Breast cancer metastasis to the bone: mechanisms of bone loss

A nanobody against the V-ATPase c subunit inhibits metastasis of 4T1-12B breast tumor cells to lung in mice

The vacuolar H+-ATPase (V-ATPase) is an ATP-dependent proton pump that functions to control the pH of intracellular compartments as well as to transport protons across the plasma membrane of various cell types, including cancer cells. We have previously shown that selective inhibition of plasma membrane V-ATPases in breast tumor cells inhibits the invasion of these cells in vitro. We have now developed a nanobody directed against an extracellular epitope of the mouse V-ATPase c subunit. We show that treatment of 4T1-12B mouse breast cancer cells with this nanobody inhibits V-ATPase-dependent acidification of the media and invasion of these cells in vitro. We further find that injection of this nanobody into mice implanted with 4T1-12B cells orthotopically in the mammary fat pad inhibits metastasis of tumor cells to lung. These results suggest that plasma membrane V-ATPases represent a novel therapeutic target to limit breast cancer metastasis.

Alendronate-functionalized porous nano-crystalsomes mitigate osteolysis and consequent inhibition of tumor growth in a tibia-induced metastasis model

Bone is one of the most prevalent sites of metastases in various epithelial malignancies, including breast cancer and this metastasis to bone often leads to severe skeletal complications in women due to its osteolytic nature. To address this, we devised a novel drug delivery approach using an Alendronate (ALN) functionalized self-assembled porous crystalsomes for concurrent targeting of Oleanolic acid (OA) and ALN (ALN + OA@NCs) to bone metastasis. Initially, the conjugation of both PEG-OA and OA-PEG-ALN with ALN and OA was achieved, and this conjugation was then self-assembled into porous crystalsomes (ALN + OA@NCs) by nanoemulsion crystallization. The reconstruction of a 3D single particle using transmission electron microscopy ensured the crystalline porous structure of ALN + OA@NCs, was well aligned with characteristic nanoparticle attributes including size distribution, polydispersity, and zeta potential. Further, ALN + OA@NCs showed enhanced efficacy in comparison to OA@NCs suggesting the cytotoxic roles of ALN towards cancer cells, followed by augmentation ROS generation (40.81%), mitochondrial membrane depolarization (57.20%), and induction of apoptosis (40.43%). We found that ALN + OA@NCs facilitated inhibiting osteoclastogenesis and bone resorption followed by inhibited osteolysis. In vivo activity of ALN + OA@NCs in the 4 T1 cell-induced tibia model rendered a reduced bone loss in the treated mice followed by restoring bone morphometric markers which were further corroborated bone-targeting effects of ALN + OA@NCs to reduce RANKL-stimulated osteoclastogenesis. Further, In vivo intravenous pharmacokinetics showed the improved therapeutic profile of the ALN + OA@NCs in comparison to the free drug, prolonging the levels of the drug in the systemic compartment by reducing the clearance culminating the higher accumulation at the tumor site. Our finding proposed that ALN + OA@NCs can effectively target and treat breast cancer metastasis to bone and its associated complications.

Radiomics based on multiple machine learning methods for diagnosing early bone metastases not visible on CT images

OBJECTIVES

This study utilizes [99mTc]-methylene diphosphate (MDP) single photon emission computed tomography (SPECT) images as a reference standard to evaluate whether the integration of radiomics features from computed tomography (CT) and machine learning algorithms can identify microscopic early bone metastases. Additionally, we also determine the optimal machine learning approach.

MATERIALS AND METHODS

We retrospectively studied 63 patients with early bone metastasis from July 2020 to March 2023. The ITK-SNAP software was used to delineate early bone metastases and normal bone tissue in SPECT images of each patient, which were then registered onto CT images to outline the volume of interest (VOI). The VOI includes 63 early bone metastasis volumes and 63 normal bone tissue volumes. 126 VOIs were randomly distributed in a 7:3 ratio between the training and testing groups, and 944 radiomics features were extracted from every VOI. We established 20 machine learning models using 5 feature selection algorithms and 4 classification methods. Evaluate the performance of the model using the area under the receiver operating characteristic curve (AUC).

RESULTS

Most machine learning models demonstrated outstanding discriminative capacity, with AUCs higher than 0.70. Notably, the K-Nearest Neighbors (KNN) classifier exhibited significant performance improvement compared to the other four classifiers. Specifically, the model constructed utilizing eXtreme Gradient Boosting (XGBoost) feature selection method integrated with KNN classifier achieved the maximum AUC, which is 0.989 in the training set and 0.975 in the testing set.

CONCLUSIONS

Radiomics features integrated with machine learning methods can identify early bone metastases that are not visible on CT images. In our analysis, KNN is considered the optimal classification method.

Breast cancer cells promote osteoclast differentiation in an MRTF-dependent paracrine manner

Bone is a frequent site for breast cancer metastasis. Conditioning of the local tumor microenvironment (TME) through crosstalk between tumor cells and bone resident cells in the metastatic niche is a major driving force for bone colonization of breast cancer cells. The vast majority of breast cancer-associated metastasis is osteolytic in nature, and RANKL-induced differentiation of bone marrow-derived macrophages to osteoclasts (OCLs) is a key requirement for osteolytic metastatic growth of cancer cells. In this study, we demonstrate that breast cancer cell-secreted factors stimulate RANKL-induced OCL differentiation of BMDMs requiring the function of Myocardin-related transcription factor (MRTF) in tumor cells. This is partly attributed to the critical role of MRTF in maintaining the basal cellular expression of connective tissue growth factor (CTGF), a pro-osteoclastogenic matricellular factor known to promote bone metastasis in human breast cancer. Supporting these in vitro findings, bioinformatics analyses of multiple human breast cancer transcriptome datasets reveal a strong positive correlation between CTGF expression and MRTF gene signature further establishing the relevance of our findings in a human disease context. By Luminex analyses, we show that MRTF depletion in breast cancer cells has a broad impact on OCL-regulatory cell-secreted factors that extends beyond CTGF. These findings, taken together with demonstration of MRTF-dependence for bone colonization breast cancer cells in vivo, suggest that MRTF inhibition could be an effective strategy to diminish OCL formation and skeletal involvement in breast cancer. In summary, this study highlights a novel tumor-extrinsic function of MRTF relevant to breast cancer metastasis.

Selenoprotein W engages in overactive osteoclast differentiation in multiple myeloma

BACKGROUND

Patients with multiple myeloma exhibit malignant osteolytic bone disease due to excessive osteoclast formation and function. We recently identified that osteoclastogenic stimulator selenoprotein W (SELENOW) is upregulated via ERK signaling and downregulated via p38 signaling during receptor activator of nuclear factor (NF)-κΒ ligand (RANKL)-induced osteoclast differentiation. In the intrinsic physiological process, RANKL-induced downregulation of SELENOW maintains proper osteoclast differentiation; in contrast, forced overexpression of SELENOW leads to overactive osteoclast formation and function.

METHODS AND RESULTS

We observed that SELENOW is highly expressed in multiple myeloma-derived peripheral blood mononuclear cells (PBMCs) and mature osteoclasts when compared to healthy controls. Also, the level of tumor necrosis factor alpha (TNFα), a pathological osteoclastogenic factor, is increased in the PBMCs and serum of patients with multiple myeloma. ERK activation by TNFα was more marked and sustained than that by RANKL, allowing SELENOW upregulation. Excessive expression of SELENOW in osteoclast progenitors and mature osteoclasts derived from multiple myeloma facilitated efficient nuclear translocation of osteoclastogenic transcription factors NF-κB and NFATc1, which are favorable for osteoclast formation.

CONCLUSION

Our findings suggest a possibility that feedforward signaling of osteoclastogenic SELENOW by TNFα derived from multiple myeloma induces overactive osteoclast differentiation, leading to bone loss during multiple myeloma.

Recent Advances in Minimally Invasive Management of Osteolytic Periacetabular Skeletal Metastases

Painful skeletal osteolytic metastases, impending pathological fractures, and nondisplaced fractures present as a devastating clinical problem in advanced stage cancer patients. Open surgical approaches provide excellent mechanical stabilization but are often associated with high complication rates and slow recovery times. Percutaneous minimally invasive interventions have arisen as a pragmatic and logical treatment option for patients with late-stage cancer in whom open surgery may be contraindicated. These percutaneous interventions minimize soft tissue dissection, allow for the immediate initiation or resumption of chemotherapies, and present with fewer complications. This review provides the most up-to-date technical and conceptual framework for the minimally invasive management of osseous metastases with particular focus on periacetabular lesions. Fundamental topics discussed are as follows: (1) pathogenesis of cancer-induced bone loss and the importance of local cytoreduction to restore bone quality, (2) anatomy and biomechanics of the acetabulum as a weight-bearing zone, (3) overview of ablation options and cement/screw techniques, and (4) combinatorial approaches. Future studies should include additional studies with more long-term follow-up to better assess mechanical durability of minimally invasive interventions. An acetabulum-specific functional and pain scoring framework should be adopted to allow for better cross-study comparison.

Altered gut microbiome drives heightened pain sensitivity in a murine model of metastatic triple-negative breast cancer

The microbiota residing in the gut environment is essential for host homeostasis. Increasing evidence suggests that microbial perturbation (dysbiosis) regulates cancer initiation and progression at local and distant sites. Here, we have identified microbial dysbiosis with the depletion of commensal bacteria as a host-intrinsic factor associated with metastatic dissemination to the bone. Using a mouse model of triple-negative mammary cancer, we demonstrate that a pre-established disruption of microbial homeostasis using an antibiotic cocktail increases tumor growth, enhanced circulating tumor cells, and subsequent dissemination to the bone. We found that the presence of pathogenic bacteria and loss of commensal bacteria in an antibiotic-induced gut environment is associated with sustained inflammation. Increased secretion of G-CSF and MMP-9 in intestinal tissues, followed by increased neutrophil infiltration and severe systemic inflammation in tumor-bearing mice, indicates the direct consequence of a dysbiotic microbiome. Increased neutrophil infiltration to the bone metastatic niche facilitates extravasation and transendothelial migration of tumor cells. It provides a novel, pre-established, and favorable environment to form an immunosuppressive pre-metastatic niche. The presence of tumor cells in immunosuppressive metastatic tumor niche disrupts the balance between osteoblasts and osteoclasts, promotes osteoclast differentiation, and remodels the bone structure. Excessive bone resorption by osteoclasts causes bone degradation and ultimately causes extreme pain in a bone metastatic mouse model. In clinical settings, bone metastasis is associated with intractable severe pain that severely compromises the quality of life in these patients.

Effect of phosphodiester composition in polyphosphoesters on the inhibition of osteoclastic differentiation of murine bone marrow mononuclear cells

Osteoporosis is a common bone disorder characterized by reduced bone density and increased risk of fractures. The modulation of bone cell functions, particularly the inhibition of osteoclastic differentiation, plays a crucial role in osteoporosis treatment. Polyphosphoesters (PPEs) have shown the potential in reducing the function of osteoclast cells, but the effect of their chemical structure on osteoclastic differentiation remains largely unexplored. In this study, we evaluated the effect of PPE's chemical structure on the inhibition of osteoclastic differentiation of murine bone marrow mononuclear cells (BMNCs). PPEs containing phosphotriester and phosphodiester units at varying compositions were synthesized. Cytotoxicity testing confirmed the biocompatibility of the copolymers at concentrations below 0.5 mg/mL. Isolated from long bones, BMNCs were cultured in a differentiation medium supplemented with different PPE concentrations. Osteoclast formation was assessed through tartrate-resistant acid phosphatase and phalloidin staining. A significant decrease in the size of osteoclast cells formed upon BMNC contact with PPEs was observed, with a more pronounced effect observed at higher PPE concentrations. In addition, an increased composition of phosphodiester units in the PPEs yielded a decreased density of differentiated osteoclasts. Furthermore, real-time PCR analysis of major osteoclastic markers provided gene expression data that correlated with microscopic observations, confirming the effect of phosphodiester units in suppressing osteoclast differentiation of BMNCs from the early stages. These findings highlight the potential of PPEs as polymers are capable of modulating bone cell functions through their chemical structures.

Regucalcin Is a Potential Regulator in Human Cancer: Aiming to Expand into Cancer Therapy

Regucalcin, a calcium-binding protein lacking the EF-hand motif, was initially discovered in 1978. Its name is indicative of its function in calcium signaling regulation. The rgn gene encodes for regucalcin and is situated on the X chromosome in both humans and vertebrates. Regucalcin regulates pivotal enzymes involved in signal transduction and has an inhibitory function, which includes protein kinases, protein phosphatases, cysteinyl protease, nitric oxide dynthetase, aminoacyl-transfer ribonucleic acid (tRNA) synthetase, and protein synthesis. This cytoplasmic protein is transported to the nucleus where it regulates deoxyribonucleic acid and RNA synthesis as well as gene expression. Overexpression of regucalcin inhibits proliferation in both normal and cancer cells in vitro, independent of apoptosis. During liver regeneration in vivo, endogenous regucalcin suppresses cell growth when overexpressed. Regucalcin mRNA and protein expressions are significantly downregulated in tumor tissues of patients with various types of cancers. Patients exhibiting upregulated regucalcin in tumor tissue have shown prolonged survival. The decrease of regucalcin expression is linked to the advancement of cancer. Overexpression of regucalcin carries the potential for preventing and treating carcinogenesis. Additionally, extracellular regucalcin has displayed control over various types of human cancer cells. Regucalcin may hold a prominent role as a regulatory factor in cancer development. Supplying the regucalcin gene could prove to be a valuable asset in cancer treatment. The therapeutic value of regucalcin suggests its potential significance in treating cancer patients. This review delves into the most recent research on the regulatory role of regucalcin in human cancer development, providing a novel approach for treatment.

Predicting diagnosis and survival of bone metastasis in breast cancer using machine learning

This study aimed at establishing more accurate predictive models based on novel machine learning algorithms, with the overarching goal of providing clinicians with effective decision-making assistance. We retrospectively analyzed the breast cancer patients recorded in the Surveillance, Epidemiology, and End Results (SEER) database from 2010 to 2016. Multivariable logistic regression analyses were used to identify risk factors for bone metastases in breast cancer, whereas Cox proportional hazards regression analyses were used to identify prognostic factors for breast cancer with bone metastasis (BCBM). Based on the identified risk and prognostic factors, we developed diagnostic and prognostic models that incorporate six machine learning classifiers. We then used the area under the receiver operating characteristic (ROC) curve (AUC), learning curve, precision curve, calibration plot, and decision curve analysis to evaluate performance of the machine learning models. Univariable and multivariable logistic regression analyses showed that bone metastases were significantly associated with age, race, sex, grade, T stage, N stage, surgery, radiotherapy, chemotherapy, tumor size, brain metastasis, liver metastasis, lung metastasis, breast subtype, and PR. Univariate and multivariate Cox regression analyses revealed that age, race, marital status, grade, surgery, radiotherapy, chemotherapy, brain metastasis, liver metastasis, lung metastasis, breast subtype, ER, and PR were closely associated with the prognosis of BCBM. Among the six machine learning models, the XGBoost algorithm predicted the most accurate results (Diagnostic model AUC = 0.98; Prognostic model AUC = 0.88). According to the Shapley additive explanations (SHAP), the most critical feature of the diagnostic model was surgery, followed by N stage. Interestingly, surgery was also the most critical feature of prognostic model, followed by liver metastasis. Based on the XGBoost algorithm, we could effectively predict the diagnosis and survival of bone metastasis in breast cancer and provide targeted references for the treatment of BCBM patients.

Breast Cancer and Bone Mineral Density in a U.S. Cohort of Middle-Aged Women: Associations with Phosphate Toxicity

Breast cancer is associated with phosphate toxicity, the toxic effect from dysregulated phosphate metabolism that can stimulate tumorigenesis. Phosphate toxicity and dysregulated phosphate metabolism are also associated with bone mineral abnormalities, including excessive bone mineral loss and deposition. Based on shared associations with dysregulated phosphate metabolism and phosphate toxicity, a hypothesis proposed in the present mixed methods-grounded theory study posits that middle-aged women with incidence of breast cancer had a greater magnitude of changes in bone mineral density over time compared with women who remained cancer-free. To test this hypothesis, a mixed-effects model was used to analyze the associations of breast cancer incidence with spinal bone mineral density changes in the U.S. Study of Women's Health Across the Nation. Compared with women in the cohort who remained cancer-free, women who self-reported breast cancer had higher bone mineral density at baseline, but had more rapid losses in bone mineral density during follow-up visits. These findings agree with the hypothesis that a greater magnitude of changes in bone mineral density over time is associated with breast cancer in a cohort of middle-aged women. The findings also have implications for studies investigating dysregulated phosphate metabolism and phosphate toxicity as causative factors of bone metastasis in metastatic breast cancer. Additionally, the authors previously found increased breast cancer risk associated with high dietary phosphate intake in the same cohort of middle-aged women, and more studies should investigate a low-phosphorus diet to reduce bone mineral abnormalities and tumorigenesis in breast cancer patients.

Conditional knockout of PDK1 in osteoclasts suppressed osteoclastogenesis and ameliorated prostate cancer-induced osteolysis in murine model

BACKGROUND

The development and maintenance of normal bone tissue is maintained by balanced communication between osteoblasts and osteoclasts. The invasion of cancer cells disrupts this balance, leading to osteolysis. As the only bone resorbing cells in vivo, osteoclasts play important roles in cancer-induced osteolysis. However, the role of 3-phosphoinositide-dependent protein kinase-1 (PDK1) in osteoclast resorption remains unclear.

METHODS

In our study, we used a receptor activator of nuclear factor-kappa B (RANK) promoter-driven Cre-LoxP system to conditionally delete the PDK1 gene in osteoclasts in mice. We observed the effect of osteoclast-specific knockout of PDK1 on prostate cancer-induced osteolysis. Bone marrow-derived macrophage cells (BMMs) were extracted and induced to differentiate osteoclasts in vitro to explore the role of PDK1 in osteoclasts.

RESULTS

In this study, we found that PDK1 conditional knockout (cKO) mice exhibited smaller body sizes when compared to the wild-type (WT) mice. Moreover, deletion of PDK1 in osteoclasts ameliorated osteolysis and rPDK1educed bone resorption markers in the murine model of prostate cancer-induced osteolysis. In vivo, we discovered that osteoclast-specific knockout of suppressed RANKL-induced osteoclastogenesis, bone resorption function, and osteoclast-specific gene expression (Ctsk, TRAP, MMP-9, NFATc1). Western blot analyses of RANKL-induced signaling pathways showed that conditional knockout of PDK1 in osteoclasts inhibited the early nuclear factor κB (NF-κB) activation, which consequently suppressed the downstream induction of NFATc1.

CONCLUSION

These findings demonstrated that PDK1 performs an important role in osteoclastogenesis and prostate cancer-induced osteolysis by modulating the PDK1/AKT/NF-κB signaling pathway.

Osteoclast-derived apoptotic bodies inhibit naive CD8+ T cell activation via Siglec15, promoting breast cancer secondary metastasis

The bone microenvironment promotes cancer cell proliferation and dissemination. During periodic bone remodeling, osteoclasts undergo apoptosis, producing large numbers of apoptotic bodies (ABs). However, the biological role of osteoclast-derived ABs, which are residents of the bone-tumor niche, remains largely unknown. Here, we discover that AB-null MRL/lpr mice show resistance to breast cancer cell implantation, with more CD8+ T cell infiltrations and a higher survival rate. We uncover that the membranous Siglec15 on osteoclast-derived ABs binds with sialylated Toll-like receptor 2 (TLR2) and blocks downstream co-stimulatory signaling, leading to the inhibition of naive CD8+ T cell activation. In addition, our study shows that treatment with Siglec15 neutralizing antibodies significantly reduces the incidence of secondary metastases and improves the survival rate of mice with advanced breast cancer bone metastasis. Our findings reveal the immunosuppressive function of osteoclast-derived ABs in the bone-tumor niche and demonstrate the potential of Siglec15 as a common target for anti-resorption and immunotherapy.

Macromorphometric Analysis of Metastatic Lesions in Bones due to Breast Cancer: Contribution to Human Identification

OBJECTIVE

This study aimed to report the metastatic lesions observed in identified skeletons whose deaths were caused by breast cancer complications to provide information and evidence that can be used in cases of human identification forensics.

METHODS

The research was conducted at the Centre for Forensic Anthropology Studies of the Faculty of Odontology of the University of Pernambuco (CEAF/FOP/UPE), Recife, Brazil. The data bank of the CEAF/FOP/UPE was searched for skeletons with the cause of death reported as due to breast cancer, resulting in five cases. The skeletons were arranged in anatomical positions and macroscopically inspected to register, describe and measure the lesions present to establish the macroscopic patterns of bone destruction caused by breast cancer.

RESULT

Of the five skeletons, two presented metastatic lesions. In the first, lesions were observed in a disseminated form, affecting almost all bones. The lesions were predominantly osteolytic and ellipsoid-shaped; however, mixed and circular lesions were also found. The second skeleton presented four lesions of mixed characteristics. The finding of bone lesions in the macroscopic analysis of skeletons may reveal a more advanced stage of the neoplasm, as well as its dissemination in areas little rich in hematopoietic tissue, such as the diaphyses of long bones, a situation widely observed in the first reported case.

CONCLUSION

Besides providing more excellent knowledge of their macroscopic presentation, bone metastatic lesions may act as an individualizing factor in human identification cases, narrowing the sample of possible victims.

Metabolic crosstalk between stromal and malignant cells in the bone marrow niche

Bone marrow is the primary site of blood cell production in adults and serves as the source of osteoblasts and osteoclasts that maintain bone homeostasis. The medullary microenvironment is also involved in malignancy, providing a fertile soil for the growth of blood cancers or solid tumors metastasizing to bone. The cellular composition of the bone marrow is highly complex, consisting of hematopoietic stem and progenitor cells, maturing blood cells, skeletal stem cells, osteoblasts, mesenchymal stromal cells, adipocytes, endothelial cells, lymphatic endothelial cells, perivascular cells, and nerve cells. Intercellular communication at different levels is essential to ensure proper skeletal and hematopoietic tissue function, but it is altered when malignant cells colonize the bone marrow niche. While communication often involves soluble factors such as cytokines, chemokines, and growth factors, as well as their respective cell-surface receptors, cells can also communicate by exchanging metabolic information. In this review, we discuss the importance of metabolic crosstalk between different cells in the bone marrow microenvironment, particularly concerning the malignant setting.

Metastatic Breast Cancer: Review of Emerging Nanotherapeutics

Metastases of breast cancer (BC) are often referred to as stage IV breast cancer due to their severity and high rate of mortality. The median survival time of patients with metastatic BC is reduced to 3 years. Currently, the treatment regimens for metastatic BC are similar to the primary cancer therapeutics and are limited to conventional chemotherapy, immunotherapy, radiotherapy, and surgery. However, metastatic BC shows organ-specific complex tumor cell heterogeneity, plasticity, and a distinct tumor microenvironment, leading to therapeutic failure. This issue can be successfully addressed by combining current cancer therapies with nanotechnology. The applications of nanotherapeutics for both primary and metastatic BC treatments are developing rapidly, and new ideas and technologies are being discovered. Several recent reviews covered the advancement of nanotherapeutics for primary BC, while also discussing certain aspects of treatments for metastatic BC. This review provides comprehensive details on the recent advancement and future prospects of nanotherapeutics designed for metastatic BC treatment, in the context of the pathological state of the disease. Furthermore, possible combinations of current treatment with nanotechnology are discussed, and their potential for future transitions in clinical settings is explored.

Osteocytes: New Kids on the Block for Cancer in Bone Therapy

The tumor microenvironment plays a central role in the onset and progression of cancer in the bone. Cancer cells, either from tumors originating in the bone or from metastatic cancer cells from other body systems, are located in specialized niches where they interact with different cells of the bone marrow. These interactions transform the bone into an ideal niche for cancer cell migration, proliferation, and survival and cause an imbalance in bone homeostasis that severely affects the integrity of the skeleton. During the last decade, preclinical studies have identified new cellular mechanisms responsible for the dependency between cancer cells and bone cells. In this review, we focus on osteocytes, long-lived cells residing in the mineral matrix that have recently been identified as key players in the spread of cancer in bone. We highlight the most recent discoveries on how osteocytes support tumor growth and promote bone disease. Additionally, we discuss how the reciprocal crosstalk between osteocytes and cancer cells provides the opportunity to develop new therapeutic strategies to treat cancer in the bone.

Potential therapeutic role for pigment epithelium-derived factor in post-menopausal breast cancer bone metastasis

OBJECTIVES

This review discusses key oestrogens associated with the circulating pre- and post-menopausal milieu and how they may impact intratumoral oestrogen levels and breast cancer (BC) metastasis. It also identifies critical steps in BC metastasis to bone from the viewpoint of pigment epithelium-derived factor (PEDF) function, and discusses the role of several associated pro-metastatic biomarkers in BC bone metastasis.

KEY FINDINGS

PEDF is regulated by oestrogen in a number of oestrogen-sensitive tissues. Changes in circulating oestrogen levels associated with menopause may enhance the growth of BC bone metastases, leading to the establishment of a pre-metastatic niche. The establishment of such a pre-metastatic niche is driven by several key mediators, with pro-osteoclastic and pro-metastatic function which are upregulated by BC cells. These mediators appear to be regulated by oestrogen, as well as differentially affected by menopausal status. PEDF interacts with several pro-metastatic, pro-osteoclastic biomarkers, including C-X-C motif chemokine receptor 4 (CXCR4) and nuclear factor kappa B (NFκB) in BC bone metastasis.

CONCLUSION

Mediators such as CXCR4 and MT1-MMP underpin the ability of PEDF to function as an antimetastatic in other cancers such as osteosarcoma, highlighting the possibility that this serpin could be used as a therapeutic against BC metastasis in future.

CD44 in Bone Metastasis Development: A Key Player in the Fate Decisions of the Invading Cells?

A participant in key developmental processes, the adhesion glycoprotein CD44 is also expressed in several types of malignancies and can promote metastasis. In addition, the expression of CD44 isoforms in different types of cancer such as prostate and breast cancers may facilitate bone metastases by enhancing tumorigenicity, osteomimicry, cell migration, homing to bone, and anchorage within the bone specialized domains. Moreover, there is evidence that the CD44-ICD fragments in breast cancer cells may promote the cells' osteolytic nature. Yet the mechanisms by which CD44 and its downstream effectors promote the establishment of these cells within the bone are not fully elucidated. In this review, we summarize the current data on the roles played by CD44 in cancer progression and bone metastasis and the possible effects of its interaction with the different components of the bone marrow milieu.

The CDK4/6 Inhibitor Palbociclib Inhibits Estrogen-Positive and Triple Negative Breast Cancer Bone Metastasis In Vivo

CDK 4/6 inhibitors have demonstrated significant improved survival for patients with estrogen receptor (ER) positive breast cancer (BC). However, the ability of these promising agents to inhibit bone metastasis from either ER+ve or triple negative BC (TNBC) remains to be established. We therefore investigated the effects of the CDK 4/6 inhibitor, palbociclib, using in vivo models of breast cancer bone metastasis. In an ER+ve T47D model of spontaneous breast cancer metastasis from the mammary fat pad to bone, primary tumour growth and the number of hind limb skeletal tumours were significantly lower in palbociclib treated animals compared to vehicle controls. In the TNBC MDA-MB-231 model of metastatic outgrowth in bone (intracardiac route), continuous palbociclib treatment significantly inhibited tumour growth in bone compared to vehicle. When a 7-day break was introduced after 28 days (mimicking the clinical schedule), tumour growth resumed and was not inhibited by a second cycle of palbociclib, either alone or when combined with the bone-targeted agent, zoledronic acid (Zol), or a CDK7 inhibitor. Downstream phosphoprotein analysis of the MAPK pathway identified a number of phosphoproteins, such as p38, that may contribute to drug-insensitive tumour growth. These data encourage further investigation of targeting alternative pathways in CDK 4/6-insensitive tumour growth.

Effect of Nano- and Microzinc Supplementation on the Mineral Composition of Bones of Rats with Induced Mammary Gland Cancer

BACKGROUND

The aim of this study was to determine changes in the mineral composition of the bones of rats with chemically induced mammary gland cancer and to attempt to establish whether a specific diet modification involving the inclusion of zinc ions in two forms-nano and micro-will affect the mineral composition of the bones.

METHODS

Female Sprague-Dawley rats were used for the research. The animals were randomly assigned to three experimental groups. All animals were fed a standard diet (Labofeed H), and selected groups additionally received zinc nanoparticles or microparticles in the amount of 4.6 mg/mL. To induce mammary cancer, the animals were given 7,12-dimethyl-1,2-benz[a]anthracene. The content of Ag, As, B, Ba, Cd, Cr, Cu, Mn, Ni, Pb, Rb, Se, Sr, Tl, U, and V was determined using ICP-MS, while that of Ca, Fe, K, Mg, Na, and Zn was determined using FAAS.

RESULTS

The use of a diet enriched with zinc nano- or microparticles significantly influenced the content of the elements tested. In the bones of rats fed a diet with zinc nanoparticles, changes were found in the content of Ca, Mg, Zn, Cd, U, V, and Tl, while in the case of the diet supplemented with zinc microparticles, there were differences in six elements-Ca, Mg, B, Cd, Ag, and Pb-compared to animals receiving an unsupplemented diet.

CONCLUSIONS

The content of elements in the bone tissue of rats in the experimental model indicates disturbances of mineral metabolism in the tissue at an early stage of mammary cancer.

Schwann Cell Insulin-like Growth Factor Receptor Type-1 Mediates Metastatic Bone Cancer Pain in Mice

Insulin growth factor-1 (IGF-1), an osteoclast-dependent osteolysis biomarker, contributes to metastatic bone cancer pain (MBCP), but the underlying mechanism is poorly understood. In mice, the femur metastasis caused by intramammary inoculation of breast cancer cells resulted in IGF-1 increase in femur and sciatic nerve, and IGF-1-dependent stimulus/non-stimulus-evoked pain-like behaviors. Adeno-associated virus-based shRNA selective silencing of IGF-1 receptor (IGF-1R) in Schwann cells, but not in dorsal root ganglion (DRG) neurons, attenuated pain-like behaviors. Intraplantar IGF-1 evoked acute nociception and mechanical/cold allodynia, which were reduced by selective IGF-1R silencing in DRG neurons and Schwann cells, respectively. Schwann cell IGF-1R signaling promoted an endothelial nitric oxide synthase-mediated transient receptor potential ankyrin 1 (TRPA1) activation and release of reactive oxygen species that, via macrophage-colony stimulating factor-dependent endoneurial macrophage expansion, sustained pain-like behaviors. Osteoclast derived IGF-1 initiates a Schwann cell-dependent neuroinflammatory response that sustains a proalgesic pathway that provides new options for MBCP treatment.

PECAM1 plays a role in the pathogenesis and treatment of bone metastases

Bone is the third most common metastatic site for all primary tumors, the common primary focus of bone metastases include breast cancer, prostate cancer, and so on. And the median survival time of patients with bone metastases is only 2–3 years. Therefore, it is urgent to develop new targets to diagnose and treat bone metastases. Based on two data sets GSE146661 and GSE77930 associated with bone metastases, it was found that 209 genes differentially expressed in bone metastases group and control group. PECAM1 was selected as hub-gene for the follow-up research after constructing protein-protein interaction (PPI) network and enrichment analysis. Moreover, q-PCR analysis verified that the expression of PECAM1 decreased in bone metastatic tumor tissues. PECAM1 was believed to be possibly related to the function of osteoclasts, we knocked down the expression of PECAM1 with shRNA in lymphocytes extracted from bone marrow nailed blood. The results indicated that sh-PECAM1 treatment could promote osteoclast differentiation, and the sh-PECAM1-treated osteoclast culture medium could significantly promote the proliferation and migration of tumor cells. These results suggested that PECAM1 may be a potential biomarker for the diagnosis and treatment of bone metastases of tumor.

Research progress of bone metastases: From disease recognition to clinical practice

Bone metastases, as one of the common types of metastatic tumors, have a great impact on the survival period and quality of life of patients. Bone metastases are usually characterized by bone destruction. Skeletal related events caused by bone destruction often lead to pain, pathological fractures and even paralysis. In this review, we provide a detailed explanation of bone metastases from the epidemiology, clinical features, pathogenesis, and recently developed clinical treatment viewpoints. We concluded that the incidence of bone metastases is increasing gradually, with serious clinical symptoms, complex pathogenesis and diverse clinical treatment. Tumor cells, immune cells, osteoblasts/osteoclasts and other cells as well as cytokines and enzymes all play a key role in the pathogenesis of bone metastases. We believe that the future treatment of bone metastases will be diversified and comprehensive. Some advanced technologies, such as nanomedicine, could be used for treatment, but this depends on understanding how disease occurs. With the development of treatment, the survival time and quality of life of patients will be improved.

The role played by ailanthone in inhibiting bone metastasis of breast cancer by regulating tumor-bone microenvironment through the RANKL-dependent pathway

Introduction: Bone metastasis of breast cancer (BC) is a process in which the disruption of the bone homeostatic microenvironment leads to an increase in osteoclast differentiation. Ailanthus altissima shows an inhibitory effect on osteoclast differentiation. Ailanthone (AIL) refers to a natural compound isolated from Ailanthus altissima, a Chinese herbal medicine, and has effective anti-tumor activity in numerous cell lines. Its impact on bone metastases for BC is yet unclear. Methods: We measured the effect of AIL on MDA-MB-231 cells by wound healing experiments, Transwell and colony formation experiment. Using the Tartrate-resistant Acid Phosphatase (TRAP) staining tests, filamentous (F-actin) staining and bone resorption test to detect the effect of AIL on the osteoclast cell differentiation of the Bone Marrow-derived Macrophages (BMMs), activated by the MDA-MB-231 cell Conditioned Medium (MDA-MB-231 CM) and the Receptor Activator of Nuclear factor-κB Ligand (RANKL),and to explore its possibility Mechanisms. In vivo experiments verified the effect of AIL on bone destruction in breast cancer bone metastasis model mice. Results: In vitro, AIL significantly decrease the proliferation, migration and infiltration abilities of MDA-MB-231 cells at a safe concentration, and also reduced the expression of genes and proteins involved in osteoclast formation in MDA-MB-231 cells. Osteoclast cell differentiation of the BMMs, activated by MDA-MB-231 CM and RANKL, were suppressed by AIL in the concentration-dependent manner. Additionally, it inhibits osteoclast-specific gene and protein expression. It was noted that AIL inhibited the expression of the osteoclast differentiation-related cytokines RANKL and interleukin-1β (IL-1β) that were secreted by the MDA-MB-231 cells after upregulating the Forkhead box protein 3 (FOXP3) expression. Furthermore, AIL also inhibits the expression of the Mitogen-Activated Protein Kinase (MAPK), Phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT), and Nuclear factor-κB Ligand (NF-κB) signaling pathways, which then suppresses the MDA-MB-231CM-induced development of Osteoclasts. Conclusion: Our study shows that AIL blocks osteoclast differentiation in the bone metastasis microenvironment by inhibiting cytokines secreted by BC cells, which may be a potential agent for the treatment of BC and its secondary bone metastasis.

Cytokines as Potential Therapeutic Targets and their Role in the Diagnosis and Prediction of Cancers

The death rate from cancer is declining as a result of earlier identification and more advanced treatments. Nevertheless, a number of unfavourable adverse effects, including prolonged, long-lasting inflammation and reduced immune function, usually coexist with anti-cancer therapies and lead to a general decline in quality of life. Improvements in standardized comprehensive therapy and early identification of a variety of aggressive tumors remain the main objectives of cancer research. Tumor markers in those with cancer are tumor- associated proteins that are clinically significant. Even while several tumor markers are routinely used, they don't always provide reliable diagnostic information. Serum cytokines are promising markers of tumor stage, prognosis, and responsiveness to therapy. In fact, several cytokines are currently proposed as potential biomarkers in a variety of cancers. It has actually been proposed that the study of circulatory cytokines together with biomarkers that are particular to cancer can enhance and accelerate cancer diagnosis and prediction, particularly via blood samples that require minimal to the absence of invasion. The purpose of this review was to critically examine relevant primary research literature in order to elucidate the role and importance of a few identified serum cytokines as prospective therapeutic targets in oncological diseases.

Regulation of bone homeostasis by MERTK and TYRO3

The fine equilibrium of bone homeostasis is maintained by bone-forming osteoblasts and bone-resorbing osteoclasts. Here, we show that TAM receptors MERTK and TYRO3 exert reciprocal effects in osteoblast biology: Osteoblast-targeted deletion of MERTK promotes increased bone mass in healthy mice and mice with cancer-induced bone loss, whereas knockout of TYRO3 in osteoblasts shows the opposite phenotype. Functionally, the interaction of MERTK with its ligand PROS1 negatively regulates osteoblast differentiation via inducing the VAV2-RHOA-ROCK axis leading to increased cell contractility and motility while TYRO3 antagonizes this effect. Consequently, pharmacologic MERTK blockade by the small molecule inhibitor R992 increases osteoblast numbers and bone formation in mice. Furthermore, R992 counteracts cancer-induced bone loss, reduces bone metastasis and prolongs survival in preclinical models of multiple myeloma, breast- and lung cancer. In summary, MERTK and TYRO3 represent potent regulators of bone homeostasis with cell-type specific functions and MERTK blockade represents an osteoanabolic therapy with implications in cancer and beyond.

Exercise and Bone Health in Cancer: Enemy or Ally?

Bone health is often threatened in cancer patients. Bone metastasis and osteoporosis frequently occur in patients with cancer and may lead to different skeletal-related events, which may negatively affect patients' quality of life and are associated with high mortality risk. Physical exercise has been recognized as a potential adjunctive strategy in the cancer setting to improve physical function as well as treatment-related side effects. Nevertheless, exercise is often not recommended to patients with bone health impairments due to safety concerns. In the current review, we aimed, through a comprehensive review of the evidence, to explore the impact of exercise in terms of safety profile, bone outcomes, and the effects on other outcomes in patients with cancer affected by bone metastasis or at high risk of losing bone. Additionally, we explored the potential mechanisms by which exercise may act on bone, particularly the impact of mechanical load on bone remodeling. Finally, considerations about exercise prescription and programming in these populations are also discussed.

RRBP1 depletion of bone metastatic cancer cells contributes to enhanced expression of the osteoblastic phenotype

Bone metastatic cancer-secreted extracellular factors are capable of modifying the bone microenvironment through interacting with bone cells, including osteoblasts. Reticulum ribosome-binding protein 1 (RRBP1) is substantially expressed in certain bone metastatic cancer cells. This study was undertaken to determine whether RRBP1 from bone metastatic cancer cells affects the osteoblastic phenotype expression. Breast and prostate cancer cells, MDA-MB-231 and PC3, were cultured, respectively, followed by collecting conditioned mediums (CMs) and identifying the abundance of RRBP1 in CMs using LC-MS/MS. MC3T3-E1 cells were cultured with a mixed medium (including CMs from shRRBP1-transduced two-type cancer cells) with or without endoplasmic reticulum (ER) stress inhibitor 4-PBA, followed by measuring the levels of osteoblastic phenotype expression and biomarkers of ER stress using western blotting, qPCR, and ARS staining, respectively. Similar experiments were performed in shRrbp1-transduced MC3T3-E1 cells cultured with a mixed medium (including CMs from the two-type cancer cells). Bone formation parameters were measured in the tibia of nude mice injected with shRRBP1-transduced two-type cancer cells using micro-CT analysis. These results showed that RRBP1 is the sole shared high-abundance protein in CMs from the two-type cancer cells, involving osteoblast differentiation. CMs from shRRBP1-transduced two-type cells boosted the osteoblastic phenotype expression partially through increasing ER stress. CMs from the two-type cancer cells partially offset the similar alterations induced by shRrbp1 in MC3T3-E1 cells. Injection with shRRBP1-transduced two-type cells ameliorated the bone lesions in nude mice. Therefore, RRBP1 depletion of bone metastatic cancer enhanced the osteoblastic phenotype expression, suggesting a role of RRBP1 in the bone microenvironment.

Wnt Signaling in the Development of Bone Metastasis

Wnt signaling occurs through evolutionarily conserved pathways that affect cellular proliferation and fate decisions during development and tissue maintenance. Alterations in these highly regulated pathways, however, play pivotal roles in various malignancies, promoting cancer initiation, growth and metastasis and the development of drug resistance. The ability of cancer cells to metastasize is the primary cause of cancer mortality. Bone is one of the most frequent sites of metastases that generally arise from breast, prostate, lung, melanoma or kidney cancer. Upon their arrival to the bone, cancer cells can enter a long-term dormancy period, from which they can be reactivated, but can rarely be cured. The activation of Wnt signaling during the bone metastasis process was found to enhance proliferation, induce the epithelial-to-mesenchymal transition, promote the modulation of the extracellular matrix, enhance angiogenesis and immune tolerance and metastasize and thrive in the bone. Due to the complexity of Wnt pathways and of the landscape of this mineralized tissue, Wnt function during metastatic progression within bone is not yet fully understood. Therefore, we believe that a better understanding of these pathways and their roles in the development of bone metastasis could improve our understanding of the disease and may constitute fertile ground for potential therapeutics.

Microfluidic Co-culture Platforms for Studying Osteocyte Regulation of Other Cell Types under Dynamic Mechanical Stimulation

PURPOSE OF REVIEW

Osteocytes are the most abundant cell type in bone. These unique cells act primarily as mechanosensors and play crucial roles in the functional adaptation of bone tissue. This review aims to summarize the recent microfluidic studies on mechanically stimulated osteocytes in regulating other cell types.

RECENT FINDINGS

Microfluidics is a powerful technology that has been widely employed in recent years. With the advantages of microfluidic platforms, researchers can mimic multicellular environments and integrate dynamic systems to study osteocyte regulation under mechanical stimulation. Microfluidic platforms have been developed to investigate mechanically stimulated osteocytes in the direct regulation of multiple cell types, including osteoclasts, osteoblasts, and cancer cells, and in the indirect regulation of cancer cells via endothelial cells. Overall, these microfluidic studies foster the development of treatment approaches targeting osteocytes under mechanical stimulation.

YTHDF2-mediated FGF14-AS2 decay promotes osteolytic metastasis of breast cancer by enhancing RUNX2 mRNA translation

BACKGROUND

LncRNA FGF14-AS2 is a critical suppressor in breast cancer (BCa) metastasis. However, whether FGF14-AS2 plays a role in the bone metastasis of BCa remains unknown.

METHODS

TRAP assay and intratibial injection were carried out to evaluate the role of FGF14-AS2 in BCa bone metastasis in vitro and in vivo. Polyribosome profiling was done to examine the translation level. RNA pulldown combined with LC/MS was performed to identify the lncRNA-binding partner, RIP, dual-luciferase assay, and Co-IP assays as well to testify these physical interactions. The prognostic value of FGF14-AS2 expression level in BCa patients was analysed using Kaplan-Meier Plotter.

RESULTS

We found that FGF14-AS2 suppresses osteoclast differentiation and osteolytic metastasis of BCa. Mechanistically, FGF14-AS2 suppresses the translation of RUNX2 by inhibiting the assembly of eIF4E/eIF4G complex and the phosphorylation of eIF4E, thereby reducing the transcription of RANKL, an essential regulator of osteoclast differentiation. Moreover, FGF14-AS2 is downregulated by YTHDF2-mediated RNA degradation in an m6A-dependent manner. Clinically, patients with high YTHDF2 and low FGF14-AS2 expression levels showed worse distant metastasis-free survival (DMFS).

CONCLUSIONS

FGF14-AS2 plays a crucial role in osteolytic metastasis, and may serve as a promising prognostic biomarker and therapeutic target for BCa bone metastasis.

Effects of Whole-Body Vibration on Breast Cancer Bone Metastasis and Vascularization in Mice

We evaluated whether whole-body vibration (WBV) prevented bone loss induced by breast cancer (BC) metastasis and the involvement of bone marrow vasculature. One day after orthotopic transplantation of mammary 4T1 tumor cells, 8-week-old BALB/c mice were subjected to 0.3 g/90 Hz vertical vibration for 20 min/day for 5 days/week (BC-WBV) or sham-handled (BC-Sham) over 3 weeks. Age-matched intact mice (Intact) were also sham-handled. Both tibiae were harvested from BC-WBV (n = 7), BC-Sham (n = 9), and Intact (n = 5) mice for bone structure imaging by synchrotron radiation-based computed tomography (SRCT) and hematoxylin and eosin staining, whereas right tibiae were harvested from other BC-WBV and BC-Sham (n = 6 each) mice for vascular imaging by SRCT. Tumor cells were similarly widespread in the marrow in BC-WBV and BC-Sham mice. In BC-Sham mice, cortical bone volume, trabecular volume fraction, trabecular thickness, trabecular number density, and bone mineral density were smaller, and marrow volume and trabecular separation were larger than in Intact mice. However, although trabecular thickness was smaller in BC-WBV than Intact mice, the others did not differ between the two groups. Serum osteocalcin tended to be higher in BC-WBV than BC-Sham mice. Compared with BC-Sham mice, BC-WBV mice had a smaller vessel diameter, a trend of a larger vessel number density, and smaller vessel diameter heterogeneity. In conclusion, WBV mitigates bone loss in BC bone metastasis, which may be partly due to increased bone anabolism. The alteration of marrow vasculature appears to be favorable for anti-tumor drug delivery. Further studies are needed to clarify the multiple actions of WBV on bone, tumor, and marrow vasculature and how they contribute to bone protection in BC metastasis.

Parathyroid hormone-related protein (PTHrP) and malignancy

PTHrP (parathyroid hormone related protein) is an important mediator of malignancy-related tumor progression and hypercalcemia that shares considerable homology and functionality with parathyroid hormone. In this chapter, we review what has been elucidated to date regarding PTHrP's role in malignancies. Starting with a review of calcium metabolism and regulation, we then summarize the discovery and structure of PTHrP and development of sensitive immunoassays for specific measurement. Subsequently, we explore its role in tumor progression, with emphasis on the primary tumor as well as skeletal and non-osseus metastases. We then consider the clinical implications of PTHrP in cancer before concluding with a discussion of both established and potential treatments for malignancy associated hypercalcemia and bone metastases.

Influence of alcohol sensitivity on bone metastases and skeletal-related events in primary operable breast cancer: A retrospective cohort study

Background

Bone metastases in breast cancer patients are a common concern for medical doctors and dentists. Bone-modifying agents, which are necessary to prevent skeletal-related events (SREs), are associated with osteonecrosis of the jaw as an adverse side effect. Hypersensitivity to alcohol is an unfavorable response caused by deficiency of aldehyde dehydrogenase-2 (ALDH2) activity. Inactive ALDH2 is associated with osteoporosis, but its influence on bone metastases is unclear. The aim of our study was to evaluate the effects of alcohol sensitivity on bone metastases and SREs in primary operable breast cancer patients.

Methods

We retrospectively analyzed patients who were administered docetaxel, an anti-tumor agent, for histologically diagnosed breast cancer between April 2004 and September 2015. Alcohol sensitivity was assessed based on medical records of hypersensitivity to alcohol. The primary endpoint was time to bone metastases and the secondary endpoint was time to first SRE from the initial docetaxel administration. Data were stratified by alcohol sensitivity and tumor stages, and differences were estimated by the Kaplan-Meier method. Prognostic risk factors were analyzed by the multivariate Cox proportional hazards model.

Results

The median follow-up period of patients with high sensitivity to alcohol (n = 45) was 54 months and that for those with low sensitivity (n = 287) was 64 months. Stratification by alcohol sensitivity revealed that tumor stage exhibited significant correlations with the cumulative incidence of bone metastases in low-sensitivity patients; however, no differences were found in high-sensitivity patients. In multivariate analysis, alcohol sensitivity was a significant prognostic risk factor for bone metastases (HR 2.721, 95% CI 1.268–5.841, P = 0.010).

Conclusion

Alcohol sensitivity may be a prognostic risk factor for bone metastases. More detailed genetic investigations and metabolic analyses are needed.

The role of percutaneous vertebral augmentation in patients with metastatic breast cancer: Literature review including report of two cases

Patients with metastatic breast cancer are at high risk for developing vertebral compression fractures due to underlying bone metastases and bone density loss. Vertebral augmentation techniques including percutaneous vertebroplasty and percutaneous balloon kyphoplasty are techniques used to stabilize compression fractures and improve pain. However, rare complications from these interventions have been observed, including spinal cord compression, nerve root compression, venous cement embolism, and pulmonary cement embolism. These complications pose unique potential challenges for patients with cancer who may already have decreased lung function and potential for venous thromboembolism. In this review, we first describe the role of percutaneous vertebral augmentations in patients with metastatic cancer, with a particular focus on patients with breast cancer. Then, we describe complications of vertebral augmentation in two patients with metastatic breast cancer including long-term symptomatic and radiographic follow-up.

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Balloon kyphoplasty and percutaneous vertebroplasty are used to stabilize compression fractures and improve pain.

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Leakage of bone cement can cause cement emboli which can depsit in locations such as the pulmonary and renal vasculature.

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Management of cement emboli depends on the amount of cement embolized and the severity of symptoms.

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Future studies are needed to better understand the long-term radiographic and clinical consequences of cement emboli.

Fundamentals of bone vasculature: Specialization, interactions and functions

Angiogenesis, hematopoiesis and osteogenesis are fundamental processes mediating complex and essential biological functions. In the bone marrow, endothelial cells (ECs) are a principal mediator of regulatory signals that govern hematopoietic and mesenchymal stem cells. EC and osteoblast interactions and niche functions of ECs are fundamental in maintaining bone health and coordinating repair and regeneration following injury. These cellular interactions are subject to dysregulation and deterioration under stress, aging, chronic disease states and malignancy. Thus, the prospect of manipulating the bone vasculature has tremendous potential to advance therapeutic interventions for the management of bone diseases. This review discusses the current state of vascular-skeletal tissue interactions focusing on osteoblast and hematopoietic stem cells interaction with ECs.

Engineer a pre-metastatic niched microenvironment to attract breast cancer cells by utilizing a 3D printed polycaprolactone/nano-hydroxyapatite osteogenic scaffold - An in vitro model system for proof of concept

Breast cancer bone metastasis is not a random process. It is affected by the local microenvironment which determines the propensity of cancer cells to invade and colonize into the secondary sites. This microenvironment is termed a pre-metastatic niche. With the flexibility to incorporate different biofactors, tissue-engineering scaffolds provide an advantageous environment to promote "designed" osteogenesis that may mimic the bony pre-metastatic niche. In the current study, designed polycaprolactone (PCL) scaffolds enriched with nano-hydroxyapatite (nHA) were fabricated through three-dimensional (3D) printing. Subsequently, human mesenchymal stem cells (hMSCs) were seeded onto PCL-nHA scaffolds for osteogenic differentiation to establish the pre-metastatic niched microenvironment. Furthermore, transwell migration assay was used to investigate recruitment of MDA-MB-231, MCF-7, and MDA-MB-453 breast cancer cells to the osseous PCL-nHA scaffolds. Our results showed that the mRNA levels of alkaline phosphatase (ALP), runt-related transcription factor 2 (Runx2), and osteocalcin (OCN) of hMSCs on the PCL-nHA scaffolds were dramatically increased compared those with the PCL scaffolds (control) at day 7, 14, and 28. Meanwhile, the migration analysis showed that the higher maturation of osteogenesis and bone metabolism collectively contributed to the creation of a more favorable niched site for the cancerous invasion. Moreover, one of the hypothesized key mediators for the promoted migration, CXCL12, was confirmed using an assay of antagonist LIT-927. This early study demonstrated that a designed tissue engineering scaffold can be utilized to create a bone-mimicking environment that serves as a novel platform to recapitulate the pre-metastatic niche and help interrogate the scheme of bone metastasis by breast cancer.

Discovering the key genes and important DNA methylation regions in breast cancer

Background

Breast cancer is the malignant tumor with the highest incidence in women. DNA methylation has an important effect on breast cancer, but the effect of abnormal DNA methylation on gene expression in breast cancer is still unclear. Therefore, it is very important to find therapeutic targets related to DNA methylation.

Results

In this work, we calculated the DNA methylation distribution and gene expression level in cancer and para-cancerous tissues for breast cancer samples. We found that DNA methylation in key regions is closely related to gene expression by analyzing the relationship between the distribution characteristics of DNA methylation in different regions and the change of gene expression level. Finally, the 18 key genes (17 tumor suppressor genes and 1 oncogene) related to prognosis were confirmed by the survival analysis of clinical data. Some important DNA methylation regions in these genes that result in breast cancer were found.

Conclusions

We believe that 17 TSGs and 1 oncogene may be breast cancer biomarkers regulated by DNA methylation in key regions. These results will help to explore DNA methylation biomarkers as potential therapeutic targets for breast cancer.

Supplementary Information

The online version contains supplementary material available at 10.1186/s41065-022-00220-5.

Withaferin A: From Ancient Remedy to Potential Drug Candidate

Withaferin A (WA) is a pivotal withanolide that has conquered a conspicuous place in research, owning to its multidimensional biological properties. It is an abundant constituent in Withania somnifera Dunal. (Ashwagandha, WS) that is one of the prehistoric pivotal remedies in Ayurveda. This article reviews the literature about the pharmacological profile of WA with special emphasis on its anticancer aspect. We reviewed research publications concerning WA through four databases and provided a descriptive analysis of literature without statistical or qualitative analysis. WA has been found as an effective remedy with multifaceted mechanisms and a broad spectrum of pharmacological profiles. It has anticancer, anti-inflammatory, antiherpetic, antifibrotic, antiplatelet, profibrinolytic, immunosuppressive, antipigmentation, antileishmanial, and healing potentials. Evidence for wide pharmacological actions of WA has been established by both in vivo and in vitro studies. Further, the scientific literature accentuates the role of WA harboring a variable therapeutic spectrum for integrative cancer chemoprevention and cure. WA is a modern drug from traditional medicine that is necessary to be advanced to clinical trials for advocating its utility as a commercial drug.

DZNep promotes mouse bone defect healing via enhancing both osteogenesis and osteoclastogenesis

Background

Enhancer of zeste homolog 2 (EZH2) is a novel oncogene that can specifically trimethylate the histone H3 lysine 27 (H3K27me3) to transcriptionally inhibit the expression of downstream tumor-suppressing genes. As a small molecular inhibitor of EZH2, 3-Deazaneplanocin (DZNep) has been widely studied due to the role of tumor suppression. With the roles of epigenetic regulation of bone cells emerged in past decades, the property and molecular mechanism of DZNep on enhancing osteogenesis had been reported and attracted a great deal of attention recently. This study aims to elucidate the role of DZNep on EZH2-H3K27me3 axis and downstream factors during both osteoclasts and osteoblasts formation and the therapeutic possibility of DZNep on bone defect healing.

Methods

Bone marrow-derived macrophages (BMMs) cells were cultured, and their responsiveness to DZNep was evaluated by cell counting kit-8, TRAP staining assay, bone resorption assay, podosome actin belt. Bone marrow-derived mesenchymal stem cells (BMSC) were cultured and their responsiveness to DZNep was evaluated by cell counting kit-8, ALP and AR staining assay. The expression of nuclear factor-κB (NF-κB), mitogen-activated protein kinase (MAPK), Wnt signaling pathway was determined by qPCR and western blotting. Mouse bone defect models were created, rescued by DZNep injection, and the effectiveness was evaluated by X-ray and micro-CT and histological staining.

Results

Consistent with the previous study that DZNep enhances osteogenesis via Wnt family member 1(Wnt1), Wnt6, and Wnt10a, our results showed that DZNep also promotes osteoblasts differentiation and mineralization through the EZH2-H3K27me3-Wnt4 axis. Furthermore, we identified that DZNep promoted the receptor activator of nuclear factor-κB (NF-κB) ligand (RANKL)-induced osteoclast formation via facilitating the phosphorylation of IKKα/β, IκB, and subsequently NF-κB nuclear translocation, which credit to the EZH2-H3K27me3-Foxc1 axis. More importantly, the enhanced osteogenesis and osteoclastogenesis result in accelerated mice bone defect healing in vivo.

Conclusion

DZNep targeting EZH2-H3K27me3 axis facilitated the healing of mice bone defect via simultaneously enhancing osteoclastic bone resorption and promoting osteoblastic bone formation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02670-6.

Breast Cancer Cells Metastasize to the Tissue-Engineered Premetastatic Niche by Using an Osteoid-Formed Polycaprolactone/Nanohydroxyapatite Scaffold

It has been deemed that the premetastatic niche (PMN) plays a critical role in facilitating bone metastasis of breast cancer cells. Tissue engineering scaffolds provide an advantageous environment to promote osteogenesis that may mimic the bony premetastatic niches (BPMNs). In this study, human mesenchymal stem cells (hMSCs) were seeded onto designed polycaprolactone/nanohydroxyapatite (PCL-nHA) scaffolds for osteogenic differentiation. Subsequently, a coculture system was used to establish the tissue-engineered BPMNs by culturing breast cancer cells, hMSCs, and osteoid-formed PCL-nHA scaffolds. Afterwards, a migration assay was used to investigate the recruitment of MDA-MB-231, MCF-7, and MDA-MB-453 cells to the BPMNs' supernatants. The cancer stem cell (CSC) properties of these migrated cells were investigated by flow cytometry. Our results showed that the mRNA expression levels of alkaline phosphatase (ALP), Osterix, runt-related transcription factor 2 (Runx2), and collagen type I alpha 1 (COL1A1) on the PCL-nHA scaffolds were dramatically increased compared to the PCL scaffolds on days 11, 18, and 32. The expression of CXCL12 in these BPMNs was increased gradually over coculturing time, and it may be a feasible marker for BPMNs. Furthermore, migration analysis results showed that the higher maturation of BPMNs collectively contributed to the creation of a more favorable niched site for the cancerous invasion. The subpopulation of breast cancer stem cells (BCSCs) was more likely to migrate to fertile BPMNs. The proportion of BCSCs in metastatic MDA-MB-231, MCF-7, and MDA-MB-453 cells were increased by approximately 63.47%, 149.48%, and 127.60%. The current study demonstrated that a designed tissue engineering scaffold can provide a novel method to create a bone-mimicking environment that serves as a useable platform to recapitulate the BPMNs and help interrogate the scheme of bone metastasis by breast cancer.

Punicalin Attenuates Breast Cancer-Associated Osteolysis by Inhibiting the NF-κB Signaling Pathway of Osteoclasts

Background: Breast cancer bone metastasis and osteoporosis are both severe diseases that seriously threaten human health. These diseases are closely associated with osteolytic lesions. And osteoclasts are the key targets of this pathological process. Given the lack of effective preventive or treatment options against these diseases, the exploitation of new pharmacological agents is critically required.

Method: We assessed the efficacy of punicalin on receptor activator of nuclear factor-κB ligand (RANKL)-mediated osteoclast formation, F-actin ring formation, gene expression, bone resorption, nuclear factor-κB (NF-κB) as well as on mitogen-activated protein kinase (MAPK) signaling pathways and molecular docking in vitro. The impact of punicalin on breast cancer-induced osteoclastogenesis, breast cancer cell proliferation, and apoptosis were examined. Transwell assays were also performed. Moreover, we evaluated in vivo effects of punicalin in postmenopausal osteoporosis models and breast cancer bone metastasis model by micro-CT scanning and histomorphometry.

Results: Punicalin inhibited osteoclast formation, F-actin ring formation, bone resorption, as well as osteoclast-related gene expression by suppressing the NF-κB signaling pathway. In vitro, punicalin also suppressed the breast cancer-induced osteoclastogenesis, and proliferation, migration as well as invasion of MDA-MB-231 cells and dose-dependently promoted their apoptosis. In vivo, punicalin significantly suppressed breast cancer-induced osteolysis, breast cancer-associated bone metastasis, and ovariectomized (OVX)-mediated osteoporosis by repressing osteoclast and breast cancer cell.

Conclusion: Punicalin is expected to offer a novel treatment for the prevention of osteolysis diseases, including osteoporosis and breast cancer-associated osteolysis.

DNA damage-inducible transcript 3 restrains osteoclast differentiation and function

DNA damage-inducible transcript 3 (DDIT3), a member of the CCAAT/enhancer-binding protein (C/EBP) family, is involved in cellular apoptosis and differentiation. DDIT3 participates in the regulation of adipogenesis and osteogenesis in vitro and in vivo. However, the role of DDIT3 in osteoclastogenesis is not yet known. In this study, the involvement of DDIT3 in osteoclast differentiation and function was reported for the first time. CRISPR/Cas9-mediated DDIT3 knockout (KO) mice were generated for functional assessment. Tartrate-resistant acid phosphatase (TRAP) staining of distal femurs showed increased positive cells in DDIT3 KO mice. DDIT3 expression was downregulated during the receptor activator of nuclear factor κB ligand (RANKL)-induced osteoclast differentiation of bone marrow-derived macrophages (BMMs). The loss of DDIT3 increased the expression of osteoclast-specific markers, including nuclear factor of activated T-cells cytoplasmic 1 (NFATc1), TRAP, cathepsin K (CTSK), and dendritic cell-specific transmembrane protein (DC-STAMP) and promoted the formation of TRAP-positive multinucleated osteoclasts. The actin ring number and resorption area of bone slices were also increased in DDIT3 KO BMMs. Lentivirus-mediated DDIT3 overexpression significantly inhibited the osteoclast differentiation of RAW264.7 cells. In the tumor necrosis factor-α-induced osteolysis model, DDIT3 deficiency enhanced osteoclast formation and aggravated bone resorption. DDIT3 inhibited osteoclast differentiation by regulating the C/EBPα-CTSK axis. Furthermore, DDIT3 KO intensified the RANKL-triggered activation of the MAPKs and Akt signaling pathways. Taken together, the results revealed the essential role of DDIT3 in osteoclastogenesis in vitro and in vivo and its close relationship with osteoclast-associated transcription factors and pathways.

Dynamic modeling of bone remodeling, osteolytic metastasis and PK/PD therapy: introducing variable order derivatives as a simplification technique

Bone is constantly being renewed: in the adult skeleton, bone resorption and formation are in a tightly coupled balance, allowing for a constant bone density to be maintained. Yet this micro-environment provides the necessary conditions for the growth and proliferation of tumor cells, and thus bone is a common site for the development of metastases, mainly from primary breast and prostate cancer. Mathematical and computational models with differential equations can replicate this bone remodeling process. These models have been extended to include the effects of disruptive tumor pathologies in the bone dynamics, as metastases contribute to the decoupling between bone resorption and formation and to the self-perpetuating tumor growth cycle. Such models may also contemplate the counteraction effects of currently used therapies, and, in the case of treatments with drugs, their pharmocokinetics and pharmacodynamics. We present a thorough overview of biochemical models for bone remodeling, in the presence of a tumour together with anti-cancer and anti-resorptive therapy, formulated as systems of first-order differential equations, or simplified using variable order derivatives. The latter models, of which some are new to this paper, result in equations with fewer parameters, and allow accounting for anomalous diffusion processes. In this way, more compact and parsimonious models, that promptly highlight tumorous bone interactions, are achieved, providing an effective framework to counteract the loss of bone integrity on the affected areas.

Incidence, prognosis and nomograms of breast cancer with bone metastases at initial diagnosis: a large population-based study

BACKGROUND

Bone is the most common metastatic site for breast cancer, and patients' condition will deteriorate when it occurs.

METHODS

We performed a retrospective analysis on 6482 breast cancer patients with bone metastases (BCBM), who were selected from the Surveillance, Epidemiology, and End Result (SEER) 18 registry database. The optimal age cut-points were generated by using the X-tile software. By using Cox regression, we selected independent prognostic factors from 21 variables, and plotted a visual nomogram to predict the probability of surviving to the median survival time. We also diagrammed a competing risk nomogram on the basis of competitive risk model.

RESULTS

Compared with other three common metastatic sites, the incidence of bone metastasis was the highest for patients with breast cancer. The incidence of BCBM peaked around the age of 60, and a large majority of patients were between the ages of 50 and 70. The survival rate decreased with age, and the median survival time was about 19 months. Factors of age, race, marital status, grade, human epidermal growth factor receptor-2 (HER2) receptor, hormone receptor, concurrent brain metastasis, concurrent liver metastasis, concurrent lung metastasis, surgery and chemotherapy are strongly related to the prognosis of patients with BCBM. It was revealed that the C-index of the nomogram was 0.72 and the calibration curves showed good agreement between the nomogram prediction and actual observation.

CONCLUSION

Our practical nomograms provide a visual and user-friendly tool in the risk evaluation and prognostic prediction for breast cancer patients with bone metastases.

Disorders of Divalent Ions (Magnesium, Calcium, and Phosphorous) in Patients With Cancer

Disorders of the divalent ions (magnesium, calcium, and phosphorous) are frequently encountered in patients with cancer. Of these, hypomagnesemia, hypocalcemia, hypercalcemia, and hypophosphatemia are seen most commonly. These electrolyte disturbances may be related to the underlying malignancy or due to side effects of anticancer therapy. When caused by a paraneoplastic process, these abnormalities may portend a poor prognosis. Importantly, the development of severe electrolyte derangements may be associated with symptoms that negatively impact quality of life, preclude the administration of critical chemotherapeutic agents, or lead to life-threatening complications that require hospitalization and emergent treatment. In accordance, prompt recognition and treatment of these disorders is key to improving outcomes in patients living with cancer. This review will discuss selected derangements of the divalent ions seen in this population, with a focus on paraneoplastic and therapy-associated etiologies.

Exosomal miR-19a and IBSP cooperate to induce osteolytic bone metastasis of estrogen receptor-positive breast cancer

Bone metastasis is an incurable complication of breast cancer. In advanced stages, patients with estrogen-positive tumors experience a significantly higher incidence of bone metastasis (>87%) compared to estrogen-negative patients (<56%). To understand the mechanism of this bone-tropism of ER+ tumor, and to identify liquid biopsy biomarkers for patients with high risk of bone metastasis, the secreted extracellular vesicles and cytokines from bone-tropic breast cancer cells are examined in this study. Both exosomal miR-19a and Integrin-Binding Sialoprotein (IBSP) are found to be significantly upregulated and secreted from bone-tropic ER+ breast cancer cells, increasing their levels in the circulation of patients. IBSP is found to attract osteoclast cells and create an osteoclast-enriched environment in the bone, assisting the delivery of exosomal miR-19a to osteoclast to induce osteoclastogenesis. Our findings reveal a mechanism by which ER+ breast cancer cells create a microenvironment favorable for colonization in the bone. These two secreted factors can also serve as effective biomarkers for ER+ breast cancer to predict their risks of bone metastasis. Furthermore, our screening of a natural compound library identifies chlorogenic acid as a potent inhibitor for IBSP-receptor binding to suppress bone metastasis of ER+ tumor, suggesting its preventive use for bone recurrence in ER+ patients.

Engineered macrophages as near-infrared light activated drug vectors for chemo-photodynamic therapy of primary and bone metastatic breast cancer

Patients with primary and bone metastatic breast cancer have significantly reduced survival and life quality. Due to the poor drug delivery efficiency of anti-metastasis therapy and the limited response rate of immunotherapy for breast cancer, effective treatment remains a formidable challenge. In this work, engineered macrophages (Oxa(IV)@ZnPc@M) carrying nanomedicine containing oxaliplatin prodrug and photosensitizer are designed as near-infrared (NIR) light-activated drug vectors, aiming to achieve enhanced chemo/photo/immunotherapy of primary and bone metastatic tumors. Oxa(IV)@ZnPc@M exhibits an anti-tumor M1 phenotype polarization and can efficiently home to primary and bone metastatic tumors. Additionally, therapeutics inside Oxa(IV)@ZnPc@M undergo NIR triggered release, which can kill primary tumors via combined chemo-photodynamic therapy and induce immunogenic cell death simultaneously. Oxa(IV)@ZnPc@M combined with anti-PD-L1 can eliminate primary and bone metastatic tumors, activate tumor-specific antitumor immune response, and improve overall survival with limited systemic toxicity. Therefore, this all-in-one macrophage provides a treatment platform for effective therapy of primary and bone metastatic tumors.

Tumour-derived exosomal lncRNA-SOX2OT promotes bone metastasis of non-small cell lung cancer by targeting the miRNA-194-5p/RAC1 signalling axis in osteoclasts

Bone is a frequent metastatic site of non-small cell lung cancer (NSCLC), and bone metastasis (BoM) presents significant challenges for patient survival and quality of life. Osteolytic BoM is characterised by aberrant differentiation and malfunction of osteoclasts through modulation of the TGF-β/pTHrP/RANKL signalling pathway, but its upstream regulatory mechanism is unclear. In this study, we found that lncRNA-SOX2OT was highly accumulated in exosomes derived from the peripheral blood of NSCLC patients with BoM and that patients with higher expression of exosomal lncRNA-SOX2OT had significantly shorter overall survival. Additionally, exosomal lncRNA-SOX2OT derived from NSCLC cells promoted cell invasion and migration in vitro, as well as BoM in vivo. Mechanistically, we discovered that NSCLC cell-derived exosomal lncRNA-SOX2OT modulated osteoclast differentiation and stimulated BoM by targeting the miRNA-194-5p/RAC1 signalling axis and TGF-β/pTHrP/RANKL signalling pathway in osteoclasts. In conclusion, exosomal lncRNA-SOX2OT plays a crucial role in promoting BoM and may serve as a promising prognostic biomarker and treatment target in metastatic NSCLC.