NRGs belong to the large family of EGF ligands, and are implicated in brain development activities by interacting with ErbB [31] and regulating HER2, HER3, and HER4 (ERBB2, ERBB3 and ERBB4, respectively, in mice), all of which have been linked to different types of cancers in the literature [32]. This evidence concerns the gene EGFR and cancer.