Specifically, ATP-gated P2X3 and P2X2/3 receptors selectively expressed in primary afferent nerves (vagal C fibers and Aδ-fibers) and afferent sensory neurons (i.e. dorsal root ganglia, trigeminal nerve, inferior ganglion of the vagus nerve, and glossopharyngeal nerve) (53, 54) participate in the development and transmission of pain signals with respect to chronic inflammatory pain, neuropathic pain, and cancer pain (55, 56). The gene discussed is P2RX2; the disease is cancer.