[Cryptotanshinone down-regulates the expression of VEGF and inhibits angiogenesis in U2OS osteosarcoma cells].

OBJECTIVE: To explore the effect of cryptotanshinone (CTS) on vascular endothelial growth factor (VEGF) expression in U2OS osteosarcoma cells, with a focus on angiogenesis. METHODS: U2OS osteosarcoma cells cultured in vitro were divided into (20, 40, 80, 160) µmol/L CTS treated groups and control group. Real-time quantitative PCR was performed to detect the expression of VEGF mRNA in U2OS osteosarcoma cells. The VEGF protein level was determined using Western blotting and immunofluorescence cytochemistry. Cell proliferation ability was detected by CCK-8 assay. The tube formation assay in vitro was used to observe the angiogenesis ability. RESULTS: CTS inhibited the levels of VEGF mRNA and protein in a dose-dependent manner in U2OS osteosarcoma cells obviously. CCK-8 assay indicated that CTS inhibited the proliferation of U2OS osteosarcoma cells. The tube formation assay in vitro revealed that CTS inhibited the angiogenesis ability. CONCLUSION: CTS could down-regulate the expression of VEGF and inhibit angiogenesis in U2OS osteosarcoma cells.

Unraveling the novel anti-osteosarcoma function of coptisine and its mechanisms.

Uncontrolled cell proliferation and robust angiogenesis play critical roles in osteosarcoma growth and metastasis. In this study we explored novel agents derived from traditional Chinese medicinal herbs that potently inhibit osteosarcoma growth and metastasis. Coptisine, an active component of the herb Coptidis rhizoma, markedly inhibited aggressive osteosarcoma cell proliferation. Coptisine induced cell cycle arrest at the G0/G1 phase through downregulation of CDK4 and cyclin D1 expression and effectively suppressed tumor growth in a xenografted mouse model. Coptisine significantly impeded osteosarcoma cell migration, invasion, and capillary-like network formation by decreasing the expression of VE-cadherin and integrin ß3, and diminishing STAT3 phosphorylation. Coptisine significantly elevated blood erythrocyte and hemoglobin levels while still remaining within the normal range. It also moderately increased white blood cell and platelet counts. These data suggest that coptisine exerts a strong anti-osteosarcoma effect with very low toxicity and is a potential anti-osteosarcoma drug candidate.

The Combination of Sorafenib and Everolimus Abrogates mTORC1 and mTORC2 upregulation in osteosarcoma preclinical models.

PURPOSE: The multikinase inhibitor sorafenib displays antitumor activity in preclinical models of osteosarcoma. However, in sorafenib-treated patients with metastatic-relapsed osteosarcoma, disease stabilization and tumor shrinkage were short-lived and drug resistance occurred. We explored the sorafenib treatment escape mechanisms to overcome their drawbacks. EXPERIMENTAL DESIGN: Immunoprecipitation, Western blotting, and immunohistochemistry were used to analyze the mTOR pathway [mTOR complex 1 (mTORC1) and mTOR complex 2 (mTORC2)]. Cell viability, colony growth, and cell migration were evaluated in different osteosarcoma cell lines (MNNG-HOS, HOS, KHOS/NP, MG63, U-2OS, SJSA-1, and SAOS-2) after scalar dose treatment with sorafenib (10-0.625 µmol/L), rapamycin-analog everolimus (100-6.25 nmol/L), and combinations of the two. Cell cycle, reactive oxygen species (ROS) production, and apoptosis were assessed by flow cytometry. Nonobese diabetic/severe combined immunodeficient (NOD/SCID) mice injected with MNNG-HOS cells were used to determine antitumor and antimetastatic effects. Angiogenesis and vascularization were evaluated in vitro by exploiting endothelial branching morphogenesis assays and in vivo in xenografted mice and chorioallantoic membranes. RESULTS: After sorafenib treatment, mTORC1 signaling was reduced (downstream target P-S6), whereas mTORC2 was increased (phospho-mTOR Ser2481) in MNNG-HOS xenografts compared with vehicle-treated mice. Combining sorafenib with everolimus resulted in complete abrogation of both mTORC1 [through ROS-mediated AMP-activated kinase (AMPK) activation] and mTORC2 (through complex disassembly). The sorafenib/everolimus combination yielded: (i) enhanced antiproliferative and proapoptotic effects, (ii) impaired tumor growth, (iii) potentiated antiangiogenesis, and (iv) reduced migratory and metastatic potential. CONCLUSION: mTORC2 activation is an escape mechanism from sorafenib treatment. When sorafenib is combined with everolimus, its antitumor activity is increased by complete inhibition of the mTOR pathway in the preclinical setting.

Osteosarcoma cells induce endothelial cell proliferation during neo-angiogenesis.

Understanding the mechanisms inducing endothelial cell (EC) proliferation following tumor microenvironment stimuli may be important for the development of antiangiogenic therapies. Here, we show that cyclin-dependent kinase 2 and 5 (Cdk2, Cdk5) are important mediators of neoangiogenesis in in vitro and in vivo systems. Furthermore, we demonstrate that a specific Yin Yang 1 (YY1) protein-dependent signal from osteosarcoma (SaOS) cells determines proliferation of human aortic endothelial cells (HAECs). Following tumor cell stimuli, HAECs overexpress Cdk2 and Cdk5, display increased Cdk2 activity, undergo enhanced proliferation, and form capillary-like structures. Moreover, Roscovitine, an inhibitor of Cdks, blunted overexpression of Cdk2 and Cdk5 and Cdk2 activity induced by the YY1-dependent signal secreted by SaOS cells. Furthermore, Roscovitine decreased HAEC proliferation and angiogenesis (the latter by 70% in in vitro and 50% in in vivo systems; P < 0.01 vs. control). Finally, the finding that Roscovitine triggers apoptosis in SaOS cells as well as in HAECs by activating caspase-3/7 indicates multiple mechanisms for the potential antitumoral effect of Roscovitine. Present work suggests that Cdk2 and Cdk5 might be pharmacologically accessible targets for both antiangiogenic and antitumor therapy.

Antitumor and anti-angiogenesis effects of thymoquinone on osteosarcoma through the NF-κB pathway.

Thymoquinone (TQ), the predominant bioactive constituent derived from the medicinal spice Nigella sativa (also known as black cumin), has been applied for medical purposes for more than 2,000 years. Recent studies reported that thymoquinone exhibited inhibitory effects on the cell proliferation of several cancer cell lines. This study was performed to investigate the antitumor and anti-angiogenic effects of thymoquinone on osteosarcoma in vitro and in vivo. Our results showed that thymoquinone induced a higher percentage of growth inhibition and apoptosis in the human osteosarcoma cell line SaOS-2 compared to that of control, and thymoquinone significantly blocked human umbilical vein endothelial cell (HUVEC) tube formation in a dose-dependent manner. To investigate the possible mechanisms involved in these events, we performed electrophoretic mobility shift assay (EMSA) and western blot analysis, and found that thymoquinone significantly downregulated NF-κB DNA-binding activity, XIAP, survivin and VEGF in SaOS-2 cells. Moreover, the expression of cleaved caspase-3 and Smac were upregulated in SaOS-2 cells after treatment with thymoquinone. In addition to these in vitro results, we also found that thymoquinone inhibits tumor angiogenesis and tumor growth through suppressing NF-κB and its regulated molecules. Collectively, our results demonstrate that thymoquinone effectively inhibits tumor growth and angiogenesis both in vitro and in vivo. Moreover, inhibition of NF-κB and downstream effector molecules is a possible underlying mechanism of the antitumor and anti-angiogenic activity of thymoquinone in osteosarcoma.

Columbamine suppresses the proliferation and neovascularization of metastatic osteosarcoma U2OS cells with low cytotoxicity.

Osteosarcoma is one of the most common malignant bone tumors in children and adolescents. Although extensive efforts have been made in anti-osteosarcoma therapy in recent decades, there are no effective low-toxicity drugs for treating patients with metastatic osteosarcoma. Hence, potent anti-metastatic osteosarcoma drugs are highly desired. In this study, we explored novel small molecular anti-metastatic osteosarcoma agents and found that columbamine (COL), an active component of the herb Coptis chinensis, inhibited the proliferation and neovascularization of metastatic osteosarcoma U2OS cells. COL effectively suppressed U2OS cell proliferation in vitro with an IC(50) of 21.31±0.38µM, with low cytotoxicity. Mechanistic studies revealed that COL induces cell cycle arrest at the G2/M transition, which is associated with attenuating CDK6 gene expression and diminishing STAT3 phosphorylation. COL did not significantly promote U2OS cell apoptosis at any of the dosages tested. Additionally, COL inhibited U2OS cell-mediated neovascularization, which was accompanied by the down-regulation of matrix metalloproteinase (MMP) 2 expression and reduction of cell migration, adhesion, and invasion. Taken together, our data show that COL exerts anti-proliferative and anti-vasculogenic effects on metastatic human osteosarcoma U2OS cells with low toxicity. These results warrant further investigation of COL as a potential anti-osteosarcoma and anti-cancer drug.

Sorafenib blocks tumour growth, angiogenesis and metastatic potential in preclinical models of osteosarcoma through a mechanism potentially involving the inhibition of ERK1/2, MCL-1 and ezrin pathways.

BACKGROUND: Osteosarcoma (OS) is the most common primary bone tumour in children and young adults. Despite improved prognosis, metastatic or relapsed OS remains largely incurable and no significant improvement has been observed in the last 20 years. Therefore, the search for alternative agents in OS is mandatory. RESULTS: We investigated phospho-ERK 1/2, MCL-1, and phospho-Ezrin/Radixin/Moesin (P-ERM) as potential therapeutic targets in OS. Activation of these pathways was shown by immunohistochemistry in about 70% of cases and in all OS cell lines analyzed. Mutational analysis revealed no activating mutations in KRAS whereas BRAF gene was found to be mutated in 4/30 OS samples from patients. Based on these results we tested the multi-kinase inhibitor sorafenib (BAY 43-9006) in preclinical models of OS. Sorafenib inhibited OS cell line proliferation, induced apoptosis and downregulated P-ERK1/2, MCL-1, and P-ERM in a dose-dependent manner. The dephosphorylation of ERM was not due to ERK inhibition. The downregulation of MCL-1 led to an increase in apoptosis in OS cell lines. In chick embryo chorioallantoic membranes, OS supernatants induced angiogenesis, which was blocked by sorafenib and it was also shown that sorafenib reduced VEGF and MMP2 production. In addition, sorafenib treatment dramatically reduced tumour volume of OS xenografts and lung metastasis in SCID mice. CONCLUSION: In conclusion, ERK1/2, MCL-1 and ERM pathways are shown to be active in OS. Sorafenib is able to inhibit their signal transduction, both in vitro and in vivo, displaying anti-tumoural activity, anti-angiogenic effects, and reducing metastatic colony formation in lungs. These data support the testing of sorafenib as a potential therapeutic option in metastatic or relapsed OS patients unresponsive to standard treatments.

Deletion of Yin Yang 1 protein in osteosarcoma cells on cell invasion and CXCR4/angiogenesis and metastasis.

We know that the Yin Yang 1 protein (YY1) overexpression is positively and strongly correlated with the degree of malignancy of bone tumors. Therefore, we questioned whether we could influence cell invasiveness by deleting YY1 in human osteosarcoma cells (SaOs-2), as tested in Matrigel-coated filters and metastasis implantation of such osteosarcoma cells in vivo, by serial analysis with nuclear magnetic resonance. Moreover, we focused our work on the chemokine receptor CXCR4 and its inhibition by T22 antibody, as well as on systemic (direct in vivo assay) and computer-assisted imaging of angiogenesis-related metastasis. Results showed that cell invasiveness and metastasis implantation by wild-type SaOs-2 cells, as evaluated by histology and immunohistochemistry, are associated with up-regulation of CXCR4 expression, which in turn was significantly reduced by T22. In addition, deletion of YY1 (siRNAYY1-SaOs-2) induced a significant decrease of cell invasion and metastasis growth. This phenomenon was associated with decreased vascular endothelial growth factor (VEGF)/angiogenesis and a complex rearrangement of the gene expression profile as evaluated by microarray analysis. In conclusion, YY1 and VEGF/CXCR4 seem to intervene in the pathogenesis of the malignant phenotype of osteosarcoma by acting on cell invasiveness and metastasis growth.

Posttreatment histology and microcirculation status of osteogenic sarcoma after a neoadjuvant chemo- and radiotherapy in combination with local electromagnetic hyperthermia.

BACKGROUND: Many biological attributes of tumors (including regional blood flow and microcirculation) can deteriorate the homogeneity of heat distribution and temperature elevation during hyperthermia. We analyzed the connection between the microcirculation status of osteogenic sarcomas and the posttreatment histology after neoadjuvant chemotherapy, irradiation and local hyperthermia. PATIENTS AND METHODS: 62 patients with histologically verified osteosarcoma (35 men, 27 women, age 9-53, average 21 years) were enrolled in the retrospective pathohistological study. 61 patients were evaluable. In 72.6% of cases the tumor was localized in bones forming knee joints. All patients received neoadjuvant treatment [6 hyperthermias (60 min, 42-45 degrees C), daunorubicin 30-50 mg/m(2), 6 infusions, adriamycin or cisplatin 30 mg/m(2) for 3 days or once 90 mg/m(2) monochemotherapy before the hyperthermic procedure; subsequently gamma-therapy, 20-36 Gy] followed by surgery. From archives, a control group was formed of 20 therapy-naive tumors. Resected tumors were histologically examined for assessment of spontaneous and therapeutically induced alterations. For analysis of the functionality status of microcirculation on histological cuts, 40 tumors (without selection) were investigated: 10 controls and 10 cases each with minimal, subtotal and total posttreatment alterations. RESULTS: Chemotherapy and radiotherapy in combination with local hyperthermia induced a distinct damage to osteosarcoma. In 39.3 and 35.7% of cases there was subtotal and total devitalization of tumor parenchyma, respectively. Thrombosis of magistral and middle vessels, stasis in the microcirculation tree (collapse), damage to intimal vessels and endothelial cells, and necrotic alterations of the vessel walls appeared predominantly in central areas of tumors. Tumors with minimal devitalization of the parenchyma had a share of nonfunctional vessels ranging from 10.6 to 61.7%, mean 29.7%. In tumors with subtotal necrosis, between 34.5 and 72.0% (mean 49.46%) of vessels were nonfunctional (stasis, thrombosis). In 10 cases with 100% necrosis of the osteosarcoma parenchyma, a mean of 56.05% of nonfunctional vessels was registered (12.3-83.0%). In the control group, between 2.85 and 73.4% (mean 21.69%) of vessels showed damage to the microcirculation. CONCLUSION: There is a direct correlation between deterioration of the microcirculation in osteosarcoma and thermo-radiochemotherapy- induced tissue alteration; the devitalization grade is directly proportional to the number of nonfunctional vessels in the tumor.

Delay in administration of CDDP until completion of AGM-1470 treatment enhances antimetastatic and antitumor effects.

The efficacy of cis-diammine dichloroplatinum (CDDP) therapy in combination with continuous administration of angiogenesis inhibitor o-(chloroacetyl-carbamoyl) fumagillol (AGM-1470) was evaluated experimentally using a transplantable rat osteosarcoma line previously established in our laboratory. AGM-1470 (2.5 mg/kg body weight/week) was administered by Alzet osmotic pumps for 2 weeks starting from 7 days after tumor inplantation and CDDP (1.25 mg/kg) was given on days 21 and 24. The number of lung metastatic nodules was counted and the wet weights of the primary tumors were measured 5 weeks after tumor inplantation. Values with administration of CDDP 3 days after discontinuation of AGM-1470 were significantly lower than when the two agents were coadministered (P < 0.05). This animal model should facilitate optimization of the timing of combination therapy.

Efficacy of CDDP and AGM-1470 chemotherapy against lung metastasis in rat osteosarcoma depends on the timing of combined administration.

The efficacy of combination therapy with cis-diammine-dichloroplatinum (II) (CDDP) and o-(chloroacetyl-carbamoyl) fumagillol (AGM-1470) was evaluated experimentally using a transplantable rat osteosarcoma line, previously established in our laboratory, with a high potential for metastasis. Tumor-bearing male Fischer 344 rats were administered CDDP (2.5 mg/kg) together with, or after discontinuation of, AGM-1470 treatment (10 mg/kg/body weight/week). When CDDP was administered three days after discontinuation of AGM-1470 the most pronounced antimetastatic effects were observed, although the antitumor effect was approximately the same.

Suppression of pulmonary metastasis by angiogenesis inhibitor TNP-470 in murine osteosarcoma.

We treated a murine osteosarcoma cell line, LM8, which preferentially metastasizes to the lungs, with a new angiogenesis inhibitor, TNP-470, to evaluate the efficacy of this compound in the suppression of pulmonary metastasis of osteosarcoma. In an in vivo experiment, tumor cells were inoculated i.v. into C3H mice, and TNP-470 or vehicle alone (control group) was administered s.c. every day for 3 weeks. In the TNP-470-treated groups, both the number of pulmonary metastatic nodules and the lung wet weight were significantly reduced in a dose-dependent manner. Similarly, vascular density in the metastatic tumors estimated by immunohistochemical staining with anti-von-Willebrand factor antibody as an endothelial marker were significantly reduced. No severe side-effects were found. In an in vitro experiment, viable tumor cells were counted after 3 days' treatment with TNP-470. The 50% inhibitory concentration was 0.6 ng/ml for LM8, which was more sensitive than other tumor cells previously reported. Our results show that TNP-470 suppresses the pulmonary metastasis of LM8 and suggest that both its anti-angiogenic activity and cytostatic activity towards LM8 are responsible for the antitumor effect.