ANNEXIN A2 REGULATES ANGIOGENESIS AND INVASION PHENOTYPES OF MALIGNANT GLIOMA

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Abstract

BACKGROUND: Despite advances in multimodal therapy, patients with malignant glioma have a dismal prognosis. Aberrant angiogenesis and diffuse glioma cell invasion are major obstacles for effective treatment. Therefore, investigation of angiogenesis and invasion is essential for the development of a curative therapy. We established animal models that histologically mimic two invasive and angiogenic phenotypes of glioma, ie, angiogenesis-dependent invasion (J3T-1) and angiogenesis-independent invasion (J3T-2). In our previous study, comparative proteomic analysis showed that annexin A2 was more highly expressed in J3T-1 than in J3T-2. In this study, the function of annexin A2 in malignant glioma in relation to angiogenesis and invasion was investigated using these animal models. METHODS: Annexin A2-downregulated J3T-1 cells (J3T-1shA) and annexin A2-upregulated J3T-2 cells (J3T-2A) were generated by gene transfection. Quantitative reverse transcription polymerase chain reaction (QRT-PCR) and immunohistochemical staining of annexin A2 and vascular endothelial growth factor (VEGF) were performed on cultured cells. J3T-1, J3T-1shA, J3T-2, and J3T-2A brain tumors were established in athymic rats. Brain sections were evaluated histopathologically. Human glioblastoma specimens were stained for annexin A2, VEGF, and platelet-derived growth factor (PDGF). RESULTS: QRT-PCR and immunohistochemical staining of cultured cells revealed that expression of VEGF was upregulated in accordance with the expression of annexin A2 in J3T-1 and J3T-2A cells. J3T-1 tumors showed remarkable angiogenic activity and invasion around neovasculature, whereas J3T-1shA tumors, including J3T-2 tumors, showed no angiogenic activity, but diffuse single-cell infiltration of tumor cells into normal parenchyma. J3T-2A tumors were highly angiogenic and showed angiogenesis-dependent invasion. Human glioblastoma specimens revealed that annexin A2 was positive in clusters of tumor cells around dilated vessels (25/30 cases). The intensity of VEGF and PDGF staining corresponded to the expression of annexin A2 (correlation coefficients: annexin A2/VEGF: R = 0.73, P < 0.05; annexin A2/PDGF: R = 0.37, P < 0.05). CONCLUSIONS: Our results revealed that the phenotype of glioma invasion is closely related to angiogenesis, and annexin A2 is one of the factors that regulates angiogenesis and invasion phenotype of malignant glioma. SECONDARY CATEGORY: Neuropathology & Tumor Biomarkers.

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