| The annual incidence of malignant gliomas is approximately 5 cases per 100,000 people. Glioblastomas account for approximately 60 to 70% of malignant gliomas, anaplastic astrocytomas for 10 to 15%, and anaplastic oligodendrogliomas and anaplastic oligoastrocytomas for 10%. Malignant gliomas are associated with disproportionately high morbidity and mortality. Despite optimal treatment, the median survival is only 12 to 15 months for patients with glioblastomas and 2 to 5 years for patients with anaplastic gliomas.So it is very important to implore the molecular pathogenesis of malignant gliomas and to find new approach to treate them.Angiogenesis is recognized as a key event in the natural progression of gliomas of all solid tumors, those of the brain show the highest degree of vascular proliferation. Newly formed brain tumor blood vessels possess a defective bloodbrain barrier that contributes to the pathogenesis of tumor-associated edema. They are associated with increased risk of intratumoral hemorrhageand are responsible for contrast enhancementGlioma cells and their microenvironment may communicate to sustain an appropriate microenvironment to support tumorigenesis, angiogenesis, and metastasis. Survivin promotes tumorigenesis and inhibits apoptosis of cancer cells suggesting its crucial role in progression of carcinoma. As Survivin is strongly expressed in various human caners, but is poorly expressed in most adult terminally differentiated normal tissues, Survivin-targeted therapy is going to be a novel strategy for cancer treatment. We have previously demonstrated that Survivin level is positively correlated to the grade of glioma and knockdown of Survivin can inhibit tumor growth and reduces the microvessel density of malignant glioma xenograft in nude mice. But it is yet to be determined whether the halt of angiogenesis is mainly mediated by Survivin deprivation. Thus, further investigation should be initialized to verify the relationship between Survivin in glioma cells and angiogenesis in surrounding microenvironment.Tumor angiogenesis may be dominated by proangiogenic cytokines secreted by tumor cells; however, the potential role of Survivin in glioma cells to regulate the phenotype of angiogenesis-relating cells has not been reported. Egr-1, an important transcriptional factor, functions as an activator of angiogenesis through regulating expression of VEGF, bFGF and PDGF. Egr-1 can be upregulated in islets with forced expression of wild-type Survivin. Hence it is worth to determine whether secretion of proangiogenic cytokines in glioma cells induced by Survivin is mediated through Egr-1.Objective: To verify the relationship between Survivin in glioma cells and angiogenesis in surrounding microenvironment.Methods: Survivin shRNA and Egr-1 shRNA plasmids were transfected in to U251 cells. Survivin, Egr-1, and Survivin-Egr-1 shRNA (a plasmid containing Survivin coding sequence and Egr-1 shRNA) were transfected into SHG44 cells. The effect of Survivin in glioma cells on the proliferation and migration of ECs were evaluated by MTT assay, transwell chamber assay and tube formation assay in vitro. Meanwhile, transcription and protein expression level of vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF) and platelet-derived growth factor (PDGF) in glioma cells were detected by qPCR and Western blot; and the level of VEGF, bFGF and PDGF in supernatant was detected by ELISA. In vivo, the tumorgenesity of corresponding glioma cells were measured by tumor size and weight and the expression of VEGF, bFGF, PDGF, Ki67, Survivin and Egr-1 in tumor tissues was detected by immunohistochemistry staining.Results: Survivin in human glioma cells could significantly promote ECs'proliferation and migration in vitro. Angiogenesis related cytokines (VEGF, bFGF and PDGF) were positively correlated with Survivin expression level both in vivo and in vitro, which could be abrogated by the knockdown of Egr-1.Conclusion: We demonstrated for the first time Survivin in glioma cells could enhance the angiogenesis by upregulating the expression of VEGF, bFGF and PDGF both in vitro and in vivo. Furthermore, such effect could be abrogated by the knockdown of Egr-1. Therefore, Egr-1 could be involved in the Survivin induced angiogenesis in human glioma cells.
|
PDF Full Text Request