Identification of critical genes associated with human osteosarcoma metastasis based on integrated gene expression profiling

Identification of allograft inflammatory factor-1 suppressing the progression and indicating good prognosis of osteosarcoma

BACKGROUND

Osteosarcoma is one of the most common cancers worldwide. Intense efforts have been made to elucidate the pathogeny, but the mechanisms of osteosarcoma are still not well understood. We aimed to investigate the potential biomarker, allograft inflammatory factor-1 (AIF1), affecting the progression and prognosis of osteosarcoma.

METHODS

Three microarray datasets were downloaded from GEO datasets and one was obtained from the TCGA dataset. The differentially expressed genes (DEGs) were identified. GO and KEGG functional enrichment analyses of overlapped DEGs were performed. The PPI network of overlapped DEGs was constructed by STRING and visualized with Cytoscape. Overall survival (OS) and Metastasis free survival (MFS) were analyzed from GSE21257. Finally, the effect of the most relevant core gene affecting the progression of osteosarcoma was examined in vitro.

RESULTS

One hundred twenty six DEGs were identified, consisting of 65 upregulated and 61 downregulated genes. Only AIF1 was significantly associated with OS and MFS. It was found that AIF1 could be enriched into the NF-κB signaling pathway. GSEA and ssGSEA analyses showed that AIF1 was associated with the immune invasion of tumors. Cell experiments showed that AIF1 was underexpressed in osteosarcoma cell lines, while the malignant propriety was attenuated after overexpressing the expression of AIF1. Moreover, AIF1 also affects the expression of the NF-κB pathway.

CONCLUSION

In conclusion, DEGs and hub genes identified in the present study help us understand the molecular mechanisms underlying the carcinogenesis and progression of osteosarcoma, and provide candidate targets for diagnosis and treatment of osteosarcoma.

Exploration of Potential Ewing Sarcoma Drugs from FDA-Approved Pharmaceuticals through Computational Drug Repositioning, Pharmacogenomics, Molecular Docking, and MD Simulation Studies

Novel drug development is a time-consuming process with relatively high debilitating costs. To overcome this problem, computational drug repositioning approaches are being used to predict the possible therapeutic scaffolds against different diseases. In the current study, computational drug repositioning approaches were employed to fetch the promising drugs from the pool of FDA-approved drugs against Ewing sarcoma. The binding interaction patterns and conformational behaviors of screened drugs within the active region of Ewing sarcoma protein (EWS) were confirmed through molecular docking profiles. Furthermore, pharmacogenomics analysis was employed to check the possible associations of selected drugs with Ewing sarcoma genes. Moreover, the stability behavior of selected docked complexes (drugs-EWS) was checked by molecular dynamics simulations. Taken together, astemizole, sulfinpyrazone, and pranlukast exhibited a result comparable to pazopanib and can be used as a possible therapeutic agent in the treatment of Ewing sarcoma.

Comprehensive Analysis of Potential Correlation Between Solute Carrier 1A (SLC1A) Family and Lung Adenocarcinoma

Background

Lung adenocarcinoma (LUAD) is the most common dangerous malignant tumor and the leading cause of global cancer incidence and mortality. The Solute Carrier 1A (SLC1A) family play a significant part in cellular biological process, inflammation, and immunity. Specific functions of the SLC1A family in lung cancer are still not systematically described.

Objective

This study aimed to explore the best biological understanding of SLC1A family in lung cancer.

Methods

To study the expression and role of the SLC1A family in lung cancer, researchers used a variety of bioinformatics databases and tools.

Results

Aberrant expression of SLC1A family genes were demonstrated and analyzed the association with gender, tumor grade, cancer stages, and nodal metastasis status. The ectopic expression of SLC1A family genes has prognostic value for LUAD patients. Immune infiltration revealed a significant correlation between SLC1A family genes expression in LUAD. SLC1A family genes were involved in manifold biological processes and have different levels of DNA methylation and genetic alteration.

Conclusions

These findings suggested that members of the SLC1A family could be a potential target for the development of LUAD therapeutics as well as a reliable indicator of LUAD prognostic value.

Identification of Key Genes and Pathways in Osteosarcoma by Bioinformatics Analysis

Purpose

Osteosarcoma (OS) is the most primary bone malignant tumor in adolescents. Although the treatment of OS has made great progress, patients' prognosis remains poor due to tumor invasion and metastasis.

Materials and Methods

We downloaded the expression profile GSE12865 from the Gene Expression Omnibus database. We screened differential expressed genes (DEGs) by making use of the R limma software package. Based on Gene Ontology, Kyoto Encyclopedia of Genes and Genomes, and Gene Set Enrichment Analysis, we performed the function and pathway enrichment analyses. Then, we constructed a Protein-Protein Interaction network and screened hub genes through the Search Tool for the Retrieval of Interacting Genes.

Result

By analyzing the gene expression profile GSE12865, we obtained 703 OS-related DEGs, which contained 166 genes upregulated and 537 genes downregulated. The DEGs were primarily abundant in ribosome, cell adhesion molecules, ubiquitin-ubiquitin ligase activity, and p53 signaling pathway. The hub genes of OS were KDR, CDH5, CD34, CDC42, RBX1, POLR2C, PPP2CA, and RPS2 through PPI network analysis. Finally, GSEA analysis showed that cell adhesion molecules, chemokine signal pathway, transendothelial migration, and focal adhesion were associated with OS.

Conclusion

In this study, through analyzing microarray technology and bioinformatics analysis, the hub genes and pathways about OS are identified, and the new molecular mechanism of OS is clarified.

A novel 14-gene signature for overall survival in lung adenocarcinoma based on the Bayesian hierarchical Cox proportional hazards model

There have been few investigations of cancer prognosis models based on Bayesian hierarchical models. In this study, we used a novel Bayesian method to screen mRNAs and estimate the effects of mRNAs on the prognosis of patients with lung adenocarcinoma. Based on the identified mRNAs, we can build a prognostic model combining mRNAs and clinical features, allowing us to explore new molecules with the potential to predict the prognosis of lung adenocarcinoma. The mRNA data (n = 594) and clinical data (n = 470) for lung adenocarcinoma were obtained from the TCGA database. Gene set enrichment analysis (GSEA), univariate Cox proportional hazards regression, and the Bayesian hierarchical Cox proportional hazards model were used to explore the mRNAs related to the prognosis of lung adenocarcinoma. Multivariate Cox proportional hazard regression was used to identify independent markers. The prediction performance of the prognostic model was evaluated not only by the internal cross-validation but also by the external validation based on the GEO dataset (n = 437). With the Bayesian hierarchical Cox proportional hazards model, a 14-gene signature that included CPS1, CTPS2, DARS2, IGFBP3, MCM5, MCM7, NME4, NT5E, PLK1, POLR3G, PTTG1, SERPINB5, TXNRD1, and TYMS was established to predict overall survival in lung adenocarcinoma. Multivariate analysis demonstrated that the 14-gene signature (HR 3.960, 95% CI 2.710–5.786), T classification (T₁, reference; T₃, HR 1.925, 95% CI 1.104–3.355) and N classification (N₀, reference; N₁, HR 2.212, 95% CI 1.520–3.220; N₂, HR 2.260, 95% CI 1.499–3.409) were independent predictors. The C-index of the model was 0.733 and 0.735, respectively, after performing cross-validation and external validation, a nomogram was provided for better prediction in clinical application. Bayesian hierarchical Cox proportional hazards models can be used to integrate high-dimensional omics information into a prediction model for lung adenocarcinoma to improve the prognostic prediction and discover potential targets. This approach may be a powerful predictive tool for clinicians treating malignant tumours.

Immunohistochemical Characterisation of GLUT1, MMP3 and NRF2 in Osteosarcoma

Osteosarcoma (OSA) is an aggressive bone malignancy. Unlike many other malignancies, OSA outcomes have not improved in recent decades. One challenge to the development of better diagnostic and therapeutic methods for OSA has been the lack of well characterized experimental model systems. Spontaneous OSA in dogs provides a good model for the disease seen in people and also remains an important veterinary clinical challenge. We recently used RNA sequencing and qRT-PCR to provide a detailed molecular characterization of OSA relative to non-malignant bone in dogs. We identified differential mRNA expression of the solute carrier family 2 member 1 (SLC2A1/GLUT1), matrix metallopeptidase 3 (MMP3) and nuclear factor erythroid 2–related factor 2 (NFE2L2/NRF2) genes in canine OSA tissue in comparison to paired non-tumor tissue. Our present work characterizes protein expression of GLUT1, MMP3 and NRF2 using immunohistochemistry. As these proteins affect key processes such as Wnt activation, heme biosynthesis, glucose transport, understanding their expression and the enriched pathways and gene ontologies enables us to further understand the potential molecular pathways and mechanisms involved in OSA. This study further supports spontaneous OSA in dogs as a model system to inform the development of new methods to diagnose and treat OSA in both dogs and people.

Identification of Gene as Predictive Biomarkers for the Occurrence and Recurrence of Osteosarcoma

Purpose

Osteosarcoma is the most common malignant bone cancer affecting adolescents and young adults. This study aimed to screen potential diagnostic and therapeutic markers for osteosarcoma.

Methods

Differential expression analysis between osteosarcoma and control was performed in GSE99671, the differentially expressed genes (DEGs) were subjected to co-expression analysis. Enrichment analysis was employed to identify the biological functions and KEGG signaling pathways of module genes. In addition, a differential analysis was also performed between recurrent and non-recurrent osteosarcoma samples in GSE39055, and enrichment analysis was performed for DEGs. Further, Kaplan–Meier curve analysis was performed on the module genes, and receiver operating characteristic (ROC) curve was drawn. Comparison of the module with the highest correlation to osteosarcoma identified key genes. Cox regression model was utilized to identify the predictive ability of key genes for the prognosis of osteosarcoma.

Results

A total of 13 co-expression modules were identified from 4871 DEGs of GSE99671, module 1 had the highest positive correlation with osteosarcoma. Module genes were mainly enriched in autophagy and macrophage migration functions. A total of 1126 DEGs were obtained from GSE39055, significantly involved in neutrophil mediated immunity. Screening of genes with area under the ROC curve (AUC) values greater than 0.73 in both GSE99671 and GSE39055 identified 5 key genes when compared with genes from module 1. The nomogram results showed that ATF5, CHCHD8, ENOPH1, and LOC286367 might predict 5-year or 8-year survival time of osteosarcoma patients. The Cox model results confirmed that the signals of ATF5, CHCHD8, and LOC286367 were robust, and it may be used in the diagnosis, treatment, and prognosis of osteosarcoma.

Conclusion

We found that ATF5, CHCHD8, and LOC286367 can effectively identify osteosarcoma tumorigenesis and even recurrence status. This is helpful for early diagnosis and treatment, improving the clinical treatment of patients with osteosarcoma.

A model of twenty-three metabolic-related genes predicting overall survival for lung adenocarcinoma

Background

The highest rate of cancer-related deaths worldwide is from lung adenocarcinoma (LUAD) annually. Metabolism was associated with tumorigenesis and cancer development. Metabolic-related genes may be important biomarkers and metabolic therapeutic targets for LUAD.

Materials and Methods

In this study, the gleaned cohort included LUAD RNA-SEQ data from the Cancer Genome Atlas (TCGA) and corresponding clinical data (n = 445). The training cohort was utilized to model construction, and data from the Gene Expression Omnibus (GEO, GSE30219 cohort, n = 83; GEO, GSE72094, n = 393) were regarded as a testing cohort and utilized for validation. First, we used a lasso-penalized Cox regression analysis to build a new metabolic-related signature for predicting the prognosis of LUAD patients. Next, we verified the metabolic gene model by survival analysis, C-index, receiver operating characteristic (ROC) analysis. Univariate and multivariate Cox regression analyses were utilized to verify the gene signature as an independent prognostic factor. Finally, we constructed a nomogram and performed gene set enrichment analysis to facilitate subsequent clinical applications and molecular mechanism analysis.

Result

Patients with higher risk scores showed significantly associated with poorer survival. We also verified the signature can work as an independent prognostic factor for LUAD survival. The nomogram showed better clinical application performance for LUAD patient prognostic prediction. Finally, KEGG and GO pathways enrichment analyses suggested several especially enriched pathways, which may be helpful for us investigative the underlying mechanisms.

circKMT2D contributes to H2O2-attenuated osteosarcoma progression via the miR-210/autophagy pathway

Circular RNAs (circRNAs) have been demonstrated to be involved in osteosarcoma (OS) development; however, the underlying mechanism of circKMT2D in OS progression remains unclear. The present study aimed to elucidate how circKMT2D could affect hydrogen peroxide (H₂O₂)-induced OS progression. H₂O₂ (100 µmol/l) was used to treat MG63 and U2OS cells. The cell viability, invasive ability, apoptosis and circKMT2D expression were detected using Cell Counting Kit-8 assay, Transwell assay, flow cytometry and reverse transcription-quantitative PCR, respectively. Furthermore, MG63 and U2OS cells transfected with circKMT2D short hairpin RNA and negative control were treated with H₂O₂, and circKMT2D expression and cell phenotype were determined. Dual-luciferase reporter assay was conducted to determine the association between circKMT2D and miR-210 expression level. Rescue experiments were conducted to examine the mechanisms through which circKMT2D and miR-210 could affect H₂O₂-treated MG63 cells. In addition, the effects of miR-210 on the expression of the autophagy-related proteins Beclin1 and p62 in H₂O₂-treated MG63 cells were detected by western blotting. An autophagy inhibitor was used to treat the MG63 cells, and whether miR-210 could affect the H₂O₂-treated MG63 cell phenotype through autophagy was investigated. The results demonstrated that H₂O₂ treatment promoted cell apoptosis and decreased cell viability, invasive ability and circKMT2D expression in MG63 and U2OS cells. Furthermore, circKMT2D knockdown decreased the cell viability and invasive ability and enhanced the apoptosis of H₂O₂-treated MG63 and U2OS cells. circKMT2D possessed binding sites for miR-210 and inhibited miR-210 expression. In H₂O₂-treated MG63 cells, miR-210 silencing partially reversed the circKMT2D knockdown-induced cell viability inhibition and apoptosis promotion. In addition, miR-210 elevated Beclin1 expression and decreased p62 expression in H₂O₂-treated MG63 cells. The use of the autophagy inhibitor partially reversed the miR-210 overexpression-induced promotion of apoptosis and inhibition of the viability and invasive ability of H₂O₂-treated MG63 cells. Taken together, these findings indicated that circKMT2D knockdown may contribute to the inhibition of H₂O₂-attenuated OS progression via miR-210/autophagy pathway.

MiR-25-3p Serves as an Oncogenic MicroRNA by Downregulating the Expression of Merlin in Osteosarcoma

PURPOSE

Moesin-ezrin-radixin-like protein (Merlin) has been identified as a tumor suppressor in several types of cancers. However, the biological function of Merlin in osteosarcoma remains unclear. MicroRNAs (miRNAs) can influence cancer progression by targeting oncogenes or anti-oncogenes. In this study, we sought to evaluate the regulation of Merlin expression by miR-25-3p and the role of the miR-25-3p/Merlin axis in osteosarcoma progression, with the aim of identifying a potential therapeutic target for osteosarcoma.

MATERIALS AND METHODS

TCGA (The Cancer Genome Atlas) database was used to analyze the correlation between Merlin expression and prognosis. RT-qPCR and Western blotting analyses were performed to compare Merlin expression between normal and malignant cells. A dual-luciferase reporter assay was performed to evaluate the direct targeting of Merlin by miR-25-3p. We overexpressed miR-25-3p, or/and Merlin, in U-2 OS and 143B cells, and studied their cellular functions in vitro. MTT and colony formation assays were performed to determine the effects on cell growth. EdU and cell cycle assays were performed to analyze the effects in cell replication. We used annexin V-fluorescein isothiocyanate and propidium iodide to stain apoptotic cells, and analyzed the cells using flow cytometry. The effects on cell metastasis were studied in wound healing and transwell assays. Lastly, the underlying mechanism was determined in RT-qPCR and Western blotting experiments.

RESULTS

Low Merlin expression was linked to poor prognosis. miR-25-3p was observed to directly target Merlin and downregulate its expression. miR-25-3p promoted cell growth, migration, and invasion, and inhibited apoptosis induced by cisplatin. Moreover, the overexpression of Merlin reversed the abovementioned effects of miR-25-3p. Further, the miR-25-3p/Merlin axis was observed to play an important role in the Hippo pathway, and regulated the expression of genes such as BIRC5, CTGF, and CYR61.

CONCLUSION

miR-25-3p functions as an oncogenic microRNA in osteosarcoma by targeting Merlin, and may serve as a potential therapeutic target for osteosarcoma.

MicroRNA-431-5p Inhibits the Tumorigenesis of Osteosarcoma Through Targeting PANX3

Purpose

This study aimed to evaluate the regulatory role of miR-431-5p on the tumorigenesis of osteosarcoma (OS) and the underlying mechanism involving pannexin 3 (PANX3).

Methods

qRT-PCR was applied to measure the expression of miR-431-5p in OS tissues and cells. PANX3 and miR-431-5p were overexpressed in U2OS and HOS cells. The cell viability and apoptosis were determined by MTT and FITC/PI double staining assay, respectively. Transwell assay was performed to detect cell migration and invasion. The protein expression of cleave-caspase-3 and MMP-2/-9 was detected by Western blot. The target relationship between miR-431-5p and PANX3 was predicated by ENCORI and identified by DLR assay. The anti-tumor effect of miR-431-5p was further analyzed in a xenograft tumor model in mice.

Results

MiR-431-5p expression was down-regulated in OS tissues and negatively correlated with lymph node metastasis and TNM stage. Over-expression of miR-431-5p induced cell apoptosis, inhibited cell proliferation, migration and invasion, up-regulated cleave-caspase-3, and down-regulated MMP-2 and -9 in OS cells. Over-expression of miR-431-5p also inhibited the growth of tumor xenografts in mice. In addition, PANX3 was a target of miR-431-5p. Over-expression of PANX3 reversed the anti-tumor effect of miR-431-5p mimics on U2OS and HOS cells.

Conclusion

Up-regulation of miR-431-5p suppressed the tumorigenesis of OS via targeting PANX3.

Long non‑coding RNA NR2F1‑AS1 facilitates the osteosarcoma cell malignant phenotype via the miR‑485‑5p/miR‑218‑5p/BIRC5 axis

Long non-coding RNA (lncRNA) NR2F1 antisense RNA 1 (NR2F1-AS1) has been reported to be an oncogene in several cancer types, including osteosarcoma (OS). However, the underlying fundamental molecular mechanism of NR2F1-AS1 in OS remains largely unknown, which the present study aimed to elucidate. The present study demonstrated that NR2F1-AS1 expression is markedly increased in OS, and NR2F1-AS1 was shown to exert oncogenic functions in OS. Further molecular mechanistic studies revealed that microRNA (miR)-485-5p and miR-218-5p were direct targets of NR2F1-AS1. More importantly, miR-485-5p and miR-218-5p exhibited low expression levels and were negatively correlated with NR2F1-AS1 expression in OS tissues. It was then identified that baculoviral inhibitor of apoptosis repeat-containing 5 (BIRC5) was a direct target of miR-485-5p and miR-218-5p in OS cells. Furthermore, a series of experiments suggested that NR2F1-AS1 affects the proliferation, migration, invasion and apoptosis of OS cells by regulating BIRC5. Finally, it was revealed that silencing of NR2F1-AS1 repressed the OS cell malignant phenotype by binding with miR-485-5p and miR-218-5p, and then downregulating BIRC5 expression, which suggests that the NR2F1-AS1/miR-485-5p/miR-218-5p/BIRC5 axis could be a potential target for treating OS.

Increased DEF6 expression is correlated with metastasis and poor prognosis in human osteosarcoma

Metastasis is the primary cause of high mortality in patients with osteosarcoma (OS). However, the molecular mechanisms underlying the regulation of metastatic disease are yet to be determined. Differentially expressed in FDCP 6 homolog (DEF6) has been demonstrated to be correlated with the metastatic behavior of several cancers, such as breast, ovarian and colorectal cancers. However, the role of DEF6 in OS remains unknown. Accordingly, the current study aimed to investigate the relationship between DEF6 expression and the malignant behavior of OS. The results revealed that high levels of DEF6 in OS tissues were associated with advanced clinical stage and metastases. Furthermore, immunohistochemistry results predicted a poor prognosis in 58 human OS specimens. Additionally, DEF6 expression was reported to be upregulated in human OS cell lines compared with a normal osteoblast cell line. small interfering RNA transfection, cell proliferation and colony formation assays, wound healing assays and Transwell assays were performed. DEF6 was not identified to be a major driver of OS cell proliferation, but it significantly contributed to metastatic potential in vitro. In addition, bioinformatics, western blotting and immunohistochemistry results indicated that MMP9 expression was positively correlated with DEF6 expression in human OS. To summarize, the results revealed that increased levels of DEF6 were associated with metastasis and poor prognosis in human OS and that DEF6 expression is positively correlated with MMP9 expression. The results indicated that DEF6 may serve as a potential antimetastatic target for OS.

SLC1A1, SLC16A9, and CNTN3 Are Potential Biomarkers for the Occurrence of Colorectal Cancer

Background

This study is aimed at identifying unknown clinically relevant genes involved in colorectal cancer using bioinformatics analysis.

Methods

Original microarray datasets GSE107499 (ulcerative colitis), GSE8671 (colorectal adenoma), and GSE32323 (colorectal cancer) were downloaded from the Gene Expression Omnibus. Common differentially expressed genes were filtered from the three datasets above. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses were performed, followed by construction of a protein-protein interaction network to identify hub genes. Kaplan-Meier survival analysis and TIMER database analysis were used to screen the genes related to the prognosis and tumour-infiltrating immune cells of colorectal cancer. Receiver operating characteristic curves were used to assess whether the genes could be used as markers for the diagnosis of ulcerative colitis, colorectal adenoma, and colorectal cancer.

Results

A total of 237 differentially expressed genes common to the three datasets were identified, of which 60 were upregulated, 125 were downregulated, and 52 genes that were inconsistently up- and downregulated. Common differentially expressed genes were mainly enriched in the cellular component of extracellular exosome and integral component of membrane categories. Eight hub genes, i.e., CXCL3, CXCL8, CEACAM7, CNTN3, SLC1A1, SLC16A9, SLC4A4, and TIMP1, were related to the prognosis and tumour-infiltrating immune cells of colorectal cancer, and these genes have diagnostic value for ulcerative colitis, colorectal adenoma, and colorectal cancer.

Conclusion

Three novel genes, CNTN3, SLC1A1, and SLC16A9 were shown to have diagnostic value with respect to the occurrence of colorectal cancer and should be verified in future studies.

Identification of hub methylated-CpG sites and associated genes in oral squamous cell carcinoma

To improve personalized diagnosis and prognosis for oral squamous cell carcinoma (OSCC) by identification of hub methylated‐CpG sites and associated genes, weighted gene comethylation network analysis (WGCNA) was performed to examine and identify hub modules and CpG sites correlated with OSCC. Here, WGCNA modeling yielded blue and brown comethylation modules that were significantly associated with OSCC status. Following screening of the differentially expressed genes (DEGs) from gene expression microarrays and differentially methylated‐CpG sites (DCGs), integrated multiomics analysis of the DEGs, DCGs, and hub CpG sites from the modules was performed to investigate their correlations. Expression levels of 16 CpG sites‐associated genes were negatively correlated with methylation patterns of promoter. Moreover, Kaplan‐Meier survival analysis of the hub CpG sites and associated genes was carried out using 2 public databases, MethSurv and GEPIA. Only 5 genes, ACTA1, ACTN2, OSR1, SYNGR1, and ZNF677, had significant overall survival using GEPIA. Hypermethylated‐CpG sites ACTN2‐cg21376883 and OSR1‐cg06509239 were found to be associated with poor survival by MethSurv. Methylation status of specific site and expression levels of associated genes were determined using clinical samples by quantitative methylation‐specific PCR and real‐time PCR. Pearson's correlation analysis showed that methylation levels of cg06509239 and cg18335068 were negatively related to OSR1 and ZNF677 expression levels, respectively. Our classification schema using multiomics analysis represents a screening framework for identification of hub CpG sites and associated genes.

Coupled structural transitions enable highly cooperative regulation of human CTPS2 filaments

Many enzymes assemble into defined oligomers, providing a mechanism for cooperatively regulating activity. Recent studies have described a mode of regulation in which enzyme activity is modulated by polymerization into large-scale filaments. Here we describe an ultrasensitive form of polymerization-based regulation employed by human CTP synthase 2 (CTPS2). Cryo-EM structures reveal that CTPS2 filaments dynamically switch between active and inactive forms in response to changes in substrate and product levels. Linking the conformational state of many CTPS2 subunits in a filament results in highly cooperative regulation, greatly exceeding the limits of cooperativity for the CTPS2 tetramer alone. The structures reveal a link between conformation and control of ammonia channeling between the enzyme’s active sites, and explain differences in regulation of human CTPS isoforms. This filament-based mechanism of enhanced cooperativity demonstrates how the widespread phenomenon of enzyme polymerization can be adapted to achieve different regulatory outcomes.

LncRNA SPRY4‑IT1 promotes progression of osteosarcoma by regulating ZEB1 and ZEB2 expression through sponging of miR‑101 activity

Long non‑coding (lnc)RNA sprouty receptor tyrosine kinase signalling antagonist 4‑intronic transcript 1 (SPRY4‑IT1) has been demonstrated to serve a critical role in the tumorigenesis of osteosarcoma (OS); however, the specific underlying mechanism remains unclear. The aim of the present study was to examine the interactions between SPRY4‑IT1 and its downstream effectors, to determine if any of the interactions contributed to SPRY4‑IT1‑mediated proliferation, migration and invasion in cancer cells. A signalling cascade which involved SPRY4‑IT1, miR‑101 and zinc finger E‑box‑binding homeoboxes (ZEBs) was examined in the present study. Intracellular SPRY4‑IT1 and miR‑101 expression levels were altered through transfection to assess their effect on proliferation, cell cycle progression, survival, migration and invasion. A dual‑luciferase assay was utilized to determine the association between SPRY4‑IT1/miR‑101 and ZEBs/miR‑101 and nude mouse xenograft experiments were performed to determine the effect of SPRY4‑IT1 in vivo. The results indicated that the SPRY4‑IT1 levels were negatively associated with miR‑101 expression levels in OS cells, an association which was not observed in the normal osteoblast cells. SPRY4‑IT1 knockdown or miR‑101 overexpression reduced proliferation, cell cycle progression, survival, migration and invasion of MG‑63 and U2OS cells. SPRY4‑IT1 knockdown was accompanied by increased expression of miR‑101 and E‑cadherin levels, as well as decreased expression levels of ZEB1/2 and other epithelial‑mesenchymal transition‑associated proteins. Simultaneous knockdown of SPRY4‑IT1 and inhibition of miR‑101 partially reversed the anti‑tumour effects of SPRY4‑IT1 inhibition in vitro. Consistent with these findings, short hairpin RNA targeting SPRY4‑IT1 also hindered xenograft tumour growth and altered the levels of miR‑101, ZEB1/2 and E‑cadherin in vivo. Dual‑luciferase reporter assays demonstrated that SPRY4‑IT1 may have regulated the expression of ZEB1 and ZEB2 by sponging miR‑101. In conclusion, SPRY4‑IT1 inhibition increased miR‑101 levels, resulting in downregulation of ZEB1/2 expression and thus exerting anti‑tumour effects in OS.

In-Vitro and In-Vivo Establishment and Characterization of Bioluminescent Orthotopic Chemotherapy-Resistant Human Osteosarcoma Models in NSG Mice

Osteosarcoma, the most common bone malignancy with a peak incidence at adolescence, had no survival improvement since decades. Persistent problems are chemo-resistance and metastatic spread. We developed in-vitro osteosarcoma models resistant to chemotherapy and in-vivo bioluminescent orthotopic cell-derived-xenografts (CDX). Continuous increasing drug concentration cultures in-vitro resulted in five methotrexate (MTX)-resistant and one doxorubicin (DOXO)-resistant cell lines. Resistance persisted after drug removal except for MG-63. Different resistance mechanisms were identified, affecting drug transport and action mechanisms specific to methotrexate (RFC/SCL19A1 decrease, DHFR up-regulation) for MTX-resistant lines, or a multi-drug phenomenon (PgP up-regulation) for HOS-R/DOXO. Differential analysis of copy number abnormalities (aCGH) and gene expression (RNAseq) revealed changes of several chromosomic regions translated at transcriptomic level depending on drug and cell line, as well as different pathways implicated in invasive and metastatic potential (e.g., Fas, Metalloproteinases) and immunity (enrichment in HLA cluster genes in 6p21.3) in HOS-R/DOXO. Resistant-CDX models (HOS-R/MTX, HOS-R/DOXO and Saos-2-B-R/MTX) injected intratibially into NSG mice behaved as their parental counterpart at primary tumor site; however, they exhibited a slower growth rate and lower metastatic spread, although they retained resistance and CGH main characteristics without drug pressure. These models represent valuable tools to explore resistance mechanisms and new therapies in osteosarcoma.