Studies have elucidated PGE2-induced neurite elongation through EP2 or EP4 activation using neuronal cell lines, such as human neuroblastoma SK-N-BE(2) C cells, mouse neuroblastoma NG108–15 cells, somatosensory neuron-like ND7/23 cells, and motor neuron-like NSC-34 cells [210–213]. The gene discussed is PTGER4; the disease is neuroblastoma.