BUB1 and neoplasm: Indeed, haploinsufficiency for most of the genes involved in the maintenance of chromosome stability (e.g. Cenpe, Mad1, Mad2, Plk4, Bub1) leads to long tumour latency and low penetrance, despite the high percentage of aneuploid cells73–78, suggesting that there are factors (e.g. p53) that restrain the transforming potential of aneuploidy78,79.