TP53 and neoplasm: This in vitro transformation model is particularly powerful for identifying and studying putative tumor suppressor genes in the TP53 pathway (Drost et al., 2010; Voorhoeve et al., 2006), especially compared to cancer-derived cell lines or spontaneously immortalized cells such as MCF10A cells in which the tumor suppressive network has been inactivated in a variety of ways (Kadota et al., 2010).