Abstract
The role of macrophages in the growth and the progression of tumors has been extensively studied in recent years. A large body of data demonstrates that macrophage polarization plays an essential role in the growth and progression of brain tumors, such as gliomas, meningiomas, and medulloblastomas. The brain neoplasm cells have the ability to influence the polarization state of the tumor associated macrophages. In turn, innate immunity cells have a decisive role through regulation of the acquired immune response, but also through humoral cross-talking with cancer cells in the tumor microenvironment. Neoangiogenesis, which is an essential element in glial tumor progression, is even regulated by the tumor associated macrophages, whose activity is linked to other factors, such as hypoxia. In addition, macrophages play a decisive role in establishing the entry into the bloodstream of cancer cells. As is well known, the latter phenomenon is also present in brain tumors, even if they only rarely metastasize. Looking ahead in the future, we can imagine that characterizing the relationships between tumor and tumor associated macrophage, as well as the study of circulating tumor cells, could give us useful tools in prognostic evaluation and therapy. More generally, the study of innate immunity in brain tumors can boost the development of new forms of immunotherapy.
Highlights
The central Nervous System (CNS) was classically considered an “immune-privileged site”, being immunologically inert and separated from the peripheral immune system [1,2].The Blood-Brain Barrier (BBB) maintains the optimal microenvironment in the CNS and is a major cause of this immune-privilege [3].Brain endothelial cells lack the expression of leUKocyte adhesion molecules [4]
Our results suggest that macrophages in Chordoid meningioma (CM) are mainly in a non-polarized or M2 state and their abundance might be associated with a major potential of relapse; there is an inverse correlation between the number of mast cells and macrophages [77]
It is well known that gliomas, meningiomas, and medulloblastomas metastasize very rarely in extracranial organs [129,130,131], but medulloblastoma disseminates frequently via the cerebrospinal fluid
Summary
The central Nervous System (CNS) was classically considered an “immune-privileged site”, being immunologically inert and separated from the peripheral immune system [1,2]. The Blood-Brain Barrier (BBB) maintains the optimal microenvironment in the CNS and is a major cause of this immune-privilege [3]. Brain tumors represent a particular case in which BBB is disrupted to different degrees, and acquired and innate immunity may play a role in the development and growth of neoplasia [6]. In the last few years much evidence has been accumulated regarding the relationship between innate immunity and tumors of the central nervous system, mainly in gliomas. Chordoid plexux papilloma Atypical choroid plexus papilloma Choroid plexus carcinoma Dysembryoplastic neuroepithelial tumor Gangliocytoma Ganglioglioma Anaplastic ganglioglioma Dystplastic gangliocytoma of cerebellum (Lhermitte-Duclos) Desmoplastic infantile astrocytoma and ganglioglioma Papillary glioneuronal tumor Rosette-forming glioneuronal tumor Central neurocytoma
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