HTR5A and glioblastoma: Recently, it was proven that neurons are connected to GBM cells via synapses that, when excited by the upstream neuron, enormously stimulate tumor growth, aggressiveness and migration in GBM cells [64,65], where glutamate, dopamine and 5-HT are the main mediators of these stimuli via their post-synaptic receptors [66,67,68].