USF1 and neoplasm: The findings that insulin via DNA-PK can contribute to enhanced FAS expression would argue against a tumor suppressive role of USF1; however, in contrast to normal tissue where FAS is mainly regulated by diet, in cancer cells FAS seems to be regulated also through the MAPK and the PI3K pathways with additional intracellular players (Van de Sande et al., 2002; Yang et al., 2002).