Evidence that cyclin D1 is required for tumorigenesis includes the finding that inactivation of cyclin D1 by anti-sense[29] or gene deletion[30] reduced breast tumor and gastrointestinal tumor growth[31] in vivo. Cyclin D1 overexpression is sufficient for the induction of mammary tumorigenesis,[32] attributed to the induction of cell proliferation, increased cell survival,[33] induction of chromosomal instability,[34][35] restraint of autophagy[36][37] and potentially non-canonical functions.[38]