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A human glioblastoma multiforme cell line (U87) and its derived-spheroids were irradiated either using a conventional irradiation (CIR) or a CK-like irradiation (IIR) in which the 8Gy was delivered intermittently over a period of 40 minutes. The ability of glioma cells to migrate into a matrigel matrix was evaluated on days 1-8 from irradiation. Irradiation with CK-driven IIR significantly increased the invasion potential of U87 cells in a matrigel-based assay. In contrast to CIR, IIR was associated with increased levels of TGF-B at four days (Real time PCR), β1-integrin at 4-5 days (real-time PCR and western blot) and no elevation in phosphorylated AKT at days 4 and 5 (western blot). Our data suggests that glioma cell invasion as well as elevations of TGF-B and β1-integrin are associated with IIR and not CIR.

Gliomas are very invasive brain tumors with poor prognosis and therefore any attempt to limit tumor cell dissemination in the brain is expected to improve glioma treatment. The recent deorphanization of CXCR7 as additional receptor for CXCL12 and CXCL11 has raised key issues on its interaction with the CXCL12/CXCR4 axis as a mechanism to modulate glioma cell migration. In this work we investigated protein and mRNA expression of the two chemokines CXCL12 and CXCL11, together with their receptors CXCR4 and CXCR7 in human glioma specimens and cell lines by immunohistochemistry, flow cytometry and quantitative real-time PCR. The main purpose of this study was to find out whether and at what extent CXCR4 and CXCR7 are differentially expressed in glioma cells. In human glioma specimens the levels of CXCL11 and CXCR4 mRNA were significantly higher in glioblastomas compared to non-tumor controls or low grade gliomas, whilst no difference was found for CXCL12 and CXCR7 mRNA expression. In cell lines, flow cytometry and immunocytochemical experiments showed CXCR4 was mainly expressed irrespective of its membrane or intracellular localization. In contrast, a predominant intracellular localization together with a negligible membrane expression of CXCR7 was found in all cells examined. In in vitro experiments CXCR4 and CXCR7 antagonists and the silencing of CXCR4 showed complete inhibition of glioma proliferation.Our findings, in agreement with previous data, suggest that in human glioma cells the prevalent intracellular localization of CXCR7 might modulate the functionality of CXCL11/12 either acting as a scavenger for these chemokines or interfering with the signaling pathways activated by the stimulation of CXCR4.

Brain metastases occur in about 25% of patients who die of cancer. The most common sources of brain metastases in adults are lung, breast, kidney, colorectal cancer and melanoma. The chemokine/receptor system CXCL12/CXCR4 plays a key role in multiple biological functions; among these, homing of neoplastic cells from the primary site to the target and metastasis progression. Recently, an alternative CXCL12 receptor, CXCR7, has been discovered. The aim of our study was to investigate the expression of CXCL12 and its receptors CXCR4 and CXCR7 by immunohistochemistry in 56 patients with metastatic brain disease from different non-CNS primary tumors and evaluate their prognostic relevance as well as that of other patient/treatment-related features on patient survival. CXCL12 showed an expression in tumor cells and in tumor vessels; CXCR7 was expressed by tumor and endothelial cells (both within the tumor and in the adjacent brain tissue), while CXCR4 showed a positivity in all samples with a nuclear pattern. Among the investigated immunohistochemical parameters, only CXCL12 expression in tumor endothelial cells showed a statistically significant correlation with shorter survival (p=0.04 log-rank), perhaps identifying more aggressive tumors. Thus, this is the first study evaluating at the same time the expression of CXCL12 and its two receptors in a cohort of brain metastases.