Background The CXCL12/CXCR4 pathway regulates tumor cell proliferation, metastasis, angiogenesis and the tumor-microenvironment cross-talk in several solid tumors, including glioblastoma (GBM), the most common and fatal brain cancer. given for 23?days since cell implantation and tumor volume was assessed by magnetic resonance imaging (MRI) at 4.7?T. Glioma connected microglia/macrophage (GAMs) polarization (anti-tumor M1 versus pro-tumor M2 phenotypes) and expressions of vascular endothelial growth element (VEGF) and CD31 were assessed by immunohistochemistry and immunofluorescence. Results We found that peptide R impairs the metabolic activity and cell proliferation of human being U87MG cells and stably reduces CXCR4 manifestation and cell migration in response to CXCL12 in vitro. In the orthotopic U87MG model, peptide R reduced tumor cellularity, advertised M1 features of GAMs and astrogliosis, and hindered intra-tumor vasculature. Conclusions Our findings suggest that focusing on CXCR4 by peptide R might represent a novel restorative approach against GBM, and contribute to the rationale to further explore in more complex pre-clinical settings the restorative potential of peptide R, only or in combination with standard therapies of GBM. Electronic supplementary material The online version of this article (doi:10.1186/s13046-016-0326-y) contains supplementary material, which is available to authorized users. displayed in the number). peptide R-treated cells), peptide-treated U87MG) (72?h of treatments), unpaired two-tailed College student t-test. b MTT assay performed on U87MG cells after 72?h incubation with CXCL12, in the presence of peptide R or Plerixafor, compared to untreated cells (-CXCL12) (means??SD of represented in the number), one-way ANOVA. Plerixafor-treated U87MG), peptide R-exposed cells), peptide R-treated U87MG cells), unpaired two-tailed College student t-test. c Quantitative analysis of U87MG cells migration (for details see Methods section) in response to 10?% FBS (black pub) or in response to CXCL12 ITX3 in the absence or presence of peptide R or Plerixafor. The percentages of area occupied by migrating ITX3 cells are reported as mean ideals??SD (shown in the number) one-way ANOVA. represent the migration innovator elements. Scale bars are ITX3 indicated Evaluation of Annexin V-positive or PI-bright cells at the same time points showed that neither peptide R nor Plerixafor exerted any appreciable apoptotic or necrotic effect (data not demonstrated). Next, cell viability was assessed by MTT assay. No significant effects were induced by both treatments at 24 and 48?h (data not shown); however, a significant reduction in the metabolic activity of U87MG cells was observed in both peptide R- and Plerixafor-treated cells (Fig.?2b). Since we previously showed that peptide R inhibits cell motility of melanoma and osteosarcoma cells [35, 36], we tested the effects exerted by peptide R and by Plerixafor, on glioma cells migration. U87MG cells, in serum free medium, were seeded in transwell chambers and allowed to migrate towards chemokine CXCL12 (added to the lower chamber medium) in the lack or existence of peptide R. Furthermore to CXCL12, FBS was also utilized as positive control for migration (dark club in Fig.?2c). Quantitative evaluation by computer-assisted light microscopy (Fig.?2c), showed that, needlessly to say, CXCL12 activated U87MG cell migration, Plerixafor treatment didn’t induce significant adjustments, even though peptide R reduced the percentage of region occupied by migrating cells significantly. Checking electron microscopy (SEM) evaluation of the higher side from the filtration system demonstrated that during migration U87MG cells subjected to FBS or CXCL12 move as stores or band of cells (Fig.?2da,b). The current presence of peptide R hampered cell migration through the membrane skin pores, and U87MG cells made an appearance organized in restricted clusters (Fig.?2dc). On the low side from the filtration system numerous cells had been visible in charge (FBS) or CXCL12-treated cells?(Fig. 2dd,e), within the existence of peptide R hardly any cells crossing membrane skin pores were documented (Fig.?2df). In vivo ramifications of peptide R BCLX in the orthotopic U87MG mouse model The above mentioned in ITX3 vitro outcomes supported the anti-tumor ramifications of peptide R on glioma cells. To check this hypothesis in vivo, we utilized intracranial orthotopic xenografts of U87MG cells. Tumor localization and quantity had been examined by MRI analyses in mice treated with automobile, peptide Plerixafor or R, as reported in Strategies. Volumetric evaluation (Fig.?3a) performed in time 10, 15 and 23 after U87MG cells implantation and remedies did not present any significant transformation of tumor size in pets treated with both CXCR4 antagonists, in comparison to control group (PBS-treated mice, CTRL). Nevertheless, immunohistochemical analyses of mind slices showed a reduction of U87MG cells, as recognized by vimentin manifestation, after treatment with peptide R when compared to Plerixafor or PBS treatment (Fig.?3b), as a result suggesting a reduced tumor cell density in peptide R-treated mice. Interestingly, in the contralateral hemisphere no vimentin+.