Genetic factors conferring metastasis in osteosarcoma

Unveiling the protein signature of the human osteosarcoma 3AB-OS cancer stem cell line

In cancer research today, one of the major challenges is the eradication of cancer stem cells (CSCs) within the tumor mass. These cells play a crucial role in initiating, growing, and maintaining the tumor. Evidence has demonstrated the presence and significance of CSCs in the development and progression of osteosarcoma (OS). However, our understanding of the specific markers for OS stem cells remains limited. In this study, we aim to identify distinct biomarkers for this cell population by conducting a proteomic analysis comparing OS stem cells to their non-stem counterparts. Our investigation focuses on a particular cell line called 3AB-OS, which exhibits stem-like characteristics, and its differentiated parental cell line, MG63. Through this research, we discovered 63 proteins exclusively expressed in 3AB-OS cells. Applying an in silico bioinformatics approach, we determined that the majority of these proteins are associated with RNA metabolism. Additionally, we identified a potential correlation between the insulin-like growth factor-binding proteins (IGF2BPs) signaling pathway and the tumorigenic and stemness features observed in 3AB-OS cells.

Galectin-3 inhibition boosts the therapeutic efficacy of Semliki Forest virus in pediatric osteosarcoma

The outcomes of metastatic and nonresponder pediatric osteosarcoma patients are very poor and have not improved in the last 30 years. These tumors harbor a highly immunosuppressive environment, making existing immunotherapies ineffective. Here, we evaluated the use of Semliki Forest virus (SFV) vectors expressing galectin-3 (Gal3) inhibitors as therapeutic tools, since both the inhibition of Gal3, which is involved in immunosuppression and metastasis, and virotherapy based on SFV have been demonstrated to reduce tumor progression in different tumor models. In vitro, inhibitors based on the Gal3 amino-terminal domain alone (Gal3-N) or fused to a Gal3 peptide inhibitor (Gal3-N-C12) were able to block the binding of Gal3 to the surface of activated T cells. In vivo, SFV expressing Gal3-N-C12 induced strong antitumor responses in orthotopic K7M2 and MOS-J osteosarcoma tumors, leading to complete regressions in 47% and 30% of mice, respectively. Pulmonary metastases were also reduced in K7M2 tumor-bearing mice after treatment with SFV-Gal3-N-C12. Both the antitumor and antimetastatic responses were dependent on modulation of the immune system, primarily including an increase in tumor-infiltrating lymphocytes and a reduction in the immunosuppressive environment inside tumors. Our results demonstrated that SFV-Gal3-N-C12 could constitute a potential therapeutic agent for osteosarcoma patients expressing Gal3.

AHA1 upregulates IDH1 and metabolic activity to promote growth and metastasis and predicts prognosis in osteosarcoma

Osteosarcoma (OS) is the most common primary malignant bone tumor in children and adolescents. Although activator of HSP90 ATPase activity 1 (AHA1) is reported to be a potential oncogene, its role in osteosarcoma progression remains largely unclear. Since metabolism reprogramming is involved in tumorigenesis and cancer metastasis, the relationship between AHA1 and cancer metabolism is unknown. In this study, we found that AHA1 is significantly overexpressed in osteosarcoma and related to the prognosis of osteosarcoma patients. AHA1 promotes the growth and metastasis of osteosarcoma both in vitro and in vivo. Mechanistically, AHA1 upregulates the metabolic activity to meet cellular bioenergetic needs in osteosarcoma. Notably, we identified that isocitrate dehydrogenase 1 (IDH1) is a novel client protein of Hsp90-AHA1. Furthermore, the IDH1 protein level was positively correlated with AHA1 in osteosarcoma. And IDH1 overexpression could partially reverse the effect of AHA1 knockdown on cell growth and migration of osteosarcoma. Moreover, high IDH1 level was also associated with poor prognosis of osteosarcoma patients. This study demonstrates that AHA1 positively regulates IDH1 and metabolic activity to promote osteosarcoma growth and metastasis, which provides novel prognostic biomarkers and promising therapeutic targets for osteosarcoma patients.

Tumor-derived Exosomes Induced M2 Macrophage Polarization and Promoted the Metastasis of Osteosarcoma Cells Through Tim-3

INTRODUCTION

Osteosarcoma, the most prevalent primary malignancy of the bone, is often presented with high-grade subclinical metastatic disease that metastasizes at very early stages. Exosomes, as molecular information carriers, may play a potent role in the occurrence and development of tumors through oncogenic molecular reprogramming of tumor-associated macrophages (TAMs). In this study, we will investigate the effect of osteosarcoma-derived exosomes on the polarization of TAMs and decipher its underlying molecular mechanism.

MATERIAL AND METHODS

Osteosarcoma-derived exosomes from MG63 cells were isolated and characterized by transmission electron microscopy, and nano-particle size analysis. Double fluorescence staining was performed to confirm the macrophages phagocytosis of exosomes. Western blot, qRT-PCR, and transwell assays were conducted to assess the effect of exosomes on migration, invasion, and macrophage differentiation. The mouse model of osteosarcoma was established to evaluate the effects of exosomes on lung metastasis in vivo.

RESULTS

MG63 exosomes were successfully isolated and verified to be phagocytized by macrophages through fluorescence confocal microscopy. The results revealed that osteosarcoma cells could induce M2 type differentiation of macrophages largely through Tim-3 mediated by exosomes, which in turn could promote the migration, invasion, epithelial-mesenchymal transition (EMT), and lung metastasis of osteosarcoma cells through the secretion of cytokines including IL-10, TGF-β, and VEGF.

CONCLUSIONS

Our results demonstrated that osteosarcoma-derived exosomes induced M2 polarization of macrophages and promoted the invasion and metastasis of tumors through Tim-3; besides, the study also suggests a novel therapeutic target for future studies.

Insights in Osteosarcoma by Proton Nuclear Magnetic Resonance Serum Metabonomics

Pediatric osteosarcoma outcomes have improved over the last decades; however, patients who do not achieve a full resection of the tumor, even after aggressive chemotherapy, have the worst prognosis. At a genetic level, osteosarcoma presents many alterations, but there is scarce information on alterations at metabolomic levels. Therefore, an untargeted nuclear magnetic resonance metabonomic approach was used to reveal blood serum alterations, when samples were taken from 21 patients with osteosarcoma aged from 12–20 (18, 86%) to 43 (3, 14%) years before any anticancer therapy were collected. The results showed that metabolites differed greatly between osteosarcoma and healthy control serum samples, especially in lipids, aromatic amino acids (phenylalanine and tyrosine), and histidine concentrations. Besides, most of the loading plots point to protons of the fatty acyls (-CH₃ and -CH₂-) from very-low- and low-density lipoproteins and cholesterol, as crucial metabolites for discrimination of the patients with osteosarcoma from the healthy samples. The relevance of blood lipids in osteosarcoma was highlighted when analyzed together with the somatic mutations disclosed in tumor samples from the same cohort of patients, where six genes linked to the cholesterol metabolism were found being altered too. The high consistency of the discrimination between osteosarcoma and healthy control blood serum suggests that nuclear magnetic resonance could be successfully applied for osteosarcoma diagnostic and prognostic purposes, which could ameliorate the clinical efficacy of therapy.

The effects of common variants in MDM2 and GNRH2 genes on the risk and survival of osteosarcoma in Han populations from Northwest China

Accumulating evidence has shown that both MDM2 and GNRH2 might be related to Osteosarcoma (OS) susceptibility. The study aimed to evaluate the effects of common variants in MDM2 and GNRH2 genes on the risk and survival of osteosarcoma in Han populations from Northwest China. In the study, we recruited 2292 subjects including 596 OS patients and 1696 healthy controls and genotyped 16 selected tag SNPs (6 from GNRH2 and 10 from MDM2). Genetic association analyses were performed at the genotypic and allelic levels. Survival curves were made for OS patients with different genotypes. Two SNPs, rs1690916 (MDM2, P = 0.0002) and rs3761243 (GNRH2, P = 0.0004), were identified to be significantly associated with OS risk. Moreover, SNP rs3761243 was strongly associated with pathological fracture (P = 2.61 × 10^–14), metastasis (P < 2.2 × 10^–16), and Enneking stage (P < 2.2 × 10^–16) in the OS group. Furthermore, survival curves based on different genotypes of SNP rs3761243 were found to be significantly different (P = 0.0003), suggesting increased risk with more copies of C alleles. Our results provide supportive evidence for genetic associations of MDM2 and GNRH2 genes with susceptibility to OS, and for the positive correlation of SNP rs3761243 in GNRH2 with the survival status of OS patients in Han populations from Northwest China.

Inhibition of ATR-Chk1 signaling blocks DNA double-strand-break repair and induces cytoplasmic vacuolization in metastatic osteosarcoma

BACKGROUND

Ataxia-telangiectasia and Rad3 related protein kinase (ATR) is an essential regulator of the DNA damage response in various cancers; however, its expression and roles in osteosarcoma are unclear. We therefore chose to evaluate the significance and mechanism of ATR in metastatic osteosarcoma, as well as its potential to be a therapeutic target.

METHODS

The osteosarcoma tissue microarrays constructed from 70 patient specimens underwent immunohistochemistry to quantify ATR and activated phospho-ATR (pATR) expression and their correlation with clinical outcomes. ATR sublocalization within the metastatic osteosarcoma cells was confirmed by immunofluorescence assay. Cell proliferation, apoptosis, and migration were evaluated following treatment with ATR siRNA or the selective inhibitor Berzosertib. Antitumor effects were determined with ex vivo three-dimensional (3D) culture models, and the impacts on the DNA damage repair pathways were measured with Western blotting.

RESULTS

Elevated ATR and activated pATR expression correlated with shorter patient survival and less necrosis following neoadjuvant chemotherapy. Intranuclear sublocalization of ATR and pATR suggested a mechanism related to DNA replication. ATR knockdown with siRNA or inhibition with Berzosertib suppressed cell proliferation in a time- and dose-dependent manner and induced apoptosis. In addition, ATR inhibition decreased Chk1 phosphorylation while increasing γH2AX expression and PARP cleavage, consistent with the interference of DNA damage repair. The ATR inhibitor Berzosertib also produced the characteristic cytoplasmic vacuolization preceding cell death, and suppressed ex vivo 3D spheroid formation and cell motility.

CONCLUSION

The faithful dependence of cells on ATR signaling for survival and progression makes it an emerging therapeutic target in metastatic osteosarcoma.

By targeting TRAF6, miR-140-3p inhibits TGF-β1-induced human osteosarcoma epithelial-to-mesenchymal transition, migration, and invasion

OBJECTIVES

We evaluated the effects of miR-140-3p on EMT, cellular migration, and invasion in TGF-β1 treated human OS cells. Human fresh OS tissue and normal bone tissue specimens were gathered from 42 patients (29 male and 13 female, 11 to 24 years of age with a mean age of 17.5 ± 2.3 years) diagnosed with OS by pathology. By targeting TRAF6, miR-140-3p inhibits TGF-β1-induced human osteosarcoma epithelial-to-mesenchymal transition, migration, and invasion.

RESULTS

In this study, we found microRNA (miR)-140-3p to be down-regulated and tumor necrosis factor receptor-associated factor 6 (TRAF6) to be up-regulated in patient OS samples. Lower levels of miR-140-3p and higher levels of TRAF6 were found in the advanced Enneking stage of OS. Furthermore, both mRNA and protein levels of TRAF6 were negatively associated with miR-140-3p mRNA expression in human OS tissue. TRAF6 was verified as a direct target of miR-140-3p in TGF-β1-treated human U2OS cells. Further, a miR-140-3p mimic dramatically inhibited while a miR-140-3p inhibitor enhanced TGF-β1-induced epithelial-to-mesenchymal transition, migration, and invasion of U2OS cells. Small interfering RNA was found to silence TRAF6 and to partly reverse the effects of the miR-140-3p inhibitor on TGF-β1-treated U2OS cells in vitro.

CONCLUSION

These results demonstrate miR-140-3p to function as a tumor inhibitor of human OS cells by decreasing TRAF6 expression. miR-140-3p and TRAF6 may be valuable and novel biomarkers for diagnosis and treatment of OS.

Genetic Variant of NFIB is Associated With the Metastasis of Osteosarcoma in Chinese Population

Variant rs7034162 in NFIB was reported to be associated with metastasis of osteosarcoma in European cases with genome-wide significance. Our purpose was to replicate the association of rs7034162 with the metastasis of osteosarcoma in the Chinese population and to further characterize the expression level of NFIB in osteosarcoma tissues. A total of 321 patients were included in this study. Variant rs7034162 was genotyped for each patient using the Taqman genotyping assay. Fifty-two cases of tumor tissues and adjacent normal tissues were collected during surgery. The χ² test was used to investigate the association of rs7034162 with the metastasis of osteosarcoma. The Student t test was used to compare the gene expression between patients with metastasis and those without metastasis. The messenger RNA expression level of NFIB was then compared among different genotypes of rs7034162 with 1-way analysis of variance test. Ninety-three patients were found to have metastasis. Patients with genotype AA had remarkably higher incidence of metastasis than those with genotype TT (34.4% vs 17.1%, P = .002). Patients with metastasis were found to have significantly higher rate of allele A than those without metastasis (53.2% vs 43.9%, P = .03). The messenger RNA expression of NFIB was significantly lower in tumor tissues of patients with metastasis than in those without metastasis (0.00035 ± 0.00017 vs 0.00063 ± 0.0025, P < .001). Compared to patients with genotype TT, those with genotype AA had remarkably decreased expression of NFIB (0.00033 ± 0.0014 vs 0.00067 ± 0.00037, P = .01). Single-nucleotide polymorphism rs7034162 was associated with metastasis of osteosarcoma in the Chinese population possibly via downregulation of NFIB. Further network analyses revealing the related pathways can help elucidate the molecular mechanism of distant metastasis in patients with osteosarcoma.

MiR-16-1-3p and miR-16-2-3p possess strong tumor suppressive and antimetastatic properties in osteosarcoma

Osteosarcoma (OS) is an aggressive malignancy affecting mostly children and adolescents. MicroRNAs (miRNAs) play important roles in OS development and progression. Here we found that miR-16-1-3p and miR-16-2-3p "passenger" strands, as well as the "lead" miR-16-5p strand, are frequently downregulated and possess strong tumor suppressive functions in human OS. Furthermore, we report different although strongly overlapping functions for miR-16-1-3p and miR-16-2-3p in OS cells. Ectopic expression of these miRNAs affected primary tumor growth, metastasis seeding and chemoresistance and invasiveness of human OS cells. Loss-of-function experiments verified tumor suppressive functions of these miRNAs at endogenous levels of expression. Using RNA immunoprecipitation (RIP) assays, we identify direct targets of miR-16-1-3p and miR-16-2-3p in OS cells. Moreover, validation experiments identified FGFR2 as a direct target for miR-16-1-3p and miR-16-2-3p. Overall, our findings underscore the importance of passenger strand miRNAs, at least some, in osteosarcomagenesis.

The oncogenic role of GNL3 in the progression and metastasis of osteosarcoma

Background

GNL3 has been reported to be up-regulated in cancers and function in tumor progression, whereas the role of GNL3 in the progression of osteosarcoma remains unclear.

Materials and methods

In this study, we blocked the expression of GNL3 by siRNA interference in osteosarcoma cell lines MG63 and U20S. CCK8, colony formation, wound-healing, Transwell, flow cytometry, and Hoechst/PI staining assays were used to examine the effects of GNL3 knockdown on cell proliferation, migration, invasion and apoptosis in MG63 and U20S cells. The relative activity of MMP9 was detected using Gelatin zymography assay. Western blot was performed to detect the expression of related proteins.

Results

We found that silencing of GNL3 reduced the growth, migration, and invasion abilities of MG63 and U20S cells. Moreover, silencing GNL3 triggered cell cycle arrest in MG63 and U20S cells, as well as promoted cell apoptosis. In addition, depletion of GNL3 was observed to reduce the activity of MMP9 and suppress the process of epithelial–mesenchymal transition (EMT) through up-regulation of E-cadherin and down-regulation of N-cadherin. Furthermore, we found that X-box-binding protein 1 (XBP1) could bind to GNL3 using dual-luciferase reporter assay, and XBP1 overexpression could restore the inhibitory effects on proliferation, invasion, and EMT in MG63 and U20S cells caused by GNL3 knockdown.

Conclusion

These data suggest that GNL3 functions as an oncogene in the progression of osteosarcoma by regulation of EMT, and XBP1 is also involved in its mechanism.

Relationship of common variants in Interleukin 33 gene with susceptibility and prognosis of osteosarcoma in Han Chinese population

Osteosarcoma (OS) is one of the most common malignant bone tumors. Many previous studies have indicated that OS is a complex disease and that its development may be affected by multiple genetic factors, which may contribute to its carcinogenesis. The aim of the present study was to evaluate the relationship of IL-33 with susceptibility and prognosis of OS in Han Chinese individuals. A total of 1,605 study subjects including 507 OS patients and 1,098 controls were recruited. Eighteen SNPs mapped to IL-33 were selected for genotyping. Genetic associations between selected SNPs and OS disease status were evaluated. Survival analyses, including Kaplan-Meier analysis and Cox model fitting for significant SNPs, were performed. The functional consequences of significant SNPs were analyzed using a publicly available database. SNP rs1048274 was identified to be significantly associated with OS disease status (OR=0.75, P=1.53×10-4). Compared to the GA and GG groups, OS patients with the AA genotype of rs1048274 had better survival rate. The hazard ratio of SNP rs1048274 (AA group compared to GG+GA group) was 0.35 (95% confidence interval of 0.25-0.5) following adjustment for several clinical variables. In conclusion, our results suggested that IL-33 may play a key role in the etiology of OS, indicating IL-33 as a potential genetic risk factor of the development and prognosis of OS.

Long non-coding RNA XIST serves an oncogenic role in osteosarcoma by sponging miR-137

The long non-coding RNA X inactive-specific transcript (XIST) has been implicated in certain human cancers, including osteosarcoma (OS), but the molecular mechanism of XIST underlying OS progression remains to be fully uncovered. In the present study, reverse transcription-quantitative polymerase chain reaction data demonstrated that XIST was significantly upregulated in OS tissues and cell lines (Saos-2, U2OS, HOS and MG63) compared with adjacent non-tumour tissues and normal human osteoblast cell line HFOB1.19. Bioinformatics analysis and luciferase reporter gene assay data demonstrated that XIST could directly target microRNA (miR)-137 and negatively regulate the expression of miR-137 in Saos-2 and U2OS cells. Furthermore, miR-137 was markedly downregulated in OS tissues and cell lines. An inverse association between XIST and miR-137 expression was observed in OS tissues. Knockdown of XIST caused a significant reduction in cell proliferation and invasion and suppressed matrix metalloproteinase (MMP2) and MMP9 protein levels in Saos-2 and U2OS cells. Furthermore, inhibition of miR-137 expression abolished the effects of XIST downregulation on the proliferation and invasion of OS cells. In summary, the present study suggests that XIST promotes OS cell proliferation and invasion by inhibition of miR-137 expression. Thus, XIST may be a potential therapeutic target for the treatment of OS.

LAMP3 plays an oncogenic role in osteosarcoma cells partially by inhibiting TP53

BACKGROUND

Osteosarcoma (OS) is a common malignant tumor that predominantly occurs in adolescents. Its most common metastasis is to the lungs. As shown in our earlier study, lysosome-associated membrane glycoprotein 3 (LAMP3) is highly upregulated in metastatic OS. However, its role in the regulation of OS cell viability and apoptosis remains unknown.

METHODS

We knocked down and overexpressed LAMP3 in OS cells and assessed the cell viability and apoptosis. Then, we investigated the expression of apoptosis-associated genes to identify the downstream gene(s) of LAMP3.

RESULTS

Knockdown of LAMP3 significantly inhibited OS cell viability and promoted apoptosis. TP53, which is involved in the apoptosis pathway, was found to be highly upregulated after knockdown of LAMP3. Overexpression of LAMP3 significantly increased cell viability and abrogated apoptosis. Importantly, subsequent knockdown of TP53 partially suppressed the increased OS cell apoptosis induced by the inhibition of LAMP3, suggesting that TP53 is a key functional downstream gene of LAMP3.

CONCLUSIONS

Our findings suggest that LAMP3 promotes OS cell viability and survival by regulating TP53 expression.

The effects of TRAF6 on proliferation, apoptosis and invasion in osteosarcoma are regulated by miR-124

The present study aimed to verify tumor necrosis factor receptor‑associated factor 6 (TRAF6) as the target gene of microRNA-124 (miR-124). In addition, the expression of miR‑124 was investigated in osteosarcoma tissues and cells, and its effects on the biological characteristics of osteosarcoma cells were determined, in order to provide an experimental and theoretical basis for the application of TRAF6 in the treatment of osteosarcoma. A fluorescence reporter enzyme system was used to verify TRAF6 as a target gene of miR‑124, and western blotting was used to detect the effects of miR‑124 on the protein expression levels of TRAF6 in cells. The expression levels of miR‑124 were detected in osteosarcoma tissues and an osteosarcoma cell line (MG‑63) by quantitative polymerase chain reaction (qPCR). In addition, a total of 48 h post‑transfection of MG‑63 cells with a miR‑124 mimic, qPCR was used to detect the expression levels of miR‑124, and the effects of miR‑124 on the viability of MG‑63 human osteosarcoma cells was determined using the MTT method. The effects of miR‑124 on the cell cycle progression and apoptosis of MG‑63 cells were analyzed by flow cytometry, whereas the effects of miR‑124 on the migration of MG‑63 cells was detected using the Transwell invasion chamber analysis method. A TRAF6 recombinant expression plasmid (pcDNA3.1‑TRAF6) was also constructed, and MG‑63 cells were transfected with the recombinant plasmid and a miR‑124 mimic, in order to further validate the biological role of miR‑124 via the regulation of TRAF6. The results of the present study indicated that, compared with in the normal control group, the expression levels of miR‑124 were significantly increased in MG‑63 cells transfected with a miR‑124 mimic (P<0.01). In addition, the luciferase reporter gene system demonstrated that, compared with in the control group, relative luciferase activity was significantly reduced in the miR‑124 mimic group (P<0.01). The results of MTT analysis indicated that cell viability was also significantly reduced in response to the overexpression of miR‑124 in MG‑63 cells (P<0.01). Flow cytometric analysis demonstrated that the proportion of cells in S phase and G2/M phase was significantly decreased (P<0.01) in cells overexpressing miR‑124, and the number of apoptotic cells was significantly increased (P<0.01). Furthermore, the results of the Transwell invasion assay suggested that the number of invasive cells was significantly decreased following enhanced expression of miR‑124 (P<0.01). In MG‑63 cells overexpressing miR‑124 and TRAF6, the results of MTT, flow cytometric and Transwell assay analyses demonstrated that the overexpression of TRAF6 had the opposite biological effects compared to miR‑124 overexpression. In conclusion, the present study indicated that the expression levels of miR‑124 were downregulated in human osteosarcoma tissues and cells, and that miR‑124 is associated with negative regulation of TRAF6 expression; therefore, the role of TRAF6 in primary osteosarcoma may be regulated by miR‑124. Therapeutic strategies that enhance miR‑124 expression or inhibit TRAF6 expression may be beneficial for the treatment of patients with osteosarcoma.

MSP-4, an Antimicrobial Peptide, Induces Apoptosis via Activation of Extrinsic Fas/FasL- and Intrinsic Mitochondria-Mediated Pathways in One Osteosarcoma Cell Line

Osteosarcoma (OS) is a common malignant bone cancer. The relatively high density of a person's bone structure means low permeability for drugs, and so finding drugs that can be more effective is important and should not be delayed. MSPs are marine antimicrobial peptides (AMP) and natural compounds extracted from Nile tilapia (Oreochromis niloticus). MSP-4 is a part of the AMPs series, with the advantage of having a molecular weight of about 2.7-kDa and anticancer effects, although the responsible anticancer mechanism is not very clear. The goal of this study is to determine the workings of the mechanism associated with apoptosis resulting from MSP-4 in osteosarcoma MG63 cells. The study showed that MSP-4 significantly induced apoptosis in MG63 cells, with Western blot indicating that MSP-4 induced this apoptosis through an intrinsic pathway and an extrinsic pathway. Thus, a pretreatment system with a particular inhibitor of Z-IETD-FMK (caspase-8 inhibitor) and Z-LEHD-FMK (caspase-9 inhibitor) significantly attenuated the cleavage of caspase-3 and prevented apoptosis. These observations indicate that low concentrations of MSP-4 can help induce the apoptosis of MG63 through a Fas/FasL- and mitochondria-mediated pathway and suggest a potentially innovative alternative to the treatment of human osteosarcoma.

Correlation between chemotherapy resistance in osteosarcoma patients and PAK5 and Ezrin gene expression

The correlation between PAK5 (P21-activated kinase 5) and Ezrin gene expression and chemotherapy resistance of osteosarcoma patients was investigated. The cisplatin (CDDP)-resistance model of osteosarcoma cells SOSP-9607/CDDP was established to detect the cell growth curve. Methyl thiazolyl tetrazolium (MTT) assay was used to detect the drug resistance of cells to chemotherapy drugs. Transwell assay was used to detect the invasive capacity of cells. Semi-quantitative PCR (qPCR) was used to detect the mRNA expression levels in the drug resistance-related genes PAK5 and Ezrin. Western blot analysis was used to detect the protein expression levels in PAK5 and Ezrin. Tumor tissues were taken from the osteosarcoma patients with chemotherapy resistance to detect the expression levels of PAK5 and Ezrin via immunohistochemical detection, and the correlation between PAK5 and Ezrin expressions was studied. The results of MTT assay showed that the growth rate of SOSP-9607 was similar to that of SOSP-9607/CDDP, and the difference was not statistically significant (P>0.05). The sensitivity of SOSP-9607 to CDDP was significantly higher than that of SOSP-9607/CDDP, and the difference was statistically significant (P<0.01). Transwell assay showed that the migration capacity of SOSP-9607/CDDP was significantly better than that of SOSP-9607 (P<0.01), indicating that the drug resistance cell lines of osteosarcoma were constructed successfully. Semi-qPCR and western blot analysis showed that the protein expression levels in PAK5 and Ezrin in SOSP-9607/CDDP were significantly higher than those in SOSP-9607 (P<0.01). The results of immunohistochemistry showed that the expression quantities of PAK5 and Ezrin in osteosarcoma tissues were significantly higher than those in para-tumor tissues (P<0.01). Pearson's correlation analysis showed that expression of PAK5 and Ezrin was positively correlated (r=0.197, P=0.023). The osteosarcoma resistance is closely related to the expression levels of PAK5 and Ezrin genes. Thus, PAK5 and Ezrin genes may affect the tolerance of osteosarcoma patients to chemotherapy drugs during treatment via the synergistic effect.

MicroRNA-92b promotes cell proliferation and invasion in osteosarcoma by directly targeting Dickkopf-related protein 3

Deregulation of microRNA-92b (miR-92b) has been implicated in osteosarcoma. However, the underlying regulatory mechanism of miR-92b in osteosarcoma growth and metastasis remains largely unclear. In the present study, reverse transcription-quantitative polymerase chain reaction and western blotting were used to measure mRNA and protein expression. MTT and Transwell assays were conducted to determine cell proliferation and invasion, and a luciferase reporter assay was performed to confirm the association between miR-92b and Dickkopf3-related protein (DKK3). The results demonstrated that miR-92b was significantly upregulated in osteosarcoma tissues compared with matched adjacent non-tumor tissues. Additionally, high miR-92b levels were significantly associated with lung metastasis and advanced tumor, node, metastasis stage (P<0.05) but not with age, sex, tumor size, location, serum lactate dehydrogenase or serum alkaline phosphatase. miR-92b expression was also significantly upregulated in osteosarcoma cell lines compared with normal osteoblast cells. Knockdown of miR-92b significantly inhibited the proliferation and invasion of osteosarcoma U2OS cells (P<0.01). By contrast, overexpression of miR-92b significantly increased U2OS cell proliferation and invasion (P<0.01). DKK3 was identified as a target gene of miR-92b and it was demonstrated that DKK3 expression was negatively regulated by miR-92b in U2OS cells. Restoration of DKK3 expression abrogated the increased proliferation and invasion of U2OS cells induced by miR-92b overexpression. Notably, DKK3 was significantly downregulated in osteosarcoma tissues compared with adjacent non-tumor tissues and its expression was inversely correlated to miR-92b levels in osteosarcoma tissues. Taken together, these data indicate that miR-92b promotes cell proliferation and invasion in osteosarcoma by targeting DKK3. Therefore, miR-92b may become a potential therapeutic target for osteosarcoma.

E2F1 silencing inhibits migration and invasion of osteosarcoma cells via regulating DDR1 expression

In the present study, knockdown of E2F1 impaired the migration and invasion of osteosarcoma cells. Further analysis showed that E2F1 knockdown decreased the expression of discoidin domain receptor 1 (DDR1) which plays a crucial role in many fundamental processes such as cell differentiation, adhesion, migration and invasion. Luciferase and ChIP assays confirmed that E2F1 silencing attenuated the expression of DDR1 through disrupting E2F1-mediated transcription of DDR1 in osteosarcoma cells. Similarly with the effect of E2F1 silencing, DDR1 knockdown weakened the migratory and invasive capabilities of osteosarcoma cells; while overexpression of DDR1 resulted in a significant increase of cell motility and invasiveness, even after knocking down E2F1. Interestingly, inactivation of E2F1/DDR1 pathway by shRNA weakened STAT3 signaling and subsequently suppressed the epithelial-mesenchymal transition (EMT) of osteosarcoma cells, as shown with decreased vimentin, MMP2, MMP9, and increased E-cadherin. Consistently, high expressions of E2F1 and DDR1 observed in osteosarcoma tissues were related to TNM stage and metastasis. In addition, high level of E2F1 or DDR1 was associated with poor prognosis in osteosarcoma patients. These results suggest that E2F1/DDR1/STAT3 pathway is critical for malignancy of osteosarcoma, which may provide a novel prognostic indicator or approach for osteosarcoma therapy.

Forkhead box C1 is targeted by microRNA-133b and promotes cell proliferation and migration in osteosarcoma

Forkhead box C1 (FOXC1) has been demonstrated to act as an oncogene in a number of malignant tumors, though its underlying mechanism of action in osteosarcoma (OS) remains unknown. The present study evaluated the expression and regulatory role of FOXC1 in OS. Reverse transcription-quantitative polymerase chain reaction and western blot data indicated that FOXC1 was significantly upregulated in OS tissues and cell lines when compared with adjacent non-tumor tissues (P<0.001) and normal human osteoblast cells (P<0.01), respectively. Moreover, levels of FOXC1 expression were significantly higher in OS at advanced clinical stage (III–IV) when compared with that at low clinical stage (I–II; P<0.001). Knockdown of FOXC1 expression caused a significant decrease in the proliferation and migration of OS U2OS cells (P<0.01), while overexpression of FOXC1 significantly promoted U2OS cell proliferation and migration (P<0.01), relative to control U2OS cells. Furthermore, FOXC1 was identified as a direct target of microRNA (miR)-133b, a reported tumor-suppressive miR in OS. The protein expression of FOXC1 was negatively regulated by miR-133b in U2OS cells (P<0.01), and miR-133b expression was inversely correlated with FOXC1 expression in OS. In conclusion, the present study demonstrated that FOXC1, targeted by miR-133b, may promote cell proliferation and migration in OS. Thus, FOXC1 may be a potential therapeutic target in the treatment of OS.

Tim-3 as a diagnostic and prognostic biomarker of osteosarcoma

Osteosarcoma is the most frequent primary bone tumor that affects adolescents and children. However, diagnostic and prognostic biomarkers for osteosarcoma remain lacking. (Tim-3) T-cell immunoglobulin domain and mucin domain-3, which negatively regulates T cell helper (Th1) cells and affects cytokine expression, has attracted increasing attention due to its critical role in regulating both adaptive and innate immune cells. In this study, we evaluated serum soluble Tim-3 level in osteosarcoma patients to explore its diagnostic and prognostic value for this particular malignancy. Serum soluble Tim-3 level was measured with enzyme-linked immunosorbent assay in 120 osteosarcoma patients, 120 benign bone tumors patients and 120 healthy controls, followed by analysis of the correlation with clinic pathological characteristics. Receiver operating curves, Kaplan-Meier curves, and log-rank analyses as well as Cox proportional hazard models were used to evaluate the diagnostic and prognostic significance. Serum solubleTim-3 level was remarkably elevated in osteosarcoma patients. Osteosarcoma patients with larger tumor size, late stages and distant metastases were accompanied with higher levels of Tim-3. ROC/AUC analysis indicated thatTim-3 served as a reliable marker to distinguish healthy participants from Tim-3 patients. Osteosarcoma patients with higher Tim-3 had relatively lower survival. Multivariate analyses for overall survival revealed that high serum soluble Tim-3 level was an independent prognostic factor for osteosarcoma. Furthermore, Tim-3 levels of CD8+ and CD4+ T cells were elevated in peripheral circulation of osteosarcoma patients. Therefore, It was indicated in our research that elevated serum soluble Tim-3 level might be a novel potential diagnostic and prognostic biomarker for osteosarcoma patients.

CXCL5 Plays a Promoting Role in Osteosarcoma Cell Migration and Invasion in Autocrine- and Paracrine-Dependent Manners

CXCL5, a CXC-type chemokine, is an important attractant for granulocytic immune cells by binding to its receptor CXCR2. Recently, CXCL5/CXCR2 has been found to play an oncogenic role in many human cancers. However, the exact role of CXCL5 in osteosarcoma cell migration and invasion has not been revealed. Here we found that the protein expression of CXCL5 was significantly increased in osteosarcoma tissues compared with that in matched adjacent nontumor tissues. Moreover, the expression of CXCL5 was significantly associated with advanced clinical stage and metastasis. Further investigation showed that the CXCL5 expression levels were also significantly increased in osteosarcoma cell lines, including Saos-2, MG63, U2OS, and SW1353, when compared with those in normal osteoblast hFoB1.19 cells. U2OS cells were further transfected with CXCL5-specific siRNA or overexpression plasmid. Knockdown of CXCL5 significantly suppressed U2OS cell migration and invasion. On the contrary, overexpression of CXLC5 remarkably promoted the migration and invasion of U2OS cells. Interestingly, both exogenous CXCL5 treatment and the conditioned medium of CXCL5-overexpressing hFoB1.19 cells could also enhance the migration and invasion of U2OS cells, suggesting that the promoting role of CXCL5 in U2OS cell migration and invasion is also in a paracrine-dependent manner. According to these data, our study demonstrates that CXCL5 is upregulated in osteosarcoma and may play an oncogenic role in osteosarcoma metastasis. Therefore, CXCL5 may become a potential therapeutic target for osteosarcoma treatment.