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G-protein-coupled formylpeptide receptor (FPR) has recently been found to be functionally expressed in gliomas and are probably involved in their malignant biological behavior. In an attempt to explore the therapeutic significance of FPRs, we used wild-type human glioblastoma cells (U87), the corresponding FPR short-interfering RNA transfected (siRNA U87) cells, and mock-transfected U87 cells (mock U87) to establish xenografts in mice brains. Compared to wild-type and mock transfected cells, siRNA U87 cells formed smaller and more well-differentiated xenografts with fewer mitotic figures and more glial filaments within their cytoplasm. The density of microvessels, which presented as a nearly normal morphous, was also decreased significantly in FPR knockdown cells. Moreover, fewer invasive foci could be observed in the xenografts derived from siRNA U87 cells, which also showed a poor migratory capacity in vitro. We suggest that decreased VEGF and MMP-2/-9 expression might be a possible mechanism for the decreasing angiogenic potential and invasive capability of U87 cells after FPR knockdown. Functional FPR might be essential for sustaining the growth and aggressive phenotype of gliomas, and could therefore be a potential therapeutic target.

Activation of the formylpeptide receptor (FPR), a G-protein-coupled receptor, by its chemotactic peptide ligand N-formylmethionyl-leucyl-phenylalanine (fMLF) promotes the directional migration and survival of human glioblastoma cells. fMLF also stimulates glioblastoma cells to produce biologically active VEGF, an important angiogenic factor involved in tumor progression. In this study, we examined the capacity of FPR to regulate the production of another angiogenic factor, the chemokine IL-8 (CXCL8), in addition to its demonstrated ability to induce VEGF secretion by malignant glioma cells. We showed that the human glioblastoma cell line U87 secreted considerable levels of IL-8 (CXCL8) upon stimulation by the FPR agonist peptide fMLF. Tumor cells transfected with small interference (si)RNA targeting FPR failed to produce IL-8 as well as VEGF in response to fMLF. Glioblastoma cells bearing FPR siRNA exhibited reduced rate of tumorigenicity in nude mice and tumors formed by such tumor cells showed less active angiogenesis and lower level expression of both IL-8 and VEGF. These results suggest that FPR plays an important role in the angiogenesis of human malignant gliomas through increasing the production of angiogenic factors by FPR positive tumor cells.

Background & Objective: Chemoattractant receptors participate in essential pathophysiologic processes, including inflammation, wound healing, human immunodeficiency virus infection, and most interestingly in the progression of malignant tumor. This study was to explore the functional expression of formylpeptide receptor (FPR) in human glioblastoma cell line U87., Methods: The expression of FPR in U87 and FPR small interfering RNA (siRNA)-transfected U87 cells (FPR-siRNA-U87 cells) was detected with indirect immunofluorescent staining by confocal laser scanning microscopy. FPR was activated by its ligand formy-Met-Leu-Phe (fMLF). Cell proliferation was assessed by MTT assay. The production of vascular endothelial growth factor (VEGF) and interleukin-8 (IL-8) was measured by ELISA, and IL-8 mRNA was assessed by reverse transcription-polymerase chain reaction (RT-PCR)., Results: FPR was expressed on U87 cells, but not on FPR-siRNA-U87 cells. After activation of FPR by fMLF, the proliferation of U87 cells was enhanced markedly (P<0.05), but that of FPR-siRNA-U87 cells had no obvious change (P>0.05). fMLF (100 nmol/L) elicited a time-dependent increase in the secretion of IL-8 and VEGF. When stimulated with 100 nmol/L fMLF for 36 h, the protein levels of VEGF and IL-8 were significantly higher in stimulated U87 cells than in control cells [(3.13+/-0.23) ng/ml vs. (2.55+/-0.25) ng/ml, P<0.05û (7.54+/-0.53) ng/ml vs. (4.02+/-0.09) ng/ml, P<0.05], but those in FPR-siRNA-U87 cells had no obvious change; the mRNA level of IL-8 was significantly increased in U87 cells, but not changed in FPR-siRNA-U87 cells., Conclusion: Activating FPR can promote the proliferation of U87 cells and enhance the production of angiogenic factors.

Nordy is a synthesized chrial compound. To investigate the effects of nordy (25 - 100 micromol x L(-1)) on the function of formylpeptide receptor (FPR) of malignant human glioma cells, human glioblastoma cell line U87 was used to detect its proliferation, migration, calcium mobilization, vascular endothelial growth factor (VEGF) mRNA and protein levels after activation of FPR by its agonist N-formyl-methionyl-leucyl-phenylalanine (fMLF). Cell proliferation, migration ability, VEGF mRNA, VEGF protein and calcium mobilization were evaluated by cell counting, chemotaxis assay, RT-PCR, ELISA and spectrometry. Nordy (50 - 100 micromol x L(-1)) potently inhibited the proliferation, migration and calcium mobilization of U87 cells induced by fMLF (P < 0.05). Moreover, 100 micromol x L(-1) nordy showed a significantly impaired VEGF mRNA expression and protein secretion induced by fMLF (P < 0.05). Nordy could inhibit FPR functioning in glioma cell proliferation, migration and angiogenesis, which might be a possible mechanism of its anti-cancer effects.

Objective: To explore the effect of Nordy, a synthesized lipoxygenase Inhibitor, on the expression of formylpeptide receptor (FPR) and its functional activities after activation in human malignant glioma cells., Methods: Human malignant glioma cells of the line U87 were cultured and divided into 3 groups: N-formyl-methionyl-leucyl-phenylalanine (fMLF) group, added with 100 nmol/L fMLF; Nordy group, added with 100 micromol/L Nordy for 12 h and then added with 100 nmol/L fMLF; and control group. The expression of FPR I the U87 cells was detected with indirect immunofluorescence staining and confocal laser scanning microscopy. The effect of Nordy on the U87 cell proliferation induced by fMLF was assayed by MTT method. RT-PCR was used to detect the mRNA expression of vascular endothelial growth factor (VEGF) and interleukin-8 (IL-8) in the U87 cells. ELISA was used to detect protein secretion of VEGF and IL-8 in the supernatant., Results: FPR was expressed on the cytoplasmic membrane of U87 cells. The mean FPR absorbance of the Nordy group was significantly lower than that of the fMLF group. The U87 cell proliferation of the Nordy group was significantly inhibited in comparison with the other 2 groups. The mRNA expression of VEGF and mRNA expression of IL-8 in the U87 cells activated by fMLF were significantly higher than those of the control group (both P<0.05), and Nordy significantly attenuated the mRNA expression of VEGF and IL-8 at different time points (all P<0.05). ELISA showed that the VEGF and IL-8 protein levels in the supernatant were 4.14 ng/ml+/-0.28 ng/ml and 4.03 ng/ml+/-0.59 ng/ml respectively, and increased to 6.46 ng/ml+/-0.33 ng/ml and 7.54 ng/ml+/-0.73 ng/ml respectively after stimulation of fMLF, however, the VEGF and IL-8 protein levels in the supernatant of the Nordy group were 3.59 ng/ml+/-0.33 ng/ml and 3.13 ng/ml+/-0.48 ng/ml respectively., Conclusion: Nordy inhibits the FPR expression and the effects in promoting the cell proliferation and mRNA expression and protein secretion of VEGF and IL-8 after the activation of FPR in malignant human glioma cells, showing that Nordy has the effects of inhibition of tumor growth and angiogenesis.

We recently found that formylpeptide receptor (FPR), a G-protein-coupled receptor that mediates chemotaxis of phagocytic leukocytes induced by bacterial peptide N-formyl-methionyl-leucyl-phenylalanine, is expressed by malignant human glioma cells and promotes tumor growth and angiogenesis. In this study, we examined the effect of Nordy, a novel chiral lipoxygenase inhibitor which was synthesized based on the structure of a natural nordihydroguaiaretic acid, on the expression of FPR by human glioblastoma cells. We found that FPR was expressed at the protein level by highly malignant human glioma cell lines U87 and BT325, and a rat glioma cell line C6. The expression level of FPR was correlated with the degree of the malignancy of tumor cells. The poorly differentiated glioma cell line U87 expressed the highest level of FPR. In U87 glioma cells, the expression of FPR was attenuated at the protein level by Nordy treatment for 48 (P<0.05). Nordy did not affect FPR mRNA expression in U87 cells. In addition, Nordy treatment seemed to promote glioma cell differentiation, as evidenced by their reduced expression of vimentin and increased expression of GFAP. Our results suggest that Nordy was capable of reducing the level of malignancy of glioma cells.