The C1q/TNF-related peptide 8 (CTRP8) has recently emerged as a novel ligand of the G protein-coupled receptor RXFP1 in the fatal brain tumor glioblastoma (GBM).
This establishes a role for dopamine receptor signaling via G protein βγ subunits in glioblastoma invasion and shows that phosphoinositide 3-kinase mutations in glioblastoma require a context of basal G protein-coupled receptor activity in order to promote this invasion.
Collectively, these findings implicate a Rap1A/β1 integrin pathway, activated downstream of G-protein-coupled receptor stimulation and RhoA, in glioblastoma cell proliferation.
Therefore, we investigated the transcription of the chemokine-receptor combinations CXCL12-CXCR4-CXCR7, CXCL16-CXCR6 and CX3CL1-CX3CR1 in freshly isolated TAMs from 20 human glioblastomas in relation to in vitro polarized M1- and M2-macrophages.
In contrast, the receptor CXCR6 is restricted in glioblastomas to a small subset of proliferating cells positive for the stem-cell markers Musashi, Nanog, Sox2 and Oct4.
Epidermal growth factor module-containing mucin-like receptor 2 is a newly identified adhesion G protein-coupled receptor associated with poor overall survival and an invasive phenotype in glioblastoma.
Activation of the formylpeptide receptor (FPR), a G-protein-coupled receptor, by its chemotactic peptide ligand N-formylmethionyl-leucyl-phenylalanine (fMLF) promotes the directional migration and survival of human glioblastoma cells. fMLF also stimulates glioblastoma cells to produce biologically active VEGF, an important angiogenic factor involved in tumor progression.