TYMS and neoplasm: Evidence that TYMS can directly participate in tumorigenesis was demonstrated by (i) transformation of mammalian cells in vitro following ectopic expression of human TYMS resulting in tumor formation in vivo in nude mice [8, 9] and (ii) induction of pancreatic islet cell adenoma following expression of ectopic TYMS (previously designated hTS) in transgenic mice [10].