The abnormally high expression of FAT10 in the tumors of several cancers, coupled with the observation that high FAT10 levels in cells lead to mitotic non-dysjunction and chromosome instability through the reduction of the MAD2 kinetochore localization during the pro-metaphase stage of the cell-cycle; as well as the findings that its expression is positively regulated by TNF-α, a presumptive tumor promoter [14,23], but negatively regulated by p53, the "guardian-of-the-genome" [24], together, strongly implicate the important role that FAT10 plays in cell-cycle control and tumorigenesis. The gene discussed is UBD; the disease is cancer.