Targeted overexpression of BSP in osteoclasts promotes bone metastasis of breast cancer cells

Identification of an endoplasmic reticulum stress-related prognostic risk model with excellent prognostic and clinical value in oral squamous cell carcinoma

BACKGROUND

Recently, endoplasmic reticulum stress related gene (ERS) markers have performed very well in predicting the prognosis of tumor patients.

METHODS

The differentially expressed genes in Oral squamous cell carcinoma (OSCC) were obtained from TCGA and GTEx database. Three prognosis-related and differentially expressed ERSs were screened out by Least Absolute Selection and Shrinkage Operator (Lasso) regression to construct a prognostic risk model. Receiver Operating Characteristic Curve (ROC), riskplots and survival curves were used to verify the model's accuracy in predicting prognosis. Multi-omics analysis of immune infiltration, gene mutation, and stem cell characteristics were performed to explore the possible mechanism of OSCC. Finally, we discussed the model's clinical application value from the perspective of drug sensitivity.

RESULTS

Three genes used in the model (IBSP, RDM1, RBP4) were identified as prognostic risk factors. Bioinformatics analysis, tissue and cell experiments have fully verified the abnormal expression of these three genes in OSCC. Multiple validation methods and internal and external datasets confirmed the model's excellent performance in predicting and discriminating prognosis. Cox regression analysis identified risk score as an independent predictor of prognosis. Multi-omics analysis found strong correlations between risk scores and immune cells, cell stemness index, and tumor mutational burden (TMB). It was also observed that the risk score was closely related to the half maximal inhibitory concentration of docetaxel, gefitinib and erlotinib. The excellent performance of the nomogram has been verified by various means.

CONCLUSION

A prognostic model with high clinical application value was constructed. Immune cells, cellular stemness, and TMB may be involved in the progression of OSCC.

Pan-cancer analysis shows that IBSP is a potential prognostic and immunotherapeutic biomarker for multiple cancer types including osteosarcoma

Background

IBSP is a member of the small integrin-binding ligand N-linked glycoprotein (SIBLING) family that plays a vital role in bone formation, renewal and repair. Emerging evidence revealed that IBSP participated in the tumorigenesis and progression in some cancers. However, its significance in tumour prognosis and immunotherapy is still unknown.

Methods

In the current study, we studied the role of IBSP in tumorigenesis, tumor diagnosis, genomic heterogeneity, methylation modifications, immune infiltration, and therapy response in pan-cancer. In addition, we constructed a risk score model to assessed the prognostic classification efficiency of IBSP using the co-expression genes of IBSP in osteosarcoma (OS), and analyzed the expression and role of IBSP in OS through a series of assays in vitro.

Results

IBSP was upregulated in various cancers compared to the paired normal tissues, and it was strongly correlated with the prognosis, pathological stage, diagnostic accuracy, genomic heterogeneity, methylation modification, immune infiltration, immune and checkpoint. Moreover, the predictive model we established in combination with the clinical characteristics of OS patients showed high survival predictive power in these individuals. The assays in vitro showed that IBSP promoted the proliferation, migration and invasion of OS cells, which further confirmed IBSP's role in cancers.

Conclusions

Our research revealed the multifunctionality of IBSP in the tumorigenesis, progression and therapy in various cancers, which demonstrated that IBSP may serve as a potential prognostic biomarker and a novel immunotherapy target in pan-cancer.

Cathepsin K: A Versatile Potential Biomarker and Therapeutic Target for Various Cancers

Cancer, a common malignant disease, is one of the predominant causes of diseases that lead to death. Additionally, cancer is often detected in advanced stages and cannot be radically cured. Consequently, there is an urgent need for reliable and easily detectable markers to identify and monitor cancer onset and progression as early as possible. Our aim was to systematically review the relevant roles of cathepsin K (CTSK) in various possible cancers in existing studies. CTSK, a well-known key enzyme in the bone resorption process and most studied for its roles in the effective degradation of the bone extracellular matrix, is expressed in various organs. Nowadays, CTSK has been involved in various cancers such as prostate cancer, breast cancer, bone cancer, renal carcinoma, lung cancer and other cancers. In addition, CTSK can promote tumor cells proliferation, invasion and migration, and its mechanism may be related to RANK/RANKL, TGF-β, mTOR and the Wnt/β-catenin signaling pathway. Clinically, some progress has been made with the use of cathepsin K inhibitors in the treatment of certain cancers. This paper reviewed our current understanding of the possible roles of CTSK in various cancers and discussed its potential as a biomarker and/or novel molecular target for various cancers.

IBSP, a potential recurrence biomarker, promotes the progression of colorectal cancer via Fyn/β-catenin signaling pathway

Colorectal cancer (CRC) is a frequently occurring digestive system cancer and postoperative tumor metastasis and recurrence are the main reasons for the failure of CRC treatment. The aim of this study was to identifying and validating key genes associated with metastatic recurrence of CRC. RNA expression of three datasets (GSE17538, GSE32323, and GSE29623) was used for biomarker discovery. We identified integrin-binding sialoprotein (IBSP) as a candidate biomarker which was validated in three clinical cohorts (GSE41258, GSE21510, and GSE39582) and our clinical specimens. The results suggested that IBSP expression significantly increased at mRNA and protein levels among CRC cases, which was associated with metastatic recurrence, metastasis, high risk of recurrence, and poor survival in CRC. Consistent results were obtained in CRC cells. The relative level of serum IBSP evidently increased among CRC patients relative to normal controls, and downregulated after operation. As suggested by gene set enrichment analysis (GSEA), the IBSP level was associated with cell-matrix adhesion in CRC. Functional experiments in vitro showed that IBSP promoted the growth and aggressiveness of CRC, and the potential mechanism by which IBSP promoted carcinogenesis of CRC was the abnormal activation of Fyn/β-catenin signaling pathway. To sum up, findings in the present work indicate that IBSP can serve as the candidate biomarker for the diagnosis, treatment, and prognosis of CRC.

Long Noncoding RNA HOXA11-AS and Transcription Factor HOXB13 Modulate the Expression of Bone Metastasis-Related Genes in Prostate Cancer

Long noncoding RNAs (lncRNAs) are emerging as critical regulators of gene expression, which play fundamental roles in cancer development. In this study, we found that homeobox A11 antisense RNA (HOXA11-AS), a highly expressed lncRNA in cell lines derived from prostate cancer bone metastases, promoted the cell invasion and proliferation of PC3 prostate cancer cells. Transcription factor homeobox B13 (HOXB13) was identified as an upstream regulator of HOXA11-AS.HOXA11-AS regulated bone metastasis-associated C-C motif chemokine ligand 2 (CCL2)/C-C chemokine receptor type 2 (CCR2) signaling in both PC3 prostate cancer cells and SaOS2 osteoblastic cells. The HOXB13/HOXA11-AS axis also regulated integrin subunits (ITGAV and ITGB1) specific to prostate cancer bone metastasis. HOXB13, in combination with HOXA11-AS, directly regulated the integrin-binding sialoprotein (IBSP) promoter. Furthermore, conditioned medium containing HOXA11-AS secreted from PC3 cells could induce the expression of CCL2 and IBSP in SaOS2 osteoblastic cells. These results suggest that prostate cancer HOXA11-AS and HOXB13 promote metastasis by regulation of CCL2/CCR2 cytokine and integrin signaling in autocrine and paracrine manners.

Role of the bone microenvironment in bone metastasis of malignant tumors - therapeutic implications

BACKGROUND

Bone is one of the most common sites for solid tumor metastasis. Bone metastasis of a malignant tumor seriously affects the quality of life and the overall survival of patients. Evidence has suggested that bone provides a favorable microenvironment that enables disseminated tumor cells to home, proliferate and colonize, leading to the formation of metastases. In the process of bone metastasis the bone microenvironment may be considered as an orchestra that plays a dissonant melody through blending (e.g. cross-talk between osteoclasts, osteoblasts and/or other cells), adding (e.g. a variety of biological factors) or taking away (e.g. blocking a specific pathway) players.

CONCLUSIONS

Here, we review the normal bone microenvironment, bone microenvironment-related factors that promote bone metastasis, as well as mechanisms underlying bone metastasis. In addition, we elude on directions for clinical bone metastasis management, focusing on potential therapeutic approaches to target bone microenvironment-related factors, including bisphosphonate, denosumab, CXCR4/CXCL12 antagonists and cathepsin K inhibitors.

Upregulation of IBSP Expression Predicts Poor Prognosis in Patients With Esophageal Squamous Cell Carcinoma

Esophageal squamous cell carcinoma (ESCC), which is characterized by invasiveness and poor prognosis, is the sixth most common leading cause of cancer-related death worldwide. Despite advances in multimodality therapy, ESCC mortality remains high, and an understanding of the molecular changes that lead to ESCC development and progression remains limited. In the present study, Integrin Binding Sialoprotein (IBSP) upregulation was found in 182 of 269 (67.7%) primary ESCC cells at the mRNA level by quantitative real-time polymerase chain reaction (qRT-PCR). Additionally, IHC staining further demonstrated that IBSP was upregulated in ESCC patients and IBSP protein upregulation was significantly related to the lymph node metastasis (P = 0.017), clinicopathologic stage (P = 0.001) and poor disease survival (P = 0.002). Moreover, functional studies illustrated that the IBSP gene can promote the proliferation and metastasis of ESCC cells. Furthermore, IBSP was found to regulate epithelial-mesenchymal transition (EMT), which promotes tumor cell metastasis. In conclusion, our study suggests that IBSP may be a valuable prognostic marker for ESCC patients.

Interleukin-8 promotes prostate cancer bone metastasis through upregulation of bone sialoprotein

The aim of the present study was to investigate whether interleukin-8 (IL-8) enhances the ability of prostate cancer bone metastasis by influencing the coding level of bone sialoprotein (BSP). Cultured prostate cancer cell lines LNCaP (androgen dependent) and DU145 (androgen independent) were divided into three groups: IL-8 treatment group; IL-8 receptor inhibitor (SB225002) treatment group; and control group. Western blotting and reverse transcription-quantitative polymerase chain reaction (RT-qPCR) were used to detect BSP protein and mRNA expression levels. Matrigel and bone adhesion experiments were used to detect the invasiveness of cancer cells and bone adhesion changes. Compared with the control group, western blotting and RT-qPCR results indicated that BSP protein and mRNA levels in LNCaP and DU145 were significantly upregulated following IL-8 treatment. Matrigel experiments indicated that following IL-8 treatment, the invasiveness of LNCaP and DU145 cells was significantly increased. The results of bone adhesion experiments indicated that following IL-8 treatment, the number of DU145 cells adhered to the surface of the bone was increased, compared with the control group. Following treatment of both cell lines with SB225002, western blotting and RT-qPCR results indicated that the expression levels of BSP protein and mRNA were significantly downregulated. Matrigel experiments indicated that following SB225002 treatment, the invasiveness of LNCaP and DU145 cells was significantly reduced. The number of DU145 cells adhered to the surface of the bone was reduced, compared with the untreated group. Therefore, IL-8 may promote prostate cancer bone metastasis by enhancing BSP regulation.

Bone resorption and bone metastasis risk

Breast cancer tumors have a tendency to metastasize to the bone. After development of a bone metastasis, the median survival time is 40 months. Currently, little is known about the modifiable risk factors for developing bone metastases in women diagnosed with breast cancer. One possible modifiable risk factor is increased bone resorption. Increased bone resorption is caused by an imbalance between osteoblasts and osteoclasts favoring osteoclast-driven bone resorption. Osteoclast activity results in the release of growth factors from the bony matrix that are requirement for successful breast cancer tumor cell proliferation within the bone. Mice studies have shown that mice that have been genetically engineered to have higher bone mineral density, and thus lower bone resorption, have a decreased incidence of bone metastases. Alternatively, mice genetically engineered to have lower bone mineral density or increased bone resorption have a higher incidence of bone metastases. In human studies, antiosteoporotic drugs have been shown to decrease osteoclast activity and prevent bone metastases. These studies suggest that increased osteoclast activity, which results in low bone mineral density, may be a modifiable risk factor for developing bone metastases in women with breast cancer. Women undergoing chemotherapy for breast cancer develop low bone mineral density in response to the direct effects of chemotherapeutic drugs on bone cells-including osteoclasts, osteoblasts, and osteocytes-and through the decrease in circulating estrogen as a result of chemotherapy-induced ovarian dysfunction. Therefore, it is important for future studies to determine the risk of developing bone metastases associated with increasing bone resorption as measured by low or decreasing bone mineral density in women diagnosed with breast cancer, as well as to determine the best intervention(s) to promote a balance between osteoclasts and osteoblasts to favor osteoblast activity during chemotherapy treatment.

Osteoclast proton pump regulator Atp6v1c1 enhances breast cancer growth by activating the mTORC1 pathway and bone metastasis by increasing V-ATPase activity

It is known that V-ATPases (vacuolar H⁺-ATPase) are involved in breast cancer growth and metastasis. Part of this action is similar to their role in osteoclasts, where they’re involved in extracellular acidification and matrix destruction; however, the roles of their subunits in cancer cell proliferation, signaling, and other pro-tumor actions are not well established. Analysis of TCGA data shows that V-ATPase subunit Atp6v1c1 is overexpressed or amplified in 34% of human breast cancer cases, with a 2-fold decrease in survival at 12 years. Whereas other subunits, such as Atp6v1c2 and Atp6v0a3, are overexpressed or genomically amplified less often, 6% each respectively, and have less impact on survival. Experiments show that lentiviral-shRNA mediated ATP6v1c1 knockdown in 4T1 mouse mammary cancer cells significantly reduces orthotopic and intraosseous tumor growth. ATP6v1c1 knockdown also significantly reduces tumor stimulated bone resorption through osteoclastogenesis at the bone and metastasis in vivo, as well as V-ATPase activity, proliferation, and mTORC1 activation in vitro. To generalize the effects of ATP6v1c1 knockdown on proliferation and mTORC1 activation we used human cancer cell lines - MCF-7, MDA-MB-231, and MDA-MB-435s. ATP6V1C1 knockdown reduced cell proliferation and impaired mTORC1 pathway activation in cancer cells but not in the untransformed cell line C3H10T1/2. Our study reveals that V-ATPase activity may be mediated through mTORC1 and that ATP6v1c1 can be knocked down to block both V-ATPase and mTORC1 activity.

Wenshen Zhuanggu formula effectively suppresses breast cancer bone metastases in a mouse Xenograft model

Wenshen Zhuanggu formula (WSZG) is a traditional Chinese medicine used as an adjuvant for the prevention of bone metastases in breast cancer patients. In this study we investigated the efficacy of WSZG in preventing bone metastases and the potential mechanisms in a mouse xenograft model of breast cancer bone metastases. This model was established by injection of human MDA-MB-231BO-Luc breast cancer cells alone or a mixture of the cancer cells with bone marrow-derived mesenchymal stem cells (BMSCs) into left ventricle of the heart in female nude mice. Then the mice were treated with WSZG (3.25, 6.5 or 13.0 mg·kg^-1·d^-1, ig) for four weeks, whereas zoledronic acid (100 μg/kg per week, ig) was used as a positive control. The occurrence and development of bone metastases were monitored via bioluminescent imaging, and bone lesions were assessed using micro-CT. Intracardiac injection of the mixture of MDA-MB-231BO-Luc breast cancer cells with BMSCs significantly facilitated the bone metastatic capacity of the breast cancer cells, and aggravated bone lesions in the mouse xenograft model of breast cancer bone metastases. Administration of WSZG dose-dependently inhibited the incidence and intensity of bone metastases and protected against bone lesions by suppressing osteoclast formation and tumor cell infiltration. Furthermore, administration of WSZG caused a marked reduction in the expression of CCL5/CCR5 and IL-17B/IL-17BR in bone metastatic tissues. The results demonstrate that WSZG exerts potential therapeutic effects in a mouse xenograft model of breast cancer bone metastases, which are partially mediated by weakening the interaction between BMSCs and breast cancer cells in the tumor microenvironment.

Targeting strategies of adenovirus‑mediated gene therapy and virotherapy for prostate cancer (Review)

Prostate cancer (PCa) poses a high risk to older men and it is the second most common type of male malignant tumor in western developed countries. Additionally, there is a lack of effective therapies for PCa at advanced stages. Novel treatment strategies such as adenovirus-mediated gene therapy and virotherapy involve the expression of a specific therapeutic gene to induce death in cancer cells, however, wild-type adenoviruses are also able to infect normal human cells, which leads to undesirable toxicity. Various PCa-targeting strategies in adenovirus-mediated therapy have been developed to improve tumor-targeting effects and human safety. The present review summarizes the relevant knowledge regarding available adenoviruses and PCa-targeting strategies. In addition, future directions in this area are also discussed. In conclusion, although they remain in the early stages of basic research, adenovirus-mediated gene therapy and virotherapy are expected to become important therapies for tumors in the future due to their potential targeting strategies.

miR-139-5p Represses BMSC Osteogenesis via Targeting Wnt/β-Catenin Signaling Pathway

Osteogenesis of mesenchymal stem cells (MSCs) has played a necessary role in the repair of bone. According to some reports, microRNAs participate in different physiological activity of the cells, including cell differentiation. This study investigated the function that miR-139-5p plays in the osteogenic differentiation of human bone marrow MSCs (hBMSCs). In addition to miR-139-5p, the effects of alkaline phosphatase (ALP), a membrane-bound metalloenzyme that is considered an early osteogenic differentiation marker, have also been investigated. Calcium-rich deposit (mineralization) is also a typical osteogenic differentiation marker that could be visualized by alizarin red S (ARS) staining. Inhibiting miR-139-5p notably promotes the hBMSC osteoblast differentiation, which, however, will be reduced by overexpressed miR-139-5p. This result has been made based on the alternations of ALP activity, ARS staining, as well as expression of osteogenic genes, including runt-related gene-2 (Runx2), collagen I (Col-1), and osteocalcin (OCN). miR-139-5p exerts its role in BMSC osteogenesis most probably through the Wnt/β-catenin pathway, by direct targeting CTNNB1 and frizzled 4 (FZD4), essential factors of Wnt/β-catenin pathway. In conclusion, according to the present study, inhibiting miR-139-5p could be a promising strategy in hBMSC osteogenesis.

Cancer Secretome May Influence BSP and DSP Expression in Human Salivary Gland Cells

One of the biggest challenges in managing head and neck cancers, especially salivary gland cancers, is the identification of secreted biomarkers of the disease that can be evaluated noninvasively. A relevant source of enriched tumor markers could potentially be found in the tumor secretome. Although numerous studies have evaluated secretomes from various cancers, the influence of the cancer secretome derived from salivary gland cancers on the behavior of normal cells has not yet been elucidated. Our data indicate that secretome derived from salivary gland cancer cells can influence the expression of two potential biomarkers of oral cancer-namely, bone sialoprotein (BSP) and dentin sialoprotein (DSP)-in normal salivary gland cells. Using routine immunohistochemistry, immunofluorescence, and immunoblotting techniques, we demonstrate an enrichment of BSP and DSP in human salivary gland (HSG) cancer tissue, unique localizations of BSP and DSP in HSG cancer cells, and enriched expression of BSP and DSP in normal salivary gland cells exposed to a cancer secretome. The secretome domain of the cancer microenvironment could alter signaling cascades responsible for normal cell proliferation, migration, and invasion, thus enhancing cancer cell survival and the potential for cancer progression. The cancer secretome may be critical in maintaining and stimulating "cancer-ness," thus potentially promoting specific hallmarks of metastasis.

The silencing of cathepsin K used in gene therapy for periodontal disease reveals the role of cathepsin K in chronic infection and inflammation

BACKGROUND AND OBJECTIVE

Periodontitis is a severe chronic inflammatory disease and one of the most prevalent non-communicable chronic diseases that affects the majority of the world's adult population. While great efforts have been devoted toward understanding the pathogenesis of periodontitis, there remains a pressing need for developing potent therapeutic strategies for targeting this dreadful disease. In this study, we utilized adeno-associated virus (AAV) expressing cathepsin K (Ctsk) small hairpin (sh)RNA (AAV-sh-Ctsk) to silence Ctsk in vivo and subsequently evaluated its impact in periodontitis as a potential therapeutic strategy for this disease.

MATERIAL AND METHODS

We used a known mouse model of periodontitis, in which wild-type BALB/cJ mice were infected with Porphyromonas gingivalis W50 in the maxillary and mandibular periodontium to induce the disease. AAV-sh-Ctsk was then administrated locally into the periodontal tissues in vivo, followed by analyses to assess progression of the disease.

RESULTS

AAV-mediated Ctsk silencing drastically protected mice (> 80%) from P. gingivalis-induced bone resorption by osteoclasts. In addition, AAV-sh-Ctsk administration drastically reduced inflammation by impacting the expression of many inflammatory cytokines as well as T-cell and dendritic cell numbers in periodontal lesions.

CONCLUSION

AAV-mediated Ctsk silencing can simultaneously target both the inflammation and bone resorption associated with periodontitis through its inhibitory effect on immune cells and osteoclast function. Thereby, AAV-sh-Ctsk administration can efficiently protect against periodontal tissue damage and alveolar bone loss, establishing this AAV-mediated local silencing of Ctsk as an important therapeutic strategy for effectively treating periodontal disease.

Runx2/DICER/miRNA Pathway in Regulating Osteogenesis

DICER is the central enzyme that cleaves precursor microRNAs (miRNAs) into 21-25 nucleotide duplex in cell lineage differentiation, identity, and survival. In the current study, we characterized the specific bone metabolism genes and corresponding miRNAs and found that DICER and Runt-related transcription factor 2 (Runx2) expressions increased simultaneously during osteogenic differentiation. Luciferase assay showed that Runx2 significantly increased the expression levels of DICER luciferase promoter reporter. Our analysis also revealed weaker DICER expression in embryos of Runx2 knock out mice (Runx2 -/-) compared with that of Runx2 +/- and Runx2 +/+ mice. We further established the calvarial bone critical-size defect (CSD) mouse model. The bone marrow stromal cells (BMSCs) transfected with siRNA targeting DICER were combined with silk scaffolds and transplanted into calvarial bone CSDs. Five weeks post-surgery, micro-CT analysis revealed impaired bone formation, and repairing in calvarial defects with the siRNA targeting DICER group. In conclusion, our results suggest that DICER is specifically regulated by osteogenic master gene Runx2 that binds to the DICER promoter. Consequently, DICER cleaves precursors of miR-335-5p and miR-17-92 cluster to form mature miRNAs, which target and decrease the Dickkopf-related protein 1 (DKK1), and proapoptotic factor BIM levels, respectively, leading to an enhanced Wnt/β-catenin signaling pathway. These intriguing results reveal a central mechanism underlying lineage-specific regulation by a Runx2/DICER/miRNAs cascade during osteogenic differentiation and bone development. Our study, also suggests a potential application of modulating DICER expression for bone tissue repair and regeneration. J. Cell. Physiol. 232: 182-191, 2017. © 2016 Wiley Periodicals, Inc.

Matricellular proteins as regulators of cancer metastasis to bone

Metastasis is the major cause of death in cancer patients, and a frequent site of metastasis for many cancers is the bone marrow. Therefore, understanding the mechanisms underlying the metastatic process is necessary for future prevention and treatment. The tumor microenvironment is now known to play a role in the metastatic cascade, both at the primary tumor and in metastatic sites, and includes both cellular and non-cellular components. The extracellular matrix (ECM) provides structural support and signaling cues to cells. One particular group of molecules associated with the ECM, known as matricellular proteins, modulate multiple aspects of tumor biology, including growth, migration, invasion, angiogenesis and metastasis. These proteins are also important for normal function in the bone by regulating bone formation and bone resorption. Recent studies have described a link between some of these proteins and metastasis of various tumors to the bone. The aim of this review is to summarize what is currently known about matricellular protein influence on bone metastasis. Particular attention to the contribution of both tumor cells and non-malignant cells in the bone has been given.

The role of the SIBLING, Bone Sialoprotein in skeletal biology - Contribution of mouse experimental genetics

Bone Sialoprotein (BSP) is a member of the "Small Integrin-Binding Ligand N-linked Glycoproteins" (SIBLING) extracellular matrix protein family of mineralized tissues. BSP has been less studied than other SIBLING proteins such as Osteopontin (OPN), which is coexpressed with it in several skeletal cell types. Here we review the contribution of genetically engineered mice (BSP gene knockout and overexpression) to the understanding of the role of BSP in the bone organ. The studies made so far highlight the role of BSP in skeletal mineralization, as well as its importance for proper osteoblast and osteoclast differentiation and activity, most prominently in primary/repair bone. The absence of BSP also affects the local environment of the bone tissue, in particular hematopoiesis and vascularization. Interestingly, lack of BSP induces an overexpression of OPN, and the cognate protein could be responsible for some aspects of the BSP gene knockout skeletal phenotype, while replacing BSP for some of its functions. Such interplay between the partly overlapping functions of SIBLING proteins, as well as the network of cross-regulations in which they are involved should now be the focus of further work.

Correlation between calcification and bone sialoprotein and osteopontin in papillary thyroid carcinoma

The correlation between calcification and papillary thyroid carcinoma has received increasing attention. We investigated the ability of bone sialoprotein (BSP) and osteopontin (OPN) protein levels to diagnose papillary thyroid carcinoma (PTC), and explored the correlation between BSP and OPN protein levels and calcification in PTC. Archival PTC specimens from patients with PTC with calcification and lateral cervical lymph node metastasis (LNM) were included in this retrospective immunohistochemical study. The protein levels of BSP and OPN were analysed immunohistochemically using routinely prepared tissue sections. PTC specimens from 66 patients with PTC were reviewed retrospectively (25 patients with histological calcification seen in paraffin sections, 41 patients without calcification; 35 patients with lateral cervical LNM, 31 patients without LNM). The percentage of samples that had cells that demonstrated positive protein staining differed significantly between PTC specimens, benign thyroid nodules, and adjacent normal follicular epithelium (BSP: 87.88%, 55.00%, and 42.50%, respectively; OPN: 83.33%, 70.00% and 50.00%, respectively). There was a significant difference in the immunohistochemical score (IHS) for BSP and OPN protein staining between PTC specimens with and without calcification (P < 0.05). The level of BSP protein staining was found to be significantly correlated with the level of OPN protein staining in PTC specimens. We conclude that the strong correlation between BSP and OPN and PTC suggests a role for BSP and OPN in calcification and tumor progression of PTC. BSP and OPN might be useful tumour markers for the diagnosis of PTC with limited value, because both of them had low specificity.

Adiponectin ameliorates experimental periodontitis in diet-induced obesity mice

Adiponectin is an adipokine that sensitizes the body to insulin. Low levels of adiponectin have been reported in obesity, diabetes and periodontitis. In this study we established experimental periodontitis in male adiponectin knockout and diet-induced obesity mice, a model of obesity and type 2 diabetes, and aimed at evaluating the therapeutic potential of adiponectin. We found that systemic adiponectin infusion reduced alveolar bone loss, osteoclast activity and infiltration of inflammatory cells in both periodontitis mouse models. Furthermore, adiponectin treatment decreased the levels of pro-inflammatory cytokines in white adipose tissue of diet-induced obesity mice with experimental periodontitis. Our in vitro studies also revealed that forkhead box O1, a key transcriptional regulator of energy metabolism, played an important role in the direct signaling of adiponectin in osteoclasts. Thus, adiponectin increased forkhead box O1 mRNA expression and its nuclear protein level in osteoclast-precursor cells undergoing differentiation. Inhibition of c-Jun N-terminal kinase signaling decreased nuclear protein levels of forkhead box O1. Furthermore, over-expression of forkhead box O1 inhibited osteoclastogenesis and led to decreased nuclear levels of nuclear factor of activated T cells c1. Taken together, this study suggests that systemic adiponectin application may constitute a potential intervention therapy to ameliorate type 2 diabetes-associated periodontitis. It also proposes that adiponectin inhibition of osteoclastogenesis involves forkhead box O1.

Bone sialoprotein and osteopontin in bone metastasis of osteotropic cancers

The mechanisms underlying malignant cell metastasis to secondary sites such as bone are complex and no doubt multifactorial. Members of the small integrin-binding ligand N-linked glycoproteins (SIBLINGs) family, particularly bone sialoprotein (BSP) and osteopontin (OPN), exhibit multiple activities known to promote malignant cell proliferation, detachment, invasion, and metastasis of several osteotropic cancers. The expression level of BSP and OPN is elevated in a variety of human cancers, particularly those that metastasize preferentially to the skeleton. Recent studies suggest that the "osteomimicry" of malignant cells is not only conferred by transmembrane receptors bound by BSP and OPN, but includes the "switch" in gene expression repertoire typically expressed in cells of skeletal lineage. Understanding the role of BSP and OPN in tumor progression, altered pathophysiology of bone microenvironment, and tumor metastasis to bone will likely result in development of better diagnostic approaches and therapeutic regimens for osteotropic malignant diseases.

Silencing of atp6v1c1 prevents breast cancer growth and bone metastasis

Previous studies have shown that Atp6v1c1, a regulator of the assembly of the V0 and V1 domains of the V-ATPase complex, is up-regulated in metastatic oral tumors. Despite these studies, the function of Atp6v1c1 in tumor growth and metastasis is still unknown. Atp6v1c1's expression in metastatic oral squamous cell carcinoma indicates that Atp6v1c1 has an important function in cancer growth and metastasis. We hypothesized that elevated expression of Atp6v1c1 is essential to cancer growth and metastasis and that Atp6v1c1 promotes cancer growth and metastasis through activation of V-ATPase activity. To test this hypothesis, a Lentivirus-mediated RNAi knockdown approach was used to study the function of Atp6v1c1 in mouse 4T1 mammary tumor cell proliferation and migration in vitro and cancer growth and metastasis in vivo. Our data revealed that silencing of Atp6v1c1 in 4T1 cancer cells inhibited lysosomal acidification and severely impaired 4T1 cell growth, migration, and invasion through Matrigel in vitro. We also show that Atp6v1c1 knockdown with Lenti-c1s3, a lentivirus targeting Atp6v1c1 for shRNA mediated knockdown, can significantly inhibit 4T1 xenograft tumor growth, metastasis, and osteolytic lesions in vivo. Our study demonstrates that Atp6v1c1 may promote breast cancer growth and bone metastasis through regulation of lysosomal V-ATPase activity, indicating that Atp6v1c1 may be a viable target for breast cancer therapy and silencing of Atp6v1c1 may be an innovative therapeutic approach for the treatment and prevention of breast cancer growth and metastasis.

BSP gene silencing inhibits migration, invasion, and bone metastasis of MDA-MB-231BO human breast cancer cells

Bone sialoprotein (BSP) has been implicated in a variety of physiological and pathophysiological events, including tumor cell invasion, bone homing, adhesion, and matrix degradation. To explore the potential involvement of BSP in human breast cancer cell invasion and metastasis, we used retrovirus-mediated RNAi to deplete BSP levels in the human bone-seeking breast cancer cell line MDA-MB-231BO (231BO) and established the 231BO-BSP27 and 231BO-BSP81 cell clones. Cell proliferation, colony formation, wound healing, and the ability to invade into matrigel of these BSP-depleted clones were all decreased. Both 231BO-BSP27 cells and 231BO-BSP81 cells showed a significant (15.4% and 28.6% respectively) reduction of bone metastatic potential following intracardiac injection as determined by X-ray detection and by hematoxylin and eosin staining. Moreover, the expression of integrins αvβ3 and β3 was decreased in the BSP-silenced cells whereas ectopic BSP expression increased the integrins αvβ3 and β3 levels. These results together suggest that BSP silencing decreased the integrin αvβ3 and β3 levels, in turn inhibiting cell migration and invasion and decreasing the ability of the cells to metastasize to bone.

RNAi-mediated silencing of Atp6i and Atp6i haploinsufficiency prevents both bone loss and inflammation in a mouse model of periodontal disease

Periodontal disease affects about 80% of adults in America, and is characterized by oral bacterial infection-induced gingival inflammation, oral bone resorption, and tooth loss. Periodontitis is also associated with other diseases such as rheumatoid arthritis, diabetes, and heart disease. Although many efforts have been made to develop effective therapies for this disease, none have been very effective and there is still an urgent need for better treatments and preventative strategies. Herein we explored for the first time the possibility that adeno-associated virus (AAV)-mediated RNAi knockdown could be used to treat periodontal disease with improved efficacy. For this purpose, we used AAV-mediated RNAi knockdown of Atp6i/TIRC7 gene expression to target bone resorption and gingival inflammation simultaneously. Mice were infected with the oral pathogen Porphyromonas gingivalis W50 (P. gingivalis) in the maxillary periodontium to induce periodontitis. We found that Atp6i depletion impaired extracellular acidification and osteoclast-mediated bone resorption. Furthermore, local injection of AAV-shRNA-Atp6i/TIRC7 into the periodontal tissues in vivo protected mice from P. gingivalis infection-stimulated bone resorption by >85% and decreased the T-cell number in periodontal tissues. Notably, AAV-mediated Atp6i/TIRC7 knockdown also reduced the expression of osteoclast marker genes and inflammation-induced cytokine genes. Atp6i(+/-) mice with haploinsufficiency were similarly protected from P. gingivalis infection-stimulated bone loss and gingival inflammation. This suggests that AAV-shRNA-Atp6i/TIRC7 therapeutic treatment may significantly improve the health of millions who suffer from P. gingivalis-mediated periodontal disease.

High bone sialoprotein (BSP) expression correlates with increased tumor grade and predicts a poorer prognosis of high-grade glioma patients

Objectives

To investigate the expression and prognostic value of bone sialoprotein (BSP) in glioma patients.

Methods

We determined the expression of BSP using real-time RT-PCR and immunohistochemistry in tissue microarrays containing 15 normal brain and 270 glioma samples. Cumulative survival was calculated by the Kaplan-Meier method and analyzed by the log-rank test. Univariate and multivariate analyses were performed by the stepwise forward Cox regression model.

Results

Both BSP mRNA and protein levels were significantly elevated in high-grade glioma tissues compared with those of normal brain and low-grade glioma tissues, and BSP expression positively correlated with tumor grade (P<0.001). Univariate and multivariate analysis showed high BSP expression was an independent prognostic factor for a shorter progression-free survival (PFS) and overall survival (OS) in both grade III and grade IV glioma patients [hazard ratio (HR) = 2.549 and 3.154 for grade III glioma, and HR = 1.637 and 1.574 for grade IV glioma, respectively]. Patients with low BSP expression had a significantly longer median OS and PFS than those with high BSP expression. Small extent of resection and lineage of astrocyte served as independent risk factors of both shorter PFS and OS in grade III glioma patients; GBM patients without O⁶-methylguanine (O⁶-meG) DNA methyltransferase (MGMT) methylation and Karnofsky performance score (KPS) less than 70 points were related to poor prognosis. Lack of radiotherapy related to shorter OS but not affect PFS in both grade III and grade IV glioma patients.

Conclusion

High BSP expression occurs in a significant subset of high-grade glioma patients and predicts a poorer outcome. The study identifies a potentially useful molecular marker for the categorization and targeted therapy of gliomas.

Diagnostic and prognostic use of bone turnover markers

The use of bone turnover markers in oncology includes monitoring of anticancer treatment in patients with malignant disease metastatic to the bones (therapeutic monitoring), predicting the risk of bone relapse in patients with a first diagnosis of potentially curative, early-stage malignant tumors (prognostic use), and making an early diagnosis of (microscopic) malignant bone disease in patients with a known malignant tumor to start early bone-targeted treatment and avoid skeletal-related events (diagnostic use). Concerning prognostic use, there is limited evidence for bone turnover markers to predict the occurrence of metachronous bone metastases in patients with early-stage malignant tumors, with serum PINP (N-terminal propeptide of procollagen type 1), ICTP (Carboxyterminal cross-linked telopeptide of type I collagen), bone sialoprotein (BSP), and tumor immunoexpression of BSP being the most promising candidates. Concerning diagnostic use, serum bone-specific alkaline phosphatise (BSAP), PINP and osteoprotegerin (OPG) were repeatedly shown to be associated with synchronous bone metastases in patients with breast or lung cancer, but sensitivity of these markers was too low to suggest that they might be preferred over conventional bone scans for the diagnosis of bone metastases. A somewhat higher sensitivity for the diagnosis of bone metastases was found for urinary NTx (N-terminal cross-linked telopeptide of type I collagen) and serum ICTP in solid tumor patients, serum TRAcP-5b (Tartrate-resistant acid phosphatase type 5b) in patients with breast cancer and serum BSAP, PINP and OPG in prostate cancer patients. Both prognostic and diagnostic use of bone turnover markers are reviewed in this chapter.

The anti-tumor agent sagopilone shows antiresorptive effects both in vitro and in vivo

Sagopilone, a fully synthetic epothilone and very potent anti-tumor agent, has proved to be efficient in inhibiting bone destruction and tumor burden in a mouse model of breast cancer bone metastasis. In addition to its antiproliferative effects, this study shows direct effects of sagopilone on bone resorption and osteoclast activity.

INTRODUCTION

Sagopilone, a novel fully synthetic third-generation epothilone, has proved to be efficient in inhibiting bone destruction and tumor burden in a mouse model of breast cancer bone metastasis. The aim of this study was to investigate whether the effect was primarily due to sagopilone's antiproliferative effect and consequent inhibition of tumor cell growth, or if sagopilone exerts direct effects on bone resorption and osteoclast activity.

METHODS

Sagopilone was studied and compared to paclitaxel in vitro in human osteoclast differentiation and activity cultures. For studying the potential of sagopilone for inhibiting bone resorption in vivo, a mouse model of ovariectomy (ovx)-induced osteoporosis was utilized.

RESULTS

Sagopilone inhibited osteoclast differentiation and activity more efficiently than paclitaxel and showed less cytotoxicity. Whereas sagopilone showed inhibitory effects on human osteoclast differentiation and activity already at 5 and 15 nM, respectively, paclitaxel started to show effects only at 20 and 100 nM concentrations, respectively. Sagopilone treatment increased BMD In the mouse ovx model even though a non-optimized dose was used which is effective in tumor-bearing mice.

CONCLUSION

This is the first study to evaluate sagopilone's effects on bone resorption in non-cancerous situation. The evidence that sagopilone is beneficial for bone will strengthen the status of sagopilone as an anti-cancer compound compared to other microtubule stabilizing agents.

Adiponectin inhibits osteoclastogenesis and bone resorption via APPL1-mediated suppression of Akt1

Adiponectin is an adipokine playing an important role in regulating energy homeostasis and insulin sensitivity. However, the effect of adiponectin on bone metabolism shows contradictory results according to different research studies. In this study femurs were isolated from genetically double-labeled mBSP9.0Luc/β-ACT-EGFP transgenic mice and were transplanted into adiponectin knock-out mice or wild type mice to investigate the effect of temporary exposure to adiponectin deficiency on bone growth and metabolism. We found that the growth of bone explants in adiponectin knock-out mice was significantly retarded. Histological analysis, microcomputed tomography analysis, and tartrate-resistant acid phosphatase staining revealed reduced trabecular bone volume, decreased cortical bone, and increased osteoclast number in bone explants in adiponectin knock-out mice. We then found that adiponectin inhibits RANKL-induced osteoclastogenesis from RAW264.7 cells and down-regulates RANKL-enhanced expressions of osteoclastogenic regulators including NFAT2, TRAF6, cathepsin K, and tartrate-resistant acid phosphatase. Adiponectin also increases osteoclast apoptosis and decreases survival/proliferation of osteoclast precursor cells. Using siRNA specifically targeting APPL1, the first identified adaptor protein of adiponectin signaling, we found that the inhibitory effect of adiponectin on osteoclasts was induced by APPL1-mediated down-regulation of Akt1 activity. In addition, overexpression of Akt1 successfully reversed adiponectin-induced inhibition in RANKL-stimulated osteoclast differentiation. In conclusion, adiponectin is important in maintaining the balance of energy metabolism, inflammatory responses, and bone formation.

Bone sialoprotein deficiency impairs osteoclastogenesis and mineral resorption in vitro

Bone sialoprotein (BSP) and osteopontin (OPN) belong to the small integrin-binding ligand N-linked glycoprotein (SIBLING) family, whose members interact with bone cells and bone mineral. Previously, we showed that BSP knockout (BSP(-/-) ) mice have a higher bone mass than wild type (BSP(+/+) ) littermates, with very low bone-formation activity and reduced osteoclast surfaces and numbers. Here we report that approximately twofold fewer tartrate-resistant acid phosphatase (TRACP)-positive cells and approximately fourfold fewer osteoclasts form in BSP(-/-) compared with BSP(+/+) spleen cell cultures. BSP(-/-) preosteoclast cultures display impaired proliferation and enhanced apoptosis. Addition of RGD-containing proteins restores osteoclast number in BSP(-/-) cultures to BSP(+/+) levels. The expression of osteoclast-associated genes is markedly altered in BSP(-/-) osteoclasts, with reduced expression of cell adhesion and migration genes (αV integrin chain and OPN) and increased expression of resorptive enzymes (TRACP and cathepsin K). The migration of preosteoclasts and mature osteoclasts is impaired in the absence of BSP, but resorption pit assays on dentine slices show no significant difference in pit numbers between BSP(+/+) and BSP(-/-) osteoclasts. However, resorption of mineral-coated slides by BSP(-/-) osteoclasts is markedly impaired but is fully restored by coating the mineral substrate with hrBSP and partly restored by hrOPN coating. In conclusion, lack of BSP affects both osteoclast formation and activity, which is in accordance with in vivo findings. Our results also suggest at least some functional redundancy between BSP and OPN that remains to be clarified.

Factors Affecting Residence Time of Mesenchymal Stromal Cells (MSC) Injected into the Myocardium

The therapeutic mechanism of mesenchymal stromal/stem cells (MSC) for the treatment of acute myocardial infarction is not well understood. Our goal was to get insights into this mechanism by analyzing the survival kinetics of allogeneic and syngeneic cell transplants under different tissue conditions. Two MSC cell banks, stably and equally expressing the luciferase reporter construct, were developed for these studies and injected directly to the myocardium of Lewis rat recipients under syngeneic or allogeneic transplantation conditions. Cell survival was monitored by real-time fashion for up to 2 weeks, using optical imaging device (IVIS, Xenogen Corp.). We found that both syngeneic and allogeneic grafts reduced significantly in size during the first week of transplantation, either in the normal or in the late infarcted heart (5 days after MI) and allotransplants became always smaller than syngeneic grafts during this period. Low dose of cyclosporine A treatment had a benefit on both allo- and syngeneic graft sizes, suggesting that multiple mechanisms play a role in early graft reduction. The MSC characteristic factors IL-6, IL-8, MCP-1, and VEGF were well above the control level in the heart tissue at 4 days after cell injection, suggesting that the peak therapeutic effect of MSC can be expected during the first week of the administration. Although allogeneic cells induced immunoglobulin production, their biological effects (cell survival, factor productions) are very similar to the syngeneic transplants and therefore they could deliver the same therapeutic effect as the syngeneic cells. Finally, freshly infarcted tissue (30 min) supported better the survival of MSC than late postischemic tissue (5 days) but only “off the shelf” allogeneic cell transplants fits with this treatment strategy.

Bone sialoprotein stimulates focal adhesion-related signaling pathways: role in migration and survival of breast and prostate cancer cells

Bone sialoprotein (BSP) is a secreted glycoprotein found in mineralized tissues however, BSP is aberrantly expressed in a variety of osteotropic tumors. Elevated BSP expression in breast and prostate primary carcinomas is directly correlated with increased bone metastases and tumor progression. In this study, the intracellular signaling pathways responsible for BSP-induced migration and tumor survival were examined in breast and prostate cancer cells (MDA-MB-231, Hs578T and PC3). Additionally, the effects of exogenous TGF-beta1 and EGF, cytokines associated with tumor metastasis and present in high-levels in the bone microenvironment, were examined in BSP-expressing cancer cells. Expression of BSP but not an integrin-binding mutant (BSP-KAE) in tumor cell lines resulted in increased levels of alpha(v)-containing integrins and number of mature focal adhesions. Adhesion of cells to recombinant BSP or the expression of BSP stimulated focal adhesion kinase and ERK phosphorylation, as well as activated AP-1-family proteins. Activation of these pathways by BSP expression increased the expression of the matrix metalloproteinases MMP-2, MMP-9, and MMP-14. The BSP-mediated activation of the FAK-associated pathway resulted in increased cancer cell invasion in a Matrigel-coated Boyden-chamber assay and increased cell survival upon withdrawal of serum. Addition of EGF or TGF-beta1 to the BSP-expressing cell lines significantly increased ERK phosphorylation, AP-1 activation, MMP-2 expression, cell migration and survival compared to untreated cells expressing BSP. This study thus defines the cooperative mechanisms by which BSP can enhance specific factors associated with a metastatic phenotype in tumor cell lines, an effect that is increased by circulating TGF-beta1 and EGF.

Applications of transgenics in studies of bone sialoprotein

Bone sialoprotein (BSP) is a major non-collagenous protein in mineralizing connective tissues such as dentin, cementum and calcified cartilage tissues. As a member of the Small Integrin-Binding Ligand, N-linked Glycoprotein (SIBLING) gene family of glycoproteins, BSP is involved in regulating hydroxyapatite crystal formation in bones and teeth, and has long been used as a marker gene for osteogenic differentiation. In the most recent decade, new discoveries in BSP gene expression and regulation, bone remodeling, bone metastasis, and bone tissue engineering have been achieved with the help of transgenic mice. In this review, we discuss these new discoveries obtained from the literatures and from our own laboratory, which were derived from the use of transgenic mouse mutants related to BSP gene or its promoter activity.