NRG1 and cancer: Third, NRG1 is a non-selective agonist of the ERBB system, binding to both ERBB3 and ERBB4 receptors, and thus it may activate ERBB3 receptors in ERBB2-overexpressing tumor cells, thereby enhancing the formation of ERBB3/ERBB2 complexes, which could induce or accelerate cancer growth25,26.