MONOCYTE CHEMOATTRACTANT PROTEIN-1 EXPRESSION AND MACROPHAGE INFILTRATION IN GLIOMAS

While the number of reports on macrophage infiltration of gliomas is i ncreasing, the extent and mechanisms of macrophage recruitment remain unclear. To investigate whether monocyte chemoattractant protein-1 (MC P-1) plays a role in this process, in situ hybridisation (ISH) was per formed for 22 glioblastomas (GEM), 1 anaplastic astrocytoma (AA) and 4 grade II fibrillary astrocytomas (Ail) and reverse transcription-poly merase chain reaction was performed in 13 GBM, 1 AA and 3 APT. High le vels of MCP-1 mRNA were detectable in most GBM, while a lower level wa s detected in AII. Many tumour-associated macrophages (TAM) could be d emonstrated by immunohistochemistry (IHC) in most GEM, while the AII c ontained a lower number of TAM. The positive correlation between the M CP-I level and abundance of TAM suggested that MCP-I has a role in TAM recruitment. By combining ISH and IHC, high levels of MCP-1 mRNA were shown both in tumour cells and TAM. Along tumour borders, reactive as trocytes and microglia also expressed MCP-1. In areas with T lymphocyt e infiltration, larger numbers of MCP-l-positive cells with an enhance d level of expression could be identified. We propose that the mechani sm of macrophage recruitment is, at least partly, effected by constitu tive expression and T cell-mediated up-regulation of MCP-1 in tumour c ells and TAM. The production of MCP-1 by TAM establishes a positive am plification circuit for macrophage recruitment in gliomas.