Nicotinic Acetylcholine Receptor of α7 Subtype is Linked to Glioblastoma Cholinergic Heterogeneity

Glioblastoma multiforme (GBM) shows tremendous heterogeneity in terms of morphology and gene expression. One of the diagnostically significant characteristics of GBM is the choline peak that can be found in patients’ NMR. Choline derivatives are distributed unevenly throughout the tumor and concentrated, in particular, at the leading edge and infiltrating GBM tumour zones as well as gene transcripts of α7 nicotinic acetylcholine receptor (nAChR), known for its ability to become activated upon choline binding. Since agonist-induced nAChR up-regulation in brain and cell lines has been described and several studies have highlighted the role of nAChR ligands in glioblastoma proliferation in vivo, here we hypothesize for the first time that the complex architecture of glioblastoma might develop partially through choline activation of calcium-permeable α7 nAChR that may contribute to changes in gene expression networks. Using the U87MG glioblastoma cell line, we demonstrated that selective α7 nAChR ligands – agonist (PNU282987) and positive allosteric modulator (PNU120596), and antagonist of α7 and α9 nAChRs (α-cobratoxin, α-CTX, from Naja naja venom) – dynamically regulate nAChR subunit mRNA expression (CHRNA4, CHRNA5, CHRNA6, CHRNA7, CHRNA9). α-CTX suppressed agonist-induced CHRNA7 up-regulation in U87MG cells and increased cell viability. Proteomic analysis revealed altered expression of cytoskeletal (ACTG1), metabolic (SHMT2, GLRX3), and endoplasmic reticulum-associated (GANAB) proteins, suggesting the involvement of calcium-dependent signaling downstream of α7 nAChR activation. Quantitative PCR, proteomics and cell viability data were integrated by cellular automata model imitating glioblastoma growth and exposed details of tumour progression, which supports a role for α7 nAChR as one of multiple factors that can help shape intratumoural heterogeneity. These results may have implications for the development of personalized treatment strategies. However, since these findings were obtained in a single cell line, further validation in additional GBM models and in vivo systems is needed before broader conclusions can be drawn.