MicroRNAs in Bone Metastasis

Association of miRNA and Bone Tumors: Future Therapeutic Inroads

Small endogenous non-coding RNA molecules known as micro-ribonucleic acids (miRNAs) control post-transcriptional gene regulation. A change in miRNA expression is related to various diseases, including bone tumors. Benign bone tumors are categorized based on matrix production and predominant cell type. Osteochondromas and giant cell tumors are among the most common bone tumors. Interestingly, miRNAs can function as either tumor suppressor genes or oncogenes, thereby determining the fate of a tumor. In the present review, we discuss various bone tumors with regard to their prognosis, pathogenesis, and diagnosis. The association between miRNAs and bone tumors, such as osteosarcoma, Ewing's sarcoma, chondrosarcoma, and giant-cell tumors, is also discussed. Moreover, miRNA may play an important role in tumor proliferation, growth, and metastasis. Knowledge of the dysregulation, amplification, and deletion of miRNA can be beneficial for the treatment of various bone cancers. The miRNAs could be beneficial for prognosis, treatment, future drug design, and treatment of resistant cases of bone cancer.

Non-coding RNA in exosomes: Regulating bone metastasis of lung cancer and its clinical application prospect

Lung cancer is a highly prevalent malignancy with poor prognosis and rapid progression. It most frequently metastasizes to the bone, where it can pose a severe threat to the patient's survival. Once metastasized, the disease is often incurable and can result in severe complications such as hypercalcemia, bone pain, fractures, spinal cord compression, and subsequent paralysis. Exosomes are bilayer vesicle nanoparticles secreted by most of the extracellular vesicles, which can be found in almost all organisms and play an essential role in intercellular communication. Through their ability to regulate related bone cells, exosomes carry bioactive molecules, including proteins, lipids, and non-coding RNAs (ncRNAs), that can be extremely important in bone remodeling. Studies have been conducted on the role play by proteins, lncRNA, and microRNA-all ncRNAs-carried by exosomes in the bone metastases of lung cancer. In this review, the latest progress of the regulatory mechanism of ncRNAs carried by exosomes in lung cancer bone metastasis has been reviewed. The clinical use of exosomes as a promising biomarker, drug transporter, and therapeutic target was highlighted to offer a novel diagnostic and treatment approach for patients with lung cancer bone metastases.

Secreted microRNAs in bone metastasis

Bone metastasis is a common complication in several solid cancers, including breast, prostate, and lung. In the bone microenvironment, metastatic cancer cells disturb bone homeostasis leading to osteolytic or osteosclerotic lesions. Osteolytic lesions are characterized by an increased osteoclast-mediated bone resorption while osteosclerotic lesions are caused by enhanced activity of osteoblasts and formation of poor-quality bone. A common feature in bone metastasis is the complex interplay between the cancer cells and the cells of the bone microenvironment, which can occur already before the cancer cells enter the distant site. Cancer cells at the primary site can secrete soluble factors and extracellular vesicles to bone to create a "pre-metastatic niche" i.e., prime the microenvironment permissive for cancer cell homing, survival, and growth. Once in the bone, cancer cells secrete factors to activate the osteoclasts or osteoblasts and the so called "vicious cycle of bone metastases". These pathological cell-cell interactions are largely dependent on secreted proteins. However, increasing evidence demonstrates that secreted RNA molecules, in particular small non-coding microRNAs are critical mediators of the crosstalk between bone and cancer cells. This review article discusses the role of secreted miRNAs in bone metastasis development and progression, and their potential as non-invasive biomarkers.

Integrative Bioinformatics Analysis Reveals That miR-524-5p/MEF2C Regulates Bone Metastasis in Prostate Cancer and Breast Cancer

Bone metastases are highly prevalent in patients with advanced prostate cancer and breast cancer and have a serious impact on the survival time and quality of life of these patients. It has been reported that microRNAs (miRNAs) are expressed abnormally in different types of cancer and metastases. However, it remains unknown whether the underlying miRNAs are associated with prostate and breast cancer bone metastasis. Differentially expressed miRNAs (DE-miRNAs) and their potential targets in the metastatic process were identified by bioinformatics analysis. Additionally, qPCR confirmed that the miR-524-5p expression was downregulated in prostate and breast cancer cells. The overexpression of miR-524-5p restrained cell proliferation, invasion, and metastasis in prostate and breast cancer cells. Meanwhile, miR-524-5p could target and inhibit the expression of MEF2C, which was verified by a luciferase assay. In conclusion, our data strongly suggest that downregulation of miR-524-5p appears to be a precocious event in prostate and breast cancer, and the miR-524-5p/MEF2C axis plays a novel role in bone metastases from prostate and breast cancers.

Comprehensive circular RNA expression profile of lung adenocarcinoma with bone metastasis: Identification of potential biomarkers

Background: Lung adenocarcinoma (LUAD) has a significant tendency to metastasize to the bone, with severe comorbidities. Recent studies have reported that circular RNAs (circRNAs) are involved in various cancer metastasis-related physiological cellular processes. However, their role in LUAD with bone metastasis (LUAD-BM) remains unknown.

Methods: Bone metastasis (BM) circRNAs were identified using high-throughput sequencing and validated by quantitative reverse transcription-PCR (qRT-PCR). Bioinformatic analyses were used to predict the potential functions of the differentially expressed circRNAs. The effects of circ_0096442 on the growth and metastasis of A549 cells were detected in a co-culture system of A549 and bone marrow-derived cells.

Results: There were 598 (238 upregulated and 360 downregulated) 390 (187 upregulated and 203 downregulated) and 644 (336 upregulated and 308 downregulated) differentially expressed circRNAs between LUAD-BM and LUAD, LUAD-BM and healthy individuals, and LUAD and healthy individuals, respectively. These differentially expressed circRNAs play important roles in cellular components, biological processes, and molecular functions. Moreover, they map several pathways related to BM, including DNA repair, DNA damage, and osteoclast differentiation. The results validated by qRT-PCR for the five most dysregulated circRNAs are consistent with the sequencing data. Additionally, circ_0096442 was found to promote the growth and metastasis of LUAD in a bone microenvironment.

Conclusion: Our findings provide a novel and important circRNA expression profile of LUAD-BM and suggest that circ_0096442 may be a biomarker for LUAD-BM.

MicroRNA-143 expression inhibits the growth and the invasion of osteosarcoma

Background

Osteosarcoma (OS) is a common malignant tumor, which occurs in the metaphysis of the long diaphysis from mesenchymal tissue. Previous studies have indicated that expression of microRNA-143 (miR-143) could affect cancer cell proliferation, migration and invasion. The present research was performed to figure out whethermiR-143 expression inhibits the growth and the invasion of OS.

Methods

We conducted a literature search in the electronic databases of Medline, Embase, Web of Science, and the Cochrane Library, SinoMed, WanFang, China national knowledge infrastructure (CNKI) until January 2022. We used Review Manager 5.3 software to conduct our research.

Results

Twelve eligible articles were included, 5 articles were reported outcomes about mice, 11 articles were reported outcomes about human. The results of mice demonstrated that the miR-143 group had significantly better results in tumor volume, tumor weight and survival rate. The results of human demonstrated that the high level of miR-143 group had significantly better results in the 3-year, 4-year, and 5-year survival rate, lung metastasis and tumor grade.

Conclusions

MiR-143 has potentially important value in the treatment and prognosis of OS. However, more reliable animal and clinical trials are needed before miR-143 based therapies can be transferred from animal studies to human applications.

The Biological Function of MicroRNAs in Bone Tumors

Micro ribonucleic acids (miRNAs) are small endogenous noncoding RNAs molecules that regulate gene expression post-transcriptionally. A single miRNA is able to target hundreds of specific messenger RNA (mRNAs) by binding to the 3′-untranslated regions. miRNAs regulate different biological processes such as cell proliferation, differentiation and apoptosis. Altered miRNA expression is certainly related to the development of the most common human diseases, including tumors. Osteosarcoma (OS), Ewing’s Sarcoma (ES), and Chondrosarcoma (CS) are the most common primary bone tumors which affect mainly children and adolescents. A significant dysregulation of miRNA expression, in particular of mir-34, mir-21, mir-106, mir-143, and miR-100, has been revealed in OS, ES and CS. In this context, miRNAs can act as either tumor suppressor genes or oncogenes, contributing to the initiation and progression of bone tumors. The in-depth study of these small molecules can thus help to better understand their biological functions in bone tumors. Therefore, this review aims to examine the potential role of miRNAs in bone tumors, especially OS, ES and CS, and to suggest their possible use as potential therapeutic targets for the treatment of bone tumors and as biomarkers for early diagnosis.

Bone Metastatic Breast Cancer: Advances in Cell Signaling and Autophagy Related Mechanisms

Bone metastasis is a frequent complication of breast cancer with nearly 70% of metastatic breast cancer patients developing bone metastasis during the course of their disease. The bone represents a dynamic microenvironment which provides a fertile soil for disseminated tumor cells, however, the mechanisms which regulate the interactions between a metastatic tumor and the bone microenvironment remain poorly understood. Recent studies indicate that during the metastatic process a bidirectional relationship between metastatic tumor cells and the bone microenvironment begins to develop. Metastatic cells display aberrant expression of genes typically reserved for skeletal development and alter the activity of resident cells within the bone microenvironment to promote tumor development, resulting in the severe bone loss. While transcriptional regulation of the metastatic process has been well established, recent findings from our and other research groups highlight the role of the autophagy and secretory pathways in interactions between resident and tumor cells during bone metastatic tumor growth. These reports show high levels of autophagy-related markers, regulatory factors of the autophagy pathway, and autophagy-mediated secretion of matrix metalloproteinases (MMP's), receptor activator of nuclear factor kappa B ligand (RANKL), parathyroid hormone related protein (PTHrP), as well as WNT5A in bone metastatic breast cancer cells. In this review, we discuss the recently elucidated mechanisms and their crosstalk with signaling pathways, and potential therapeutic targets for bone metastatic disease.

Regulation of bone metastasis and metastasis suppressors by non-coding RNAs in breast cancer

Breast cancer (BC) is a critical health care issue that substantially affects women worldwide. Though surgery and chemotherapy can effectively control tumor growth, metastasis remains a primary concern. Metastatic BC cells predominantly colonize in bone, owing to their rigid osseous nutrient-rich nature. There are recently increasing studies investigating the context-dependent roles of non-coding RNAs (ncRNAs) in metastasis regulation. ncRNAs, including microRNAs, long non-coding RNAs, circular RNAs, and small interference RNAs, control the BC metastasis via altered mechanisms. Additionally, these ncRNAs have been reported in regulating a unique class of genes known as Metastatic suppressors. Metastasis suppressors like BRMS1, NM23, LIFR, and KAI1, etc., have been extensively studied for their role in inducing apoptosis, inhibiting metastasis, and maintaining homeostasis. In this review, we have emphasized the direct regulation of ncRNAs for effectively controlling the distant spread of BC. Furthermore, we have highlighted the ncRNA-mediated modulation of the metastatic suppressors, thereby delineating their indirect influence over metastasis.

Bone-modifying Agents (BMAs) in Breast Cancer

Bone-modifying agents (BMAs) are mainstays in breast cancer and prevent and treat osteoporosis in early-stage disease and reduce skeletal metastases complications in advanced disease. There is some evidence to support that BMA also prevents skeletal metastases and improves overall survival. Bone loss occurs with chemotherapy-induced ovarian failure, gonadotrophin-releasing hormone (GnRH) agonists, and aromatase inhibitors. In some women, the bone loss will be of sufficient magnitude to increase the risks of osteoporosis or fractures. Recommended steps in osteoporosis prevention or treatment include risk factor assessment, taking adequate amounts of calcium and vitamin D3, and periodic evaluations with dual-energy x-ray absorptiometry scanning. If clinically indicated by the T-scores and fracture-risk prediction algorithms treat with oral, IV bisphosphonates or subcutaneous denosumab (DEN). Zoledronic acid (ZA) or DEN reduces skeletal metastases complications, including pathological fracture, spinal cord compression, or the necessity for radiation or surgery to bone. Also, both of these drugs have the side-effect of osteonecrosis at a similar incidence. Monthly administration of ZA or DEN is standard, but several recent randomized trials show noninferiority between ZA monthly and every 3-month ZA. Every 3-month ZA is a new standard of care. Similar trials of the schedule of DEN are ongoing. ZA anticancer effect is only in postmenopausal women or premenopausal women rendered postmenopausal by GnRH agonists or bilateral oopherectomy. High-risk women, either postmenopausal or premenopausal, receiving GnRH/oopherctomy should consider adjuvant ZA. There are insufficient data to support DEN in this setting. Herein, this narrative review covers the mechanism of action of BMA, randomized clinical trials, and adverse events, both common and rare.

Restoring Tissue Homeostasis at Metastatic Sites: A Focus on Extracellular Vesicles in Bone Metastasis

Bone is the most common site of cancer metastasis and the spread of cancer cells to the bone is associated with poor prognosis, pain, increased risk of fractures, and hypercalcemia. The bone marrow microenvironment is an attractive place for tumor dissemination, due to the dynamic network of non-malignant cells. In particular, the alteration of the bone homeostasis favors the tumor homing and the consequent osteolytic or osteoblastic lesions. Extracellular vesicles (EVs) are reported to be involved in the metastatic process, promoting tumor invasion, escape from immune surveillance, extravasation, extracellular matrix remodeling, and metastasis, but the role of EVs in bone metastases is still unclear. Current results suggest the ability of tumor derived EVs in promoting bone localization and metastasis formation, altering the physiological balance between bone destruction and new bone depositions. Moreover, EVs from the bone marrow niche may support the onset of tumor metastasis. This review summarizes recent findings on the role of EVs in the pathological alterations of homeostasis that occur during bone metastasis to show novel potential EV-based therapeutic options to inhibit metastasis formation.

Downregulation of microRNA-605 indicates poor prognosis and promotes the progression of osteosarcoma

Osteosarcoma (OS) is a type of primary bone tumor, which is one of the leading causes of cancer-related death. MicroRNA (miR)-605 has been demonstrated to act as a prognostic biomarker and therapeutic target in various cancers, such as breast cancer and non-small cell lung cancer, but its function in OS remains unclear. The aim of the present study was to investigate the prognostic value of miR-605 in patients with OS by evaluating its expression levels and to explore the biological function of miR-605 in OS progression. For this purpose, tumor tissues and adjacent normal tissues were collected from OS patients, and the expression of miR-605 in the collected tissues and OS MG63, U2OS, HOS, and SAOS-2 cell lines was detected by quantitative real-time PCR. The prognostic value of miR-605 was evaluated by Kaplan-Meier survival curves and Cox regression analysis. The effects of miR-605 on OS cell proliferation, migration and invasion were analyzed by the CCK-8 and transwell assays, respectively. The results of the present study revealed that miR-605 was significantly downregulated in OS tissues compared with adjacent normal tissues, which was associated with the clinical stage and distant metastasis of patients. Additionally, the downregulation of miR-605 predicted the poor prognosis of patients with OS and served as an independent prognostic indicator. The downregulation of miR-605 enhanced cell proliferation, migration, and invasion of OS cells, which suggested that miR-605 may be involved in the progression of OS. The findings of the present study provide a new therapeutic target for the treatment of patients with OS.

A Signature of Circulating miRNAs Associated With Fibrous Dysplasia of Bone: the mirDys Study

Fibrous dysplasia (FD) is a rare bone disease caused by activating mutations of GNAS encoding the Gsα protein, enhancing cyclic adenosine monophosphate (cAMP) production by overstimulation of adenylyl cyclase and impairing osteoblastic differentiation. The clinical presentation ranges from asymptomatic to polyostotic forms with severe disability, explained by the mosaic distribution of the GNAS mutation. Physicians have to deal with the gap of knowledge in FD pathogenesis, the absence of prognostic markers and the lack of specific treatment. The identification of specific biomarkers for FD is an important step to improve the clinical and therapeutic approaches. An epigenetic regulation driven by microRNAs (miRNAs), known as promising biomarkers in bone disease, could be involved in FD. We have sought circulating miRNAs that are differentially expressed in FD patients compared to controls and would reflect dysregulations of osteogenesis-related genes and bone disorder. The global miRNA profiling was performed using Next Generation Sequencing in patient serum collected from a discovery cohort of 20 patients (10 polyostotic and 10 monostotic) and 10 controls. From these, we selected 19 miRNAs for a miRNA validation phase from serum of 82 patients and 82 controls, using real-time qPCR. Discovery screening identified 111 miRNAs differentially expressed in patient serum, after adjusting for the false discovery rate (FDR). Among the 82 patients, 55% were polyostotic, and 73% were women with a mean age of 42 years. Six miRNAs (miR-25-3p, miR-93-5p, miR-182-5p, miR-324-5p, miR-363-3p, and miR-451a) were significantly overexpressed in serum, with FDR <0.05. The expression level of these six miRNAs was not associated with the FD severity. In conclusion, we identified a signature of circulating miRNAs associated with FD. These miRNAs are potential negative regulators of gene expression in bone cell progenitors, suggesting their activity in FD by interfering with osteoblastic and osteoclastic differentiation to impair bone mineralization and remodeling processes. © 2020 American Society for Bone and Mineral Research.

Ailanthone: A novel potential drug for treating human cancer

Cancer is the second leading cause of death after cardiovascular disease. In 2015, >8.7 million people died worldwide due to cancer, and by 2030 this figure is expected to increase to ~13.1 million. Tumor chemotherapy drugs have specific toxicity and side effects, and patients can also develop secondary drug resistance. To prevent and treat cancer, scientists have developed novel drugs with improved antitumor effects and decreased toxicity. Ailanthone (AIL) is a quassinoid extract from the traditional Chinese medicine plant Ailanthus altissima, which is known to have anti-inflammatory and antimalarial effects. An increasing number of studies have focused on AIL due to its antitumor activity. AIL can inhibit cell proliferation and induce apoptosis by up- or downregulating cancer-associated molecules, which ultimately leads to cancer cell death. Antitumor effects of AIL have been observed in melanoma, acute myeloid leukemia, bladder, lung, breast, gastric and prostate cancer and vestibular neurilemmoma. To the best of our knowledge, the present study is the first review to describe the antitumor mechanisms of AIL.

miR-29a is a potential protective factor for fibrogenesis in gluteal muscle contracture

Circulating miRNAs have been proposed as the effective diagnostic biomarkers for muscular fibrosis-associated diseases. However, circulating biomarkers for early diagnosis of contracture muscles are limited in gluteal muscle contracture (GMC) patients. Here we sought to explore the abnormally expressed miRNAs in plasma and contraction bands of GMC patients. The results showed miR-29a-3p expression in plasma and contraction bands tissue was significantly reduced in GMC patients compared with normal control. Cell viability and levels of proliferation-associated protein cyclin D1 and cyclin-dependent-kinase 2 (CDK2) were powerfully inhibited by miR-29a mimics and enhanced by miR-29a inhibitor compared with negative control. Furthermore, miR-29a mimics effectively impeded, while miR-29a inhibitor enhanced the expression of collagen I and collagen III, followed by the secretion of transforming growth factor beta1 (TGF-beta1), TGF-beta3 and connective tissue growth factor (CTGF) in primary human contraction bands (CB) fibroblasts. The miR-29a-3p negatively regulated the expression of TGF-beta1 through binding to the 3´ UTR region of SERPINH1 (encoding heat shock protein HSP47), but had no effect on Smad2 activity. The miR-29a-3p was inversely correlated with HSP47 in contraction bands tissue from GMC patients. Collectively, miR-29a was notably depressed and regulated cell viability and fibrosis by directly targeting HSP47 in GMC, which suggest that circulating miR-29a might be a potential biomarker for early diagnosis and provides a novel therapeutic target for GMC.

Inhibition of miR-9 decreases osteosarcoma cell proliferation

Osteosarcoma (OS) is the most common primary bone tumor that affects adolescents and young adults. Disruption of microRNA (miRNA) regulation is well established in the pathophysiology of different cancers, including OS. Increased expression of miR-9 in OS positively correlates with the tumor size, clinical stage, and distant metastasis. In the present study, we used two different OS cell lines, MG-63 and Saos-2, as in vitro models. miR-9 inhibitor and miR-9 mimics were used to study the function of miR-9 in these two cell lines. We determined the effect of miR-9 inhibition on cell proliferation, cell cycle, apoptosis, and the protein expression of different genes. Our results demonstrated that miR-9 inhibition in the human OS cell lines suppresses their metastatic potential, as determined by decreased cell proliferation and cell cycle arrest, decreased invasion, and increased apoptosis. The Western blot analysis showed that E-cadherin, matrix metalloproteinase 13, forkhead box O3, Bcl-2-like protein 11, and β-catenin are involved in miR-9 signaling. Moreover, miR-9 mimics rescued the effects caused by the inhibition of miR-9 in the OS cell lines. Our findings suggest that miR-9 is important for mediating OS cell migration, invasion, metastasis, and apoptosis. Inhibition of miR-9 could be further explored as a therapeutic target to treat OS.

Endometrial microRNAs and their aberrant expression patterns

MicroRNAs (miRNAs) are a class of small noncoding RNAs that regulate gene expression. They play fundamental roles in several biological processes, including cell differentiation and proliferation, embryo development, organ development, and organ metabolism. Besides regulating the physiological processes, miRNAs regulate various pathological conditions such as tumors, metastases, metabolic diseases, and osteoporosis. Although several studies have been performed on miRNAs, only few studies have described the miRNA expression and functions in human reproductive tract tissues. During menstruation, the human endometrium undergoes extensive cyclic morphological and biochemical modifications before embryo implantation. In addition to the ovarian steroid hormones (estrogen and progesterone), endometrial autocrine or paracrine factors and embryo-derived signals play a significant role in endometrial functions. miRNAs are considered key regulators of gene expression in the human endometrium and implantation process, and their aberrant expression levels are associated with the development of various disorders, including tumorigenesis. In this review, we summarize the studies that show the role of miRNAs in regulating the physiological conditions of the endometrium and the implantation process and discuss the aberrant expression of miRNAs in ectopic pregnancy, endometriosis, and endometrial cancer.

Breast cancer bone metastases are attenuated in a Tgif1-deficient bone microenvironment

Background

Osteoclast activation is a hallmark of breast cancer-induced bone disease while little is known about the role of osteoblasts in this process. Recently, we identified the homeodomain protein TG-interacting factor-1 (Tgif1) as a crucial regulator of osteoblast function. In this study, we demonstrate that lack of Tgif1 also restricts the progression of breast cancer bone metastases.

Methods

Transwell migration assays were used to investigate the osteoblast-breast cancer cell interaction in vitro. Molecular analyses included RNA sequencing, immunoblotting, and qRT-PCR. To determine the role of Tgif1 in metastatic bone disease, 4T1 breast cancer cells were injected intracardially into mice with a germ line deletion of Tgif1 (Tgif1^−/−) or control littermates (Tgif1^+/+). Progression of bone metastases and alterations in the bone microenvironment were assessed using bioluminescence imaging, immunofluorescence staining, confocal microscopy, and histomorphometry.

Results

Medium conditioned by osteoblasts stimulated breast cancer cell migration, indicating a potential role of osteoblasts during bone metastasis progression. Tgif1 expression was strongly increased in osteoblasts upon stimulation by breast cancer cells, demonstrating the implication of Tgif1 in the osteoblast-breast cancer cell interaction. Indeed, conditioned medium from osteoblasts of Tgif1^−/− mice failed to induce breast cancer cell migration compared to control, suggesting that Tgif1 in osteoblasts augments cancer cell motility. Semaphorin 3E (Sema3E), which is abundantly secreted by Tgif1^−/− osteoblasts, dose-dependently reduced breast cancer cell migration while silencing of Sema3E expression in Tgif1^−/− osteoblasts partially restored the impaired migration. In vivo, we observed a decreased number of breast cancer bone metastases in Tgif1^−/− mice compared to control littermates. Consistently, the presence of single breast cancer cells or micro-metastases in the tibiae was reduced in Tgif1^−/− mice. Breast cancer cells localized in close proximity to Endomucin-positive vascular cells as well as to osteoblasts. Although Tgif1 deficiency did not affect the bone marrow vasculature, the number and activity of osteoblasts were reduced compared to control. This suggests that the protective effect on bone metastases might be mediated by osteoblasts rather than by the bone marrow vasculature.

Conclusion

We propose that the lack of Tgif1 in osteoblasts increases Sema3E expression and attenuates breast cancer cell migration as well as metastases formation.

Therapeutic potentials and modulatory mechanisms of fatty acids in bone

Bone metabolism is a lifelong process that includes bone formation and resorption. Osteoblasts and osteoclasts are the predominant cell types associated with bone metabolism, which is facilitated by other cells such as bone marrow mesenchymal stem cells (BMMSCs), osteocytes and chondrocytes. As an important component in our daily diet, fatty acids are mainly categorized as long-chain fatty acids including polyunsaturated fatty acids (LCPUFAs), monounsaturated fatty acids (LCMUFAs), saturated fatty acids (LCSFAs), medium-/short-chain fatty acids (MCFAs/SCFAs) as well as their metabolites. Fatty acids are closely associated with bone metabolism and associated bone disorders. In this review, we summarized the important roles and potential therapeutic implications of fatty acids in multiple bone disorders, reviewed the diverse range of critical effects displayed by fatty acids on bone metabolism, and elucidated their modulatory roles and mechanisms on specific bone cell types. The evidence supporting close implications of fatty acids in bone metabolism and disorders suggests fatty acids as potential therapeutic and nutritional agents for the treatment and prevention of metabolic bone diseases.

Non-coding RNAs in bone remodelling and bone metastasis: Mechanisms of action and translational relevance

Bone metastases are frequent complications in patients with advanced cancer, which can be fatal or may rapidly impede the quality of life of patients. Current treatments for patients with bone metastases are palliative. Therefore, a better understanding of the molecular mechanisms that precede the overt development of skeletal lesions could lead to better therapeutic interventions. In this review, we present evidence that non-coding RNAs (ncRNAs) such as long ncRNAs, microRNAs, and circular RNAs are emerging as master regulators of bone metastasis formation. We highlight potential opportunities for the therapeutic targeting of ncRNAs. Furthermore, we discuss the possibility that ncRNAs may be used as biomarkers in the context of bone metastases, which might provide insight for improving the response to current bone-targeting therapies. LINKED ARTICLES: This article is part of a themed issue on The molecular pharmacology of bone and cancer-related bone diseases. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v178.9/issuetoc.