CCNE1 and cancer: Given that i) cancer cells harbouring CCNE1 gene amplification depend on CCNE1 expression for their survival, ii) that one of the main functions of CCNE1 is to activate CDK2 in the transition from G1/S phase [55], and iii) that CCNE1 RNAi-mediated silencing led to G1 arrest, we posited that cancer cells harbouring CCNE1 gene amplification would be dependent on CDK2 expression and kinase activity for their survival.