Aromatic Hydrocarbon Receptor Suppresses Prostate Cancer Bone Metastasis Cells-Induced Vasculogenesis of Endothelial Progenitor Cells under Hypoxia.

BACKGROUND/AIMS: Hypoxia leads to the development of neovascularization in solid tumor by regulating VEGF expression. Aromatic hydrocarbon receptor (AHR), a receptor for dioxin-like compounds, functions as a transcription factor through dimerization with hypoxia-inducible factors 1ß (HIF-1ß) and inhibits the secretion of vascular endothelial growth factor (VEGF). The purpose of this study was to explore whether AHR can suppress hypoxia-induced VEGF production in prostate bone metastasis cells and repress neovascularization in endothelial progenitor cells (EPCs), and, if so, through what mechanisms. METHODS: PC-3 or LNCaP cells induced angiogenesis was detected by Matrigel-based tube formation assay, mRNA expression levels was measured by qRT-PCR, VEGF secretion level was determined by ELISA assay, respectively. RESULTS: AHR activation inhibits hypoxia-induced adhesiveness and vasculogenesis of EPCs induced by PC-3 or LNCaP cells under hypoxia. Moreover, AHR activation suppressed hypoxia-induced VEGF production in PC-3 and LNCaP cells (48 ± 14% in PC-3, p = 0.000; 41 ± 14% in LNCaP, p = 0.000) by attenuating HIF-1α and HIF-1ß level that in turn diminished the angiogenic ability of EPCs in vitro. Furthermore, we found the mRNA level of hypoxia-inducible factors 1α (HIF-1α) (1.54 ± 0.13 fold in PC-3, p = 0.002, 1.62 ± 0.12 fold in LNCaP, p = 0.001) and HIF-1ß (1.67 ± 0.23 fold in PC-3, p = 0.007; 1.75 ± 0.26 fold in LNCaP, p=0.008) were upregulated in prostate cancer bone metastasis PC-3 and LNCaP cell lines in response to hypoxia, and revealed that the regulation of VEGF by HIF-1α and HIF-1ß was possibly mediated by the activation of phosphatidylinositol 3-kinase pathway. CONCLUSION: By providing a mechanistic insight into the modulation of neovascularization by AHR ligand, we suggest that AHR ligand has a strong potential of being a new therapeutic agent with applications in the field of bone metastatic prostate cancer.

Celastrol inhibits vasculogenesis by suppressing the VEGF-induced functional activity of bone marrow-derived endothelial progenitor cells.

Bone marrow (BM)-derived endothelial progenitor cells (EPCs) play a critical role in tumor vasculogenesis because they provide both instructive (release of pro-angiogenic cytokines, such as VEGF) and structural (vessel incorporation and stabilization) functions. Celastrol, derived from Trypterygium wilfordii Hook F., a traditional Chinese medicine plant, has been studied for its antitumorigenic properties, but its mechanism of action is not well understood. The aims of this study are to investigate the effects of Celastrol on VEGF-induced functional activity of BM-EPCs and to identify any mechanisms associated with this process. Here, we show that Celastrol attenuates VEGF secretion in BM-EPCs in vitro. This attenuation, in turn, inhibits the in vitro VEGF-induced cell viability, cell-cell adhesion, cell-ECM adhesion, migration response and vascular tube formation of BM-EPCs. Additionally, Celastrol inhibits the phosphorylation of VEGFR2, endothelial nitric oxide synthase (eNOS), and Akt to attenuate cell functions. Taken together, the present study demonstrates that Celastrol decreases Akt/eNOS signaling in BM-EPCs in vitro. These findings identify novel mechanisms that regulate EPC function and may provide new insights for the medicinal use of Celastrol.

Disabled homolog 2 interactive protein functions as a tumor suppressor in osteosarcoma cells.

The disabled homolog 2 interactive protein (DAB2IP) gene is a member of the family of Ras GTPases and functions as a tumor suppressor in many types of carcinoma; however, its function in osteosarcoma remains unclear. The aim of the present study was to determine the function of DAB2IP in osteosarcoma and normal bone cells in vitro. The expression of DAB2IP protein was assessed in osteoblast and osteosarcoma cell lines by western blot analysis. The effects of DAB2IP expression on cell proliferation, colony formation, apoptosis, cell cycle, and cell migration and invasion were evaluated by in vitro studies. DAB2IP expression was lower in osteosarcoma cell lines than in normal osteoblast cell lines. DAB2IP expression affected cell proliferation, apoptosis and cell cycle distribution. In addition, DAB2IP inhibited the migration and invasion of osteosarcoma and normal osteoblast cells. Therefore, DAB2IP may function as a tumor suppressor in osteosarcoma cell lines by inhibiting cell proliferation and invasion.

Biomechanical analysis of a newly developed shape memory alloy hook in a transforaminal lumbar interbody fusion (TLIF) in vitro model.

OBJECTIVE: The objective of this biomechanical study was to evaluate the stability provided by a newly developed shape memory alloy hook (SMAH) in a cadaveric transforaminal lumbar interbody fusion (TLIF) model. METHODS: Six human cadaveric spines (L1-S2) were tested in an in vitro flexibility experiment by applying pure moments of ±8 Nm in flexion/extension, left/right lateral bending, and left/right axial rotation. After intact testing, a TLIF was performed at L4-5. Each specimen was tested for the following constructs: unilateral SMAH (USMAH); bilateral SMAH (BSMAH); unilateral pedicle screws and rods (UPS); and bilateral pedicle screws and rods (BPS). The L3-L4, L4-L5, and L5-S1 range of motion (ROM) were recorded by a Motion Analysis System. RESULTS: Compared to the other constructs, the BPS provided the most stability. The UPS significantly reduced the ROM in extension/flexion and lateral bending; the BSMAH significantly reduced the ROM in extension/flexion, lateral bending, and axial rotation; and the USMAH significantly reduced the ROM in flexion and left lateral bending compared with the intact spine (p<0.05). The USMAH slightly reduced the ROM in extension, right lateral bending and axial rotation (p>0.05). Stability provided by the USMAH compared with the UPS was not significantly different. ROMs of adjacent segments increased in all fixed constructs (p>0.05). CONCLUSIONS: Bilateral SMAH fixation can achieve immediate stability after L4-5 TLIF in vitro. Further studies are required to determine whether the SMAH can achieve fusion in vivo and alleviate adjacent segment degeneration.