ISG15 and neoplasm: Finally, there is suggestive evidence that ISG15 canfunction as a tumor suppressor [30].Premalignant cells have to undergo many divisions before they become invasive,and it is thought that the primary function of replicative aging is to limitthe number of available divisions as a brake against cancer formation [63].Furthermore, hyperproliferation provides one of the conditions favoring thedevelopment of malignancies.