Signaling Pathway In Osteosarcoma Cells Research Articles

P-Coumaric Acid Inhibits Osteosarcoma Growth by Inhibiting PI3K/Akt Signaling Pathway.

P-coumaric acid (p-CA) is a kind of phenylpropionic acid derived from aromatic amino acids, which is widely distributed in many plants and human diets. It has strong pharmacological and inhibitory effects on a variety of tumors. However, the role of p-CA in osteosarcoma, a tumor with a poor prognosis, is still unknown. Therefore, we aimed to evaluate the effect of p-CA on osteosarcoma and explore its potential mechanism. This study aimed to investigate whether p-CA has an inhibitory effect on the growth of osteosarcoma cells and explore its potential mechanism. MTT assay and clonogenic assay were used to detect the effect of p-CA on the proliferation of osteosarcoma cells. The effect of p-CA on apoptosis of osteosarcoma cells was detected by the Hoechst staining and flow cytometry. The effects of p-CA on the migration and invasion of osteosarcoma cells were detected by scratch healing assay and Transwell invasion assay. Western blot and PI3K/Akt pathway activator 740Y-P were used to detect the anti-tumor mechanism of p-CA on osteosarcoma cells. The effect of p-CA on osteosarcoma cells in vivo was verified by an orthotopic osteosarcoma tumor animal model in nude mice. MTT assay and clonogenic assay showed that p-CA inhibited the proliferation of osteosarcoma cells. Hoechst stain and flow cytometry showed that p-CA could induce apoptosis of osteosarcoma cells and lead to G2 phase arrest of osteosarcoma cells. Transwell assay and scratch healing assay found that p-CA could inhibit the migration and invasion of osteosarcoma cells. Western blot showed that p-CA could inhibit the activity of the PI3K/Akt signaling pathway in osteosarcoma cells, and 740Y-P could reverse its inhibitory effect. In vivo mouse models, p-CA has an antitumor effect on osteosarcoma cells in vivo, and at the same time, it has less toxic side effects on mice. This study demonstrated that p-CA could effectively inhibit the proliferation, migration and invasion of osteosarcoma cells and promote apoptosis. p-CA may play an anti-osteosarcoma role by inhibiting PI3K/Akt signaling pathway.

Anticancer effect of crizotinib on osteosarcoma cells by targeting c-Met signaling pathway.

C-Met receptor and its ligand hepatocyte growth factor (HGF) are overexpressed in a variety of osteosarcoma cell lines and osteosarcoma pathological samples. It is suggested that c-Met/HGF plays an important role in the development of osteosarcoma. This study aimed to explore the anticancer effect of the c-Met-targeted drug crizotinib on osteosarcoma (OS) cells. The effects of crizotinib on the proliferation of osteosarcoma cells (SaOS2, MG-63 and MNNG) at different concentrations were detected by CCK8. Human osteosarcoma cell line MG-63 was used as an in vitro model to evaluate the effects of 2.5 μM crizotinib, 5.0 μM crizotinib and DMSO on cell apoptosis, cell cycle, migration and invasion. The expression of the c-Met signaling pathway in osteosarcoma cells was detected by western blot. The results showed that crizotinib inhibited the proliferation of cell lines in a concentration-dependent manner. Crizotinib significantly increased the number of apoptotic cells compared with the control group. Compared with the control group, crizotinib increased G0/G1 phase cells and decreased S phase cells. Compared with the control group, crizotinib inhibited the migration and invasion of osteosarcoma cells and decreased the expression of c-Met/Gab1/STAT5. This study will provide a promising therapeutic target and theoretical basis for the clinical application of crizotinib in osteosarcoma.

Piperine improves the sensitivity of osteosarcoma cells to doxorubicin by inducing apoptosis and inhibiting the PI3K/AKT/GSK-3β pathway

BackgroundOsteosarcoma is a primary bone malignancy associated with the highest incidence rate. Chemotherapy for osteosarcoma has not substantially changed, and survival of patients with metastatic tumours has reached a plateau. Doxorubicin (DOX) is a broad-spectrum anti-osteosarcoma drug; however, its application is limited due to its high cardiotoxicity. Piperine (PIP) has been verified to drive certain cancer cell death and increases chemosensitivity of DOX. However, the effects of PIP in promoting the chemosensitivity of osteosarcoma to DOX have not been studied.MethodsWe examined the combined effect of PIP and DOX on U2OS and 143B osteosarcoma cells. CCK-8 assays, scratch assays, flow cytometry analysis, and western blotting were performed. Furthermore, the effect of PIP combined with DOX on osteosarcoma tumours was observed in vivo using nude mice.ResultsPIP can increase the chemosensitivity of U2OS and 143B cells to DOX. Both in vitro and in vivo results showed the dramatic inhibition of cell proliferation and tumour growth by the combined therapy group compared to monotherapy groups. Apoptosis analysis revealed that PIP augments DOX-induced cell apoptosis by upregulating BAX and P53 expression, as well as reducing Bcl-2 expression. Furthermore, PIP also attenuated the initiation of the PI3K/AKT/GSK-3β signaling pathway in osteosarcoma cells by altering the expression levels of P-AKT, P-PI3K and P-GSK3β.ConclusionsThis study revealed for the first time that PIP can potentiate the sensitivity and cytotoxicity of DOX during osteosarcoma therapy in vitro and in vivo, which probably achieved by inhibiting the PI3K/AKT/GSK-3β signalling pathway.

Retraction: Down-regulation of MRPS23 inhibits LPS-induced proliferation and invasion via regulation of the NF-κB signaling pathway in osteosarcoma cells.

[This retracts the article DOI: 10.1039/C8RA08973F.].

FOXO3a-dependent up-regulation of HSP90 alleviates cisplatin-induced apoptosis by activating FUNDC1-mediated mitophagy in hypoxic osteosarcoma cells

Hypoxia-induced decrease in cisplatin (CDDP) sensitivity in human osteosarcoma (OS) is a significant obstacle to effective chemotherapy. Recently, mitophagy has been shown to be associated with CDDP sensitivity. However, whether it regulates hypoxia-induced decreases in CDDP sensitivity in OS and the underlying mechanisms remain unknown. In this study, we found that hypoxia activated mitophagy and suppressed mitophagy with specific inhibitors, mitochondrial division inhibitor-1 (Mdivi-1) or lysosome inhibitor chloroquine (CQ), which inhibited CDDP-induced apoptosis in hypoxic U-2OS and MG-63 cells. In addition, hypoxia upregulated the phosphorylation level of FUN14 domain-containing protein 1 (FUNDC1), whereas the activation of mitophagy and decreased CDDP sensitivity were inhibited by transfection with FUNDC1 small interfering RNA (siRNA). Hypoxia treatment also led to the up-regulation of heat shock protein 90 (HSP90), whereas HSP90 siRNA inhibited FUNDC1-mediated activation of mitophagy and decreased CDDP sensitivity. Furthermore, activation of Unc-51 like autophagy activating kinase 1 (Ulk1) was found in U-2OS and MG-63 cells after induction of hypoxia. Overexpression of Ulk1 prevented the inhibitory effect of HSP90 siRNA on the activation of FUNDC1 and mitophagy and decreased CDDP sensitivity in hypoxic U-2OS and MG-63 cells. Finally, hypoxia induced the activation of forkhead box transcription factor 3a (FOXO3a), whereas FOXO3a siRNA inhibited hypoxia-induced HSP90 up-regulation, Ulk1 activation, and FUNDC1-mediated activation of mitophagy, and decreased CDDP sensitivity in U-2OS and MG-63 cells. Using a chromatin immunoprecipitation (ChIP) assay, we confirmed that FOXO3a binds to the HSP90 promoter region. In conclusion, our findings suggest that hypoxia alleviates CDDP-induced apoptosis by activating mitophagy through the FOXO3a/HSP90/Ulk1/FUNDC1 signaling pathway in OS cells.

Effects of butein on human osteosarcoma cell proliferation, apoptosis, and autophagy through oxidative stress.

Osteosarcoma (OS) is a primary malignant bone tumor, and the cure rate has stagnated in the past three decades. Butein, a plant polyphenol extracted from many herbs, has been proved to possess anti-tumor activity. However, the effect of butein on human OS and the underlying mechanisms remain to be elucidated. The OS cell line 143B was used. The effects of butein were evaluated through the cell proliferation assay, flow cytometry, florescence and transmission electron microscopy, and western blotting. All statistical analyses were performed using GraphPad Prism 7.0. Butein was found to inhibit cell proliferation by causing G2/ M phase arrest in the 143B cells. In addition, butein suppressed the invasion of 143B cells upon IL-6 treatment. Additionally, we found that butein inhibited the invasion of 143B cells stimulated with IL-6 via the p-STAT3-MMP9 signaling pathway. Remarkably, butein triggered extrinsic and intrinsic apoptosis and autophagy of 143B cells. The process of autophagy may have tumor-supporting effects. Furthermore, butein induced oxidative stress as evidenced by ROS generation, increase in malondialdehyde (MDA) level, and decrease in GSH/GSSH ratio and GPX4 expression. N-acetylcysteine can reverse the change of ROS. Further experiments indicated apoptosis and autophagy could be attenuated by the N-acetyl-L-cysteine and c-Jun N-terminal kinase (JNK) inhibitor SP600125. Additionally, butein inhibited the Akt/mammalian target of rapamycin (mTOR) signaling pathway, and suppressed the Akt kinase activity increased apoptosis and autophagy. Our results revealed butein induced apoptosis and autophagy by regulating oxidative stress, activating the JNK signaling pathway and blocking the Akt/mTOR signaling pathway in OS cells. Additionally, butein inhibited the invasion of 143B cells stimulated with IL-6 through the pSTAT3- MMP9 signaling pathway. In view of these results, butein may be a potential anti-tumor drug targeting osteosarcoma.

Downregulation of TAF9B by miR-7-5p Inhibits the Progression of Osteosarcoma.

BackgroundOsteosarcoma (OS) is a malignant bone tumor with high metastatic potential. As a regulatory factor of apoptosis, TATA-box binding protein (TBP) associated factor 9B (TAF9B) is rarely studied in tumors.MethodsWe investigated the role and mechanism of TAF9B in OS cells by overexpression and knockdown. CCK8, colony formation, transwell, and flow cytometry analysis were performed to detect proliferation, migration, invasion, and apoptosis.ResultsTAF9B overexpression promotes the proliferation, migration, and invasion of OS cells, while TAF9B knockdown gives the opposite result. TAF9B inhibits apoptosis by upregulating Bcl-2 and downregulating Bax and Cleaved-caspase-3. Through starBase analysis, it was found that miR-7-5p can bind to the 3ʹUTR region of TAF9B, which is further confirmed by the dual luciferase reporter system assay. MiR-7-5p downregulates the expression of TAF9B in MG63 and U2OS cells. The proliferation and invasion of OS cells are inhibited after miR-7-5p mimics transfection and are promoted after miR-7-5p inhibitor transfection. TAF9B rescues the inhibitory effect of miR-7-5p on OS cells. TAF9B also activates the AKT/mTOR signaling pathway.ConclusionAccording to our results, miR-7-5p inhibits the translation of TAF9B and then suppresses growth and metastasis through the AKT/mTOR signaling pathway in OS cells, thereby indicating the potential value of miR-7-5p and TAF9B as therapeutic targets for human OS.

Chitooligosaccharides inhibit tumor progression and induce autophagy through the activation of the p53/mTOR pathway in osteosarcoma

Osteosarcoma is the most common primary sarcoma of bone. The use of Chitooligosaccharide (COS) as a drug carrier is an emerging new strategy for cancer therapy. However, the application of COS in osteosarcoma has not been reported. Here, we investigated the influence of COS on osteosarcoma, and suggested the underlying mechanism. Initially, we obtained COS with a low-degree-polymerized (DP = 2–6) by enzymatic hydrolysis. Using these COS materials, in vitro assays showed that COS elicited the anti-tumor activity against osteosarcoma cells. We found that COS had significant effects on cell growth, metastasis inhibition, apoptosis and autophagy induction, and triggered pro-apoptosis autophagy through p53/mTOR signaling pathway in osteosarcoma cells. In addition, the COS also inhibited tumor growth and metastasis in an osteosarcoma xenograft model in vivo. Finally, we showed that COS could increase sensitivity to chemotherapy of cisplatin in vitro. Thus, we provide experimental evidence to demonstrate that COS has anti-tumor effect on osteosarcoma, and COS can be a new potential therapeutic candidate for the treatment of osteosarcoma.

Piceatannol suppresses proliferation and induces apoptosis by regulation of the microRNA‑21/phosphatase and tensin homolog/protein kinase B signaling pathway in osteosarcoma cells.

Piceatannol (Pice), a natural analog of resveratrol, has been identified as an anticancer agent in various cancers by modulating the expression of microRNAs (miRNAs/miRs). However, the molecular mechanisms underlying the anticancer effects of Pice in osteosarcoma (OS) cells remain unclear. Thus, we hypothesized that Pice exerts anticancer effects on OS cells via the regulation of miRNA expression. Herein, we performed a MTT assay and flow cytometric analysis to determine cell viability and apoptosis in OS cells treated with Pice, respectively. Our results showed that Pice inhibits proliferation in a dose-dependent manner induces the apoptosis of OS cells. More importantly, miRNA microarray analysis identified that Pice alters miRNA expression profiles in human OS cells after treatment with Pice, and miR-21 was the most significantly downregulated. In addition, the therapeutic effects of Pice on OS cells were weakened by restoration of miR-21. In addition, we further verified that phosphatase and tensin homolog (PTEN), a tumor suppressor gene, is the functional target of miR-21 and Pice blocks the PTEN/AKT signaling pathway through inhibiting miR-21 expression in OS cells. Our findings suggested that Pice may exert anticancer effects on OS cells via mediating the miR-21/PTEN/AKT signaling pathway and could be considered to be a potential anticancer agent for treating OS.

<p>LncRNA TDRG1 Promotes Proliferation, Invasion and Epithelial-Mesenchymal Transformation of Osteosarcoma Through PI3K/AKT Signal Pathway</p>

ObjectiveThis study aimed to investigate the effect of long non-coding TDRG1 on proliferation and migration of osteosarcoma cells through PI3K/AKT signaling pathway.Materials and MethodsAltogether 87 cases of osteosarcoma tissues and adjacent tissues were collected, and osteosarcoma cells and osteoblasts were purchased. The expression of LncRNA TDRG1 in tissues and cells was detected by RT-PCR. Si-NC, si-TDRG1, and Sh-TDRG1 were transfected into osteosarcoma cells. L740Y-P (activator of PI3K/AKT pathway) and LY294002 (inhibitor of PI3k/AKT pathway) were used to interfere with PI3k/Akt signaling pathway in osteosarcoma cells. qRT-PCR was used to detect the expression of TDRG1 in osteosarcoma tissues and cells. WB was used to detect the expression of p-PI3K, p-AKT, N-cadherin, E-Cadherin, vimentin, Bax, Caspase-3, and Bcl-2 in cells. CCK-8, Transwell and cell scratch tests were used to detect cell proliferation, invasion and migration, and flow cytometry was used to detect cell apoptosis.ResultsTDRG1 was highly expressed in osteosarcoma, and the levels of p-PI3K and p-AKT were also up-regulated. Cell experiments showed that inhibiting the expression of TDRG1 could inhibit the proliferation, invasion, migration and EMT of osteosarcoma cells, promote the apoptosis of cells, and up-regulating the expression of TDRG1 could promote the proliferation, invasion, migration and EMT of osteosarcoma cells and inhibit the apoptosis of cells. The 740Y-P intervention could reverse the inhibition of Si-TDRG1 on osteosarcoma cell proliferation, invasion, migration and EMT and the promotion of cell apoptosis. LY294002 intervention could reverse the promotion of Sh-TDRG1 on osteosarcoma cell proliferation, invasion, migration and EMT and the inhibition of cell apoptosis.ConclusionTDRG1 is highly expressed in osteosarcoma tissue. Silencing the expression of osteosarcoma can inhibit the proliferation, invasion, migration and EMT of osteosarcoma cells by inhibiting PI3K/AKT signaling pathway, which may be a new target for diagnosis and treatment of osteosarcoma.

Andrographolide induces apoptosis in human osteosarcoma cells via the ROS/JNK pathway.

Osteosarcoma is the most common primary malignant tumor of the bone and the long-term survival of patients with this disease has remained unsatisfactory over the past several decades. Andrographolide, a traditional drug used in Chinese medicine, has been found to exert a significant antitumor effect against several types of cancer. However, relatively little is known about the effect of andrographolide on osteosarcoma and the underlying mechanisms. In the present study, it was shown that andrographolide inhibited osteosarcoma cell proliferation by arresting the cell cycle at the G2/M phase and increasing caspase-mediated apoptosis. Furthermore, treatment with andrographolide induced JNK activation and increased production of reactive oxygen species (ROS). The andrographolide-triggered apoptosis in osteosarcoma cells was partly abrogated by a JNK inhibitor and completely reversed by a ROS scavenger. Additionally, JNK activation and cell cycle arrest at the G2/M phase were prevented by administration of an ROS scavenger. In vivo, it was also found that andrographolide inhibited tumor growth by increasing the levels of ROS and activating JNK; thus inducing cytotoxicity in primary osteosarcoma cells. Together, the results of the present study suggest that andrographolide caused G2/M arrest and induced cell apoptosis via regulation of the ROS/JNK signaling pathway in osteosarcoma cells. Thus, andrographolide may serve as a promising antitumor therapeutic agent against osteosarcoma.

TRIM58 Interacts with Pyruvate Kinase M2 to Inhibit Tumorigenicity in Human Osteosarcoma Cells.

Background Tripartite motif containing 58 (TRIM58), an E3 ubiquitin ligase, is reported as a suppressor gene in certain human tumors. However, the biological function of TRIM58 in osteosarcoma (OS) is still less identified. Methods In the present study, TRIM58 induced silencing and overexpression in OS cells using RNA interference (RNAi) and lentiviral-mediated vector, respectively. Cell proliferation profiles were analyzed using cell counting kit-8 (CCK-8) assay. Cell apoptosis profiles were determined using a flow cytometer. qRT-PCR and western blot were used to determine gene expression. Coimmunoprecipitation (Co-IP) assay was used to examine protein interaction. Results Our results demonstrated TRIM58 was downregulated in human OS tissues. Overexpression of TRIM58 remarkably suppressed the growth of OS cells and decreased glucose transportation and lactate secretion. These results indicated that TRIM58 involved in the regulation of energy metabolism in OS cells. Importantly, TRIM58 interacted with pyruvate kinase M2 (PKM2) in OS cells. Moreover, TRIM58 might inhibit the activity of PKM2 through enhancing its polyubiquitination in OS cells. Conclusions This analysis not only explored a deep understanding of the biological function of TRIM58 but also indicated its signaling pathway in OS cells.

The Cytoplasmic Expression Of CLDN12 Predicts An Unfavorable Prognosis And Promotes Proliferation And Migration Of Osteosarcoma.

BackgroundTo date, the impact and potential molecular mechanisms of CLDN12 and its association with malignancy in osteosarcoma have not been determined.Materials and methodsIn the present study, the expression profiles of CLDN12 in osteosarcoma cell lines and tissues were explored by immunohistochemistry. A fetal osteoblast cell line was transfected with a eukaryotic expression plasmid, and endogenous CLDN12 in osteosarcoma cells were silenced through an RNA interference (RNAi) method. These transfections were verified, and the activation state of Thr308 site in protein kinase B (Akt) was explored by Western blotting. Moreover, the malignant phenotype of osteosarcoma cells was evaluated by cell counting kit-8 (CCK-8), colony formation, Transwell, and wound-healing assays. Furthermore, osteoblast cells were treated with the phosphatidylinositol-3-kinase (PI3K) inhibitor LY294002 to determine the impact of the PI3K/Akt signaling pathway on cell migration ability.ResultsThe results revealed that CLDN12 was overexpressed and localized in the cytoplasm of osteosarcoma cells, and its overexpression was associated with an unfavorable prognosis, irrespective of tumor node metastasis stage. In addition, the knockdown of CLDN12 in cultured osteosarcoma cells markedly attenuated cell proliferation and migration, as indicated by the Cell Counting Kit-8 assay, colony formation assay, scratch wound healing assay and Transwell migration assay. The results also demonstrated that the overexpression of CLDN12 increased the activation of Thr308 site in Akt in fetal osteoblast cells, and the PI3K inhibitor LY294002 partially decreased CLDN12-promoted proliferation and metastasis.ConclusionIn conclusion, the results of the present study indicated that CLDN12 promoted cell proliferation and migration through the PI3K/Akt signaling pathway in osteosarcoma cells, suggesting that CLDN12 may be a potential agent in the treatment of patients with osteosarcoma.

CSN5 controls the growth of osteosarcoma via modulating the EGFR/PI3K/Akt axis

CSN5, a critical subunit of the constitutive photomorphogenesis 9 (COP9) signalosome (CSN), functions as a potential tumor promoter in various cancers. However, the biological functions and clinical significance of CSN5 in osteosarcoma (OS) remains unclear. Here, we report that OS tumors overexpressed CSN5 compared with normal bone tissues, and CSN5 overexpression was obviously associated with the malignant phenotype and poor prognosis in patients with OS. In addition, high CSN5 expression significantly promoted the growth of OS cells, whereas CSN5 silence suppressed the tumorigenicity of OS cells. Furthermore, we found PI3K/Akt signaling pathway contributed to the effects of CSN5 in OS cells, and blocking the Akt pathway significantly inhibited the actions of CSN5. Mechanistically, we demonstrate that CSN5 positively regulated EGFR stability through reducing the levels of EGFR ubiquitination, thereby activating the PI3K/Akt signaling pathway in OS cells. Moreover, our results shown that the oncogenic effects of CSN5 on OS cells were EGFR dependent. Thus, CSN5 has a central role in regulating diverse aspects of the pathogenesis of OS, which could be a potential diagnostic and therapeutic target for OS.

Overexpression of FER1L4 promotes the apoptosis and suppresses epithelial-mesenchymal transition and stemness markers via activating PI3K/AKT signaling pathway in osteosarcoma cells

Novel long non-coding RNA Fer-1-like protein 4 (FER1L4) has been identified as a tumor suppressor in endometrial carcinoma, ovarian cancer, hepatocellular carcinoma, esophageal squamous cell carcinoma. However, the function of FER1L4 in osteosarcoma has not been clear. The aim of the research was to explore the effects of FER1L4 in osteosarcoma. Results showed that FER1L4 was observed to be lowly expressed in osteosarcoma cell lines (US-O2, MG-63 and SaOS-2 cells), especially MG63 cells. Besides, overexpression of FER1L4 remarkably repressed the proliferation, migration and invasion of MG63 cells. FER1L4-induced apoptotic cell death leaded to the activation of caspase-3 and Bax/Bcl2. Moreover, epithelial-mesenchymal transition (EMT) was tremendously suppressed by increased FER1L4, evidences were the increased E-cadherin and reduced vimentin and fibronectin. Blocking FER1L4 expression by sh-FER1L4 treatment increased the expression of SOX9, CD44, ALDH1, Nanog and Oct4, indicating that FER1L4 could effectively decrease cell stemness in osteosarcoma. Furthermore, the protein levels of p-AKT and p-PI3K were remarkably suppressed when FER1L4 was knocked down. In conclusion, the study indicated that FER1L4 acted as a tumor suppressor in osteosarcoma via activating PI3K/AKT pathway may be a new prognostic biomarker and potential therapeutic target for osteosarcoma intervention.

Knockdown of HOXB8 inhibits tumor growth and metastasis by the inactivation of Wnt/β-catenin signaling pathway in osteosarcoma

Homeobox B8 (HOXB8) is a member of HOX family and was reported to be dysregulated in human cancers. However, its expression pattern and function in human osteosarcoma (OS) remain unknown. The aim of the current study is to examine its expression and biological roles in human OS cells. Our results showed that HOXB8 was highly expressed in human OS tissues and cell lines. Knockdown of HOXB8 significantly suppressed the proliferation of OS cells in vitro and attenuated the tumor growth in a tumor xenograft model. In addition, knockdown of HOXB8 dramatically repressed the migration and invasion of OS cells. Furthermore, knockdown of HOXB8 efficiently prevented the activation of Wnt/β-catenin signaling pathway in OS cells. In conclusion, the findings of the present study demonstrated that knockdown of HOXB8 could suppress tumorigenesis and metastasis in OS through regulation of the Wnt/β-catenin signaling pathway. Thus, HOXB8 may represent a novel therapeutic target for the treatment of OS.

Artemisinin inhibits angiogenesis by regulating p38 MAPK/CREB/TSP-1 signaling pathway in osteosarcoma.

Osteosarcoma is the most common bone tumor and characterizes a high metastatic potential. In osteosarcoma, angiogenesis is reported to be closely associated with tumor metastasis. Understanding the underlying mechanisms and accordingly developing therapeutic strategies are urgently desired. Antimalarial agent, artemisinin, has been reported to inhibit tumor angiogenesis. However, we still knew little about the effects of artemisinin on angiogenesis and its potential molecular mechanisms in human osteosarcoma. In this study, we found that artemisinin could induce both the expression and secretion of thrombospondin-1 (TSP-1) in a dose-dependent way in osteosarcoma cells. In addition, TSP-1 could effectively restore the artemisinin-induced suppression of angiogenesis in human umbilical vein endothelial cells (HUVECs). More importantly, we further found that phosphorylation of cAMP response element-binding protein (CREB) bond specifically to the promoter of TSP-1 and promoted its transcriptional activation. Moreover, our results showed that artemisinin could induce the phosphorylation of CREB via the activation of p38 mitogen-activated protein kinase (MAPK) signaling pathway in osteosarcoma cells. In vivo, we also found that artemisinin could inhibit osteosarcoma proliferation and angiogenesis by regulating the p38 MAPK/CREB/TSP-1 signaling pathway. Taken together, our findings indicated that artemisinin could inhibit angiogenesis by regulating the p38 MAPK/CREB/TSP-1 signaling pathway in osteosarcoma.

Down-regulation of MRPS23 inhibits LPS-induced proliferation and invasion via regulation of the NF-κB signaling pathway in osteosarcoma cells.

Mitochondrial ribosomal protein S23 (MRPS23), encoded by a nuclear gene, is a participant in the translation of mitochondrial proteins. Recently, MRPS23 has been reported to be overexpressed in many types of cancers and have a close association with cancer progression. However, the specific roles of MRPS23 in osteosarcoma (OS) remain unknown. In this study, we investigated the expression pattern and biological functions of MRPS23 in OS cells. Our results demonstrated that MRPS23 was up-regulated in OS tissues and cell lines. Down-regulation of MRPS23 significantly inhibited OS cell proliferation and invasion induced by lipopolysaccharide (LPS) in vitro. Furthermore, the in vivo experiments showed that MRPS23 down-regulation markedly suppressed OS cell growth and metastasis induced by LPS. Mechanistically, down-regulation of MRPS23 inhibited the activity of NF-κB signaling pathway in OS cells. In conclusion, these findings indicated that MRPS23 may be a potential therapeutic target for OS treatment.

Downregulation of Homeobox B7 Inhibits the Tumorigenesis and Progression of Osteosarcoma.

Homeobox B7 (HOXB7), a member of the HOX gene family, plays a role in tumorigenesis. However, until now the expression status and role of HOXB7 in osteosarcoma remain unclear. Therefore, the present study aimed to investigate the functional role and mechanism of HOXB7 in osteosarcoma. Our results demonstrated that HOXB7 was overexpressed in osteosarcoma cell lines. Downregulation of HOXB7 significantly inhibited osteosarcoma cell proliferation in vitro, as well as attenuated xenograft tumor growth in vivo. Downregulation of HOXB7 also inhibited the migration and invasion of osteosarcoma cells. Furthermore, downregulation of HOXB7 significantly suppressed the protein expression levels of p-PI3K and p-Akt in U2OS cells. In summary, our data demonstrated that downregulation of HOXB7 inhibited proliferation, invasion, and tumorigenesis, partly through suppressing the PI3K/Akt signaling pathway in osteosarcoma cells. Our findings provide new insights into the role of HOXB7 in osteosarcoma and new therapeutic targets for the treatment of osteosarcoma.

Epigenetic silencing of the Wnt antagonist APCDD1 by promoter DNA hyper-methylation contributes to osteosarcoma cell invasion and metastasis

Osteosarcoma (OS) is the most common type of bone tumor in children and adults. However, the molecular mechanism underlying OS tumorigenesis remains unclear. Here, we report that the expression of APCDD1, a Wnt antagonist, was reduced in OS tissues and cells compared to adjacent normal tissue and osteoblast cells, respectively. Mechanistically, this was due to increased levels of methylation in the promoter region of the APCDD1 gene. Consistently, the DNA methyltransferase inhibitor 5-AZA-dC, reduced DNA methylation in the APCDD1 promoter, and restored APCDD1 expression in OS tissue and cells. Moreover, DNMT3a, but not DNMT1 or DNMT3b, was the major DNA methyltransferase that facilitated hyper-methylation of DNA in the APCDD1 promoter, thus reducing APCDD1 mRNA levels in OS tissues. Importantly, ectopic expression of APCDD1 suppressed activity of the Wnt/β-Catenin signaling pathway in OS cells and inhibited their invasion and reversed their EMT-like properties, while depletion of APCDD1 promoted invasion and metastasis of osteosarcoma cells in vitro and in vivo. Thus, we have provided the first evidence that APCDD1 expression is epigenetically silenced in OS, which may facilitate invasion and metastasis of OS cells.