Parathyroid hormone/parathyroid hormone-related peptide regulate osteosarcoma cell functions: Focus on the extracellular matrix (Review)

Gamma-aminobutyric acid (GABA)-mediated bone formation and its implications for anti-osteoporosis strategies: Exploring the relation between GABA and GABA receptors

Osteoporosis is a significant global health concern, linked to reduced bone density and an increased fracture risk, with effective treatments still lacking. This study explored the potential of gamma-aminobutyric acid (GABA) and its receptors as a novel approach to promote osteogenesis and address osteoporosis. GABA concentrations up to 10 mM were well-tolerated by MC3T3-E1 preosteoblast, stimulating osteoblast differentiation and mineralization in a concentration- and time-dependent manner. In vivo experiments with zebrafish larvae demonstrated the ability of GABA to improve vertebral formation and enhanced bone density, indicating the potential therapeutic value for osteoporosis. Notably, GABA countered the adverse effects of prednisolone on vertebral formation, bone density, and osteogenic gene expression in zebrafish larvae, suggesting a promising therapeutic solution to counteract corticosteroid-induced osteoporosis. Moreover, our study highlighted the involvement of GABA receptors in mediating the observed osteogenic effects. By using GABAA, GABAB, and GABAC receptor antagonists, we demonstrated that blocking these receptors attenuated GABA-induced osteoblast differentiation and vertebral formation in both MC3T3-E1 cells and zebrafish larvae, underscoring the importance of GABA receptor interactions in promoting bone formation. In conclusion, these findings underscore the osteogenic potential of GABA and its ability to mitigate the detrimental effects of corticosteroids on bone health. Targeting GABA and its receptors could be a promising strategy for the development of novel therapeutic interventions to address osteoporosis. However, further investigations are warranted to fully elucidate the underlying molecular mechanism of GABA and its clinical applications in treating osteoporosis.

Multi-Anticancer Activities of Phytoestrogens in Human Osteosarcoma

Phytoestrogens are plant-derived bioactive compounds with estrogen-like properties. Their potential health benefits, especially in cancer prevention and treatment, have been a subject of considerable research in the past decade. Phytoestrogens exert their effects, at least in part, through interactions with estrogen receptors (ERs), mimicking or inhibiting the actions of natural estrogens. Recently, there has been growing interest in exploring the impact of phytoestrogens on osteosarcoma (OS), a type of bone malignancy that primarily affects children and young adults and is currently presenting limited treatment options. Considering the critical role of the estrogen/ERs axis in bone development and growth, the modulation of ERs has emerged as a highly promising approach in the treatment of OS. This review provides an extensive overview of current literature on the effects of phytoestrogens on human OS models. It delves into the multiple mechanisms through which these molecules regulate the cell cycle, apoptosis, and key pathways implicated in the growth and progression of OS, including ER signaling. Moreover, potential interactions between phytoestrogens and conventional chemotherapy agents commonly used in OS treatment will be examined. Understanding the impact of these compounds in OS holds great promise for developing novel therapeutic approaches that can augment current OS treatment modalities.

BNTA alleviates inflammatory osteolysis by the SOD mediated anti-oxidation and anti-inflammation effect on inhibiting osteoclastogenesis

Abnormal activation and overproliferation of osteoclast in inflammatory bone diseases lead to osteolysis and bone mass loss. Although current pharmacological treatments have made extensive advances, limitations still exist. N-[2-bromo-4-(phenylsulfonyl)-3-thienyl]-2-chlorobenzamide (BNTA) is an artificially synthesized molecule compound that has antioxidant and anti-inflammatory properties. In this study, we presented that BNTA can suppress intracellular ROS levels through increasing ROS scavenging enzymes SOD1 and SOD2, subsequently attenuating the MARK signaling pathway and the transcription of NFATc1, leading to the inhibition of osteoclast formation and osteolytic resorption. Moreover, the results also showed an obvious restrained effect of BNTA on RANKL-stimulated proinflammatory cytokines, which indirectly mediated osteoclastogenesis. In line with the in vitro results, BNTA protected LPS-induced severe bone loss in vivo by enhancing scavenging enzymes, reducing proinflammatory cytokines, and decreasing osteoclast formation. Taken together, all of the results demonstrate that BNTA effectively represses oxidation, regulates inflammatory activity, and inhibits osteolytic bone resorption, and it may be a potential and exploitable drug to prevent inflammatory osteolytic bone diseases.

High-specificity protection against radiation-induced bone loss by a pulsed electromagnetic field

Radiotherapy increases tumor cure and survival rates; however, radiotherapy-induced bone damage remains a common issue for which effective countermeasures are lacking, especially considering tumor recurrence risks. We report a high-specificity protection technique based on noninvasive electromagnetic field (EMF). A unique pulsed-burst EMF (PEMF) at 15 Hz and 2 mT induces notable Ca²⁺ oscillations with robust Ca²⁺ spikes in osteoblasts in contrast to other waveforms. This waveform parameter substantially inhibits radiotherapy-induced bone loss by specifically modulating osteoblasts without affecting other bone cell types or tumor cells. Mechanistically, primary cilia are identified as major PEMF sensors in osteoblasts, and the differentiated ciliary expression dominates distinct PEMF sensitivity between osteoblasts and tumor cells. PEMF-induced unique Ca²⁺ oscillations depend on interactions between ciliary polycystins-1/2 and endoplasmic reticulum, which activates the Ras/MAPK/AP-1 axis and subsequent DNA repair Ku70 transcription. Our study introduces a previously unidentified method against radiation-induced bone damage in a noninvasive, cost-effective, and highly specific manner.

NELL1 Regulates the Matrisome to Promote Osteosarcoma Progression

Sarcomas produce an abnormal extracellular matrix (ECM), which in turn provides instructive cues for cell growth and invasion. Neural EGF like-like molecule 1 (NELL1) is a secreted glycoprotein characterized by its nonneoplastic osteoinductive effects, yet it is highly expressed in skeletal sarcomas. Here, we show that genetic deletion of NELL1 markedly reduces invasive behavior across human osteosarcoma (OS) cell lines. NELL1 deletion resulted in reduced OS disease progression, inhibiting metastasis and improving survival in a xenograft mouse model. These observations were recapitulated with Nell1 conditional knockout in mouse models of p53/Rb-driven sarcomagenesis, which reduced tumor frequency and extended tumor-free survival. Transcriptomic and phosphoproteomic analyses demonstrated that NELL1 loss skews the expression of matricellular proteins associated with reduced FAK signaling. Culturing NELL1 knockout sarcoma cells on wild-type OS-enriched matricellular proteins reversed the phenotypic and signaling changes induced by NELL1 deficiency. In sarcoma patients, high expression of NELL1 correlated with decreased overall survival. These findings in mouse and human models suggest that NELL1 expression alters the sarcoma ECM, thereby modulating cellular invasive potential and prognosis. Disruption of NELL1 signaling may represent a novel therapeutic approach to short-circuit sarcoma disease progression.

SIGNIFICANCE

NELL1 modulates the sarcoma matrisome to promote tumor growth, invasion, and metastasis, identifying the matrix-associated protein as an orchestrator of cell-ECM interactions in sarcomagenesis and disease progression.

The role of SPI1-TYROBP-FCER1G network in oncogenesis and prognosis of osteosarcoma, and its association with immune infiltration

Osteosarcoma is an aggressive malignant bone sarcoma worldwide. A causal gene network with specific functions underlying both the development and progression of OS was still unclear. Here we firstly identified the differentially expressed genes (DEGs) between control and OS samples, and then defined the hub genes and top clusters in the protein–protein interaction (PPI) network of these DEGs. By focusing on the hub gene TYROBP in the top 1 cluster, a conserved TYROBP co-expression network was identified. Then the effect of the network on OS overall survival was analyzed. Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses and Gene Set Enrichment Analysis (GSEA) were used to explore the functions of the network. XCell platform and ssGSEA algorithm were conducted to estimate the status of immune infiltration. ChEA3 platform, GSEA enrichment analysis, and Drug Pair Seeker (DPS) were used to predict the key transcription factor and its upstream signal. We identified the downregulated SPI1-TYROBP-FCER1G network in OS, which were significantly enriched in immune-related functions. We also defined a two-gene signature (SPI1/FCER1G) that can predict poorer OS overall survival and the attenuated immune infiltration when downregulated. The SPI1-TYROBP-FCER1G network were potentially initiated by transcription factor SPI1 and would lead to the upregulated CD86, MHC-II, CCL4/CXCL10/CX3CL1 and hence increased immune infiltrations. With this study, we could better explore the mechanism of OS oncogenesis and metastasis for developing new therapies.

Potential of natural products in osteosarcoma treatment: Focus on molecular mechanisms

Osteosarcoma is the most frequent type of bone cancer found in children and adolescents, and commonly arises in the metaphyseal region of tubular long bones. Standard therapeutic approaches, such as surgery, chemotherapy, and radiation therapy, are used in the management of osteosarcoma. In recent years, the mortality rate of osteosarcoma has decreased due to advances in treatment methods. Today, the scientific community is investigating the use of different naturally derived active principles against various types of cancer. Natural bioactive compounds can function against cancer cells in two ways. Firstly they can act as classical cytotoxic compounds by non-specifically affecting macromolecules, such as DNA, enzymes, and microtubules, which are also expressed in normal proliferating cells, but to a greater extent by cancer cells. Secondly, they can act against oncogenic signal transduction pathways, many of which are activated in cancer cells. Some bioactive plant-derived agents are gaining increasing attention because of their anti-cancer properties. Moreover, some naturally-derived compounds can significantly promote the effectiveness of standard chemotherapy drugs, and in certain cases are able to ameliorate drug-induced adverse effects caused by chemotherapy. In the present review we summarize the effects of various naturally-occurring bioactive compounds against osteosarcoma.

miR-19 Promotes Cell Proliferation, Invasion, Migration, and EMT by Inhibiting SPRED2-mediated Autophagy in Osteosarcoma Cells

Osteosarcoma is an aggressive malignancy with rapid development and poor prognosis. microRNA-19 (miR-19) plays an important role in several biological processes. Sprouty-related EVH1 domain protein 2 (SPRED2) is a suppressor of extracellular signal-regulated kinase/mitogen-activated protein kinase (ERK/MAPK) signaling to inhibit tumor development and progression by promoting autophagy. In this study, we investigated the roles of miR-19, SPRED2, and autophagy in osteosarcoma. We detected the expression of miR-19, SPRED2, epithelial-mesenchymal transition (EMT) markers, and autophagy-related proteins via quantitative real-time polymerase chain reaction or western blot. To evaluate the function of miR-19 and SPRED2, we used MTT and colony formation assays to detect cell proliferation, Transwell, and wound-healing assays to detect cell invasion and migration. Targetscan and luciferase reporter assays confirmed the relationship between SPRED2 and miR-19. The expression of miR-19 was significantly upregulated in osteosarcoma, while SPRED2 was downregulated. miR-19 inhibitor reduced cell proliferation, invasion, migration, and EMT, while its cell biological effects were partially reversed by addition of autophagy inhibitor 3-methyladenine (3-MA) or SPRED2 siRNA in osteosarcoma. SPRED2, a suppressor of ERK/MAPK pathway that is known to trigger autophagy, was identified as a direct target of miR-19. SPRED2 overexpression increased cell proliferation, invasion, migration, and EMT by promoting autophagy, and the effects could be inhibited by 3-MA. Collectively, these findings reveal an underlying mechanism for development of osteosarcoma. miR-19 was upregulated in osteosarcoma cells, and negatively regulated SPRED2, thus promoting the malignant transformation of osteosarcoma cells via inhibiting SPRED2-induced autophagy. Therefore, miR-19/SPRED2 may be a potential target for the treatment of osteosarcoma.

Regulation of Bone Cell Differentiation and Activation by Microbe-Associated Molecular Patterns

Gut microbiota has emerged as an important regulator of bone homeostasis. In particular, the modulation of innate immunity and bone homeostasis is mediated through the interaction between microbe-associated molecular patterns (MAMPs) and the host pattern recognition receptors including Toll-like receptors and nucleotide-binding oligomerization domains. Pathogenic bacteria such as Porphyromonas gingivalis and Staphylococcus aureus tend to induce bone destruction and cause various inflammatory bone diseases including periodontal diseases, osteomyelitis, and septic arthritis. On the other hand, probiotic bacteria such as Lactobacillus and Bifidobacterium species can prevent bone loss. In addition, bacterial metabolites and various secretory molecules such as short chain fatty acids and cyclic nucleotides can also affect bone homeostasis. This review focuses on the regulation of osteoclast and osteoblast by MAMPs including cell wall components and secretory microbial molecules under in vitro and in vivo conditions. MAMPs could be used as potential molecular targets for treating bone-related diseases such as osteoporosis and periodontal diseases.

Investigation of anticancer activities of STA-9090 (ganetespib) as a second generation HSP90 inhibitor in Saos-2 osteosarcoma cells

Osteosarcoma is common childhood tumour type of the bone. Chemotherapy is the most important step in treatment of osteosarcoma. Despite advanced diagnosis methods and target specific cancer therapeutics, osteosarcoma has still a high mortality rate and a tendency to metastasize. Therefore, new therapeutic strategies are evaluated in osteosarcoma treatment in pre-clinical and clinical studies. In the last ten years, heat shock protein 90 (HSP90) has been important biological target to design target specific cancer drugs. HSP90 play vital roles in proper folding, stabilization and maintenance of oncogenic client proteins in tumorigenesis. Therefore, inhibition of HSP90 has been significant therapeutic aspects in cancer drug design. STA-9090 (ganetespib) is a second generation small molecule HSP90 inhibitor which blocks tumurogenesis in cancer cells. STA-9090 inhibited ATP hydrolysis and protein folding process of HSP90. In this study, STA-9090 decreased Saos-2 cell proliferation and IC₅₀ dose of STA-9090 was found out as 18.71 µM and 10.25 µM at 24 h and 48 h, respectively. STA-9090 inhibited HSP90 ATPase function and disrupted oncogenic client protein folding activity. Also, STA-9090 decreased protein level of the HSP90 in osteosarcoma cells. Expression analysis of osteosarcoma and bone metabolism related genes was performed by RT² Profiler PCR Array. This study has found the down-regulation of the expression levels of oncogenic genes: DKK1, TWIST1, WNT10B, WNT3A, RANK, RANKL, PTH, FGFR1, FGFR2, LTBP2, IL6, TGFβ1, MMP2 and SPARC genes, in STA-9090 treated Saso-2 cells. Furthermore, expression levels of osteosarcoma related genes, OPG, ERα, ERβ, IL15, BMP2 and BMP7, were found to have increased significantly. Biological activities of STA-9090 on Saos-2 cell line show its potential as a target specific drug to inhibit osteosarcoma and its metastasis.

PTHR1 in osteosarcoma: Specific molecular mechanisms and comprehensive functional perspective

Osteosarcoma occurs largely in children and adolescents and is the most common primary malignant tumour of bone. Although surgical advances and neoadjuvant chemotherapy have made great strides in recent years, rates of local recurrence and lung metastasis remain high, with a plateau in overall survival during the past decade. It is thus urgent to explore the pathogenesis of osteosarcoma and identify potential therapeutic targets. Parathyroid hormone receptor 1 (PTHR1) belongs to the broad family of G protein–coupled receptors, binding both parathyroid hormone (PTH) and parathyroid hormone–related peptide (PTHrP, a paracrine factor). Previous studies have shown that in tissues and cells of osteosarcoma, expression of PTHR1 is markedly increased, correlating with aggressive biologic behaviour and a poor prognosis. PTHR1 expression also correlates closely with epigenetic regulation, transcriptional regulation, post‐translational modification and protein interaction. Herein, we have summarized the latest research on the role played by PTHR1 in progression of osteosarcoma, assessing its clinical utility as a novel biomarker and its therapeutic ramifications.

Parathyroid hormone type 1 receptor regulates osteosarcoma K7M2 Cell growth by interacting with angiotensinogen

This study aimed to determine the interactions between parathyroid hormone type 1 receptor (PTHR1) and angiotensinogen (AGT) and the effects of these agents on osteosarcoma (OS). We constructed a stably transfected mouse OS K7M2 cell line (shPTHR1- K7M2) using shRNA and knocked down AGT in these cells using siRNA-AGT. The transfection efficiency and expression of AGT, chemokine C-C motif receptor 3 (CCR3), and chemokine (C-C motif) ligand 9 (CCL9) were determined using real-time quantitative PCR. Cell viability and colony formation were assessed using Cell Counting Kit-8 and crystal violet staining, respectively. Cell apoptosis and cycle phases were assessed by flow cytometry, and cell migration and invasion were evaluated using Transwell assays. Interference with PTHR1 upregulated the expression of AGT and CCR3, and downregulated that of CCL9, which was further downregulated by AGT knockdown. Cell viability, migration, invasion and colony formation were significantly decreased, while cell apoptosis was significantly increased in shPTHR1-K7M2, compared with those in K7M2 cells (P < .05 for all). However, AGT knockdown further inhibited cell viability after 72 h of culture but promoted cell migration and invasion. PTHR1 interference decreased and increased the numbers of cells in the G0/G1 and G2/M phases, respectively, compared with those in K7M2 cells. Angiotensinogen knockdown increased the number of cells in the G0/G1 phase compared with that in the shPTHR1-K7M2 cells. Therefore, PTHR1 affects cell viability, apoptosis, migration, invasion and colony formation, possibly by regulating AGT/CCL9 in OS cells.

Widespread disturbance in extracellular matrix collagen biomarker responses to teriparatide therapy in osteogenesis imperfecta

Osteogenesis imperfecta (OI), a heritable disorder caused by abnormalities in synthesis or processing of type I collagen, is characterized by skeletal fragility. Type I collagen interacts with multiple components of the extracellular matrix (ECM) including other collagens types. Thus, alterations in structure or quantity may broadly affect ECM homeostasis. In fact, while OI is clinically categorized by severity of bone disease, patients can also present with extra-skeletal manifestations, including the pulmonary, muscle and cardiovascular systems. Parathyroid hormone (PTH) is a regulator of skeletal homeostasis but the receptor for PTH/PTH1R is expressed in a variety of other tissues. Given interactions between type I collagen with other collagens in the ECM and the potential for PTH action on tissues beyond the skeleton, we explored whether serum levels of non-type I collagens are altered in response to teriparatide (human parathyroid hormone 1-34). We measured biomarkers of collagens II, III, IV, V, and VI in serum from individuals with type I and types III/IV OI in response to an 18 month course of teriparatide or placebo. These results were compared to similar biomarker measures in postmenopausal (PM) women without OI treated with teriparatide. In type I OI, teriparatide therapy increased concentrations of biomarkers of collagens II, III, IV, V, and VI. In individuals with types III/IV OI these biomarker changes in response to teriparatide were blunted, as we previously reported with collagen I biomarkers during teriparatide therapy. In contrast to OI, in PM women there were no effects of teriparatide on the collagen biomarkers we assessed (II, V, and VI). These findings suggest that in OI teriparatide therapy has abnormal effects on the homeostasis of many ECM collagens likely derived from skeletal as well as extra-skeletal tissues.

Role of PTHrP nuclear localization and carboxyl terminus sequences in postnatal spinal cord development

Parathyroid hormone-related peptide (PTHrP) acts under physiological conditions to regulate normal development of several tissues and organs. The role of PTHrP in spinal cord development has not been characterized. Pthrp knock in (Pthrp KI) mice were genetically modified to produce PTHrP in which there is a deficiency of the nuclear localization sequence (NLS) and C-terminus. Using this genetically modified mouse model, we have characterized its effect on spinal cord development early postnatally. The spinal cords from Pthrp KI mice displayed a significant reduction in its length, weight, and cross-sectional area compared to wild-type controls. Histologically, there was a decreased development of neurons and glial cells that caused decreased cell proliferation and increased apoptosis. The neural stem cells (NSCs) cultures also revealed decreased cell proliferation and differentiation and increased apoptosis. The proposed mechanism of delayed spinal cord development in Pthrp KI mice may be due to alteration in associated pathways in regulation of cell-division cycles and apoptosis. There was significant downregulation of Bmi-1 and upregulation of cyclin-dependent kinase inhibitors p27, p21, and p16 in Pthrp KI animals. We conclude that NLS and C-terminus peptide segments of PTHrP play an important role in inhibiting cell apoptosis and stimulation of cellular proliferation necessary for normal spinal cord development.

PTHR1 May Be Involved in Progression of Osteosarcoma by Regulating miR-124-3p-AR-Tgfb1i1, miR-27a-3p-PPARG-Abca1, and miR-103/590-3p-AXIN2 Axes

Our previous study has indicated that the parathyroid hormone type 1 receptor (PTHR1) may play important roles in development and progression of osteosarcoma (OS) by regulating Wnt, angiogenesis, and inflammation pathway genes. The goal of this study was to further illuminate the roles of PTHR1 in OS by investigating upstream regulation mechanisms (including microRNA [miRNA] and transcription factors [TFs]) of crucial genes. The microarray dataset GSE46861 was downloaded from the Gene Expression Omnibus database, in which six tumors with short hairpin RNA (shRNA) PTHR1 knockdown (PTHR1.358) and six tumors with shRNA control knockdown (Ren.1309) were collected from mice. Differentially expressed genes (DEGs) between PTHR1.358 and Ren.1309 were identified using the linear models for microarray data (LIMMA) method, and then the miRNA-TF-mRNA regulatory network was constructed using data from corresponding databases, followed by module analysis, to screen crucial regulatory relationships. OS-related human miRNAs were extracted from the curated Osteosarcoma Database. Gene ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways were enriched using the Database for Annotation, Visualization, and Integrated Discovery (DAVID) tool. As a result, the miRNA-TF-mRNA regulatory network, including 1049 nodes (516 miRNA, 25 TFs, and 508 DEGs) and 15942 edges (interaction relationships, such as Pparg-Abca1 and miR-590-3p-AXIN2), was constructed, from which three significant modules were extracted and modules 2 and 3 contained interactions between miRNAs/TFs and DEGs such as miR-103-3p-AXIN2, miR-124-3p-AR-Tgfb1i1, and miR-27a-3p-PPARG-Abca1. miR-27a-3p was a known miRNA associated with OS. Abca1, AR, and miR-124-3p were hub genes in the miRNA-TF-mRNA network. Tgfb1i1 was involved in cell proliferation, Abca1 participated in the cholesterol metabolic process, and AXIN2 was associated with the canonical Wnt signaling pathway. Furthermore, we also confirmed upregulation of miR-590-3p and downregulation of AXIN2 in the mouse OS cell line K7M2-WT transfected with PTHR1 shRNA. In conclusion, PTHR1 may play important roles in progression of OS by activating miR-124-3p-AR-Tgfb1i1, miR-27a-3p-PPARG-Abca1, and miR-103/590-3p-AXIN2 axes.

Advances in differentiation therapy for osteosarcoma

Differentiation therapy involves the use of agents that can induce differentiation in cancer cells, with the irreversible loss of tumour phenotype. The application of differentiation therapy in osteosarcoma has made progress because of a better understanding of the potential links between differentiation defects and tumorigenesis. Here, we review recent studies on differentiation therapy for osteosarcoma, describing a variety of differentiation inducers. By highlighting these examples of drug-induced osteosarcoma cell differentiation, we can acquire unique insights into not only osteosarcoma treatment, but also novel approaches to transform differentiating drugs into more effective therapies for other solid tumours.

Epigenetic regulation of bone remodeling by natural compounds

Osteoporosis and osteopenia impact more than 54 million Americans, resulting in significant morbidity and mortality. Alterations in bone remodeling are the hallmarks for osteoporosis, and thus the development of novel treatments that will prevent or treat bone diseases would be clinically significant, and improve the quality of life for these patients. Bone remodeling involves the removal of old bone by osteoclasts and the formation of new bone by osteoblasts. This process is tightly coupled, and is essential for the maintenance of bone strength and integrity. Since the osteoclast is the only cell capable of bone resorption, the development of drugs to treat bone disorders has primarily focused on reducing osteoclast differentiation, maturation, and bone resorption mechanisms, and there are few treatments that actually increase bone formation. Evidence from observational, experimental, and clinical studies demonstrate a positive link between naturally occurring compounds and improved indices of bone health. While many natural extracts and compounds are reported to have beneficial effects on bone, only resveratrol, sulforaphane, specific phenolic acids and anthocyanins, have been shown to both increase bone formation and reduce resorption through their effects on the bone epigenome. Each of these compounds alters specific aspects of the bone epigenome to improve osteoblast differentiation, reduce osteoblast apoptosis, improve bone mineralization, and reduce osteoclast differentiation and function. This review focuses on these specific natural compounds and their epigenetic regulation of bone remodeling.

High-resolution large-area imaging of nanoscale structure and mineralization of a sclerosing osteosarcoma in human bone

Osteosarcoma is the most common primary bone cancer type in humans. It is predominantly found in young individuals, with a second peak later in life. The tumour is formed by malignant osteoblasts and consists of collagenous, sometimes also mineralized, bone matrix. While the morphology of osteosarcoma has been well studied, there is virtually no information about the nanostructure of the tumour and changes in mineralization on the nanoscale level. In the present paper, human bone tissue inside, next to and remote from a sclerosing osteosarcoma was studied with small angle x-ray scattering, x-ray diffraction and electron microscopy. Quantitative evaluation of nanostructure parameters was combined with high resolution, large area mapping to obtain microscopic images with nanostructure parameter contrast. It was found that the tumour regions were characterized by a notable reduction in mineral particle size, while the mineral content was even higher than that in normal bone. Furthermore, the normal preferential orientation of mineral particles along the longitudinal direction of corticalis or trabeculae was largely suppressed. Also the bone mineral crystal structure was affected: severe crystal lattice distortions were detected in mineralized tumour tissue pointing to a different ion substitution of hydroxyl apatite in tumorous tissue than in healthy tissue.

RUNX family: Oncogenes or tumor suppressors (Review)

Runt-related transcription factor (RUNX) proteins belong to a transcription factors family known as master regulators of important embryonic developmental programs. In the last decade, the whole family has been implicated in the regulation of different oncogenic processes and signaling pathways associated with cancer. Furthermore, a suppressor tumor function has been also reported, suggesting the RUNX family serves key role in all different types of cancer. In this review, the known biological characteristics, specific regulatory abilities and experimental evidence of RUNX proteins will be analyzed to demonstrate their oncogenic potential and tumor suppressor abilities during oncogenic processes, suggesting their importance as biomarkers of cancer. Additionally, the importance of continuing with the molecular studies of RUNX proteins' and its dual functions in cancer will be underlined in order to apply it in the future development of specific diagnostic methods and therapies against different types of cancer.

Quercetin suppresses the proliferation and metastasis of metastatic osteosarcoma cells by inhibiting parathyroid hormone receptor 1

Osteosarcoma is an aggressive malignant neoplasm and cancerous bone tumor. Quercetin is a well-known flavonoid abundant in vegetables, fruits, grains, leaves, and red onions. In the present study, we evaluated the effects of quercetin-induced inhibition of parathyroid hormone receptor 1 (PTHR1) on proliferation, migration, and invasion in U2OS and Saos^-2 cells. Following incubation with quercetin (20, 40, 60, 80, or 100 μM) for 48 h, the cell viability of U2OS and Saos^-2 cells were significantly reduced in a dose-dependent manner. Additionally, there were significant decreases in cell adhesion, invasion, and migration as well as reduced cell viability at higher concentrations of quercetin. Furthermore, the mRNA expression levels of matrix metalloproteinases (MMP)-2 and -9 were attenuated, whereas the mRNA expression levels of tissue inhibitors of metalloproteinases (TIMP)-1 and -2 were elevated. Quercetin treatment also significantly reduced the mRNA expression levels of PTHR1 by 0.27-, and 0.55-fold at 80, and 100 μM, respectively, whereas 0.19 and 0.41 folds in Saos^-2 cells. PTHR1 protein expression in U2OS cells was reduced by 0.19-, and 0.43-fold at 80, and 100 μM of quercetin, respectively (P < 0.05), whereas 0.17 and 0.35 folds in Saos-2 cells. Immunofluorescence analyses revealed reduced expression of PTHR1 following treatment with quercetin. PTHR1 expression in U2OS cells was reduced by 0.18-, and 0.41-fold at 80, and 100 μM, respectively, whereas 0.15 and 0.38 folds in Saos^-2 cells. The knockdown of PTHR1enhanced quercetin-inhibited proliferation and invasion. Taken together, the present findings indicate that quercetin reduced human metastatic osteosarcoma cell invasion, adhesion, proliferation, and migration by inhibiting PTHR1.

The long noncoding RNA lnc-ob1 facilitates bone formation by upregulating Osterix in osteoblasts

Long noncoding RNAs (lncRNAs) have emerged as integral regulators of physiology and disease, but specific roles of lncRNAs in bone disease remain largely unknown. Here, we show that lnc-ob1 regulates osteoblast activity and bone formation in mice by upregulating the osteogenic transcription factor Osterix. Expression of lnc-ob1 is enriched in osteoblasts and upregulated during osteoblastogenesis. We demonstrate that osteoblast-specific knock-in of lnc-ob1 enhances bone formation and increases bone mass. Pharmacological overexpression of lnc-ob1 specifically in osteoblasts confers resistance to ovariectomy-induced osteoporosis in mice. In humans, expression of the homologue, lnc-OB1, decreases with age in osteoblasts of patients with osteoporosis. Mechanistically, lnc-ob1 upregulates the expression of Osterix in mouse and human osteoblasts, probably via inhibition of H3K27me3 methylation. Our data indicate that lnc-OB1 regulates bone formation and might be a drug target for the treatment of osteoporosis.

PTHrP treatment of colon cancer cells promotes tumor associated-angiogenesis by the effect of VEGF

We showed that Parathyroid Hormone-related Peptide (PTHrP) induces proliferation, migration, survival and chemoresistance via MAPKs and PI3K/AKT pathways in colorectal cancer (CRC) cells. The objective of this study was to investigate if PTHrP is also involved in tumor angiogenesis. PTHrP increased VEGF expression and the number of structures with characteristics of neoformed vessels in xenografts tumor. Also, PTHrP increased mRNA levels of VEGF, HIF-1α and MMP-9 via ERK1/2 and PI3K/Akt pathways in Caco-2 and HCT116 cells. Tumor conditioned media (TCMs) from both cell lines treated with PTHrP increases the number of cells, the migration and the tube formation in the endothelial HMEC-1 cells, whereas the neutralizing antibody against VEGF diminished this response. In contrast, PTHrP by direct treatment only increased ERK1/2 phosphorylation and the HMEC-1 cells number. These results provide the first evidence related to the mode of action of PTHrP that leads to its proangiogenic effects in the CRC.

Long Noncoding RNA SNHG16 Promotes Osteosarcoma Cells Migration and Invasion via Sponging miRNA-340

Long noncoding RNA host gene 16 (SNHG16) has a key role in a variety of cancer progression. However, the role and mechanism of SNHG16 in osteosarcoma (OS) remain unknown. In this study, we examined the functional role of SNHG16 in OS cells through knocked-down SNHG16 by using siRNA. We found that SNHG16 is overexpressed in OS tissues and cell lines. Inhibition of SNHG16 reduced OS cells proliferation, stimulated apoptosis, and decreased migration and invasion. In addition, SNHG16 reduced miR-340 expression in OS cells. The results showed that SNHG16 involves in the migration and invasion of OS cells through sponging miRNA-340. Together, our data support an important role of SNHG16 in regulating OS cell invasion and migration that highlights SNHG16 may be regarded as a potential target for OS treatment.

Biglycan Regulates MG63 Osteosarcoma Cell Growth Through a LPR6/β-Catenin/IGFR-IR Signaling Axis

Biglycan, a small leucine rich proteoglycan (SLRP), is an important participant in bone homeostasis and development as well as in bone pathology. In the present study biglycan was identified as a positive regulator of MG63 osteosarcoma cell growth (p ≤ 0.001). IGF-I was shown to increase biglycan expression (p ≤ 0.01), whereas biglycan-deficiency attenuated significantly both basal and IGF-I induced cell proliferation of MG63 cells (p ≤ 0.001; p ≤ 0.01, respectively). These effects were executed through the IGF-IR receptor whose activation was strongly attenuated (p ≤ 0.01) in biglycan-deficient MG63 cells. Biglycan, previously shown to regulate Wnt/β-catenin pathway, was demonstrated to induce a significant increase in β-catenin protein expression evident at cytoplasmic (p ≤ 0.01), membrane (p ≤ 0.01), and nucleus fractions in MG63 cells (p ≤ 0.05). As demonstrated by immunofluorescence, increase in β-catenin expression is attributed to co-localization of biglycan with the Wnt co-receptor low-density lipoprotein receptor-related protein 6 (LRP6) resulting in attenuated β-catenin degradation. Furthermore, applying anti-β-catenin and anti-pIGF-IR antibodies to MG-63 cells demonstrated a cytoplasmic and to the membrane interaction between these molecules that increased upon exogenous biglycan treatment. In parallel, the downregulation of biglycan significantly inhibited both basal and IGF-I-dependent ERK1/2 activation, (p ≤ 0.001). In summary, we report a novel mechanism where biglycan through a LRP6/β-catenin/IGF-IR signaling axis enhances osteosarcoma cell growth.

miR-27a-3p promotes the malignant phenotypes of osteosarcoma by targeting ten-eleven translocation 1

Osteosarcoma has become one of the most common primary malignant tumors affecting children and adolescents. Although increasing evidence has indicated that microRNAs (miRNAs or miRs) play important roles in the development of osteosarcoma, the expression of miR‑27a‑3p and its effects on osteosarcoma are not yet fully understood. In the present study, our data demonstrated that the expression of miR‑27a‑3p in osteosarcoma cell lines was significantly higher than that in the normal human osteoblastic cell line, hFOB 1.19 cell (P<0.01). In order to explore the role of miR‑27a‑3p in the development and progression of osteosarcoma, the expression of miR‑27a‑3p was inhibited by transfection of the MG-63 cells with miR‑27a‑3p inhibitor. The results revealed that the cell proliferative ability significantly decreased (P<0.01), the number of apoptotic cells significantly increased (P<0.01) and the number of cells passing through the Transwell membrane was significantly reduced in the group transfected with the miR‑27a‑3p inhibitor (P<0.01). At the same time, the expression of E-cadherin and α-catenin was significantly upregulated (P<0.01), while the expression of vimentin was significantly downregulated in the group transfected with the miR‑27a‑3p inhibitor (P<0.01). Our results also revealed that the mRNA expression of ten-eleven translocation 1 (TET1) in the osteosarcoma cells was significantly downregulated compared with that in the hFOB 1.19 cells (P<0.01). Luciferase reporter system analysis indicated that miR‑27a‑3p recognized the TET1 3'-UTR. The protein expression of TET1 significantly increased in the group transfected with the miR‑27a‑3p inhibitor. The results from CCK-8 assay, flow cytometric assay and Transwell invasion analysis revealed that TET1 knockdown inhibited the biological effects induced by the downregulation of miR‑27a‑3p. Taken together, the findings of this study indicate that miR‑27a‑3p is upregulated, while TET1 is downregulated in human osteosarcoma cells. miR‑27a‑3p inhibition suppresses the proliferation and invasion of osteosarcoma cells, and promotes cell apoptosis via the negative regulation of TET1. miR‑27a‑3p/TET1 may thus be a potential target for the treatment of osteosarcoma.

β-Alanine mediated inhibition of PTHR1suppresses the proliferation, invasion and tumorigenesis in metastatic human osteosarcoma U2OS cells

The present study was aimed to investigate the effect of β-alanine mediated inhibition of parathyroid hormone 1 receptor (PTHR1), suppresses the proliferation, invasion, and tumorigenesis in metastatic human osteosarcoma U2OS cells. Cell survival rate was reduced 96.54, 91.23, 84.62, 76.42 and 69.72% following incubation of β-alanine at 50-250 mM respectively. Annexin-V/propidium iodide (PI) staining showed a reduced level of viable cells (71.37%) at 250 mM of β-alanine. U2OS cell proliferation, adhesion, invasion, and migration were decreased following incubation with β-alanine. Matrix metalloproteinases-2/9 (MMP-2/9) mRNA expression was reduced, whereas tissue inhibitors of metalloproteinases-1/2 (TIMP-1/2) mRNA expression was increased remarkably. The mRNA and protein of PTHR1 were reduced in the cells following incubation with β-alanine. Vacuole membrane protein 1 (Vmp1) mRNA and protein were increased in the cells following incubation with β-alanine. In tunel assay, the number of PTHR1 positive cells was 67, 34 and 17 following incubation with β-alanine at 150, 200 and 250 mM respectively. Taking all these data together, it is concluded that β-alanine mediated inhibition of PTHR1 reduced the U2OS cell proliferation, invasion, migration, and tumorigenesis. Furthermore, the results indicated that the β-alanine induced expression of PTHR1 has a positive relationship with invasion and metastasis of osteosarcoma cells.

MicroRNA-19 contributes to the malignant phenotypes of osteosarcoma in vitro by targeting Pax6

This study was conducted to detect the expression of miR-19 and Pax6 (Paired box protein 6) in human osteosarcoma cells and the effects on biological characteristics of osteosarcoma cells. Quantitative real-time polymerase chain reaction was used to detect the expression of Pax6 and miR-19 in normal human osteoblasts (hFOB 1.19) and osteosarcoma cell lines (U2OS, Saos-2, and MG-63). Results showed that miR-19 was significantly upregulated in osteosarcoma cell lines compared with that in hFOB 1.19 cells, while the expression of Pax6 messenger RNA was significantly downregulated. Pax6 was defined as the target gene of miR-19 which was validated by luciferase reporter gene analysis. Results indicated that miR-19 had an interaction with Pax6 3'-untranslated region. At the same time, the protein expression of Pax6 was significantly decreased in the MG-63 cells transfected with miR-19 mimic and was notably enhanced in osteosarcoma MG-63 cells transfected with miR-19 inhibitor. These data suggested that Pax6 was a target of miR-19 in osteosarcoma MG-63 cells. The effects of miR-19 on the biological behavior of MG-63 cells were determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, flow cytometry, and Transwell assay. Results showed that the downregulation of miR-19 inhibited cell viability, reduced the percentage of cells in S phase and the number of cells passing through the Transwell chamber, and increased the number of apoptotic cells. Western blot analysis showed that the inhibition of miR-19 significantly increased the expression of epithelial proteins (E-cadherin and β-catenin) and decreased the expression of mesenchymal protein (Vimentin), extracellular signal-regulated kinase, and phosphorylated extracellular signal-regulated kinase in MG-63 cells. MiR-19 inhibitor and Pax6 small interfering RNA were simultaneously transfected into MG-63 cells. Results from 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, flow cytometry, and Transwell assay demonstrated that the inhibition of Pax6 expression in MG-63 cells could reverse the cell biological effects induced by the inhibition of miR-19 expression. Based on these findings, it was suggested that miR-19, upregulated in osteosarcoma cells, negatively regulated the expression of Pax6, which can promote the malignant phenotypes of osteosarcoma cells via activation of the extracellular signal-regulated kinase signaling pathways. Therefore, miR-19/Pax6 may offer potential for use as a target for the treatment of osteosarcoma.

Parathyroid Hormone-Related Protein Promotes Rat Stem Leydig Cell Differentiation

The regulatory factors for stem Leydig cell development are largely unknown. Herein, we reported that parathyroid hormone-related protein (PTHrP) may be a factor to regulate this process. The effects of PTHrP on rat stem Leydig cell proliferation and differentiation were investigated using a stem Leydig cell culture system and an ethane dimethane sulfonate (EDS)-treated in vivo Leydig cell regeneration model. PTHrP (1,000 pg/ml) significantly increased medium testosterone level and up-regulated STAR, CYP17A1, and 17β-HSD3 expressions. Co-treatment with PKA inhibitor H-89 or PKC inhibitor U73122 reversed PTHrP-mediated increase of testosterone production in vitro. Intratesticular injection of PTHrP (100 ng/testis) into the Leydig cell-depleted testis from post-EDS day 7 to 21 significantly increased serum testosterone level, up-regulated LHCGR, SCARB1, CYP11A1, 11β-HSD1, and CYP17A1 expressions. It also enlarged Leydig cell size without affecting PCNA-labeled Leydig cell number. This indicates that PTHrP promotes stem Leydig cell differentiation. PTHrP in vivo increased CREB and p-CREB levels, suggesting that PTHrP acts via a PKA-CREB signaling pathway. In conclusion, PTHrP stimulates stem Leydig cell differentiation without affecting its proliferation, showing its novel action and mechanism on rat stem Leydig cell development.

Transcriptomic analyses reveal the underlying pro-malignant functions of PTHR1 for osteosarcoma via activation of Wnt and angiogenesis pathways

BACKGROUND

Increasing evidence has indicated parathyroid hormone type 1 receptor (PTHR1) plays important roles for the development and progression of osteosarcoma (OS). However, its function mechanisms remain unclear. The goal of this study was to further illuminate the roles of PTHR1 in OS using microarray data.

METHODS

Microarray data were available from the Gene Expression Omnibus database under the accession number GSE46861, including six tumors from mice with PTHR1 knockdown (PTHR1.358) and six tumors from mice with control knockdown (Ren.1309). Differentially expressed genes (DEGs) between PTHR1.358 and Ren.1309 were identified using the LIMMA method, and then, protein-protein interaction (PPI) network was constructed using data from STRING database to screen crucial genes associated with PTHR1. KEGG pathway enrichment analysis was performed to investigate the underlying functions of DEGs using DAVID tool.

RESULTS

A total of 1163 genes were identified as DEGs, including 617 downregulated (Lef1, lymphoid enhancer-binding factor 1) and 546 upregulated genes (Dkk1, Dickkopf-related protein 1). KEGG enrichment analysis indicated upregulated DEGs were involved in Renin-angiotensin system (e.g., Agt, angiotensinogen) and Wnt signaling pathway (e.g., Dkk1), while downregulated DEGs participated in Basal cell carcinoma (e.g., Lef1). A PPI network (534 nodes and 2830 edges) was constructed, in which Agt gene was demonstrated to be the hub gene and its interactive genes (e.g., CCR3, CC chemokine receptor 3; and CCL9, chemokine CC chemokine ligand 9) were inflammation related.

CONCLUSIONS

Our present study preliminarily reveals the pro-malignant effects of PTHR1 in OS cells may be mediated by activating Wnt, angiogenesis, and inflammation pathways via changing the expressions of the crucial enriched genes (Dkk1, Lef1, Agt-CCR3, and Agt-CCL9).