Effects Of SDF-1/CXCR4 Axis On Progression Of Glioma And Its Mechanism

Tumor microenvironment plays an important role in the proliferation and migration of tumor cells. A host of extracellular signaling molecules like stromal derived factor-1(SDF-1) is able to activate varies kinds of tumor cells to affect proliferation and migration. Thus to investigate the mechanism involved in microenvironment of glioma is urgent. In the present study, we choose high grade glioma, glioblastoma cell line, U87-MG to investigate the potential effects and the involved mechanism of SDF-1/CXCR4 axis in the tumor progreesion. Specific small double-stranded interfering RNA (siRNA) was used to downregulate the gene expression of CXCR4. Then expession of CXCR4 were detected at mRNA level by reverse transcription polymerase chain reaction(RT-PCR) and localization by indirect immunofluorescene staining. Transwell assay was performd to investigate the ability of migarion at different CXCR4 level.The results suggest that siRNA could significantly reduce the expression of CXCR4. Futhermore, the CXCR4 expression has tight relationship with the migration of U87 cells.This part was to study the protective effect injuried by hydrogen peroxide (H₂O₂) and the effects on Ca²⁺ homeostasis after activation of chemokine receptor CXCR4 in human glioma cell line U87. Cells were divided into three groups: control group, H₂O₂ (0.7 mM) treated group, SDF-1α+H₂O₂ treated group (100 ng/ml and 0.7 mM respectively). Apoptotic cells were measured by flow cytometry. Western Blot was used to detect the expression of phosphorylated protein kinase B (pAkt) and phosphorylated extracellular signal regulating kinase (pERK1/2). Confocal laser scanning microscope was used to measure the changes of Ca²⁺ of cells after actication of CXCR4 by SDF-1.The results suggest that activation of CXCR4 could protect U87 cells from H₂O₂-induced apoptosis, the mechanism may be link to the activation of phosphatidylinositol 3-kinase (PI3K) -Akt and mitogen-activated protein kinase (MAPK) -ERK1/2 signalling pathway. In additon, SDF-1 induced cytoplasmic Ca²⁺ increasing was depended on both intracellular and extracellular way,Further results revealed that IP3Rs, nifedipine-sensitive Ca²⁺ channel as well as CXCR4 were involved in SDF-1 induced increment of Ca²⁺ in U87 cells..