IL-8/CXCR1/2 signalling promotes tumor cell proliferation, invasion and vascular mimicry in glioblastoma

Background: Glioblastoma multiforme (GBM) is one of the lethal malignant tumors of the central nervous system. Despite advances made in understanding this complex disease, little has been achieved in improving clinical efficacy towards it. Factors such as chemokines play important role in shaping the tumor microenvironment which in turn plays a significant role in deciding course of tumor progression. In this study, we investigated the role of chemokine IL-8 in glioblastoma progression with particular emphasis on immunomodulation, cellular proliferation, invasion and vascular mimicry. Methods: Role of IL-8 in GBM immunology was determined by correlating the expression of IL-8 by immunohistochemistry with other immune cell markers such as CD3 and CD68. Effect of high IL-8 expression on overall survival, the difference in expression level between different GBM subgroups and anatomic structures were analyzed using other databases. Two GBM cell lines - U-87MG and LN-18 were used to study the impact of targeting IL-8-CXCR1/2 signalling using neutralizing antibodies and pharmacological antagonist. Reverse transcriptase-polymerase chain reaction and immunocytochemistry were used to determine the expression of these axes. Impact on cell viability and proliferation was assessed by MTT, proliferation marker-ki-67 and clonogenic survival assays. Multicellular tumor spheroids generated from GBM cell lines were used to study invasion in matrigel. Results: Weak Positive correlation was observed between IL-8 and CD3 as well as between IL-8 and CD68. High IL-8 expression in GBM patients was found to be associated with dismal survival. No significant difference in IL-8 expression between different molecular subgroups of GBM was observed. In vitro targeting of IL-8-CXCR1/2 signalling displayed a significant reduction in cell viability and proliferation, and spheroid invasion. Furthermore, the presence of CD34-/CXCR1 + vessels in GBM tissues showed the involvement of IL-8/CXCR1 in vascular mimicry structure formation. Conclusion: These results suggest a direct involvement of IL-8-CXCR1/2 axes in GBM progression by promoting both cell proliferation and invasion and indirectly by promoting neovascularization in the form of vascular mimicry.