The inhibition of RANKL/RANK signaling by osteoprotegerin suppresses bone invasion by oral squamous cell carcinoma cells

Current comprehensive understanding of denosumab (the RANKL neutralizing antibody) in the treatment of bone metastasis of malignant tumors, including pharmacological mechanism and clinical trials

Denosumab, a fully humanized monoclonal neutralizing antibody, inhibits activation of the RANK/RANKL/OPG signaling pathway through competitive binding with RANKL, thereby inhibiting osteoclast-mediated bone resorption. Denosumab inhibits bone loss; therefore, it is used to treat metabolic bone diseases (including postmenopausal osteoporosis, male osteoporosis, and glucocorticoid-induced osteoporosis), in clinical practice. Since then, multiple effects of denosumab have been discovered. A growing body of evidence suggests that denosumab has a variety of pharmacological activities and broad potential in clinical diseases such as osteoarthritis, bone tumors, and other autoimmune diseases. Currently, Denosumab is emerging as a treatment for patients with malignancy bone metastases, and it also shows direct or indirect anti-tumor effects in preclinical models and clinical applications. However, as an innovative drug, its clinical use for bone metastasis of malignant tumors is still insufficient, and its mechanism of action needs to be further investigated. This review systematically summarizes the pharmacological mechanism of action of denosumab and the current understanding and clinical practice of the use of denosumab for bone metastasis of malignant tumors to help clinicians and researchers deepen their understanding of denosumab.

Research progress of bone-targeted drug delivery system on metastatic bone tumors

Bone metastases are common in malignant tumors and the effect of conventional treatment is limited. How to effectively inhibit tumor bone metastasis and deliver the drug to the bone has become an urgent issue to be solved. While bone targeting drug delivery systems have obvious advantages in the treatment of bone tumors. The research on bone-targeted anti-tumor therapy has made significant progress in recent years. We introduced the related tumor pathways of bone metastases. The tumor microenvironment plays an important role in metastatic bone tumors. We introduce a drug-loading systems based on different environment-responsive nanocomposites for anti-tumor and anti-metastatic research. According to the process of bone metastases and the structure of bone tissue, we summarized the information on bone-targeting molecules. Bisphosphate has become the first choice of bone-targeted drug delivery carrier because of its affinity with hydroxyapatite in bone. Therefore, we sought to summarize the bone-targeting molecule of bisphosphate to identify the modification effect on bone-targeting. And this paper discusses the relationship between bisphosphate bone targeting molecular structure and drug delivery carriers, to provide some new ideas for the research and development of bone-targeting drug delivery carriers. Targeted therapy will make a more outstanding contribution to the treatment of tumors.

Significance of cancer stroma for bone destruction in oral squamous cell carcinoma using different cancer stroma subtypes

Stromal cells in the tumor microenvironment (TME) can regulate the progression of numerous types of cancer; however, the bone invasion of oral squamous cell carcinoma (OSCC) has been poorly investigated. In the present study, the effect of verrucous SCC-associated stromal cells (VSCC-SCs), SCC-associated stromal cells (SCC-SCs) and human dermal fibroblasts on bone resorption and the activation of HSC-3 osteoclasts in vivo were examined by hematoxylin and eosin, AE1/3 (pan-cytokeratin) and tartrate-resistant acid phosphatase staining. In addition, the expression levels of matrix metalloproteinase (MMP)9, membrane-type 1 MMP (MT1-MMP), Snail, receptor activator of NF-κB ligand (RANKL) and parathyroid hormone-related peptide (PTHrP) in the bone invasion regions of HSC-3 cells were examined by immunohistochemistry. The results suggested that both SCC-SCs and VSCC-SCs promoted bone resorption, the activation of osteoclasts, and the expression levels of MMP9, MT1-MMP, Snail, RANKL and PTHrP. However, SCC-SCs had a more prominent effect compared with VSCC-SCs. Finally, microarray data were used to predict potential genes underlying the differential effects of VSCC-SCs and SCC-SCs on bone invasion in OSCC. The results revealed that IL1B, ICAM1, FOS, CXCL12, INS and NGF may underlie these differential effects. In conclusion, both VSCC-SCs and SCC-SCs may promote bone invasion in OSCC by enhancing the expression levels of RANKL in cancer and stromal cells mediated by PTHrP; however, SCC-SCs had a more prominent effect. These findings may represent a potential regulatory mechanism underlying the bone invasion of OSCC.

Bone morphogenetic protein induces bone invasion of melanoma by epithelial-mesenchymal transition via the Smad1/5 signaling pathway

Oral malignant melanoma, which frequently invades the hard palate or maxillary bone, is extremely rare and has a poor prognosis. Bone morphogenetic protein (BMP) is abundantly expressed in bone matrix and is highly expressed in malignant melanoma, inducing an aggressive phenotype. We examined the role of BMP signaling in the acquisition of an aggressive phenotype in melanoma cells in vitro and in vivo. In five cases, immunohistochemistry indicated the phosphorylation of Smad1/5 (p-Smad1/5) in the nuclei of melanoma cells. In the B16 mouse and A2058 human melanoma cell lines, BMP2, BMP4, or BMP7 induces morphological changes accompanied by the downregulation of E-cadherin, and the upregulation of N-cadherin and Snail, markers of epithelial-mesenchymal transition (EMT). BMP2 also stimulates cell invasion by increasing matrix metalloproteinase activity in B16 cells. These effects were canceled by the addition of LDN193189, a specific inhibitor of Smad1/5 signaling. In vivo, the injection of B16 cells expressing constitutively activated ALK3 enhanced zygoma destruction in comparison to empty B16 cells by increasing osteoclast numbers. These results suggest that the activation of BMP signaling induces EMT, thus driving the acquisition of an aggressive phenotype in malignant melanoma.

p130Cas induces bone invasion by oral squamous cell carcinoma by regulating tumor epithelial-mesenchymal transition and cell proliferation

Bone invasion is a critical factor in determining the prognosis of oral squamous cell carcinoma (OSCC) patients. Transforming growth factor β (TGF-β) is abundantly expressed in the bone matrix and is involved in the acquisition of aggressiveness by tumors. TGF-β is also important to cytoskeletal changes during tumor progression. In this study, we examined the relationship between TGF-β signaling and cytoskeletal changes during bone invasion by OSCC. Immunohistochemical staining of OSCC samples from five patients showed the expression of p130Cas (Crk-associated substrate) in the cytoplasm and phosphorylated Smad3 expression in the nucleus in OSCC cells. TGF-β1 induced the phosphorylation of Smad3 and p130Cas, as well as epithelial-mesenchymal transition (EMT) accompanied by the downregulation of the expression of E-cadherin, a marker of epithelial cells, and the upregulation of the expression of N-cadherin, or Snail, a marker of mesenchymal cells, in human HSC-2 cells and mouse squamous cell carcinome VII (SCCVII) cells. SB431542, a specific inhibitor of Smad2/3 signaling, abrogated the TGF-β1-induced phosphorylation of p130Cas and morphological changes. Silencing p130Cas using an short hairpin RNA (shRNA) or small interfering RNA in SCCVII cells suppressed TGF-β1-induced cell migration, invasion, EMT and matrix metalloproteinase-9 (MMP-9) production. Compared with control SCCVII cells, SCCVII cells with silenced p130Cas strongly suppressed zygomatic and mandibular destruction in vivo by reducing the number of osteoclasts, cell proliferation and MMP-9 production. Taken together, these results showed that the expression of TGF-β/p130Cas might be a new target for the treatment of OSCC bone invasion.

Blockade of NF-κB Translocation and of RANKL/RANK Interaction Decreases the Frequency of Th2 and Th17 Cells Capable of IL-4 and IL-17 Production, Respectively, in a Mouse Model of Allergic Asthma

The main purpose of this study was to investigate whether the blockade of the interaction between the receptor activator of nuclear factor-κB (NF-ĸB) ligand (RANKL) and its receptor RANK as well as the blockade of NF-κB inhibitor kinase (IKK) and of NF-κB translocation have the potential to suppress the pathogenesis of allergic asthma by inhibition and/or enhancement of the production by CD4⁺ and CD8⁺ T cells of important cytokines promoting (i.e., IL-4 and IL-17) and/or inhibiting (i.e., IL-10 and TGF-β), respectively, the development of allergic asthma. Studies using ovalbumin(OVA)-immunized mice have demonstrated that all the tested therapeutic strategies prevented the OVA-induced increase in the absolute number of IL-4- and IL-17-producing CD4⁺ T cells (i.e., Th2 and Th17 cells, respectively) indirectly, i.e., through the inhibition of the clonal expansion of these cells in the mediastinal lymph nodes. Additionally, the blockade of NF-κB translocation and RANKL/RANK interaction, but not IKK, prevented the OVA-induced increase in the percentage of IL-4-, IL-10- and IL-17-producing CD4⁺ T cells. These latter results strongly suggest that both therapeutic strategies can directly decrease IL-4 and IL-17 production by Th2 and Th17 cells, respectively. This action may constitute an important mechanism underlying the anti-asthmatic effect induced by the blockade of NF-κB translocation and of RANKL/RANK interaction. Thus, in this context, both these therapeutic strategies seem to have an advantage over the blockade of IKK. None of the tested therapeutic strategies increased both the absolute number and frequency of IL-10- and TGF-β-producing Treg cells, and hence they lacked the potential to inhibit the development of the disease via this mechanism.

CCL28-induced RARβ expression inhibits oral squamous cell carcinoma bone invasion

Oral squamous cell carcinoma (OSCC) frequently invades the maxillary or mandibular bone, and this bone invasion is closely associated with poor prognosis and survival. Here, we show that CCL28 functions as a negative regulator of OSCC bone invasion. CCL28 inhibited invasion and epithelial-mesenchymal transition (EMT), and its inhibition of EMT was characterized by induced E-cadherin expression and reduced nuclear localization of β-catenin in OSCC cells with detectable RUNX3 expression levels. CCL28 signaling via CCR10 increased retinoic acid receptor-β (RARβ) expression by reducing the interaction between RARα and HDAC1. In addition, CCL28 reduced RANKL production in OSCC and osteoblastic cells and blocked RANKL-induced osteoclastogenesis in osteoclast precursors. Intraperitoneally administered CCL28 inhibited tumor growth and osteolysis in mouse calvaria and tibia inoculated with OSCC cells. RARβ expression was also increased in tumor tissues. In patients with OSCC, low CCL28, CCR10, and RARβ expression levels were highly correlated with bone invasion. Patients with OSCC who had higher expression of CCL28, CCR10, or RARβ had significantly better overall survival. These findings suggest that CCL28, CCR10, and RARβ are useful markers for the prediction and treatment of OSCC bone invasion. Furthermore, CCL28 upregulation in OSCC cells or CCL28 treatment can be a therapeutic strategy for OSCC bone invasion.

Blockade of RANKL/RANK and NF-ĸB signalling pathways as novel therapeutic strategies for allergic asthma: A comparative study in a mouse model of allergic airway inflammation

The main aims of this study were: (1) to investigate whether a blockade of the interaction between the receptor activator of nuclear factor-κB (NF-ĸB) ligand (RANKL) and its receptor RANK may have potential as a novel therapeutic strategy for allergic asthma; (2) to compare the efficacies of the blockade of RANKL/RANK interaction as well as the blockade of NF-κB inhibitor kinase (IKK) and of NF-κB translocation to the nucleus, also in comparison with glucocorticosteroid treatment, in terms of the development of a mouse model of allergic airway inflammation (AAI) and accompanying immune response. The blockade of each of the targets fully prevented the development of AAI. All the tested therapeutic strategies seemed to have a certain advantage over glucocorticosteroids with regard to counteracting the development of AAI. Prevention of the activation and clonal expansion of CD4⁺ effector T (Teff) cells in the mediastinal lymph nodes (MLNs) constitutes a fundamental event underlying the anti-asthmatic effect induced by the blockade of IKK, NF-κB translocation or of RANKL/RANK interaction. The results indicate that attenuation of the CD11b⁺CD103^-CD11c^high dendritic cell response in the MLNs is an initial but not the main mechanism responsible for this effect. In turn, the direct anti-proliferative action on CD4⁺ Teff cells seems to constitute the chief mechanism responsible for the anti-asthmatic effect of all the tested therapeutic strategies. A clinical implication is that local inhibition of RANKL/RANK interaction achieved via inhalatory administration of a RANKL antagonist can be considered as a novel therapeutic strategy in treatment of allergic asthma.

Short-term RANKL exposure initiates a neoplastic transcriptional program in the basal epithelium of the murine salivary gland

Although salivary gland cancers comprise only ∼3-6% of head and neck cancers, treatment options for patients with advanced-stage disease are limited. Because of their rarity, salivary gland malignancies are understudied compared to other exocrine tissue cancers. The comparative lack of progress in this cancer field is particularly evident when it comes to our incomplete understanding of the key molecular signals that are causal for the development and/or progression of salivary gland cancers. Using a novel conditional transgenic mouse (K5:RANKL), we demonstrate that Receptor Activator of NFkB Ligand (RANKL) targeted to cytokeratin 5-positive basal epithelial cells of the salivary gland causes aggressive tumorigenesis within a short period of RANKL exposure. Genome-wide transcriptomic analysis reveals that RANKL markedly increases the expression levels of numerous gene families involved in cellular proliferation, migration, and intra- and extra-tumoral communication. Importantly, cross-species comparison of the K5:RANKL transcriptomic dataset with The Cancer Genome Atlas cancer signatures reveals the strongest molecular similarity with cancer subtypes of the human head and neck squamous cell carcinoma. These studies not only provide a much needed transcriptomic resource to mine for novel molecular targets for therapy and/or diagnosis but validates the K5:RANKL transgenic as a preclinical model to further investigate the in vivo oncogenic role of RANKL signaling in salivary gland tumorigenesis.

The RANK-RANKL axis: an opportunity for drug repurposing in cancer?

Drug repurposing offers advantages over traditional drug development in terms of cost, speed and improved patient outcomes. The receptor activator of nuclear factor kappa B (RANK) ligand (RANKL) inhibitor denosumab is approved for the prevention of skeletal-related events in patients with advanced malignancies involving bone, including solid tumours and multiple myeloma. Following improved understanding of the role of RANK/RANKL in cancer biology, denosumab has already been repurposed as a treatment for giant cell tumour of bone. Here, we review the role of RANK/RANKL in tumourigenesis, including effects on tumour initiation, progression and metastasis and consider the impact of RANK/RANKL on tumour immunology and immune evasion. Finally, we look briefly at ongoing trials and future opportunities for therapeutic synergy when combining denosumab with anti-cancer agents such as immune checkpoint inhibitors.

Engineering a monomeric variant of macrophage colony-stimulating factor (M-CSF) that antagonizes the c-FMS receptor

Enhanced activation of the signaling pathways that mediate the differentiation of mononuclear monocytes into osteoclasts is an underlying cause of several bone diseases and bone metastasis. In particular, dysregulation and overexpression of macrophage colony-stimulating factor (M-CSF) and its c-FMS tyrosine kinase receptor, proteins that are essential for osteoclast differentiation, are known to promote bone metastasis and osteoporosis, making both the ligand and its receptor attractive targets for therapeutic intervention. With this aim in mind, our starting point was the previously held concept that the potential of the M-CSF_C31S mutant as a therapeutic is derived from its inability to dimerize and hence to act as an agonist. The current study showed, however, that dimerization is not abolished in M-CSF_C31S and that the protein retains agonistic activity toward osteoclasts. To design an M-CSF mutant with diminished dimerization capabilities, we solved the crystal structure of the M-CSF_C31S dimer complex and used structure-based energy calculations to identify the residues responsible for its dimeric form. We then used that analysis to develop M-CSF_C31S,M27R, a ligand-based, high-affinity antagonist for c-FMS that retained its binding ability but prevented the ligand dimerization that leads to receptor dimerization and activation. The monomeric properties of M-CSF_C31S,M27R were validated using dynamic light scattering and small-angle X-ray scattering analyses. It was shown that this mutant is a functional inhibitor of M-CSF-dependent c-FMS activation and osteoclast differentiation in vitro Our study, therefore, provided insights into the sequence-structure-function relationships of the M-CSF/c-FMS interaction and of ligand/receptor tyrosine kinase interactions in general.

RANK Ligand Modulation of Autophagy in Oral Squamous Cell Carcinoma Tumor Cells

Autophagy is a cellular process to recycle nutrients and has been implicated in cancer treatment. Oral squamous cell carcinoma (OSCC) is the most common oral cancer which ranks 3% of cancers in men and 2% in women. In this study, immunohistochemical staining of OSCC tumor specimens from human subjects and an athymic mouse model demonstrated high levels of autophagy markers LC3-II and ATG5 expression. Further, we identified high levels LC3-II expression in OSCC tumor cell lines (SCC-1, SCC-12, and SCC-14a) compared to normal human epithelial (RWPE-1) cells. OSCC cells express high levels of RANK ligand (RANKL); however, a functional role in autophagy is unknown. Interestingly, RANKL stimulation significantly increased autophagosome-related gene expressions such as LC3, ATG5, BECN1, and PI3KC3 mRNA expression in OSCC cells. Further, Western blot analysis of total cell lysates demonstrated a dose-dependent increase in LC3-II and ATG5 expression in RANKL-stimulated cells. In addition, RANKL increased expression of LC3-I and LC3-II, essential for autophagosome formation. Confocal microscopy analysis of LC3-II and localization with lysosome further confirms autophagosome formation in response to RANKL treatment in OSCC cells. Collectively, our results indicate a novel function of RANKL to induce autophagosome formation, and could be a potential therapeutic target to control OSCC tumor progression.

RANK-RANKL signalling in cancer

Oncogenic events combined with a favourable environment are the two main factors in the oncological process. The tumour microenvironment is composed of a complex, interconnected network of protagonists, including soluble factors such as cytokines, extracellular matrix components, interacting with fibroblasts, endothelial cells, immune cells and various specific cell types depending on the location of the cancer cells (e.g. pulmonary epithelium, osteoblasts). This diversity defines specific "niches" (e.g. vascular, immune, bone niches) involved in tumour growth and the metastatic process. These actors communicate together by direct intercellular communications and/or in an autocrine/paracrine/endocrine manner involving cytokines and growth factors. Among these glycoproteins, RANKL (receptor activator nuclear factor-κB ligand) and its receptor RANK (receptor activator nuclear factor), members of the TNF and TNFR superfamilies, have stimulated the interest of the scientific community. RANK is frequently expressed by cancer cells in contrast with RANKL which is frequently detected in the tumour microenvironment and together they participate in every step in cancer development. Their activities are markedly regulated by osteoprotegerin (OPG, a soluble decoy receptor) and its ligands, and by LGR4, a membrane receptor able to bind RANKL. The aim of the present review is to provide an overview of the functional implication of the RANK/RANKL system in cancer development, and to underline the most recent clinical studies.

Establishment of a xenograft model to explore the mechanism of bone destruction by human oral cancers and its application to analysis of role of RANKL

BACKGROUND

The molecular mechanism underlying bone invasion caused by oral squamous cell carcinoma (OSCC) is not well understood. To elucidate the molecular mechanism, the development of more suitable xenograft models mimicking human mandibular bone destruction by OSCC has been required.

MATERIALS AND METHODS

Human OSCC cell lines, HSC3, HSC3-C1, and HSC3-R2, were injected in the periosteal region of the mandible in athymic mice, and the bone destruction was analyzed. Receptor activators of nuclear factor κ-B ligand (RANKL) mRNA and protein expression levels were measured in the OSCC cell lines. Antibody that specifically neutralizes mouse RANKL and human RANKL, respectively, was injected into HSC3-cell-transplanted mice.

RESULTS

Transplantation of HSC3 cells induced mandibular bone destruction. Histological examination revealed numerous osteoclasts on the bone destruction surface. Fibroblastic cell intervention between the cancer nests and resorbing bone surface was observed in a similar fashion to those observed in human OSCC cases. The number of osteoclasts and fibroblasts was significantly correlated. Bone destruction induced by the transplantation of HSC3 cells was reduced by injection of an antibody that specifically neutralizes mouse RANKL. Transplantation of HSC3-R2 cells, which overexpresses RANKL, induced advanced bone destruction compared to that of HSC3-C1 cells, which only overexpress the empty vector.

CONCLUSIONS

We established a useful xenograft model for investigating the molecular mechanism underlying the bone destruction induced by OSCC in the jaw. This model will be used to investigate the precise roles of several cytokines synthesized by both cancer cells and fibroblastic cells in OSCC-associated bone destruction in the jaw.

Chorioamniotic membrane senescence: a signal for parturition?

OBJECTIVE

Senescence is an important biological phenomenon involved in both physiologic and pathologic processes. We propose that chorioamniotic membrane senescence is a mechanism associated with human parturition. The present study was conducted to explore the association between senescence and normal term parturition by examining the morphologic and biochemical evidences in chorioamniotic membranes.

STUDY DESIGN

Chorioamniotic membranes were collected from normal term deliveries; group 1: term labor and group 2: term, not in labor. Senescence-related morphologic changes were determined by transmission electron microscopy and biochemical changes were studied by senescence-associated (SA) β-galactosidase staining. Amniotic fluid samples collected from both term labor and term not in labor were analyzed for 14 SA secretory phenotype (SASP) markers.

RESULTS

Morphologic evidence of cellular senescence (enlarged cells and organelles) and a higher number of SA β-galactosidase-stained amnion and chorion cells were observed in chorioamniotic membranes obtained from women in labor at term, when compared to term not in labor. The concentration of proinflammatory SASP markers (granulocyte macrophage colony-stimulating factor, interleukin-6 and -8) was significantly higher in the amniotic fluid of women in labor at term than women not in labor. In contrast, SASP factors that protect against cell death (eotaxin-1, soluble Fas ligand, osteoprotegerin, and intercellular adhesion molecule-1) were significantly lower in the amniotic fluid samples from term labor.

CONCLUSION

Morphologic and biochemical features of senescence were more frequent in chorioamniotic membranes from women who experienced term labor. Senescence of chorioamniotic membranes were also associated with amniotic fluid SASP markers.

Aberrant Activation of the RANK Signaling Receptor Induces Murine Salivary Gland Tumors

Unlike cancers of related exocrine tissues such as the mammary and prostate gland, diagnosis and treatment of aggressive salivary gland malignancies have not markedly advanced in decades. Effective clinical management of malignant salivary gland cancers is undercut by our limited knowledge concerning the key molecular signals that underpin the etiopathogenesis of this rare and heterogeneous head and neck cancer. Without knowledge of the critical signals that drive salivary gland tumorigenesis, tumor vulnerabilities cannot be exploited that allow for targeted molecular therapies. This knowledge insufficiency is further exacerbated by a paucity of preclinical mouse models (as compared to other cancer fields) with which to both study salivary gland pathobiology and test novel intervention strategies. Using a mouse transgenic approach, we demonstrate that deregulation of the Receptor Activator of NFkB Ligand (RANKL)/RANK signaling axis results in rapid tumor development in all three major salivary glands. In line with its established role in other exocrine gland cancers (i.e., breast cancer), the RANKL/RANK signaling axis elicits an aggressive salivary gland tumor phenotype both at the histologic and molecular level. Despite the ability of this cytokine signaling axis to drive advanced stage disease within a short latency period, early blockade of RANKL/RANK signaling markedly attenuates the development of malignant salivary gland neoplasms. Together, our findings have uncovered a tumorigenic role for RANKL/RANK in the salivary gland and suggest that targeting this pathway may represent a novel therapeutic intervention approach in the prevention and/or treatment of this understudied head and neck cancer.

Magnetic resonance imaging for diagnosis of mandibular involvement from head and neck cancers: a systematic review and meta-analysis

Background

Diagnosis of mandibular involvement caused by head and neck cancers is critical for treatment. We performed a meta-analysis to determine the diagnostic efficacy of MR for distinguishing mandibular involvement caused by head and neck cancers.

Methods

Thirteen databases were searched electronically and hand-searching was also done. Two reviewers conducted study inclusion, data extractions, and quality assessment of the studies independently. Meta-disc 1.4 and STATA 11.0 were used to conduct the meta-analysis.

Results

16 studies involving a total of 490 participants underwent MR examinations and were accounted for in this meta-analysis. Among the included studies, 2 had high risk of bias, while the rest had unclear risk of bias. Meta-regression showed that the slight clinical and methodological heterogeneities did not influence the outcome (P>0.05). Meta-analysis indicated that the MR for the diagnosis of mandibular involvement had a pooled sensitivity (SEN) of 78%, specificity (SPE) of 83%, positive likelihood ratio (+LR) of 3.80, negative likelihood ratio (-LR) of 0.28, diagnostic odds ratio (DOR) of 28.94, area under curve (AUC) of 0.9110, and Q* of 0.8432. Two studies detected the diagnostic efficacy of MR for the mandibular medullar invasion, and only one study reported the inferior alveolar canal invasion, which made it impossible to include it in our meta-analysis. In comparing to CT, MR had a higher SEN without statistical significance (P = 0.08), but a significantly lower SPE (P = 0.04). The synthesized diagnostic efficacy (AUC and Q*) on mandibular involvement was similar between the two modalities (P>0.05).

Conclusions

Present clinical evidence showed that MR had an acceptable diagnostic value in detecting mandibular involvement caused by head and neck cancers. MR exceeded CT in diagnosing patients with mandibular invasion (higher sensitivity than CT) but was less efficacious to exclude patients without the mandibular invasion (lower specificity than CT).

Multifunctional properties of RANKL/RANK in cell differentiation, proliferation and metastasis

It is known that there are close relationships between bone destruction and tumor growth in bone metastasis. RANKL is a central factor in bone metastasis, inducing osteoclastogenesis mediated by its receptor RANK. Recent reports demonstrate that RANKL has important roles in organogenesis stimulating proliferation and differentiation of epithelial and stroma cells. RANKL is induced not only by cytokines and hormones but also by UV-irradiation, inflammation and carcinogens. Expression of RANK and RANKL is found in several human cancer cell lines, and RANK signaling stimulates proliferation, migration and epithelial–mesenchymal transition of cancer cells, which may be involved in metastasis via an autocrine/paracrine mechanism. RANKL regulates the number of Tregs that produce RANKL, which may affect cancer metastasis. In this review we discuss the multifunctional roles of RANKL/RANK in osteoclastogenesis, organogenesis, and the metastasis and tumorigenesis of cancer cells.

Targeting RANKL in breast cancer: bone metastasis and beyond

In breast cancer, RANK ligand (RANKL) appears to play an important role in the process of chemotaxis between circulating tumor cells and the bone microenvironment, which enables RANK-expressing breast cancer cells to migrate into the bone. Mounting clinical evidence has further demonstrated that the anti-RANKL monoclonal antibody; denosumab is the most effective approach in the prevention of skeletal-related events. On the other hand, inhibiting RANKL in preclinical models, not only reduced breast cancer formation but also decreased the development of lung metastases, suggesting RANKL as a novel target for breast cancer chemoprevention. In addition, recent data have pointed to a potential role of RANKL in the biology of breast cancer arising at a young age. Hence, RANKL emerges as a key molecule, not only in the field of breast cancer bone metastasis but also in the biology of breast cancer as a whole.

Co-expression of CD44+/RANKL+ tumor cells in the carcinogenesis of oral squamous cell carcinoma

Receptor activator of nuclear factor-kappa (RANK)/receptor activator of nuclear factor-kappa B ligand (RANKL) signaling helps putative cancer stem cells (CSC) to maintain their stemness. Expression of CD44 and RANKL was analyzed in oral squamous cell carcinoma specimen (n = 191). Moreover, RANKL expression was measured in cancer cell lines (BICR3, BICR56) by immunohistochemistry and western blot analysis. Scanned images were digitally analyzed using ImageJ and the immunomembrane plug-in. CD44 and RANKL expression on protein level was correlated with clinical characteristics and impact on survival. RANKL was co-labeled with CD44 in immunohistochemical and immunofluorescence double labeling experiments. Although high CD44+/RANKL+ co-expression was significantly associated with clinicopathological factors and worse survival, multivariate analysis did not demonstrate high CD44+/RANKL+ co-expression as independent prognostic factor. Immunohistochemical and immunofluorescence double labeling experiments revealed RANKL expression by CD44+ cancer cells. RANKL specificity was confirmed by western blot analysis. For the first time, this study provides evidence that RANKL expression in OSCC might be associated with disease recurrence and a cell compartment measured by CD44+/RANKL+ co-expression within the mucosal epithelial basal layer cells.

RANKL synthesized by both stromal cells and cancer cells plays a crucial role in osteoclastic bone resorption induced by oral cancer

The molecular mechanisms underlying bone destruction by invading oral cancer are not well understood. Using IHC, we demonstrated that receptor activator of nuclear factor-κB ligand (RANKL)-positive fibroblasts and cancer cells were located at sites of bone invasion in human oral cancers. HSC3 and HO-1-N-1, human oral cancer cell lines, expressed RANKL and stimulated Rankl expression in the UAMS-32 murine osteoblastic cell line. We discriminated the roles of RANKL synthesized by stromal cells and cancer cells in cancer-associated bone resorption by using species-specific RANKL antibodies against murine RANKL and human RANKL, respectively. Osteoclastogenesis induced by the conditioned medium of HSC3 and HO-1-N-1 cells in a co-culture of murine bone marrow cells and UAMS-32 cells was inhibited by the addition of antibodies against either mouse or human RANKL. HSC3-induced bone destruction was greatly inhibited by the administration of anti-mouse RANKL antibody in a xenograft model. HO-1-N-1-induced bone destruction was inhibited by the administration of either anti-mouse or anti-human RANKL antibody. Bone destruction induced by the transplantation of human RANKL-overexpressing cells (HSC3-R2) was greatly inhibited by the injection of anti-human RANKL antibody. The present study revealed that RANKL produced by both stromal and cancer cells is involved in oral cancer-induced osteoclastic bone resorption. These results provide important information for understanding the cellular and molecular basis of cancer-associated bone destruction and the mechanism of action underlying RANKL antibody (denosumab) therapy.

The RANKL/RANK system as a therapeutic target for bone invasion by oral squamous cell carcinoma (Review)

Squamous cell carcinomas (SCCs) of the gingiva frequently invade the mandible or maxilla; this invasion is associated with a worse prognosis. The bone destruction associated with carcinomal invasion is mediated by osteoclasts rather than directly by the carcinoma. Therefore, if the cellular and molecular mechanisms by which oral SCC regulates bone invasion were known, it could inform the development of new therapeutic targets. Recently, dysregulation of the functional equilibrium in the receptor activator of NF-κB ligand (RANKL)/RANK/osteoprotegerin (OPG) triad has been shown to be responsible for osteolysis associated with the development of malignant tumors in bone sites. Furthermore, the administration of OPG or soluble RANK prevents bone metastasis by cancer cells. In this review, we discuss recent findings indicating that bone invasion by oral SCC is mediated via RANKL/RANK and may be successfully prevented by RANKL inhibition.

Identification of a novel bone morphogenetic protein (BMP)-inducible transcript, BMP-inducible transcript-1, by utilizing the conserved BMP-responsive elements in the Id genes

Bone morphogenetic proteins (BMPs) inhibit myogenesis and induce osteoblastic differentiation in myoblasts. They also induce the transcription of several common genes, such as Id1, Id2 and Id3, in various cell types. We have reported that a GC-rich element in the Id1 gene functions as a BMP-responsive element (BRE) that is regulated by Smads. In this study, we analyzed and identified BREs in the 5'-flanking regions of the mouse Id2 and Id3 genes. The core GGCGCC sequence was conserved among the BREs in the Id1, Id2 and Id3 genes and was essential for the response to BMP signaling via Smads. We found a novel BRE on mouse chromosome 13 at position 47,723,740-47,723,768 by searching for conserved sequences containing the Id1 BRE. This potential BRE was found in the 5'-flanking region of a novel gene that produces a non-coding transcript, termed BMP-inducible transcript-1 (BIT-1), and this element regulated the expression of this gene in response to BMP signaling. We found that BIT-1 is expressed in BMP target tissues such as the testis, brain, kidney and cartilage. These findings suggest that the transcriptional induction of the Ids, BIT-1 and additional novel genes containing the conserved BRE sequence may play an important role in the regulation of the differentiation and/or function of target cells in response to BMPs.

Anti-RANKL therapy for bone tumours: Basic, pre-clinical and clinical evidences

Bone remodelling is related to coordinated phases of bone resorption and bone apposition allowing the maintenance of bone integrity, the phosphocalcic homoeostasis all along the life and consequently the bone adaptation to mechanical constraints or/and to endocrine fluctuations. Unfortunately, bone is a frequent site of tumour development originated from bone cell lineages (primary bone tumours: bone sarcomas) or from nonosseous origins (bone metastases: carcinomas). These tumour cells disrupt the balance between osteoblast and osteoclast activities resulting in a disturbed bone remodelling weakening the bone tissue, in a strongly altered bone microenvironment and consequently facilitating the tumour growth. At the early stage of tumour development, osteoclast differentiation and recruitment of mature osteoclasts are strongly activated resulting in a strong bone matrix degradation and release of numerous growth factors initially stored into this organic/calcified matrix. In turn these soluble factors stimulate the proliferation of tumour cells and exacerbate their migration and their ability to initiate metastases. Because Receptor Activator of NFκB Ligand (RANKL) is absolutely required for in vivo osteoclastogenesis, its role in the bone tumour growth has been immediately pointed out and has consequently allowed the development of new targeted therapies of these malignant diseases. The present review summarises the role of RANKL in the bone tumour microenvironment, the most recent pre-clinical and clinical evidences of its targeting in bone metastases and bone sarcomas. The following sections position RANKL targeted therapy among the other anti-resorptive therapies available and underline the future directions which are currently under investigations.

Selective inhibition of NF-κB suppresses bone invasion by oral squamous cell carcinoma in vivo

Nuclear factor-κB (NF-κB) is constitutively activated in many cancers, including oral squamous cell carcinoma (OSCC), and is involved in the invasive characteristics of OSCC, such as growth, antiapoptotic activity and protease production. However, the cellular mechanism underlying NF-κB's promotion of bone invasion by OSCC is unclear. Therefore, we investigated the role of NF-κB in bone invasion by OSCC in vivo. Immunohistochemical staining of OSCC invading bone in 10 patients indicated that the expression and nuclear translocation of p65, a main subunit of NF-κB, was increased in OSCC compared with normal squamous epithelial cells. An active form of p65 phosphorylated at serine 536 was present mainly in the nucleus in not only differentiated tumor cells but also tumor-associated stromal cells and bone-resorbing osteoclasts. We next injected mouse OSCC SCCVII cells into the masseter region of C(3) H/HeN mice. Mice were treated for 3 weeks with a selective NF-κB inhibitor, NBD peptide, which disrupts the association of NF-κB essential modulator (NEMO) with IκB kinases. NBD peptide treatment inhibited TNFα-induced and constitutive NF-κB activation in SCCVII cells in vitro and in vivo, respectively. Treatment with NBD peptide decreased zygoma and mandible destruction by SCCVII cells, reduced number of osteoclasts by inhibiting RANKL expression in osteoblastic cells and SCCVII cells, increased apoptosis and suppressed the proliferation of SCCVII cells. Taken together, our data clearly indicate that inhibition of NF-κB is useful for inhibiting bone invasion by OSCC.