MAPK/ERK Signaling in Osteosarcomas, Ewing Sarcomas and Chondrosarcomas: Therapeutic Implications and Future Directions

MTA2 knockdown suppresses human osteosarcoma metastasis by inhibiting uPA expression

The relationship between metastasis-associated protein 2 (MTA2) overexpression and tumor growth and metastasis has been extensively studied in a variety of tumor cells but not in human osteosarcoma cells. This study aims to elucidate the clinical significance, underlying molecular mechanisms, and biological functions of MTA2 in human osteosarcoma in vitro and in vivo. Our results show that MTA2 was elevated in osteosarcoma cell lines and osteosarcoma tissues and was associated with tumor stage and overall survival of osteosarcoma patients. Knockdown of MTA2 inhibited osteosarcoma cell migration and invasion by reducing the expression of urokinase-type plasminogen activator (uPA). Bioinformatic analysis demonstrated that high levels of uPA in human osteosarcoma tissues correlated positively with MTA2 expression. Furthermore, treatment with recombinant human uPA (Rh-uPA) caused significant restoration of OS cell migration and invasion in MTA2 knockdown osteosarcoma cells. We found that ERK1/2 depletion increased the expression of uPA, facilitating osteosarcoma cell migration and invasion. Finally, MTA2 depletion significantly reduced tumor metastasis and the formation of lung nodules in vivo. Overall, our study suggests that MTA2 knockdown suppresses osteosarcoma cell metastasis by decreasing uPA expression via ERK signaling. This finding provides new insight into potential treatment strategies against osteosarcoma metastasis by targeting MTA2.

Amicis Omnia Sunt Communia: NF-κB Inhibition as an Alternative to Overcome Osteosarcoma Heterogeneity

Tumor heterogeneity poses a significant challenge in osteosarcoma (OS) treatment. In this regard, the "omics" era has constantly expanded our understanding of biomarkers and altered signaling pathways (i.e., PI3K/AKT/mTOR, WNT/β-catenin, NOTCH, SHH/GLI, among others) involved in OS pathophysiology. Despite different players and complexities, many commonalities have been described, among which the nuclear factor kappa B (NF-κB) stands out. Its altered activation is pervasive in cancer, with pleiotropic action on many disease-relevant traits. Thus, in the scope of this article, we highlight the evidence of NF-κB dysregulation in OS and its integration with other cancer-related pathways while we summarize the repertoire of compounds that have been described to interfere with its action. In silico strategies were used to demonstrate that NF-κB is closely coordinated with other commonly dysregulated signaling pathways not only by functionally interacting with several of their members but also by actively participating in the regulation of their transcription. While existing inhibitors lack selectivity or act indirectly, the therapeutic potential of targeting NF-κB is indisputable, first for its multifunctionality on most cancer hallmarks, and secondly, because, as a common downstream effector of the many dysregulated pathways influencing OS aggressiveness, it turns complex regulatory networks into a simpler picture underneath molecular heterogeneity.

Exploring the logic and conducting a comprehensive evaluation of AdipoRon-based adiponectin replacement therapy against hormone-related cancers-a systematic review

The potential benefits of adiponectin replacement therapy extend to numerous human diseases, with current research showing particular interest in its effectiveness against specific cancer forms, especially hormone-related. However, limitations in the pharmacological use of the intact protein have led to a focus on alternative options. AdipoRon is an extensively studied non-peptidic drug candidate for adiponectin replacement therapy. While researchers have explored the efficacy and therapeutic applications of AdipoRon in various disease conditions, their effects against cancer models advanced more, with no review regarding AdipoRon's efficacy against hormone-related cancers being published. The present systematic review aims to fill this gap. Preclinical evidence was compiled from PubMed, EMBASE, COCHRANE, and Google Scholar following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, and the manuscript's quality assessment was conducted using the Joanna Briggs Institute (JBI) Checklist Critical Appraisal Tool for Systematic Reviews' Quality. The included nine studies incorporated various cell and animal models of the pancreas, gynaecological system, and osteosarcoma cancers. AdipoRon demonstrated effectiveness against pancreatic cancer by activating p44/42 MAPK, mitochondrial dysfunction, and AMPK-mediated inhibition of ACC1. In gynaecological cancers, it exhibited promising anticancer effects through the activation of AMPK, potential inhibition of mTOR, and modulation of the SET1B/BOD1/AdipoR1 signaling cascade. Against osteosarcoma, AdipoRon worked by perturbing ERK1/2 signaling and reducing p70S6K phosphorylation. AdipoRon shows promise in preclinical studies, but human trials are crucial for clinical safety and effectiveness. Caution is needed due to potential off-target effects, especially in cancer therapy with multi-target approaches. Structural biology and computational methods can help predict these effects.

PD-L1, STAT3, IL6, and EGFR Immunoexpressions in High-Grade Osteosarcoma

Introduction

Immunotherapy has been widely used in the treatment of various malignancies with satisfactory results. One of the agents for immunotherapy is an inhibitor of programmed cell death-1 and its ligands (PD-1 and PD-L1). However, attempts at utilizing PD-1/PD-L1 immunotherapy in osteosarcoma have not yielded favorable results. This may be due to differences in PD-L1 regulation and the immune landscape in osteosarcoma, as the mechanism is still poorly understood. Therefore, elucidating PD-L1 regulation in osteosarcoma is paramount in order to improve treatment results using immunotherapy.

Methods

This is a cross-sectional study conducted in the Department of Anatomical Pathology of Saiful Anwar Hospital using 33 paraffin blocks of confirmed cases of osteosarcoma. Immunohistochemical staining using PD-L1, STAT3, IL6, and EGFR was performed. Statistical analyses were subsequently performed on the immunoexpression data of these antibodies.

Results

PD-L1, STAT3, IL6, and EGFR expressions were found in 6 (18.2%), 6 (18.2%), 28 (84.8%), and 30 (90.9%) cases, respectively. There were significant correlations between PD-L1 and STAT3 (r = 0.620, p=<0.001), PD-L1 and EGFR (r = 0.449, p=0.009), as well as STAT3 and EGFR (r = 0.351, p=0.045).

Conclusion

The existence of a correlation between PD-L1, STAT3, and EGFR indicates the potential role of STAT3 and EGFR in PD-L1 regulation in osteosarcoma, which may become the basis for targeted therapy.

Unveiling the Protective Role of Melatonin in Osteosarcoma: Current Knowledge and Limitations

Melatonin, an endogenous neurohormone produced by the pineal gland, has received increased interest due to its potential anti-cancer properties. Apart from its well-known role in the sleep-wake cycle, extensive scientific evidence has shown its role in various physiological and pathological processes, such as inflammation. Additionally, melatonin has demonstrated promising potential as an anti-cancer agent as its function includes inhibition of tumorigenesis, induction of apoptosis, and regulation of anti-tumor immune response. Although a precise pathophysiological mechanism is yet to be established, several pathways related to the regulation of cell cycle progression, DNA repair mechanisms, and antioxidant activity have been implicated in the anti-neoplastic potential of melatonin. In the current manuscript, we focus on the potential anti-cancer properties of melatonin and its use in treating and managing pediatric osteosarcoma. This aggressive bone tumor primarily affects children and adolescents and is treated mainly by surgical and radio-oncological interventions, which has improved survival rates among affected individuals. Significant disadvantages to these interventions include disease recurrence, therapy-related toxicity, and severe/debilitating side effects that the patients have to endure, significantly affecting their quality of life. Melatonin has therapeutic effects when used for treating osteosarcoma, attributed to its ability to halt cancer cell proliferation and trigger apoptotic cell death, thereby enhancing chemotherapeutic efficacy. Furthermore, the antioxidative function of melatonin alleviates harmful side effects of chemotherapy-induced oxidative damage, aiding in decreasing therapeutic toxicities. The review concisely explains the many mechanisms by which melatonin targets osteosarcoma, as evidenced by significant results from several in vitro and animal models. Nevertheless, if further explored, human trials remain a challenge that could shed light and support its utility as an adjunctive therapeutic modality for treating osteosarcoma.

Novel combination of imipridones and histone deacetylase inhibitors demonstrate cytotoxic effect through integrated stress response in pediatric solid tumors

There is a demonstrated need for new chemotherapy options in pediatric oncology, as pediatric solid tumors continue to plateau at 60% with event-free survival. Imipridones, a novel class of small molecules, represent a potential new therapeutic option, with promising pre-clinical data and emerging clinical trial data in adult malignancies. ONC201, ONC206, and ONC212 are imipridones showing pro-apoptotic anti-cancer response. Using cell viability assays, and protein immunoblotting, we were able to demonstrate single-agent efficacy of all 3 imipridones inducing cell death in pediatric solid tumor cell lines, including osteosarcoma, malignant peripheral nerve sheath tumors, Ewing sarcoma (EWS), and neuroblastoma. ONC201 displayed IC50 values for non-H3K27M-mutated EWS cell lines ranging from 0.86 µM (SK-N-MC) to 2.76 µM (RD-ES), which were comparable to the range of IC50 values for H3K27M-mutated DIPG cells lines (range 1.06 to 1.56 µM). ONC212 demonstrated the highest potency in single-agent cell killing, followed by ONC206, and ONC201. Additionally, pediatric solid tumor cells were treated with single-agent therapy with histone deacetylase inhibitors (HDACi) vorinostat, entinostat, and panobinostat, showing cell killing with all 3 HDACi drugs, with panobinostat showing the greatest potency. We demonstrate that dual-agent therapy with combinations of imipridones and HDACi lead to synergistic cell killing and apoptosis in all pediatric solid tumor cell lines tested, with ONC212 and panobinostat combinations demonstrating maximal potency. The imipridones induced the integrated stress response with ATF4 and TRAIL receptor upregulation, as well as reduced expression of ClpX. Hyperacetylation of H3K27 was associated with synergistic killing of tumor cells following exposure to imipridone plus HDAC inhibitor therapies. Our results introduce a novel class of small molecules to treat pediatric solid tumors in a precision medicine framework. Use of impridones in pediatric oncology is novel and shows promising pre-clinical efficacy in pediatric solid tumors, including in combination with HDAC inhibitors.

MiR-4270 acts as a tumor suppressor by directly targeting Bcl-xL in human osteosarcoma cells

Chondrosarcomas and osteosarcomas are malignant bone tumors with a poor prognosis when unresectable or metastasized. Moreover, radiotherapy and chemotherapy could be ineffective. MiRNAs represent an alternative therapeutic approach. Based on high-throughput functional screening, we identified four miRNAs with a potential antiproliferative effect on SW1353 chondrosarcoma cells. Individual functional validations were then performed in SW1353 cells, as well as in three osteosarcoma cell lines. The antiproliferative and cytotoxic effects of miRNAs were evaluated in comparison with a positive control, miR-342-5p. The cytotoxic effect of four selected miRNAs was not confirmed on SW1353 cells, but we unambiguously revealed that miR-4270 had a potent cytotoxic effect on HOS and MG-63 osteosarcoma cell lines, but not on SaOS-2 cell line. Furthermore, like miR-342-5p, miR-4270 induced apoptosis in these two cell lines. In addition, we provided the first report of Bcl-xL as a direct target of miR-4270. MiR-4270 also decreased the expression of the anti-apoptotic protein Mcl-1, and increased the expression of the pro-apoptotic protein Bak. Our findings demonstrated that miR-4270 has tumor suppressive activity in osteosarcoma cells, particularly through Bcl-xL downregulation.

Anti-tumor effects of deubiquitinating enzyme inhibitor PR-619 in human chondrosarcoma through reduced cell proliferation and endoplasmic reticulum stress-related apoptosis

Chondrosarcoma, a treatment-resistant cancer with limited therapeutic options, lacks significant advancements in treatment methods. However, PR-619, a novel inhibitor of deubiquitinating enzymes, has demonstrated anti-tumor effects in various malignancies. This study aimed to investigate the impact of PR-619 on chondrosarcoma both in vitro and in vivo. Two human chondrosarcoma cell lines, SW11353 and JJ012, were utilized. Cell viability was assessed using an MTT assay, while flow cytometry enabled the detection of apoptosis and cell cycle progression. Western blotting analyses were conducted to evaluate apoptosis, cell stress, and endoplasmic reticulum (ER) stress. Furthermore, the in vivo anti-tumor effects of PR-619 were examined using a xenograft mouse model. The results revealed that PR-619 induced cytotoxicity, apoptosis, and cell cycle arrest at the G0/G1 stage by activating caspases, PARP cleavage, and p21. Moreover, PR-619 increased the accumulation of polyubiquitinated proteins and ER stress by activating IRE1, GRP78, caspase-4, CHOP, and other cellular stress responses, including JNK activation. In vivo analysis demonstrated that PR-619 effectively inhibited tumor growth with minimal toxicity in the xenograft mouse model. These findings provide evidence of the anti-tumor effects and induction of cellular and ER stress by PR-619 in human chondrosarcoma, suggesting its potential as a novel therapeutic strategy for in human chondrosarcoma.

Targeted long-read sequencing of the Ewing sarcoma 6p25.1 susceptibility locus identifies germline-somatic interactions with EWSR1-FLI1 binding

Ewing sarcoma (EwS) is a rare bone and soft tissue malignancy driven by chromosomal translocations encoding chimeric transcription factors, such as EWSR1-FLI1, that bind GGAA motifs forming novel enhancers that alter nearby expression. We propose that germline microsatellite variation at the 6p25.1 EwS susceptibility locus could impact downstream gene expression and EwS biology. We performed targeted long-read sequencing of EwS blood DNA to characterize variation and genomic features important for EWSR1-FLI1 binding. We identified 50 microsatellite alleles at 6p25.1 and observed that EwS-affected individuals had longer alleles (>135 bp) with more GGAA repeats. The 6p25.1 GGAA microsatellite showed chromatin features of an EWSR1-FLI1 enhancer and regulated expression of RREB1, a transcription factor associated with RAS/MAPK signaling. RREB1 knockdown reduced proliferation and clonogenic potential and reduced expression of cell cycle and DNA replication genes. Our integrative analysis at 6p25.1 details increased binding of longer GGAA microsatellite alleles with acquired EWSR-FLI1 to promote Ewing sarcomagenesis by RREB1-mediated proliferation.

Ursonic acid inhibits migration and invasion of human osteosarcoma cells through the suppression of mitogen-activated protein kinases and matrix metalloproteinases

INTRODUCTION

Osteosarcoma (OS) is the most common form of bone malignancy. Although contemporary chemotherapy and surgery have improved the prognosis of those with OS, developing new OS therapies has proven difficult for some time. The activation of the matrix metalloproteinase (MMP) and mitogen-activated protein kinase (MAPK) signaling pathways can induce metastasis, which is an obstacle to OS treatment. Ursonic acid (UNA) is a phytochemical with the potential to cure a variety of human ailments, including cancer.

METHODS AND RESULTS

In this study, we investigated the anti-tumor properties of UNA in MG63 cells. We conducted colony formation assay, wound healing assay, and Boyden chamber assays to investigate the anti-OS effects of UNA. UNA was found to significantly inhibit the proliferative, migratory, and invasive abilities of MG63 cells. This bioactivity of UNA was mediated by the inhibition of extracellular signal-regulated kinase (ERK) and p38 and reduction of MMP-2 transcriptional expression as observed in western blot analysis, gelatin zymography and RT-PCR. Anti-OS activities of UNA were also observed in Saos2 and U2OS cells, indicating that its anti-cancer properties are not specific to cell types.

CONCLUSION

Our findings suggest that UNA has the potential for use in anti-metastatic drugs in the treatment of OS.

Anti-inflammatory activity of Echinosophora koreensis nakai root extract in lipopolysaccharides-stimulated RAW 264.7 cells and carrageenan-induced mouse paw edema model

ETHNOPHARMACOLOGICAL RELEVANCE

Echinosophora koreensis Nakai is an endemic plant species distributed in a limited area within the Korean province of Gangwon, including the Yanggu-gun, Inje-gun, Cheorwon-gun, Chuncheon-si, and Hongcheon-gun counties. It is used in traditional medicine to treat various disorders, such as fever, skin diseases, diuresis, and neuralgia.

MATERIALS AND METHODS

This study demonstrated the effects of E. koreensis Nakai root extract (EKRE) on lipopolysaccharide (LPS)-induced inflammatory responses in vitro and in vivo. Cell viability was assessed through a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Nitric oxide (NO) production was measured using Griess reagent. Interleukin (IL)-6 and tumor necrosis factor (TNF) levels were assessed using enzyme-linked immunosorbent assays. Inducible nitric oxide synthase (iNOS), nuclear factor kappa-B (NF-κB), and mitogen-activated protein kinase (MAPK) expression were assessed using Western blot analysis. To examine the effects of EKRE in vivo, it was administered orally at doses of 50 or 200 mg/kg for 3 days in mice. Edema in the paws was induced through λ-carrageenan injection and measured hourly for up to 5 h using calipers.

RESULTS

EKRE markedly suppressed LPS-generated NO, IL-6, and iNOS production in RAW 264.7 cells. Moreover, it suppressed the activation of the NF-κB and MAPK in LPS-stimulated cells. Furthermore, EKRE significantly inhibited carrageenan-induced edema in mouse paws. There were no significant differences in IL-6 and TNF production in paw tissue harvested from mice, but levels decreased at high EKRE concentrations (200 mg/kg).

CONCLUSION

The results of this study provided validation for EKRE-induced inhibition of inflammatory responses in vitro and in vivo. This research suggested that EKRE is a promising treatment for inflammatory disorders.

Nuclear receptor modulators inhibit osteosarcoma cell proliferation and tumour growth by regulating the mTOR signaling pathway

Osteosarcoma is the most common primary malignant bone tumour in children and adolescents. Chemoresistance leads to poor responses to conventional therapy in patients with osteosarcoma. The discovery of novel effective therapeutic targets and drugs is still the main focus of osteosarcoma research. Nuclear receptors (NRs) have shown substantial promise as novel therapeutic targets for various cancers. In the present study, we performed a drug screen using 29 chemicals that specifically target 17 NRs in several different human osteosarcoma and osteoblast cell lines. The retinoic acid receptor beta (RARb) antagonist LE135, peroxisome proliferator activated receptor gamma (PPARg) antagonist T0070907, liver X receptor (LXR) agonist T0901317 and Rev-Erba agonist SR9011 significantly inhibited the proliferation of malignant osteosarcoma cells (U2OS, HOS-MNNG and Saos-2 cells) but did not inhibit the growth of normal osteoblasts. The effects of these NR modulators on osteosarcoma cells occurred in a dose-dependent manner and were not observed in NR-knockout osteosarcoma cells. These NR modulators also significantly inhibited osteosarcoma growth in vivo and enhanced the antitumour effect of doxorubicin (DOX). Transcriptomic and immunoblotting results showed that these NR modulators may inhibit the growth of osteosarcoma cells by regulating the PI3K/AKT/mTOR and ERK/mTOR pathways. DDIT4, which blocks mTOR activation, was identified as one of the common downstream target genes of these NRs. DDIT4 knockout significantly attenuated the inhibitory effects of these NR modulators on osteosarcoma cell growth. Together, our results revealed that modulators of RARb, PPARg, LXRs and Rev-Erba inhibit osteosarcoma growth both in vitro and in vivo through the mTOR signaling pathway, suggesting that treatment with these NR modulators is a novel potential therapeutic strategy.

Targeting Signaling Pathway by Curcumin in Osteosarcoma

The most prevalent primary bone malignancy among children and adolescents is osteosarcoma. The high mortality rate of osteosarcoma is due to lung metastasis. Despite the development of multi-agent chemotherapy and surgical resection, patients with osteosarcoma have a high metastasis rate and poor prognosis. Thus, it is necessary to identify novel therapeutic agents to improve the 5-year survival rate of these patients. Curcumin, a phytochemical compound derived from Curcuma longa, has been employed in treating several types of cancers through various mechanisms. Also, in vitro studies have demonstrated that curcumin could inhibit cell proliferation and induce apoptosis in osteosarcoma cells. Development in identifying signaling pathways involved in the pathogenesis of osteosarcoma has provided insight into finding new therapeutic targets for the treatment of this cancer. Targeting MAPK/ERK, PI3k/AKT, Wnt/β-catenin, Notch, and MircoRNA by curcumin has been evaluated to improve outcomes in patients with osteosarcoma. Although curcumin is a potent anti-cancer compound, it has rarely been studied in clinical settings due to its congenital properties such as hydrophobicity and poor bioavailability. In this review, we recapitulate and describe the effect of curcumin in regulating signaling pathways involved in osteosarcoma.

MAPK-interacting kinases inhibition by eFT508 overcomes chemoresistance in preclinical model of osteosarcoma

The MAPK-interacting kinases 1 and 2 (MNK1/2) have generated increasing interest as therapeutic targets for many cancers with little known in osteosarcoma. This study evaluated the efficacy of eFT508, a highly selective inhibitor of MNK1/2, as single drug alone and in combination with paclitaxel in preclinical models of osteosarcoma. EFT508 is active against multiple osteosarcoma cell lines via inhibiting growth, survival and migration. It also demonstrates anti-osteosarcoma selectivity with much less toxicity on normal osteoblastic than osteosarcoma cells. Consistent with in vitro findings, eFT508 at non-toxic dose significantly arrested tumor growth in mice throughout the whole duration of treatment. Mechanistically, eEFT508 is highly effective in blocking eIF4E phosphorylation and eIF4E-mediated protein translation. Combination index shows that eFT508 and paclitaxel is synergistic in osteosarcoma cells. Our findings highlight the therapeutic value of MNK1/2 inhibition and suggest eFT508 as a promising candidate for the treatment of osteosarcoma.

Potential Anti-Metastatic Role of the Novel miR-CT3 in Tumor Angiogenesis and Osteosarcoma Invasion

Osteosarcoma (OS) is the most common primary bone tumor mainly occurring in young adults and derived from primitive bone-forming mesenchyme. OS develops in an intricate tumor microenvironment (TME) where cellular function regulated by microRNAs (miRNAs) may affect communication between OS cells and the surrounding TME. Therefore, miRNAs are considered potential therapeutic targets in cancer and one of the goals of research is to accurately define a specific signature of a miRNAs, which could reflect the phenotype of a particular tumor, such as OS. Through NGS approach, we previously found a specific molecular profile of miRNAs in OS and discovered 8 novel miRNAs. Among these, we deepen our knowledge on the fifth candidate renamed now miR-CT3. MiR-CT3 expression was low in OS cells when compared with human primary osteoblasts and healthy bone. Through TargetScan, VEGF-A was predicted as a potential biological target of miR-CT3 and luciferase assay confirmed it. We showed that enforced expression of miR-CT3 in two OS cell lines, SAOS-2 and MG-63, reduced expression of VEGF-A mRNA and protein, inhibiting tumor angiogenesis. Enforced expression of miR-CT3 also reduced OS cell migration and invasion as confirmed by soft agar colony formation assay. Interestingly, we found that miR-CT3 behaves inducing the activation of p38 MAP kinase pathway and modulating the epithelial-mesenchymal transition (EMT) proteins, in particular reducing Vimentin expression. Overall, our study highlights the novel role of miR-CT3 in regulating tumor angiogenesis and progression in OS cells, linking also to the modulation of EMT proteins.

Inflammatory conversion of quiescent osteoblasts by metastatic breast cancer cells through pERK1/2 aggravates cancer-induced bone destruction

Disruption of bone homeostasis caused by metastatic osteolytic breast cancer cells increases inflammatory osteolysis and decreases bone formation, thereby predisposing patients to pathological fracture and cancer growth. Alteration of osteoblast function induces skeletal diseases due to the disruption of bone homeostasis. We observed increased activation of pERK1/2 in osteolytic breast cancer cells and osteoblasts in human pathological specimens with aggressive osteolytic breast cancer metastases. We confirmed that osteolytic breast cancers with high expression of pERK1/2 disrupt bone homeostasis via osteoblastic ERK1/2 activation at the bone-breast cancer interface. The process of inflammatory osteolysis modulates ERK1/2 activation in osteoblasts and breast cancer cells through dominant-negative MEK1 expression and constitutively active MEK1 expression to promote cancer growth within bone. Trametinib, an FDA-approved MEK inhibitor, not only reduced breast cancer-induced bone destruction but also dramatically reduced cancer growth in bone by inhibiting the inflammatory skeletal microenvironment. Taken together, these findings suggest that ERK1/2 activation in both breast cancer cells and osteoblasts is required for osteolytic breast cancer-induced inflammatory osteolysis and that ERK1/2 pathway inhibitors may represent a promising adjuvant therapy for patients with aggressive osteolytic breast cancers by altering the shared cancer and bone microenvironment.

Emetine exerts anticancer effects in U2OS human osteosarcoma cells via activation of p38 and inhibition of ERK, JNK, and β-catenin signaling pathways

Osteosarcoma (OS) is a primary bone neoplasm that is highly malignant. As advances in chemotherapy for the treatment of OS have stagnated, discovery of new reagents is required. Emetine is a phytochemical which can be isolated from a medicinal herb Cephaelis ipecacuanha and is traditionally used for amoebicides. Previous studies have demonstrated that emetine can possibly be repositioned for use in anticancer reagents. However, any anticancer effects and underlying mechanisms of emetine on human OS are not yet well understood. In this study, we analyzed the anticancer effects and involved cellular mechanisms after treatment with emetine to U2OS human OS cells. Emetine significantly reduced both the viability and proliferation, and induced apoptosis via activation of caspase-3 and caspase-7 in U2OS cells. Emetine effectively inhibited the migration and invasion of U2OS cells. Gelatinase activities of matrix metalloproteinase 2 (MMP-2) and MMP-9 were reduced by emetine. MMP-9 was transcriptionally inhibited, while MMP-2 was posttranscriptionally repressed, via the reduced expression of membrane-type I-matrix metalloproteinase (MT1-MMP). p38, which is closely related with induction of apoptosis, was stimulated by emetine. Extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and β-catenin, which are linked with expression of MMPs, were downregulated. Emetine exerted anticancer effects on MG63 human OS cells as well. Taken together, our study demonstrated the anticancer and antimetastatic potential of emetine in treating human OS for the first time. It is expected that emetine may be a promising drug candidate to be repositioned for chemotherapy of OS.

Anti-Metastatic and Anti-Angiogenic Effects of Curcumin Analog DK1 on Human Osteosarcoma Cells In Vitro

Osteosarcoma (OS) is a life-threatening malignant bone tumor associated with poor prognosis among children. The survival rate of the patient is still arguably low even with intensive treatment provided, plus with the inherent side effects from the chemotherapy, which gives more unfavorable outcomes. Hence, the search for potent anti-osteosarcoma agent with promising safety profile is still on going. Natural occurring substance like curcumin has gained a lot of attention due to its splendid safety profile as well as it pharmacological advantages such as anti-metastasis and anti-angiogenesis. However, natural curcumin was widely known for its poor cellular uptake, which undermines all potential that it possesses. This prompted the development of synthetically synthesized curcuminoid analog, known as (Z)-3-hydroxy-1-(2-hydroxyphenyl)-3-phenylprop-2- en-1-one (DK1). In this present study, in vitro scratch assay, transwell migration/invasion assay, HUVEC tube formation assay, and ex vivo rat aortic ring assays were performed in order to investigate the anti-metastatic and anti-angiogenic potential of DK1. For further comprehension of DK1 mechanism on human osteosarcoma cell lines, microarray gene expression analysis, quantitative polymerase chain reaction (qPCR), and proteome profiler were adopted, providing valuable forecast from the expression of important genes and proteins related to metastasis and angiogenesis. Based on the data gathered from the bioassays, DK1 was able to inhibit the metastasis and angiogenesis of human osteosarcoma cell lines by significantly reducing the cell motility, number of migrated and invaded cells as well as the tube formation and micro-vessels sprouting. Additionally, DK1 also has significantly regulated several cancer pathways involved in OS proliferation, metastasis, and angiogenesis such as PI3K/Akt and NF-κB in both U-2 OS and MG-63. Regulation of PI3K/Akt caused up-regulation of genes related to metastasis inhibition, namely, PTEN, FOXO, PLK3, and GADD45A. Meanwhile, NF-κB pathway was regulated by mitigating the expression of NF-κB activator such as IKBKB and IKBKE in MG-63, whilst up-regulating the expression of NF-κB inhibitors such as NFKBIA and NFKBIE in U-2 OS. Finally, DK1 also has successfully hindered the metastatic and angiogenic capability of OS cell lines by down-regulating the expression of pro-metastatic genes and proteins like MMP3, COL11A1, FGF1, Endoglin, uPA, and IGFBP2 in U-2 OS. Whilst for MG-63, the significantly down-regulated oncogenes were Serpin E1, AKT2, VEGF, uPA, PD-ECGF, and Endoglin. These results suggest that curcumin analog DK1 may serve as a potential new anti-osteosarcoma agent due to its anti-metastatic and anti-angiogenic attributes.

Cold Atmospheric Plasma: A New Strategy Based Primarily on Oxidative Stress for Osteosarcoma Therapy

Osteosarcoma is the most common primary bone tumor, and its first line of treatment presents a high failure rate. The 5-year survival for children and teenagers with osteosarcoma is 70% (if diagnosed before it has metastasized) or 20% (if spread at the time of diagnosis), stressing the need for novel therapies. Recently, cold atmospheric plasmas (ionized gases consisting of UV-Vis radiation, electromagnetic fields and a great variety of reactive species) and plasma-treated liquids have been shown to have the potential to selectively eliminate cancer cells in different tumors through an oxidative stress-dependent mechanism. In this work, we review the current state of the art in cold plasma therapy for osteosarcoma. Specifically, we emphasize the mechanisms unveiled thus far regarding the action of plasmas on osteosarcoma. Finally, we review current and potential future approaches, emphasizing the most critical challenges for the development of osteosarcoma therapies based on this emerging technique.

Inhibitory effects on chondrosarcoma cell metastasis by Senna alata extract

BACKGROUND

Senna alata L. Roxb or candle bush is a traditional medicinal plant with a wide range of biological activities including anti-inflammatory, antimicrobial and antifungal. Leaf extract of S. alata showed the anti-tumor activity in various cancer cell lines. In this study, we focused on the inhibitory mechanism of S. alata extract (SAE) on cancer metastasis including cell migration, cell invasion and signaling pathways in chondrosarcoma SW1353 cells.

PURPOSE

This study aimed to evaluate the anti-metastatic mechanisms of Senna alata extract on chondrosarcoma SW1353 cells.

METHODS

Screening for phytochemicals in biologically active fraction of SAE was analysed by ¹H NMR spectroscopy. Cell viability and cytoxicity were determined by using MTT assay. Cell migration was observed by scratch wound healing and transwell migration assay. Cell invasion and cell adhesion assay were examined by Matrigel coated transwell chambers or plates. The expression of matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs), MAPKs and PI3K/Akt signaling pathways and NF-κB were detected by Western blot analysis.

RESULTS

The SAE treatment at the sub-cytoxic and non-cytotoxic concentrations significantly inhibited cell migration, cell invasion and cell adhesion of SW1353 cells in a dose-dependent manner. The results from Western blot analysis showed decreased MMP-2 and MMP-9 expression, while increased TIMP-1 and TIMP-2 expression in SAE treated cells. Moreover, SAE suppressed phosphorylation of ERK1/2, p38 and Akt but decreased NF-κB transcription factor expression in SW1353 cells.

CONCLUSION

These results revealed that SAE could reduce MMP-2 and MMP-9 expression by downregulation of NF-κB which is downstream of MAPKs and PI3K/Akt signaling pathway in SW1353 cells resulting in reduced cancer cell migration and invasion. Therefore, SAE may have the potential use as an alternative treatment of chondrosarcoma metastasis.

Mechanisms of Resistance to Conventional Therapies for Osteosarcoma

Osteosarcoma (OS) is the most common primary bone tumor, mainly occurring in children and adolescents. Current standard therapy includes tumor resection associated with multidrug chemotherapy. However, patient survival has not evolved for the past decades. Since the 1970s, the 5-year survival rate is around 75% for patients with localized OS but dramatically drops to 20% for bad responders to chemotherapy or patients with metastases. Resistance is one of the biological processes at the origin of therapeutic failure. Therefore, it is necessary to better understand and decipher molecular mechanisms of resistance to conventional chemotherapy in order to develop new strategies and to adapt treatments for patients, thus improving the survival rate. This review will describe most of the molecular mechanisms involved in OS chemoresistance, such as a decrease in intracellular accumulation of drugs, inactivation of drugs, improved DNA repair, modulations of signaling pathways, resistance linked to autophagy, disruption in genes expression linked to the cell cycle, or even implication of the micro-environment. We will also give an overview of potential therapeutic strategies to circumvent resistance development.

Identification of a survival-related signature for sarcoma patients through integrated transcriptomic and proteomic profiling analyses

Sarcoma (SARC) represents a group of highly histological and molecular heterogeneous rare malignant tumors with poor prognosis. There are few proposed classifiers for predicting patient's outcome. The Cancer Proteome Atlas (TPCA) and The Cancer Genome Atlas (TCGA) databases provide multi-omics datasets that enable a comprehensive investigation for this disease. The proteomic expression profile of SARC patients along with the clinical information was downloaded. 55 proteins were found to be associated with overall survival (OS) of patients using univariate Cox regression analysis. We developed a prognostic risk signature that comprises seven proteins (AMPKALPHA, CHK1, S6, ARID1A, RBM15, ACETYLATUBULINLYS40, and MSH6) with robust predictive performance using multivariate Cox stepwise regression analysis. Additionally, the signature could be an independent prognostic predictor after adjusting for clinicopathological parameters. Patients in high-risk group also have worse progression free intervals (PFI) than that of patients in low-risk group, but not for disease free intervals (DFI). The signature was validated using transcriptomic profile of SARC patients from TCGA. Potential mechanisms between high- and low-risk groups were identified using differentially expressed genes (DEGs) analysis. These DEGs were primarily enriched in RAS and MPAK signaling pathways. The signature protein molecules are candidate biomarkers for SARC, and the analysis of computational biology in tumor infiltrating lymphocytes and immune checkpoint molecules revealed distinctly immune landscapes of high- and low-risk patients. Together, we constructed a prognostic signature for predicting outcomes for SARC integrating proteomic and transcriptomic profiles, this might have value in guiding clinical practice.

PAK1 and PAK4 as therapeutic targets for Ewing sarcoma: a commentary

Ewing sarcoma (ES) is an aggressive pediatric bone tumor that is prone to metastasis. Due to low five-year survival rates and limited therapeutic options for metastatic disease, there is a dire clinical need for improved ES treatments. Targeting p21-activated kinases (PAKs) may be key. PAK1 and PAK4 are associated with aggressive ES and poor patient outcomes, although their molecular mechanisms remain largely uncharacterized in this disease. This commentary aims to highlight the recent advancements made to the understanding of PAK1 and PAK4 in ES in the paper "p21-activated kinases as viable therapeutic targets for the treatment of high-risk Ewing sarcoma" by Qasim et al.

Alpha Ketoglutarate Exerts In Vitro Anti-Osteosarcoma Effects through Inhibition of Cell Proliferation, Induction of Apoptosis via the JNK and Caspase 9-Dependent Mechanism, and Suppression of TGF-β and VEGF Production and Metastatic Potential of Cells

Osteosarcoma (OS) is the most common type of primary bone tumor. Currently, there are limited treatment options for metastatic OS. Alpha-ketoglutarate (AKG), i.e., a multifunctional intermediate of the Krebs cycle, is one of the central metabolic regulators of tumor fate and plays an important role in cancerogenesis and tumor progression. There is growing evidence suggesting that AKG may represent a novel adjuvant therapeutic opportunity in anti-cancer therapy. The present study was intended to check whether supplementation of Saos-2 and HOS osteosarcoma cell lines (harboring a TP53 mutation) with exogenous AKG exerted an anti-cancer effect. The results revealed that AKG inhibited the proliferation of both OS cell lines in a concentration-dependent manner. As evidenced by flow cytometry, AKG blocked cell cycle progression at the G₁ stage in both cell lines, which was accompanied by a decreased level of cyclin D1 in HOS and increased expression of p21^Waf1/Cip1 protein in Saos-2 cells (evaluated with the ELISA method). Moreover, AKG induced apoptotic cell death and caspase-3 activation in both OS cell lines (determined by cytometric analysis). Both the immunoblotting and cytometric analysis revealed that the AKG-induced apoptosis proceeded predominantly through activation of an intrinsic caspase 9-dependent apoptotic pathway and an increased Bax/Bcl-2 ratio. The apoptotic process in the AKG-treated cells was mediated via c-Jun N-terminal protein kinase (JNK) activation, as the specific inhibitor of this kinase partially rescued the cells from apoptotic death. In addition, the AKG treatment led to reduced activation of extracellular signal-regulated kinase (ERK1/2) and significant inhibition of cell migration and invasion in vitro concomitantly with decreased production of pro-metastatic transforming growth factor β (TGF-β) and pro-angiogenic vascular endothelial growth factor (VEGF) in both OS cell lines suggesting the anti-metastatic potential of this compound. In conclusion, we showed the anti-osteosarcoma potential of AKG and provided a rationale for a further study of the possible application of AKG in OS therapy.

Is Use of BMP-2 Associated with Tumor Growth and Osteoblastic Differentiation in Murine Models of Osteosarcoma?

BACKGROUND

The putative benefit of rhBMP-2 is in the setting of limb reconstruction using structural allografts, whether it be allograft-prosthetic composites, osteoarticular allografts, or intercalary segmental grafts. There are also potential advantages in augmenting osseointegration of uncemented endoprosthetics and in reducing infection. Recombinant human BMP-2 might mitigate nonunion in structural allograft augmented osteosarcoma limb salvage surgery; however, its use is limited because of concerns about the prooncogenic effects of the agent.

QUESTIONS/PURPOSES

(1) To assess if BMP-2 signaling influences osteosarcoma cell line growth. (2) To characterize degree of osteosarcoma cell line osteoblastic differentiation in response to BMP-2. (3) To assess if BMP-2 signaling has a consistent effect on local or systemic tumor burden in various orthotopic murine models of osteosarcoma.

METHODS

In this study, 143b, SaOS-2 and DLM8-M1 osteosarcoma cell lines were transfected with BMP-2 cDNA controlled by a constitutive promoter (experimental) or an empty vector (control) using a PiggyBac transposon system. Cellular proliferation was assessed using a quantitative MTT colorimetric assay. Osteoblastic differentiation was compared between control and experimental cell lines using quantitative real-time polymerase chain reaction of the osteoblastic markers connective tissue growth factor, Runx-2, Osterix, alkaline phosphatase and osteocalcin. Experimental and control cell lines were injected into the proximal tibia of either NOD-SCID (143b and SaOS-2 xenograft model), or C3H (DLM8-M1 syngeneic model) mice. Local tumor burden was quantitatively assessed using tumor volume caliper measurements and bioluminescence, and qualitatively assessed using post-mortem ex vivo microCT. Lung metastasis was qualitatively assessed by the presence of bioluminescence, and incidence was confirmed using histology. rhBMP-2 soaked absorbable collagen sponges (experimental) and sterile-H2O soaked absorbable collagen sponges (control) were implanted adjacent to 143b proximal tibial cell line injections to compare the effects of exogenous BMP-2 application with endogenous upregulation.

RESULTS

Constitutive expression of BMP-2 increased the in vitro proliferation of 143b cells (absorbance values 1.2 ± 0.1 versus 0.89 ± 0.1, mean difference 0.36 [95% CI 0.12 to 0.6]; p = 0.01), but had no effect on SaOS-2 and DLM8-M1 cell proliferation. In response to constitutive BMP-2 expression, 143b cells had no differences in osteoblastic differentiation, while DLM8-M1 cells downregulated the early marker connective tissue growth factor (mean ΔCt 0.2 ± 0.1 versus 0.6 ± 0.1; p = 0.002) and upregulated the early-mid range marker Runx-2 (mean ΔCt -0.8 ± 0.1 versus -1.1 ± 0.1; p = 0.002), and SaOS-2 cells upregulated the mid-range marker Osterix (mean ΔCt -2.1 ± 0.6 versus -3.9 ± 0.6; p = 0.002). Constitutive expression of BMP-2 resulted in greater 143b and DLM8-M1 local tumor volume (143b: 307.2 ± 106.8 mm versus 1316 ± 387.4 mm, mean difference 1009 mm [95% CI 674.5 to 1343]; p < 0.001, DLM8-M1 week four: 0 mm versus 326.1 ± 72.8 mm, mean difference 326.1 mm [95% CI 121.2 to 531]; p = 0.009), but modestly reduced local tumor growth in SaOS-2 (9.5 x 10 ± 8.3x10 photons/s versus 9.3 x 10 ± 1.5 x 10 photons/s, mean difference 8.6 x 10 photons/s [95% CI 5.1 x 10 to 1.2 x 10]; p < 0.001). Application of exogenous rhBMP-2 also increased 143b local tumor volume (495 ± 91.9 mm versus 1335 ± 102.7 mm, mean difference 840.3 mm [95% CI 671.7 to 1009]; p < 0.001). Incidence of lung metastases was not different between experimental or control groups for all experimental conditions.

CONCLUSIONS

As demonstrated by others, ectopic BMP-2 signaling has unpredictable effects on local tumor proliferation in murine models of osteosarcoma and does not consistently result in osteosarcoma cell line differentiation. Further investigations into other methods of safe bone and soft tissue healing augmentation and the use of differentiation therapies is warranted.

CLINICAL RELEVANCE

Our results indicate that BMP-2 has the potential to stimulate the growth of osteosarcoma cells that are poorly responsive to BMP-2 mediated osteoblastic differentiation. As this differentiation potential is unpredictable in the clinical setting, BMP-2 may promote the growth of microscopic residual tumor burden after resection. Our study provides further support for the recommendation to avoid the use of BMP-2 after limb-salvage surgery in patients with osteosarcoma.

EWS-FLI1 regulates and cooperates with core regulatory circuitry in Ewing sarcoma

Core regulatory circuitry (CRC)-dependent transcriptional network is critical for developmental tumors in children and adolescents carrying few gene mutations. However, whether and how CRC contributes to transcription regulation in Ewing sarcoma is unknown. Here, we identify and functionally validate a CRC 'trio' constituted by three transcription factors (TFs): KLF15, TCF4 and NKX2-2, in Ewing sarcoma cells. Epigenomic analyses demonstrate that EWS-FLI1, the primary fusion driver for this cancer, directly establishes super-enhancers of each of these three TFs to activate their transcription. In turn, KLF15, TCF4 and NKX2-2 co-bind to their own and each other's super-enhancers and promoters, forming an inter-connected auto-regulatory loop. Functionally, CRC factors contribute significantly to cell proliferation of Ewing sarcoma both in vitro and in vivo. Mechanistically, CRC factors exhibit prominent capacity of co-regulating the epigenome in cooperation with EWS-FLI1, occupying 77.2% of promoters and 55.6% of enhancers genome-wide. Downstream, CRC TFs coordinately regulate gene expression networks in Ewing sarcoma, controlling important signaling pathways for cancer, such as lipid metabolism pathway, PI3K/AKT and MAPK signaling pathways. Together, molecular characterization of the oncogenic CRC model advances our understanding of the biology of Ewing sarcoma. Moreover, CRC-downstream genes and signaling pathways may contain potential therapeutic targets for this malignancy.

Effects of oleuropein on tumor cell growth and bone remodelling: Potential clinical implications for the prevention and treatment of malignant bone diseases

Oleuropein (Ole) is the main bioactive phenolic compound present in olive leaves, fruits and olive oil. This molecule has been shown to exert beneficial effects on several human pathological conditions. In particular, recent preclinical and observational studies have provided evidence that Ole exhibits chemo-preventive effects on different types of human tumors. Studies undertaken to elucidate the specific mechanisms underlying these effects have shown that this molecule may thwart several key steps of malignant progression, including tumor cell proliferation, survival, angiogenesis, invasion and metastasis, by modulating the expression and activity of several growth factors, cytokines, adhesion molecules and enzymes involved in these processes. Interestingly, experimental observations have highlighted the fact that most of these signalling molecules also appear to be actively involved in the homing and growth of disseminating cancer cells in bones and, ultimately, in the development of metastatic bone diseases. These findings, and the experimental and clinical data reporting the preventive activity of Ole on various pathological conditions associated with a bone loss, are indicative of a potential therapeutic role of this molecule in the prevention and treatment of cancer-related bone diseases. This paper provides a current overview regarding the molecular mechanisms and the experimental findings underpinning a possible clinical role of Ole in the prevention and development of cancer-related bone diseases.

MDM2 Antagonists Induce a Paradoxical Activation of Erk1/2 through a P53-Dependent Mechanism in Dedifferentiated Liposarcomas: Implications for Combinatorial Strategies

The MDM2 gene is amplified in dedifferentiated liposarcoma (DDLPS). Treatment with MDM2 antagonists is a promising strategy to treat DDLPS; however, drug resistance is a major limitation when these drugs are used as a single agent. This study examined the impact of MDM2 antagonists on the mitogen-activated protein kinase (MAPK) pathway in DDLPS and investigated the potential synergistic activity of a MAPK kinase (MEK) inhibitor in combination with MDM2 antagonists. We identified a synergistic effect and identified the mechanism behind it. Combination effects of MDM2 antagonists and a MEK inhibitor were analyzed in a patient-derived xenograft mouse model and in DDLPS and leiomyosarcoma cell lines using different cell proliferation assays and immunoblot analysis. MDM2 antagonist (RG7388)-resistant IB115 [P4] cells and p53-silenced DDLPS cells were also established to understand the importance of functional p53. We found that MDM2 antagonists induced an upregulation of phosphorylated extracellular signal-regulated kinase (p-ERK) in DDLPS cells. The upregulation of p-ERK occurred due to mitochondrial translocation of p53, which resulted in increased production of reactive oxygen species, causing the activation of receptor tyrosine kinases (RTKs). Activated RTKs led to the activation of the downstream MEK/ERK signaling pathway. Treatment with a MEK inhibitor resulted in decreased expression of p-ERK, causing significant anti-tumor synergy when combined with MDM2 antagonists. Our results provide a framework for designing clinical studies of combination therapies in DDLPS patients.

Role of TKI for Metastatic Osteogenic Sarcoma

OPINION STATEMENT

Osteosarcomas (OS) belong to a large family of mesenchymal tumor entities which exhibit heterogenous histological, genetic, and molecular features. Current OS treatment regimen consists of the combination of surgery and intensive multi-agent chemotherapy. Ever since the introduction of chemotherapy, 5-year survival rate among OS patients has improved to 60-75%. However, 30-35% of OS patients are associated with pulmonary metastasis and relapse, which have significantly poor prognosis, with an overall 5-year survival rate of about 20%. The fact that OS are both rare forms of cancer and highly heterogeneous may explain why patients' survival has not improved in the past three decades, especially for metastatic/relapsed and unresectable osteosarcomas. Patients who experience relapse with metastatic disease have limited therapeutic options, often receiving additional cytotoxic therapy such as ifosfamide and etoposide and/or carboplatin or gemcitabine plus docetaxel. Novel precise OS-targeted thrapies are being developed with the hope of improving metastatic/relapsed OS prognosis. This review provides an overview of the most updated targeted therapies in relapsed/metastatic osteosarcoma and dicusses some clinical options in order to improve progression-free survival.

Down-Regulation of Ribosomal Protein RPS21 Inhibits Invasive Behavior of Osteosarcoma Cells Through the Inactivation of MAPK Pathway

Objective

The goal of our present study was to explore the expression level, biological function, and underlying molecular mechanism of ribosomal protein s21 (RPS21) in human osteosarcoma (OS).

Methods

Firstly, we evaluated the expression of RPS21 in OS tissue samples based on the Gene Expression Omnibus (GEO) datasets and also measured the RPS21 expression of OS cell lines (MG63, and U2OS) by quantitative real-time polymerase chain reaction (qRT-PCR). siRNA interference method was used to reduce the expression of RSP21 in the OS cells. Cell Counting Kit-8 (CCK-8), colony formation, wound-healing, and transwell assays were conducted to measure the proliferation, migration, and invasion of OS cells. The mitogen-activated protein kinase (MAPK) pathway-related proteins levels were examined by Western blot.

Results

Our analyses showed that the expression of RPS21 was significantly increased in OS, compared with normal samples. Upregulation of RPS21 was associated with worse outcomes of OS patients. Knockdown of RPS21 suppressed OS cell proliferation, colony-forming ability, migration, and invasion capacities. Moreover, down-regulation of RPS21 inactivated the MAPK signaling pathway.

Conclusion

RPS21 plays an oncogenic candidate in OS development via regulating the activity of MAPK pathway; therefore, it may serve as a novel therapeutic target for OS treatment.

Pazopanib and Trametinib as a Synergistic Strategy against Osteosarcoma: Preclinical Activity and Molecular Insights

Receptor tyrosine kinases (RTKs) inhibitors’ activity in advanced osteosarcoma is significant but short-lived. To prevent or at least delay drug resistance, we explored a vertical inhibition by combining drugs acting at different levels of the RTK pathways (pazopanib + trametinib). We studied pazopanib + trametinib antitumor activity both in vitro and in vivo (MNNG-HOS and KHOS xenografts in NOD/SCID mice) investigating the molecular mechanisms and potential escapes. The involvement of MAPK-PI3K pathways was validated by Nanostring technology, western blot and by silencing/overexpression experiments. Pazopanib targets were expressed on seven osteosarcoma cell lines and their pathways were activated. Pazopanib + trametinib exhibited synergistic antitumor activity by inducing apoptosis and inhibiting ERK1/2 and Akt. In vivo antitumor activity was shown in osteosarcoma-bearing mice. The drug combination significantly down-modulated RTK Ephrin Type-A Receptor 2 (EphA2) and Interleukin-7 Receptor (IL-7R), whereas induced mitogen-activated protein-kinase kinase (MAPKK) MEK6. EphA2 silencing significantly reduced osteosarcoma cell proliferation and migration, while impeding MEK6 up-regulation in the treated cells significantly increased the antitumor effect of the studied drugs. Moreover, the up-regulation of MEK6 reduced combination activity. Pazopanib + trametinib demonstrated synergistic antitumor effects in osteosarcoma models through ERK and Akt inhibition and EphA2 and IL-7R down-modulation. MEK6 up-regulation might evoke escaping mechanism.

AdipoRon Affects Cell Cycle Progression and Inhibits Proliferation in Human Osteosarcoma Cells

AdipoRon (AdipoR) is the first synthetic molecule acting as a selective and potent adiponectin receptor agonist. Recently, the possible pharmacological use of AdipoR in different pathological conditions has been addressed. Interestingly, initial evidence suggests that AdipoR may have anticancer properties in different preclinical models, such as pancreatic and ovarian cancer. To our knowledge, so far no research has been directed at determining the impact of AdipoR on osteosarcoma, the most aggressive and metastatic bone malignancy occurring in childhood and adolescence age. Here, we investigate the possible antitumor effects of AdipoR in osteosarcoma cell lines. MTT and cell growth curve assays clearly indicate that AdipoR inhibits, at different extents, proliferation in both U2OS and Saos-2 osteosarcoma cell lines, the latter being more sensitive. Moreover, flow cytometry-based assays point out a significant G0/G1 phase accumulation and a contemporary S phase decrease in response to AdipoR. Consistent with the different sensitivity, a strong subG1 appearance in Saos-2 after 48 and 72 hours of treatment is also observed. The investigation of the molecular mechanisms highlights a common and initial ERK1/2 activation in response to AdipoR in both Saos-2 and U2OS cells. Interestingly, a simultaneous and dramatic downregulation of p70S6K phosphorylation, one of the main targets of mTORC1 pathway, has also been observed in AdipoR-treated Saos-2, but not in U2OS cells. Importantly, a strengthening of AdipoR-induced effects was reported upon everolimus-mediated mTORC1 perturbation in U2OS cells. In conclusion, our findings provide initial evidence of AdipoR as an anticancer molecule differently affecting various signaling pathways involved in cell cycle and cell death in osteosarcoma cells and encourage the design of future studies to further understand its pattern of activities.

Genomic Complexity of Osteosarcoma and Its Implication for Preclinical and Clinical Targeted Therapies

Osteosarcoma is a genomically complex disease characterized by few recurrent single-nucleotide mutations or in-frame fusions. In contrast, structural alterations, including copy number changes, chromothripsis, kataegis, loss of heterozygosity (LOH), and other large-scale genomic alterations, are frequent and widespread across the osteosarcoma genome. These observed structural alterations lead to activation of oncogenes and loss of tumor suppressors which together contribute to oncogenesis. To date, few targeted therapies for osteosarcoma have been identified. It is likely that effectiveness of targeted therapies will vary greatly in subsets of tumors with distinct key driver events. Model systems which can recapitulate the genetic heterogeneity of this disease are needed to test this hypothesis. One possible approach is to use patient-derived xenograft (PDX) models characterized with regards to their similarity to the human tumor samples from which they were derived. Here we review evidence pointing to the genomic complexity of osteosarcoma and how this is reflected in available model systems. We also review the current state of preclinical testing for targeted therapies using these models.

Increased expression of ecotropic viral integration site 2A indicates a poor prognosis and promotes osteosarcoma evolution through activating MEK/ERK pathway

Although ecotropic viral integration site 2 A (EVI2A) plays key roles in several cancers, the expression and function of EVI2A in osteosarcoma (OS) have not been investigated. Hence, we explored the expression of EVI2A and its clinical significance of EVI2A of OS. Firstly, we investigated the expression of EVI2A in OS tissues. The relationship of EVI2A expression and survival time was analyzed using Kaplan-Meier plotter. Then, we used quantitative reverse transcription PCR (qRT-PCR) to confirm the expression level of EVI2A in OS cell lines. Cell proliferation, and wound-healing experiments were used to identify the biological function of EVI2A. Moreover, EVI2A-mediated MEK/ERK signaling pathway was evaluated using western blotting. Data suggested that EVI2A was highly expressed in OS tissues, and high-expression of EVI2A was associated with worse overall survival in OS patients. Moreover, the up-regulation of it was observed in OS cell lines (Saos2, and MG63). Knockdown of EVI2A suppressed cell proliferation and migration of OS. Western blotting revealed that the inactivation of MEK/ERK pathway was found in OS cells after EVI2A knockdown. Our data implicated the crucial role of EVI2A in the progression of OS, demonstrating that expression of EVI2A may offer an attractive novel prognostic signature for OS.

Licochalcone A-Induced Apoptosis Through the Activation of p38MAPK Pathway Mediated Mitochondrial Pathways of Apoptosis in Human Osteosarcoma Cells In Vitro and In Vivo

BACKGROUND

Licochalcone A (LicA) is isolated from the roots of Glycyrrhiza glabra and possesses antitumor and anti-invasive activities against several tumor cells. However, the antitumor effects of LicA on human osteosarcoma cells have yet to be demonstrated either in vitro or in vivo.

METHODS

Cell viability was measured by MTT assay. Apoptosis and mitochondrial dysfunction were detected with Annexin V/PI staining and JC-1 staining by flow cytometry. The expressions of caspase- or mitochondrial-related proteins were demonstrated by western blotting. Antitumor effect of LicA on 143B xenograft mice in vivo.

RESULTS

LicA could inhibit cell proliferation and induce apoptosis in human osteosarcoma cells, as evidenced by a decrease in cell viability, loss of mitochondrial membrane potentials, and activation of caspases. LicA treatment substantially reduced the expression of Bcl-2 and Mcl-1 and increased the expression of cleaved-caspase-3, cleaved-caspase-9, cleaved-PARP, and Bax in HOS and U2OS cells. Moreover, mitochondrial membrane potential and apoptosis suppression mediated by Z-VAD or tauroursodeoxycholic acid significantly reduced LicA-induced mitochondria-dependent apoptosis. The study also determined that LicA treatment induced p38MAPK phosphorylation, but siRNA-p38 or BIRB796 substantially reversed cell viability through the inhibition of mitochondria-dependent apoptosis pathways. Finally, an in vivo study revealed that LicA significantly inhibited 143B xenograft tumor growth.

CONCLUSIONS

These findings demonstrate that LicA has antitumor activities against human osteosarcoma cells through p38MAPK regulation of mitochondria-mediated intrinsic apoptotic pathways in vitro and in vivo.

Chlorogenic acid activates ERK1/2 and inhibits proliferation of osteosarcoma cells

Osteosarcoma (OS) is a very aggressive metastatic pediatric and adolescent tumor. Due to its recurrent development of chemotherapy resistance, clinical outcome for OS patients remains poor. Therefore, discovering more effective anticancer agents is needed. Chlorogenic acid (CGA) is a phenolic compound contained in plant-related products that modulates many cellular functions and inhibits cell proliferation in several cancer types. However, few evidence is available in OS. Here, we investigate the effects of CGA in U2OS, Saos-2, and MG-63 OS cells. By multiple approaches, we demonstrate that CGA acts as anticancer molecule affecting the cell cycle and provoking cell growth inhibition mainly by apoptosis induction. We also provide evidence that CGA strongly activates extracellular-signal-regulated kinase1/2 (ERK1/2). Strikingly, ERK1/2 inhibitor PD98059 sensitizes the cells to CGA. Altogether, our data enforce the evidence of the anticancer activity mediated by CGA and provide the rationale for the development of innovative therapeutic strategies in OS cure.

Efficacy of an anti-cancer strategy targeting SET in canine osteosarcoma

Osteosarcoma (OSA) is the most common bone tumor in dogs. Protein phosphatase 2A (PP2A), an evolutionary conserved serine/threonine protein phosphatase, is a crucial tumor suppressor. SET is a PP2A inhibitory protein that directly interacts with PP2A and suppresses its phosphatase activity. SET has been reported as a contributor of wide range of human and dog tumor malignancies. However, the role of SET in canine OSA (cOSA) remains unknown. In this study, we investigated the role of SET in cOSA by using 2 cOSA cell lines: POS (primary origin) and HM-POS (metastatic origin). Knockdown (KD) of SET expression was noted to slightly suppress POS cell proliferation only. Furthermore, SET KD effectively suppressed colony formation ability of both POS and HM-POS cells. SET KD was observed to repress ERK1/2, mTOR, E2F1, and NF-κB signaling in HM-POS cells, whereas it inhibited only ERK1/2 signaling in POS. Further, it was observed that SET-targeting drug, FTY720, exerted anti-cancer effects in both POS and HM-POS cells. Moreover, the drug also enhanced the anti-cancer effect of cisplatin. The data suggested that a combination therapy, based on SET targeting drugs and cisplatin, could be a potent strategy for cOSA.

Protein Kinase B and Extracellular Signal-Regulated Kinase Inactivation is Associated with Regorafenib-Induced Inhibition of Osteosarcoma Progression In Vitro and In Vivo

Osteosarcoma is the most common type of bone cancer. Multimodality treatment involving chemotherapy, radiotherapy and surgery is not effective enough to control osteosarcoma. Regorafenib, the oral multi-kinase inhibitor, has been shown to have positive efficacy on disease progression delay in chemotherapy resistant osteosarcoma patients. However anti-cancer effect and mechanism of regorafenib in osteosarcoma is ambiguous. Thus, the aim of this study is to investigate the efficacy and molecular mechanism of regorafenib on osteosarcoma in vitro and in vivo. Human osteosarcomas U-2 OS or MG-63 were treated with regorafenib, miltefosine (protein kinase B (AKT) inhibitor), or PD98059 (mitogen-activated protein/extracellular signal-regulated kinase (MEK) pathway inhibitor) for 24 or 48 h. Cell viability, apoptotic signaling transduction, tumor invasion, expression of tumor progression-associated proteins and tumor growth after regorafenib treatment were assayed by MTT 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, flow cytometry, transwell assay, Western blotting assay and in vivo animal experiment, respectively. In these studies, we also indicated that regorafenib suppressed cell growth by prompting apoptosis of osteosarcoma cells, which is mediated through inactivation of ERK and AKT signaling pathways. After regorafenib treatment, downregulation of related genes in invasion (vascular endothelial growth factor (VEGF) and matrix metallopeptidase 9 (MMP-9)), proliferation (CyclinD1) and anti-apoptosis (X-linked inhibitor of apoptosis protein (XIAP), myeloid cell leukemia-1 (MCL-1), and cellular FLICE (FADD-like IL-1β-converting enzyme)-inhibitory protein (C-FLIP)) were found. Moreover, upregulation of caspase-3 and caspase-8 cleavage were also observed. In sum, we suggest that regorafenib has potential to suppress osteosarcoma progression via inactivation of AKT and ERK mediated signaling pathway.

Anoikis‑resistant human osteosarcoma cells display significant angiogenesis by activating the Src kinase‑mediated MAPK pathway

Tumor cells must resist anoikis to metastasize. There is a key role of angiogenesis in the growth and metastasis of tumors. However, the relationship between anoikis resistance and angiogenesis has not been well explored in human osteosarcoma. In the present study, we reported the higher expression of vascular endothelial growth factor-A (VEGF-A) in osteosarcoma cells that were resistant to anoikis than in parental osteosarcoma cells, promoting the proliferation, tube formation, and migration of human umbilical vein endothelial cells (HUVECs). Src, JNK (Jun amino-terminal kinase) and ERK (extracellular signal-regulated kinase) signaling pathway phosphorylation was activated in anoikis-resistant cells; Src inhibitor reduced the expression of VEGF-A and angiogenesis and inhibited JNK and ERK pathway activity. Overexpression of phosphorylated (p)-Src and VEGF-A was positively correlated to the metastatic potential in human osteosarcoma tissues, as quantified by immunohistochemistry. In addition, p-Src expression was directly correlated with VEGF-A expression and microvessel density in vivo. Our findings revealed that anoikis resistance in osteosarcoma cells increased the expression of VEGF-A and angiogenesis through the Src/JNK/ERK signaling pathways. Thus, Src may be a potential therapeutic alternative in osteosarcoma angiogenesis and metastasis.

Novel molecular insights and new therapeutic strategies in osteosarcoma

Osteosarcoma (OS) is one of the most prevalent malignant cancers with lower survival and poor overall prognosis mainly in children and adolescents. Identifying the molecular mechanisms and OS stem cells (OSCs) as new concepts involved in disease pathogenesis and progression may potentially lead to new therapeutic targets. Therefore, therapeutic targeting of OSCs can be one of the most important and effective strategies for the treatment of OS. This review describes the new molecular targets of OS as well as novel therapeutic approaches in the design of future investigations and treatment.

An analysis of the expression and function of myeloid differentiation factor 88 in human osteosarcoma

The aim of the present study was to investigate the expression and function of myeloid differentiation factor 88 (MyD88) in osteosarcoma. Immunohistochemical staining was used to detect MyD88 protein in osteosarcoma tissues and matched normal bone tissues. The association between MyD88 expression and the clinical characteristics of patients with osteosarcoma was analyzed. Furthermore, survival analysis of patients with osteosarcoma was performed to study the association between MyD88 expression and patient prognosis. Finally, the effect of the MyD88 inhibitor, ST2825, on the proliferation and apoptosis of the human osteosarcoma cell line U2OS was examined. Additionally, cell proliferation, invasion and apoptosis were examined using an MTT assay, Transwell assay and Annexin V-fluorescein isothiocyanate staining kit, respectively. The expression of proteins associated with the NF-κB signaling pathway was analyzed by western blotting. The positive expression rate of MyD88 in osteosarcoma and normal bone tissues was 71.4 and 6.1%, respectively. Statistical analysis demonstrated that MyD88 was not associated with gender, age, histological type or tumor location, but that it was associated with Enneking stage and tumor metastasis (P<0.05). According to the survival analysis, patients with osteosarcoma in the high MyD88 expression group displayed a reduced overall survival rate (P<0.05). Furthermore, inhibition of MyD88 by ST2825 in U2OS cells resulted in a marked decrease in cellular proliferation and migration, and an increase in the rate of apoptosis (P<0.05). Notably, ST2825 significantly decreased cyclin D1, matrix metallopeptidase-9 and nucleus p65 expression, but increased cleaved-caspase 3 expression in ST2825-treated U2OS cells (P<0.05). The results of the present study indicated that MyD88 expression is associated with the progression of osteosarcoma and may be a potential therapeutic target for the treatment of osteosarcoma.

Individualized doxorubicin sensitivity testing of undifferentiated soft tissue sarcoma (USTS) in a patient-derived orthotopic xenograft (PDOX) model demonstrates large differences between patients

Doxorubicin (DOX) is often first-line treatment of undifferentiated/unclassified soft tissue sarcoma (USTS). However, the DOX response rate for USTS patients is low. Individualized precision-medicine technology that could identify DOX responders as well as non-responders would be of high value to cancer patients. In the present study, we established 5 patient-derived orthotopic xenograft (PDOX) nude mouse models from 5 USTS patients and evaluated the efficacy of DOX in each PDOX model. USTS's were grown orthotopically in the right thigh of nude mice to establish the PDOX models. Two weeks after implantation, the mouse models were randomized into two groups of 8 mice each: untreated control; and DOX (3 mg/kg, i.p., once a week for 2 weeks). DOX showed significant growth inhibition in only 2 USTS PDOX models out of 5 (p = 0.0054, p = 0.0055, respectively) on day 14 after initiation. DOX was ineffective in the other 3 PDOX models. However, even in the DOX-sensitive cases, DOX could not regress the PDOX tumors responding to treatment. The present study has important implications since this is the first in vivo study to compare the DOX sensitivity for USTS on multiple patient tumors. We showed that only two of five USTS were responsive to DOX, despite DOX being first line chemotherapy for USTS. The 3 resistant cases should not be treated with DOX clinically, in order to spare the patients' unnecessary toxicity. This PDOX model is useful for precise individualized drug sensitivity testing, especially for rare heterogeneous recalcitrant sarcomas such as USTS.

Targeting the epigenetic readers in Ewing sarcoma inhibits the oncogenic transcription factor EWS/Fli1

Ewing Sarcoma is a rare bone and soft tissue malignancy affecting children and young adults. Chromosomal translocations in this cancer produce fusion oncogenes as characteristic molecular signatures of the disease. The most common case is the translocation t (11; 22) (q24;q12) which yields the EWS-Fli1 chimeric transcription factor. Finding a way to directly target EWS-Fli1 remains a central therapeutic approach to eradicate this aggressive cancer. Here we demonstrate that treating Ewing Sarcoma cells with JQ1(+), a BET bromodomain inhibitor, represses directly EWS-Fli1 transcription as well as its transcriptional program. Moreover, the Chromatin Immuno Precipitation experiments demonstrate for the first time that these results are a consequence of the depletion of BRD4, one of the BET bromodomains protein from the EWS-Fli1 promoter. In vitro, JQ1(+) treatment reduces the cell viability, impairs the cell clonogenic and the migratory abilities, and induces a G1-phase blockage as well as a time- and a dose-dependent apoptosis. Furthermore, in our in vivo model, we observed a tumor burden delay, an inhibition of the global vascularization and an increase of the mice overall survival. Taken together, our data indicate that inhibiting the BET bromodomains interferes with EWS-FLi1 transcription and could be a promising strategy in the Ewing tumors context.

RSF1 functions as an oncogene in osteosarcoma and is regulated by XIST/miR-193a-3p axis

RSF1 (HBXAP), is a member of ATP-dependent chromatin remodeling factor. Dysregulated RSF1 has been reported to be related to tumor progression. However, the function of RSF1 in osteosarcoma (OS) remains unclear. In this study, we showed that RSF1 expression was upregulated in OS cells. RSF1 inhibition suppressed OS cell proliferation and invasion. We further showed that MAPK/Erk signaling pathway was inactivated by RSF1 suppression. In addition, RSF1 was identified as a direct target of miR-193a-3p. Clinically, RSF1 was increased and associated with advanced clinical features and poor overall survival of OS patients. MiR-193a-3p expression was decreased and associated with advanced clinical features and poor overall survival of OS patients. In addition, we found that miR-193a-3p was negatively correlated with RSF1 expression in OS tissues. Moreover, our data showed that XIST could function as competing endogenous RNA to repress miR-193a-3p, which regulated its downstream target RSF1. In conclusion, our findings demonstrated that the XIST/miR-193a-3p/RSF1 axis might contribute to the progression and act as a therapeutic target of OS patients.

Phase Ib/II Study of the Safety and Efficacy of Combination Therapy with Multikinase VEGF Inhibitor Pazopanib and MEK Inhibitor Trametinib In Advanced Soft Tissue Sarcoma

Purpose: Pazopanib, a multireceptor tyrosine kinase inhibitor targeting primarily VEGFRs1-3, is approved for advanced soft tissue sarcoma (STS) and renal cell cancer. Downstream of VEGFR, trametinib is an FDA-approved MEK inhibitor used for melanoma. We hypothesized that vertical pathway inhibition using trametinib would synergize with pazopanib in advanced STS.Experimental Design: In an open-label, multicenter, investigator-initiated National Comprehensive Cancer Network (NCCN)-sponsored trial, patients with metastatic or advanced STS received pazopanib 800 mg and 2 mg of trametinib continuously for 28-day cycles. The primary endpoint was 4-month progression-free survival (PFS). Secondary endpoints were overall survival, response rate, and disease control rate.Results: Twenty-five patients were enrolled. The median age was 49 years (range, 22-77 years) and 52% were male. Median PFS was 2.27 months [95% confidence interval (CI), 1.9-3.9], and the 4-month PFS rate was 21.1% (95% CI, 9.7-45.9), which was not an improvement over the hypothesized null 4-month PFS rate of 28.3% (P = 0.79). Median overall survival was 9.0 months (95% CI, 5.7-17.7). A partial response occurred in 2 (8%) of the evaluable patients (95% CI, 1.0-26.0), one with PIK3CA E542K-mutant embryonal rhabdomyosarcoma and another with spindle cell sarcoma. The disease control rate was 14/25 (56%; 95% CI, 34.9-75.6). The most common adverse events were diarrhea (84%), nausea (64%), fatigue (56%), and hypertension (52%).Conclusions: The combination of pazopanib and trametinib was tolerable without indication of added activity of the combination in STS. Further study may be warranted in RAS/RAF aberrant sarcomas. Clin Cancer Res; 23(15); 4027-34. ©2017 AACR.

Anti-angiogenesis target therapy for advanced osteosarcoma (Review)

Osteosarcomas (OS), especially those with metastatic or unresectable disease, have limited treatment options. The greatest advancement in treatments occurred in the 1980s when multi-agent chemotherapy, including doxorubicin, cisplatin, high-dose methotrexate, and, in some regimens, ifosfamide, was demonstrated to improve overall survival compared with surgery alone. However, standard chemotherapeutic options have been limited by poor response rates in patients with relapsed or advanced cases. It has been reported that VEGFR expression correlates with the outcome of patients with osteosarcoma and circulating VEGF level has been associated with the development of lung metastasis. At present, it seems to us that progress has not been made since Grignani reported a phase II cohort trial of sorafenib and sorafenib combined with everolimus for advanced osteosarcoma, which, in a sense, have become a milestone as a second-line therapy for osteosarcoma. Although the recognization of muramyltripepetide phosphatidyl-ethanolamine has made some progress based on its combination with standard chemotherapy, its effect on refractory cases is controversial. Personalized comprehensive molecular profiling of high-risk osteosarcoma up to now has not changed the therapeutic prospect of advanced osteosarcoma significantly. Thus, how far have we moved forward and what therapeutic strategy should we prefer for anti-angiogenesis therapy? This review provides an overview of the most updated anti-angiogenesis therapy in OS and discusses some clinical options in order to maintain or even improve progression-free survival.

Decrease in stathmin expression by arsenic trioxide inhibits the proliferation and invasion of osteosarcoma cells via the MAPK signal pathway

Osteosarcoma (OS) is the most common type of malignant bone tumor in children and adolescents. In total, 40–50% of patients with OS experience metastasis, and thus have a poor prognosis. Our previous study demonstrated that arsenic trioxide (As₂O₃) combined with doxorubicin [also known as Adriamycin (ADM)] significantly inhibited OS cell proliferation by downregulating stathmin expression. The present study investigated the effect and mechanism of stathmin expression on OS cell invasion. It was identified that the expression of stathmin was increased in human ADM-resistant OS MG63 (MG63/dox) cells compared with the level in the normal osteoblast hFoB1.19cell line using western blot analysis. Lentiviral-mediated small hairpin RNA (shRNA) was constructed to silence stathmin expression of MG63/dox cells. In transwell assay, stathmin-knockdown significantly suppressed migration and invasion in MG63/dox cells. As₂O₃ combined with ADM inhibited the migration and invasion of MG63/dox cells, and was associated with the downregulation of phosphorylated-mitogen-activated protein kinase (MAPK) 1 and β-catenin, and upregulation of phosphorylated-MAPK8 and E-cadherin. In addition, stathmin-knockdown significantly suppressed tumor growth and increased E-cadherin expression in a xenograft nude mouse model. Taken together, these data suggested that As₂O₃ combined with ADM inhibited stathmin-mediated invasion via the MAPK pathway. Elucidation of the mechanism for stathmin downregulation by As₂O₃ may provide novel insights into the mechanism of OS metastasis.

Biomarkers of Osteosarcoma, Chondrosarcoma, and Ewing Sarcoma

Osteosarcoma is the most frequent malignant bone neoplasm, followed by chondrosarcoma and Ewing sarcoma. The diagnosis of bone neoplasms is generally made through histological evaluation of a biopsy. Clinical and radiological features are also important in aiding diagnosis and to complete the staging of bone cancer. In addition to these, there are several non-specific serological or specific molecular markers for bone neoplasms. In bone tumors, molecular markers increase the accuracy of the diagnosis and assist in subtyping bone tumors. Here, we review these markers and discuss their role in the diagnosis and prognosis of the three most frequent malignant bone neoplasms, namely osteosarcoma, chondrosarcoma, and Ewing sarcoma.