Neuregulin 4 also known as NRG4 is a member of the neuregulin protein family which in humans is encoded by the NRG4 gene. Loss of expression of NRG4 is frequently seen in advanced bladder cancer while increased NRG4 expression correlates to better survival. The neuregulins, including NRG4, activate type-1 growth factor receptors (EGFR) to initiating cell-to-cell signaling through tyrosine phosphorylation. Furthermore, NRG4 is a low affinity ligand for the ERBB4 tyrosine kinase receptor. Concomitantly recruits ERBB1 and ERBB2 coreceptors, resulting in ligand-stimulated tyrosine phosphorylation and activation of the ERBB receptors. NRG4 does not bind to the ERBB1, ERBB2 and ERBB3 receptors.