In comparison to full-length cyclin E (50 kDa), LMW-E forms are uniquely expressed in tumor cells, exhibit enhanced CDK2-associated kinase activity, have increased affinity for CDK2 [7]–[9], and exhibit decreased inhibition by CDK2 inhibitors, p21 and p27 (Figure 1) [10], [11]. The gene discussed is CCNE1; the disease is neoplasm.