CDKN2A and neoplasm: Although induction of PyMT does not lead to tumorigenesis in β cells, even in Ink4a/Arf-null and Arf-null backgrounds, β cells are subject to transformation by other oncogenes, such as SV40 T antigen (Tag) and Myc; in addition, the viability of either the hyperplastic or tumor cells is dependent on the continued expression of the initiating oncogene [24]–[26].