CCNE1 and neoplasm: For example, although its mutation is a major cause of familial PD,88,89 Parkin can function as a tumor suppressor to downregulate some substrates, such as cyclin D and cyclin E, and subsequently control cell cycle progression.90 Additionally, Parkin can promote the degradation of TRAF2 and TRAF6, thereby inhibiting the nuclear factor-kappa-B (NF-κB) signaling pathway and inducing tumor apoptosis.91