Mechamism Of Antiglioma Activity Of F2 Isolated From Grape Seeds Related To Formyl Peptide Receptor

Glioblastoma is the most common and lethal tumor type in the brain.Formyl peptide receptor 1(FPR1).is a new molecular target for glioma therapeutics,which has been shown to play important roles in glioma cells invasion,proliferation and angiogenesis.Thus,we established a drug screening platform taking FPR1 as a target and finally discovered the target compound F2 through a wide screening.The oligomer procyanidins(F2)(F2,degree of polymerization 2-15)is a natural fraction isolated from grape seeds.We found that F2 selectively inhibited U-87 cell chemotaxis,calcium mobilization and MAP kinases ERK1/2 phosphorylation mediated by FPR1.Based on the previous finding,we further explored the relationship and molecular mechanisms of F2 involved in FPR1 function.Firstly,we investigated the capacity of F2 to interact with FPR.Cross-attenuation of chemotaxis revealed that F2 shared FPR1 with formyl-methionyl-leucyl-phenylalanine(fMLF),which is a prototype agonist of FPR1.F2 was chemotactic for U-87 cells and the chemotactic response was abolished when FPR1 gene was silenced or FPR1 was competitively occupied.We further showed that F2 specifically blocked the binding of fluorescent agonist to FPR1.Interestingly,F2 exhibited the characteristic of a partial agonist for FPR1,as shown by its capacity to activate FPR1-mediated PI3K-PKC-MAPK pathways.Meanwhile,F2 also attenuated fMLF-triggered MAPK activation,suggesting that F2 could antagonize the effect of an agonist.Furthermore,F2 abolished the invasion of U-87 cells induced by fMLF.Thus,we have identified F2 as a novel,partial agonist for FPR1.In addition,we found that F2 selectively inhibited FPR1-enhanced transactivation of the Epidermal Growth Factor Receptor(EGFR)and FPR1-mediated PI3K/AKT pathway activation,subsequently decreasing their downstream protein Bcl-2/Bax,hypoxia inducible factor-1?(HIF-1?)and vascular endothelial growth factor(VEGF)expression.As a result,F2 could inhibit formation of Capillary-Like structures and invasion of endothelial cells induced by culture supernatants from U-87 cells treated with fMLF.Further,administration of 50 mg/kg and 200 mg/kg body weight of mice by oral gavage(7 d/week)markedly inhibited tumor growth and tumor angiogenesis of U-87 glioma cancer cells in nude mice,which was associated with the induction of decreased expression of Bcl-2/Bax and VEGF in tumor xenograft cells.In conclusion,these results indicated that F2 may be a novel natural FPR inhibitor and could potentially be useful in antiglioma therapeutics.