miR-513a-5p regulates radiosensitivity of osteosarcoma by targeting human apurinic/apyrimidinic endonuclease

Inhibitors of APE1 redox and ATM synergistically sensitize osteosarcoma cells to ionizing radiation by inducing ferroptosis

The resistance of osteosarcoma (OS) to ionizing radiation (IR) is an obstacle for effective patient treatment. Apurinic/apyrimidinic endonuclease-reduction/oxidation factor 1 (APE1/Ref-1) is a multifunctional protein with DNA repair and reduction/oxidation (redox) activities. We previously revealed the role of APE1 in OS radioresistance; however, whether the redox activity of APE1 is involved in OS radioresistance is unclear. APE1 regulates the activation of ataxia-telangiectasia mutated (ATM), an initiator of DNA damage response that mediates radioresistance in other cancers. The role of APE1 redox activity and ATM activation in OS radioresistance is unknown. Our study revealed that IR increased APE1 expression and ATM activation in OS cells, and APE1 directly regulated ATM activation by its redox activity. The combined use of an APE1 redox inhibitor and ATM inhibitor effectively sensitized OS cells to IR in vitro and in vivo. Mechanistically, the increased radiosensitization of OS cells by the combined use of the two inhibitors was mediated by increased ferroptosis. Co-treatment with the two inhibitors significantly decreased expression of the common targeted transcription factor P53 compared with single inhibitor treatment. Collectively, APE1 redox activity, ATM activation and their crosstalk play important roles in the resistance of OS to irradiation. Synergetic inhibition of APE1 redox activity and ATM activation sensitized OS cells to IR by inducing ferroptosis, which provides a promising strategy for OS radiotherapy.

Radiotherapy in bone sarcoma: the quest for better treatment option

Bone sarcomas are rare tumors representing 0.2% of all cancers. While osteosarcoma and Ewing sarcoma mainly affect children and young adults, chondrosarcoma and chordoma have a preferential incidence in people over the age of 40. Despite this range in populations affected, all bone sarcoma patients require complex transdisciplinary management and share some similarities. The cornerstone of all bone sarcoma treatment is monobloc resection of the tumor with adequate margins in healthy surrounding tissues. Adjuvant chemo- and/or radiotherapy are often included depending on the location of the tumor, quality of resection or presence of metastases. High dose radiotherapy is largely applied to allow better local control in case of incomplete primary tumor resection or for unresectable tumors. With the development of advanced techniques such as proton, carbon ion therapy, radiotherapy is gaining popularity for the treatment of bone sarcomas, enabling the delivery of higher doses of radiation, while sparing surrounding healthy tissues. Nevertheless, bone sarcomas are radioresistant tumors, and some mechanisms involved in this radioresistance have been reported. Hypoxia for instance, can potentially be targeted to improve tumor response to radiotherapy and decrease radiation-induced cellular toxicity. In this review, the benefits and drawbacks of radiotherapy in bone sarcoma will be addressed. Finally, new strategies combining a radiosensitizing agent and radiotherapy and their applicability in bone sarcoma will be presented.

Revisiting Two Decades of Research Focused on Targeting APE1 for Cancer Therapy: The Pros and Cons

APE1 is an essential endodeoxyribonuclease of the base excision repair pathway that maintains genome stability. It was identified as a pivotal factor favoring tumor progression and chemoresistance through the control of gene expression by a redox-based mechanism. APE1 is overexpressed and serum-secreted in different cancers, representing a prognostic and predictive factor and a promising non-invasive biomarker. Strategies directly targeting APE1 functions led to the identification of inhibitors showing potential therapeutic value, some of which are currently in clinical trials. Interestingly, evidence indicates novel roles of APE1 in RNA metabolism that are still not fully understood, including its activity in processing damaged RNA in chemoresistant phenotypes, regulating onco-miRNA maturation, and oxidized RNA decay. Recent data point out a control role for APE1 in the expression and sorting of onco-miRNAs within secreted extracellular vesicles. This review is focused on giving a portrait of the pros and cons of the last two decades of research aiming at the identification of inhibitors of the redox or DNA-repair functions of APE1 for the definition of novel targeted therapies for cancer. We will discuss the new perspectives in cancer therapy emerging from the unexpected finding of the APE1 role in miRNA processing for personalized therapy.

A spotlight on the interplay of signaling pathways and the role of miRNAs in osteosarcoma pathogenesis and therapeutic resistance

Osteosarcoma (OS) is one of the most common bone cancers that constantly affects children, teenagers, and young adults. Numerous epigenetic elements, such as miRNAs, have been shown to influence OS features like progression, initiation, angiogenesis, and treatment resistance. The expression of numerous genes implicated in OS pathogenesis might be regulated by miRNAs. This effect is ascribed to miRNAs' roles in the invasion, angiogenesis, metastasis, proliferation, cell cycle, and apoptosis. Important OS-related mechanistic networks like the WNT/b-catenin signaling, PTEN/AKT/mTOR axis, and KRAS mutations are also affected by miRNAs. In addition to pathophysiology, miRNAs may influence how the OS reacts to therapies like radiotherapy and chemotherapy. With a focus on how miRNAs affect OS signaling pathways, this review seeks to show how miRNAs and OS are related.

Non-coding RNAs in metabolic reprogramming of bone and soft tissue sarcoma: Fundamental mechanism and clinical implication

Sarcomas, comprising approximately 1% of human malignancies, show a poor response to treatment and easy recurrence. Metabolic reprogramming play an important role in tumor development in sarcomas. Accumulating evidence shows that non-coding RNAs (ncRNAs) participate in regulating the cellular metabolism of sarcomas, which improves the understanding of the development of therapy-resistant tumors. This review addresses the regulatory roles of metabolism-related ncRNAs and their implications for sarcoma initiation and progression. Dysregulation of metabolism-related ncRNAs is common in sarcomas and is associated with poor survival. Emerging studies show that abnormal expression of metabolism-related ncRNAs affects cellular metabolism, including glucose, lipid, and mitochondrial metabolism, and leads to the development of aggressive sarcomas. This review summarizes recent advances in the roles of dysregulated metabolism-related ncRNAs in sarcoma development and stemness and describes their potential to serve as biological biomarkers for disease diagnosis and prognosis prediction, as well as therapeutic targets for treating refractory sarcomas.

Circular RNA Sec61 subunit alpha isoform 1 by competitive absorption of microRNA-513a-5p mediates peroxisomal biogenesis factor 5 expression and promotes the malignant phenotype of non-small cell lung cancer

Circular RNAs (circRNAs) are functional RNAs in the development and metabolism of non-small cell lung cancer (NSCLC). Therein, this paper particularly elucidated the circRNA SEC61 subunit alpha isoform 1 (circSEC61A1) in NSCLC has not been fully elucidated. Clinical analysis of circSEC61A1 expression was performed on specimens collected from 51 patients with primary NSCLC, together with patients' survival. Cell experiments were performed after interfering with circSEC61A1, microRNA (miR)-513a-5p, and peroxisomal biogenesis factor 5 (PEX5) expression, respectively, and cell malignant phenotypes and aerobic glycolysis were evaluated, as well as epithelial-to-mesenchymal transition (EMT)-related markers and Wnt/β-catenin pathway. Xenografts experiments studied the performance of circSEC61A1 in vivo. The downstream molecules of circSEC61A1 were searched. Our data demonstrated that circSEC61A1 was upregulated in NSCLC patients, showing an association with poorer survival outcomes. In cell experiments, circSEC61A1 overexpression promoted NSCLC malignant phenotypes, glycolysis, EMT, and Wnt/β-catenin pathway activation, whereas circSEC61A1 underexpression did the opposite. Knockdown of circSEC61A1 limited tumor growth and metastasis. Furthermore, circSEC61A1 could regulate PEX5 expression through competitive absorption of miR-513a-5p. Generally, circSEC61A1 is a potential biomarker for NSCLC, and circSEC61A1 serves tumor-promoting action in the progression of NSCLC.

circRNA PLOD2 promotes tumorigenesis and Warburg effect in colon cancer by the miR-513a-5p/SIX1/LDHA axis

Increasing evidence has proved that circRNAs might act as potential biomarkers for tumor diagnosis and prognosis. However, the functions and mechanisms of multiple circRNAs in colon cancer remains unclear. Here, we found circPLOD2 was dramatically upregulated in colon cancer tissue and cell lines. In vitro CCK-8, colony formation and transwell assays, and in vivo tumor transplantation assay were performed and explored that circPLOD2 might promote tumor proliferation, migration and invasion in vitro and in vivo. Moreover, based on the analysis of RNA pull-down, RNA immunoprecipitation, luciferase and rescued assays, we confirmed that the interactions between circPLOD2, miR-513a-5p and SIX1. It suggested that circPLOD2 acted as a sponge of miR-513a-5p to regulate the activation of the target gene SIX1. In addition, as a key transcription factor of Warburg effect related genes, SIX1 was proved to enhance the transcriptional expression of LDHA by chromatin immunoprecipitation assay, thereby regulating glycolysis in colon cancer cells. Therefore, we identified that circPLOD2 promoted colon cancer progression through miR-513a-5p/SIX1/LDHA axis, and acted as a new biomarker for colon cancer prognosis and treatment.

Novel insights into host responses to Japanese Encephalitis Virus infection: Reanalysis of public transcriptome and microRNAome datasets

PURPOSE

Japanese encephalitis (JE), caused by the Japanese encephalitis virus (JEV), is the principal cause of viral encephalitis in South-East Asian and Western Pacific countries; accounting for 68,000 cases, and up to 20,400 fatalities, annually across the world. Despite being a high-risk condition, there is no specific treatment for JE. Given rapid additions in genomics databases and the power of data reanalysis in addressing critical medical questions, the present study was designed to identify novel host factors that might have potential roles in JEV infection.

METHODS

We extracted microarray and RNA-Seq data sets from NCBI-GEO and compared mock and JEV-infected samples. Raw data from all the studies were re-analyzed to identify host factors associated with JEV replication.

RESULTS

We identified several coding and non-coding host factors that had no prior known role in viral infections. Of these, the coding transcripts: Myosin Heavy Chain 10 (MYH10), Progestin and AdipoQ Receptor Family Member 8 (PAQR8), and the microRNAs: hsa-miR-193b-5p, hsa-miR-3714 and hsa-miR-513a-5p were found to be novel host factors deregulated during JEV infection. MYH10 encodes a conventional non-muscle myosin, and mutations in MYH10 have been shown to cause neurological defects. PAQR8 has been associated with epilepsy, which exhibits symptoms similar to JEV infection. JE is a neuro-degenerative disease, and the known involvement of MYH10 and PAQR8 in neurological disorders strongly indicates potential roles of these host factors in JEV infection. Additionally, we observed that MYH10 and PAQR8 had a significant negative correlation with Activating transcription factor 3 (ATF3), which is a previously validated modulator of JEV infection. ATF3 is a transcription factor that binds to the promotors of genes encoding other transcription factors or interferon-stimulated genes and negatively regulates host antiviral responses during JE.

CONCLUSION

Our findings demonstrate the significance of data reanalysis in the identification of novel host factors that may become targets for diagnosis/ therapy against viral diseases of major concern, such as, JE. The deregulated coding and non-coding transcripts identified in this study need further experimental analysis for validation.

CircRNA.0007127 triggers apoptosis through the miR-513a-5p/CASP8 axis in K-562 cells

BACKGROUND: Circular RNAs (circRNAs) are covalently closed single-stranded RNAs with multiple biological functions. CircRNA.0007127 is derived from the carbon catabolite repression 4-negative on TATA-less (CCR4-NOT) complex subunit 2 (CNOT2), which was found to regulate tumor cell apoptosis through caspase pathway. METHODS: Potential circRNA.0007127 target microRNAs (miRNAs) were analyzed by miRanda, TargetScan, and RNAhybrid software, and the miRNAs with binding sites for apoptosis-related genes were screened. The roles of circRNA.0007127 and its downstream target, microRNA (miR)‍-513a-5p, were validated by quantitative real-time polymerase chain reaction (qPCR), flow cytometry, mitochondrial membrane potential, immunofluorescence, western blot, and caspase-8 (CASP8) protein activity in vitro in H₂O₂-induced K-562 cells. The circRNA.‍0007127‍‒‍miR-513a-5p and CASP8‍‒‍miR-513a-5p interactions were verified by luciferase reporter assays. RESULTS: Silencing circRNA.0007127 decreased cell apoptosis by inhibiting CASP8 pathway activation in K-562 cells. Compared with the control group, the expression of CASP8 was reduced by 50% and the 43-kD fragment of CASP8 protein was significantly reduced (P≤0.05). The luciferase reporting assay showed that circRNA.0007127 combined with miR-513a-5p or CASP8, with extremely significant differences (P≤0.001). The overexpression of miR-513a-5p inhibited the gene expression level of CASP8 in a human myeloid leukemia cell model (75% change) and the level of a 43-kD fragment of CASP8 protein (P≤0.01). The rescue experiment showed that cotransfection with circRNA.0007127 small-interfering RNA (siRNA) and the miR-513a-5p inhibitor increased CASP8 gene expression and the apoptosis rate, suggesting that the miR-513a-5p inhibitor is a circRNA.0007127 siRNA antagonist. CONCLUSIONS: CircRNA.0007127 regulates K-562 cell apoptosis through the miR-513a-5p/CASP8 axis, which can serve as a novel powerful molecular target for K-562 cells.

Identification of 5 microRNA biomarkers associated with the prognosis of uveal melanoma

To uncover the role of microRNAs in the occurrence and development of uveal melanoma (UM), we used R language packages in this study to analyze the correlations between the expression of microRNA isoforms, their target genes, and the clinical data for UM patients retrieved from The Cancer Genome Atlas (TCGA). We used Weighted Correlation Network Analysis (WGCNA) to divide the expression profiles of different microRNAs into 10 modules, among which blue and yellow modules were associated with UM survival. Hsa-miR-513a-5p, miR-506-3p, miR-508-3p, miR-140-3p, and miR-103a-2-5p were further identified as the top 5 node microRNAs based on the risk scores in both modules using least absolute shrinkage and selection operator (LASSO) Cox regression analysis. After combining these 5 microRNAs into an integrated risk signature, the prognostic performance of the risk signature was evaluated by area under the receiver operating characteristic (AUROC) curve, and their association with UM clinical characteristics was further analyzed using multiple Cox regression. Our results showed that this risk signature was sensitivity and specificity, and could serve as an independent prognostic factor. In addition, Spearman correlation analysis showed that expression of almost all target mRNAs were significantly positively or negatively correlated with the associated microRNAs. The gene ontology (GO), pathways, and disease enrichment analyses also showed that these 5 microRNAs were closely related to the incidence and progression of tumor, indicating their potential for predicting the outcome of UM.

High dose androgen suppresses natural killer cytotoxicity of castration-resistant prostate cancer cells via altering AR/circFKBP5/miRNA-513a-5p/PD-L1 signals

Most advanced prostate cancer (PCa) patients initially respond well to androgen deprivation therapy, but almost all eventually develop castration-resistant prostate cancer (CRPC). Early studies indicated the bipolar androgen therapy via a cycling of high dose and low dose of androgen to suppress PCa growth might be effective in a select patient population. The detailed mechanisms, however, remain unclear. Here we found the capacity of natural killer (NK) cells to suppress the CRPC cells could be suppressed by a high dose of dihydrotestosterone (DHT). Mechanism dissection indicates that transactivated AR can increase circularRNA-FKBP5 (circFKBP5) expression, which could sponge/inhibit miR-513a-5p that suppresses the PD-L1 expression via direct binding to its 3'UTR to negatively impact immune surveillance from NK cells. Preclinical data from in vitro cell lines and an in vivo mouse model indicate that targeting PD-L1 with sh-RNA or anti-PD-L1 antibody can enhance the high dose DHT effect to better suppress CRPC cell growth. These findings may help us to develop novel therapies via combination of high dose androgen with PD-1/PD-L1 checkpoint inhibitors to better suppress CRPC progression.

Hsa-miR-557 Inhibits Osteosarcoma Growth Through Targeting KRAS

Objective: Osteosarcoma is the most common malignancy in the skeletal system; studies showed an important role of miRNAs in tumorigenesis, indicating miRNAs as possible therapeutic molecules. This study found abnormal hsa-miR-557 expression levels in osteosarcoma and tried to explore the potential function and the mechanism.

Methods: Differential expression genes of osteosarcoma were analyzed using GSE28423 from the GEO database. Survival analysis of miRNAs was conducted with data obtained from the TARGET-OS database. STRING and miRDIP were used to predict target genes of hsa-miR-557; KRAS was then verified using dual-luciferase reporter assay. Expression of genes was detected by qPCR, and levels of proteins were detected by Western blot. The proliferation ability of cells was detected by CCK-8 and cell cycle analysis. Tumor formation assay in nude mice was used to detect the influence of osteosarcoma by hsa-miR-557 in vivo.

Results: Analysis from the GEO and TARGET databases found 12 miRNAs that are significantly related to the osteosarcoma prognosis, 7 downregulated (hsa-miR-140-3p, hsa-miR-564, hsa-miR-765, hsa-miR-1224-5p, hsa-miR-95, hsa-miR-940, and hsa-miR-557) and 5 upregulated (hsa-miR-362-3p, hsa-miR-149, hsa-miR-96, hsa-miR-744, and hsa-miR-769-5p). CCK-8 analysis and cell cycle analysis found that hsa-miR-557 could significantly inhibit the proliferation of osteosarcoma cells. The tumor formation assay in nude mice showed that tumor sizes and weights were inhibited by hsa-miR-557 transfection. Further studies also proved that hsa-miR-557 could target the 3′UTR of KRAS and modulate phosphorylation of downstream proteins.

Conclusion: This study showed that hsa-miR-557 could inhibit osteosarcoma growth both in vivo and in vitro, by modulating KRAS expression.

Long non-coding RNA titin-antisense RNA1 contributes to growth and metastasis of cholangiocarcinoma by suppressing microRNA-513a-5p to upregulate stratifin

Cholangiocarcinoma (CCA) is one of the most common histological types of primary hepatic malignancy and is associated with poor overall prognosis, causing a ponderous burden on human life. Hence, it is necessary to elucidate the pathogenesis of CCA. The objective of our research was to shed light on the mechanism through which long non-coding RNA titin-antisense RNA1 (lncRNA TTN-AS1) is involved in the development of CCA. Reverse transcription quantitative polymerase chain reaction was used to detect TTN-AS1 expression in CCA samples and cells. Functional experiments were performed using the Cell Counting Kit-8, 5-ethynyl-2'-deoxyuridine, transwell, and in vivo tumor growth assays. The relationship between TTN-AS1, miR-513a-5p, and stratifin (SFN) was explored using a dual luciferase reporter assay, RNA immunoprecipitation (RIP) experiment, and Pearson correlation analysis. The result showed that TTN-AS1 and SFN are highly expressed in CCA tissues. Bioinformatics analysis, luciferase reporter and RIP experiments revealed the correlation between TTN-AS1, miR-513a-5p, and SFN. In addition, silencing TTN-AS1 mitigated CCA cell proliferation and migration. Mechanistically, miR-513a-5p is sponged by TTN-AS1. The miR-513a-5p inhibitor abolished the effect of TTN-AS1 silencing on the aggressive behaviors of CCA cells. Furthermore, we showed that miR-513a-5p is a regulator of CCA by targeting SFN. TTN-AS1 induced CCA cell growth and metastasis via the miR-513a-5p/SFN pathway, which offers a new strategy for therapeutic interventions for CCA.

Effect of miRNA-200a on radiosensitivity of osteosarcoma cells by targeting Bone morphogenetic protein receptor 2

To study the effect of miR-200a on radiosensitivity of osteosarcoma cells and its mechanism. NC (normal cell) group, mimic-NC group, mimic-miR-200a group, inhibitor-NC group, inhibitor-miR-200a group, si-NC group, si-BMPR2 (Bone morphogenetic protein receptor 2) group, mimic-miR-200a+vector-NC group, and mimic-miR-200a+vector-BMPR2 group were set; the cells of the above groups were irradiated with different radiation intensities (0, 1, 2, 3, and 4 Gy). The expression of miR-200a and BMPR2 mRNA was detected by qRT-PCR; the expression of BMPR2 protein was detected by Western blot; cell viability was detected by MMT (3-(4,5)-dimethylthiahiazo (-z-y1)-3,5-di-phenytetrazoliumromide); apoptosis rate was detected by flow cytometry. Cell clone formation experiment was used to detect cell radiosensitivity. Dual-luciferase reporter gene test was used to detect cell fluorescence activity. The expression of BMPR2 was high and the expression of miR-200a was low in osteosarcoma tissues after radiotherapy and in osteosarcoma cells after irradiation. Overexpression of miR-200a and interference with BMPR2 expression inhibits osteosarcoma cell proliferation, promotes apoptosis, and increases cellular radiosensitivity, miR-200a targets expression of BMPR2, and overexpression of BMPR2 reverses the radiosensitizing and apoptotic effects of miR-200a expression on osteosarcoma cells. Overexpression of miR-200a inhibits osteosarcoma cell proliferation, promotes apoptosis, and increases cellular radiosensitivity. The mechanism may be related to the regulation of BMPR2, which may provide new targets and new ideas for osteosarcoma treatment.

DNA damage response and repair in osteosarcoma: Defects, regulation and therapeutic implications

Osteosarcoma (OS) is the most common primary bone malignancy in children and adolescents which has the survival rate of 20% in its advanced stages. Osteosarcomas are mostly resistance to our common treatments. DNA damage response (DDR) is a specialized multistep process containing abundant proteins which are necessary for the survival of any cell and organism. DDR machinery detects a diversity of DNA lesions and inhibits the cell cycle progression if these lesions are not repairable. DDR is involved in aging, age-related diseases, and cancer. In recent years, DDR inhibitors have gained the attention of researches due to their potentials in offering novel therapeutic targets and improving the response of many cancers to either chemo- or radio-therapy. In this regard, we tried to gather a great body of evidence about the role of DDR ingredients in osteosarcoma's initiation/progression, prognosis, and treatment.

Circ_0004872 promotes platelet-derived growth factor-BB-induced proliferation, migration and dedifferentiation in HA-VSMCs via miR-513a-5p/TXNIP axis

The proliferation, migration and dedifferentiation of vascular smooth muscle cells (VSMCs) exert crucial roles in atherosclerosis (AS) progression. The aim of our study was to explore the influences of circular RNA 0004872 (circ_0004872) in platelet-derived growth factor-BB (PDGF-BB)-induced AS cell model and investigate the underlying mechanisms. Real-time quantitative polymerase chain reaction (RT-qPCR) was implemented for the expression detection of circ_0004872, mitogen-activated protein kinase 1 (MAPK1) messenger RNA (mRNA), microRNA-513a-5p (miR-513a-5p) and thioredoxin interacting protein (TXNIP). Cell proliferation was analyzed via Cell Counting Kit 8 (CCK8) assay. Cell migration was assessed via wound healing assay and transwell migration assay. Western blot assay was used to measure the expression of alpha smooth muscle actin (α-SMA), osteopontin (OPN), calponin and TXNIP. Dual-luciferase reporter assay and RNA-pull down assay were used for confirmation of interaction between miR-513a-5p and circ_0004872 or TXNIP. Circ_0004872 expression was elevated in PDGF-BB-induced human aortic vascular smooth muscle cells (HA-VSMCs) and carotid plaque tissues. Circ_0004872 silencing alleviated PDGF-BB-induced proliferation, migration and dedifferentiation in HA-VSMCs. MiR-513a-5p bound to circ_0004872, and circ_0004872 knockdown-induced effects in PDGF-BB-treated HA-VSMCs were largely attenuated by the silencing of miR-513a-5p. MiR-513a-5p bound to the 3' untranslated region (3'UTR) of TXNIP, and miR-513a-5p overexpression-mediated effects were counteracted by the transfection of pcDNA-TXNIP in PDGF-BB-induced HA-VSMCs. TXNIP was modulated by circ_0004872/miR-513a-5p signaling cascade in HA-VSMCs. Circ_0004872 accelerated PDGF-BB-induced proliferation, migration and dedifferentiation in HA-VSMCs through enhancing TXNIP level via sponging miR-513a-5p.

Mechanisms of Resistance to Conventional Therapies for Osteosarcoma

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

New perspectives in cancer biology from a study of canonical and non-canonical functions of base excision repair proteins with a focus on early steps

Alterations of DNA repair enzymes and consequential triggering of aberrant DNA damage response (DDR) pathways are thought to play a pivotal role in genomic instabilities associated with cancer development, and are further thought to be important predictive biomarkers for therapy using the synthetic lethality paradigm. However, novel unpredicted perspectives are emerging from the identification of several non-canonical roles of DNA repair enzymes, particularly in gene expression regulation, by different molecular mechanisms, such as (i) non-coding RNA regulation of tumour suppressors, (ii) epigenetic and transcriptional regulation of genes involved in genotoxic responses and (iii) paracrine effects of secreted DNA repair enzymes triggering the cell senescence phenotype. The base excision repair (BER) pathway, canonically involved in the repair of non-distorting DNA lesions generated by oxidative stress, ionising radiation, alkylation damage and spontaneous or enzymatic deamination of nucleotide bases, represents a paradigm for the multifaceted roles of complex DDR in human cells. This review will focus on what is known about the canonical and non-canonical functions of BER enzymes related to cancer development, highlighting novel opportunities to understand the biology of cancer and representing future perspectives for designing new anticancer strategies. We will specifically focus on APE1 as an example of a pleiotropic and multifunctional BER protein.

Recent Insights into Therapy Resistance in Osteosarcoma

Osteosarcoma, the most common bone malignancy of childhood, has been a challenge to treat and cure. Standard chemotherapy regimens work well for many patients, but there remain minimal options for patients with progressive or resistant disease, as clinical trials over recent decades have failed to significantly improve survival. A better understanding of therapy resistance is necessary to improve current treatments and design new strategies for future treatment options. In this review, we discuss known mechanisms and recent scientific advancements regarding osteosarcoma and its patterns of resistance against chemotherapy, radiation, and other newly-introduced therapeutics.

LINC01436 Promotes the Progression of Gastric Cancer via Regulating miR-513a-5p/APE1 Axis

Background

Gastric cancer (GC) is one of the deadliest cancer worldwide. Multiple long non-coding RNAs (lncRNAs) are recently identified as crucial oncogenic factors or tumor suppressors in GC. In this study, we aimed to probe into the effect of LINC01436 on GC progression.

Methods

LINC01436 and miR-513a-5p expressions in GC tissue samples were measured using quantitative real-time polymerase chain reaction (qRT-PCR). Western blot was used to detect the expression of apurinic/apyrimidinic endodeoxyribonuclease 1 (APE1) expression. Human GC cell lines AGS and BGC-823 were employed to investigate the function and mechanism of LINC01436 in GC. Cell counting kit-8 (CCK-8) assay was used to assess the effect of LINC01436 on proliferation. Flow cytometry was utilized to explore the effect of LINC01436 on apoptosis, and Transwell assay was conducted to detect the effect of LINC01436 on the migration and invasion. Colony formation assay was performed to evaluate the effect of LINC01436 on radioresistance of GC cells. Furthermore, luciferase reporter assay and RNA immunoprecipitation assay were conducted to confirm the binding relationship between miR-513a-5p and LINC01436. Additionally, Western blot was used to study the regulatory function of LINC01436 and miR-513a-5p on APE1.

Results

LINC01436 expression of GC clinical samples was remarkably increased and LINC01436 was correlated with unfavorable pathological indexes. LINC01436 high expression was associated with shorter overall survival time. Its overexpression observably promoted the proliferation, metastasis and radioresistance of GC cells, and its knockdown suppressed the malignant phenotypes of GC cells. LINC01436 overexpression markedly reduced the miR-513a-5p expression via sponging it and enhanced the APE1 expression. MiR-513a-5p overexpression or APE1 knockdown reversed the effects of LINC01436 on GC cells.

Conclusion

LINC01436 is a molecular sponge of tumor suppressor miR-513a-5p, which indirectly enhances the APE1 expression and functions as the oncogenic lncRNA in GC.

Targeting Molecular Mechanisms Underlying Treatment Efficacy and Resistance in Osteosarcoma: A Review of Current and Future Strategies

Osteosarcoma is the most common primary malignant bone tumour in children and adolescents. Due to micrometastatic spread, radical surgery alone rarely results in cure. Introduction of combination chemotherapy in the 1970s, however, dramatically increased overall survival rates from 20% to approximately 70%. Unfortunately, large clinical trials aiming to intensify treatment in the past decades have failed to achieve higher cure rates. In this review, we revisit how the heterogenous nature of osteosarcoma as well as acquired and intrinsic resistance to chemotherapy can account for stagnation in therapy improvement. We summarise current osteosarcoma treatment strategies focusing on molecular determinants of treatment susceptibility and resistance. Understanding therapy susceptibility and resistance provides a basis for rational therapy betterment for both identifying patients that might be cured with less toxic interventions and targeting resistance mechanisms to sensitise resistant osteosarcoma to conventional therapies.

Circular RNA MYLK promotes tumour growth and metastasis via modulating miR-513a-5p/VEGFC signalling in renal cell carcinoma

Growing evidence indicates that circular RNAs (circRNAs) are promising biomarkers, as they play significant roles in the development of various cancers. The circular RNA MYLK (circMYLK) has been reported to be involved in the development of malignant tumours, including liver, prostate and bladder cancers. Nevertheless, the biological function of circMYLK in renal cell carcinoma (RCC) remains unclear. In this study, we observed that circMYLK is notably up-regulated in RCC. Increased circMYLK expression led to a larger tumour size, distant metastasis and poor prognosis of RCC patients. Moreover, circMYLK silencing repressed RCC growth and metastasis in vitro and in vivo. Mechanistically, circMYLK can capture miR-513a-5p to facilitate VEGFC expression and further promote the tumorigenesis of RCC cells. In summary, our findings demonstrate that circMYLK has an oncogenic role in RCC growth and metastasis by modulating miR-513a-5p/VEGFC signalling. Thus, circMYLK has potential as a diagnostic biomarker and therapeutic target in the treatment of RCC.

The multiple function of long noncoding RNAs in osteosarcoma progression, drug resistance and prognosis

Osteosarcoma is a bone tumor prevalent in children and young adults. LncRNAs are a family of non-protein-coding transcripts longer than 200 nucleotides. The tumor-related pathological functions of lncRNAs include proliferation, migration, and chemotherapy resistance, all of which have been widely acknowledged in research on osteosarcoma. In addition, compelling evidence suggests that lncRNAs could serve as diagnostic indicators, prognostic biomarkers, and targets for disease treatment. In this review, we systematically summarize how lncRNAs regulate tumorigenesis, invasion and therapeutic resistance. By deepening our knowledge of the relationship between lncRNAs and osteosarcoma, we hope to translate research findings into clinical applications as soon as possible.

miRNA signatures in childhood sarcomas and their clinical implications

Progresses in multimodal treatments have significantly improved the outcomes for childhood cancer. Nonetheless, for about one-third of patients with Ewing sarcoma, rhabdomyosarcoma, or osteosarcoma steady remission has remained intangible. Thus, new biomarkers to improve early diagnosis and the development of precision-targeted medicine remain imperative. Over the last decade, remarkable progress has been made in the basic understanding of miRNAs function and in interpreting the contribution of their dysregulation to cancer development and progression. On this basis, this review focuses on what has been learned about the pivotal roles of miRNAs in the regulation of key genes implicated in childhood sarcomas.

lncRNA UCA1 Increases Proliferation and Multidrug Resistance of Retinoblastoma Cells Through Downregulating miR-513a-5p

Chemoresistance is one of the major obstacles for cancer therapy. Abnormal expression of long noncoding RNAs (lncRNAs) was broadly implicated in chemoresistance of multiple cancers. This study was aimed to investigate the function of urothelial cancer associated 1 (UCA1) in multidrug resistance of retinoblastoma and its potential molecular mechanism. In this study, we observed that UCA1 was significantly upregulated in chemoresistant retinoblastoma tissues and multidrug resistant retinoblastoma cell lines and predicted an unfavorable overall survival. Functionally, knockdown of UCA1 remarkably inhibited proliferation and sensitized retinoblastoma cells to multiple chemotherapy drugs, including vincristine (VCR), carboplatin (CBP), cisplatin (DDP), VP-16 (etoposide), and 5-fluorouracil (5-Fu). Mechanistic studies demonstrated that UCA1 functioned as a miRNA sponge to increase stathmin 1 (STMN1) expression through sponging miR-513a-5p. In addition, silence of miR-513a-5p or STMN1 overexpression could partly reverse UCA1 knockdown-induced inhibitory effects on proliferation and multidrug resistance of retinoblastoma cells. Overall, this study is the first to demonstrate that UCA1 plays a critical role in retinoblastoma chemoresistance, and UCA1 may serve as a potential diagnostic biomarker and therapeutic target of retinoblastoma.

The Role of miRNA in the Diagnosis, Prognosis, and Treatment of Osteosarcoma

Osteosarcoma (OS) is one of the most common malignant tumors derived from mesenchymal tissue and is highly invasive, mainly in children and adolescents. Treatment of OS is mostly based on standard treatment options, including aggressive surgical resection, systemic chemotherapy, and targeted radiation therapy, but the 5-year survival rate is still low. MicroRNA (miRNA) is a highly conserved type of endogenous nonprotein-encoding RNA, about 19-25 nucleotides in length, whose transcription process is independent of other genes. Generally, miRNAs play a role in regulating cell proliferation, differentiation, apoptosis, and development by binding to the 3' untranslated region of target mRNAs, whereby they can degrade or induce translational silencing. Although miRNAs play a regulatory role in various metabolic processes, they are not translated into proteins. Several studies have shown that miRNAs play an important role in the diagnosis, treatment, and prognosis of OS. Herein, the authors describe new advances in the diagnosis, prognosis, and treatment of miRNAs in OS.

MicroRNA-638 expression change in osteosarcoma patients via PLD1 and VEGF expression

The present study aimed to investigate the function and mechanism of microRNA-638 (miR-638) in osteosarcoma. MiR-638 expression change in patients with osteosarcoma was detected by reverse transcription-quantitative polymerase chain reaction. Expression of miR-638 was observed to be downregulated in patients with osteosarcoma compared with the control group. In vitro, overexpression of miR-638 induced apoptosis, and inhibited cell proliferation and invasion of osteosarcoma cells. Overexpression of miR-638 induced Bcl-2 associated X and caspase-3 protein expression, and suppressed cyclin D1, phospholipase D1 (PLD1) and vascular endothelial growth factor (VEGF) protein expression in osteosarcoma. The promotion of PLD1 decreased the effects of miR-638 on osteosarcoma cell proliferation. In summary, it was demonstrated that miRNA-638 expression change in patients with osteosarcoma and an in vitro model via PLD1 and VEGF expression and miRNA-638 may be potential clinical indicators of osteosarcoma.

Identification of co-expression modules and pathways correlated with osteosarcoma and its metastasis

BACKGROUND

Osteosarcoma is the most common bone tumor that occurs in children.

METHODS

To identify co-expression modules and pathways correlated with osteosarcoma and its clinical characteristics, we performed weighted gene co-expression network analysis (WGCNA) on RNA-seq data of osteosarcoma with 52 samples. Then we performed pathway enrichment analysis on genes from significant modules.

RESULTS

A total of 5471 genes were included in WGCNA, and 16 modules were identified. Module-trait analysis identified that a module involved in microtubule bundle formation, drug metabolism-cytochrome P450, and IL-17 signaling pathway was negatively correlated with osteosarcoma and positively correlated with metastasis; a module involved in DNA replication was positively correlated with osteosarcoma; a module involved in cell junction was positively correlated with metastasis; and a module involved in heparin binding negatively correlated with osteosarcoma. Moreover, expression levels in four of the top ten differentially expressed genes were validated in another independent dataset.

CONCLUSIONS

Our analysis might provide insight for molecular mechanisms of osteosarcoma.

Activation of Sonic Hedgehog Signaling Is Associated with Human Osteosarcoma Cells Radioresistance Characterized by Increased Proliferation, Migration, and Invasion

Background

Radioresistance restricts the application of radiotherapy in human osteosarcoma (OS). This study investigated the molecular mechanism of radioresistance in OS, which may provide clues to finding ideal targets for genetic therapy.

Materila/Methods

The human OS cell line MG63 was employed as parent cells. After repeat low-dose X-ray irradiation of MG63, the radioresistant OS cell line MG63R was produced. Colony formation assay was used to assess the radioresistance. Cell viability was evaluated by CCK-8 assay. Flow cytometry was used to detect cell apoptosis, and wound healing assay was used to evaluate invasive capacity. The nuclear translocation was evaluated by fluorescent immunohistochemistry. Protein expression levels were assessed by Western blotting. Specific siRNA against Shh was used to silence Shh.

Results

More survival colony formation, elevated cell viability, less cell apoptosis, and increased wound closure were found in MG63R than in MG63 cells exposed to irradiation. The nuclear translocation of Gli, expression levels of Shh, Smo, Ptch1, Bcl2, active MMP2, and active MMP9 were increased in MG63R cells compared with MG63 cells. Transfection of Shh-siRNA suppressed expression levels of Shh, Smo, Ptch1, Bcl2, active MMP2, and active MMP9, as well as the nuclear translocation of Gli in MG63R cells. The cell viability, survival colony formation, and wound closure were impaired, whereas cell apoptosis was increased, in siRNA-transfected MG63R cells than in control MG63R cells exposed to irradiation.

Conclusions

Activation of Shh signaling was involved in radioresistance of OS cells. Blocking this signaling can impair the radioresistance capacity of OS cells.

NOVA1 acts as an oncogene in osteosarcoma

Osteosarcoma is one of the most common bone tumors in young patients. NOVA1 (neuro-oncological ventral antigen 1) is a neuron-specific RNA binding-protein and belongs to the Nova family. Previous studies showed that NOVA1 played crucial roles in the development of several tumors. The objective of our study was to study the role of NOVA1 in the osteosarcoma. In our study, we showed that NOVA1 expression was upregulated in osteosarcoma cell lines and tissues. The expression of NOVA1 was upregulated in 22 (22/30; 73%) osteosarcoma cases compared to that in the adjacent tissues. Overexpression of NOVA1 promoted osteosarcoma cell viability, colony formation and invasion. Furthermore, knockdown of NOVA1 suppressed osteosarcoma cell viability, colony formation and invasion. These data suggested that NOVA1 acted as an oncogene in the development of osteosarcoma.

What Is New in the miRNA World Regarding Osteosarcoma and Chondrosarcoma?

Despite the availability of multimodal and aggressive therapies, currently patients with skeletal sarcomas, including osteosarcoma and chondrosarcoma, often have a poor prognosis. In recent decades, advances in sequencing technology have revealed the presence of RNAs without coding potential known as non-coding RNAs (ncRNAs), which provides evidence that protein-coding genes account for only a small percentage of the entire genome. This has suggested the influence of ncRNAs during development, apoptosis and cell proliferation. The discovery of microRNAs (miRNAs) in 1993 underscored the importance of these molecules in pathological diseases such as cancer. Increasing interest in this field has allowed researchers to study the role of miRNAs in cancer progression. Regarding skeletal sarcomas, the research surrounding which miRNAs are involved in the tumourigenesis of osteosarcoma and chondrosarcoma has rapidly gained traction, including the identification of which miRNAs act as tumour suppressors and which act as oncogenes. In this review, we will summarize what is new regarding the roles of miRNAs in chondrosarcoma as well as the latest discoveries of identified miRNAs in osteosarcoma.