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Chemokines and their receptors are actively involved in inflammation, immune responses, and cancer development. Here we report the detection of CD133(+) glioma stem-like cells (GSCs) co-expressing a chemokine receptor CXCR4 in human primary glioma tissues. These GSCs were located in areas adjacent to tumour vascular capillaries, suggesting an association between GSCs and tumour angiogenesis. To test this hypothesis, we isolated CD133(+) GSCs from surgical specimens of human primary gliomas and glioma cell lines. As compared to CD133(-) cells, CD133(+) GSCs expressed significantly higher levels of CXCR4 mRNA and protein, and migrated more efficiently in response to the CXCR4 ligand CXCL12. In addition, CXCL12 induced vascular endothelial growth factor (VEGF) production by CD133(+) GSCs via activation of the PI3K/AKT signalling pathway. Furthermore, knocking down of CXCR4 using RNA interference or inhibition of CXCR4 function by an antagonist AMD3100 not only reduced VEGF production by CD133(+) GSCs in vitro, but also attenuated the growth and angiogenesis of tumour xenografts in vivo formed by CD133(+) GSCs in SCID mice. These results indicate that CXCL12 and its receptor CXCR4 promote GSC-initiated glioma growth and angiogenesis by stimulating VEGF production., (Copyright © 2011 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.)

Objective: CXCR4 is implicated in the growth, metastasis, and angiogenesis of malignant tumors. We investigated the potential role of CXCR4 in human gliomas., Methods: The expression of CXCR4 messenger ribonucleic acid and protein by human glioma cell lines was examined by reverse-transcriptase polymerase chain reaction and immunocytochemistry analysis. Tumor cell chemotaxis and production of vascular endothelial growth factor induced by the CXCR4 ligand SDF-1beta were measured. Xenograft models were used for evaluation of glioma cell tumorigenesis. CXCR4 expression by xenografted tumors and primary human glioma specimens were evaluated for CXCR4 protein expression. The relationship between CXCR4 expression and patient survival was analyzed. A synthetic lipoxygenase inhibitor, Nordy, was tested for its effects on glioma cell expression and function of CXCR4, as well as on glioma cell tumorigenicity., Results: CXCR4 expression correlated directly with the degree of malignancy of the human glioma cell lines and primary tumors. Activation of CXCR4 induced tumor cell chemotaxis and increased production of vascular endothelial growth factor. Glioma cells expressing higher levels of CXCR4 formed more rapidly growing and lethal tumors in nude mice. Primary human glioma specimens expressing CXCR4 contained high-density microvessels. Patients with CXCR4-positive gliomas had poorer prognosis after surgery. The lipoxygenase inhibitor Nordy diminished CXCR4 expression by glioma cell lines in vitro and reduced their tumorigenicity in nude mice., Conclusion: The level of CXCR4 expression seems to correlate with the degree of malignancy of human gliomas and may contribute to their rapid growth.

The chemokine receptor CXCR4 plays an important role in tumor growth, angiogenesis and metastasis. Our previous studies showed that Nordy, a synthetic chiral compound of nordihydroguaiaretic acid, inhibited the growth and angiogenesis of various malignant tumors. In this study we examined the capacity of Nordy to regulate CXCR4-mediated production of angiogenic factors by human glioblastoma cells. We found that Nordy potently inhibited CXCR4 ligand SDF-1-induced production of IL-8 and vascular endothelial cell growth factor, two important angiogenic factors implicated in the progression of malignant tumors. Further study revealed that the effect of Nordy was attributable to its down-regulation of the expression of functional CXCR4 in glioblastoma cells. These results suggest that the anti-cancer activity of Nordy is due, at least in part, to its suppression of the chemokine receptor CXCR4 thus reducing the production of angiogenic factors by tumor cells.

Objective: To isolate, culture and identify glioma stem cells from human malignant glioma cell line U87, and investigate the changes of pro-angiogenic factors production by glioma stem cells followed by activation of CXCR4 and observe their tumorigenesis as well as the expression of vascular endothelial growth factor when implanted into nude mice., Methods: The ratio of CD133 positive cells was detected by flow cytometry. Magnetic separation of CD133 positive cells was carried out on the magnetic cell sorting system (MACS). Expression of nestin, glial fibrillary acidic protein (GFAP) and CXCR4 on tumorspheres was detected by indirect immunofluorescence under confocal laser scanning microscopy. The functional activation of CXCR4 was assessed by calcium mobilization experiments. ELISA was used to detect the production of vascular endothelial growth factor (VEGF) and interleukin-8 (IL-8) in conditioned medium. Glioma stem cells were implanted into nude mice to assess their tumorigenesis ability and the expression of VEGF., Results: The ratio of CD133 positive cells with stem cell property was 0.5% in U87 cells. Activation of CXCR4 on glioma stem cells induced calcium mobilization and increased VEGF and IL-8 protein secretion. CD133 positive cells secreted more VEGF and IL-8 than their negative counterparts in vitro. Tumors derived from CD133 positive cells grew more rapidly and expressed elevated level of VEGF than their negative counterparts., Conclusions: There are a small fraction of glioma stem cells in human glioblastoma cell line U87. Expressing functional CXCR4 and secreting more pro-angiogenic factors may be involved in tumor angiogenesis mediated by glioma stem cells.

Numerous studies have showed that chemokine receptors, such as CXCR4, contribute to the growth and metastasis of a variety of malignant tumors. In this study, we investigated the role of CXCR4 in the production of angiogenic factor, vascular endothelial growth factor (VEGF), in various human glioma cells from astrocytic origin. The expression of CXCR4 mRNA and protein in three glioma cell lines, U87-MG, SHG-44, and CHG-5, was determined by RT-PCR and immunocytochemistry, respectively. The malignancies of three gliomas were evaluated by expression of glial fibrillary acidic protein and vimentin, the differentiation markers of astrocytic cells. The role of functional CXCR4 in tumor cell migration was studied with chemotaxis assay. Ca2+ mobilization and VEGF production were measured in the cells after stimulation with CXCR4 ligand, SDF1beta. The results showed that the levels of functional CXCR4 expression at both mRNA and protein levels by several human glioma cell lines were correlated with the degree of differentiation of the tumor cells. Activation of CXCR4 induced glioma cell chemotaxis and could trigger the increase of intracellular [Ca2+]i. Such an activation could result in the increased production of VEGF by the stimulated tumor cells. Our results suggest that CXCR4 may contribute to the high level of VEGF produced by malignant glioma cells and thus constitute a therapeutic target for antiangiogenesis strategy.