Pro-inflammatory cytokines in cystic glioblastoma: A quantitative study with a comparison with bacterial brain abscesses. With an MRI investigation of displacement and destruction of the brain tissue surrounding a glioblastoma

Abstract

Cystic glioblastomas are aggressive primary brain tumors that may both destroy and displace the surrounding brain tissue as they grow. The mechanisms underlying these tumors' destructive effect could include exposure of brain tissue to tumor-derived cytokines, but quantitative cytokine data are lacking. Here, we provide quantitative data on leukocyte markers and cytokines in the cyst fluid from 21 cystic glioblastomas, which we compare to values in 13 brain abscess pus samples. The concentration of macrophage/microglia markers sCD163 and MCP-1 was higher in glioblastoma cyst fluid than in brain abscess pus; lymphocyte marker sCD25 was similar in cyst fluid and pus, whereas neutrophil marker myeloperoxidase was higher in pus. Median cytokine levels in glioblastoma cyst fluid were high (pg/mL): TNF-α: 32, IL-6: 1064, IL-8: 23585, tissue factor: 28, the chemokine CXCL1: 639. These values were not significantly different from values in pus, pointing to a highly pro-inflammatory glioblastoma environment. In contrast, levels of IFN-γ, IL-1β, IL-2, IL-4, IL-10, IL-12, and IL-13 were higher in pus than in glioblastoma cyst fluid. Based on the quantitative data, we show for the first time that the concentrations of cytokines in glioblastoma cyst fluid correlate with blood leukocyte levels, suggesting an important interaction between glioblastomas and the circulation. Preoperative MRI of the cystic glioblastomas confirmed both destruction and displacement of brain tissue, but none of the cytokine levels correlated with degree of brain tissue displacement or peri-tumoral edema, as could be assessed by MRI. We conclude that cystic glioblastomas are highly pro-inflammatory environments that interact with the circulation and that they both displace and destroy brain tissue. These observations point to the need for neuroprotective strategies in glioblastoma therapy, which could include an anti-inflammatory approach.

Keywords: brain abscess; cyst fluid; cytokine; glioblastoma; inflammation; macrophage; pus; tumor microenvironment.

Figure 1

Cystic glioblastoma. Note how the cyst is in close contact with tumor tissue (white asterisk) and the surrounding brain tissue, both white matter and overlying neocortex. Red asterisks indicate the zone of peri-tumoral edema.

Figure 2

Solid glioblastoma in the left occipital lobe. Note how the tumor affects white matter (compare with contralateral side) and produces a mass effect with obliteration of the subarachnoidal spaces of the ipsilateral sulci (arrows). Centrally, this tumor has an area of necrosis (asterisk), which is not cystic.

Figure 3

Neuropathological analysis of cystic glioblastoma. (A) Hematoxylin and eosin staining of a representative biopsy reveals intratumoral cysts. (B) Glioblastoma cells show strong immunoreactivity (brown color) for GFAP. (C) Anti-CD68 antibodies label macrophages and microglia cells (dark brown cells). The areas of the section without solid tissue represent cyst lumen. (D) Anti-CD3 antibodies label T-lymphocytes (dark brown cells). The areas of the section without solid tissue represent cyst lumen. (E) Anti-CD20 antibodies label immunoreactive B-lymphocytes (dark brown cells). The areas of the section without solid tissue represent cyst lumen. (F) The infiltrative growth pattern of the glioblastoma cells in white matter is evident among the axons that are stained dark brown for neurofilament heavy chain. (G) Glioblastoma cells infiltrate neocortical tissue where neurons are stained dark brown for NeuN. (H) Hematoxylin and eosin staining of neocortex shows damaged neurons (white arrowheads) with shrunken, triangular appearance and condensed chromatin. Prominent satellitosis (56) can be seen (black arrow). Please note the proximity of tumor-associated leukocytes to the cyst lumen (C–E). Note also how macrophages and lymphocytes may both be scattered throughout the tumor and appear in groups (C–E) and how neurons (brown nuclei) embedded among tumor cells (blue nuclei) appear pycnotic in the center of (G).

Figure 4

Four cystic glioblastomas before and after tumor surgery. T1 weighted MPRAGE MRIs after intravenous injection of gadolinium-based contrast medium (which gives the ring-formed bright signal in most images), except in D and G, which are T2-weighted and T2-weighted FLAIR, respectively. Images (A, C, E, G) show pre-surgical MRIs. Note the modest displacement of surrounding brain tissue (compare with contralateral side). Images (B, D, F, H, I) show MRIs after 240, 295, 330, 39 days, and 45 months, respectively. Tumors in images (A, C) were assessed as having minimal mass effect, tumors in images (E, G) had pronounced mass effect. Note the absence of brain tissue where the tumor and cyst resided; this comprises white matter and adjacent neocortex.

Figure 5

Four solid glioblastomas before and after tumor surgery. T1-weighted MPRAGE MRIs were obtained after intravenous injection of gadolinium-based contrast medium (which gives a bright, ring-formed signal in most images). Images (A, C, E, G) show pre-surgical MRIs. Tumors in images (A, C) were assessed as having minimal mass effect. Note the modest displacement of surrounding brain tissue (compare with contralateral side). Tumors in images (E, G) were assessed as having moderate and pronounced mass effect, respectively. Images (B, D, F, H) show MRIs after 400, 167, 26, and 4 days, respectively. Note the absence of brain tissue where the tumor resided. This includes both white matter and the overlying neocortex.