On the other hand, tumors with N-MYC overexpression are composed predominantly of highly proliferative neuronal progenitor cells, which suggests that N-MYC promotes proliferation and prevents differentiation of these progenitor cells, resulting in tumor formation in sympathetic nervous system, as demonstrated in tyrosine hydroxylase (TH)-MYCN transgenic mice (N-MYC regulated by TH promoter) [150]. Here, MYCN is linked to neoplasm.