Breast cancer-derived Dickkopf1 inhibits osteoblast differentiation and osteoprotegerin expression: implication for breast cancer osteolytic bone metastases

Design and development of in-vitro co-culture device for studying cellular crosstalk in varied tissue microenvironment

Despite of being in different microenvironment, breast cancer cells influence the bone cells and persuade cancer metastasis from breast to bone. Multiple co-culture approaches have been explored to study paracrine signaling between these cells and to study the progression of cancer. However, lack of native tissue microenvironment remains a major bottleneck in existing co-culture technologies. Therefore, in the present study, a tumorigenic and an osteogenic microenvironment have been sutured together to create a multi-cellular environment and has been appraised to study cancer progression in bone tissue. The PCL-polystyrene and PCL-collagen fibrous scaffolds were characterized for tumorigenic and osteogenic potential induction on MDA-MB-231 and MC3T3-E1 cells respectively. Diffusion ability of crystal violet, glucose, and bovine serum albumin across the membrane were used to access the potential paracrine interaction facilitated by device. While in co-cultured condition, MDA-MB-231 cells showed EMT phenotype along with secretion of TNFα and PTHrP which lower down the expression of osteogenic markers including alkaline phosphatase, RUNX2, Osteocalcin and Osteoprotegerin. The cancer progression in bone microenvironment demonstrated the role and necessity of creating multiple tissue microenvironment and its contribution in studying multicellular disease progression and therapeutics.

The therapeutic effect of traditional Chinese medicine on breast cancer through modulation of the Wnt/β-catenin signaling pathway

Breast cancer, the most prevalent malignant tumor among women globally, is significantly influenced by the Wnt/β-catenin signaling pathway, which plays a crucial role in its initiation and progression. While conventional chemotherapy, the standard clinical treatment, suffers from significant drawbacks like severe side effects, high toxicity, and limited prognostic efficacy, Traditional Chinese Medicine (TCM) provides a promising alternative. TCM employs a multi-targeted therapeutic approach, which results in fewer side effects and offers a high potential for effective treatment. This paper presents a detailed analysis of the therapeutic impacts of TCM on various subtypes of breast cancer, focusing on its interaction with the Wnt/β-catenin signaling pathway. Additionally, it explores the effectiveness of both monomeric and compound forms of TCM in the management of breast cancer. We also discuss the potential of establishing biomarkers for breast cancer treatment based on key proteins within the Wnt/β-catenin signaling pathway. Our aim is to offer new insights into the prevention and treatment of breast cancer and to contribute to the standardization of TCM.

Single-cell Transcriptome Analysis Identifies Senescent Osteocytes as Contributors to Bone Destruction in Breast Cancer Metastasis

Breast cancer bone metastases increase fracture risk and are a major cause of morbidity and mortality among women. Upon colonization by tumor cells, the bone microenvironment undergoes profound reprogramming to support cancer progression that disrupts the balance between osteoclasts and osteoblasts, leading to bone lesions. Whether such reprogramming affects matrix-embedded osteocytes remains poorly understood. Here, we demonstrate that osteocytes in breast cancer bone metastasis develop premature senescence and a distinctive senescence-associated secretory phenotype (SASP) that favors bone destruction. Single-cell RNA sequencing identified osteocytes from mice with breast cancer bone metastasis enriched in senescence and SASP markers and pro-osteoclastogenic genes. Using multiplex in situ hybridization and AI-assisted analysis, we detected osteocytes with senescence-associated distension of satellites, telomere dysfunction, and p16Ink4a expression in mice and patients with breast cancer bone metastasis. In vitro and ex vivo organ cultures showed that breast cancer cells promote osteocyte senescence and enhance their osteoclastogenic potential. Clearance of senescent cells with senolytics suppressed bone resorption and preserved bone mass in mice with breast cancer bone metastasis. These results demonstrate that osteocytes undergo pathological reprogramming by breast cancer cells and identify osteocyte senescence as an initiating event triggering bone destruction in breast cancer metastases.

Overexpression of Corin Ameliorates Kidney Fibrosis through Inhibition of Wnt/β-Catenin Signaling in Mice

The Wnt/β-catenin pathway represents a promising therapeutic target for mitigating kidney fibrosis. Corin possesses the homologous ligand binding site [Frizzled-cysteine-rich domain (Fz-CRD)] similar to Frizzled proteins, which act as receptors for Wnt. The Fz-CRD has been found in eight different proteins, all of which, except for corin, are known to bind Wnt and regulate its signal transmission. We hypothesized that corin may inhibit the Wnt/β-catenin signaling pathway and thereby reduce fibrogenesis. Reduced expression of corin along with the increased activity of Wnt/β-catenin signaling was found in unilateral ureteral obstruction (UUO) and ureteral ischemia/reperfusion injury (UIRI) models. In vitro, corin bound to the Wnt1 through its Fz-CRDs and inhibit the Wnt1 function responsible for activating β-catenin. Transforming growth factor-β1 inhibited corin expression, accompanied by activation of β-catenin; conversely, overexpression of corin attenuated the fibrotic effects of transforming growth factor-β1. In vivo, adenovirus-mediated overexpression of corin attenuated the progression of fibrosis, which was potentially associated with the inhibition of Wnt/β-catenin signaling and the down-regulation of its target genes after UUO and UIRI. These results suggest that corin acts as an antagonist that protects the kidney from pathogenic Wnt/β-catenin signaling and from fibrosis following UUO and UIRI.

Bone metastatic mammary tumor cell-derived extracellular vesicles inhibit osteoblast maturation via JNK signaling

The metastases of breast cancer to bone often cause osteolytic lesions not only by stimulating osteoclasts to resorb the bone but also by inhibiting osteoblasts from bone formation. Although tumor cell-derived extracellular vesicles (EVs) promote osteoclast differentiation and bone resorption, their roles in osteoblast differentiation and functions have not been elucidated. In this study, we investigated the effects of breast cancer cell-derived EVs on osteoblast differentiation and functions in vitro. We found that upon osteogenic induction, 4T1 bone metastatic mouse mammary tumor cell-derived EVs (4T1-EVs) were inhibited matrix mineralization of ST2 mouse bone marrow stromal cells. Temporal expression analysis of osteoblast marker genes, including runt-related transcription factor 2 (Runx2), osterix (Osx), alkaline phosphatase (Alp), collagen type I (Col1a1), bone sialoprotein (Bsp), and osteocalcin (Bglap) revealed that 4T1-EVs decreased their expression during the late stage of osteoblast differentiation. Elevated levels of c-Jun N-terminal kinase (JNK) phosphorylation, upon osteogenic induction, were diminished by 4T1-EVs, significantly. In contrast, the nullification of reduced JNK phosphorylation by anisomycin, a potent JNK activator, increased the expression levels of osteoblast differentiation markers. Overall, our data indicated that 4T1-EVs affect osteoblast maturation, at least partially, through the regulation of JNK activity, which provides novel insights into the pathological impact of osteolytic bone metastasis and the role of EVs in osteoblast differentiation.

Unravelling transcriptomic complexity in breast cancer through modulation of DARPP-32 expression and signalling pathways

DARPP-32 is a key regulator of protein-phosphatase-1 (PP-1) and protein kinase A (PKA), with its function dependent upon its phosphorylation state. We previously identified DKK1 and GRB7 as genes with linked expression using Artificial Neural Network (ANN) analysis; here, we determine protein expression in a large cohort of early-stage breast cancer patients. Low levels of DARPP-32 Threonine-34 phosphorylation and DKK1 expression were significantly associated with poor patient prognosis, while low levels of GRB7 expression were linked to better survival outcomes. To gain insight into mechanisms underlying these associations, we analysed the transcriptome of T47D breast cancer cells following DARPP-32 knockdown. We identified 202 differentially expressed transcripts and observed that some overlapped with genes implicated in the ANN analysis, including PTK7, TRAF5, and KLK6, amongst others. Furthermore, we found that treatment of DARPP-32 knockdown cells with 17β-estradiol or PKA inhibitor fragment (6-22) amide led to the differential expression of 193 and 181 transcripts respectively. These results underscore the importance of DARPP-32, a central molecular switch, and its downstream targets, DKK1 and GRB7 in breast cancer. The discovery of common genes identified by a combined patient/cell line transcriptomic approach provides insights into the molecular mechanisms underlying differential breast cancer prognosis and highlights potential targets for therapeutic intervention.

DKK1 is a predictive biomarker for response to DKN-01: Results of a phase 2 basket study in women with recurrent endometrial carcinoma

PURPOSE

Dickkopf-1 (DKK1) is a Wnt signaling modulator promoting tumor growth, metastasis, angiogenesis, and immunosuppression by regulating innate immunity. DKK1 is over-expressed in gynecologic cancers and is associated with shortened survival. DKN-01 is a humanized monoclonal antibody with DKK1 neutralizing activity that may provide clinical benefit to patients whose tumors have overexpression of DKK1 or Wnt genetic alterations.

METHODS

We conducted an open-label, Phase 2 basket study with 2-stage design in patients with endometrial carcinoma (EC) and platinum-resistant/refractory epithelial ovarian cancer. DKN-01 was administered either as monotherapy or in combination with weekly paclitaxel at investigator's discretion. All patients underwent NGS testing prior to enrollment; tumor tissue was also tested for DKK1 expression by RNAscope pre-treatment and after cycle 1 if available. At least 50% of patients were required to have a Wnt signaling alteration either directly or tangentially. This publication reports results from the EC population overall and by DKK1-expression.

RESULTS

DKN-01 monotherapy and in combination with paclitaxel was more effective in patients with high DKK1-expressing tumors compared to low-expressing tumors. DKN-01 monotherapy demonstrated an objective response rate [ORR] of 25.0% vs. 0%; disease control rate [DCR] of 62.5% vs. 6.7%; median progression-free survival [PFS] was 4.3 vs. 1.8 months, and overall survival [OS] was 11.0 vs. 8.2 months in DKK1-high vs DKK1-low patients. Similarly, DKN-01 in combination with paclitaxel demonstrated greater clinical activity in patients with DKK1-high tumors compared to DKK1-low tumors: DCR was 55% vs. 44%; median PFS was 5.4 vs. 1.8 months; and OS was 19.1 vs. 10.1 months. Wnt activating mutations correlated with higher DKK1 expression. DKN-01 was well tolerated as a monotherapy and in combination with paclitaxel.

CONCLUSIONS

Collectively, data demonstrates promising clinical activity of a well-tolerated drug, DKN-01, in EC patients with high tumoral DKK1 expression which frequently corresponded to the presence of a Wnt activating mutation. Future development will focus on using DKN-01 in DKK1-high EC patients in combination with immunotherapy.

Patient-Derived Breast Cancer Bone Metastasis In Vitro Model Using Bone-Mimetic Nanoclay Scaffolds

The unavailability of reliable models for studying breast cancer bone metastasis is the major challenge associated with poor prognosis in advanced-stage breast cancer patients. Breast cancer cells tend to preferentially disseminate to bone and colonize within the remodeling bone to cause bone metastasis. To improve the outcome of patients with breast cancer bone metastasis, we have previously developed a 3D in vitro breast cancer bone metastasis model using human mesenchymal stem cells (hMSCs) and primary breast cancer cell lines (MCF-7 and MDAMB231), recapitulating late-stage of breast cancer metastasis to bone. In the present study, we have tested our model using hMSCs and patient-derived breast cancer cell lines (NT013 and NT023) exhibiting different characteristics. We investigated the effect of breast cancer metastasis on bone growth using this 3D in vitro model and compared our results with previous studies. The results showed that NT013 and NT023 cells exhibiting hormone-positive and triple-negative characteristics underwent mesenchymal to epithelial transition (MET) and formed tumors in the presence of bone microenvironment, in line with our previous results with MCF-7 and MDAMB231 cell lines. In addition, the results showed upregulation of Wnt-related genes in hMSCs, cultured in the presence of excessive ET-1 cytokine released by NT013 cells, while downregulation of Wnt-related genes in the presence of excessive DKK-1, released by NT023 cells, leading to stimulation and abrogation of the osteogenic pathway, respectively, ultimately mimicking different types of bone lesions in breast cancer patients.

Advancing Treatment of Bone Metastases through Novel Translational Approaches Targeting the Bone Microenvironment

Bone metastases represent a lethal condition that frequently occurs in solid tumors such as prostate, breast, lung, and renal cell carcinomas, and increase the risk of skeletal-related events (SREs) including pain, pathologic fractures, and spinal cord compression. This unique metastatic niche consists of a multicellular complex that cancer cells co-opt to engender bone remodeling, immune suppression, and stromal-mediated therapeutic resistance. This review comprehensively discusses clinical challenges of bone metastases, novel preclinical models of the bone and bone marrow microenviroment, and crucial signaling pathways active in bone homeostasis and metastatic niche. These studies establish the context to summarize the current state of investigational agents targeting BM, and approaches to improve BM-targeting therapies. Finally, we discuss opportunities to advance research in bone and bone marrow microenvironments by increasing complexity of humanized preclinical models and fostering interdisciplinary collaborations to translational research in this challenging metastatic niche.

Mechanisms, Diagnosis and Treatment of Bone Metastases

Bone and bone marrow are among the most frequent metastatic sites of cancer. The occurrence of bone metastasis is frequently associated with a dismal disease outcome. The prevention and therapy of bone metastases is a priority in the treatment of cancer patients. However, current therapeutic options for patients with bone metastatic disease are limited in efficacy and associated with increased morbidity. Therefore, most current therapies are mainly palliative in nature. A better understanding of the underlying molecular pathways of the bone metastatic process is warranted to develop novel, well-tolerated and more successful treatments for a significant improvement of patients' quality of life and disease outcome. In this review, we provide comparative mechanistic insights into the bone metastatic process of various solid tumors, including pediatric cancers. We also highlight current and innovative approaches to biologically targeted therapy and immunotherapy. In particular, we discuss the role of the bone marrow microenvironment in the attraction, homing, dormancy and outgrowth of metastatic tumor cells and the ensuing therapeutic implications. Multiple signaling pathways have been described to contribute to metastatic spread to the bone of specific cancer entities, with most knowledge derived from the study of breast and prostate cancer. However, it is likely that similar mechanisms are involved in different types of cancer, including multiple myeloma, primary bone sarcomas and neuroblastoma. The metastatic rate-limiting interaction of tumor cells with the various cellular and noncellular components of the bone-marrow niche provides attractive therapeutic targets, which are already partially exploited by novel promising immunotherapies.

Mediterranean Diet Food Components as Possible Adjuvant Therapies to Counteract Breast and Prostate Cancer Progression to Bone Metastasis

Bone metastasis is a serious and often lethal complication of particularly frequent carcinomas, such as breast and prostate cancers, which not only reduces survival but also worsens the patients’ quality of life. Therefore, it is important to find new and/or additional therapeutic possibilities that can counteract the colonization of bone tissue. High adherence to the Mediterranean diet (MD) is effective in the prevention of cancer and improves cancer patients’ health, thus, here, we considered its impact on bone metastasis. We highlighted some molecular events relevant for the development of a metastatic phenotype in cancer cells and the alterations of physiological bone remodeling, which occur during skeleton colonization. We then considered those natural compounds present in MD foods with a recognized role to inhibit or reverse the metastatic process both in in vivo and in vitro systems, and we reported the identified mechanisms of action. The knowledge of this bioactivity by the dietary components of the MD, together with its wide access to all people, could help not only to maintain healthy status but also to improve the quality of life of patients with bone metastases.

Mesenchymal Stromal Cells in Neuroblastoma: Exploring Crosstalk and Therapeutic Implications

Neuroblastoma (NB) is the second most common solid cancer in childhood, accounting for 15% of cancer-related deaths in children. In high-risk NB patients, the majority suffers from metastasis. Despite intensive multimodal treatment, long-term survival remains <40%. The bone marrow (BM) is among the most common sites of distant metastasis in patients with high-risk NB. In this environment, small populations of tumor cells can persist after treatment (minimal residual disease) and induce relapse. Therapy resistance of these residual tumor cells in BM remains a major obstacle for the cure of NB. A detailed understanding of the microenvironment and its role in tumor progression is of utmost importance for improving the treatment efficiency of NB. In BM, mesenchymal stromal cells (MSCs) constitute an important part of the microenvironment, where they support hematopoiesis and modulate immune responses. Their role in tumor progression is not completely understood, especially for NB. Although MSCs have been found to promote epithelial-mesenchymal transition, tumor growth, and metastasis and to induce chemoresistance, some reports point toward a tumor-suppressive effect of MSCs. In this review, we aim to compile current knowledge about the role of MSCs in NB development and progression. We evaluate arguments that depict tumor-supportive versus -suppressive properties of MSCs in the context of NB and give an overview of factors involved in MSC-NB crosstalk. A focus lies on the BM as a metastatic niche, since that is the predominant site for NB metastasis and relapse. Finally, we will present opportunities and challenges for therapeutic targeting of MSCs in the BM microenvironment.

Bone metastasis: mechanisms, therapies, and biomarkers

Skeletal metastases are frequent complications of many cancers, causing bone complications (fractures, bone pain, disability) that negatively affect the patient's quality of life. Here, we first discuss the burden of skeletal complications in cancer bone metastasis. We then describe the pathophysiology of bone metastasis. Bone metastasis is a multistage process: long before the development of clinically detectable metastases, circulating tumor cells settle and enter a dormant state in normal vascular and endosteal niches present in the bone marrow, which provide immediate attachment and shelter, and only become active years later as they proliferate and alter the functions of bone-resorbing (osteoclasts) and bone-forming (osteoblasts) cells, promoting skeletal destruction. The molecular mechanisms involved in mediating each of these steps are described, and we also explain how tumor cells interact with a myriad of interconnected cell populations in the bone marrow, including a rich vascular network, immune cells, adipocytes, and nerves. We discuss metabolic programs that tumor cells could engage with to specifically grow in bone. We also describe the progress and future directions of existing bone-targeted agents and report emerging therapies that have arisen from recent advances in our understanding of the pathophysiology of bone metastases. Finally, we discuss the value of bone turnover biomarkers in detection and monitoring of progression and therapeutic effects in patients with bone metastasis.

Pizotifen inhibits the proliferation and invasion of gastric cancer cells

Gastric cancer is the fifth most common malignancy and the third highest cause of cancer-associated mortality worldwide. Therefore, research on the pathogenesis of gastric cancer is of utmost importance. It has been reported that aberrant activation of the Wnt/β-catenin signaling pathway is involved in the occurrence and development of gastric cancer. In the present study, it was found that pizotifen could inhibit the viability of gastric cancer cell lines MNK45 and AGS cells in a dose-dependent manner. Pizotifen treatment suppressed cell migration and invasion in MNK45 and AGS cells, whilst also inducing apoptosis. Western blot analysis demonstrated that pizotifen blocked the expression of Wnt3a, β-catenin and N-cadherin, whilst increasing E-cadherin expression. In addition, BML-284, a pharmacological Wnt signaling activator, partially reversed the changes in the expression levels of β-catenin, N-cadherin and E-cadherin in MNK45 and AGS cells induced by pizotifen. Collectively, these findings suggested that pizotifen demonstrates potential as a novel anti-cancer drug for the treatment of gastric cancer by inhibiting the Wnt/β-catenin pathway.

Wnt/β-Catenin Signaling Pathway Regulates Osteogenesis for Breast Cancer Bone Metastasis: Experiments in an In Vitro Nanoclay Scaffold Cancer Testbed

Breast cancer shows a high affinity toward bone, causing bone-related complications, leading to a poor clinical prognosis. The Wnt/β-catenin signaling pathway has been well-documented for the bone regenerative process; however, the regulation of the Wnt/β-catenin pathway in breast cancer bone metastasis is poorly explored. Here, we report that the Wnt/β-catenin signaling pathway has a significant effect on osteogenesis during breast cancer bone metastasis. In this study, we have created a 3D in vitro breast cancer bone metastatic microenvironment using nanoclay-based scaffolds along with osteogenically differentiated human mesenchymal stem cells (MSCs) and human breast cancer cells (MCF-7 and MDA-MB-231). The results showed upregulation in expressions of Wnt-related factors (Wnt-5a, β-catenin, AXIN2, and LRP5) in sequential cultures of MSCs with MCF-7 as compared to sequential cultures of MSCs with MDA-MB-231. Sequential cultures of MSCs with MCF-7 also showed higher β-catenin expression on the protein levels than sequential cultures of MSCs with MDA-MB-231. Stimulation of Wnt/β-catenin signaling in sequential cultures of MSCs with MCF-7 by ET-1 resulted in increased bone formation, whereas inactivation of Wnt/β-catenin signaling by DKK-1 displayed a significant decrease in bone formation, mimicking bone lesions in breast cancer patients. These data collectively demonstrate that Wnt/β-catenin signaling governs osteogenesis within the tumor-harboring bone microenvironment, leading to bone metastasis. The nanoclay scaffold provides a unique testbed approach for analysis of the pathways of cancer metastasis.

New Insights about the Wnt/β-Catenin Signaling Pathway in Primary Bone Tumors and Their Microenvironment: A Promising Target to Develop Therapeutic Strategies?

Osteosarcoma and Ewing sarcoma are the most common malignant primary bone tumors mainly occurring in children, adolescents and young adults. Current standard therapy includes multidrug chemotherapy and/or radiation specifically for Ewing sarcoma, associated with tumor resection. However, patient survival has not evolved for the past decade and remains closely related to the response of tumor cells to chemotherapy, reaching around 75% at 5 years for patients with localized forms of osteosarcoma or Ewing sarcoma but less than 30% in metastatic diseases and patients resistant to initial chemotherapy. Despite Ewing sarcoma being characterized by specific EWSR1-ETS gene fusions resulting in oncogenic transcription factors, currently, no targeted therapy could be implemented. It seems even more difficult to develop a targeted therapeutic strategy in osteosarcoma which is characterized by high complexity and heterogeneity in genomic alterations. Nevertheless, the common point between these different bone tumors is their ability to deregulate bone homeostasis and remodeling and divert them to their benefit. Therefore, targeting different actors of the bone tumor microenvironment has been hypothesized to develop new therapeutic strategies. In this context, it is well known that the Wnt/β-catenin signaling pathway plays a key role in cancer development, including osteosarcoma and Ewing sarcoma as well as in bone remodeling. Moreover, recent studies highlight the implication of the Wnt/β-catenin pathway in angiogenesis and immuno-surveillance, two key mechanisms involved in metastatic dissemination. This review focuses on the role played by this signaling pathway in the development of primary bone tumors and the modulation of their specific microenvironment.

Sclerostin inhibition alleviates breast cancer-induced bone metastases and muscle weakness

Breast cancer bone metastases often cause a debilitating non-curable condition with osteolytic lesions, muscle weakness and a high mortality. Current treatment comprises chemotherapy, irradiation, surgery and anti-resorptive drugs that restrict but do not revert bone destruction. In metastatic breast cancer cells, we determined the expression of sclerostin, a soluble Wnt inhibitor that represses osteoblast differentiation and bone formation. In mice with breast cancer bone metastases, pharmacological inhibition of sclerostin using an anti-sclerostin antibody (Scl-Ab) reduced metastases without tumor cell dissemination to other distant sites. Sclerostin inhibition prevented the cancer-induced bone destruction by augmenting osteoblast-mediated bone formation and reducing osteoclast-dependent bone resorption. During advanced disease, NF-κB and p38 signaling was increased in muscles in a TGF-β1-dependent manner, causing muscle fiber atrophy, muscle weakness and tissue regeneration with an increase in Pax7-positive satellite cells. Scl-Ab treatment restored NF-κB and p38 signaling, the abundance of Pax7-positive cells and ultimately muscle function. These effects improved the overall health condition and expanded the life span of cancer-bearing mice. Together, these results demonstrate that pharmacological inhibition of sclerostin reduces bone metastatic burden and muscle weakness with a prolongation of the survival time. This might provide novel options for treating musculoskeletal complications in breast cancer patients. .

EBV miR-BART10-3p Promotes Cell Proliferation and Migration by Targeting DKK1

In Epstein-Barr virus (EBV)-infected epithelial cancers, BamHI A rightward transcript (BART) miRNAs are highly expressed. However, only a few target genes of BART miRNAs have been investigated. Our mRNA microarray data showed that DKK1 was markedly down-regulated in EBV-associated gastric carcinoma (EBVaGC) cells. Using luciferase reporter assay we tested whether miR-BART10-3p regulates DKK1 by directly targeting the 3'-UTR of DKK1 mRNA. We observed that miR-BART10-3p transfection decreased DKK1 expression, while an LNA inhibitor of miR-BART10-3p (LNA-miR-BART10-3p(i)) increased DKK1 expression. Furthermore, miR-BART10-3p and siDKK1 promoted cell proliferation and migration. In contrast, transfecting GC cells with LNA-miR-BART10-3p(i) or DKK1 over expression vector suppressed cell proliferation and migration. Our results suggest that miR-BART10-3p may be involved in the tumor progression of EBVaGC by targeting DKK1.

Dkk1 involvement and its potential as a biomarker in pancreatic ductal adenocarcinoma

Dickkopf-1 (Dkk1)'s dysregulation has been implicated in the pathogenesis of a variety of cancers. It is part of the Dkk family of proteins that includes Dkk2, Dkk3 and Dkk4. This family of secreted proteins shares similar conserved cysteine domains and inhibits the Wnt/b-catenin pathway by causing proteasomal B-catenin degradation, inducing apoptosis, and preventing cell proliferation. Pancreatic ductal adenocarcinoma (PDAC) is the 4th leading cause of cancer mortality in the United States due to the late stage of diagnosis and the limited effectiveness of current therapy. Dkk1 is found increased in PADC patients' specimens and serum. Dkk1 can be a promising biomarker specific to PDAC, which has the potential to increase PDAC survival rates through improving early stage detection and monitoring progression compared to current biomarker gold standards. In addition, recent studies suggest that Dkk1 could be an excellent target for cancer immunotherapy. Interestingly, Dkk1-CKAP4-PI3K/AKT signal pathway also plays role in pancreatic cancer cell proliferation. In this review, we present the multiple mechanisms of Dkk1 in PDAC studied thus far and explore its function, regulation, and clinical applications in gynecological cancers including pancreatic ductal adenocarcinoma (PDAC), breast, ovarian, cervical, and endometrial cancer. Further research into Dkk1's mechanism and use as a diagnostic tool, alone or in combination with other biomarkers, could prove clinically useful for better understanding the pathology of PDAC and improving its early detection and treatment.

Prognostic value of DKK2 from the Dickkopf family in human breast cancer

Breast cancer is one of the most frequently diagnosed types of cancer with a high mortality and malignancy rate in women worldwide. The Dickkopf (DKK) protein family, as a canonical Wnt/β-catenin pathway antagonist, has been implicated in both physiological and pathological processes. This study aimed to comprehensively characterize the prognostic value and elucidate the mechanisms of DKKs in breast cancer and its subtypes. Firstly, DKK mRNA expression and corresponding outcome were analyzed by means of the Gene Expression-Based Outcome for Breast Cancer Online (GOBO) platform based on PAM50 intrinsic breast cancer subtypes. Subsequently, we extracted breast cancer datasets from the Cancer Genome Atlas (TCGA) and Molecular Taxonomy of Breast Cancer International Consortium (METABRIC) to validate the expression profile and prognostic values from the GOBO platform. Moreover, a protein-protein network was created and functional enrichment was conducted to explore the underlying mechanisms of action of the DKKs. In addition, we uncovered the genetic and epigenetic alterations of DKK2 in breast cancer. The main finding of this study was the differential roles of DKKs in the PAM50 subtypes of breast cancer analyzed. The overall trend was that a high level of DKK2 was associated with a good survival in breast cancer, although it played an opposite role in the Normal-like subtype. We also found that DKK2 carried out its functions through multiple signaling pathways, not limited to the Wnt/β-catenin cascade in breast cancer. Finally, we used our own data to validate the bioinformatics analysis data for DKK2 by RT-qPCR. Taken together, our findings suggest that DKK2 may be a potential prognostic biomarker for the Normal-like subtype of breast cancer. However, the prognostic role of DKKs in the subtypes of breast cancer still requires validation by larger sample studies in the future.

Dickkopf-1 (Dkk1) protein expression in breast cancer with special reference to bone metastases

Dysregulation of the Wnt inhibitor dickkopf-1 protein (Dkk1) has been reported in a variety of cancers. In addition, it has been linked to the progression of malignant bone disease by impairing osteoblast activity. This study investigated serum- and tissue levels of Dkk1 in breast cancer patients with- or without bone metastases. Serum Dkk1 levels were measured by ELISA in 89 breast cancer patients and 86 healthy women. Tissue levels of Dkk1 and β-catenin, a major downstream component of Wnt transduction pathway, were tested with immunohistochemical staining in 143 different tissues, including adjacent non-tumoral breast tissues, primary breast tumours, lymph nodes metastases, and bone metastases. Serum levels of Dkk1 were significantly increased in breast cancer patients without metastases compared with healthy controls and even more increased in patients with bone metastases. Tissue expression of Dkk1 was positive in 70% of tested primary breast cancer tissues and demonstrated significant correlation with histological type and PR status. Less frequent expression of Dkk1 was found in lymph nodes metastases and bone metastases compared with adjacent non-tumoral breast tissues and primary breast tumours. Tissue expression of β-catenin was positive in the vast majority of all tested tissue types indicating activated Wnt/β-catenin signalling. Our results suggested that Wnt/β-catenin signalling in breast tumours and their secondary lymph nodes- and bone metastases is dysregulated and this could be related to aberrant Dkk1 expression levels. Hence, Dkk1 protein might provide insights into the continued development of novel comprehensive and therapeutic strategies for breast cancer and its bone metastases.

Postnatal Skeletal Deletion of Dickkopf-1 Increases Bone Formation and Bone Volume in Male and Female Mice, Despite Increased Sclerostin Expression

The Wnt antagonist Dickkopf-1 (Dkk1) is a negative regulator of osteoblast function and bone mass. However, because of the lack of appropriate models, many aspects of its role in the regulation of postnatal bone turnover and its cellular source have remained unknown. In this study, we deleted Dkk1 postnatally and in different cell types using various Cre-drivers (Rosa26-ERT2-Cre, Osx-cre, Dmp1-Cre) and assessed to which extent cells of the osteoblastic lineage contribute to the effects of Dkk1 on bone turnover and homeostasis. Female and male mice were examined at 12 weeks of age. Mice with a global or cell type-specific deletion of Dkk1 showed a two- to threefold higher bone volume compared with their Cre-negative littermates. The mineral apposition rate and the bone formation rate were increased two- to fourfold in all three mouse lines, despite a significant increase in systemic and skeletal levels of sclerostin. Dkk1 deletion further reduced the number of osteoclasts about twofold, which was accompanied by a strong decrease in the receptor activator of nuclear factor-κB ligand/osteoprotegerin mRNA ratio in femoral bone. Despite similar increases in bone mass, the deletion of Dkk1 in osterix-expressing cells reduced circulating Dkk1 significantly (males, -79%; females, -77%), whereas they were not changed in Dkk1^fl/fl ;Dmp1-Cre mice. However, both lines showed significantly reduced Dkk1 mRNA levels in bone. In summary, we show that lack of Dkk1 in cells of the osteoblastic lineage leads to high bone mass with increased bone formation, despite increased levels of sclerostin. Moreover, the majority of systemic Dkk1 appears to originate from osteoprogenitors but not from mature osteoblasts or osteocytes. Nevertheless, the amount of Dkk1 produced locally by more mature osteogenic cells is sufficient to modulate bone mass. Thus, this study highlights the importance of local Wnt signaling on postnatal bone homeostasis. © 2018 American Society for Bone and Mineral Research.

Wnt signaling in bone metastasis: mechanisms and therapeutic opportunities

Bone metastasis frequently occurs in advanced cancer patients, who will develop osteogenic/osteolytic bone lesions in the late stage of the disease. Wnt signaling pathway, which is mainly grouped into the β-catenin dependent pathway and β-catenin independent pathway, is a well-organized cascade that has been reported to play important roles in a variety of physiological and pathological conditions, including bone metastasis. Regulation of Wnt signaling in bone metastasis involves multiple stages, including dissemination of primary tumor cells to bone, dormancy and outgrowth of metastatic tumor cells, and tumor-induced osteogenic and osteolytic bone destruction, suggesting the importance of Wnt signaling in bone metastasis pathology. In this review, we will introduce the involvement of Wnt signaling components in specific bone metastasis stages and summarize the promising Wnt modulators that have shown potential as bone metastasis therapeutics, in the hope to maximize the therapeutic opportunities of Wnt signaling for bone metastasis.

DKK1 and Kremen Expression Predicts the Osteoblastic Response to Bone Metastasis

Bone metastasis is a complication of advanced breast and prostate cancer. Tumor-secreted Dickkopf homolog 1 (DKK1), an inhibitor of canonical Wnt signaling and osteoblast differentiation, was proposed to regulate the osteoblastic response to metastatic cancer in bone. The objectives of this study were to compare DKK1 expression with the in vivo osteoblastic response in a panel of breast and prostate cancer cell lines, and to discover mechanisms that regulate cancer DKK1 expression. DKK1 expression was highest in MDA-MB-231 and PC3 cells that produce osteolytic lesions, and hence a suppressed osteoblastic response, in animal models of bone metastasis. LnCaP, C4-2B, LuCaP23.1, T47D, ZR-75-1, MCF-7, ARCaP and ARCaP_M cancer cells that generate osteoblastic, mixed or no bone lesions had the lowest DKK1 expression. The cell lines with negligible expression, LnCaP, C4-2B and T47D, exhibited methylation of the DKK1 promoter. Canonical Wnt signaling activity was then determined and found in all cell lines tested, even in the MDA-MB-231 and PC3 cell lines despite sizeable amounts of DKK1 protein expression expected to block canonical Wnt signaling. A mechanism of DKK1 resistance in the osteolytic cell lines was investigated and determined to be at least partially due to down-regulation of the DKK1 receptors Kremen1 and Kremen2 in the MDA-MB-231 and PC3 cell lines. Combined DKK1 and Kremen expression in cancer cells may serve as predictive markers of the osteoblastic response of breast and prostate cancer bone metastasis.

The power of precise bioinformatics prediction of miRNA:mRNA interactions:miR-4699 as a potential inducer of Wnt signaling pathway

microRNAs have attracted interest because of their regulatory effects on gene expression. Experimental detection of potential targets of miRNAs is a laborious task. Considering the expensive techniques of detection, computational approaches for miRNA target prediction can be used as the first step in miRNA research. A large number of tools and algorithms have been developed during the last two decades, led to problems such as confusion in selecting an appropriate tool and false positive or negative results. Therefore, one of the most frequent problems and critical issues of miRNA research is finding a reliable miRNA target prediction tool. In this study, we have proposed a research direction and introduced user-friendly and current databases and tools with the highest accuracy. To verify whether our proposed research direction is practical, we have provided a case example of predicting a miRNA which can target negative regulators of osteogenesis and experimentally evaluated the accuracy of the prediction results by Real-Time PCR and Luciferase assay. The results of RT-qPCR and Luciferase assay indicated a significant decline in expression of Dickkopf-related protein 1 (DKK1) and tumor necrosis factor ligand superfamily member 11 (TNFSF11) as the key negative regulators of osteogenesis upon overexpression of miR-4699-3p. The results emphasize the validity and importance of accurate in silico investigation as the first step in experimental studies. This is the first report detailing the prediction and validation of miR-4699-3p target genes. We suggest hsa-miR-4699 for further investigation as an osteogenic miRNA for therapeutics purposes.

Effects of DKK1 overexpression on bone metastasis of SBC-3 cells

Among all malignancies, lung cancer is the leading cause of cancer-related deaths in China. Bone metastasis is one of the most common complications and one of the most important factors affecting the prognosis of lung cancer patients, which resulting in very poor therapeutic effects. Previously, we have demonstrated that the expression levels of Dickkopf1 (DKK1), a protein involved in cell regulation and proliferation, was dramatically higher in cells that have a tendency to metastasize and invade the bone tissue (SBC-5 cells) compared with cells that do not (SBC-3 cells). Downregulation of DKK1 in SBC-5 cells inhibited cell malignancy in vitro, and the formation of bone metastasis in vivo. However, whether upregulating DKK1 would be sufficient to induce aggressive tumor behavior (proliferation, migration, invasion and metastasis) in SBC-3 cells remained to be investigated. The present study aimed to examine the role of DKK1 in SBC-3 cells, as well as to investigate the SBC-3 ability to metastasize and invade the bone tissue. The results demonstrated that upregulation of DKK1 in SBC-3 cells enhanced cell proliferation, colony formation, cell migration and invasion in vitro, as well as bone metastasis in vivo. These results indicate that DKK1 may be an important regulator in the development of small cell lung cancer (SCLC), and targeting DKK1 may be an effective method for preventing and/or treating skeletal metastases in SCLC cases.

Sclerostin: an Emerging Target for the Treatment of Cancer-Induced Bone Disease

PURPOSE OF REVIEW

This review provides a summary of the current knowledge on Sost/sclerostin in cancers targeting the bone, discusses novel observations regarding its potential as a therapeutic approach to treat cancer-induced bone loss, and proposes future research needed to fully understand the potential of therapeutic approaches that modulate sclerostin function.

RECENT FINDINGS

Accumulating evidence shows that sclerostin expression is dysregulated in a number of cancers that target the bone. Further, new findings demonstrate that pharmacological inhibition of sclerostin in preclinical models of multiple myeloma results in a robust prevention of bone loss and preservation of bone strength, without apparent effects on tumor growth. These data raise the possibility of targeting sclerostin for the treatment of cancer patients with bone metastasis. Sclerostin is emerging as a valuable target to prevent the bone destruction that accompanies the growth of cancer cells in the bone. Further studies will focus on combining anti-sclerostin therapy with tumor-targeted agents to achieve both beneficial skeletal outcomes and inhibition of tumor progression.

Rationale for targeting the Wnt signalling modulator Dickkopf-1 for oncology

Wnt signalling is a fundamental pathway involved in embryonic development and adult tissue homeostasis. Mutations in the pathway frequently lead to developmental defects and cancer. As such, therapeutic intervention of this pathway has generated tremendous interest. Dickkopf-1 (DKK1) is a secreted inhibitor of β-catenin-dependent Wnt signalling and was originally characterized as a tumour suppressor based on the prevailing view that Wnt signalling promotes cancer pathogenesis. However, DKK1 appears to increase tumour growth and metastasis in preclinical models and its elevated expression correlates with a poor prognosis in a range of cancers, indicating that DKK1 has more complex cellular and biological functions than originally appreciated. Here, we review current evidence for the cancer-promoting activity of DKK1 and recent insights into the effects of DKK1 on signalling pathways in both cancer and immune cells. We discuss the rationale and promise of targeting DKK1 for oncology.

LINKED ARTICLES

This article is part of a themed section on WNT Signalling: Mechanisms and Therapeutic Opportunities. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.24/issuetoc.

Endocrine Therapy of Estrogen Receptor-Positive Breast Cancer Cells: Early Differential Effects on Stem Cell Markers

Introduction

Endocrine therapy of breast cancer, which either deprives cancer tissue of estrogen or prevents estrogen pathway signaling, is the most common treatment after surgery and radiotherapy. We have previously shown for the estrogen-responsive MCF-7 cell line that exposure to tamoxifen, or deprivation of estrogen, leads initially to inhibition of cell proliferation, followed after several months by the emergence of resistant sub-lines that are phenotypically different from the parental line. We examined the early responses of MCF-7 cells following either exposure to 4-hydroxytamoxifen or deprivation of estrogen for periods of 2 days–4 weeks.

Methods

Endocrine-sensitive or -resistant breast cancer cell lines were used to examine the expression of the stem cell gene SOX2, and the Wnt effector genes AXIN2 and DKK1 using quantitative PCR analysis. Breast cancer cell lines were used to assess the anti-proliferative effects (as determined by IC₅₀ values) of Wnt pathway inhibitors LGK974 and IWP-2.

Results

Hormone therapy led to time-dependent increases of up to 10-fold in SOX2 expression, up to threefold in expression of the Wnt target genes AXIN2 and DKK1, and variable changes in NANOG and OCT4 expression. The cells also showed increased mammosphere formation and increased CD24 surface protein expression. Some but not all hormone-resistant MCF-7 sub-lines, emerging after long-term hormonal stress, showed up to 50-fold increases in SOX2 expression and smaller increases in AXIN2 and DKK1 expression. However, the increase in Wnt target gene expression was not accompanied by an increase in sensitivity to Wnt pathway inhibitors LGK974 and IWP-2. A general trend of lower IC₅₀ values was observed in 3-dimensional spheroid culture conditions (which allowed enrichment of cells with cancer stem cell phenotype) relative to monolayer cultures. The endocrine-resistant cell lines showed no significant increase in sensitivity to Wnt inhibitors.

Conclusion

Hormone treatment of cultured MCF-7 cells leads within 2 days to increased expression of components of the SOX2 and Wnt pathways and to increased potential for mammosphere formation. We suggest that these responses are indicative of early adaptation to endocrine stress with features of stem cell character and that this facilitates the survival of emerging hormone-resistant cell populations.

Acute myeloid leukemia transforms the bone marrow niche into a leukemia-permissive microenvironment through exosome secretion

Little is known about how leukemia cells alter the bone marrow (BM) niche to facilitate their own growth and evade chemotherapy. Here, we provide evidence that acute myeloid leukemia (AML) blasts remodel the BM niche into a leukemia growth-permissive and normal hematopoiesis-suppressive microenvironment through exosome secretion. Either engrafted AML cells or AML-derived exosomes increased mesenchymal stromal progenitors and blocked osteolineage development and bone formation in vivo. Preconditioning with AML-derived exosomes ‘primed’ the animals for accelerated AML growth. Conversely, disruption of exosome secretion in AML cells through targeting Rab27a, an important regulator involved in exosome release, significantly delayed leukemia development. In BM stromal cells, AML-derived exosomes induced the expression of DKK1, a suppressor of normal hematopoiesis and osteogenesis, thereby contributing to osteoblast loss. Conversely, treatment with a DKK1 inhibitor delayed AML progression and prolonged survival in AML-engrafted mice. In addition, AML-derived exosomes induced a broad downregulation of hematopoietic stem cell-supporting factors (for example, CXCL12, KITL and IGF1) in BM stromal cells and reduced their ability to support normal hematopoiesis. Altogether, this study uncovers novel features of AML pathogenesis and unveils how AML cells create a self-strengthening leukemic niche that promotes leukemic cell proliferation and survival, while suppressing normal hematopoiesis through exosome secretion.

Serum dickkopf-1 as a clinical and prognostic factor in non-small cell lung cancer patients with bone metastases

Background

The study was designed to evaluate the association between serum dickkopf-1 (DKK1) and non-small cell lung cancer (NSCLC) bone metastases.

Materials and Methods

Serum DKK1 levels were quantified in 470 NSCLC patients, 140 with osseous metastases, 178 with extraosseous metastases, and 152 with early stage in complete remission. The Receiver Operating Characteristic (ROC) curve enabled us to identify a threshold value to distinguish patients with bone metastases.

Results

Serum DKK1 levels in patients with osseous metastases were significantly higher than in the other 2 groups (P < 0.001). ROC curves showed that the optimum cutoff was 311.8 pg/ml (area under curve 0.791, 95% confidence interval 0.739–0.843, sensitivity 77.1% and specificity 71.4%). Of interest, serum DKK1 correlated with the number of bone lesions (P = 0.042) and associated with the poor survival in NSCLC patients with osseous metastases (P = 0.029).

Conclusions

Our data shows that serum DKK1 can be used for the detection of NSCLC bone metastases. More importantly this is the first report to show that serum DKK1 is a good predictor of poor prognosis in NSCLC patients with bone metastases.

Adjuvant tamoxifen but not aromatase inhibitor therapy decreases serum levels of the Wnt inhibitor dickkopf-1 while not affecting sclerostin in breast cancer patients

PURPOSE

Endocrine therapies, including tamoxifen or aromatase inhibitors, are indispensable for the treatment of patients with estrogen receptor (ER)- and/or progesterone-positive breast cancer. Whereas tamoxifen displays partial ER agonistic effects in bone, aromatase inhibitors increase bone resorption and fracture risk. The Wnt inhibitors dickkopf-1 (DKK-1) and sclerostin negatively impact bone formation and are considered targets for the treatment of bone disorders. However, the effect of endocrine therapies on serum DKK-1 and sclerostin levels in patients with primary breast cancer remains elusive.

METHODS

Serum DKK-1 and sclerostin levels were measured at primary diagnosis as well as 3-5 days and 12 months after surgery in a cohort of 45 pre- and postmenopausal women with primary estrogen receptor-positive breast cancer treated with adjuvant tamoxifen or aromatase inhibitors.

RESULTS

Mean baseline levels ±SD for DKK-1 and sclerostin were 29.7 ± 14.6 and 27.1 ± 16.2 pmol/l, respectively. A significant negative correlation of DKK-1 levels and age was observed (r = -0.32; p < 0.05), but not for sclerostin. Of note, DKK-1 levels were significantly lower in peri- and postmenopausal women compared to premenopausal patients (-47%; p < 0.05). In tamoxifen-treated patients, DKK-1 levels were reduced by 35% (p < 0.01) one year after surgery but remained unaltered in patients treated with aromatase inhibitors. No significant changes were observed for sclerostin.

CONCLUSION

DKK-1 serum levels were reduced in breast cancer patients receiving an adjuvant therapy with tamoxifen, possibly contributing to its bone-protective properties.

Alteration of osteoblast arrangement via direct attack by cancer cells: New insights into bone metastasis

Intact bone tissue exhibits a characteristic anisotropic microstructure derived from collagen fiber alignment and the related c-axis orientation of apatite crystals, which govern the mechanical properties of bone tissue. In contrast, tumor-invaded bone exhibits a disorganized, less-aligned microstructure that results in severely disrupted mechanical function. Despite its importance both in basic principle and in therapeutic applications, the classical understanding of bone metastasis is limited to alterations in bone mass regulated by metastatic cancer cells. In this study, we demonstrate a novel mechanism underlying the disruption of bone tissue anisotropy in metastasized bone. We observed that direct attack by cancer cells on osteoblasts induces the less-organized osteoblast arrangement. Importantly, the crystallographic anisotropy of bone tissue is quantitatively determined by the level of osteoblast arrangement. Osteoblast arrangement was significantly disrupted by physical contact with cancer cells such as osteolytic melanoma B16F10, breast cancer MDA-MB-231, and osteoblastic prostate cancer MDA-PCa-2b cells. The present findings demonstrate that the abnormal arrangement of osteoblasts induced by physical contact with cancer cells facilitates the disorganized microstructure of metastasized bone.

The Biological Effects of Dickkopf1 on Small Cell Lung Cancer Cells and Bone Metastasis

The bone is among the most common sites of metastasis in patients with lung cancer. Over 30%–40% of lung cancers can develop bone metastasis, and no effective therapeutic methods exist in clinic cases. Wnt/β-catenin signaling and Dickkopf1 (DKK1) play important roles in the progression of lung cancer, which preferentially metastasizes to the skeleton. However, the role of DKK1 in osteotropism of small cell lung cancer (SCLC) remains to be elucidated. This study aimed to define the role of DKK1 in SCLC bone metastasis and investigate the underlying mechanisms. Our results demonstrated that the expression level of DKK1 was dramatically higher in bone metastatic SCLC cells (SBC-5 cell line) compared with that in cells without bone metastatic ability (SBC-3 cell line). Therefore, we hypothesized that DKK1 was involved in the bone metastasis of SCLC. We then suppressed the DKK1 expression in SBC-5 cells by RNAi and found that downregulation of DKK1 can inhibit cell proliferation, colony formation, cell migration, and invasion, but increase the apoptosis rate. Downregulation of DKK1 did not affect the cell cycle progression of SBC-5 cells in vitro. In vivo, downregulated DKK1 in SBC-5 cells resulted in attenuated bone metastasis. These results indicated that DKK1 may be an important regulator in bone metastases of SCLC, and targeting DKK1 may be an effective method to prevent and treat skeleton metastases in SCLC cases.

Breast cancer cells and bone marrow mesenchymal stromal cells: a regulated modulation of the breast tumor in the context of immune response

OBJECTIVE

The role of direct cell-cell interactions mediating selective bone metastasis by breast cancer cells (BCCs) niche is still mostly unknown.

MATERIALS AND METHODS

Conditioned medium and direct cell-cell contacts experiments were used to investigate the effect of bone marrow-derived mesenchymal stromal cells (MSCs), osteoprogenitor-like cells (MG-63) and osteosarcoma cells (SaOS-2) on luminal-like (MCF-7) and basal-like (MDA-MB-231) BCCs flow cytometry was used to assess the purity of isolated BCCs and osteoblasts. Expression of osteoblastic markers was investigated by semi-quantitative RT-PCR. RANKL and OPG levels were measured by ELISA.

RESULTS

Conditioned medium from MSCs and osteoblasts induced the expression of osteoblastic markers in BCCs. While co-culture assays with SaOS-2 increased the expression of osteoblastic markers in MCF-7 cells, SaOS-2 cell conditioned medium increased the expression of RANKL, PTHrP, VEGF and NOGGIN in MCF-7 cells. Co-cultures with either MG-63 cells or MSCs induced OPG and MMP-2 in both tumor cell lines. Interestingly, conditioned medium from co-cultures of MSCs and MDA-MB-231 cells significantly decreased the proliferation of activated T lymphocytes which was reversed by addition of anti-OPG antibodies to the co-cultures.

CONCLUSION

Our data suggest that MSCs strongly contribute to the adaptation and invasiveness of breast cancer cells in skeletal tissues.

Serum sclerostin levels in renal cell carcinoma patients with bone metastases

Sclerostin has been proposed as a potent inhibitor of bone formation. Sclerostin antibodies are under clinical development to treat osteoporosis and metastatic bone disease. Serum sclerostin level is elevated in multiple myeloma, an osteolytic malignancy, where it might serve as predictive marker for the use of sclerostin-directed antibodies. As renal cell carcinoma (RCC) patients often present with osteolytic metastases, we aimed to investigate serum sclerostin levels in RCC patients. Our study included 53 RCC patients (19 with bone metastases, 25 with visceral metastases and 9 with localized disease) and 53 age- and gender-matched non-osteoporotic controls. Frozen serum samples were subjected to sclerostin quantitative sandwich ELISA. The mean serum sclerostin levels of RCC patients and controls were 45.8 pmol/l and 45.1 pmol/l, respectively (p = 0.86). Analysis of variance showed no difference between the subgroups of RCC patients with regard to visceral or bone metastases or localized disease (p = 0.22). There was no significant association between eGFR (estimated glomerular filtration rate) and serum sclerostin levels in RCC patients (r = 0.05; p = 0.74) and controls (r = 0.06; p = 0.68). Our results indicate that serum sclerostin levels appear not to be a valuable biomarker to assess the occurrence of bone metastases in RCC patients.

Mammary Development and Breast Cancer: A Wnt Perspective

The Wnt pathway has emerged as a key signaling cascade participating in mammary organogenesis and breast oncogenesis. In this review, we will summarize the current knowledge of how the pathway regulates stem cells and normal development of the mammary gland, and discuss how its various components contribute to breast carcinoma pathology.

p38 MAPK regulates the Wnt inhibitor Dickkopf-1 in osteotropic prostate cancer cells

The Wnt inhibitor Dickkopf-1 (DKK-1) has been associated with the occurrence of bone metastases in osteotropic prostate cancer by inhibiting osteoblastogenesis. P38 mitogen-activated protein kinase (MAPK) activity is also dysregulated in advanced prostate cancer. However, the impact of p38 MAPK signaling on DKK-1 remains unknown. Inhibition of p38 MAPK signaling in osteolytic PC3 cells by small molecule inhibitors (doramapimod, LY2228820 and SB202190) suppressed DKK-1 expression, whereas activation of p38 MAPK by anisomycin increased DKK-1. Further dissection by targeting individual p38 MAPK isoforms with siRNA revealed a stronger role for MAPK11 than MAPK14 and MAPK12 in the regulation of DKK-1. Moreover, prostate cancer cells with a predominantly osteolytic phenotype produced sufficient amounts of DKK-1 to inhibit Wnt3a-induced osteoblastic differentiation in C2C12 cells. This inhibition was blocked directly by neutralizing DKK-1 using a specific antibody and also indirectly by blocking p38 MAPK. Furthermore, tissue expression in human prostate cancer revealed a correlation between p38 MAPK and DKK-1 expression with higher expression in tumor compared with normal tissues. These results reveal that p38 MAPK regulates DKK-1 in prostate cancer and may present a potential target in osteolytic prostate cancers.

The best of both worlds - managing the cancer, saving the bone

In the context of breast cancer, the importance of the skeleton in the regulation of primary tumour development and as a site for subsequent metastasis is well characterized. Our understanding of the contributions made by the host bone and bone marrow cells increasingly demonstrates the extent of the interaction between tumour cells and normal host cells. As a result, the need to develop and utilize therapies that can impede the growth and/or function of tumour cells while sparing normal host bone and bone marrow cells is immense and expanding. The need for these new treatments is, however, superimposed on the orthopaedic management of patients' quality of life, where pain control and continued locomotion are paramount. Indeed, the majority of the anticancer therapies used to date often result in direct or indirect damage to bone. Thus, although the bone microenvironment regulates tumour cell growth in bone, cells within the bone marrow niche also mediate many of the orthopaedic consequences of tumour progression as well as resistance to the antitumour effects of existing therapies. In this Review, we highlight the effects of existing cancer treatments on bone and the bone marrow microenvironment as well as the mechanisms mediating these effects and the current utility of modern orthopaedic interventions.

Wnt3a: functions and implications in cancer

Wnt3a, one of Wnt family members, plays key roles in regulating pleiotropic cellular functions, including self-renewal, proliferation, differentiation, and motility. Accumulating evidence has suggested that Wnt3a promotes or suppresses tumor progression via the canonical Wnt signaling pathway depending on cancer type. In addition, the roles of Wnt3a signaling can be inhibited by multiple proteins or chemicals. Herein, we summarize the latest findings on Wnt3a as an important therapeutic target in cancer.

Emerging drugs for the treatment of bone metastasis

INTRODUCTION

Bone metastases are virtually incurable resulting in significant disease morbidity, reduced quality of life and mortality. Bone provides a unique microenvironment whose local interactions with tumor cells offer novel targets for therapeutic interventions. Increased understanding of the pathogenesis of bone disease has led to the discovery and clinical utility of bone-targeted agents other than bisphosphonates and denosumab, currently, the standard of care in this setting.

AREAS COVERED

In this review, we present the recent advances in molecular targeted therapies focusing on therapies that inhibit bone resorption and/or stimulate bone formation and novel anti-tumoral agents that exerts significant effects on skeletal metastases, nowadays available in clinical practice or in phase of development.

EXPERT OPINION

New emergent bone target therapies radium-223, mTOR inhibitors, anti-androgens have demonstrated the ability to increase overall survival in bone metastatic patients, other compounds, such as ET-1 and SRC inhibitors, up to now failed to clearly confirm in clinical trials their promising preclinical data.

Interaction between bone marrow stromal cells and neuroblastoma cells leads to a VEGFA-mediated osteoblastogenesis

The potential role of osteoblasts in bone and bone marrow (BM) metastases in neuroblastoma (NBL) remains unclear. In this study, we examined the effect of NBL cells on the osteoblastic differentiation of BM-derived mesenchymal stromal cells (BMMSC). We show that the presence of NBL cells enhanced the osteoblastic differentiation of BMMSC driven by bone morphogenetic protein (BMP)-4, in the absence of any effect on NBL cell proliferation. Expression profiles of BMMSC driven toward osteoblastic differentiation revealed an increase in vascular endothelial growth factor A (Vegfa) expression in the presence of NBL cells. We demonstrated that NBL cells increased BMMSC-derived VEGFA mRNA and protein and that this was enhanced by BMP-4. However, in similar conditions, neither the addition of an mVEGFA blocking antibody nor exogenous recombinant (r) mVEGFA affected osteoblastic differentiation. In contrast, siRNA- mediated knock-down of VEGFA in BMMSC prevented osteoblastic differentiation in BMP-4-treated cocultures, an effect that was not reversed in the presence of rmVEGFA. An analysis of murine bones injected with hNBL cells revealed an increase of mVEGFA producing cells near tumor cells concomitantly with an increase in Vegfa and Runx2 mRNA. This coincided with an increase in osteoclasts, in Rankl/Opg mRNA ratio and with the formation of osteolytic lesions. Thus NBL cells promote osteoblastogenesis in the BM by increasing VEGFA expression in BMMSC. Our study provides a new insight into the role of VEGFA in NBL metastases by pointing to the role of stroma-derived intracrine VEGFA in osteoblastogenesis.

Galectin-3 inhibits osteoblast differentiation through notch signaling

Patients with bone cancer metastasis suffer from unbearable pain and bone fractures due to bone remodeling. This is caused by tumor cells that disturb the bone microenvironment. Here, we have investigated the role of tumor-secreted sugar-binding protein, i.e., galectin-3, on osteoblast differentiation and report that it downregulates the expression of osteoblast differentiation markers, e.g., RUNX2, SP7, ALPL, COL1A1, IBSP, and BGLAP, of treated human fetal osteoblast (hFOB) cells. Co-culturing of hFOB cells with human breast cancer BT-549 and prostate cancer LNCaP cells harboring galectin-3 has resulted in inhibition of osteoblast differentiation by the secreted galectin-3 into culture medium. The inhibitory effect of galectin-3 was found to be through its binding to Notch1 in a sugar-dependent manner that has led to accelerated Notch1 cleavage and activation of Notch signaling. Taken together, our findings show that soluble galectin-3 in the bone microenvironment niche regulates bone remodeling through Notch signaling, suggesting a novel bone metastasis therapeutic target.

Runx2, a target gene for activating transcription factor-3 in human breast cancer cells

Activating transcription factor (ATF-3) is a stress response gene and is induced by transforming growth factor beta 1 (TGF-β1) in breast cancer cells. In this study, we dissected the functional role of ATF-3 gene in vitro by knocking down its expression stably in human bone metastatic breast cancer cells (MDA-MB231). Knockdown of ATF-3 expression in these cells decreased cell number, altered cell cycle phase transition, and decreased mRNA expression of cell cycle genes. Knockdown of ATF-3 expression in MDA-MB231 cells also decreased cell migration, and the expression levels of invasive and metastatic genes such as MMP-13 and Runx2 were found to be decreased in these cells. Most importantly, ATF-3 was associated with Runx2 promoter in MDA-MB231 cells and knockdown of ATF-3 expression decreased its association with Runx2 promoter. Hence, our results suggested that ATF-3 plays a role in proliferation and invasion of bone metastatic breast cancer cells in vitro and we identified for the first time that Runx2 is a target gene of ATF-3 in MDA-MB231 cell line.

RANKL inhibition blocks osteolytic lesions and reduces skeletal tumor burden in models of non-small-cell lung cancer bone metastases

INTRODUCTION

Bone metastasis is a serious complication in patients with lung cancer, occurring in up to 40% of patients. Tumor cell-mediated osteolysis occurs ultimately through induction of RANK ligand (RANKL) within the bone stroma although this hypothesis has not been tested extensively in the setting of non-small-cell lung cancer (NSCLC). By using two novel NSCLC bone metastasis mouse models, we examined the effects of RANKL inhibition on osteolysis and tumor progression.

METHODS

We treated mice bearing skeletal NSCLC tumors with osteoprotegerin-Fc (OPG-Fc) to assess whether osteoclast inhibition through RANKL inhibition would affect bone metastases at early or late stages of bone colonization. Progression of skeletal tumor was determined by radiography, longitudinal bioluminescent imaging, and histological analyses.

RESULTS

OPG-Fc reduced development and progression of radiographically evident osteolytic lesions and also significantly reduced skeletal tumor progression in both NSCLC bone metastasis models. In the H1299 human NSCLC bone metastasis model, OPG-Fc plus docetaxel in combination resulted in significantly greater inhibition of skeletal tumor growth compared with either single agent alone. The observed ability of RANKL inhibition to reduce NSCLC osteolytic bone destruction or skeletal tumor burden was associated with decreases in tumor-associated osteoclasts.

CONCLUSIONS

These results demonstrate that RANKL is required for the development of tumor-induced osteolytic bone destruction caused by NSCLC cells in vivo. RANKL inhibition also reduced skeletal tumor burden, presumably through the indirect mechanism of blocking tumor-induced osteoclastogenesis and resultant production of growth factors and calcium from the bone microenvironment. RANKL inhibition also provided an additive benefit to docetaxel treatment by augmenting the reduction of tumor burden.

BMP9 regulates cross-talk between breast cancer cells and bone marrow-derived mesenchymal stem cells

PURPOSE

Breast cancer cells frequently metastasize to distant organs, including bone. Interactions between breast cancer cells and the bone microenvironment are known to enhance tumor growth and osteolytic damage. Here we investigated whether BMP9 (a secretary protein) may change the bone microenvironment and, by doing so, regulate the cross-talk between breast cancer cells and bone marrow-derived mesenchymal stem cells.

METHODS

After establishing a co-culture system composed of MDA-MB-231 breast cancer cells and HS-5 bone marrow-derived mesenchymal stem cells, and exposure of this system to BMP9 conditioned media, we assessed putative changes in migration and invasion capacities of MDA-MB-231 cells and concomitant changes in osteogenic marker expression in HS-5 cells and metastases-related genes in MDA-MB-231 cells.

RESULTS

We found that BMP9 can inhibit the migration and invasion of MDA-MB-231 cells, and promote osteogenesis and proliferation of HS-5 cells, in the co-culture system. We also found that the BMP9-induced inhibition of migration and invasion of MDA-MB-231 cells may be caused by a decreased RANK ligand (RANKL) secretion by HS-5 cells, leading to a block in the AKT signaling pathway.

CONCLUSIONS

From our data we conclude that BMP9 inhibits the migration and invasion of breast cancer cells, and promotes the osteoblastic differentiation and proliferation of bone marrow-derived mesenchymal stem cells by regulating cross-talk between these two types of cells through the RANK/RANKL signaling axis.