Advances in osteosarcoma stem cell research and opportunities for novel therapeutic targets

A GAD1 inhibitor suppresses osteosarcoma growth through the Wnt/β-catenin signaling pathway

Background

As a marker of the GABAergic system, the expression of glutamate decarboxylase 1 (GAD1) is mainly restricted to the central nervous system. Emerging studies have shown that aberrant expression of GAD1 in tumor tissues may promote tumor cell growth. The role of GAD1 in the development of osteosarcoma (OS) remains unclear, so this study sought to investigate the expression status of GAD1 and the effect of its specific inhibitor 3-mercaptopropionic acid (3-MPA) on OS.

Methods

The R2 database was used to analyze the relationship between the expression of GAD1 and clinical prognosis in OS patients. Immunohistochemistry was used to compare the expression profile of GAD1 between OS and matched neighboring tissues. The potential antitumor effects of 3-MPA on cell viability, colony formation and the cell cycle were examined. Moreover, the in vivo effect of 3-MPA on tumor growth was investigated using tumor-bearing nude mice.

Results

The expression level of GAD1 was aberrantly upregulated in OS tissues, but almost no expression of GAD1 was found in matched neighboring tissues. Western blotting analyses showed upregulation of GAD1 in OS cells compared to human osteoblast cells. In vitro and in vivo, 3-MPA significantly suppressed the growth of OS. Regarding the mechanism, 3-MPA inhibited β-catenin and cyclin D1 in OS cells, thereby inactivating the Wnt/β-catenin pathway.

Conclusions

OS displays increased expression of the GABAergic neuronal marker GAD1, and 3-MPA significantly reduces OS growth by inhibiting the Wnt/β-catenin pathway.

Role of proteoglycan synthesis genes in osteosarcoma stem cells

Osteosarcoma stem cells (OSCs) contribute to the pathogenesis of osteosarcoma (OS), which is the most common malignant primary bone tumor. The significance and underlying mechanisms of action of proteoglycans (PGs) and glycosaminoglycans (GAGs) in OSC phenotypes and OS malignancy are largely unknown. This study aimed to investigate the role of PG/GAG biosynthesis and the corresponding candidate genes in OSCs and poor clinical outcomes in OS using scRNA-seq and bulk RNA-seq datasets of clinical OS specimens, accompanied by biological validation by in vitro genetic and pharmacological analyses. The expression of β-1,3-glucuronyltransferase 3 (B3GAT3), one of the genes responsible for the biosynthesis of the common core tetrasaccharide linker region of PGs, was significantly upregulated in both OSC populations and OS tissues and was associated with poor survival in patients with OS with high stem cell properties. Moreover, the genetic inactivation of B3GAT3 by RNA interference and pharmacological inhibition of PG biosynthesis abrogated the self-renewal potential of OSCs. Collectively, these findings suggest a pivotal role for B3GAT3 and PG/GAG biosynthesis in the regulation of OSC phenotypes and OS malignancy, thereby providing a potential target for OSC-directed therapy.

miR-1293 suppresses osteosarcoma progression by modulating drug sensitivity in response to cisplatin treatment

Chemotherapy is considered the primary treatment for osteosarcoma. however, its effectiveness is limited due to drug resistance and toxicity. Thus, identifying novel therapeutic targets to enhance the efficacy of chemotherapy is urgently needed. Here, we identified a novel cisplatin-sensitivity enhancing mechanism via up-regulation of the tumour suppressor gene, miR-1293. Meanwhile, higher levels of miR-1293 observed in prechemotherapy patients were associated with a more favorable prognosis. The mechanism underlying cisplatin upregulated miR-1293 expression involves hypomethylation of the miR-1293 promoter, which blocks the binding of the transcription repressor TFAP2A to the promoter. Furthermore, miR-1293 inhibits osteosarcoma progression by targeting TIMP1 to inactivate the Notch1/Hes1 and TGFBR1/Smad2/3 pathways, thereby promoting tumour cell death. The findings presented herein unveil a novel mechanism for enhancing cisplatin sensitivity and proposed a potential therapeutic strategy for osteosarcoma through pre-chemotherapy supplementation of miR-1293.

Identification and prognostic evaluation of differentially expressed long noncoding RNAs associated with immune infiltration in osteosarcoma

Osteosarcoma is a malignant bone cancer that originates from the bone with the strongest invasiveness. Tumor formation strongly correlates with immune cell infiltration into the tumor immune microenvironment (TIME). Therefore, we aimed to identify TIME-related biomarkers as potential prognostic markers of osteosarcoma. The mRNA and long noncoding RNA (lncRNA) transcriptome data of 88 patients with osteosarcoma and the expression profile of GSE99671 were downloaded from The Cancer Genome Atlas and Gene Expression Omnibus, respectively. Immune infiltration scores and types were evaluated using ESTIMATE and CIBERSORT. A linear model was established to identify the differentially expressed genes (DEGs) and lncRNAs (DElncRNAs). Functional enrichment analysis of DEGs was conducted by Gene Ontology, Kyoto Encyclopedia of Genes and Genomes, gene set enrichment analysis, and gene set variation analysis. DElncRNAs were analyzed using a weighted gene co-expression network. Least absolute shrinkage and selection operator regression was applied to screen for prognostic markers. Patient survival was predicted by the risk score and analyzed by receiver operating characteristic curve. Clinical features affecting patient survival were assessed. Immune infiltration positively correlated with osteosarcoma patient survival. Different immune cell infiltrates in patients with osteosarcma may serve as prognostic indicators and targets for immunotherapy. In total, 1125 DEGs, 80 DElncRNAs, and 11 pairs of co-expressed lncRNA-mRNAs were identified. DEGs in the three modules were associated with immune infiltration into the TIME. Four DElncRNAs, namely AC015819.1, AC015911.3, AL365361.1, and USP30-AS1, showed good prognostic ability for osteosarcoma and were positively correlated with the immune score. Tumor metastasis and risk scores alone were good prognostic indicators, and a combination of the two variables can better predict the prognosis of osteosarcoma. We identified four lncRNAs, AC015819.1, AC015911.3, AL365361.1, and USP30-AS1, as potential biomarkers for osteosarcoma prognosis.

A tumor suppressor protein encoded by circKEAP1 inhibits osteosarcoma cell stemness and metastasis by promoting vimentin proteasome degradation and activating anti-tumor immunity

BACKGROUND

Osteosarcoma (OS) is one of most commonly diagnosed bone cancer. Circular RNAs (circRNAs) are a class of highly stable non-coding RNA, the majority of which have not been characterized functionally. The underlying function and molecular mechanisms of circRNAs in OS have not been fully demonstrated.

METHOD

Microarray analysis was performed to identify circRNAs that are differentially-expressed between OS and corresponding normal tissues. The biological function of circKEAP1 was confirmed in vitro and in vivo. Mass spectrometry and western blot assays were used to identify the circKEAP1-encoded protein KEAP1-259aa. The molecular mechanism of circKEAP1 was investigated by RNA sequencing and RNA immunoprecipitation analyses.

RESULTS

Here, we identified a tumor suppressor circKEAP1, originating from the back-splicing of exon2 of the KEAP1 gene. Clinically, circKEAP1 is downregulated in OS tumors and associated with better survival in cancer patients. N6-methyladenosine (m6A) at a specific adenosine leads to low expression of circKEAP1. Further analysis revealed that circKEAP1 contained a 777 nt long ORF and encoded a truncated protein KEAP1-259aa that reduces cell proliferation, invasion and tumorsphere formation of OS cells. Mechanistically, KEAP1-259aa bound to vimentin in the cytoplasm to promote vimentin proteasome degradation by interacting with the E3 ligase ARIH1. Moreover, circKEAP1 interacted with RIG-I to activate anti-tumor immunity via the IFN-γ pathway.

CONCLUSION

Taken together, our findings characterize a tumor suppressor circKEAP1 as a key tumor suppressor regulating of OS cell stemness, proliferation and migration, providing potential therapeutic targets for treatment of OS.

Amplified Ferroptosis and Apoptosis Facilitated by Differentiation Therapy Efficiently Suppress the Progression of Osteosarcoma

Osteosarcoma (OS) is the most frequent osseous neoplasm among young people aged 10-20. Currently, the leading treatment for osteosarcoma is a combination of surgery and chemotherapy. However, the mortality remains high due to chemoresistance, metastasis, and recurrence, attributing to the existence of cancer stem cells (CSCs) as reported. To target CSCs, differentiation therapy attracts increasing attention, inducing CSCs to bulk tumor cells with elevated reactive oxygen species (ROS) levels and less chemoresistance. Moreover, increasing studies have implied that ferroptosis is a promising approach to eliminating cancer cells through eliciting oxidative damage and subsequent apoptosis, effectively bypassing chemoresistance. Here, a cancer-cell-membrane-decorated biocompatible formulation (GA-Fe@CMRALi liposome) is constructed to combat OS efficiently by combining distinct differentiation and ferroptosis therapies through magnified ROS-triggered ferroptosis and apoptosis with homologous target capability to tumor sites. The combinational approach exhibited favorable therapeutic efficacy against OS in vitro and in vivo. Impressively, the potential mechanisms are revealed by mRNA sequencing. This study provides a tactical design and typical paradigm of the synergized differentiation and ferroptosis therapies to combat heterogeneous OS.

LRPPRC regulates malignant behaviors, protects mitochondrial homeostasis, mitochondrial function in osteosarcoma and derived cancer stem-like cells

BACKGROUND

Leucine-rich pentatricopeptide repeat containing (LRPPRC) is a potential oncogene in multiple tumor types, including lung adenocarcinoma, esophageal squamous cell carcinoma and gastric cancer. LRPPRC exerts its tumor-promoting effects mainly by regulating mitochondrial homeostasis and inducing oxidative stress. However, the exact role and mechanisms by which LRPPRC acts in osteosarcoma and osteosarcoma-derived cancer stem-like cells (CSCs), which potentially critically contribute to recurrence, metastasis and chemoresistance, are still largely unclear.

METHODS

LRPPRC level in osteosarcoma cells and CSCs were detected by western blot. Effects of LRPPRC on CSCs were accessed after LRPPRC knockdown by introducing lentivirus containing shRNA targeting to LRPPRC mRNA.

RESULTS

we found that LRPPRC was highly expressed in several osteosarcoma cell lines and that LRPPRC knockdown inhibited malignant behaviors, including proliferation, invasion, colony formation and tumor formation, in MG63 and U2OS cells. Enriched CSCs derived from MG63 and U2OS cells presented upregulated LRPPRC levels compared to parental cells (PCs), and LRPPRC knockdown markedly decreased the sphere-forming capacity. These findings demonstrate that LRPPRC knockdown decreased stemness in CSCs. Consistent with a previous report, LRPPRC knockdown decreased the expression levels of FOXM1 and its downstream target genes, including PRDX3, MnSOD and catalase, which are responsible for scavenging reactive oxygen species (ROS). Expectedly, LRPPRC knockdown increased the accumulation of ROS in osteosarcoma and osteosarcoma-derived CSCs under hypoxic conditions due to the decrease in ROS scavenging proteins. Moreover, LRPPRC knockdown sensitized osteosarcomas and CSCs against carboplatin, a ROS-inducing chemoagent, and promoted apoptosis. Furthermore, LRPPRC knockdown significantly decreased the mitochondrial membrane potential, disturbed mitochondrial homeostasis and led to mitochondrial dysfunction.

CONCLUSION

Taken together, these findings indicated that LRPPRC exerts critical roles in regulating mitochondrial homeostasis, mitochondrial function and tumorigenesis in osteosarcomas and osteosarcoma-derived CSCs. This suggests that LRPPRC might be a promising therapeutic target for osteosarcomas.

Prognostic and immunological significance of an M1 macrophage-related gene signature in osteosarcoma

As the most abundant infiltrating immune cells in the tumor microenvironment (TME), tumor-associated macrophages (TAMs) are pivotal in tumor development and treatment. The present investigation endeavors to explore the potential of M1 macrophage-related genes (MRGs) as biomarkers for assessing risk in individuals with osteosarcoma. RNA-sequence data and clinical data were derived from TCGA and GEO databases. The CIBERSORT method was utilized to discern subtypes of tumor-infiltrating immune cells. Identification of MRGs was achieved through Pearson correlation analysis. A prognostic risk model for MRGs was developed using Cox and LASSO regression analyses. A tripartite gene signature comprising CD37, GABRD, and ARHGAP25 was an independent prognostic indicator and was employed to develop a risk score model. The internal and external validation cohort confirmed the results. The area under the ROC curve (AUC) was determined for survival periods of 1 year, three years, and five years, yielding values of 0.746, 0.839, and 0.850, respectively. The C-index of the risk score was found to be superior to clinicopathological factors. GO/KEGG enrichment showed that the differences between high- and low-risk groups were predominantly associated with immune response pathways. Immune-related analysis related to proportions of immune cells, immune function, and expression levels of immune checkpoint genes all showed differences between the high- and low-risk groups. The qRT-PCR and Western blotting results indicate that CD37 expression was markedly higher in MG63 and U2OS cell lines when compared to normal osteoblast hFOB1.19. In U2OS cell line, GABRD expression levels were significantly upregulated. ARHGAP25 expression levels were elevated in both 143B and U2OS cell lines. In summary, utilizing a macrophage genes signature demonstrates efficacy in predicting both the prognosis and therapy response of OS. Additionally, immune analysis confirms a correlation between the risk score and the tumor microenvironment. Our findings, therefore, provide a cogent account for the disparate prognoses observed among patients and furnish a justification for further inquiry into biomarkers and anti-tumor treatment strategies.

Cellular and Genetic Background of Osteosarcoma

Osteosarcoma describes a tumor of mesenchymal origin with an annual incidence rate of four to five people per million. Even though chemotherapy treatment has shown success in non-metastatic osteosarcoma, metastatic disease still has a low survival rate of 20%. A targeted therapy approach is limited due to high heterogeneity of tumors, and different underlying mutations. In this review, we will summarize new advances obtained by new technologies, such as next generation sequencing and single-cell sequencing. These new techniques have enabled better assessment of cell populations within osteosarcoma, as well as an understanding of the molecular pathogenesis. We also discuss the presence and properties of osteosarcoma stem cells-the cell population within the tumor that is responsible for metastasis, recurrence, and drug resistance.

Shedding Light on Osteosarcoma Cell Differentiation: Impact on Biomineralization and Mitochondria Morphology

Osteosarcoma (OS) is the most common primary malignant bone tumor and its etiology has recently been associated with osteogenic differentiation dysfunctions. OS cells keep a capacity for uncontrolled proliferation showing a phenotype similar to undifferentiated osteoprogenitors with abnormal biomineralization. Within this context, both conventional and X-ray synchrotron-based techniques have been exploited to deeply characterize the genesis and evolution of mineral depositions in a human OS cell line (SaOS-2) exposed to an osteogenic cocktail for 4 and 10 days. A partial restoration of the physiological biomineralization, culminating with the formation of hydroxyapatite, was observed at 10 days after treatment together with a mitochondria-driven mechanism for calcium transportation within the cell. Interestingly, during differentiation, mitochondria showed a change in morphology from elongated to rounded, indicating a metabolic reprogramming of OS cells possibly linked to an increase in glycolysis contribution to energy metabolism. These findings add a dowel to the genesis of OS giving new insights on the development of therapeutic strategies able to restore the physiological mineralization in OS cells.

Encapsulation and Delivery of an Osteosarcoma Stem Cell Active Gallium(III)-Diflunisal Complex Using Polymeric Micelles

Here we report the encapsulation of an osteosarcoma stem cell (OSC) potent gallium(III)-diflunisal complex 1 into polymeric nanoparticles, and its delivery into osteosarcoma cells. At the optimum feed (20 %, 1 NP²⁰ ), nanoparticle encapsulation of 1 enhances potency towards bulk osteosarcoma cells and OSCs (cultured in monolayer and three-dimensional systems). Strikingly, the nanoparticle formulation exhibits up to 5645-fold greater potency towards OSCs than frontline anti-osteosarcoma drugs, doxorubicin and cisplatin. The nanoparticle formulation evokes a similar mechanism of action as the payload, which bodes well for future translation. Specifically, the nanoparticle formulation induces nuclear DNA damage, cyclooxygenase-2 downregulation, and caspase-dependent apoptosis. To the best of our knowledge, this is the first study to demonstrate that polymeric nanoparticles can be used to effectively deliver an OSC-active metal complex into osteosarcoma cells.

Dioscin induces osteosarcoma cell apoptosis by upregulating ROS-mediated P38 MAPK signaling

Osteosarcoma is the most common primary malignant bone tumor in children and adolescents. Many patients with osteosarcoma readily develop resistance to chemotherapy and have an extremely dismal prognosis. Dioscin, a saponin, is known to exhibit potent anticancer activities and induce cellular death of a variety of cancer types. However, the inhibitory effect of dioscin on osteosarcoma cells and its underlying mechanisms have not been fully elucidated. We investigated the responses of human U2-OS and MG63 osteosarcoma cells to dioscin with regard to proliferation, apoptosis, migration, and invasion, and studied the effect of dioscin on MAPK-related proteins by western blot analysis assays. Dioscin inhibited osteosarcoma cell proliferation, migration, and invasion. Moreover, it induced osteosarcoma cell apoptosis via reactive oxygen species (ROS)-dependent apoptotic signaling. N-acetylcysteine, a reactive oxygen species inhibitor, suppressed dioscin-induced apoptosis, indicating that ROS play an essential role in dioscin-induced apoptosis. Western blot analysis assays showed that p38 MAPK was upregulated after dioscin treatment, and that dioscin induced apoptosis by upregulating ROS-mediated p38 MAPK signaling. Our study suggests that dioscin possesses antitumor activities against human osteosarcoma cells, inhibits osteosarcoma cell proliferation, migration and invasion, and induces osteosarcoma cell apoptosis through upregulating ROS-mediated p38 MAPK signaling. This study may provide a new therapeutic strategy and potential clinical applications for the treatment of osteosarcoma.

The Osteosarcoma Stem Cell Activity of a Gallium(III)-Phenanthroline Complex Appended to Salicylate

We report the synthesis, characterisation, and anti-osteosarcoma properties of a gallium(III) complex (1) comprising of two 1,10-phenanthroline ligands and salicylate, a non-steroidal anti-inflammatory drug. The gallium(III) complex 1 displays micromolar potency towards bulk osteosarcoma cells and osteosarcoma stem cells (OSCs). Notably, the gallium(III) complex 1 exhibits significantly higher toxicity towards OSCs grown in monolayer and three-dimensional cultures than cisplatin, a frontline anti-osteosarcoma drug. Nuclei isolation and immunoblotting studies show that the gallium(III) complex 1 enters osteosarcoma cell nuclei and induces DNA damage. Flow cytometry and cytotoxicity studies (in the presence of prostaglandin E2) indicate that the gallium(III) complex 1 downregulates cyclooxygenase-2 (COX-2) expression and kills osteosarcoma cells in a COX-2-dependent manner. Further, the mode of osteosarcoma cell death evoked by the gallium(III) complex 1 is characterised as caspase-dependent apoptosis.

Vascular Niche Facilitates Acquired Drug Resistance to c-Met Inhibitor in Originally Sensitive Osteosarcoma Cells

Osteosarcoma (OS) is the most common primary bone tumor in children and adolescents characterized by drug resistance and poor prognosis. As one of the key oncogenes, c-Met is recognized as a promising therapeutic target for OS. In this report, we show that c-Met inhibitor PF02341066 specifically killed OS cells with highly phosphorylated c-Met in vitro. However, the inhibitory effect of PF02341066 was abrogated in vivo due to interference from the vascular niche. OS cells adjacent to microvessels or forming vascular mimicry suppressed c-Met expression and phosphorylation. Moreover, VEGFR2 was activated in OS cells and associated with acquired drug resistance. Dual targeting of c-Met and VEGFR2 could effectively shrink the tumor size in a xenograft model. c-Met-targeted therapy combined with VEGFR2 inhibition might be beneficial to achieve an ideal therapeutic effect in OS patients. Together, our results confirm the pivotal role of tumor heterogeneity and the microenvironment in drug response and reveal the molecular mechanism underlying acquired drug resistance to c-Met-targeted therapy.

Prognostic significance of modified lung immune prognostic index in osteosarcoma patients

Purpose: Osteosarcoma is the most common primary malignancy of bone with a dismal prognosis for patients with pulmonary metastases. Evaluation of osteosarcoma prognosis would facilitate the prognosis consultation as well as the development of personalized treatment decisions. However, there is limited effective prognostic predictor at present. Lung Immune Prognostic Index (LIPI) is a novel prognostic factor in pulmonary cancers, whereas, the prognostic significance of LIPI in osteosarcoma has not yet been well clarified. In this study, we firstly explore the prognostic role of LIPI and further modify this predictive model in osteosarcoma.

Patients and methods: A retrospectively study was conducted at Musculoskeletal Tumor Center of West China Hospital between January 2016 and January 2021. Hematological factors and clinical features of osteosarcoma patients were collected and analyzed. The area under curve (AUC) and optimal cuff-off of each single hematological factor was calculated.

Results: In this study, lactate dehydrogenase (LDH), derived neurtrophil to lymphocyte ratio (dNLR), and Hydroxybutyrate dehydrogenase (HBDH) have higher AUC values. LIPI was composed of LDH and dNLR and was further modified by combing the HBDH, forming the osteosarcoma immune prognostic index (OIPI). OIPI divided 223 osteosarcoma patients divided into four groups, none, light, moderate, and severe (p < 0.0001). OIPI has a higher AUC value than LIPI and other hematological indexes in t-ROC curve. According to the univariate and multivariate analysis, pathological fracture, metastasis, NLR, platelet–lymphocyte ratio (PLR), and OIPI were associated with the prognosis; and metastasis and OIPI were independent prognostic factors of osteosarcoma patients. An OIPI-based nomogram was also established and could predict the 3-year and 5-year overall survival. In addition, OIPI was also revealed correlated with metastasis and pathological fracture in osteosarcoma.

Conclusion: This study first explore the prognostic significance of LIPI in osteosarcoma patients. In addition, we developed a modified LIPI, the OIPI, for osteosarcoma patients. Both the LIPI and OIPI could predict the overall survival of osteosarcoma patients well, while OIPI may be more suitable for osteosarcoma patients. In particular, OIPI may have the ability to identify some high-risk patients from clinically low-risk patients.

Hypermethylated PODN represses the progression of osteosarcoma by inactivating the TGF-β/Smad2/3 pathway

BACKGROUND

PODN is reported to be an promising biomarker for prognosis of osteosarcoma (OS), while the specific function of PODN has not been explored in OS. This study is designed to explore the function and underlying mechanism of PODN in OS.

METHODS

The mRNA expression of PODN was determined using qRT-PCR. Protein levels of PODN, DNMT1, DNMT3A, DNMT3B, TGF-β1, Smad2/3 and p-Smad2/3 were detected using western blot. The methylation of PODN was determined with methylation-specific PCR. Moreover, CCK-8 assay and colony formation assay were used for assessing the proliferation of OS cells. Transwell assay was used to evaluate migration and invasion abilities of OS cells. Immunohistochemical staining was performed to determine the protein expression of Ki67 and PODN in tumor tissues. For constructing a xenograft tumor model, MG-63 cells were introduced into the right side of the mouse back via subcutaneous injection.

RESULTS

PODN was lowly expressed and was hypermethylated in OS tissues and cells. PODN overexpression prevented OS cells from proliferating, migrating and invading, and inhibited tumorigenesis in xenograft mice. After PODN overexpression, protein levels of TGF-β1 and p-Smad2/3 were decreased in OS cells. Meantime, the suppressive effects of PODN overexpression on proliferation, migration and invasion of OS cells as well as mouse tumorigenesis were partly counteracted by TGF-β1 overexpression.

CONCLUSIONS

PODN overexpression inactivated the TGF-β/Smad2/3 pathway to suppress OS development in vitro and in vivo.

Integration of single-cell RNA sequencing and bulk RNA sequencing to reveal an immunogenic cell death-related 5-gene panel as a prognostic model for osteosarcoma

Background

Despite the comparatively low prevalence of osteosarcoma (OS) compared to other cancer types, metastatic OS has a poor overall survival rate of fewer than 30%. Accumulating data has shown the crucial functions of immunogenic cell death (ICD) in various cancers; nevertheless, the relationship between ICD and OS was not previously well understood. This research aims to determine the function of ICD in OS and construct an ICD-based prognostic panel.

Methods

Single cell RNA sequencing data from GSE162454 dataset distinguished malignant cells from normal cells in OS. The discrepancy in ICD scores and corresponding gene expression was intensively explored between malignant cells and normal cells. Using the RNA sequencing data of the TARGET-OS, GSE16091, GSE21257, and GSE39058 datasets, the molecular subtype of OS was determined by clustering seventeen ICD-related genes obtained from the literature. Differentially expressed genes (DEGs) between different molecular subtypes were identified to develop a novel ICD-associated prognostic panel.

Results

The malignant cells had a remarkable decrease in the ICD scores and corresponding gene expression compared with normal cells. A total of 212 OS patients were successfully stratified into two subtypes: C1 and C2. C1-like OS patients were characterized by better prognostic outcomes, overexpression of ICD genes, activation of the ICD pathway, high inflitration abundance of immunocytes, and low expression levels of immune checkpoint genes (ICGs); however, the reverse is true in C2-like OS patients. Utilizing the limma programme in R, the DEGs between two subtypes were determined, and a 5-gene risk panel consisting of BAMBI, TMCC2, NOX4, DKK1, and CBS was developed through LASSO-Cox regression analysis. The internal- and external-verification cohorts were employed to verify the efficacy and precision of the risk panel. The AUC values of ROC curves indicated excellent prognostic prediction values of our risk panel.

Conclusions

Overall, ICD represented a protective factor against OS, and our 5-gene risk panel serving as a biomarker could effectively evaluate the prognostic risk in patients with OS.

Osteosarcoma subtypes based on platelet-related genes and tumor microenvironment characteristics

Background

Osteosarcoma is a common metastatic tumor in children and adolescents. Because of its easy metastasis, patients often show a poor prognosis. Recently, researchers have found that platelets are closely related to metastasis of a variety of malignant tumors, but the role of platelets related characteristics in osteosarcoma is still unknown. The purpose of this study is to explore the characteristics of platelet-related subtypes and cell infiltration in tumor microenvironment.

Methods

We collected osteosarcoma cohorts from TCGA and GEO databases, and explored the molecular subtypes mediated by platelet-related genes and the related TME cell infiltration according to the expression of platelet-related genes in osteosarcoma. In addition, we also explored the differentially expressed genes (DEGs) among different molecular subtypes and established a protein-protein interaction network (PPI). Then we constructed a platelet scoring model by Univariate cox regression and least absolute shrinkage and selection operator (Lasso) cox regression model to quantify the characteristics of platelet in a single tumor. RT-PCR was used to investigate the expression of six candidate genes in osteosarcoma cell lines and normal osteoblast lines. Finally, we also predicted potential drugs with therapeutic effects on platelet-related subtypes.

Results

We found that platelet-related genes (PRGs) can distinguish osteosarcoma into two different platelet-related subtypes, C1 and C2. And the prognosis of the C2 subtype was significantly worse than that of C1 subtype. The results of ESTIMATE analysis and GO/KEGG enrichment showed that the differences between different subtypes were mainly concentrated in immune response pathways, and the immune response of C2 was inhibited relative to C1. We further studied the relationship between platelet-related subtypes and immune cell infiltration. We found that the distribution of most immune cells in C1 subtype was higher than that in C2 subtype, and there was a correlation between C1 subtype and more immune cells. Finally, we screened the PRGs related to the prognosis of osteosarcoma through Univariate Cox regression, established independent prognostic platelet characteristics consisting of six genes to predict the prognosis of patients with OS, and predicted the drugs that may be used in the treatment of osteosarcoma. RT-PCR was used to verify the expression of candidate genes in osteosarcoma cells.

Conclusion

Platelet scoring model is a significant biomarker, which is of great significance to determine the prognosis, molecular subtypes, characteristics of TME cell infiltration and therapy in patients with OS.

EID3 Promotes Cancer Stem Cell-Like Phenotypes in Osteosarcoma through the Activation of PI3K-AKT Signaling Pathway

The aim of this study is to elucidate molecular mechanism by which E1A-like inhibitor of differentiation 3 (EID3) promotes cancer stem cell-like phenotypes in osteosarcoma. Overexpression of EID3 in osteosarcoma cells generated more spherical clones, enhanced the expression of stemness-associated genes, and promoted chemoresistance, invasion, and metastasis. Furthermore, osteosarcoma cells overexpressing EID3 had increased ability to grow in suspension as osteospheres with high expression of Sox2 and stem cell marker CD133. In addition, knockdown of EID3 reduced sphere formation and inhibited osteosarcoma cell migration and invasion. RNA sequencing and bioinformatics analysis revealed that PI3K-Akt signaling pathway and MAPK pathway­related genes were enriched in osteosarcoma cells with high expression of EID3. Taken together, EID3 promotes osteosarcoma, and EID3–PI3K-Akt axis is a potential therapeutic target for osteosarcoma treatment.

PKIB involved in the metastasis and survival of osteosarcoma

Osteosarcoma is frequently metastasized at the time of diagnosis in patients. However, the underlying mechanism of osteosarcoma metastasis remains poorly understood. In this study, we evaluated DNA methylation profiles combined with gene expression profiles of 21 patients with metastatic osteosarcoma and 64 patients with non-metastatic osteosarcoma from TARGET database and identified PKIB and AIM2 as hub genes related to the metastasis of osteosarcoma. To verify the effects of PKIB on migration and invasion of osteosarcoma, we performed wound-healing assay and transwell assay. The results showed that PKIB significantly inhibited the migration and invasion of osteosarcoma cells, and the Western blot experiments showed that the protein level of E-cad was upregulated and of VIM was downregulated in 143-B cell recombinant expression PKIB. These results indicate that PKIB inhibit the metastasis of osteosarcoma. CCK-8 assay results showed that PKIB promote the proliferation of osteosarcoma. In addition, the Western blot results showed that the phosphorylation level of Akt was upregulated in 143-B cells overexpressing PKIB, indicating that PKIB promotes the proliferation of osteosarcoma probably through signaling pathway that Akt involved in. These results give us clues that PKIB was a potential target for osteosarcoma therapy. Furthermore, combined clinical profiles analysis showed that the expression of AIM2- and PKIB- related risk scores was significantly related to the overall survival of patients with osteosarcoma. Thus, we constructed a nomogram based on AIM2 and PKIB expression–related risk scores for osteosarcoma prognostic assessment to predict the 1-, 2-, 3-, and 5-year overall survival rate of patients with metastatic osteosarcoma, assisting clinicians in the diagnosis and treatment of metastatic osteosarcoma.

Hsa_circ_0001017 promotes cell proliferation, migration and invasion in osteosarcoma by sponging miR-145-5p

BACKGROUND

Circular RNAs (circRNAs) have displayed important roles in the development and progression of various cancers. However, the functions of the majority of circRNAs in osteosarcoma (OS) remain unknown.

METHODS

Circular RNA microarray analysis was performed in three OS cell lines (Saos-2, U2OS and MG63) and normal vascular endothelial cells. The co-differentially expressed circRNAs (CDECs) were identified in OS cell lines with the criterion of FDR (false discovery rate) < 0.05 and |fold change (FC)|> 2. Quantitative real-time PCR was used to validate the expression levels of selected CDECs. A series of functional assays, including MTT assay, flow cytometry and transwell assay were conducted in OS cells. The interaction between circRNA and miRNAs was confirmed by luciferase reporter assay and RNA immunoprecipitation assay.

RESULTS

A total of 241 CDECs, including 75 upregulated and 166 downregulated CDECs, were identified in three OS cell lines compared with normal vascular endothelial cells. PCR validation showed that hsa_circ_0000704, hsa_circ_0001017 and hsa_circ_0005035 were all highly expression in the three OS cell lines, compared with osteoblast cell lines (HECC, hFOB1.19 and HFF-1). Functionally, overexpression of circ_0001017 significantly promoted the cell proliferation, migration and invasion and decreased apoptosis in U2OS cells. Knockdown of circ_0001017 obtained the opposite results. Circ_0001017 may downregulate miR-145-5p through direct binding. Furthermore, the expression of miR-145-5p was negatively regulated by circ_0001017 in OS cells. In addition, further functional studies indicated that miR-145-5p inhibitor eliminated the effects caused by si-circ_0001017 in OS cells.

CONCLUSIONS

In conclusion, our study suggested that circ_0001017 may be a novel oncogenic factor during the progression and development of OS by targeting miR-145-5p.

The Roles of Noncoding RNAs in the Development of Osteosarcoma Stem Cells and Potential Therapeutic Targets

Osteosarcoma (OS) is the common bone tumor in children and adolescents. Because of chemotherapy resistance, the OS patients have a poor prognosis. The one reason of chemotherapeutic resistance is the development of cancer stem cells (CSCs). CSCs represent a small portion of tumor cells with the capacity of self-renewal and multipotency, which are associated with tumor initiation, metastasis, recurrence and drug resistance. Recently, noncoding RNAs (ncRNAs) have been reported to critically regulate CSCs. Therefore, in this review article, we described the role of ncRNAs, especially miRNAs, lncRNAs and circRNAs, in regulating CSCs development and potential mechanisms. Specifically, we discussed the role of multiple miRNAs in targeting CSCs, including miR-26a, miR-29b, miR-34a, miR-133a, miR-143, miR-335, miR-382, miR-499a, miR-1247, and let-7days. Moreover, we highlighted the functions of lncRNAs in regulating CSCs in OS, such as B4GALT1-AS1, DANCR, DLX6-AS1, FER1L4, HIF2PUT, LINK-A, MALAT1, SOX2-OT, and THOR. Due to the critical roles of ncRNAs in regulation of OS CSCs, targeting ncRNAs might be a novel strategy for eliminating CSCs for OS therapy.

Emerging Roles and Mechanisms of lncRNA FOXD3-AS1 in Human Diseases

Numerous long noncoding RNAs (lncRNAs) have been identified as powerful regulators of human diseases. The lncRNA FOXD3-AS1 is a novel lncRNA that was recently shown to exert imperative roles in the initialization and progression of several diseases. Emerging studies have shown aberrant expression of FOXD3-AS1 and close correlation with pathophysiological traits of numerous diseases, particularly cancers. More importantly, FOXD3-AS1 was also found to ubiquitously impact a range of biological functions. This study aims to summarize the expression, associated clinicopathological features, major functions and molecular mechanisms of FOXD3-AS1 in human diseases and to explore its possible clinical applications.

Osteosarcoma cell proliferation suppression via SHP-2-mediated inactivation of the JAK/STAT3 pathway by tubocapsenolide A

Introduction

Previously, we have reported a withanolide-type steroid, named tubocapsenolide A (TA), which shows potent anti-proliferative activity in several cancer cell lines. However, its inhibitory effect on the Janus kinase/signal transducer and activator of transcription 3 (JAK/STAT3) pathway and therapeutic potential on osteosarcoma have not been reported.

Objectives

In the present study, we aimed to investigate the effect and molecular mechanism of TA in osteosarcoma.

Methods

The biological functions of TA in U2OS cells were investigated using colony formation, 5-ethynyl-20-deoxyuridine (EDU) staining, and cell cycle/apoptosis assays. The interaction between TA and Src homology 2 phosphatase 2 (SHP-2) was detected by enzyme activity and validated by target-identification methods such as drug affinity responsive target stability (DARTS), cellular thermal shift assay (CETSA), and biolayer interferometry (BLI). The in vivo anti-tumor efficacy of TA was analyzed in the xenograft tumor model. Western blotting analysis was performed to detect the protein expression levels.

Results

TA exhibited antitumor activity against osteosarcoma both in vitro and in vivo by regulating the JAK/STAT3 signaling pathway. Mechanically, TA interacted with SHP-2 directly and activated its phosphatase activity. Importantly, protein tyrosine phosphatase (PTP) inhibitor, SHP-2 inhibitor, and SHP-2 siRNA could reverse the inhibitory effect of TA on the JAK/STAT3 signaling pathway and restored the TA-induced cell death.

Conclusion

TA activated the phosphatase activity of SHP-2, which resulted in the inhibition of the JAK/STAT3 pathway and contributed to the antitumor efficacy of TA. Collectively, these findings suggested that TA could serve as a novel therapeutic agent for the treatment of osteosarcoma.

Advances in the Research of Osteosarcoma Stem Cells and its Related Genes

Osteosarcoma is a malignant tumor that often occurs in adolescents. There is an urgent need of new treatment options for osteosarcoma due to its poor prognosis after metastasis. Cancer stem cell theory states that cancer stem cells represent a small proportion of cancer cells. These cancer stem cells have self-renewal ability and are closely associated with cancer growth and metastasis as well as chemotherapy resistance. Similarly, osteosarcoma stem cells (OSCs) play an important role in the growth, metastasis, and chemotherapy resistance of osteosarcoma cells. Targeting OSCs may represent a future treatment of osteosarcoma. Furthermore, some genes have shown to regulate the growth, metastasis, and chemotherapy resistance of osteosarcoma cells by altering the stemness of OSCs. Targeting these genes may help in the treatment of osteosarcoma. This review mainly discusses recent advances in the research of OSCs and its related genes. This article is protected by copyright. All rights reserved.

miR-557 suppressed the malignant behaviours of osteosarcoma cells by reducing HOXB9 and deactivating the EMT process

MicroRNAs (miRNAs) are vital gene regulators, which play a profound role in the process of forming and developing many diseases, especially tumour. The study intends to excavate the potential regulatory mechanisms of miR-557 and its targeting gene Homeobox B9 (HOXB9) in osteosarcoma. GEO dataset on osteosarcoma was applied to detect the expression of miR-557 and HOXB9. Associations between miR-557 and HOXB9 were speculated by prediction software and verified by dual luciferase assay. Cell proliferation, colony formation and mobility were measured by cell counting kit-8, plate clone formation and transwell assays. Expression of mesenchymal transitions (MTs) related proteins was assessed by western blot analysis. Low expression of miR-557 was presented in osteosarcoma tissues and cell lines. Upregulation of miR-557 restrained osteosarcoma cells proliferation, movement and MT process. HOXB9, served as a target gene of miR-557, was highly expressed in osteosarcoma, and its high expression was associated with poor prognosis in patients with osteosarcoma. In addition, overexpression of HOXB9 attenuated the inhibitory effects of miR-557 on tumour progression by MT process. Overexpression of miR-557 suppressed the growth, metastasis and MT process of osteosarcoma cells by targeting HOXB9, affording novel molecular selection for targeted therapy of osteosarcoma.

Tumor-associated macrophages in osteosarcoma

Osteosarcoma (OS) is the most common primary bone tumor in children and adolescents. It is an aggressive tumor with a tendency to spread to the lung, which is the most common site of metastasis. Patients with advanced OS with metastases have poor prognoses despite the application of chemotherapy, thus highlighting the need for novel therapeutic targets. The tumor microenvironment (TME) of OS is confirmed to be essential for and supportive of tumor growth and dissemination. The immune component of the OS microenvironment is mainly composed of tumor-associated macrophages (TAMs). In OS, TAMs promote tumor growth and angiogenesis and upregulate the cancer stem cell-like phenotype. However, TAMs inhibit the metastasis of OS. Therefore, much attention has been paid to investigating the mechanism of TAMs in OS development and the progression of immunotherapy for OS. In this article, we aim to summarize the roles of TAMs in OS and the major findings on the application of TAMs in OS treatment.

A Novel Overall Survival Prediction Signature Based on Cancer Stem Cell-Related Genes in Osteosarcoma

Background: Osteosarcoma is the most general bone malignancy that mostly affects children and adolescents. Numerous stem cell-related genes have been founded in distinct forms of cancer. This study aimed at identifying a stem cell-related gene model for the expected assessment of the prognosis of osteosarcoma patients.

Methods: We obtained the genes expression data and relevant clinical materials from Therapeutically Applicable Research to Generate Effective Treatments (TARGET) and Gene Expression Omnibus (GEO) databases. We identified differentially expressed genes (DEGs) from the GEO dataset, whereas prognostic stem cell-related genes were obtained from the TARGET database. Subsequently, univariate, LASSO and multivariate Cox regression analyses were applied to establish the stem cell-related signature. Finally, the prognostic value of the signature was validated in the GEO dataset.

Results: Twenty-five genes were prognostic ferroptosis-related DEGs. Consequently, we identified eight stem cell-related genes as a signature of prognosis of osteosarcoma patients. Then, the Kaplan–Meier (K-M) curve, the AUC value of ROC, and Cox regression analysis verified that the eight stem cell-related gene model were a new and substantial prognostic marker independent of other clinical traits. Moreover, the nomogram on the foundation of risk score and other clinical traits was established for predicting the survival rate of osteosarcoma patients. Biological function analyses displayed that tumor related pathways were affluent.

Conclusion: The expression level of stem cell-related genes offers novel prognostic markers as well as underlying therapeutic targets for the therapy and prevention of osteosarcoma.

Circ_0084582 Facilitates Cell Growth, Migration, Invasion, and Angiopoiesis in Osteosarcoma via Mediating the miR-485-3p/JAG1 Axis

Osteosarcoma (OS) is the most representative bone cancer, and circular RNAs serve as pivotal regulators in the progression of OS. This research was designed to explore the role and functional mechanism of circ_0084582 in OS. Circ_0084582, microRNA-485-3p (miR-485-3p), and Jagged1 (JAG1) levels were measured by quantitative real-time polymerase chain reaction. Cell proliferation was examined via 3-(4, 5-dimethylthiazol-2-y1)-2, 5-diphenyl tetrazolium bromide (MTT) assay. Cell cycle progression was analyzed by flow cytometry. Wound healing and transwell assays were performed for evaluating cell migration and invasion. Angiopoiesis was assessed using the tube formation assay. Protein detection was conducted using Western blot. The target relation was identified by the dual-luciferase reporter assay, RNA immunoprecipitation (RIP) assay, and RNA pull-down assay. A xenograft experiment was applied for analyzing the effect of circ_0084582 on OS in vivo. Circ_0084582 was highly expressed in OS tissues and cells. Circ_0084582 knockdown reduced cell proliferation, cell cycle progression, migration, invasion, and angiopoiesis of OS cells. JAG1 was upregulated in OS, and its overexpression reversed the effects of circ_0084582 knockdown on OS cells. Circ_0084582 targeted miR-485-3p, and miR-485-3p targeted JAG1, and circ_0084582 could affect the JAG1 level by sponging miR-485-3p. The function of circ_0084582 in OS progression was also achieved by sponging miR-485-3p. Circ_0084582 knockdown decreased OS growth in vivo partly by the miR-485-3p–mediated JAG1 downregulation. These results indicate that circ_0084582 functions as a tumorigenic factor in OS via the regulation of miR-485-3p/JAG1 axis.

In vitro selection of DNA aptamers against human osteosarcoma

BACKGROUND

 Osteosarcoma is a highly malignant bone tumor, most frequently occurring in the rapid bone growth phase. Effective treatment of this disease is hindered by the lack of specific probes for early diagnosis and the fast cancer widespread.

METHODS

 To find such probes, the cell-Systematic Evolution of Ligands by EXponential enrichment (cell-SELEX) methodology was implemented against the human osteosarcoma MG-63 cell line towards the selection of new specific aptamers. After 10 rounds of selection, the aptamer DNA pool was Sanger sequenced and the sequences were subjected to a bioinformatic analysis that included sequence alignment, phylogenetic relationship, and secondary structure prediction.

RESULTS

 A DNA aptamer (OS-7.9), with a dissociation constant (K_d) value in the nanomolar range (12.8 ± 0.9 nM), revealed high affinity against the target cells at the physiological temperature. Furthermore, the selected aptamer also recognized lung carcinoma and colon colorectal adenocarcinoma cell lines, which are reported as common metastasis sites of osteosarcoma.

CONCLUSIONS

 These results suggest that OS-7.9 could recognize a common protein expressed in these cancer cells, possibly becoming a potential molecular probe for early diagnosis and targeted therapies for metastatic disease. Moreover, to the best of our knowledge, this was the first attempt to generate a DNA aptamer (OS-7.9 aptamer) against the MG-63-cell line by cell-SELEX.

A new antisarcoma strategy: multisubtype heat shock protein/peptide immunotherapy combined with PD-L1 immunological checkpoint inhibitors

Osteosarcoma, a common malignant tumor in orthopedics, often has a very poor prognosis after lung metastasis. Immunotherapy has not achieved much progress in the treatment because of the characteristics of solid tumors and immune environment of osteosarcoma. The tumor environment is rather essential for sarcoma treatment. Our previous study demonstrated that heat shock proteins could be used as antitumor vaccines by carrying tumor antigen peptides, and we hypothesize that an anti-osteosarcoma effect may be increased with an immune check point inhibitor (PD-L1 inhibitor) as a combination treatment strategy. The present study prepared a multisubtype mixed heat shock protein osteosarcoma vaccine (mHSP/peptide vaccine) and concluded that the mHSP/peptide vaccine was more effective than a single subtype heat shock protein, like Grp94. Therefore, we used the mHSP/peptide vaccine in combination with a PD-L1 inhibitor to treat osteosarcoma, and the deterioration of osteosarcoma was effectively hampered. The mechanism of combined therapy was investigated, and AKT expression participates with sarcoma lung metastasis. This study proposed an antisarcoma strategy via stimulation of the immune system as a further alternative approach for sarcoma treatment and elucidated the mechanism of combined therapy.

Osteosarcoma Stem Cell Potent Gallium(III)-Polypyridyl Complexes Bearing Diflunisal

We report the anti‐osteosarcoma stem cell (OSC) properties of a series of gallium(III)‐polypyridyl complexes (5‐7) containing diflunisal, a non‐steroidal anti‐inflammatory drug. The most effective complex within the series, 6 (containing 3,4,7,8‐tetramethyl‐1,10‐phenanthroline), displayed similar potency towards bulk osteosarcoma cells and OSCs, in the nanomolar range. Remarkably, 6 exhibited significantly higher monolayer and sarcosphere OSC potency (up to three orders of magnitude) than clinically approved drugs used in frontline (cisplatin and doxorubicin) and secondary (etoposide, ifosfamide, and carboplatin) osteosarcoma treatments. Mechanistic studies show that 6 downregulates cyclooxygenase‐2 (COX‐2) and kills osteosarcoma cells in a COX‐2 dependent manner. Furthermore, 6 induces genomic DNA damage and caspase‐dependent apoptosis. To the best of our knowledge, 6 is the first metal complex to kill osteosarcoma cells by simultaneously inhibiting COX‐2 and damaging nuclear DNA.

Piperlongumine inhibits the progression of osteosarcoma by downregulating the SOCS3/JAK2/STAT3 pathway via miR-30d-5p

AIMS

The present study evaluated the functions of Piperlongumine (PL) in osteosarcoma (OS) cell growth and metastasis both in vitro and in vivo.

MAIN METHODS

MTT assay was conducted to test the cytotoxic effects of PL on the human osteoblasts line HFOB1.19 and the human normal chondrocyte line C28/I2T. FITC-Annexin V and propidium iodide (PI) were used to examine cell apoptosis. The migration, invasion and relative epithelial-mesenchymal transition were examined by Transwell assay and Western blotting. Reverse transcription-quantitative PCR (RT-qPCR) was performed to analyze the cytokine signaling 3 (SOCS3) mRNA expression. TargetScan database was used to predict the target of SOCS3. The binding association between miR-30d-5p and SOCS3 in U2OS and MG63 cells was evaluated by the dual-luciferase reporter assay. A xenograft model was constructed to evaluate the effect of PL on OS cell growth in vivo.

KEY FINDINGS

The results revealed that PL inhibited the growth, migration, invasion, epithelial-mesenchymal transition, and promoted the apoptosis of OS cells dose-dependently. In addition, PL upregulated the protein levels of suppressor of SOCS3, while it inactivated the JAK2/STAT3 pathway, which was accompanied by a decreased level of microRNA (miR)-30d-5p. Furthermore, SOCS3was confirmed as a novel target of miR-30d-5p. Overexpression of miR-30d-5p not only led to decreased expression of SOCS3, but also dampened the antitumor effect of PL on OS.

SIGNIFICANCE

The present data demonstrated that PL inhibited the progression of OS via downregulation of the SOCS3-mediated JAK2/STAT3 pathway by inhibiting miR-30d-5p.

CircRAB3IP upregulates twist family BHLH transcription factor (TWIST1) to promote osteosarcoma progression by sponging miR-580-3p

Circular RNAs (circ RNAs) have been found to play an important role in cancer development. However, the role of circRAB3IP in osteosarcoma (OS) is unclear.

In the present study, We found that circRAB3IP was highly expressed in OS tissues and OS cells. High levels of circRAB3IP was correlated with advanced TNM stage, distant metastasis. CircRAB3IP knockdown inhibited cell proliferation, migration, and invasion. Moreover, circRAB3IP directly binds to miR-580-3p. TWIST1 is directly targeted by miR-580-3p. We also demonstrated that circRAB3IP act as the sponge of miR-580-3p to promote TWIST1 expression. CircRAB3IP promotes OS cells proliferation, migration, and invasion through modulating miR-580-3p/TWIST1 axis. Moreover, circRAB3IP facilitated tumor formation in vivo. Our findings suggested that circRAB3IP acts as an oncogene in OS by regulating miR-580-3p/TWIST1 axis.

Cancer Stem Cells as a Source of Drug Resistance in Bone Sarcomas

Bone sarcomas are commonly characterized by a high degree of intra-tumor heterogeneity, which in part is due to the presence of subpopulations of tumor cells presenting stem cell properties. Similar to normal stem cells, these cancer stem cells (CSCs) display a drug resistant phenotype and therefore are responsible for relapses and tumor dissemination. Drug resistance in bone sarcomas could be enhanced/modulated during tumor evolution though the acquisition of (epi)-genetic alterations and the adaptation to changing microenvironments, including drug treatments. Here we summarize findings supporting the involvement of pro-stemness signaling in the development of drug resistance in bone sarcomas. This include the activation of well-known pro-stemness pathways (Wnt/β-Cat, NOTCH or JAT/STAT pathways), changes in the metabolic and autophagic activities, the alteration of epigenetic pathways, the upregulation of specific non-coding RNAs and the crosstalk with different microenvironmental factors. This altered signaling is expected to be translated to the clinic in the form of biomarkers of response and new therapies able to overcome drug resistance.

Deregulation of CLTC interacts with TFG, facilitating osteosarcoma via the TGF-beta and AKT/mTOR signaling pathways

Although the treatment of osteosarcoma has improved, the overall survival rate of this common type of osseous malignancies has not changed for four decades. Thus, new targets for better therapeutic regimens are urgently needed. In this study, we found that high expression of clathrin heavy chain (CLTC) was an independent prognostic factor for tumor-free survival (HzR, 3.049; 95% CI, 1.476-6.301) and overall survival (HzR, 2.469; 95% CI, 1.005-6.067) of patients with osteosarcoma. Down-regulation of CLTC resulted in tumor-suppressive effects in vitro and in vivo. Moreover, we found that CLTC was transcriptionally regulated by a transcription factor-specificity protein 1 (SP1), which binds to the CLTC promoter at the -320 to -314-nt and +167 to +173-nt loci. Mechanistic investigations further revealed that CLTC elicited its pro-tumor effects by directly binding to and stabilizing trafficking from the endoplasmic reticulum to the Golgi regulator (TFG). Importantly, overexpression of TFG rescued both the tumor-suppressive effect and inhibition of the TGF-β and AKT/mTOR pathways caused by CLTC down-regulation, which indicated that the activity of CLTC was TFG-dependent. Immunohistochemistry analysis confirmed that CLTC expression was positively correlated with TFG expression. These findings collectively highlight CLTC as a new prognostic biomarker for patients with osteosarcoma, and the interruption of the SP1/CLTC/TFG axis may serve as a novel therapeutic strategy for osteosarcoma.

Hsa_circ_0010220 regulates miR-198/Syntaxin 6 axis to promote osteosarcoma progression

•

hsa_circ_0010220 expression is increased in osteosarcoma.

•

hsa_circ_0010220 knockdown represses cell proliferation, migration and invasion.

•

hsa_circ_0010220 regulates Syntaxin 6 via miR-198.

•

hsa_circ_0010220 silence decreases xenograft tumor growth.

Background

Circular RNAs (circRNAs) are a class of endogenous RNAs that are involved in osteosarcoma progression. Hsa_circ_0010220 (circ_0010220) is a circRNA generated by gene Rho Guanine Nucleotide Exchange Factor 10 Like (ARHGEF10L) and is upregulated in osteosarcoma, but its functional role in osteosarcoma is limited studied. This study aimed to illustrate the regulatory mechanism underlying circ_0010220 in osteosarcoma.

Methods

51 paired tumor and normal tissues were obtained from osteosarcoma patients. circ_0010220, microRNA (miR)-198 and Syntaxin 6 (STX6) abundances were examined by quantitative reverse transcription polymerase chain reaction and western blot. Cell proliferation, cell cycle, apoptosis, migration and invasion were analyzed via Cell Counting Kits-8 (CCK-8), colony formation, flow cytometry and transwell analyses. Target relationship was verified via dual-luciferase reporter analysis, RNA immunoprecipitation and pull-down. The in vivo function was analyzed using a xenograft model.

Results

Circ_0010220 was elevated in osteosarcoma tissues and cells, and was related to the lower survival rate of osteosarcoma patients. Circ_0010220 knockdown inhibited cell proliferation, migration and invasion, but induced cell cycle arrest and apoptosis in vitro. Besides, circ_0010220 silence curbed the growth of xenograft osteosarcoma tumors in vivo. Mechanistic research revealed that miR-198 is a target of circ_0010220, and directly targets STX6. Moreover, circ_0010220 upregulated the expression of STX6 by sponging miR-198 to regulate cell proliferation, migration, invasion, cell cycle, and apoptosis.

Conclusion

Circ_0010220 contributes to osteosarcoma progression through mediating miR-198/STX6 axis, which might be a novel therapeutic target for osteosarcoma therapy.

Genome-editing approaches and applications: a brief review on CRISPR technology and its role in cancer

The development of genome-editing technologies in 1970s has discerned a new beginning in the field of science. Out of different genome-editing approaches such as Zing-finger nucleases, TALENs, and meganucleases, clustered regularly interspaced short palindromic repeats-CRISPR-associated protein 9 (CRISPR/Cas9) is a recent and versatile technology that has the ability of making changes to the genome of different organisms with high specificity. Cancer is a complex process that is characterized by multiple genetic and epigenetic changes resulting in abnormal cell growth and proliferation. As cancer is one of the leading causes of deaths worldwide, a large number of studies are done to understand the molecular mechanisms underlying the development of cancer. Because of its high efficiency and specificity, CRISPR/Cas9 has emerged as a novel and powerful tool in the field of cancer research. CRISPR/Cas9 has the potential to accelerate cancer research by dissecting tumorigenesis process, generating animal and cellular models, and identify drug targets for chemotherapeutic approaches. However, despite having tremendous potential, there are certain challenges associated with CRISPR/Cas9 such as safe delivery to the target, potential off-target effects and its efficacy which needs to be addressed prior to its clinical application. In this review, we give a gist of different genome-editing technologies with a special focus on CRISPR/Cas9 development, its mechanism of action and its applications, especially in different type of cancers. We also highlight the importance of CRISPR/Cas9 in generating animal models of different cancers. Finally, we present an overview of the clinical trials and discuss the challenges associated with translating CRISPR/Cas9 in clinical use.

Downregulation of long non-coding RNA UCA1 represses tumorigenesis and metastasis of osteosarcoma via miR-513b-5p/E2F5 axis

Long non-coding RNAs have the regulatory roles in different kinds of human cancers. The key point of this study was to research the functional mechanisms of urothelial carcinoma associated 1 (UCA1) in the development of osteosarcoma. Quantitative real-time PCR was adopted for the expression detection of UCA1, microRNA-513b-5p (miR-513b-5p) and E2F transcription factor 5 (E2F5). The target relation was verified via dual-luciferase reporter assay and RNA pull-down assay. Cell proliferation was evaluated using Cell Counting Kit-8 and colony formation assays. Transwell assay was applied to assess cell migration and invasion. Western blot was performed for protein examination. Xenograft experiment was used to explore the effect of UCA1 on osteosarcoma in vivo. UCA1 expression was enhanced while miR-513b-5p was refrained in osteosarcoma tissues and cells. MiR-513b-5p was a target of UCA1. Inhibition of UCA1 or overexpression of miR-513b-5p suppressed osteosarcoma cell proliferation, migration and invasion. E2F5 was identified as a downstream gene of miR-513b-5p. MiR-513b-5p inhibitor or E2F5 overexpression rescued the progression inhibition of osteosarcoma by UCA1 knockdown, and UCA1 regulated E2F5 and Cyclin E expression by targeting miR-513b-5p. Downregulation of UCA1 restrained the tumorigenesis of osteosarcoma in vivo through the miR-513b-5p/E2F5 axis. Collectively, knockdown of UCA1 inhibited tumorigenesis and metastasis of osteosarcoma via regulating the miR-513b-5p/E2F5 axis. UCA1 might be a biological indicator in the progression and treatment of osteosarcoma.

Direct conversion of osteosarcoma to adipocytes by targeting TNIK

Osteosarcoma (OS) is an aggressive mesenchymal tumor for which no molecularly targeted therapies are available. We have previously identified TRAF2- and NCK-interacting protein kinase (TNIK) as an essential factor for the transactivation of Wnt signal target genes and shown that its inhibition leads to eradication of colorectal cancer stem cells. The involvement of Wnt signaling in the pathogenesis of OS has been implicated. The aim of the present study was to examine the potential of TNIK as a therapeutic target in OS. RNA interference or pharmacological inhibition of TNIK suppressed the proliferation of OS cells. Transcriptome analysis suggested that a small-molecule inhibitor of TNIK upregulated the expression of genes involved in OS cell metabolism and downregulated transcription factors essential for maintaining the stem cell phenotype. Metabolome analysis revealed that this TNIK inhibitor redirected the metabolic network from carbon flux toward lipid accumulation in OS cells. Using in vitro and in vivo OS models, we confirmed that TNIK inhibition abrogated the OS stem cell phenotype, simultaneously driving conversion of OS cells to adipocyte-like cells through induction of PPARγ. In relation to potential therapeutic targeting in clinical practice, TNIK was confirmed to be in an active state in OS cell lines and clinical specimens. From these findings, we conclude that TNIK is applicable as a potential target for treatment of OS, affecting cell fate determination.

Circ_0105346 Knockdown Inhibits Osteosarcoma Development via Regulating miR-1182/WNT7B Axis

Background

Osteosarcoma (OS) is a common bone malignancy in children and adolescents. Circular RNAs (circRNAs) have been reported to affect OS progression. This paper mainly delineated the role of circRNA circ_0105346 in OS development and the potential mechanism.

Methods

Quantitative reverse transcription PCR (qRT-PCR) and Western blot assays were applied to detect the expression of circ_0105346, microRNA (miR)-1182 and wingless-type MMTV integration site family 7B (WNT7B). 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay was conducted to evaluate cell viability, and flow cytometry was performed to monitor cell apoptosis and cycle. In addition, cell migration and invasion were determined via transwell assay. Wound healing assay was also employed to evaluate the migrated capacity of OS cells. Western blot assay was also employed to examine the levels of protein markers. Additionally, the interaction between miR-1182 and circ_0105346 or WNT7B was confirmed by the dual-luciferase reporter, RNA immunoprecipitation (RIP) and pull-down assays. Mouse xenograft model was constructed to clarify the effect of circ_0105346 on tumor growth in vivo.

Results

Circ_0105346 and WNT7B were upregulated, while miR-1182 was downregulated in OS tissues and cells. Circ_0105346 knockdown suppressed OS cell proliferation, cell cycle, migration, invasion and glycolysis, as well as accelerated apoptosis, which was attenuated by miR-1182 inhibition. Interestingly, circ_0105346 targeted miR-1182, and miR-1182 interacted with WNT7B. Circ_0105346 could upregulate WNT7B by downregulating miR-1182 expression. Furthermore, circ_0105346 knockdown blocked tumor growth in vivo.

Conclusion

Circ_0105346 knockdown repressed OS progression by regulating miR-1182/WNT7B axis, at least in part.

Oncogenic gene TRIM10 confers resistance to cisplatin in osteosarcoma cells and activates the NF-κB signaling pathway

Deregulation of tripartite motif (TRIM) family proteins contribute to multiple biological processes such as neurodegeneration, development, inflammation, cell survival, apoptosis, and carcinogenesis. However, the biological function and molecular mechanism of TRIM family proteins in osteosarcoma chemoresistance remain unclear. In the current study, we found the protein expression of TRIM10 was markedly overexpressed in cisplatin resistance's osteosarcoma tissues and TRIM10 overexpression was inversely correlated with osteosarcoma patient survival. Furthermore, overexpression of TRIM10 confers cisplatin resistance on osteosarcoma cells; however, repressing TRIM10 sensitized osteosarcoma cell lines to cisplatin cytotoxicity in vitro. Mechanically, TRIM10 upregulated the nuclear levels of p65, thereby activating canonical NF-κB signaling. Taken together, our results suggest that TRIM10 contributed to cisplatin resistance in osteosarcoma cells, and targeting the TRIM10/p65 axis may represent a promising strategy to enhance cisplatin response in osteosarcoma patients with chemoresistance.

Identification and Verification of Immune-Related Gene Prognostic Signature Based on ssGSEA for Osteosarcoma

Osteosarcoma is the most common malignant bone tumor in children and adolescence. Multiple immune-related genes have been reported in different cancers. The aim is to identify an immune-related gene signature for the prospective evaluation of prognosis for osteosarcoma patients. In this study, we evaluated the infiltration of immune cells in 101 osteosarcoma patients downloaded from TARGET using the ssGSEA to the RNA-sequencing of these patients, thus, high immune cell infiltration cluster, middle immune cell infiltration cluster and low immune cell infiltration cluster were generated. On the foundation of high immune cell infiltration cluster vs. low immune cell infiltration cluster and normal vs. osteosarcoma, we found 108 common differentially expressed genes which were sequentially submitted to univariate Cox and LASSO regression analysis. Furthermore, GSEA indicated some pathways with notable enrichment in the high- and low-immune cell infiltration cluster that may be helpful in understanding the potential mechanisms. Finally, we identified seven immune-related genes as prognostic signature for osteosarcoma. Kaplan-Meier analysis, ROC curve, univariate and multivariate Cox regression further confirmed that the seven immune-related genes signature was an innovative and significant prognostic factor independent of clinical features. These results of this study offer a means to predict the prognosis and survival of osteosarcoma patients with uncovered seven-gene signature as potential biomarkers.

Autophagy in Osteosarcoma Cancer Stem Cells Is Critical Process which Can Be Targeted by the Antipsychotic Drug Thioridazine

Simple Summary

Cancer stem cells (CSCs) represent a minor population of cancer cells with stem cell-like properties and appear as a crucial target in oncology as they are the origin of relapses and resistance to current treatments. Autophagy, which allows the degradation and recycling of cellular components for survival purposes, has been shown to be upregulated in some CSCs, participating in the resistance of these cells. The aim of our study was to analyze the autophagy level and the consequences of targeting this process in osteosarcoma CSCs. Our results indicate that autophagy is a critical process in osteosarcoma CSCs and that targeting this pathway allows to switch their fate from survival to death.

Abstract

Cancer stem cells (CSCs) represent a minor population of cancer cells with stem cell-like properties which are able to fuel tumor growth and resist conventional treatments. Autophagy has been described to be upregulated in some CSCs and to play a crucial role by maintaining stem features and promoting resistance to both hostile microenvironments and treatments. Osteosarcoma (OS) is an aggressive bone cancer which mainly affects children and adolescents and autophagy in OS CSCs has been poorly studied. However, this is a very interesting case because autophagy is often deregulated in this cancer. In the present work, we used two OS cell lines showing different autophagy capacities to isolate CSC-enriched populations and to analyze the autophagy in basal and nutrient-deprived conditions. Our results indicate that autophagy is more efficient in CSCs populations compared to the parental cell lines, suggesting that autophagy is a critical process in OS CSCs. We also showed that the antipsychotic drug thioridazine is able to stimulate, and then impair autophagy in both CSC-enriched populations, leading to autosis, a cell death mediated by the Na+/K⁺ ATPase pump and triggered by dysregulated accumulation of autophagosomes. Taken together, our results indicate that autophagy is very active in OS CSCs and that targeting this pathway to switch their fate from survival to death could provide a novel strategy to eradicate these cells in osteosarcoma.

Exosomal PD-L1 and N-cadherin predict pulmonary metastasis progression for osteosarcoma patients

BACKGROUND

Recent studies indicated that exosomal programmed death-ligand 1 (PD-L1) derived from cancers could induce immunosuppression and tumor pathogenesis. However, it is unclear how exosomes influence osteosarcoma (OS) progression and whether PD-L1 also exists in serum exosomes (Sr-exosomes) of patients with osteosarcoma. We examined serum exosomes from 70 OS patients, 9 patients with benign tumors and 22 healthy donors. OS-derived exosomes were functionally evaluated in vivo and in vitro.

RESULTS

The characteristics of exosomes derived from OS patient serum and OS cell lines were confirmed by several methods. We found OS patients had a higher level of exosomal PD-L1 compared to healthy donors. Meanwhile, OS patients with pulmonary metastasis also showed a relatively higher level of exosomal PD-L1 than patients without metastasis. Next, bioinformatic analysis demonstrated that Sr-exosomes isolated from OS patients may involve in the important process of immune function and cancer pathogenesis for OS patients. Co-expression network centered with PD-L1 among Sr-exosomal differently expressed mRNA demonstrated exosomal N-cadherin had a close relationship with exosomal PD-L1 expression. Then, we confirmed higher level of Sr-exosomal N-cadherin in OS patients with pulmonary metastasis compared to ones without metastasis. Furthermore, we elucidated osteosarcoma-derived exosomes and exosomal-PD-L1 promoted the pulmonary metastasis in metastatic models. ROC (Receiver Operating Characteristic Curve) analysis showed AUC (Area Under Curve) of 0.823 for exosomal PD-L1, 0.806 for exosomal N-cadherin and 0.817 for exosomal N-cadherin/E-cadherin to distinguish OS patients with pulmonary metastasis from ones without metastasis.

CONCLUSIONS

Osteosarcoma stimulates pulmonary metastasis by releasing exosomes, that carry PD-L1 and N-cadherin. Detection of exosomal PD-L1 and N-cadherin from serum of OS patients may predict pulmonary metastasis progression for OS patients.

Gamabufotalin suppressed osteosarcoma stem cells through the TGF-β/periostin/PI3K/AKT pathway

AIMS

To investigate the effect of gamabufotalin (GBT) on metastasis and modulation of stemness features in osteosarcoma, and the molecular mechanisms underlying such effects.

METHODS

Human osteosarcoma U2OS/MG-63 cell lines were used in this study. Cell proliferation, migration, and invasion were determined by MTT assay, wound healing assay, and cell invasion assay, respectively. The inhibitive effect of GBT on stemness was assessed by flow cytometry and mammosphere formation. The protein levels of related proteins were detected by western blotting analysis. The effect of GBT on tumorigenicity and metastasis was determined by immunofluorescence staining and immunohistochemistry in vivo experiments.

RESULTS

We found that GBT suppressed the viability of U2OS/MG-63 cells in a time- and dose-dependent manner. Notably, GBT had no effect on the viability of human fetal osteoblastic (hFOB) 1.19 cells. Moreover, GBT increased the width of wounds, reduced the number of invasive osteosarcoma cells and reversed the epithelial-mesenchymal transition phenotype. Notably, we found that, compared with hFOB1.19 cells, the levels of transforming growth factor-β (TGF-β), periostin, phosphorylated-AKT (p-AKT), and phosphorylated-PI3K (p-PI3K) were higher in spheroids group than in parent cells. In addition, GBT reduced the ratio of CD133+ cells, the size of spheroids and Nanog, as well as the protein levels of SRY-box transcription factor 2 (SOX2), and octamer-binding protein 3/4 (OCT3/4). Our in vivo experiments showed that GBT consistently reduced lung metastasis lesions, the expression levels of matrix metalloproteinase 2 (MMP2), TGF-β, periostin, p-AKT, and p-PI3K (immunohistochemistry staining), as well as that of CD133 in tumor tissues (immunofluorescence analysis). From a mechanistic point of view, exogenous TGF-β/periostin/PI3K/AKT overexpression neutralized the reduction of GBT-decreased invasion/migration and the suppression of stemness properties.

CONCLUSION

Collectively, our data demonstrated that GBT inhibited the viability and tumorigenesis capability of osteosarcoma cells by blocking the TGF-β/periostin/PI3K/AKT signaling pathway. Therefore, GBT may represent a promising therapeutic agent for the management of osteosarcoma.

Nanoparticle enhanced combination therapy for stem-like progenitors defined by single-cell transcriptomics in chemotherapy-resistant osteosarcoma

The adaptation of osteosarcoma cells to therapeutic pressure impedes the efficacy of chemotherapy for osteosarcoma. However, the characteristics and cellular organization of therapy-resistant cells in osteosarcoma tumors remain elusive. Here, we utilized single-cell transcriptomics to systematically map the cell-type-specific gene expression in a chemotherapy-resistant osteosarcoma tumor. Our data demonstrated the VEGFR2-JMJD3-abundant subsets as quiescent stem-like cells, thereby establishing the hierarchy of therapy-resistant actively cycling progenitor pools (JMJD3-abundant) in osteosarcoma. VEGFR2 inhibitor and JMJD3 inhibitor synergistically impeded osteosarcoma cell propagation and tumor growth. Although osteosarcoma cells are predisposed to apoptosis induced by the synergistic therapy through activation of the CHOP pro-apoptotic factor via the endoplasmic reticulum (ER) stress, the stem-like/progenitor cells exhibit an adaptive response, leading to their survival. Reduction in cellular glutathione levels in stem-like/progenitor cells caused by the treatment with a glutathione synthesis inhibitor increases ER stress-induced apoptosis. Importantly, the marked therapeutic improvement of synergistic therapy against stem-like/progenitor cells was achieved by using glutathione-scavenging nanoparticles, which can load and release the drug pair effectively. Overall, our study provides a framework for understanding glutathione signaling as one of the therapeutic vulnerabilities of stem-like/progenitor cells. Broadly, these findings revealed a promising arsenal by encapsulating glutathione-scavenging nanoparticles with co-targeting VEGFR2 and JMJD3 to eradicate chemotherapy-resistant osteosarcoma.

N6-Methyladenosine modification of the TRIM7 positively regulates tumorigenesis and chemoresistance in osteosarcoma through ubiquitination of BRMS1

BACKGROUND

Metastasis is the leading cause of death in patients with osteosarcoma. Some of these patients fail to respond to chemotherapy and die of metastasis within a short period. Therefore, it is important to identify novel biomarkers to improve the diagnosis and treatment of osteosarcoma. TRIM7 is a member of the tripartite motif (TRIM) family protein that is involved in various pathological conditions including cancer; however, its role in osteosarcoma remains elusive.

METHODS

Cell proliferation, invasion and migration were measured by CCK-8 and Transwell. Immunoprecipitation and mass spectrometry analysis were used to identify candidate proteins associated with TRIM7. Immunoprecipitation, immunofluorescence, pull down and ubiquitination assay were performed to examine the regulation between TRIM7 and its candidate protein. m6A modification of TRIM7 was measured by RNA immunoprecipitation.

FINDINGS

TRIM7 expression was upregulated in osteosarcoma tissues and was an independent risk factor in predicting poor prognosis. TRIM7 regulates osteosarcoma cell migration and invasion through ubiquitination of breast cancer metastasis suppressor 1 (BRMS1). Moreover, chemoresistance was readily observed in osteosarcoma cells and in patient-derived xenograft (PDX) mice with higher TRIM7 levels. Loss of TRIM7 m6A modification was observed in osteosarcoma tissues. METTL3 and YTHDF2 were the main factors involved in the aberrant m6A modification of TRIM7.

INTERPRETATION

Overall, our findings show that TRIM7 plays a key role in regulating metastasis and chemoresistance in osteosarcoma through ubiquitination of BRMS1.

FUNDING

This work was financially supported by grants of NSFC (81001192, 81672658 and 81972521) and National Key Research Project of Science and Technology Ministry (2016YFC0106204).

Systems Biology Approach Identifies Prognostic Signatures of Poor Overall Survival and Guides the Prioritization of Novel BET-CHK1 Combination Therapy for Osteosarcoma

Osteosarcoma (OS) patients exhibit poor overall survival, partly due to copy number variations (CNVs) resulting in dysregulated gene expression and therapeutic resistance. To identify actionable prognostic signatures of poor overall survival, we employed a systems biology approach using public databases to integrate CNVs, gene expression, and survival outcomes in pediatric, adolescent, and young adult OS patients. Chromosome 8 was a hotspot for poor prognostic signatures. The MYC-RAD21 copy number gain (8q24) correlated with increased gene expression and poor overall survival in 90% of the patients (n = 85). MYC and RAD21 play a role in replication-stress, which is a therapeutically actionable network. We prioritized replication-stress regulators, bromodomain and extra-terminal proteins (BETs), and CHK1, in order to test the hypothesis that the inhibition of BET + CHK1 in MYC-RAD21+ pediatric OS models would be efficacious and safe. We demonstrate that MYC-RAD21+ pediatric OS cell lines were sensitive to the inhibition of BET (BETi) and CHK1 (CHK1i) at clinically achievable concentrations. While the potentiation of CHK1i-mediated effects by BETi was BET-BRD4-dependent, MYC expression was BET-BRD4-independent. In MYC-RAD21+ pediatric OS xenografts, BETi + CHK1i significantly decreased tumor growth, increased survival, and was well tolerated. Therefore, targeting replication stress is a promising strategy to pursue as a therapeutic option for this devastating disease.