Ultrastructural Characterization of Macrophage-like Mononuclear Leukocytes in Human Astrocytic Tumors

Abstract

The aim of this study was to describe the ultrastructural features of macrophage-like mononuclear leukocytes associated with human astrocytic tumors. Tumoral biopsies of 10 patients with a pathological diagnosis of astrocytic tumor by means of transmission electron microscopy were examined. The macrophage-like mononuclear leukocyte shows ultrastructural characteristics related with the physiologic phenotype of the alternatively activated macrophage (M2), localized principally around of tumoral vasculature and tumor milieu; classically activated macrophages (M1) in surrounding necrosis areas were observed. The presence of these two ultrastructural kinds of macrophage-like mononuclear leukocytes into different areas of the tumor denotes that cellular response of TAMs is dependent of microenvironment stimuli in different parts of a tumor. The process of transvascular emigration of monocyte/macrophage-like mononuclear leukocytes into tumor is presented. The preponderance of alternatively activated macrophage-like mononuclear leukocytes suggests disequilibrium between pro-tumoral leukocytes and anti-tumoral leukocytes. Therefore, macrophage polarization toward anti-tumoral macrophage-like mononuclear leukocytes would be a potential target for therapeutic manipulation in human astrocytic tumors.

Emerging Role of Tumor-associated Macrophages as Therapeutic Targets in Glioblastoma Multiforme

“…The contemporary anti-tumor strategies are shifting from tumor-cell centric to those targeting various components of the tumor microenvironment [18][19]. The tumor microenvironment is a mixture of extracellular matrix molecules, tumor cells, endothelial cells, fibroblasts, and immune cells [20][21]. Among the tumor-infiltrating leukocytes, the predominant infiltrating cells comprise macrophages/microglia, which are referred to as tumor-associated macrophages (TAMs).…”