E2F1 and prostate cancer: This peptide, when conjugated with penetratin (PEP), elicited cellular uptake and has been demonstrated to bind to the E2F1 promoter to abrogate its transcription and downregulated E2F-responsive enzymes, leading to notable cytotoxicities in cell lines of lung cancer and prostate cancer (Xie et al., 2013; Xie et al., 2014).