Thus, the number of NK-1 receptors expressed in normal human cells is lower (e.g., human blood T-lymphocytes express 7,000–10,000 NK-1 receptors/cell) [56] than that expressed in human tumor cells (e.g., astrocytoma cells express 40,000 NK-1 receptors/cell) [57]. This evidence concerns the gene TACR1 and neoplasm.