CDT1 and Geminin are central regulators of licensing, while their aberrant protein expression has been reported in various cancer-derived cell lines, as well as in different human tumor specimens (Karakaidos et al., 2004; Xouri et al., 2004; Bravou et al., 2005; Gonzalez et al., 2005; Tatsumi et al., 2006). This evidence concerns the gene CDT1 and cancer.