reduces bone loss in ovariectomized mice, suggesting that it may be a promising therapeutic agent for osteoporosis.     

Sciadopitysin suppresses RANKL-mediated osteoclastogenesis and prevents bone loss in LPS-treated mice

Previous studies reported that sciadopitysin (Sc), a type of biflavonoids, protects reactive oxygen species (ROS)-mediated osteoblast dysfunction, but its role in osteoclastogenesis remains unclear. In this study, we observed that Sc dose-dependently suppressed RANKL-induced osteoclastogenesis and bone resorption. Our results indicated that Sc treatment strongly reduced RANKL-induced osteoclast-specific genes expression, including cathepsin K (CTSK), tartrate-resistant acid phosphatase (TRAP) and MMP-9. Furthermore, Sc apparently attenuated RANKL-increased expressions of c-Fos and NFATc1. Meanwhile, Sc also strikingly inhibited the activation of NF-κB without altering the phosphorylation of MAPKs (p38, JNK and ERK1/2). Finally, our study demonstrated that Sc administration could reverse the bone loss in LPS-induced mice model. This study suggests that Sc inhibits RANKL-induced osteoclastogenesis and bone loss by inhibiting NF-κB activation and reducing the expression of c-Fos and NFATc1. Therefore, Sc might be benefit for RANKL-mediated osteolytic bone diseases.     

Novel anti-cancer strategy in bone tumors by targeting molecular and cellular modulators of bone resorption

Tumor cells alter the balanced process of bone formation and bone resorption mediated respectively by osteoblasts and osteoclasts, leading to the disruption of the normal equilibrium and resulting in a spectrum of osteolytic to osteoblastic lesions. This review will summarize research on molecules that play direct and essential roles in the differentiation and activity of osteoclasts, and the role of these molecules in bone destruction caused by cancer. Results from experimental models suggest that the Receptor Activator of NF-kB Ligand (RANKL), a member of the TNF superfamily is a common effector of bony lesions in osteolysis caused by primary and secondary bone tumors. Therefore, osteoclast represents an attractive target across a broad range of tumors that develop in bone. Elucidation of the mechanisms of RANKL interactions with its activator (RANK) and decoy (osteoprotegerin: OPG) receptors has enable the development of pharmacological inhibitors of RANKL (and of its signalling pathway) which have been recently patented, with potential for the treatment of cancer-induced bone disease. Blocking bone resorption by specific other drugs such as bisphosphonates, inhibitors of cathepsin K (the main enzyme involved in bone resorption mechanisms) or signalling pathways regulating osteoclast differentiation and activation is also a promising target for the treatment of osteolysis associated to bone tumors.     

Berberine inhibits RANKL-induced osteoclast formation and survival through suppressing the NF-kappaB and Akt pathways

Berberine, an isoquinoline alkaloid isolated from several medicinal plants, has been reported to possess anti-bacterial, anti-inflammatory and antitumor properties. Although berberine also inhibits osteoclastogenesis and bone resorption, the molecular machinery for its inhibitory effects remains unknown. This study focused on the suppressive effects of berberine on receptor activator of nuclear factor kappaB (NF-kappaB) ligand (RANKL)-induced osteoclastogenesis and survival. Berberine inhibited RANKL-mediated osteoclast formation and survival while having no cytotoxic effects on bone marrow macrophages or osteoblastic cells. Berberine attenuated RANKL-induced activation of NF-kappaB through inhibiting phosphorylation at the activation loop of IkappaBalpha kinase beta, phosphorylation and degradation of IkappaBalpha, and NF-kappaB p65 nuclear translocation. RANKL-induced Akt phosphorylation was strongly inhibited by berberine; however, neither monocyte/macrophage-colony stimulating factor (M-CSF)-induced nor insulin-induced Akt activation was inhibited by the drug. Under M-CSF- and RANKL-deprived condition, berberine increased the active form of caspase-3 in osteoclasts. By contrast, berberine did not potentiate the activation of caspase-3 in M-CSF-deprived bone marrow macrophages. These findings indicate that berberine inhibits osteoclast formation and survival through suppression of NF-kappaB and Akt activation and that both pathways in the osteoclast lineage are highly sensitive to berberine treatment.     

Trolox inhibits osteolytic bone metastasis of breast cancer through both PGE2-dependent and independent mechanisms

Bone is a preferred site of metastasis from breast cancer, and increased osteoclast activity is implicated in breast cancer outgrowth in the bone microenvironment. Our previous observation of an anti-osteoclastic activity of Trolox, a vitamin E analog, led us to investigate whether Trolox inhibits bone metastasis and osteolysis caused by breast cancer. Administration of Trolox markedly inhibited osteolytic bone metastasis in an experimental metastasis model by intracardiac injection of 4T1 breast cancer cells. Trolox inhibited proliferation of 4T1 cells in the bone marrow but not in the mammary fat pad. In addition, Trolox could reduce tumor burden, osteolysis, and prostaglandin E₂ (PGE₂) production induced by direct inoculation of 4T1 cells into the marrow cavity of the tibia. Trolox decreased the migratory and invasive activities of 4T1 cells via PGE₂-dependent and independent mechanisms. It also inhibited the ability of 4T1 cells to stimulate the expression of receptor activator of nuclear factor-κB ligand (RANKL), a key cytokine for osteoclast differentiation factor, in osteoblasts. In addition, Trolox suppressed RANKL expression in osteoblasts induced by soluble factors from 4T1 cells. Furthermore, Trolox suppressed 4T1 cell-induced osteoclast differentiation in the co-culture of bone marrow cells and osteoblasts via both PGE₂-dependent and independent mechanisms. Taken together, these results suggest that Trolox inhibits breast cancer cell-induced osteoclast differentiation and the invasive behavior of cancer cells through PGE₂-dependent and independent mechanisms, thereby suppressing osteolytic bone metastasis of breast cancer.     

Inhibition of osteoclast differentiation and bone resorption by a novel lysophosphatidylcholine derivative, SCOH

Osteoclasts are multinucleated cells formed by multiple steps of cell differentiation from progenitor cells of hematopoietic origin. Intervention in osteoclast differentiation is considered as an effective therapeutic approach to the treatment for bone diseases involving osteoclasts. In this study, we found that the organic compound (S)-1-lyso-2-stearoylamino-2-deoxy-sn-glycero-3-phosphatidylcholine (SCOH) inhibited osteoclast differentiation. The inhibitory effect of SCOH was observed in mouse bone marrow cell cultures supported either by coculturing with osteoblasts or by adding macrophage colony stimulating factor (M-CSF) and receptor activator of nuclear factor kappaB ligand (RANKL). M-CSF and RANKL activate the ERK, Akt, and NF-kappaB signal transduction pathways, and SCOH suppressed this activation. SCOH also inhibited the bone resorptive activity of differentiated osteoclasts. It attenuated bone resorption, actin ring formation, and survival of mature osteoclasts. Reduced activation of Akt and NF-kappaB and decreased induction of XIAP were observed in mature osteoclasts treated with SCOH. Thus, this novel phosphatidylcholine derivative may be useful for treating bone-resorption diseases.     

Zoledronic acid inhibits RANK expression and migration of osteoclast precursors during osteoclastogenesis

Bisphosphonates have been known to directly inhibit bone resorption and promote apoptosis in mature osteoclasts. Although bisphosphonates have been recognized as the most effective drugs to treat osteoporosis and bone cancer metastasis, the exact effects and mechanism(s) of bisphosphonates on osteoclastogenesis are unclear. The aim of this study was to clarify whether nitrogen-containing bisphosphonates affect recruitment and differentiation in osteoclasts. We examined the effects of zoledronic acid on receptor activator of NF-κB (RANK) expression and cell migration during osteoclastogenesis in two types of osteoclast precursors, RAW264.7 cells and Bone marrow cells (BMCs). Tumor necrosis factor-α (TNF-α) and RANK ligand (RANKL) upregulated RANK expression in RAW264.7 and BMCs in the presence of macrophage colony stimulating factor in a time-dependent manner. Zoledronic acid (30 and 50 μM) had no effect on cell viability in osteoclast precursors after 36 h of cultivation. Zoledronic acid (10 and 30 μM) strongly inhibited TNF-α- and RANKL-induced upregulation of RANK in a dose-dependent manner. The inhibitory effects on RANK expression were likely to be associated with the suppression of the NF-κB pathway, but not other downstream signaling pathways. Zoledronic acid (30 μM) also suppressed the TNF-α- and RANKL-induced migration of precursors by inhibiting the mevalonic acid pathway. Our results suggest that nitrogen-containing bisphosphonates not only inhibit mature osteoclasts but also prevent osteoclast precursors from differentiating and migrating towards inflammatory osteolysis lesions.