| Glioblastoma multiforme is the most malignant intracranial glioma. Despite the treatments of surgery, radiation, and chemotherapy, we can’t prevent the recurrence of tumor and significantly improve the prognosis.Invasive nature of malignant glioma is a major of factors causing therapeutic failure. The invasion of tumor cells to adjacent parenchyma is a complex process.Chemokine CXCL12, also called stromal cell-derived factor1(SDF1), and its receptor CXCR4were both expressed in glioma, and CXCL12and CXCR4expression elevated with increasing tumor grade. Some studies have reported that CXCL12/CXCR4participated in glioma cell invasion and migration, but the mechanism is not clear yet. We intended to detect the expression of CXCL12and CXCR4in glioblastoma microenviroment, and investigated their role in invasion and migration. The present study included two parts:1. The characteristics of CXCL12vs CXCR4expression and distribution in glioblastoma microenviroment. Forty-five tumor specimens were collected from patients with newly diagnosed glioblastoma (according to WHO CNS tumor classification in2007) from September,2009to June,2012in Department of Neurosurgery of Tianjin Medical University General Hospital, while5control brain tissues were collected from patients undergoing medial temporal lobe epilepsy surgery. Multiple specimens were obtained under assistance of neuronavigation system during the operation including specimens from central tumor tissue and from border zone between tumor and peri-tumor edema and from peritumoral edematous white matter. Immunohistochemistry was employed to detect the expression of CXCL12, CXCR4and MMP-9in tissue specimens. In tumor core, CXCL12was expressed in vascular endothelial cells and cells around necrosis, CXCR4was expressed in cells around vessel and necrosis, MMP-9was expressed in cells around necrosis. In junctional zones, CXCL12was expressed in proliferative vascular endothelial cells, CXCR4was expressed in cells around proliferative vessel, MMP-9was expressed in proliferative vessel areas. In peritumoral edematous areas, CXCL12, CXCR4and MMP-9were sporadically expressed. CXCL12was weakly positive and CXCR4was negative. The expression level of CXCL12, CXCR4and MMP-9demonstrated weakening trend from tumor core to peritumoral edematous areas. The expression of CXCL12/CXCR4and MMP-9was positively correlated (CXCL12and MMP-9, r=0.769, P＜0.05; CXCR4and MMP-9, r=0.948, P＜0.05).2.The role of CXCL12/CXCR4in invasion and migration of glioma.We chose three malignant glioma cell lines U251, LN229and SNB19, and observed the chemotaxis of HUVEC cultural supernatant to glioma cells, the number of migratory cells in AMD3100groups was fewer than that in HUVEC groups, the difference was significant (P<0.05).Three cell lines were treated with CXCL12and AMD3100respectively. The expression of MMP-9in treated and control cells were detected by RT-PCR and Western blot. The MMP-9mRNA expression value of control groups in U251was0.294±0.042, the value of CXCL12group was0.968±0.065, the value of AMD3100groups was0.187±0.028. The MMP-9protein expression value of control groups in U251was0.449±0.026, the value of CXCL12groups was0.605±0.011, the value of AMD3100groups was0.358±0.009. The MMP-9mRNA expression value of control groups in LN229was0.265±0.032, the value of CXCL12groups was0.853±0.054, the value of AMD3100groups was0.107±0.024. The MMP-9protein expression value of control groups in LN229was0.445±0.022, the value of CXCL12groups was0.771±0.020, the value of AMD3100groups was0.324±0.021. The MMP-9mRNA expression value of control groups in SNB19was0.279±0.039, the value of CXCL12groups was0.902±0.057, the value of AMD3100groups was0.124±0.031; The MMP-9protein expression value of control groups in SNB19was0.425±0.024, the value of CXCL12groups was0.625±0.019,the value of AMD3100groups was0.368±0.021. The same MMP-9expression trend was found, that was CXCL12groups> control groups>AMD3100groups, the difference was significant (P＜0.05).Phalloidine immunofluorescence was used to detect the actin reorganization in different groups. We found that actin was polymerizated filamentously in CXCL12groups, but not in AMD3100groups.Conclusion:1. CXCL12and CXCR4were expressed in the microenviroment of tumor mass, junctional zones between tumor and peritumoral areas and peritumoral edematous areas, and the level of them reduced gradually from mass to peritumoral edematous areas.2.The assembly of tumor cells around vessel was mediated by CXCL12/CXCR4in glioblastoma microenviroment, explaining that malignant glioma migrated along basement membrane.3. CXCL12/CXCR4might promote the invasion of malignant glioma cells via the upregulated MMP-9expression.4. CXCL12/CXCR4might enhance the migration of malignant glioma cells via the elevated filamentous polymerization of actin. CXCR4could be a potential target against the invasion and migration of glioma. |
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