MYCN and neoplasm: MYCN driven tumor formation had higher penetrance and reduced latency in p53 haploinsufficient mice, and chemotherapy induced apoptosis was shown to be p53-dependent, in which apoptosis was significantly reduced in TH-MYCNp53 +/- tumors compared with TH-MYCNp53 + / + tumors (Chesler et al., 2008).