Doxorubicin-resistant osteosarcoma: novel therapeutic approaches in sight?

Blocking CXCR4-CARM1-YAP axis overcomes osteosarcoma doxorubicin resistance by suppressing aerobic glycolysis

Osteosarcoma, recognized for its aggressiveness and resistance to chemotherapy, notably doxorubicin, poses significant treatment challenges. This comprehensive study investigated the CXCR4-CARM1-YAP signaling axis and its pivotal function in controlling aerobic glycolysis, which plays a crucial role in doxorubicin resistance. Detailed analysis of Dox-resistant 143b/MG63-DoxR cells has uncovered the overexpression of CXCR4. Utilizing a combination of molecular biology techniques including gene silencing, aerobic glycolysis assays such as Seahorse experiments, RNA sequencing, and immunofluorescence staining. The study provides insight into the mechanistic pathways involved. Results demonstrated that disrupting CXCR4 expression sensitizes cells to doxorubicin-induced apoptosis and alters glycolytic activity. Further RNA sequencing revealed that CARM1 modulated this effect through its influence on glycolysis, with immunofluorescence of clinical samples confirming the overexpression of CXCR4 and CARM1 in drug-resistant tumors. Chromatin immunoprecipitation studies further highlighted the role of CARM1, showing it to be regulated by methylation at the H3R17 site, which in turn affected YAP expression. Crucially, in vivo experiments illustrated that CARM1 overexpression could counteract the tumor growth suppression that resulted from CXCR4 inhibition. These insights revealed the intricate mechanisms at play in osteosarcoma resistance to doxorubicin and pointed toward potential new therapeutic strategies that could target this metabolic and signaling network to overcome drug resistance and improve patient outcomes.

ERRα contributes to HDAC6-induced chemoresistance of osteosarcoma cells

Chemotherapy resistance is an important problem for clinical therapy of osteosarcoma (OS). The potential effects of histone deacetylases (HDACs) on OS chemoresistance are studied. The expression of HDACs in OS cells resistance to doxorubicin (Dox) and cisplatin (CDDP) is checked. Among 11 members of HDACs, levels of HDAC6 are significantly upregulated in OS cells resistance to Dox and CDDP. Inhibition of HDAC6 via its specific inhibitor ACY1215 restores chemosensitivity of OS-resistant cells. Further, HDAC6 directly binds with estrogen-related receptors alpha (ERRα) to regulate its acetylation and protein stability. Inhibition of ERRα further strengthens ACY1215-increased chemosensitivity of OS-resistant cells. Mechanistically, K129 acetylation is the key residue for HDAC6-regulated protein levels of ERRα. Collectively, we find that ERRα contributes to HDAC6-induced chemoresistance of OS cells. Inhibition of HDAC6/ERRα axis might be a potential approach to overcome chemoresistance and improve therapy efficiency for OS treatment. 1. HDAC6 was significantly upregulated in Dox and CDDP resistant OS cells; 2. Inhibition of HDAC6 can restore chemosensitivity of OS cells; 3. HDAC6 binds with ERRα at K129 to decrease its acetylation and increase protein stability; 4. ERRα contributes to HDAC6-induced chemoresistance of OS cells.

Rapamycin-induced autophagy in osteosarcoma cells is mediated via the biglycan/Wnt/β-catenin signaling axis

Biglycan is a class I secreted small leucine-rich proteoglycan (SLRP), which regulates signaling pathways connected to bone pathologies. Autophagy is a vital catabolic process with a dual role in cancer progression. Here, we show that biglycan inhibits autophagy in two osteosarcoma cell lines (P ≤ 0.001), while rapamycin-induced autophagy decreases biglycan expression in MG63 osteosarcoma cells and abrogates the biglycan-induced cell growth increase (P ≤ 0.001). Rapamycin also inhibits β-catenin translocation to the nucleus, inhibiting the Wnt pathway (P ≤ 0.001) and reducing biglycan's colocalization with the Wnt coreceptor LRP6 (P ≤ 0.05). Furthermore, biglycan exhibits protective effects against the chemotherapeutic drug doxorubicin in MG63 OS cells through an autophagy-dependent manner (P ≤ 0.05). Cotreatment of these cells with rapamycin and doxorubicin enhances cells response to doxorubicin by decreasing biglycan (P ≤ 0.001) and β-catenin (P ≤ 0.05) expression. Biglycan deficiency leads to increased caspase-3 activation (P ≤ 0.05), suggesting increased apoptosis of biglycan-deficient cells treated with doxorubicin. Computational models of LRP6 and biglycan complexes suggest that biglycan changes the receptor's ability to interact with other signaling molecules by affecting the interdomain bending angles in the receptor structure. Biglycan binding to LRP6 activates the Wnt pathway and β-catenin nuclear translocation by disrupting β-catenin degradation complex (P ≤ 0.01 and P ≤ 0.05). Interestingly, this mechanism is not followed in moderately differentiated, biglycan-nonexpressing U-2OS OS cells. To sum up, biglycan exhibits protective effects against the doxorubicin in MG63 OS cells by activating the Wnt signaling pathway and inhibiting autophagy.

ADCK1 is a potential therapeutic target of osteosarcoma

We here showed that ADCK1 (AarF domain-containing kinase 1), a mitochondrial protein, is upregulated in human osteosarcoma (OS) tissues and OS cells. In primary and established OS cells, ADCK1 shRNA or CRISPR/Cas9-induced ADCK1 knockout (KO) remarkably inhibited cell viability, proliferation and migration, and provoked apoptosis activation. Conversely, ectopic ADCK1 overexpression exerted pro-cancerous activity by promoting OS cell proliferation and migration. ADCK1 depletion disrupted mitochondrial functions in OS cells and induced mitochondrial membrane potential reduction, ATP depletion, reactive oxygen species production. Significantly, ADCK1 silencing augmented doxorubicin-induced apoptosis in primary OS cells. mTOR activation is important for ADCK1 expression in OS cells. The mTOR inhibitors, rapamycin and AZD2014, as well as mTOR shRNA, potently decreased ADCK1 expression in primary OS cells. In nude mice, the growth of subcutaneous pOS-1 xenografts was largely inhibited when bearing ADCK1 shRNA or ADCK1 KO construct. Moreover, ADCK1 KO largely inhibited pOS-1 xenograft in situ growth in proximal tibia of nude mice. ADCK1 depletion, apoptosis activation and ATP reduction were detected in pOS-1 xenografts bearing ADCK1 shRNA or ADCK1 KO construct. Together, the mitochondrial protein ADCK1 is required for OS cell growth and is a novel therapeutic target of OS.

Anti-EGFR Targeted Multifunctional I-131 Radio-Nanotherapeutic for Treating Osteosarcoma: In Vitro 3D Tumor Spheroid Model

The systemic delivery of doxorubicin (DOX) to treat osteosarcoma requires an adequate drug concentration to be effective, but in doing so, it raises the risk of increasing organ off-target toxicity and developing drug resistance. Herein, this study reveals a multiple therapeutic nanocarrier delivery platform that overcomes off-target toxicity by providing good specificity and imparting enhanced tumor penetration in a three-dimensional (3D) human MG-63 spheroid model. By synthesizing PEG-PLGA nanoparticles by the double emulsion method, encapsulating DOX and Na131I in the inner core, and conjugating with an epidermal growth factor receptor (EGFR) antibody, it is intended to specifically target human MG-63 cells. The nanocarrier is biocompatible with blood and has good stability characteristics. Na131I encapsulation efficiency was >96%, and radiochemical purity was >96% over 96 h. A DOX encapsulation efficacy of ~80% was achieved, with a drug loading efficiency of ~3%, and a sustained DOX release over 5 days. The nanocarrier EGFR antibody achieved a ~80-fold greater targeting efficacy to MG-63 cells (EGFR+) than fibroblast cells (EGFR−). The targeted multiple therapeutic DIE-NPs have a higher penetration and uptake of Na131I to the 3D model and a ~3-fold higher cytotoxicity than the DOX monotherapy (D-NPs). The co-administration of DOX and Na131I (DIE-NPs) disrupts DNA repair and generates free radicals resulting in DNA damage, triggering the activation of apoptosis pathways. This leads to inhibition of MG-63 cell proliferation and promotes cell cycle arrest in the G0/G1 phase. Furthermore, the PEGylated anti-EGFR functionalized DIE-NPs were found to be biocompatible with red blood cells and to have no adverse effects. This anti-EGFR targeted multifunctional I-131 radio-nanotherapeutic signifies a customizable specific targeted treatment for osteosarcoma.

Addressing Doxorubicin Resistance in Bone Sarcomas Using Novel Drug-Resistant Models

Bone sarcomas have not shown a significant improvement in survival for decades, due, in part, to the development of resistance to current systemic treatments, such as doxorubicin. To better understand those mechanisms mediating drug-resistance we generated three osteosarcoma and one chondrosarcoma cell lines with a stable doxorubicin-resistant phenotype, both in vitro and in vivo. These resistant strains include a pioneer model generated from a patient-derived chondrosarcoma line. The resistant phenotype was characterized by a weaker induction of apoptosis and DNA damage after doxorubicin treatment and a lower migratory capability. In addition, all resistant lines expressed higher levels of ABC pumps; meanwhile, no clear trends were found in the expression of anti-apoptotic and stem cell-related factors. Remarkably, upon the induction of resistance, the proliferation potential was reduced in osteosarcoma lines but enhanced in the chondrosarcoma model. The exposure of resistant lines to other anti-tumor drugs revealed an increased response to cisplatin and/or methotrexate in some models. Finally, the ability to retain the resistant phenotype in vivo was confirmed in an osteosarcoma model. Altogether, this work evidenced the co-existence of common and case-dependent phenotypic traits and mechanisms associated with the development of resistance to doxorubicin in bone sarcomas.

A Spheroid Model of Early and Late-Stage Osteosarcoma Mimicking the Divergent Relationship between Tumor Elimination and Bone Regeneration

Osteosarcoma is the most diagnosed bone tumor in children. The use of tissue engineering strategies after malignant tumor resection remains a subject of scientific controversy. As a result, there is limited research that focuses on bone regeneration postresection, which is further compromised following chemotherapy. This study aims to develop the first co-culture spheroid model for osteosarcoma, to understand the divergent relationship between tumor elimination and bone regeneration. By manipulating the ratio of stromal to osteosarcoma cells the modelled cancer state (early/late) is modified, as is evident by the increased tumor growth rates and an upregulation of a panel of well-established osteosarcoma prognostic genes. Validation of the authors' model is conducted by analyzing its ability to mimic the cytotoxic effects of the FDA-approved chemotherapeutic Doxorubicin. Next, the model is used to investigate what effect osteogenic supplements have, if any, on tumor growth. When their model is treated with osteogenic supplements, there is a stimulatory effect on the surrounding stromal cells. However, when treated with chemotherapeutics this stimulatory effect is significantly diminished. Together, the results of this study present a novel multicellular model of osteosarcoma and provide a unique platform for screening potential therapeutic options for osteosarcoma before conducting in vivo experiments.

Biglycan Interacts with Type I Insulin-like Receptor (IGF-IR) Signaling Pathway to Regulate Osteosarcoma Cell Growth and Response to Chemotherapy

Simple Summary

Osteosarcoma (OS) is an aggressive, primary bone cancer. OS cells produce altered osteoid whose components participate in signaling correlated to the development of this cancer. Biglycan (BGN), a proteoglycan, is correlated to aggressive OS type and resistance to chemotherapy. A constitutive signaling of insulin-like growth factor receptor I (IGF-IR) signaling in sarcoma progression was established. We showed that biglycan binds IGF-IR resulting in prolonged IGF-IR activation, nuclear translocation, and growth response of the poorly-differentiated MG63 cells correlated to increased aggressiveness markers expression and enhanced chemoresistance. This mechanism is not valid in moderately and well-differentiated, biglycan non-expressing U-2OS and Saos-2 OS cells.

Abstract

Osteosarcoma (OS) is a mesenchymally derived, aggressive bone cancer. OS cells produce an aberrant nonmineralized or partly mineralized extracellular matrix (ECM) whose components participate in signaling pathways connected to specific pathogenic phenotypes of this bone cancer. The expression of biglycan (BGN), a secreted small leucine-rich proteoglycan (SLRP), is correlated to aggressive OS phenotype and resistance to chemotherapy. A constitutive signaling of IGF-IR signaling input in sarcoma progression has been established. Here, we show that biglycan activates the IGF-IR signaling pathway to promote MG63 biglycan-secreting OS cell growth by forming a complex with the receptor. Computational models of IGF-IR and biglycan docking suggest that biglycan binds IGF-IR dimer via its concave surface. Our binding free energy calculations indicate the formation of a stable complex. Biglycan binding results in prolonged IGF-IR activation leading to protracted IGF-IR-dependent cell growth response of the poorly-differentiated MG63 cells. Moreover, biglycan facilitates the internalization (p ≤ 0.01, p ≤ 0.001) and sumoylation-enhanced nuclear translocation of IGF-IR (p ≤ 0.05) and its DNA binding in MG63 cells (p ≤ 0.001). The tyrosine kinase activity of the receptor mediates this mechanism. Furthermore, biglycan downregulates the expression of the tumor-suppressor gene, PTEN (p ≤ 0.01), and increases the expression of endothelial–mesenchymal transition (EMT) and aggressiveness markers vimentin (p ≤ 0.01) and fibronectin (p ≤ 0.01) in MG63 cells. Interestingly, this mechanism is not valid in moderately and well-differentiated, biglycan non-expressing U-2OS and Saos-2 OS cells. Furthermore, biglycan exhibits protective effects against the chemotherapeutic drug, doxorubicin, in MG63 OS cells (p ≤ 0.01). In conclusion, these data indicate a potential direct and adjunct therapeutical role of biglycan in osteosarcoma.

Exosomal Long Non-Coding RNA ANCR Mediates Drug Resistance in Osteosarcoma

Osteosarcoma (OS) is rare cancer with bimodal age distribution with peaks observed in children and young adults. Typically, OS is treated with pre-surgery neoadjuvant therapy, surgical excision, and post-surgery chemotherapy. However, the efficacy of treatment on disease prognosis and objective response is not currently optimal, often resulting in drug resistance; in turn, highlighting the need to understand mechanisms driving resistance to therapy in OS patients. Using Doxycycline (Dox)-sensitive and resistant variants of OS cells lines KHOS and U2OS, we found that the resistant variants KHOS-DR and U2OS-DR have significantly higher in vitro proliferation. Treating the Dox-sensitive KHOS/U2OS cells with exosomes isolated from KHOS-DR/U2OS-DR made them resistant to treatment with Dox in vitro and in vivo and enhanced tumor growth and progression, while decreasing overall survival. Expression of the long non-coding RNA (lncRNA) ANCR was significantly higher in the KHOS-DR and U2OS-DR variants. SiRNA-mediated knockdown of ANCR decreased in vitro proliferation, while increasing sensitivity to Dox treatment in the KHOS-DR/U2OS-DR cells. Expression of the exosomal lncRNA ANCR was critical for drug resistance and OS tumor progression in xenografts and was correlated to resistance to Adriamycin and overall survival is patients with OS. These results establish lncRNA ANCR as a critical mediator of resistance to therapy in OS patients, highlighting it as a potential therapeutic target in OS patients.

Development of a Nomogram for Predicting the Efficacy of Preoperative Chemotherapy in Osteosarcoma

Background

Due to the obvious heterogeneity of osteosarcoma, many patients are not sensitive to neoadjuvant chemotherapy. In this study, the clinical characteristics and auxiliary examinations of patients with osteosarcoma were used to predict the effect of preoperative chemotherapy, so as to guide the clinical adjustment of the treatment plan to improve the prognosis of patients.

Methods

In this study, 90 patients with pathologically confirmed osteosarcoma were included, and they were randomly divided into training cohort (n=45) and validation cohort (n=45). A prediction model of preoperative chemotherapy efficacy for osteosarcoma was established by multivariate logistic regression analysis, and a nomogram was used as the visualization of the model. The ROC curve and C-index were used to evaluate the accuracy of the nomogram. Decision curve analysis (DCA) was used to evaluate the net benefit of the nomogram in predicting the efficacy of neoadjuvant chemotherapy under different threshold probabilities.

Results

In the study, the age, gender, location, tumor volume, metastasis at the first visit, MSTS staging, C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), alkaline phosphatase (ALP), and lactate dehydrogenase (LDH) were used in the multivariate logistic regression analysis and the construction of the nomogram. The AUC and C-index of the training cohort were 0.793 (95% CI: 0.632, 0.954) and 0.881 (95% CI: 0.776, 0.986), respectively. The AUC and C-index in the validation cohort were 0.791 (95% CI: 0.644, 0.938) and 0.813 (95% CI: 0.679, 0.947), respectively, which were close to the training cohort. DCA showed that the model had good clinical application value.

Conclusion

Based on the clinical characteristics of patients and auxiliary examinations, the nomogram can be good used to predict the efficacy of preoperative chemotherapy for osteosarcoma.

Recent Advances in the Treatment of Bone Metastases and Primary Bone Tumors: An Up-to-Date Review

In the last decades, the treatment of primary and secondary bone tumors has faced a slow-down in its development, being mainly based on chemotherapy, radiotherapy, and surgical interventions. However, these conventional therapeutic strategies present a series of disadvantages (e.g., multidrug resistance, tumor recurrence, severe side effects, formation of large bone defects), which limit their application and efficacy. In recent years, these procedures were combined with several adjuvant therapies, with different degrees of success. To overcome the drawbacks of current therapies and improve treatment outcomes, other strategies started being investigated, like carrier-mediated drug delivery, bone substitutes for repairing bone defects, and multifunctional scaffolds with bone tissue regeneration and antitumor properties. Thus, this paper aims to present the types of bone tumors and their current treatment approaches, further focusing on the recent advances in new therapeutic alternatives.

3',4'-Dihydroxyflavonol Modulates the Cell Cycle in Cancer Cells: Implication as a Potential Combination Drug in Osteosarcoma

New agents are demanded to increase the therapeutic options for osteosarcoma (OS). Although OS is the most common bone cancer in children and adolescents, it is considered a rare disorder. Therefore, finding adjuvant drugs has potential to advance therapy for this disease. In this study, 3′,4′-dihydroxyflavonol (DiOHF) was investigated to assess the effects in OS cellular models in combination with doxorubicin (Dox). MG-63 and U2OS human OS cells were exposed to DiOHF and Dox and tested for cell viability and growth. To elucidate the inhibitory effects of DiOHF, additional studies were conducted to assess apoptosis and cell cycle distribution, gene expression quantification of cell cycle regulators, and cytokinesis-block cytome assay to determine nuclear division rate. DiOHF decreased OS cell growth and viability in a concentration-dependent manner. Its combination with Dox enabled Dox dose reduction in both cell lines, with synergistic interactions in U2OS cells. Although no significant apoptotic effects were detected at low concentrations, cytostatic effects were demonstrated in both cell lines. Incubation with DiOHF altered cell cycle dynamics and resulted in differential cyclin and cyclin-dependent kinase expression. Overall, this study presents an antiproliferative action of DiOHF in OS combination therapy via modulation of the cell cycle and nuclear division.

Mitochondria-targeting graphene oxide nanocomposites for fluorescence imaging-guided synergistic phototherapy of drug-resistant osteosarcoma

BACKGROUND

Osteosarcoma (OS) is the most common primary malignant bone tumor occurring in children and young adults. Drug-resistant osteosarcoma often results in chemotherapy failure. Therefore, new treatments aimed at novel therapeutic targets are urgently needed for the treatment of drug-resistant osteosarcoma. Mitochondria-targeted phototherapy, i.e., synergistic photodynamic/photothermal therapy, has emerged as a highly promising strategy for treating drug-resistant tumors. This study proposed a new nano-drug delivery system based on near-infrared imaging and multifunctional graphene, which can target mitochondria and show synergistic phototherapy, with preferential accumulation in tumors.

METHODS AND RESULTS

Based on our previous study, (4-carboxybutyl) triphenyl phosphonium bromide (TPP), a mitochondria-targeting ligand, was conjugated to indocyanine green (ICG)-loaded, polyethylenimine-modified PEGylated nanographene oxide sheets (TPP-PPG@ICG) to promote mitochondrial accumulation after cellular internalization. Thereafter, exposure to a single dose of near-infrared irradiation enabled synergistic photodynamic and photothermal therapy, which simultaneously inhibited adenosine triphosphate synthesis and mitochondrial function. Induction of intrinsic apoptosis assisted in surmounting drug resistance and caused tumor cell death. After fluorescence imaging-guided synergistic phototherapy, the mitochondria-targeting, multifunctional graphene-based, drug-delivery system showed highly selective anticancer efficiency in vitro and in vivo, resulting in marked inhibition of tumor progression without noticeable toxicity in mice bearing doxorubicin-resistant MG63 tumor cells.

CONCLUSION

The mitochondria-targeting TPP-PPG@ICG nanocomposite constitutes a new class of nanomedicine for fluorescence imaging-guided synergistic phototherapy and shows promise for treating drug-resistant osteosarcoma.

LINC01116 Promotes Doxorubicin Resistance in Osteosarcoma by Epigenetically Silencing miR-424-5p and Inducing Epithelial-Mesenchymal Transition

Background: Development of resistance to doxorubicin-based chemotherapy limits its curative effect in osteosarcoma. In the current study, we focused on investigating the mechanisms underlying the development of doxorubicin resistance in osteosarcoma.

Methods: The human osteosarcoma cell line MG-63 and doxorubicin-resistant MG-63/Dox cells were used in this study. Quantitative real-time polymerase chain reaction (qRT-PCR) was used to detect the expression of the long non-coding RNA LINC01116 in the two cell lines. Then, the specific shRNA for LINC01116 was employed to suppress LINC01116 expression in MG-63/Dox cells. Cell viability was assessed by the CCK-8 and colony formation assays. Cell migration and invasion were evaluated by the transwell assay. Moreover, the epithelial-mesenchymal transition (EMT)-related proteins, E-cadherin, vimentin, and N-cadherin were evaluated by Western blotting. The regulation of LINC01116 on miR-424-5p expression was examined using methylation-specific PCR, RNA immunoprecipitation, and Western blotting assay. The potential targeting of HMGA2 by miR-424-5p was predicted using the bioinformatics databases TargetScan and miRanda and verified by a dual-luciferase reporter assay.

Results: LINC01116 was more highly expressed in MG-63/Dox cells than in MG-63 cells. Inhibition of LINC01116 suppressed cell viability, migration, and invasion, along with upregulating the expression of E-cadherin, downregulating vimentin, and attenuating doxorubicin resistance in MG-63/Dox cells. Further mechanism-related investigations indicated that LINC01116 regulated HMGA2 expression via the EZH2-associated silencing of miR-424-5p.

Conclusion: LINC01116 exerts regulatory effects on doxorubicin resistance through the miR-424-5p axis, providing a potential approach to overcoming chemoresistance in osteosarcoma.

Pioglitazone modulates doxorubicin resistance in a in vivo model of drug resistant osteosarcoma xenograft

Osteosarcoma has been reported with treatment failure in up to 40% of cases. Our laboratory had identified genes involved in the PPARγ pathway to be associated with doxorubicin (DOX) resistance. We hence used PPARγ agonist pioglitazone (PIO) to modulate DOX resistance. DOX-resistant cell line (143B-DOX) was developed by gradient exposure to DOX. The cytotoxicity to PIO and in combination with DOX was assayed in vitro, followed by HPLC to estimate the metabolites of PIO in the presence of microsomes (HLMs). Gene expression studies revealed the mechanism behind the cytotoxicity of PIO. Further, the effects were evaluated in mice bearing 143B-DOX tumors treated either with PIO (20 mg/kg/p.o or 40 mg/kg/p.o Q1D) alone or in combination with DOX (0.5 mg/kg/i.p Q2W). 143B-DOX was 50-fold resistant over parental cells. While PIO did not show any activity on its own, the addition of HLMs to the cells in culture showed over 80% cell kill within 24 h, possibly due to the metabolites of PIO as determined by HPLC. In combination with DOX, PIO had shown synergistic activity. Additionally, cytotoxicity assay in the presence of HLMs revealed that PIO on its own showed promising activity compared to its metabolites-hydroxy pioglitazone and keto pioglitazone. In vivo studies demonstrated that treatment with 40 mg/kg/p.o PIO alone showed significant activity, followed by a combination with DOX. Gene expression studies revealed that PIO could modulate drug resistance by downregulating MDR1 and IL8. Our study suggests that PIO can modulate DOX resistance in osteosarcoma cells.

Notoginsenoside R1 counteracts mesenchymal stem cell-evoked oncogenesis and doxorubicin resistance in osteosarcoma cells by blocking IL-6 secretion-induced JAK2/STAT3 signaling

Tumor microenvironment is a critical participant in the initiation, progression and drug resistance of carcinomas, including osteosarcoma. Notoginsenoside R1 (NGR1) is a proverbial active ingredient of the traditional Chinese medicine Panax notoginseng (PN) and possess undeniable roles in several cancers. Nevertheless, its function in osteosarcoma and tumor microenvironment remains elusive. In the current study, exposure to NGR1 dose-dependently inhibited osteosarcoma cell viability and migration, and induced apoptosis. Furthermore, osteosarcoma cells that were incubated with conditioned medium (CM) from bone marrow mesenchymal stem cells (BMSCs) exhibited greater proliferation, migration capacity and MMP-2 and MMP-9 expression relative to control cells, which was reversed when BMSCs were treated with NGR1. Notably, administration with NGR1 antagonized CM-evoked doxorubicin resistance in osteosarcoma cells by decreasing cell viability and increasing cell apoptosis and caspase-3/9 activity. Mechanically, NGR1 suppressed IL-6 secretion from BMSCs, as well as the subsequent activation of the JAK2/STAT3 signaling in osteosarcoma cells. In addition, blocking the JAK2 pathway by its antagonist AG490 reversed CM-induced osteosarcoma cell proliferation, migration and doxorubicin resistance. Moreover, exogenous supplementation with IL-6 engendered not only the reactivation of the JAK2/STAT3 signaling but also muted NGR1-mediated efficacy against osteosarcoma cell malignancy and doxorubicin resistance. Collectively, NGR1 may directly restrain osteosarcoma cell growth and migration, or indirectly antagonize MSC-evoked malignancy and drug resistance by interdicting IL-6 secretion-evoked activation of the JAK2/STAT3 pathway. Consequently, the current study may highlight a promising therapeutic strategy against osteosarcoma by regulating tumor cells and the tumor microenvironment.

Triptonide Modulates MAPK Signaling Pathways and Exerts Anticancer Effects via ER Stress-Mediated Apoptosis Induction in Human Osteosarcoma Cells

Background

Osteosarcoma (OS) is the most common primary malignancy arise from bone and is one of the causes of cancer-related deaths. Triptonide (TN), a diterpenoid epoxide presented in Tripterygium wilfordii, is shown to possess a broad spectrum of biological properties.

Methods

In this study, we investigate the growth inhibitory effect of TN against human OS cells and its underlying molecular mechanism of action.

Results

Findings of our in vitro study revealed that TN exhibited a dose-dependent cytotoxic effect in MG63 and U-2OS cells. ROS-mediated cytotoxic effect was achieved in OS cells treated with TN which was reversed upon NAC treatment. Significantly, increased expression of PERK, p-EIF2, GRP78, ATF4 and CHOP in TN-treated OS cells unfolds the molecular mechanism of TN targets ER stress-mediated apoptosis. Modulation of ERK MAPK pathway was also observed as evidenced by the increased phosphorylation of ERK (p-ERK) and p-p38 in TN-treated OS cells.

Conclusion

Altogether, the outcome of the study for the first time revealed that TN exhibited its potential chemotherapeutic effects through ROS-mediated ER stress-induced apoptosis via p38 and ERK MAPK signaling pathways.

Small Nucleolar RNAs Determine Resistance to Doxorubicin in Human Osteosarcoma

Doxorubicin (Dox) is one of the most important first-line drugs used in osteosarcoma therapy. Multiple and not fully clarified mechanisms, however, determine resistance to Dox. With the aim of identifying new markers associated with Dox-resistance, we found a global up-regulation of small nucleolar RNAs (snoRNAs) in human Dox-resistant osteosarcoma cells. We investigated if and how snoRNAs are linked to resistance. After RT-PCR validation of snoRNAs up-regulated in osteosarcoma cells with different degrees of resistance to Dox, we overexpressed them in Dox-sensitive cells. We then evaluated Dox cytotoxicity and changes in genes relevant for osteosarcoma pathogenesis by PCR arrays. SNORD3A, SNORA13 and SNORA28 reduced Dox-cytotoxicity when over-expressed in Dox-sensitive cells. In these cells, GADD45A and MYC were up-regulated, TOP2A was down-regulated. The same profile was detected in cells with acquired resistance to Dox. GADD45A/MYC-silencing and TOP2A-over-expression counteracted the resistance to Dox induced by snoRNAs. We reported for the first time that snoRNAs induce resistance to Dox in human osteosarcoma, by modulating the expression of genes involved in DNA damaging sensing, DNA repair, ribosome biogenesis, and proliferation. Targeting snoRNAs or down-stream genes may open new treatment perspectives in chemoresistant osteosarcomas.

Hyaluronated liposomes containing H2S-releasing doxorubicin are effective against P-glycoprotein-positive/doxorubicin-resistant osteosarcoma cells and xenografts

Doxorubicin (dox) is one of the first-line drug in osteosarcoma treatment but its effectiveness is limited by the efflux pump P-glycoprotein (Pgp) and by the onset of cardiotoxicity. We previously demonstrated that synthetic doxs conjugated with a H₂S-releasing moiety (Sdox) were less cardiotoxic and more effective than dox against Pgp-overexpressing osteosarcoma cells. In order to increase the active delivery to tumor cells, we produced hyaluronic acid (HA)-conjugated liposomes containing Sdox (HA-Lsdox), exploiting the abundance of the HA receptor CD44 in osteosarcoma. HA-Lsdox showed favorable drug-release profile and higher toxicity in vitro and in vivo than dox or the FDA-approved liposomal dox Caelyx^® against Pgp-overexpressing osteosarcoma, displaying the same cardiotoxicity profile of Caelyx^®. Differently from dox, HA-Lsdox delivered the drug within the endoplasmic reticulum (ER), inducing protein sulfhydration and ubiquitination, and activating a ER stress pro-apoptotic response mediated by CHOP. HA-Lsdox also sulfhydrated the nascent Pgp in the ER, reducing its activity. We propose HA-Lsdox as an innovative tool noteworthy to be tested in Pgp-overexpressing patients, who are frequently less responsive to standard treatments in which dox is one of the most important drugs.

Endoplasmic reticulum-targeting doxorubicin: a new tool effective against doxorubicin-resistant osteosarcoma

Doxorubicin is one of the most effective drugs for the first-line treatment of high-grade osteosarcoma. Several studies have demonstrated that the major cause for doxorubicin resistance in osteosarcoma is the increased expression of the drug efflux transporter ABCB1/P-glycoprotein (Pgp). We recently identified a library of H2S-releasing doxorubicins (Sdox) that were more effective than doxorubicin against resistant osteosarcoma cells. Here we investigated the molecular mechanisms of the higher efficacy of Sdox in human osteosarcoma cells with increasing resistance to doxorubicin. Differently from doxorubicin, Sdox preferentially accumulated within the endoplasmic reticulum (ER), and its accumulation was only modestly reduced in Pgp-expressing osteosarcoma cells. The increase in doxorubicin resistance was paralleled by the progressive down-regulation of genes of ER-associated protein degradation/ER-quality control (ERAD/ERQC), two processes that remove misfolded proteins and protect cell from ER stress-triggered apoptosis. Sdox, that sulfhydrated ER-associated proteins and promoted their subsequent ubiquitination, up-regulated ERAD/ERQC genes. This up-regulation, however, was insufficient to protect cells, since Sdox activated ER stress-dependent apoptotic pathways, e.g., the C/EBP-β LIP/CHOP/PUMA/caspases 12-7-3 axis. Sdox also promoted the sulfhydration of Pgp that was subsequently ubiquitinated: this process further enhanced Sdox retention and toxicity in resistant cells. Our work suggests that Sdox overcomes doxorubicin resistance in osteosarcoma cells by at least two mechanisms: it induces the degradation of Pgp following its sulfhydration and produces a huge misfolding of ER-associated proteins, triggering ER-dependent apoptosis. Sdox may represent the prototype of innovative anthracyclines, effective against doxorubicin-resistant/Pgp-expressing osteosarcoma cells by perturbing the ER functions.

Functionalized Keratin as Nanotechnology-Based Drug Delivery System for the Pharmacological Treatment of Osteosarcoma

Osteosarcoma therapy might be moving toward nanotechnology-based drug delivery systems to reduce the cytotoxicity of antineoplastic drugs and improve their pharmacokinetics. In this paper, we present, for the first time, an extensive chemical and in vitro characterization of dual-loaded photo- and chemo-active keratin nanoparticles as a novel drug delivery system to treat osteosarcoma. The nanoparticles are prepared from high molecular weight and hydrosoluble keratin, suitably functionalized with the photosensitizer Chlorin-e6 (Ce6) and then loaded with the chemotherapeutic drug Paclitaxel (PTX). This multi-modal PTX-Ce6@Ker nanoformulation is prepared by both drug-induced aggregation and desolvation methods, and a comprehensive physicochemical characterization is performed. PTX-Ce6@Ker efficacy is tested on osteosarcoma tumor cell lines, including chemo-resistant cells, using 2D and 3D model systems. The single and combined contributions of PTX and Ce6 is evaluated, and results show that PTX retains its activity while being vehiculated through keratin. Moreover, PTX and Ce6 act in an additive manner, demonstrating that the combination of the cytostatic blockage of PTX and the oxidative damage of ROS upon light irradiation have a far superior effect compared to singularly administered PTX or Ce6. Our findings provide the proof of principle for the development of a novel, nanotechnology-based drug delivery system for the treatment of osteosarcoma.

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.

SOX2OT variant 7 contributes to the synergistic interaction between EGCG and Doxorubicin to kill osteosarcoma via autophagy and stemness inhibition

BACKGROUND

Doxorubicin is the preferred chemotherapeuticdrug for osteosarcoma treatment of which clinical efficacy is limited because of its chemo-resistance and cardiac toxicity. It is necessary to develop the combination regimen with complementary molecular mechanisms to reduce the side effects and enhance sensitivity of Doxorubicin. EGCG is a polyphenol in green tea with antitumor bioactivity,which has been found that its combination with certain chemotherapeutic drugs could improve the antitumor efficiency.

METHODS

In this study, MTT assay was used to detect the cell growth inhibition The CD133+/CD44+ cells were isolated from U2OS and SaoS2 cell lines using magnetic-activated cell sorting and identified by flow cytometry analysis. qRT-PCR was used for determining the relative mRNA levels of key genes. Immunofluorescence was performed to evaluate the autophagy flux alterations. Self-renewal ability was accessed by sphere-forming assay. Tumorigenicity in nude mice was preformed to evaluate tumorigenicity in vivo.

RESULTS

We found that EGCG targeting LncRNA SOX2OT variant 7 produced synergistic effects with Doxorubicin on osteosarcoma cell growth inhibition. On the one hand, EGCG could reduce the Doxorubicin-induced pro-survival autophagy through decreasing SOX2OT variant 7 to improve the growth inhibition of Doxorubicin. On the other hand, EGCG could partially inactivate Notch3/DLL3 signaling cascade targeting SOX2OT variant 7 to reduce the stemness then abated drug-resistance of osteosarcoma cells.

CONCLUSIONS

This study will help to reveal the molecular mechanisms of synergistic effects of EGCG and Doxorubicin on OS chemotherapy and improve the clinical efficacy of chemotherapy as well as provide a basis for developing antitumor drugs targeting osteosarcoma stem cells.

Alginate Oligosaccharide DP5 Exhibits Antitumor Effects in Osteosarcoma Patients following Surgery

Osteosarcoma is a malignant musculoskeletal tumor that has high-rate morbidity and mortality worldwide. Alginate oligosaccharide (AOS), a natural product, has antitumor activities and may have therapeutic effects in osteosarcoma, the molecular mechanisms of which remain unclear. AOS was prepared from alginate sodium using alginate lyase. The fractions of AOS were further isolated by size-exclusion chromatography and verified by electrospray ionization mass spectrometry (ESI-MS). Osteosarcoma patients were enrolled in the study and assigned into two groups: AOS (AG, oral administration of 10-mg AOS daily) and control groups (CG, placebo). Preoperative and postoperative clinical data were investigated and analyzed. Four different degrees of polymerizations (DPs) were isolated and denominated as DP2, DP3, DP4, and DP5. Among these polymers, only DP5 showed antitumor functions on osteosarcoma cells. Before surgery and the outcome of primary end point after surgery, no significant differences were observed for clinical data and tumor size between the AG and CG groups (P > 0.05). After 2-year therapy, the mean tumor volume was 214.6 ± 145.7 c.c. in AG and 467.2 ± 225.3 c.c in CG (P < 0.01). The rate of local recurrence was 44.9 and 68.7% in AG and CG, respectively (P < 0.01). AOS treatment resulted in the increase in serum levels of SOD, GSH, HDL-C, and reduction in the levels of interleukin-1 (IL-1) beta and IL-6; the ratios of AST/ALT; and triglycerides, total cholesterol (TC), low-density lipoprotein cholesterol LDL-C, and malondialdehyde (MDA) (P < 0.05). AOS reduces osteosarcoma progression, which is associated with improvement in antioxidant and anti-inflammatory capacities of patients, and may be used as a potential drug for osteosarcoma therapy.