MCP-1 and MIP-3 alpha Secreted from Necrotic Cell-Treated Glioblastoma Cells Promote Migration/Infiltration of Microglia

Background/Aims: Glioblastoma multiforme (GBM) is the most common primary brain tumor in adults. The defining characteristics of GBM are diffuse infiltration of tumor cells into normal brain parenchyma, rapid growth, a high degree of infiltration of microglia and macrophages, and the presence of necrosis. Microglia/macrophages are frequently found in gliomas and they extensively infiltrate GBM tissue, up to 30% of total tumor mass. However, little is known about the effect of necrotic cells (NCs) on microglia infiltration in GBM and the tumor-infiltrating microglia-induced factors in GBMs. Methods: In this study, to address whether necrosis or necrosis-exposed GBM cells affect the degree of microglia/macrophage infiltration, migration and invasion/infiltration assays were performed. Culture supernatants and nuclear extracts of CRT-MG cells treated or untreated with necrotic cells were analyzed using a chemokine array and electrophoretic mobility shift assay, respectively. Results: The presence of NCs promoted the migration/infiltration of microglia, and GBM cell line CRT-MG cells exposed to NCs further enhanced the migration and infiltration of HM06 microglial cells. Treatment with NCs induced mRNA and protein expression of chemokines such as Monocyte Chemoattractant Protein-1 (CCL2/MCP-1) and Macrophage Inflammatory Protein-3 alpha (CCL20/MIP-3 alpha) in CRT MG cells. In particular, CCL2/MCP-1 and CCL20/MIP-3 alpha were significantly increased in NC-treated CRT-MG cells. NCs induced DNA binding of the transcription factors Nuclear Factor (NF)-kappa B and Activator Protein 1 (AP-1) to the CCL2/MCP-1 and CCL20/MIP-3 alpha promoters, leading to increased CCL2/MCP-1 and CCL20/MIP-3 alpha mRNA and protein expression in CRT MG cells. Conclusion: These results provide evidence that NCs induce the expression of CCL2/MCP-1 and CCL20/MIP-3 alpha in glioblastoma cells through activation of NF-kappa B and AP-1 and facilitate the infiltration of microglia into tumor tissues. (C) 2018 The Author(s) Published by S Karger AG, Basel