Grade IV astrocytomas, or
glioblastomas (GBMs), are the most common malignant
primary brain tumor in adults. The median GBM patient survival of 12-15 months has remained stagnant, in spite of treatment strategies, making GBMs a tremendous challenge clinically. This is at least in part due to the complex interaction of GBM cells with the brain microenvironment and their tendency to aggressively infiltrate normal brain tissue. GBMs frequently invade supratentorial brain regions that are richly innervated by
neurotransmitter projections, most notably
acetylcholine (ACh). Here, we asked whether ACh signaling influences the biology of GBMs. We examined the expression and function of known
ACh receptors (AChRs) in large GBM datasets, as well as, human GBM cell lines and patient-derived xenograft lines. Using
RNA-Seq data from the "The
Cancer Genome Atlas" (TCGA), we confirmed the expression of AChRs and demonstrated the functionality of these receptors in GBM cells with time-lapse
calcium imaging. AChR activation did not alter cell proliferation or migration, however, it significantly increased cell invasion through complex extracellular matrices. This was due to the enhanced activity of
matrix metalloproteinase-9 (MMP-9) from GBM cells, which we found to be dependent on an intracellular
calcium-dependent mechanism. Consistent with these findings, AChRs were significantly upregulated in regions of GBM infiltration in situ (Ivy
Glioblastoma Atlas Project) and elevated expression of
muscarinic AChR M3 correlated with reduced patient survival (TCGA). Data from the Repository for Molecular Brain
Neoplasia Data (REMBRANDT) dataset also showed the co-expression of
choline transporters,
choline acetyltransferase, and
vesicular acetylcholine transporters, suggesting that GBMs express all the
proteins required for ACh synthesis and release. These findings identify ACh as a modulator of GBM behavior and posit that GBMs may utilize ACh as an autocrine signaling molecule.