Advances in Chemokine Signaling Pathways as Therapeutic Targets in Glioblastoma

SIMPLE SUMMARY: Chemokine signaling is crucial for tumorigenesis, proliferation, angiogenesis, tumor progression and metastasis in glioblastoma. Furthermore, chemokines have an impact on the overall survival of GBM patients that, with a median survival of 15 months, still lack effective treatment. Several chemokine signaling axes, for instance CXCR2/CXCL2/IL-8, CXCR4/CXCL12 and CCR2/CCL2, were investigated in detail and appear to be promising therapeutic targets. The aim was to review novel approaches that target chemokines or chemokine receptors in glioblastoma. Here, preclinical and clinical studies were used to clarify their significance for targeted treatments alone and in combination with other therapeutic applications. ABSTRACT: With a median patient survival of 15 months, glioblastoma (GBM) is still one of the deadliest malign tumors. Despite immense efforts, therapeutic regimens fail to prolong GBM patient overall survival due to various resistance mechanisms. Chemokine signaling as part of the tumor microenvironment plays a key role in gliomagenesis, proliferation, neovascularization, metastasis and tumor progression. In this review, we aimed to investigate novel therapeutic approaches targeting various chemokine axes, including CXCR2/CXCL2/IL-8, CXCR3/CXCL4/CXCL9/CXCL10, CXCR4/CXCR7/CXCL12, CXCR6/CXCL16, CCR2/CCL2, CCR5/CCL5 and CX3CR1/CX3CL1 in preclinical and clinical studies of GBM. We reviewed targeted therapies as single therapies, in combination with the standard of care, with antiangiogenic treatment as well as immunotherapy. We found that there are many antagonist-, antibody-, cell- and vaccine-based therapeutic approaches in preclinical and clinical studies. Furthermore, targeted therapies exerted their highest efficacy in combination with other established therapeutic applications. The novel chemokine-targeting therapies have mainly been examined in preclinical models. However, clinical applications are auspicious. Thus, it is crucial to broadly investigate the recently developed preclinical approaches. Promising preclinical applications should then be investigated in clinical studies to create new therapeutic regimens and to overcome therapy resistance to GBM treatment.