Osteosarcoma (OS) is the most common primary malignant bone tumor that more commonly occurs in children and adolescents. The most commonly used treatment for OS is surgery combined with chemotherapy, but the treatment outcomes are typically unsatisfactory. High rates of metastasis and post-treatment recurrence rates are major challenges in the treatment of OS. This underlines the need for studying the in-depth characterization of the pathogenetic mechanisms of OS and development of more effective therapeutic modalities. Previous studies have demonstrated the important role of the bone microenvironment and the regulation of signaling pathways in the occurrence and development of OS. In this review, we discussed the available evidence pertaining to the mechanisms of OS development and identified therapeutic targets for OS. We also summarized the available treatment modalities for OS and identified future priorities for therapeutics research.
Child ; Adolescent ; Humans ; Bone Neoplasms/drug therapy* ; Signal Transduction ; Bone and Bones/metabolism* ; Treatment Outcome ; Osteosarcoma/drug therapy* ; Tumor Microenvironment

OBJECTIVE: To investigate the prognostic value and mechanism of long non-coding RNA DLEU1(LncRNA DLEU1) in osteosarcoma. METHODS: The tissue samples and clinical data of 86 patients with osteosarcoma treated by orthopaedic surgery in our hospital from January 2012 to December 2014 were retrospectively collected. The expression of LncRNA DLEU1 in pathological tissues was detected by qRT-PCR, then the patients were divided into high and low expression of LncRNA DLEU1 groups. Osteosarcoma cell line HOS was divided into two groups, down-regulated expression group (si-DLEU1 group) and negative control group (si-NC group). LncRNA DLEU1 siRNA and negative control sequence were transfected by Lipofectamine 3000. Chi-square test was used to analyze the relationship between the expression of LncRNA DLEU1 and the clinicopathological factors of osteosarcoma. Kaplan-Meier method was used to compare the difference of the overall survival rate of osteosarcoma patients between the high and low expression groups of LncRNA DLEU1. The risk factors affecting the overall survival rate of osteosarcoma were analyzed by single factor and multifactor analysis. The number of invasive cells in the two groups was determined and compared by Transwell assay. RESULTS: The expression of LncRNA DLEU1 in osteosarcoma tissue was higher than that in adjacent tissues (P<0.001). The expression of LncRNA DLEU1 in human osteosarcoma cell lines (MG-63, U-2 OS, and HOS) was significantly higher than that in human osteoblast line hFOB 1.19 (P<0.001). The expression of LncRNA DLEU1 was significantly correlated with Enneking stage (P<0.001), distant metastasis (P=0.016), and histological grade (P=0.028). The 1-year overall survival rate of the LncRNA DLEU1 high expression group was significantly higher than that of the low expression group (90.7% vs 60.5%, P<0.001). The 5-year overall survival rate of the LncRNA DLEU1 high expression group was significantly higher than that of the low expression group (32.6% vs 11.6%, P<0.001). Univariate analysis showed that Enneking stage (P<0.001), tumor size (P=0.043), distant metastasis (P<0.001), histological grade (P<0.001), and expression of LncRNA DLEU1 (P<0.001) were risk factors for overall survival of osteosarcoma patients. Multivariate analysis showed that high expression of LncRNA DLEU1 [HR=1.948, 95% CI(1.141, 3.641), P=0.012] and distant metastasis[HR=4.108, 95% CI(2.169, 7.780), P<0.001] were independent risk factors for overall survival of osteosarcoma patients. The number of invasive cells in si-DLEU1 group was significantly lesser than that in si-NC group(139±13 vs 357±31, P<0.001). CONCLUSION High expression of LncRNA DLEU1 is a molecular marker affecting the prognosis of osteosarcoma patients. Downregulation of LncRNA DLEU1 can inhibit the invasion of osteosarcoma cells.
Humans ; Prognosis ; RNA, Long Noncoding/metabolism* ; Retrospective Studies ; Cell Proliferation/genetics* ; Cell Line, Tumor ; Osteosarcoma/genetics* ; Bone Neoplasms/pathology*

OBJECTIVE: To screen for aberrantly expressed genes in osteosarcoma cells and investigate the role of RHPN2 in regulating the proliferation, apoptosis, migration and tumorigenic abilities of osteosarcoma cells. METHODS: We used GEO2R to analyze the differential gene expression profile between osteosarcoma cells and normal cells in the GSE70414 dataset. RTqPCR and Western blotting were performed to detect RHPN2 expression in osteosarcoma cell lines MG-63, 143B and SAOS2. Two RHPN2-shRNA and a control NC-shRNA were designed to silence the expression of RHPN2 in 143B cells, and CCK8 assay, colony-forming assay, annexin V-FITC/PI staining and scratch assays were carried out to examine the changes in proliferation, apoptosis and migration of the cells. We also established nude mouse models bearing osteosarcoma xenografts derived 143B cells and RHPN2-shRNA-transfected 143B cells, and assessed the effect of RHPN2 silencing on osteosarcoma cell tumorigenesis using HE staining. Kaplan-Meier survival curves were used to analyze the correlation between RHPN2 expression and survival outcomes of patients with osteosarcoma. RESULTS: RHPN2 expression was significantly upregulated in osteosarcoma cell lines MG-63, 143B and SAOS2 (P < 0.01). Silencing of RHPN2 significantly inhibited the proliferation and migration of 143B cells in vitro, promoted cell apoptosis (P < 0.01), and suppressed tumorigenic capacity of the cells in nude mice. A high expression of RHPN2 was significantly correlated with a poor prognosis of patients with osteosarcoma (P < 0.05). CONCLUSION RHPN2 is highly expressed in osteosarcoma cells to promote cell proliferation and migration and inhibits cell apoptosis. A high expression of RHPN2 is associated with a poorer prognosis of the patients with osteosarcoma.
Adaptor Proteins, Signal Transducing/metabolism* ; Animals ; Apoptosis ; Bone Neoplasms/metabolism* ; Carcinogenesis ; Cell Line, Tumor ; Cell Movement/physiology* ; Cell Proliferation/physiology* ; Humans ; Immediate-Early Proteins ; Mice ; Mice, Nude ; Osteosarcoma/metabolism* ; RNA, Small Interfering/genetics*

OBJECTIVE: To study the effects and mechanisms of miR-181a-5p on the proliferation, cycle and migration of HOS osteosarcoma cells. METHODS: Real-time quantitative PCR was used to detect the expression of miR-181a-5p and HOXB4 in osteoblast hFOB1.19 cell line and osteosarcoma cell lines (HOS, U2OS, MG63). miR-181a-5p mimics and miR-181a-5p inhibitors were respectively transfected into HOS cells by Lipofectamine 2000, and miR NC group was set as control group. CCK-8 method was used to detect the change in cell proliferation. Flow cytometry was used to detect the changes in cell cycles. Wound healing experiments and Transwell migration experiments were used to detect the changes in cell migration ability. The target gene of miR-181a-5p was predicted by Targetscan website and validated by Dual-luciferase reporter gene system and Western blot. RESULTS: Compared with osteoblast hFOB1.19, miR-181a-5p was low expressed in osteosarcoma cells HOS, U2OS, and MG63(P<0.05), while HOXB4 was high expressed in osteosarcoma cells HOS, U2OS, and MG63(P<0.05). Compared with the miR NC group, over expression of miR-181a-5p inhibited the proliferation and migration of osteosarcoma HOS cells, and the number of cells in S phase decreased(P<0.05). However, knockdown miR-181a-5p promoted the proliferation and migration of osteosarcoma HOS cells, the cells in S phase increased(P<0.05). Bioinformatics prediction and Dual-luciferase reporter gene system validate HOXB4 as a downstream target gene of miR-181a-5p(P<0.05). Western blot showed that miR-181a-5p over expression or knockdown significantly down-regulated or up-regulated HOXB4 expressions in the HOS cells respectively(P<0.05). CONCLUSION miR-181a-5p is down expressed in osteosarcoma cells, and over-expression miR-181a-5p inhibits the proliferation, cell cycle and migration ability of osteosarcoma cells by targeting HOXB4.
Humans ; Apoptosis ; Bone Neoplasms/genetics* ; Cell Line, Tumor ; Cell Proliferation/genetics* ; Homeodomain Proteins/genetics* ; MicroRNAs/metabolism* ; Osteosarcoma/genetics* ; Transcription Factors/genetics*

Objective: To explore the effects of circTNPO1 on the proliferation and metastasis of osteosarcoma (OS) by sponging miR-338-3p. Methods: The expression of circTNPO1 on osteoblasts and multiple OS cell lines were detected by qRT-PCR. CircTNPO1 stable knockdown 143B cell line was constructed by sh-circTNPO1. Cell count kit 8 (CCK-8) assay and wound healing assay were applied to evaluate the proliferation and metastasis of this cell. Luciferase reporter assay was used to explore the binding between circTNPO1 and miR-338-3p. In xenograft tumor model, miR-338-3p inhibitor or its control was injected into the circTNPO1 knockdown tumors. The weight and size of the tumors were evaluated and Ki-67 expression was detected by immunohistochemistry. Results: The RNA expression of circTNPO1 in OS cell lines U2OS, HOS, MG63, 143B, ZOS and ZOSM were 2.73±0.27, 3.18±0.54, 4.33±0.52, 5.75±0.65, 4.50±0.49 and 3.96±0.35, respectively, higher than 1.00±0.09 in hFOB1.19 (P<0.001). CCK-8 assay revealed that after 48 h and 72 h, the absorbance of sh-circTNPO1 #1 was 0.81±0.05 and 1.09±0.06, while sh-circTNPO1 #2 143B cells was 0.84±0.04 and 1.2±0.04, which were sharply reduced compared with the control (1.00±0.06 and 1.49±0.06, P<0.001); after 48 h and 72 h, the absorbance of 143B cells transfected with circTNPO1 #1 and miR-338-3p (0.92±0.06 and 1.32±0.07) were higher than those of cells transfected with sh-circTNPO1 cells and miR NC (0.92±0.06 and 1.32±0.07, P<0.050). Wound healing assay demonstrated that the 24 hour-migration rates of sh-circTNPO1 #1 and sh-circTNPO1 #2 cells were (24.43±2.15)% and (39.70±4.20)% respectively, which were significantly lower than that of the control [(56.51±3.27)%, P<0.010]; the migration rates of sh-circTNPO1 #1+ miR NC and sh-circTNPO1 #1+ miR-338-3p inhibitor were (26.70±2.21)% and (46.10±5.71)%, with a significant difference (P<0.005). In xenograft tumor model, the weight and size of tumors in control, sh-circTNPO1 #1+ miR NC and sh-circTNPO1 #1+ miR-338-3p inhibitor mice were (458.80±158.10) mg, (262.50±82.09) mg, (395.40±137.60) mg and (593.00±228.40) mm(2,) (203.30±144.20) mm(2,) (488.60±208.60) mm(2,) respectively. Compared with control, sh-circTNPO1 tumors were significantly smaller (P<0.01). Injection with miR-338-3p inhibitor significantly reversed both the weight and size of tumors (P<0.05). Conclusion: CircTNPO1 promotes the proliferation and metastasis of OS by sponging miR-338-3p, which could be a new target for OS treatments.
Animals ; Bone Neoplasms/pathology* ; Cell Line, Tumor ; Cell Movement ; Cell Proliferation/genetics* ; Gene Expression Regulation, Neoplastic ; Humans ; Ki-67 Antigen/metabolism* ; Mice ; MicroRNAs/metabolism* ; Osteosarcoma/secondary* ; RNA, Circular/metabolism* ; Sincalide/metabolism*

To investigate the effect of miR-30a/HMGA2-mediated autophagy in osteosarcoma cells on apoptosis induced by chemotherapeutics. 
 Methods: A total of 30 osteosarcoma tissues of sensitive and resistant to chemotherapeutics were divided into a chemotherapy-sensitive group and a chemotherapy-resistant group. The mRNA expression levels of miR-30a and high mobility group protein A2 (HMGA2) in the chemotherapy-sensitive group and the chemotherapy-resistant group, and the mRNA expression levels of miR-30a in osteosarcoma U2-OS cells treated by cisplatin, doxorubicin and methotrexate at different concentrations were detected by real-time PCR. The expression levels of autophagy related protein Beclin 1, microtubule associated protein 1 light chain 3B (LC3B) and autophagy factor P62 were detected by Western blotting. The osteosarcoma U2-OS cells were transfected with miR-30a mimics and miR-30a inhibitors to construct a miR-30a high expression group, a miR-30a low expression group and a control group. The expression levels of Beclin 1, LC3B and P62 in osteosarcoma U2-OS cells after treatment of cisplatin and doxorubicin in these 3 groups were detected by Western blotting; the level of autophagy was detected by monodansylcada (MDC) staining; the level of ROS was detected by dihydroethidium (DHE); the level of cell surviving rate was detected by cell counting kit-8 (CCK-8); the level of apoptosis was detected by annexin APC/PI double staining; the level of mitochondria oxidative damage was detected by mitochondrial membrane potential assay kit with JC-1 (JC-1 method). The interaction between miR-30a and HMGA2 was detected by dual luciferase reporter assay. The osteosarcoma U2-OS cells were transfected with HMGA2 mimics and HMGA2-shRNA to construct a high HMGA2 group, a low HMGA2 group, and a control group. The expression levels of Beclin 1, LC3B and P62 in osteosarcoma U2-OS cells after the treatment of cisplatin were detected by Western blotting.
 Results: The level of miR-30a in the chemotherapy-resistant tissues was significantly lower than that in the chemotherapy-sensitive tissues (P<0.05), and the expression of HMGA2 was opposite comparing to that of miR-30a (P<0.05). After the treatment by low concentration (5 μmol/L) of chemotherapeutics, the level of miR-30a was down-regulated in osteosarcoma U2-OS cells, accompanied with up-regulation of Beclin 1 and LC3B (P<0.01) and down-regulation of P62 (P<0.01). Compared with the control group, the expression levels of Beclin 1 and LC3B were significantly decreased (P<0.05), and the expression level of P62 was significantly increased (P<0.05) in the miR-30a high expression group, which was opposite in the miR-30a low expression group. In the miR-30a high expression group treated by chemotherapeutics, the level of autophagy and the cell survival rate were lower than those in group with low expression of miR-30a, while the levels of ROS, the mitochondrial oxidative damage and the apoptosis were higher than those in group with low expression of miR-30a (all P<0.05). The targeting interaction between HMGA2 and miR-30a were verified by dual luciferase reporter assay. Compared with the control group, the expression levels of Beclin 1 and LC3B were significantly increased (P<0.05), and the expression level of P62 was significantly decreased (P<0.05) in the HMGA2 high expression group, which was opposite in the HMGA2 low expression group.
 Conclusion: Suppression of miR-30a/HMGA2-mediated autophagy in osteosarcoma cells is likely to enhance the therapeutic effect of chemotherapeutics.
Apoptosis ; Apoptosis Regulatory Proteins ; Autophagy ; Beclin-1 ; Bone Neoplasms ; Cell Line, Tumor ; HMGA2 Protein ; metabolism ; Humans ; MicroRNAs ; genetics ; Osteosarcoma

OBJECTIVEOsteosarcoma is the most common type of malignant bone tumor in children and adolescents. The role of E3 ligases in tumorigenesis is currently a focus in tumor research. In the present study, we investigated the role of the E3 ligase tripartite motif 21 (TRIM21) in osteosarcoma cell proliferation.

METHODS3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assays were used to assess osteosarcoma cell viability. U2-OS cells stably carrying a recombinant lentivirus expressing tetracycline-regulated TRIM21 were screened. Co-immunoprecipitation was coupled with LCMS/MS analysis to identify novel interacting partners of TRIM21. Co-immunoprecipitation and bimolecular fluorescence complementation (BIFC) were performed to validate the interactions between TRIM21 and its novel partner YWHAZ. A TRIM21-ΔRING construct was generated to test the effects of TRIM21 ligase activity on YWHAZ.

RESULTSTRIM21 positively regulated osteosarcoma cell proliferation. Overexpression of TRIM21 enhanced osteosarcoma cell tolerance toward various stresses. YWHAZ protein was identified as a novel interacting partner of TRIM21 and its expression levels were negatively regulated by TRIM21. The RING domain of TRIM21 was required for TRIM21 negative regulation of YWHAZ expression. However, overexpression of YWHAZ did not affect positive regulation of osteosarcoma cell proliferation by TRIM21.

CONCLUSIONOur results further clarify the molecular mechanisms underlying the pathogenesis of osteosarcoma.

14-3-3 Proteins ; genetics ; metabolism ; Cell Proliferation ; genetics ; Humans ; Osteosarcoma ; genetics ; Ribonucleoproteins ; genetics ; metabolism ; Tumor Cells, Cultured

PURPOSE: Long non-coding RNA taurine upregulated gene 1 (TUG1) is reported to be a vital regulator of the progression of various cancers. This study aimed to explore the exact roles and molecular mechanisms of TUG1 in osteosarcoma (OS) development. MATERIALS AND METHODS: Real-time quantitative PCR was applied to detect the expressions of TUG1 and microRNA-132-3p (miR-132-3p) in OS tissues and cells. Western blot was performed to measure protein levels of sex determining region Y-box 4 (SOX4). Cell viability was assessed using XTT assay. Cell apoptosis was evaluated using flow cytometry and caspase-3 activity detection assays. Bioinformatics analysis and luciferase reporter experiments were employed to confirm relationships among TUG1, miR-132-3p, and SOX4. RESULTS: TUG1 was highly expressed in human OS tissues, OS cell lines, and primary OS cells. TUG1 knockdown hindered proliferation and induced apoptosis in human OS cell lines and primary OS cells. Moreover, TUG1 inhibited miR-132-3p expression by direct interaction, and introduction of miR-132-3p inhibitor partly abrogated the effect of TUG1 knockdown on the proliferation and apoptosis of OS cells. Furthermore, SOX4 was validated as a target of miR-132-3p. Further functional analyses revealed that miR-132-3p inhibited proliferation and induced apoptosis of OS cells, while this effect was greatly abated following SOX4 overexpression. Moreover, TUG1 knockdown suppressed proliferation and promoted apoptosis by upregulating miR-132-3p and downregulating SOX4 in primary OS cells. CONCLUSION: TUG1 facilitated proliferation and suppressed apoptosis by regulating the miR-132-3p/SOX4 axis in human OS cell lines and primary OS cells. This finding provides a potential target for OS therapy.
Apoptosis/*genetics ; Biomarkers, Tumor ; Bone Neoplasms/genetics/metabolism/*pathology ; Cell Line, Tumor ; Cell Proliferation ; Gene Expression Regulation, Neoplastic/genetics ; Gene Knockdown Techniques ; Humans ; MicroRNAs/*genetics/metabolism ; Osteosarcoma/genetics/metabolism/*pathology ; RNA, Long Noncoding/*genetics/metabolism ; Real-Time Polymerase Chain Reaction ; Reverse Transcriptase Polymerase Chain Reaction ; SOXC Transcription Factors/genetics/*metabolism ; Transcriptional Activation ; Tumor Cells, Cultured ; Up-Regulation

Multidrug resistance (MDR) is one of the major obstacles in cancer chemotherapy. Our previous study has shown that icariin could reverse MDR in MG-63 doxorubicin-resistant (MG-63/DOX) cells. It is reported that icariin is usually metabolized to icariside II and icaritin. Herein, we investigated the effects of icariin, icariside II, and icaritin (ICT) on reversing MDR in MG-63/DOX cells. Among these compounds, ICT exhibited strongest effect and showed no obvious cytotoxicity effect on both MG-63 and MG-63/DOX cells ranging from 1 to 10 μmol·L. Furthermore, ICT increased accumulation of rhodamine 123 and 6-carboxyfluorescein diacetate and enhanced DOX-induced apoptosis in MG-63/DOX cells in a dose-dependent manner. Further studies demonstrated that ICT decreased the mRNA and protein levels of multidrug resistance protein 1 (MDR1) and multidrug resistance-associated protein 1 (MRP1). We also verified that blockade of STAT3 phosphorylation was involved in the reversal effect of multidrug resistance in MG-63/DOX cells. Taken together, these results indicated that ICT may be a potential candidate in chemotherapy for osteosarcoma.
ATP Binding Cassette Transporter, Subfamily B ; drug effects ; genetics ; metabolism ; Antineoplastic Agents ; pharmacology ; Apoptosis ; drug effects ; Cell Line, Tumor ; Cell Survival ; drug effects ; Dose-Response Relationship, Drug ; Doxorubicin ; metabolism ; pharmacology ; toxicity ; Drug Resistance, Multiple ; drug effects ; Drug Resistance, Neoplasm ; drug effects ; Flavonoids ; pharmacology ; Gene Expression Regulation, Neoplastic ; drug effects ; Humans ; Multidrug Resistance-Associated Proteins ; drug effects ; genetics ; metabolism ; Osteosarcoma ; drug therapy ; metabolism ; pathology ; Phosphorylation ; drug effects ; Rhodamine 123 ; metabolism ; STAT3 Transcription Factor ; antagonists & inhibitors ; metabolism ; Triterpenes ; pharmacology

BACKGROUND: Methotrexate (MTX), one of the main drugs used to treat osteosarcoma, is a representative folic acid antagonist. Polymorphisms of various enzymes involved in the metabolism of MTX could contribute to differences in response to MTX in pediatric osteosarcoma patients. METHODS: Blood and tissue samples were obtained from 37 pediatric osteosarcoma patients who were treated with high-dose MTX therapy. The following 4 single nucleotide polymorphisms (SNPs) were analyzed: ATIC 347C>G, MTHFR 677C>T, MTHFR 1298A>C and SLC19A1 80G>A. Serial plasma MTX concentrations after high-dose MTX therapy and MTX-induced toxicities were evaluated. Correlations among polymorphisms, MTX concentrations and treatment-induced toxicities were assessed. RESULTS: Plasma MTX levels at 48 hours after high-dose MTX infusion were significantly associated with SLC19A1 80G>A (P=0.031). Higher plasma levels of MTX at 48 and 72 hours were significantly associated with MTX-induced mucositis (P=0.007 and P=0.046) and renal toxicity (P=0.002), respectively. SNP of SLC19A1 gene was associated with development of severe mucositis (P=0.026). CONCLUSION: This study suggests that plasma levels of MTX are associated with GI and renal toxicities after high-dose MTX therapy, and genetic polymorphisms that affect the metabolism of MTX may influence drug concentrations and development of significant side effects in pediatric patients treated with high-dose MTX.
Folic Acid* ; Humans ; Metabolism ; Methotrexate* ; Mucositis ; Osteosarcoma* ; Plasma ; Polymorphism, Genetic* ; Polymorphism, Single Nucleotide