Unlike D1-receptor-expressing neurons, we found that repeated inhibition of D2-receptor-expressing neurons in the shell and core regions of the nucleus accumbens, which could parallel the state of the stimulation of D2-receptors by released dopamine in D2-receptor-expressing neurons because of essential D2-Gi coupling, failed to decrease tumor volume or change the number of effector T cells compared to those in a control group. This evidence concerns the gene GNAI1 and neoplasm.