MiR-367 negatively regulates apoptosis induced by adriamycin in osteosarcoma cells by targeting KLF4

The promising roles of exosomal microRNAs in osteosarcoma: A new insight into the clinical therapy

Osteosarcoma is the most common malignant bone sarcoma in children. Chemotherapy drugs resistance significantly hinders the overall survival of patients. Due to high biocompatibility and immunocompatibility, exosomes have been explored extensively. Multiple parent cells can actively secrete numerous exosomes, and the membrane structure of exosomes can protect miRNAs from degradation. Based on these characteristics, exosomal miRNAs play an important role in the occurrence, development, drug resistance. Therefore, in-depth exploration of exosome biogenesis and role of exosomal miRNAs will provide new strategies and targets for understanding the pathogenesis of osteosarcoma and overcoming chemotherapy drug resistance. Moreover, advancing evidences have showed that engineering modification could attribute stronger targeting to exosomes to deliver cargos to recipient cells more effectively. In this review, we focus on the mechanisms of exosomal miRNAs on the occurrence and development of osteosarcoma and the potential to function as tumor biomarkers for diagnosis and prognosis prediction. In addition, we also summarize recent advances in the clinical application values of engineering exosomes to provide novel ideas and directions for overcoming the chemotherapy resistance in osteosarcoma.

Expression analysis of circulating miR-22, miR-122, miR-217 and miR-367 as promising biomarkers of acute lymphoblastic leukemia

BACKGROUND

The role of serum-based biomarkers such as microRNAs in cancer diagnosis has been extensively established. This study aimed to determine the expression levels of bioinformatically selected miRNAs and whether they can be used as biomarkers or a new therapeutic target in patients with acute lymphoblastic leukemia (ALL).

MATERIALS AND METHODS

The expression levels of serum miR-22, miR-122, miR-217, and miR-367 in 21 ALL patients and 21 healthy controls were measured using quantitative real-time PCR. The receiver operating characteristic (ROC) curve and the associated area under the curve (AUC) was used to assess candidate miRNAs' diagnostic value as a biomarker.

RESULTS

The results showed that miR-217 was markedly decreased in patients with ALL compared to controls. Moreover, miR-22, miR-122, and miR-367 were found to be upregulated. Furthermore, ROC analysis showed that serum miR-217 and miR-367 could differentiate ALL patients from healthy individuals, while miR-22 has approximate discriminatory power that requires further investigation.

CONCLUSION

These results provide promising preliminary evidence that circulating miR-217 and miR-367 could be considered potent diagnostic biomarkers and therapeutic goals in this disease.

Effects of microenvironment in osteosarcoma on chemoresistance and the promise of immunotherapy as an osteosarcoma therapeutic modality

Osteosarcoma (OS) is one of the most common primary malignant tumors originating in bones. Its high malignancy typically manifests in lung metastasis leading to high mortality. Although remarkable advances in surgical resection and neoadjuvant chemotherapy have lengthened life expectancy and greatly improved the survival rate among OS patients, no further breakthroughs have been achieved. It is challenging to treat patients with chemoresistant tumors and distant metastases. Recent studies have identified a compelling set of links between hypoxia and chemotherapy failure. Here, we review the evidence supporting the positive effects of hypoxia in the tumor microenvironment (TME). In addition, certain anticancer effects of immune checkpoint inhibitors have been demonstrated in OS preclinical models. Continued long-term observation in clinical trials is required. In the present review, we discuss the mutualistic effects of the TME in OS treatment and summarize the mechanisms of immunotherapy and their interaction with TME when used to treat OS. We also suggest that immunotherapy, a new comprehensive and potential antitumor approach that stimulates an immune response to eliminate tumor cells, may represent an innovative approach for the development of a novel treatment regimen for OS patients.

MicroRNA-367-3p suppresses sevoflurane-induced adult rat astrocyte apoptosis by targeting BCL2L11

The present study aimed to characterize the effect of microRNA (miR)-367-3p on sevoflurane anesthesia and elucidate the underlying mechanism. A total of 36 4-month-old adult Sprague-Dawley rats were divided into six groups. Sevoflurane was inhaled at concentrations of 0, 1, 2, 4, 8 and 16% for a total of 6 h; the hippocampus of the brain was subsequently minced and digested, and astrocytes were isolated. Various methods, including reverse transcription-quantitative (RT-q)PCR, western blotting and TUNEL staining, were used to determine the expression levels of Bax, BCL-2 and BCL-2-like protein 11 (BCL2L11), as well as the level of apoptosis. The rats were treated with 8% sevoflurane and the astrocytes from the rats were transfected with miR-367-3p or anti-miR-367-3p. The present study demonstrated that sevoflurane promoted astrocytes apoptosis. Western blotting revealed that with an increase of sevoflurane concentration, the expression levels of the apoptotic proteins Bax and BCL2L11 were significantly increased, whereas the protein expression levels of BCL-2 were significantly decreased. However, overexpression of miR-367-3p reversed these effects. TUNEL staining revealed that sevoflurane promoted the apoptosis of astrocytes, while apoptosis was reversed by miR-367-3p overexpression. RT-qPCR demonstrated that sevoflurane inhibited the expression of miR-367-3p. Notably, miR-367-3p reduced the expression of BCL2L11, thereby inhibiting the apoptosis of astrocytes originating from the hippocampal area of adult rats induced by sevoflurane. Therefore, miR-367-3p and BCL2L11 may act as effective targets for the study of anesthesia.

MicroRNA (miR)-429 Promotes Inflammatory Injury by Targeting Kruppel-like Factor 4 (KLF4) in Neonatal Pneumonia

BACKGROUND

Neonatal pneumonia is a common disease in the neonatal period with a high incidence and death. This study aimed to investigate the molecular mechanism and effect of microRNA (miR)-429 in neonatal pneumonia.

METHODS

The peripheral blood was collected from neonatal pneumonia and healthy patients, respectively. Human lung fibroblast WI-38 cells were treated with lipopolysaccharide (LPS) to establish neonatal pneumonia cell model. Then, the miR-429 expression was detected by quantitative real-time polymerase chain reaction (qRT-PCR). In addition, the relationship between miR- 429 and kruppel-like factor 4 (KLF4) was confirmed by dual luciferase reporter assay. Cell viability, the level of interleukin 6 (IL-6), IL-1β and tumor necrosis factor α (TNF-α) and apoptosis were measured by Cell Counting Kit-8 (CCK-8), enzyme linked immunosorbent assay (ELISA) and flow cytometry. Meanwhile, apoptosis and nuclear factor kappa-B (NF-κB) pathway related proteins expression were analyzed by western blot.

RESULTS

MiR-429 expression level was increased in neonatal peripheral blood and LPS-stimulated WI-38 cells. Then, miR-429 overexpression increased apoptosis, the level of IL-6, IL-1β, TNF-α, Bax and cleaved caspase-3, while reduced cell viability in LPS-stimulated WI-38 cells. Besides, KLF4 was identified as the target gene of miR-429, and reversed the changes caused by miR-429 overexpression. Finally, miR-429 suppressor down-regulated p-NF-κB level in LPS-stimulated cells and KLF4 knockdown reversed these reductions.

CONCLUSION

MiR-429 promotes inflammatory injury, apoptosis and activates the NF-κB signaling pathway by targeting KLF4 in neonatal pneumonia, and then these results provide evidence for clinical diagnosis and treatment for neonatal pneumonia.

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.

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.

MiR-409-3p Inhibits Cell Proliferation and Invasion of Osteosarcoma by Targeting Zinc-Finger E-Box-Binding Homeobox-1

Osteosarcoma (OS) is the most common bone cancer worldwide. There is evidence that microRNA-409 (miR-409-3p) is involved in tumorigenesis and cancer progression, however, its possible role in OS requires clarification. In the present study, we evaluated the expression level, clinical significance, and mode of action of miR-409-3p in OS. The miR-409-3p levels were diminished in the OS cells and tissues compared with associated adjacent non-tumor tissues and a non-cancer osteoplastic cell line. Low miR-409-3p expression levels were associated with clinical stage and distant metastasis in patients with OS. Resumption of miR-409-3p expression attenuated OS cell proliferation and invasion. Additionally, based on informatics analyses, we predicted that zinc-finger E-box-binding homeobox-1 (ZEB1) is a possible target of miR-409-3p. This hypothesis was confirmed using luciferase reporter assays, reverse transcription-quantitative real-time polymerase chain reaction, and Western blot analyses. The findings of the current study indicated that ZEB1 was up-regulated in the OS tissues and cell lines, and that this up-regulation was inversely proportional to miR-409-3p expression levels. Furthermore, down-regulation of ZEB1 decreased OS cell invasion and proliferation, illustrating that the tumor suppressive role of miR-409-3p in OS cells may be exerted via negative regulation of ZEB1. Taken together, our observations highlight the potential role of miR-409-3p as a tumor suppressor in OS partially through down-regulation of ZEB1 and suggest that miR-409-3p has potential applications in OS treatment.

Drug resistance-related microRNAs in osteosarcoma: Translating basic evidence into therapeutic strategies

Although the application of multiple chemotherapy brought revolutionary changes to improve overall survival of osteosarcoma patients, the existence of multidrug resistance (MDR) has become a great challenge for successful osteosarcoma treatment in recent decades. Substantial studies have revealed various underlying mechanisms of MDR in cancers. As for osteosarcoma, evidence has highlighted that microRNAs (miRNAs) can mediate in the processes of DNA damage response, apoptosis avoidance, autophagy induction, activation of cancer stem cells, and signal transduction. Besides, these drug resistance‐related miRNAs showed much promise for serving as candidates for predictive biomarkers of poor outcomes and shorter survival time, and therapeutic targets to reverse drug resistance and overcome treatment refractoriness. This review aims to demonstrate the potential molecular mechanisms of miRNAs‐regulated drug resistance in osteosarcoma, and provide insight in translating basic evidence into therapeutic strategies.

MicroRNA‑9‑5p downregulates Klf4 and influences the progression of hepatocellular carcinoma via the AKT signaling pathway

Krüppel-like factor 4 (Klf4) is a transcriptional factor involved in the progression of hepatocellular carcinoma (HCC). However, the underlying regulatory mechanisms associated with the Klf4 gene as a tumor suppressor in HCC remain unclear. microRNAs (miRNAs or miRs) are a series of small non-coding RNAs that serve a vital role in regulating gene expression via their influence on protein translation and the associated degradation of mRNA. The mRNA expression levels of the miRNA, miR-9-5p, and Klf4 were measured using reverse transcription-quantitative polymerase chain reaction. The protein expression levels of Klf4, protein kinase B (AKT), phosphorylated (p-)AKT, mechanistic target of rapamycin (mTOR), p-mTOR, B cell lymphoma-2 (Bcl-2) and Bcl-2-associated X protein (Bax) were determined by western blot analysis. Dual luciferase reporter assay was used to confirm a direct interaction between miR-9-5p and the 3′-untranslated region (3′-UTR) sequence of Klf4. Cell counting kit-8 assay, wound healing assay, Transwell migration assay and flow cytometric analysis were performed to evaluate the proliferative, migratory and apoptotic capabilities of the HCC cells. In the present study, miR-9-5p was revealed to be overexpressed in HCC as a novel upstream gene of Klf4. miR-9-5p expression was inversely associated with Klf4 expression in clinical samples. Additionally, Kaplan-Meier analysis revealed a markedly poor prognosis of HCC in the miR-9-5p high-expression group. Bioinformatics analysis revealed that miR-9-5p bound directly to the 3′-UTR of Klf4, which reduced the expression levels of Klf4. The miR-9-5p/Klf4 axis promoted HCC proliferation and migration, and inhibited HCC apoptosis. Furthermore, miR-9-5p upregulated the Bcl-2/Bax protein ratio and activated AKT/mTOR signaling. Taken together, these data demonstrated that the miR-9-5p/Klf4 axis was able to promote HCC progression, which may occur via regulation of the AKT signaling pathway, highlighting a potential novel target in HCC treatment.

Mechanism of the enhancing effects of miR-93 on resistance of breast cancer MCF-7 cells to adriamycin

This study aimed to investigate the effects of miR-93 on resistance of breast cancer MCF-7 cells to adriamycin, and to explore the possible mechanism. Expression of miR-93 in breast cancer cell lines MCF-7 and MCF-7/ADM was detected by reverse transcription-quantitative PCR (RT-qPCR). miR-93 mimics and inhibitors were transfected into MCF-7/ADM and MCF-7 cells, and MTT assay was used to detect the resistance of cells to adriamycin after transfection. Western blot analysis was used to detect the expression of anti-apoptotic protein Bcl-2 and multidrug resistance gene MDR1 related P-gp protein in MCF-7/ADM and MCF-7 cells before and after the transfection of miR-93 mimics. Expression level of miR-93 in MCF-7/ADM cells was decreased, and was 40% of that in MCF-7 cells (0.39±0.04, p<0.05). Before transfection, IC₅₀ value of MCF-7 cells to adriamycin (11.02±0.95) was lower than that of MCF-7/ADM cells (21.29±1.83, p<0.05). IC₅₀ value of MCF-7/ADR cells at 72 h after transfection with miR-93 mimics (13.55±0.86) was lower than that of the negative control group (24.67±1.51, p<0.05). IC₅₀ value of MCF-7 cells 72 h after transfection with miR-93 inhibitor (19.88±1.28) was higher than that of negative control group (11.02±0.95, p<0.05). Expression levels of Bcl-2 and P-gp proteins in MCF-7/ADM cells were 1.63±0.24 and 1.76±0.22 times that of MCF-7 cells, respectively (p<0.05). At 72 h after transfection of miR-93 mimics, expression levels of Bcl-2 and P-gp proteins in MCF-7/ADM cells were 0.27±0.06 and 0.39±0.05, respectively, compared with the negative control group (p<0.05). At 72 h after transfection with miR-93 inhibitor, expression levels of Bcl-2 and P-gp protein in MCF-7 cells were 1.48±0.10 and 1.56±0.11 times of the negative control group, respectively (p<0.05). miR-93 can increase the apoptosis of MCF-7/ADM cells and their resistance to adriamycin by inhibiting the expression of Bcl-2 and P-gp proteins.

miR-181b inhibits chemoresistance in cisplatin-resistant H446 small cell lung cancer cells by targeting Bcl-2

INTRODUCTION

MicroRNAs (miRNAs) are a group of small non-coding RNAs that affect multiple aspects of tumor biology including chemo resistance. miR-181b has been reported to modulate multidrug resistance in non-small cell lung cancer cells. This study was undertaken to determine the role of miR-181b in chemo resistance of small cell lung cancer cells.

MATERIAL AND METHODS

This study was undertaken to determine the role of miR-181b in chemoresistance of small cell lung cancer cells with use of qRt-PCR, WB, bioinformatics analysis, and double luciferase reporter system.

RESULTS

Our data showed that miR-181b was significantly downregulated in cisplatin-resistant H446 small cell lung cancer cells, compared to parental cells, compared to parental cells. Ectopic expression of miR-181b inhibited cell proliferation and invasion in cisplatin-resistant H446 cells (p = 0.023). Moreover, overexpression of miR-181b increased the susceptibility of cisplatin-resistant H446 cells to cisplatin. Mechanistic investigations demonstrated that miR-181b inhibited B-cell lymphoma-2 (Bcl-2) expression by binding to the 3'-untranslated region. Overexpression of Bcl-2 reversed miR-181b-mediated chemo sensitization, which is accompanied by a reduced apoptotic response.

CONCLUSIONS

Taken together, this work demonstrated that miR-181b might have the ability to overcome chemo resistance of small cell lung cancer cells, and restoration of this miRNA may represent a potential therapeutic strategy for improving chemo sensitivity in small cell lung cancer.

MicroRNA-346 regulates neural stem cell proliferation and differentiation by targeting KLF4

MicroRNAs have been shown to play an important role in stem cell fate determination and self-renewal. However, the role of miRNAs in neural stem cells (NSCs) remains poorly understood. In this study, we showed that miR-346, a less characterized microRNA, promoted NSCs proliferation, differentiation and apoptosis by targeting KLF4, a core transcriptional factor in stem cell fate determination. Our data suggested that miR-346 could directly target the 3'-untranslated region of KLF4. Overexpression of miR-346 decreased KLF4 expression at both mRNA and protein levels in NSCs. More importantly, Overexpression of miR-346 repressed NSC proliferation and induced the expression of lineage markers including GFAP and Tuj1. Additionally, overexpression of miR-346 promoted apoptosis of NSCs. In concert, suppressing its expression by an antisense RNA, anti-miR-346, promoted NSC proliferation, and meanwhile inhibited its differentiation and apoptosis. We also showed that the effects of miR-346 overexpression could be reversed by re-expression of KLF4. Taken together, Those data suggest that miR-346 is a novel miRNA that regulates NSC proliferation and differentiation by targeting KLF4.

RETRACTED: miR-367 regulation of DOC-2/DAB2 interactive protein promotes proliferation, migration and invasion of osteosarcoma cells

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the authors, who have informed the Editor-in-Chief that miR-367 overexpression did not significantly reduce the DAB2IP level in MG-63 cells as shown in Figures 4C and 4D of the published article. Furthermore, the effects of miR-367 overexpression and DAB2IP knockdown on the proliferation and metastasis of MG-63 cells in Figure 2 and Figure 6 are also no longer repeatable. Subsequent analysis showed that the MG-63 cells used in this study were contaminated with HeLa cells, identified by short tandem repeat analysis. The authors believe cell contamination may be the main reason why the reported results are not reproducible. The authors no longer have confidence in the reliability of the results and would like to apologize for any inconvenience caused. The Editor-in-Chief agreed to retract the article.

Potential therapeutic implications of miRNAs in osteosarcoma chemotherapy

Osteosarcoma is the most common primary bone cancer in young adults and adolescents. Drug resistance is the main cause leading to therapeutical failure. The mechanisms of drug resistance of osteosarcoma have not been fully understood. Notably, recent researches associate microRNA with drug resistance in osteosarcoma cells, raising the awareness that targeting microRNAs may help in chemotherapy success. In this review, we summarize the mechanisms linking microRNAs to drug resistance and ongoing researches on microRNAs in drug response to osteosarcoma. In addition, the therapeutic potential of microRNAs in chemotherapy will also be discussed.

miR-367 promotes tumor growth by inhibiting FBXW7 in NSCLC

miR-367 is one of the most abundant miRNAs in human embryonic stem cells (hESCs) and is mainly involved in maintaining the pluripotency of stem cells. However, its role in cancer development remains poorly understood. In the present study, we explored the function and mechanism of the endogenous miR-367 in non-small cell lung cancer (NSCLC). In the present study, we demonstrated that the level of miR-367 in NSCLC was significantly higher than that in adjacent normal tissues, and its upregulation was positively correlated with tumor size, tumor differentiation and tumor-node-metastasis (TNM) stage. miR-367 was an indicator of a poorer prognosis in NSCLC patients. Furthermore, overexpression of miR-367 significantly inhibited apoptosis and enhanced proliferation by promoting cell cycle transition from G1 to S phase. In contrast, knockdown of miR-367 markedly reversed the cellular events observed with miR-367 overexpression. Moreover, we identified that F-box and WD repeat domain-containing 7 (FBXW7) is a novel target of miR-367. It reverses the oncogenic effects of miR-367 by downregulating its substrates, c-Myc and c-Jun, in NSCLC cells. Finally, studies in vivo revealed that knockdown of miR-367 inhibited the growth of xenografts in the nude mice by increasing the expression of FBXW7. In summary, our findings indicate that miR-367 exerts tumor-promoting effect by negatively regulating FBXW7 in NSCLC, and it could become a potential therapeutic target for NSCLC intervention.

MicroRNA-433 regulates apoptosis by targeting PDCD4 in human osteosarcoma cells

Osteosarcoma is the most common aggressive sarcoma of the bone in children and adolescents. It is characterized by a high level of genetic instability and recurrent DNA deletions and amplifications. microRNAs (miRNAs) play a key role in cancer initiation, progression and metastasis; however, the potential role of miRNAs in osteosarcoma remains largely unknown. In the present study, miR-433 was shown to be overexpressed in osteosarcoma tissues compared with normal human osteoblasts. Transfection of miR-433 mimics into osteosarcoma cell lines significantly decreased apoptosis by targeting programmed cell death 4, a tumor suppressor that is involved in apoptosis. In contrast, inhibition of miR-433 enhanced apoptosis. Furthermore, in vivo miR-433 overexpression inhibited the apoptosis of tumor cells and increased tumor growth. The results of the present study suggested that miR-433 is a potential molecular target for osteosarcoma therapy.

miR-1297 regulates neural stem cell differentiation and viability through controlling Hes1 expression

OBJECTIVES

Neural stem cells (NSCs) are self-renewing, undifferentiated and multipotent precursors that can generate neuronal and glial lineages. MicroRNAs (miRNAs) are small non-coding RNAs that act crucial roles in cell proliferation, differentiation and migration. However, the role of miR-1297 in the development of NSCs is still unknown.

MATERIALS AND METHODS

Primary NSCs were isolated from rat's embryos. The expression of miR-1297 and Hes1 were measured by qRT-PCR. Western blot was performed to detect the protein expression of Hes1, β-tubulin-III and GFAP.

RESULTS

We showed that miR-1297 expression was upregulated during NSC differentiation, while the expression of Hes1 was decreased during NSC differentiation. Elevated expression of miR-1297 promoted the NSCs viability and increased the formation of NSCs to neurospheres. Ecoptic expression of miR-1297 promoted β-tubulin-III expression in the NSCs. Overexpression of miR-1297 decreased GFAP expression in the NSCs. Furthermore, we demonstrated that miR-1297 regulated NSCs viability and differentiation by directly targeting Hes1. Overexpression of miR-1297 suppressed Hes1 expression in the NSCs.

CONCLUSIONS

These results suggested that miR-1297 played an important role in NSCs viability and differentiation through inhibiting Hes1 expression.

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.

MicroRNA-21 Inhibits the Apoptosis of Osteosarcoma Cell Line SAOS-2 via Targeting Caspase 8

Currently, multiple microRNAs (miRNAs) have been found to play vital roles in the pathogenesis of osteosarcoma. This study aimed to investigate the role of miR-21 in osteosarcoma. The level of miR-21 in 20 pairs of osteosarcoma and corresponding adjacent tissues was monitored by qPCR. Human osteosarcoma cell line SAOS-2 was transfected with either miR-21 mimic or miR-21 inhibitor, and then cell viability, survival, and apoptosis were measured by MTT, colony formation assay, and flow cytometry. A target of miR-21 was predicted by the microRNA.org database and verified in vitro by using luciferase reporter, qPCR, and Western blot analyses. Finally, cells were cotransfected with siRNA against caspase 8 and miR-21 inhibitor, and the apoptotic cell rate was determined again. Results showed that the mRNA level of miR-21 was highly expressed in osteosarcoma tissues compared with adjacent tissues. Overexpression of miR-21 improved cell viability and survival but suppressed apoptosis. Caspase 8 was a direct target of miR-21, and it was negatively regulated by miR-21. Moreover, miR-21 suppression attenuated caspase 8 silencing and induced the decrease in apoptosis. In conclusion, overexpression of miR-21 suppressed SAOS-2 cell apoptosis via directly targeting caspase 8.

MicroRNA-124 upregulation inhibits proliferation and invasion of osteosarcoma cells by targeting sphingosine kinase 1

Increasing evidence has confirmed that the dysregulation of microRNAs (miRNAs) contributes to the proliferation and invasion of human cancers. Previous studies have shown that the dysregulation of miR-124 is in numerous cancers. However, the roles of miR-124 in human osteosarcoma (OS) have not been well clarified. Therefore, this study was to investigate the biological functions and molecular mechanisms of miR-124 in OS cell lines, discussing whether it could be a therapeutic biomarker of OS in the future. In this study, our results demonstrated that miR-124 was down-regulated in OS cell lines and tissues. Furthermore, the low level of miR-124 was associated with increased expression of Sphingosine kinase 1 (SPHK1) in OS cells and tissues. Up-regulation of miR-124 significantly inhibited cell proliferation, invasion, and MMP-2 and -9 expressions of OS cells. Bioinformatics analysis predicted that the SPHK1 was a potential target of miR-124. Further study by luciferase reporter assay demonstrated that miR-124 could directly target SPHK1. Overexpression of SPHK1 in OS cells transfected with miR-124 mimic partially reversed the inhibitory of miR-124. In conclusion, miR-124 inhibited cell proliferation and invasion in OS cells by downregulation of SPHK1, and that downregulation of SPHK1 was essential for the miR-124-inhibited cell invasion and in OS cells.