CCNE1 and cancer: Importantly, cyclin E is overproduced in many cancers and tumor-derived cell lines due to gene amplification or dysregulated transcription (Barretina et al, 2012; Asghar et al, 2017; Geng et al, 2018; Chu et al, 2021), yet high cyclin E can induce replication stress, proliferation failure, and genome instability (Minella et al, 2002; Teixeira et al, 2015).